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No. 49: Jan-Feb 1987
The puzzling occultations of stars by Neptune have led scientists to postulate that discontinuous rings of debris rotate around the planet. (SF#38 and #40) But, given the number of recent failures to detect the ring at all, astronomers have been reduced to thinking about even weirder configurations of matter. The most recent model, by P. Goldreich et al, envisions a necklace of arcs in orbit, as illustrated. They calculate that the resonant effects of a yet undiscovered satellite in an inclined orbit could produce this strange pattern.
(Murray, Carl d.; "Arcs around Neptune," Nature, 324:209, 1986.)
Comment. Voyager 2 will encounter Neptune in 1989. Hopefully, it will clear things up ringwise. Or, it may photograph something even more exotic, like some 2001-like monoliths in orbit!!
|A possible configuration for ring and arcs and a confining satellite in orbit around Neptune, according to the theory of Goldreich et al. Radial variations are exagerated. (Would any astronomer, even 10 years ago, have countenanced such a spectacle in the Solar System?)| | 0.813455 | 3.285358 |
On a distant space rock investigated by NASA's probe, the days are slowing down – and scientists are still trying to figure out why. every 4.3 hours. But scientists working on NASA's OSIRIS-REx mission to space rock used data collected before the probe arrived to calculate that Bennu's rotation speed accelerated over time – by about 1 second of every century. As things accelerate, things need to change, so we'll look for these things, and discovering that speed gives us some insights into what kinds of things we need to look for, "Mike Nolan, lead author of the New Study and Geophysicist in the Moon and Planetary a laboratory at the University of Arizona, who is also the head of the OSIRIS-REx mission team, said in a statement published by the American Geophysical Union, which published the new study. "We have to look for evidence that something is different in the relatively recent past and it is possible to change things when we go." Related: OSIRIS-REx: NASA Mission to Return Asteroids to Photos
The new study, despite mission links OSIRIS-REx is not based on measurements from this probe; Instead, he looks at data collected from two terrestrial telescopes between 1
"You can not make all three of them fit completely," said Nolan. "It was when we came up with this idea that it should speed up."
This is not an unknown phenomenon, but it is rare, and scientists have just confirmed their first example of accelerating the rotation of the asteroid in 2007. Bennou observations leave the secret to what causes it.
One possible explanation is that the material that moves on the surface of Bennu or emerges from the asteroid can allow the speed of rotation to accelerate. The other explanation is more complex, the effect Yarkovski-O'Keefe-Radzievski-Paddak (YORP) . This effect is caused by the sunlight rebounding from the asteroid and slightly changing the spin speed faster or slower depending on the shape of the object. For particularly weak asteroids, the effect of YORP can actually break into a rock space .
Scientists behind the new study suspect that the effect of YORP Bennu is experiencing. Over the next two years, OSIRIS-REx will provide more data, including detailed boulder analysis and gravity measurements. Scientists can use these observations to confirm what is happening in Bennu and determine the local YORP levels.
These numbers can also help scientists understand the behavior of other asteroids who will never see a special spacecraft. published January 31 in Geophysical Research Letters. | 0.808345 | 3.875843 |
On the morning of the full Moon on June 17, , as morning twilight begins, the bright planet Jupiter will appear in the southwest at about 8 degrees above the horizon and the planet Saturn will appear in the south-southeast at about 25 degrees above this horizon. The bright star appearing nearly overhead will be Deneb, part of the "Summer Triangle. As the month progresses, Jupiter, Saturn, and the background of stars will appear to shift towards the west. Venus will appear to shift closer to the Sun, rising closer to sunrise and becoming more difficult to see.
Venus will pass on the far side of the Sun as seen from the Earth in mid-August By the morning of the full Moon on July 16, , as morning twilight begins, Jupiter will have already set and Saturn will appear low in the southwest at about 7 degrees above the horizon. This summer should be a great time for Jupiter and Saturn watching, especially with a backyard telescope.
Jupiter was at its closest and brightest for the year on June 10, while Saturn will be at its closest and brightest on July 9, called "opposition" because they are opposite the Earth from the Sun, effectively a "full Jupiter" and a "full Saturn". Both will appear to shift towards the west over the coming months, making them visible earlier in the evening sky and friendlier for backyard stargazing, especially if you have young ones with earlier bed times.
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With clear skies and a small telescope you should be able to see Jupiter's four bright moons, Ganymede, Callisto, Europa, and Io, shifting positions noticeably in the course of an evening. Galileo was the first person known to point the newly developed telescope at Jupiter, and he immediately noticed these moons that we now call the Galilean moons. For Saturn, you should be able to see the brightly illuminated rings as well as the motions of Saturn's moons, particularly the largest moon, Titan.
On Wednesday evening, June 12, , the bright star appearing to the lower right of the waxing gibbous Moon will be Spica. Even though they are not usually visible, I include in these Moon missives information about Near Earth Objects mostly asteroids that pass the Earth within about 10 or 15 lunar distances, because I find it interesting that we have discovered so many. Sometime around Friday, June 14, , Jun UTC with 5 days, 8 hours, 5 minutes uncertainty , Near Earth Object YA14 , between and feet 48 and meters in size, will pass the Earth at between 8.
On Saturday night into Sunday morning, June 15 to 16, , the bright planet Jupiter, the bright star Antares, and the waxing, gibbous, almost full Moon will appear as a triangle, with Jupiter on the left, the Moon on the right and Antares below. For the Washington, DC area, they will appear in the southeast as evening twilight ends at PM EDT, the Moon will reach its highest in the sky just after midnight at AM, and Antares will be setting in the southwest just as morning twilight begins Sunday morning at AM.
On Sunday evening into Monday morning, June 16 to 17, , the bright planet Jupiter will appear to the right of the nearly full Moon. They will appear in the southeast as evening twilight ends at PM EDT for the Washington, DC area , the Moon will reach its highest in the sky early Monday morning at PM , and they will appear in the southwest as morning twilight begins at AM. On Tuesday evening, June 18, , the planets Mercury and Mars will appear less than a third or a degree apart low in the west-northwest.
To see them, you will need a clear view of the horizon and to look as evening twilight ends. For the Washington, DC area, as evening twilight ends at PM EDT, Mercury the brighter of the two will appear about 5 degrees above the horizon, with Mars appearing less than a third of a degree below Mercury.
The two bright stars to the upper right of Mercury and Mars will be Pollux and Castor, the "twins" in the constellation Gemini.
On Wednesday evening into Thursday morning, June 19 to 20, , the bright planet Saturn will appear near the full Moon. As the pair rises, Saturn will appear to shift towards the right. By the time the Moon reaches its highest in the sky Thursday morning at AM, Saturn will appear to the upper right. They will still appear near each other as morning twilight begins at around AM. Friday, June 21, , at AM EDT, will be the summer solstice, the astronomical end of spring and start of summer. This will be the day with the longest period of sunlight 14 hours, 53 minutes, and On Sunday evening, June 23, , at around 7 PM EDT, the planet Mercury will be at its greatest angular separation from the Sun in the evening sky as seen from the Earth, called greatest eastern elongation, appearing half full when viewed by telescope.
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On Sunday morning, June 30, , if you have a clear view of the east-northeast horizon, you might be able to see the bright star Aldebaran appearing about 3 degrees to the lower left of the thin, waning, crescent Moon. On Monday morning, July 1, , if you have a clear view of the east-northeast horizon, you might be able to see Venus and the thin, waning crescent Moon. The sky may be bright enough that you may need binoculars to see them and be sure to STOP looking with binoculars well before sunrise, as concentrating sunlight into your eyes with lenses is a really bad idea.
This will be a total eclipse of the Sun, visible from the southeastern Pacific ocean and from a small part of Chile and Argentina right around sunset. A partial eclipse of the Sun should be visible from parts of South and Central America. By fusing your ego with your sensitivities, the solar eclipse helps you realize that your future choices are all about advocating for your self-worth.
On the other hand, the lunar eclipse on July 16th helps you understand the long-term implications of these critical changes. As the Moon emits this unusual umber tone, it enables you to shift your perspective and process your circumstances through a different lens.
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These eclipses are occurring in Cancer and Capricorn. So, if you have a planet or celestial point in Cancer or Capricorn, it will be directly impacted by these eclipses.
However, because all birth charts are degrees and contain all the zodiac signs, everyone will—to varying degrees—be influenced by these eclipses. The Cancer-Capricorn eclipse series actually started last year, so to find out exactly how these upcoming eclipses will impact you, think back to the earlier occurrences on July 12th, , and January 5th, What was going on in your life? Who was involved? Were you experiencing any changes?
Brace yourself for some serious drama, because eclipses are no joke! Type keyword s to search. A few centuries later, around BC, Aristotle took Pythagoras observations even further. By observing the shadow of the Earth across the face of the Moon during a lunar eclipse, Aristotle reckoned that the Earth was also a sphere. He reasoned, incorrectly however, that the Earth was fixed in space and that the Moon, Sun and Stars revolved around it.
He also believed the Moon was a translucent sphere that traveled in a perfect orbit around Earth. In the early s Astronomer Nicolaus Copernicus developed a model of the Solar System where Earth and the other planets orbited around the Sun, and the Moon orbited around Earth.https://otstersisci.gq
These observations were revolutionary. Copernicus and Galileo upended the long-held Aristotelian view of the heavens as a place where Earth was the center of the Universe and the Moon was a smooth, polished orb. Telescopes and new minds helped scientist understand that the Earth and planets orbited around the Sun and the Moon was a battered and cratered satellite held in our own orbit. | 0.862555 | 3.441262 |
Scientists from Germany and the United States have unveiled the results of a newly-completed, state of the art simulation of the evolution of galaxies. TNG50 is the most detailed large-scale cosmological simulation yet. It allows researchers to study in detail how galaxies form, and how they have evolved since shortly after the Big Bang. For the first time, it reveals that the geometry of the cosmic gas flows around galaxies determines galaxies’ structures, and vice versa. The researchers publish their results in two papers in the journal Monthly Notices of the Royal Astronomical Society.
Astronomers running cosmological simulations face a fundamental trade-off: with finite computing power, typical simulations so far have been either very detailed or have spanned a large volume of virtual space, but have so far not been able to do both. Detailed simulations with limited volumes can model no more than a few galaxies, making statistical deductions difficult. Large-volume simulations, in turn, typically lack the details necessary to reproduce many of the small-scale properties we observe in our own Universe, reducing their predictive power.
The TNG50 simulation, which has just been published, manages to avoid this trade-off. For the first time, it combines the idea of a large-scale cosmological simulation – a Universe in a box – with the computational resolution of “zoom” simulations, at a level of detail that had previously only been possible for studies of individual galaxies.
In a simulated cube of space that is more than 230 million light-years across, TNG50 can discern physical phenomena that occur on scales one million times smaller, tracing the simultaneous evolution of thousands of galaxies over 13.8 billion years of cosmic history. It does so with more than 20 billion particles representing dark (invisible) matter, stars, cosmic gas, magnetic fields, and supermassive black holes. The calculation itself required 16,000 cores on the Hazel Hen supercomputer in Stuttgart, working together, 24/7, for more than a year – the equivalent of fifteen thousand years on a single processor, making it one of the most demanding astrophysical computations to date.
The first scientific results from TNG50 are published by a team led by Dr. Annalisa Pillepich (Max Planck Institute for Astronomy, Heidelberg) and Dr Dylan Nelson (Max Planck Institute for Astrophysics, Garching) and reveal unforeseen physical phenomena. According to Nelson: “Numerical experiments of this kind are particularly successful when you get out more than you put in. In our simulation, we see phenomena that had not been programmed explicitly into the simulation code. These phenomena emerge in a natural fashion, from the complex interplay of the basic physical ingredients of our model universe.”
TNG50 features two prominent examples of this kind of emergent behavior. The first concerns the formation of “disc” galaxies like our own Milky Way. Using the simulation as a time machine to rewind the evolution of cosmic structure, researchers have seen how the well-ordered, rapidly rotating disc galaxies (which are common in our nearby Universe) emerge from chaotic, disorganized, and highly turbulent clouds of gas at earlier epochs.
As the gas settles down, newborn stars are typically found on more and more circular orbits, eventually forming large spiral galaxies – galactic carousels. Annalisa Pillepich explains: “In practice, TNG50 shows that our own Milky Way galaxy with its thin disc is at the height of galaxy fashion: over the past 10 billion years, at least those galaxies that are still forming new stars have become more and more disc-like, and their chaotic internal motions have decreased considerably. The Universe was much messier when it was just a few billion years old!”
As these galaxies flatten out, researchers found another emergent phenomenon, involving the high-speed outflows and winds of gas flowing out of galaxies. This launched as a result of the explosions of massive stars (supernovae) and activity from supermassive black holes found at the heart of galaxies. Galactic gaseous outflows are initially also chaotic and flow away in all directions, but over time, they begin to become more focused along a path of least resistance.
In the late universe, flows out of galaxies take the form of two cones, emerging in opposite directions – like two ice cream cones placed tip to tip, with the galaxy swirling at the center. These flows of material slow down as they attempt to leave the gravitational well of the galaxy’s halo of invisible – or dark – matter, and can eventually stall and fall back, forming a galactic fountain of recycled gas. This process redistributes gas from the center of a galaxy to its outskirts, further accelerating the transformation of the galaxy itself into a thin disc: galactic structure shapes galactic fountains, and vice versa.
The team of scientists creating TNG50 (based at Max-Planck-Institutes in Garching and Heidelberg, Harvard University, MIT, and the Center for Computational Astrophysics (CCA)) will eventually release all simulation data to the astronomy community at large, as well as to the public. This will allow astronomers all over the world to make their own discoveries in the TNG50 universe – and possibly find additional examples of emergent cosmic phenomena, of order emerging from chaos.
“First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback” by Dylan Nelson, Annalisa Pillepich, Volker Springel, Rüdiger Pakmor, Rainer Weinberger, Shy Genel, Paul Torrey, Mark Vogelsberger, Federico Marinacci and Lars Hernquist, 29 August 2019, Monthly Notices of the Royal Astronomical Society. | 0.862204 | 4.023185 |
Hello, friends! Today I’d like to take you on a quick tour of the Alpha Centauri star system, the Solar System’s next door neighbors.
Alpha Centauri consists of three stars. Two of those stars orbit in a tight binary formation, sort of like this:
The third star is known as Proxima Centauri. It’s a tiny red dwarf star, orbiting very far away from that central binary pair. Proxima is known to have at least one (possibly two) planets, but we’ll visit Proxima’s planets in a future post.
Today, I really just want to focus on Alpha Centauri A and B, the two stars in that central binary, to see if they have any planets. In 2012, astronomers announced the discovery of a planet orbiting Alpha Centauri B, but that discovery turned out to be a ghost in the data. Otherwise, astronomers have found nothing out there.
Over the last decade or so, we’ve found so many exoplanets, both near and far. Given how close-by Alpha Centauri is, you’d think we would have found something there by now. It’s enough to make you wonder if, maybe, there’s nothing to find. But it turns out there’s a very good reason why we’re having so much trouble finding Alpha Centauri’s planets.
As Alpha Centauri A and B move through their figure-eight orbital paths, sometimes they’re close together, and sometimes they’re far apart. Over the past decade or so, it just so happens that they’ve been very close together, at least from our vantage point here on Earth. Even with all the advanced planet hunting techniques we’ve developed in the past ten years, the double glare of those two stars would’ve concealed any signs of a planet from our view.
But that’s about to change. In February of 2016, Alpha Centauri A and B were as close together as they’ll get (as seen from Earth). They’ve been moving away from each other ever since, and according to this article from Scientific American, 2020 is the magical year when A and B are finally far enough apart that our telescopes can observe them separately.
Based on the metallicity of those two stars, they should be just as capable of forming planets as our own Sun. Planetary orbits would be stable up to 2.5 astronomical units away from either star, according to Scientific American (our entire inner Solar System could fit comfortably inside that 2.5 A.U. radius). And computer simulations produce many plausible scenarios where Earth-like planets could exist in the Alpha Centauri binary.
In some of those computer simulations, an Alpha Centaurian planet might be even more suitable for life than Earth! So stay tuned. In the next few years, we may finally get news about habitable planets—or even a superhabitable planets—in Alpha Centauri.
Next time on Planet Pailly, how are you preparing for the robot rebellion? | 0.855156 | 3.712068 |
The irregular galaxy NGC 4485 shows all the signs of having been involved in a hit-and-run accident with a bypassing galaxy. Rather than destroying the galaxy, the chance encounter is spawning a new generation of stars, and presumably planets.
The right side of the galaxy is ablaze with star formation, shown in the plethora of young blue stars and star-incubating pinkish nebulas. The left side, however, looks intact. It contains hints of the galaxy's previous spiral structure, which, at one time, was undergoing normal galactic evolution.
The larger culprit galaxy, NGC 4490, is off the bottom of the frame. The two galaxies sideswiped each other millions of years ago and are now 24,000 light-years apart. The gravitational tug-of-war between them created rippling patches of higher-density gas and dust within both galaxies. This activity triggered a flurry of star formation.
This galaxy is a nearby example of the kind of cosmic bumper-car activity that was more common billions of years ago when the universe was smaller and galaxies were closer together.
NGC 4485 lies 25 million light-years away in the northern constellation Canes Venatici (the Hunting Dogs).
This new image, captured by Hubble's Wide Field Camera 3 (WFC3), provides further insight into the complexities of galaxy evolution.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. | 0.868942 | 3.378537 |
This is an artist's rendering of solar wind coming towards the Earth and its magnetosphere.
Click on image for full size
is flinging 1 million tons of matter out into space every second! We call this material solar wind.
Once the solar wind is blown into space, the particles travel at supersonic speeds of 200-800 km/sec! These particles travel all the way past Pluto and do not slow down until they reach the termination shock within the heliosphere
. The Heliosphere is the entire region of space influenced by the Sun.
The solar wind plasma is very thin. Near the Earth, the plasma is only about 6 particles per cubic centimeter. So, even though the wind travels SUPER fast, it wouldn't even ruffle your hair if you were to stand in it because it's so thin! But, it is responsible for such unusual things as:
The particles of the solar wind, and the Sun's magnetic field (IMF) are stuck together, therefore the solar wind carries the IMF (interplanetary magnetic field) with it into space.
Instruments like SWICS and SWOOPS onboard the Ulysses probe are studying solar wind. They are hoping to make a 3-D map of solar wind characteristics throughout the heliosphere.
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Scientists ask many questions. One of the questions they like to ask is "Where did the atmosphere come from?" As always, scientists chip in with many different, and sometimes conflicting answers. Some...more | 0.824373 | 3.386117 |
Monstrous gas cloud to smash into Milky Way Galaxy with ‘spectacular burst’
The Smith Cloud, a high-velocity cloud of hydrogen gas “is plummeting toward our galaxy at nearly 700,000 miles per hour,” said the team of astronomers who have been working with the Hubble Space Telescope.
The cloud, supposedly coming from the outer regions of the galactic disk where it originated about 70 million years ago, was discovered in the 1960s by doctoral astronomy student Gail Smith.
The “apocalypse” it brings is not going to happen tomorrow – the scientists found out that the cloud is expected to plow into the Milky Way's disk in some 30 million years.
When the collision takes place, it “will ignite a spectacular burst of star formation, perhaps providing enough gas to make 2 million suns,” the astronomers say.
"The cloud is an example of how the galaxy is changing with time," Andrew Fox, of the Space Telescope Science Institute in Baltimore, Maryland, said. "It's telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another."
And the cloud is really monstrous even up to space standards – the comet-shaped region of gas in the cloud is about 11,000 light-years long and 2,500 light-years across.
“If the cloud could be seen in visible light, it would span the sky with an apparent diameter 30 times greater than the size of the full moon,” astronomers say.
While the cloud is heading to our galaxy with monstrous speed (and probably monstrous intentions), the scientists try to unravel the mystery of the phenomenon. The researchers wonder how the cloud got to “where it is now” or what exactly catapulted it out of the Milky way.
“Could it be a region of dark matter — an invisible form of matter — that passed through the disk and captured Milky Way gas? The answers may be found in future research,” the scientists ask. | 0.870603 | 3.449079 |
The book “Setting Aside All Authority” comprises 10 chapters, 270 pages. The last half of the book is largely made up of two appendices: (A) the first English translation of Monsignor Francesco Ingoli’s essay to Galileo (disputing the Copernican system on the eve of the Inquisition’s condemnation of it in 1616) and (B) excerpts from the Italian Jesuit astronomer Giovanni Battista Riccioli’s reports on his experiments with falling bodies. The book is published by the University of Notre Dame, 2015.
The main thesis of the book challenges the notion that around the time of Galileo, and the beginning of the Copernican revolution, opponents of the heliocentric worldview, championed by Galileo, were primarily motivated by religion or dictates from the authority of the Roman Catholic Church.
The author, Christopher M. Graney, uses newly translated works by anti-Copernican writers of the time to demonstrate that they predominantly used scientific arguments and not religion in their opposition to the Copernican system. Graney argues that it was largely a science-versus-science debate, rather than church authority-versus-science as often incorrectly portrayed.
In the 1651, the Jesuit Giovanni Battista Riccioli published his book the New Almagest wherein he outlined 77 arguments against the Copernican system (pro-geocentrism) and 49 arguments in favour of it. Most arguments against the Copernican heliocentric system could be answered, at that time, but Riccioli, using the then available telescopic observations of the size of stars, was able to construct a powerful scientific argument that the pro-Copernican astronomers could not answer without an appeal to the greatness of God.
Graney largely uses Riccioli’s New Almagest, which argues in favour not of the Ptolemaic system but of the hybrid Tychonic system, where the Earth is immobile at the centre of the universe, the sun, the moon and the stars circle the earth; but the planets circle the sun. Riccioli built on the work of the Danish astronomer Tycho Brahe, and built a strong scientific case against the heliocentric system, at least through the middle of the seventeenth century, which was several decades after the advent of the telescope.
The main two arguments presented in the book, both scientific, are the size of stars and the effect on falling bodies.
If the earth were rotating, then a falling body should hit a point on the surface of the earth at a definite distance from a vertical line to the surface, if dropped vertically. The same argument could be made for cannon balls fired in different directions on the earth’s surface. These type of discussions and arguments carried on for a century, and even Isaac Newton got involved. What we now know as the Coriolis force, a ‘fictitious’ force, resulting from the rotation of the planet on the fired or dropped objects could not be measured with the required precision in the 17th century.
Riccioli carried out many precise ball dropping experiments. He intended to show that there was no deviation in the path of the falling bodies but he failed to get any conclusive result (due to many unknown and uncorrected errors). Also he had argued that experts firing cannon balls would have to correct for earth rotation (if the earth did rotate). However, it was found that the ‘experts’ were nowhere that good, they did not have that sort of precision or accuracy, and so that also was an inconclusive argument.
We know today that the rotation of the earth has to be taken into account for long-range military targeting of projectiles (due to the Coriolis force). Even highly accurate snipers firing over 1000 m are required to account for not only wind direction, wind speed, air density, elevation, but also the Coriolis effect due to the rotation of the earth.
In 1851, two hundred years after Riccioli’s publication of the New Almagest, Léon Foucault first demonstrated his pendulum in Paris. It was the first accurate demonstration of the effect of Earth rotation on falling bodies. The pendulum (Fig. 1) swings with a regular period and as the earth rotates the path of the pendulum successively moves to the left (as viewed from above) tracing out a circle. This is the effect of the Coriolis force. It is proof of the rotation of the planet.
Interestingly, the argument used by Galileo and other pro-Copernicans was that no effect on falling bodies could be detected due to common motion. Galileo used an analogy about an insect flying inside of a moving ship at sea. But Foucault’s pendulum proves that analogy to be invalid.
Sizes of stars
The size of stars argument went as follows. Sizes of stars were first measured by eye, before the invention of the telescope. That is what Tycho Brahe spent much of his time doing. That gave a ‘magnitude’ for a star, catalogued as magnitudes 1 through 6, with 1 the largest and 6 the smallest. Of course, large meant bright and small meant dim. It was based on these ‘measured’ sizes of stars that Tycho Brahe developed an argument against Copernicus.
Then with the invention of the telescope, it was observed that the star sizes were at least 10 times smaller. But because the astronomers also observed solid disks for the planets out to Saturn (and even phases for Venus) it was then believed that the telescope gave the true sizes of the stars also. Based on telescopic measurements of the star sizes, Riccioli formulated a version of the Brahe argument against the heliocentric system and in favour of the geocentric Tychonic system.
With the telescope, astronomers looked for parallax of the distant stars but were not able to detect any parallax. In the geocentric universe the earth is immobile and hence no parallax would be expected. In the heliocentric universe, the earth orbits the sun once per year, and in so doing, over a 6 month period it moves from one side of its orbit to the other. Therefore based on trigonometry, a foreground star should be seen to move against the more distant background stars as the earth moves between these two extrema. But of course the orbit is circular. Therefore if a star is close enough it should trace out a circle on the sky as seen from earth over a solar year.
Thus the argument followed: if a star was seen to have a certain size but it was too distant to exhibit any parallax, then it must be massively large, at least as large as the orbit of the earth around the sun. It was argued that that must be the case, otherwise no disk for the star could be observed. The only response the Copernican astronomers had to that was that God is a great God and He made such large stars for His own glory. Riccioli argued that it was not the geocentrists who appealed to authority but the heliocentrists, in their answer to the ‘size of stars’ argument—purely a scientific argument based on the best science of their day.
Real size of stars
Ironically, the geocentrists may not have made their own error (assuming that their telescopes gave the correct size of stellar disks) had they been privy to the English astronomer Horrocks’ report on the 1639 transit of Venus across the sun. During his observations, Horrocks noted that he observed the moon passing through the stars of the constellation Pleiades. As the leading dark edge of the moon passed in front of the stars they simply winked out. They vanished suddenly, meaning they did not transition to darkness as you might expect if their disk was being slowly covered by the dark edge of the moon. This meant that the ‘measured’ size of the stellar disks was in fact spurious—due to an unknown cause at that time. The sizes of the planets was correct because the telescope resolution was sufficient but it was not sufficient for distant stars.
But Horrocks’ report was not published until 1662, 11 years after Riccioli published his New Almagest. And in 1659 Christian Huygens published his observations of stars using filtering (with smoked glass) wherein he showed the star sizes changed with greater filtering. Thus it was soon realised that stars were actually point objects. In 1665 Riccioli published his Reformed Astronomy, in which he maintained his table of star sizes but de-emphasized the star-size argument.
Of course, if the stars are so enormously distant and if their ‘measured’ sizes are spurious, then the major scientific argument the geocentrists had against the heliocentrists evaporates. By 1720 Edmund Halley argued that the star sizes were spurious, but some astronomers still maintained the argument. A century later the English astronomer George Airy developed a full theoretical explanation for the spurious disk of stars. It explained both the appearance of disks and why they varied in size for different stars. This effect is known as an ‘Airy Disk’ and results from diffraction effects in the objective lens of the telescope. Because light has a wave nature adjacent beams interfere with each other creating a pattern of maxima and minima. Since the lens is circular it produces a central bright maximum surrounded by ever reducing surrounding rings. See Fig. 2. The same effect would be observed with the human eye (i.e. a lens) or a pin hole (i.e. no lens).
Thus Graney argues that it was not until the mid-nineteenth century before complete arguments supporting the Copernican system were developed for Riccioli’s arguments. The main two arguments were the size of stars, explained by their spurious observed disks, and the lack of precision of falling body experiments, after which it was shown via the Foucault pendulum that the earth does in fact move, rotating on its axis. Thus Graney argues that the old canard that astronomers of the seventeenth century held onto religion and authority as their argument against Galileo and the Copernican system is wrong. It was science against science and not science against religion per se. Both sides at times used religion but the ‘battle’ was primarily fought with science. | 0.903232 | 3.267214 |
New observations of a faraway asteroid may have given scientists the first piece of long-sought evidence that our solar system's gas giants once careened drunkenly through space, kicking smaller planetoids aside as they lurched half-formed through the cosmos.
The asteroid — named 2004 EW95 —was first discovered in 2004 orbiting about 2.5 billion miles (4 billion kilometers) away from Earth in the donut-shaped ring of ice and rock at the edge of our solar system called the Kuiper Belt. The Kuiper Belt begins beyond the orbit of Neptune, about 30 astronomical units from the sun, or about 30 times the distance between the sun and Earth, and may extend nearly as far into interstellar space. (One astronomical unit is about 93 million miles, or 150 million kilometers.) [Meteorites: Rocks That Survived Fiery Plunge to Earth]
The young solar system
While the belt is likely home to trillions of comets and hundreds of thousands of unexplored, icy planetoids (including the dwarf planet Pluto), scientists suspect that many thousands of the mysterious objects there originated much closer to Earth.
But how did those objects end up on the edge of the solar system? Some recent theories suggest they were thrown there by renegade gas giants like Jupiter and Saturn during the early days of our solar system's formation. According to these theories, the gas giants didn't start their life in a fixed orbit, but rather roared through the galaxy accreting material, bouncing against each other's gravity and launching the smaller, weaker bodies in their path far and wide into space.
If these theories are correct, some of the asteroids swirling around the Kuiper Belt must be the same sort of ancient, carbon-rich (or carbonaceous) asteroids commonly found in the asteroid belt between Mars and Jupiter today. But scientists haven't been able to find any of these carbonaceous asteroids in the Kuiper Belt — until now.
In a recent paper published in the March issue of the Astrophysical Journal Letters, an international team of researchers took a detailed look at the faint light reflecting off of the Kuiper asteroid 2004 EW95. With some help from the European Southern Observatory's Very Large Telescope (yes, that is its real name), the team collected detailed information on the light that reflected back from the asteroid during two separate sessions in 2014 and 2017. (Since different elements absorb and reflect different wavelengths of light, the light reflected back from an asteroid can reveal its composition.)
"The reflectance spectrum of 2004 EW95 was clearly distinct from the other observed outer solar system objects," lead author Tom Seccull, a postgraduate research student at Queen's University in Belfast, Northern Ireland, said in a statement.
Unlike other known Kuiper Belt objects, which are uniformly dark and largely featureless, 2004 EW95 reflected faint wavelengths that seemed to correspond to the presence of certain minerals. These minerals, called phyllosilicatesand ferric oxides, suggest that the object formed under similar conditions to many carbonaceous asteroids found much closer to Earth. However, the asteroid's light reflection data suggested 2004 EW95 also sustained a massive blow that caused it to heat up significantly.
"[These findings] are consistent with the idea that this object may have formed near Jupiter among the primordial [carbonaceous] asteroids and was subsequently emplaced into the Kuiper Belt by the migrating planets," the authors concluded in their paper.
If this ancient, faintly-glinting asteroid is indeed a carbon-rich exile thrown far from its original home by a surly gas giant, it provides a "key verification" to one of the dominant theories about the early days of our solar system, the researchers wrote — in which the gas giants partied it up by charging through the solar system and ejecting rocky bodies out into far-flung orbits.
Closer observation of the Kuiper Belt could yield thousands of other clues to the foundational mysteries of our solar system — and all we need is a Very Large Telescope to uncover them.
Originally published on Live Science. | 0.894737 | 4.028992 |
Hygiea is located in the main asteroid belt between Mars and Jupiter and is the fourth largest object in the main asteroid belt. Now, a new telescopic survey suggests Hygiea is a dwarf planet, due to its surprisingly spherical shape.
Largest documented asteroid breakup in the asteroid belt during the past two billion years caused enormous amounts of dust to spread through the solar system. The blocking effect of this dust lead to cooler temperatures which in turn caused diversification.
NASA’s New Horizons spacecraft, now 3.79 billion miles from Earth, snapped these images of Kuiper Belt Objects. They’re the furthest images ever taken away from Earth.
Astronomers have observed an unusual type of object in the asteroid belt between Mars and Jupiter: two asteroids orbiting each other and exhibiting comet-like features.
Scientists have identified a new dwarf planet in our Solar System, and it's lurking way out in the edges, some 13.6 billion km from the Sun.
The new data indicates that while Ceres, which is the largest body in the asteroid belt, was once warm enough for water to have shifted internally, those temperatures were never high enough for an iron core to separate from the rest of the dwarf planet's interior. | 0.814108 | 3.320371 |
Cosmic dust forms in supernovae blasts
Scientists claim to have solved a longstanding mystery as to how cosmic dust, the building blocks of stars and planets, forms across the Universe.
Cosmic dust contains tiny fragments or organic material and is spread out across the Universe. The dust is primarily formed in stars and is then blown off in a slow wind or a massive star explosion.
Up until now, astronomers have had little understanding as to why so much cosmic dust exists in the interstellar medium, with theoretical estimates suggesting it should be obliterated by supernova explosions.
A supernova is an event that occurs upon the violent death of a star and is one of the most powerful events in the Universe, producing a shockwave which destroys almost anything in its path.
Yet new research published in the Monthly Notices of the Royal Astronomical Society has observed the survival of cosmic dust around the closest supernova explosion detected to us, Supernova 1987A.
Observations using NASA's research aircraft, the Stratospheric Observatory for Infrared Astronomy (SOFIA), have detected cosmic dust in a distinctive set of rings that form part of Supernova 1987A.
The results seem to suggest that there is rapid growth of cosmic dust within the rings, leading the team to believe that dust may actually be re-forming after it is destroyed in the wake of a supernova blast wave.
This immediacy – that the post-shock environment might be ready to form or re-form dust – had never been considered before, and may be pivotal in fully understanding how cosmic dust is both created and destroyed.
"We already knew about the slow-moving dust in the heart of 1987A," said Dr. Mikako Matsuura, lead author on the paper from the School of Physics and Astronomy.
"It formed from the heavy elements created in the core of the dead star. But the SOFIA observations tell us something completely new."
Cosmic dust particles can be heated from tens to hundreds of degrees causing them to glow at both infrared and millimeter wavelengths. Observations of millimeter-wave dust emission can generally be carried out from the ground using telescopes; however, observations in the infrared are almost impossible to interference from the water and carbon dioxide in the Earth's atmosphere.
By flying above most of the obscuring molecules, SOFIA provides access to portions of the infrared spectrum not available from the ground. | 0.867776 | 3.981014 |
Your question will eventually lead you to Mach's Principle. It is an old, yet unsolved question, that still remains at the stage of "philosophical idea".
I understand that your question is equivalent to "What would be found if we could measure all effects on the pendulum with infinite accuracy?", what if even the tiniest contributions could be registered? (Please read the note at the end as well, regarding the effect on any pendulum of the proximity of mass, whether that pendulum is in a free-fall orbit or not. The effect of earth's orbital motion is not zero because it affects the speed rate of proper time)
Yes, some components of the acceleration on the pendulum allow to deduce that the pendulum belongs to a rotating frame. That leads to think that the pendulum and the whole Universe may eventually be found to be rotating around some point, but that idea makes no sense (what is that point then, if everything is rotating? Rotation relative to what?). Then Mach's principle comes to the rescue, telling us that inertia effects on your pendulum arise somehow from the influence of all the other objects of the Universe, from here to the most distant ones. But there is no mathematical model for such thing, not even in General Relativity.
The pendulum is blindly affected by the local conditions of space and time, which constantly change in time and from one point to another (although all effect other than those arising from the rotating frame on top of the bulk mass of the Earth are extremely tiny). Those conditions are determined by the arrangement of energy/mass and momentum around. In the newtonian model, by the mass distribution. This is useful because you can idealize a portion of the Universe in a model that allows you to predict some behaviour of the system: for instance the Schwarzschild metrics allow to accurately synchronize the clocks of the GPS satellites in their motion around the Earth, and to accurately model orbits close to the Sun. The homogeneous and isotropic Universe model allows to derive properties of the expansion in the past, etc. But there is no model for an accurate description of how the whole universe is affecting your pendulum.
In other words, the essential origin of inertia is still unknown. What is a Foucault pendulum eventually rotating around? There is no answer to that question. Moreover, it is not yet clear whether the question makes sense or not.
The most close answer to your question may be found in our motion relative to the Background radiation, found by means of the dipole anisotropy of the CBR. This is the closest thing that there is, to an "absolute reference frame" but it makes sense only for us. Other distant observers in out expanding Universe will have a completely different perception.
As correctly stated by Ben Crowell, the orbital motion is a free fall, and therefore its dynamical effects on the pendulum are different from those of being on top of the rotating Earth. However, that free fall happens along places with different values of the gravitational potential (bigger in January, for instance) and therefore the speed rate of pendulums is affected. Thus, your pendulum, as any other clock-alike device, is affected by all the other masses in the Universe.
You might think about placing several synchronized pendulums at different distant points on the surface of the Earth and, by measuring (with infinite accuracy) their speed rate differences, map some properties of the gravitational potential in which you are embedded, deducing for example the direction of a center of mass. This makes an interesting question if you want to start another post.
As for Mach's principle, let me stress that it is merely a philosophical idea, that may or may not some day lead to a real theory. It is neither correct nor incorrect.
There is often a fallacy motivated by the Equivalence Principle, in which people ignore the different speed rate of proper time inside the free-falling elevator. Yes, the man inside the free-falling elevator is unable to distinguish if he is in a gravitational field (but in free fall), or if he is floating in interstellar space, far away from any mass. But in the second case, the man inside the elevator is ageing faster that the one that is in free fall (orbit) around the Sun. This is another kind of twins paradox that is often forgotten. | 0.807349 | 3.692835 |
Detection of a supernova with an unusual chemical signature by a team of astronomers led by Carnegie’s Juna Kollmeier—and including Carnegie’s Nidia Morrell, Anthony Piro, Mark Phillips, and Josh Simon—may hold the key to solving the longstanding mystery that is the source of these violent explosions. Observations taken by the Magellan telescopes at Carnegie’s Las Campanas Observatory in Chile were crucial to detecting the emission of hydrogen that makes this supernova, called ASASSN-18tb, so distinctive.
Their work is published in Monthly Notices of the Royal Astronomical Society.
Type Ia supernovae play a crucial role in helping astronomers understand the universe. Their brilliance allows them to be seen across great distances and to be used as cosmic mile-markers, which garnered the 2011 Nobel Prize in Physics. Furthermore, their violent explosions synthesize many of the elements that make up the world around us, which are ejected into the galaxy to generate future stars and stellar systems.
Although hydrogen is the most-abundant element in the universe, it is almost never seen in Type Ia supernova explosions. In fact, the lack of hydrogen is one of the defining features of this category of supernovae and is thought to be a key clue to understanding what came before their explosions. This is why seeing hydrogen emissions coming from this supernova was so surprising.
Type Ia supernovae originate from the thermonuclear explosion of a white dwarf that is part of a binary system. But what exactly triggers the explosion of the white dwarf—the dead core left after a Sun-like star exhausts its nuclear fuel—is a great puzzle. A prevailing idea is that, the white dwarf gains matter from its companion star, a process that may eventually trigger the explosion, but whether this is the correct theory has been hotly debated for decades.
This led the research team behind this paper to begin a major survey of Type Ia supernovae—called 100IAS—that was launched when Kollmeier was discussing the origin of these supernovae with study co-authors Subo Dong of Peking University and Doron Kushnir of the Weizmann Institute of Science who, along with Weizmann colleague Boaz Katz, put forward an new theory for Type Ia explosions that involves the violent collision of two white dwarfs.
Astronomers eagerly study the chemical signatures of the material ejected during these explosions in order to understand the mechanism and players involved in creating Type Ia supernovae.
In recent years, astronomers have discovered a small number of rare Type Ia supernovae that are cloaked in large amount of hydrogen—maybe as much as the mass of our Sun. But in several respects, ASASSN-18tb is different from these previous events.
“It’s possible that the hydrogen we see when studying ASASSN-18tb is like these previous supernovae, but there are some striking differences that aren’t so easy to explain,” said Kollmeier.
First, in all previous cases these hydrogen-cloaked Type Ia supernovae were found in young, star-forming galaxies where plenty of hydrogen-rich gas may be present. But ASASSN-18tb occurred in a galaxy consisting of old stars. Second, the amount of hydrogen ejected by ASASSN-18tb is significantly less than that seen surrounding those other Type Ia supernovae. It probably amounts to about one-hundredth the mass of our Sun.
“One exciting possibility is that we are seeing material being stripped from the exploding white dwarf’s companion star as the supernova collides with it,” said Anthony Piro. “If this is the case, it would be the first-ever observation of such an occurrence.”
“I have been looking for this signature for a decade!” said co-author Josh Simon. “We finally found it, but it’s so rare, which is an important piece of the puzzle for solving the mystery of how Type Ia supernovae originate.”
Nidia Morrell was observing that night, and she immediately reduced the data coming off the telescope and circulated them to the team including Ph.D. student Ping Chen, who works on 100IAS for his thesis and Jose Luis Prieto of Universidad Diego Portales, a veteran supernova observer. Chen was the first to notice that this was not a typical spectrum. All were completely surprised by what they saw in ASASSN-18tb’s spectrum.
“I was shocked, and I thought to myself ‘could this really be hydrogen?'” recalled Morrell.
To discuss the observation, Morrell met with team member Mark Phillips, a pioneer in establishing the relationship—informally named after him—that allows Type Ia supernovae to be used as standard rulers. Phillips was convinced: “It is hydrogen you’ve found; no other possible explanation.”
“This is an unconventional supernova program, but I am an unconventional observer—a theorist, in fact” said Kollmeier. “It’s an extremely painful project for our team to carry out. Observing these things is like catching a knife, because by definition they get fainter and fainter with time! It’s only possible at a place like Carnegie where access to the Magellan telescopes allow us to do time-intensive and sometimes arduous, but extremely important cosmic experiments. No pain, no gain.”
More information: Juna A Kollmeier et al. Hα emission in the nebular spectrum of the Type Ia supernova ASASSN-18tb★. Monthly Notices of the Royal Astronomical Society (2019). DOI: 10.1093/mnras/stz953 ,
Image: This cartoon courtesy of Anthony Piro illustrates three possibilities for the origin of the mysterious hydrogen emissions from the Type Ia supernova called ASASSN-18tb that were observed by the Carnegie astronomers. Starting from the top and going clockwise: The collision of the explosion with a hydrogen-rich companion star, the explosion triggered by two colliding white dwarf stars subsequently colliding with a third hydrogen-rich star, or the explosion interacting with circumstellar hydrogen material. Credit: Carnegie Institution for Science | 0.844229 | 4.219792 |
The Hertzsprung-Russell diagram of the Large Magellanic Cloud compiled recently by Fitzpatrick & Garmany (1990) shows that there are a number of supergiant stars immediately redward of the main sequence although theoretical models of massive stars with normal hydrogen abundance predict that the region 4.5 ≤ logTeff ≤ 4.3 should be un-populated (“gap”). Supergiants having surface enrichment of helium acquired for example from a previous phase of accretion from a binary companion, however, evolve in a way so that the evolved models and observed data are consistent — an observation first made by Tuchman & Wheeler (1990). We compare the available optical data on OB supergiants with computed evolutionary tracks of massive stars of metallicity relevant to the LMC with and without helium-enriched envelopes and conclude that a large fraction (≈ 60 per cent) of supergiant stars may occur in binaries. As these less evolved binaries will later evolve into massive X-ray binaries, the observed number and orbital period distribution of the latter can constrain the evolutionary scenarios of the supergiant binaries. The distributions of post main sequence binaries and closely related systems like WR + O stars are bimodal-consisting of close and wide binaries in which the latter type is numerically dominating. When the primary star explodes as a supernova leaving behind a neutron star, the system receives a kick and in some cases can lead to runaway O-stars. We calculate the expected space velocity distribution for these systems. After the second supernova explosion, the binaries in most cases, will be disrupted leading to two runaway neutron stars. In between the two explosions, the first born neutron star’s spin evolution will be affected by accretion of mass from the companion star. We determine the steady-state spin and radio luminosity distributions of single pulsars born from the massive stars under some simple assumptions. Due to their great distance, only the brightest radio pulsars may be detected in a flux-limited survey of the LMC. A small but significant number of observable single radio pulsars arising out of the disrupted massive binaries may appear in the short spin period range. Most pulsars will have a low velocity of ejection and therefore may cluster around the OB associations in the LMC.
Volume 41, 2020
Continuous Article Publishing mode
Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.
Click here for Editorial Note on CAP Mode | 0.802316 | 3.978036 |
Explore the starry skies of April! There will be a number of intriguing celestial sights to enjoy with the help of a binocular or telescope. Here are a few of our favorites:
Mercury After Sunset - On April 1st, Mercury will reach its greatest eastern elongation of just under 20 degrees from the Sun, which means the planet will reach its highest point above Earth's horizon. Catch a glimpse of tiny Mercury in binoculars just above the western horizon right after sunset, or use a [telescope] for a closer look. Since Mercury is very small in the sky, locating it can be a challenge. Try looking for a bright "star" in the western sky that doesn't appear to twinkle as much as surrounding stars. Chances are you've found Mercury!
Jupiter at Opposition - Gigantic Jupiter reaches opposition on April 7th, making it the best night of the year to explore the gas giant planet. While Jupiter can be detected in almost any size telescope, the most rewarding views of the gas giant planet and its four brightest moons can be found in larger refractor and reflector telescopes with moderate to high power eyepieces. Opposition occurs when a planet reaches its closest approach to Earth in its elliptical orbit. Since Jupiter will be directly opposite the Sun from Earth on April 7th, it will be visible all night long - rising at sunset and setting at sunrise. Take advantage of Jupiter's brightest night of the year and take a closer look at its striking cloud band "stripes" and four Galilean moons Io, Europa, Ganymede and Callisto. Use an [Orion Jupiter Observation Filter] to reveal cloud belt details and improve contrast in your views of the biggest planet in our solar system.
Jupiter and the Moon - Just a few days after reaching opposition, gas giant planet Jupiter pairs up with the Moon to make a pretty pairing in the night sky. Get outside at sunset on April 10th to see gas giant planet Jupiter appear as close as 2.4° South of the nearly Full Moon. Both Jupiter and the Moon will rise together over the eastern horizon just a few moments after sunset.
Spring Brings Galaxy Season! - April skies provide stargazers with ample opportunities to observe far-off galaxies. With the Virgo Galaxy Cluster and bright galaxies in the Big Dipper and Coma Berenices well-positioned in the sky, April evenings are truly a gift for galaxy hounds. Check out a few of our favorite galaxies: M101, M51, and M106 near the Big Dipper asterism; M86, M87, M84 and M104 in the Virgo Galaxy Cluster; and don't miss NGC 4565, M64, M99, and M100 in the constellation Coma Berenices. While a humble 80mm telescope will show most of the galaxies we mention, a big reflector like our [SkyQuest XT10 Classic Dobsonian] will provide jaw-dropping views of these distant galaxies!
International Dark Sky Week - From Saturday April 22nd through Friday April 28th, celebrate International Dark Sky Week by keeping your outdoor lights turned off after sunset to reduce light pollution. Endorsed by the International Dark-Sky Association and the American Astronomical Society, International Dark Sky Week presents an opportunity to appreciate the beautiful night sky without the adverse effects of light pollution from outdoor lighting. Turn out those lights and enjoy views of the starry sky from your own backyard!
Lyrids Meteor Shower - Kick off International Dark Sky Week by getting outside after midnight on the night of April 22nd to enjoy the peak of the Lyrids Meteor Shower. Look for meteors to radiate outwards from the constellation Lyra after midnight on the 22nd into the early hours of April 23rd. The Lyrids is a medium shower which can produce about 20 meteors per hour during its peak. The waning crescent Moon will be out when shower activity peaks, but it shouldn't make it too difficult to spot meteors. The Lyrids shower often produces meteors with impressive dust trails that can last several seconds. You don't need a telescope to enjoy the show - just sit back in a comfy chair and watch bright dust trails flare across the sky.
April's Deep Sky Challenge: Leo Galaxy Cluster - You'll want a big reflector telescope and dark, clear skies to go after this month's challenge object; the compact galaxy cluster Hickson 44, also named the Leo Quartet, or Galaxy Cluster NGC 3190, after its brightest member. This grouping of distant galaxies is located less than halfway between the stars Adhafera (Zeta Leonis) and Algieba (Gamma Leonis) along the sickle asterism of constellation Leo. This grouping of faint galaxies is quite challenging to detect in telescopes, so we recommend using a larger [Dobsonian] reflector to find out how many galaxies you can see. | 0.882705 | 3.38685 |
Here are the remnants of last supernova that is known to explode in our galaxy Milky Way. The light of explosion had reached the Earth some 400 years back and had amazingly lit up the night sky in October 1604.
The then mathematician and astronomer Johannes Kepler had then studied the event. But that was the time when telescope was not invented. In his memory, the event has been termed as Kepler’s Supernova Remnant.
Now we have not just telescopes but we also have giant orbiting space telescopes which keep on exploring and scanning the stellar events.
Here is the explanation of NASA about the event :
The supernova produced a bright new star in early 17th century skies within the constellation Ophiuchus. It was studied by astronomer Johannes Kepler and his contemporaries, without the benefit of a telescope, as they searched for an explanation of the heavenly apparition. Armed with a modern understanding of stellar evolution, early 21st century astronomers continue to explore the expanding debris cloud, but can now use orbiting space telescopes to survey Kepler’s SNR across the spectrum.
Recent X-ray data and images of Kepler’s Supernova Remnant taken by the orbiting Chandra X-ray Observatory has shown relative elemental abundances typical of a Type Ia supernova, and further indicated that the progenitor was a white dwarf star that exploded when it accreted too much material from a companion Red Giant star and went over Chandrasekhar’s limit. About 13,000 light years away, Kepler’s supernova represents the most recent stellar explosion seen to occur within our Milky Way galaxy. | 0.884942 | 3.493448 |
This approximate natural-color image shows Saturn, its rings, and four of its icy satellites. Three satellites (Tethys, Dione, and Rhea) are visible against the darkness of space, and another smaller satellite (Mimas) is visible against Saturn's cloud tops very near the left horizon and just below the rings. The dark shadows of Mimas and Tethys are also visible on Saturn's cloud tops, and the shadow of Saturn is seen across part of the rings. Saturn, second in size only to Jupiter in our Solar System, is 120,660 km (75,000 mi) in diameter at its equator (the ring plane) but, because of its rapid spin, Saturn is 10% smaller measured through its poles. Saturn's rings are composed mostly of ice particles ranging from microscopic dust to boulders in size. These particles orbit Saturn in a vast disk that is a mere 100 meters (330 feet) or so thick. The rings' thinness contrasts with their huge diameter--for instance 272,400 km (169,000 mi) for the outer part of the bright A ring, the outermost ring visible here. The pronounced concentric gap in the rings, the Cassini Division (named after its discoverer), is a 3500-km wide region (2200 mi, almost the width of the United States) that is much less populated with ring particles than the brighter B and A rings to either side of the gap. The rings also show some enigmatic radial structure ('spokes'), particularly at left. This image was synthesized from images taken in Voyager's blue and violet filters and was processed to recreate an approximately natural color and contrast. | 0.85669 | 3.662948 |
Emma is one of my regular guest bloggers. I feel really thrilled about the possibility to post one educating post of this great blogger once a month over the next couple of months. Thank you so much, Emma, for sharing these great posts with us! If you would like to check out the previous guest posts, this amazing blogger wrote for me, head over here.
Black holes. They’re some of the most incredible, and most elusive, phenomena in the universe.
Most of the things we know about the universe, we know through data gathered using the electromagnetic spectrum. That’s basically a spectrum of energy wavelengths. Visible light is a tiny, tiny part of it. And everything in the universe emits electromagnetic radiation.
Well, almost everything.
Black holes defy analysis. We can’t reach out and touch the universe, so we need the electromagnetic spectrum—in the form of visible light, infrared radiation, X rays, and others—to know what’s out there. But black holes don’t emit anything.
They just gobble up everything. Their immense, powerful gravitational fields suck in all matter, energy, light, time, etc. that is unfortunate enough to slip past what we call the “event horizon.”
So if we can’t reach out and touch them, and we can’t see them, how do we know they’re there?
First of all, we may not be able to see black holes, but we can see the stuff that gets pulled into them. The problem is, it’s hard to tell if it’s a black hole we’re seeing, or just a faraway object that looks too dim to see from our corner of the universe.
The most direct way to observe a black hole is by using something astronomers call “redshift.” To get a better idea of redshift, let’s take a look at some sound waves.
Have you heard the ice cream truck recently?
I don’t know if the ice cream truck is a worldwide thing, but where I grew up, we heard it all the time. It would drive down the road, its merry tune growing louder and louder as it got closer.
And then as it moved away, it would get quieter and quieter, until we didn’t hear it at all.
I’ll tell you what’s happening here: a simple, sound wave version of redshift and blueshift.
The volume of a sound is determined by the wavelength. Wavelength is a little different for sound than for light, but let’s not argue technicalities here.
Basically, the longer the wavelength, the quieter the sound. The shorter the wavelength, the louder the sound.
As an ice cream truck, ambulance, or really any kind of vehicle making a noise moves toward you, the wavelength of the sound doesn’t change. It seems to get squished, as you see above. The wavelengths thus seem to be shorter, so it seems to be getting louder.
The same goes for anything moving away from you. As the distance between you and the vehicle widens, the wavelength still doesn’t change. But it seems to get stretched, so the sound seems to be getting quieter.
So how does this work for black holes?
Well, this whole redshift/blueshift thing works in a similar way for light. Redshift is what we call it when the light wavelengths get stretched…because red light is just visible light wavelengths being stretched as far as they can go without becoming invisible.
And blueshift is what we call it when light wavelengths get squished, because blue light is just visible light wavelengths being squished as much as they can without becoming invisible.
All this is important because the one defining characteristic of a black hole—at least as far as we can easily observe—is that stuff whizzes around it fast.
The orbital velocities around a black hole are absolutely extraordinary. If black holes are the racetracks of the universe, every single star in orbit receives a grand prize. And this comes in really handy for us—because extraordinary velocities mean dramatic redshift.
Here’s the redshift we observe from stars orbiting around a black hole. Usually, when we observe redshift, it’s miniscule. Like, a fraction of what you see above. That’s because stars don’t usually move all that fast.
When we’re looking at a black hole, though, we’re seeing tons of stars whizzing around at dizzying velocities—dizzying, that is, if you’re in space. The funny thing is, time in space moves a lot slower than you’re used to on Earth. Maybe it’s because of our short lifespans—we live each day moment by moment. Stars, on the other hand, take their sweet time. Because time may wait for no man, but it certainly waits for the universe.
Think about it. If stars have orbits that are angled so that half the time, they move towards you, and half the time, they’re swinging off away from you, you’re going to see redshift and blueshift. And if they’re whizzing around a black hole, it will be dramatic.
I just spent the last couple paragraphs talking about knowing it’s a black hole by stars orbiting around it at fantastic speeds. What happened to everything in the vicinity being gobbled up?
Well…every heard of the Schwarzschild radius?
A black hole is often referred to as a singularity—a single, infinitely dense point in time and space where matter is sucked in…and, as far as we can tell, sucked out of the known universe.
Beyond this singularity, unimaginable gravitational force wreaks havoc on anything in the vicinity. If you’re between the singularity and the event horizon, you’re basically dead.
Well…spaghettified is a more accurate description. You’ll die of being stretched beyond your body’s tolerance.
The Schwarzschild radius is the distance between the singularity and any point on the event horizon. And if you’re outside the event horizon, you’re safe. That’s why stars can continue to orbit around a black hole…right until the day they swing too close, and then begin the inexorable descent into uncharted territory.
Because it’s literally impossible to see beyond the event horizon, no one’s entirely sure what happens inside it. Last I heard, it was suspected that time itself gets a bit warped—gravity is caused by a dent in the fabric of space-time, after all, and time is part of that equation.
What happens when you reach the singularity? I’m not sure anyone knows. There have been all sorts of theories…
What if a black hole opens up into a white hole?
Mind you, this one’s purely theoretical, and it’s only called a white hole because it’s the opposite of a black hole.
Anyway…let’s get out of the theoretical, and back into the realm of “beyond a reasonable doubt,” as scientists like to say.
So, how does a black hole form, anyway?
A black hole is basically the result of gravitational collapse. An object’s gravity becomes so powerful that it can’t sustain its own density, and the object falls through the fabric of space-time to become a singularity. And it can happen to anything.
Even the Earth.
This is highly unlikely to ever happen, but if the Earth got smushed down to the size of a marble without losing any of its mass, then it would become a singularity.
Planets don’t usually get smushed down into black holes, though. It’s more common—and more in the range of reasonable doubt—for a black hole to form at the end of a star’s life cycle.
A star begins its life within a nebula, where dust and gas collects together until the star has enough gravity to draw in even more dust and gas. A star is born once its gravity drives pressures beneath its surface to generate incredible amounts of energy.
The star can then support a solar system, and starts its family by drawing gas and dust into orbit around it. That gas and dust collects to create planets in individual orbits, and the solar wind from the star blows the remaining gases away.
An average star, like our sun, burns bright for billions of years before eventually expanding, blowing off its outer layers, and fading away into a white dwarf.
A larger, more massive star, on the other hand, burns bright for only around 20 or so million years before expanding. Its demise is more spectacular, however, and it implodes into a supernova. That’s right—a supernova is not an explosion, it’s an implosion. It’s the beginning of that gravitational collapse we talked about.
After that, the supernova might just settle into existence as a neutron star. But if it has enough mass, the gravitational collapse and matter implosion will continue and form a singularity. And thus, a black hole is born.
These black holes are believed—beyond a reasonable doubt—to be at the center of every large galaxy. There’s one at the center of ours. But don’t worry about getting gobbled up in the near future—the central bulge of the galaxy, where all the stars near the black hole are whizzing around it, will be the first to go.
And it’s not going anywhere anytime soon. It’s been around for millennia. Technically, billennia, though that’s not really a word. In fact, I wouldn’t worry about our black hole at all—our sun will expand and swallow us whole before any black hole comes to get us.
Not comforting, I know. But that’s all still generations away. | 0.884771 | 3.5012 |
Using observations with NASA’s Chandra X-ray Observatory and ESA’s
XMM-Newton, astronomers have announced a robust detection of a vast reservoir of intergalactic gas about 400 million light years from Earth.
This discovery is the strongest evidence yet that the “missing matter” in the nearby Universe is located in an enormous web of hot, diffuse gas.
This missing matter — which is different from dark matter — is composed of baryons, the particles, such as protons and electrons, that are found on the Earth, in stars, gas, galaxies, and so on. A variety of measurements of distant gas clouds and galaxies have provided a good estimate of the amount of this “normal matter” present when the universe was only a few billion years old. However, an inventory of the much older, nearby universe has turned up only about half as much normal matter, an embarrassingly large shortfall.
The mystery then is where does this missing matter reside in the nearby Universe? This latest work supports predictions that it is mostly found in a web of hot, diffuse gas known as the Warm-Hot Intergalactic Medium (WHIM). Scientists think the WHIM is material left over after the formation of galaxies, which was later enriched by elements blown out of galaxies.
“Evidence for the WHIM is really difficult to find because this stuff is so diffuse and easy to see right through,” said Taotao Fang of the University of California at Irvine and lead author of the latest study. “This differs from many areas of astronomy where we struggle to see through obscuring material.”
To look for the WHIM, the researchers examined X-ray observations of a rapidly growing supermassive black hole known as an active galactic nucleus, or AGN. This AGN, which is about two billion light years away, generates immense amounts of X-ray light as it pulls matter inwards.
Lying along the line of sight to this AGN, at a distance of about 400 million light years, is the so-called Sculptor Wall. This “wall”, which is a large diffuse structure stretching across tens of millions of light years, contains thousands of galaxies and potentially a significant reservoir of the WHIM if the theoretical simulations are correct. The WHIM in the wall should absorb some of the X-rays from the AGN as they make their journey across intergalactic space to Earth.
Using new data from Chandra and previous observations with both Chandra and
XMM-Newton, absorption of X-rays by oxygen atoms in the WHIM has clearly been detected by Fang and his colleagues. The characteristics of the absorption are consistent with the distance of the Sculptor Wall as well as the predicted temperature and density of the WHIM. This result gives scientists confidence that the WHIM will also be found in other large-scale structures.
Several previous claimed detections of the hot component of the WHIM have been controversial because the detections had been made with only one X-ray telescope and the statistical significance of many of the results had been questioned.
“Having good detections of the WHIM with two different telescopes is really a big deal,” said co-author David Buote, also from the University of California at Irvine. “This gives us a lot of confidence that we have truly found this missing matter.”
In addition to having corroborating data from both Chandra and XMM-Newton, the new study also removes another uncertainty from previous claims. Because the distance of the Sculptor Wall is already known, the statistical significance of the absorption detection is greatly enhanced over previous “blind” searches. These earlier searches attempted to find the WHIM by observing bright AGN at random directions on the sky, in the hope that their line of sight intersects a previously undiscovered large-scale structure.
Confirmed detections of the WHIM have been made difficult because of its extremely low density. Using observations and simulations, scientists calculate the WHIM has a density equivalent to only 6 protons per cubic meter. For comparison, the interstellar medium — the very diffuse gas in between stars in our galaxy — typically has about a million hydrogen atoms per cubic meter.
“Evidence for the WHIM has even been much harder to find than evidence for dark matter, which is invisible and can only be detected indirectly,” said Fang.
There have been important detections of possible WHIM in the nearby Universe with relatively low temperatures of about 100,000 degrees using ultraviolet observations and relatively high temperature WHIM of about 10 million degrees using observations of X-ray emission in galaxy clusters. However, these are expected to account for only a relatively small fraction of the WHIM. The X-ray absorption studies reported here probe temperatures of about a million degrees where most of the WHIM is predicted to be found.
These results appear in the May 10th issue of The Astrophysical Journal. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass. | 0.850079 | 4.1686 |
Enceladus is having a moment: ever since NASA announced it had all the basic ingredients to support life, people have become interested in the unusual Saturnian moon. In addition to hiding a warm subterranean ocean beneath its crust, Enceladus produces enough energy from its hydrothermal vents that could hypothetically support alien microbes. To add another layer of weirdness to this strange world, new research suggests Enceladus may have tipped over long ago.
After studying information collected by NASA’s Cassini spacecraft, a team of scientists thinks they’ve found evidence that Enceladus’ spin axis—the imaginary line through its north and south poles—has shifted about 55 degrees away from its original axis. According to the researchers, the most likely reason is that a smaller object, like an asteroid, collided with the moon, causing it to reorient. A smash-up has previously been used to explain Enceladus’ unusual “tiger stripes,” geysers of water erupting at the moon’s current south pole. The team’s research was published in April in the journal Icarus.
“The geological activity in this [tiger stripe] terrain is unlikely to have been initiated by internal processes,” the study’s lead author, Radwan Tajeddine, a Cassini imaging team associate at Cornell University, said in a statement. “We think that, in order to drive such a large reorientation of the moon, it’s possible that an impact was behind the formation of this anomalous terrain.”
If Enceladus was indeed walloped by a giant space rock long ago, it would have redistributed the moon’s mass. According to NASA, it would have taken Enceladus over a million years to get its shit together and stabilize—in the meantime, its north and south poles would have shifted greatly in a phenomenon called “true polar wander.” Polar wander, which has also been used to explain the curious equatorial placement of Pluto’s famous heart region, could explain why Enceladus’ north and south poles look so unbelievably different from one another. For one thing, the north pole doesn’t have those hydrothermal vents spewing water vapour.
While Enceladus is still shrouded in icy mysteries, hopefully, cracking a few will help us figure out what this world is hiding. Maybe, just maybe, we’ll get to find some space narwhals lurking below its surface. [NASA]
More Space Posts:
Figuring out what they really are and how they really work will continue to be a challenge.
Jupiter is the wild west of the solar system, and an incredible view of its rings proves just how true that is.
By studying zigzag patterns from the crash, scientists have been able to estimate the speed and size of the offending object.
Gizmodo sat down with Leland Melvin to talk about diversity in STEAM fields, education, and of course, Good Dogs in Space. | 0.838798 | 3.73797 |
We’ve used the 3 most powerful optical telescopes on Earth to test a fundamental law of nature 10 billion years ago!
Swinburne University PhD student, Tyler Evans, led this new work to comprehensively compare spectra of a single, distant quasar gathered using three different telescopes – the Very Large Telescope in Chile, the Keck Observatory in Hawaii and the Subaru Telescope, also in Hawaii. Why three telescopes? Because we’re measuring one of nature’s “fundamental constants”, so we want to make absolutely sure we get it right.
Here’s an info-graphic explaining our experiment (larger versions are available in the gallery below):3 telescopes testing nature’s laws in 3 distant galaxies. Image credit: Swinburne Astronomy Productions.
We targetted the quasar – a supermassive black hole whose surroundings glow hundreds of times brighter than a galaxy – because we knew (from previous observations) it had 3 galaxies along the line of sight from Earth. We took a spectrum of the quasar with the 3 telescopes, spreading the light our into its colours, to reveal the characteristic signatures of gas in these galaxies: some very specific colours are absorbed out of the light beam. This pattern of dark lines (missing colours) in the spectrum is like a barcode: it encodes the value called the “fine structure constant” – effectively, the strength of electromagnetism – in the galaxies. All we have to do is read this barcode (using some fancy techniques) to measure this fundamental quantity in the distant universe!
By getting three copies of the spectrum, we can check to make sure the barcode we’re reading really is correct. If the specialised prisms on the telescopes that separate the light into its component colours somehow distort the barcodes a bit, then we won’t measure the correct strength of electromagnetism. That is, if some of the dark lines are shifted around, even by a few parts in a million, we’re able to detect it by cross-checking the spectra (rainbows) from the 3 different telescopes.
Actually, we did find some small distortions like this, but we’re able to correct for them. Once corrected, our measurements of electromagnetism in all 3 galaxies, on all 3 telescopes, agree with the strength found here on Earth.
All this triple checking means that our new measurement is probably the most reliable one ever made of electromagnetism outside our Milky Way galaxy.
Find the details in our paper here:
Evans T.M., Murphy M.T., Whitmore J.B., Misawa T., Centurión M., D’Odorico S., Lopez S., Martins C.J.A.P., Molaro P., Petitjean P., Rahmani H., Srianand R., Wendt M.,
The UVES large program for testing fundamental physics – III. Constraints on the fine-structure constant from 3 telescopes,
2014, Mon. Not. Roy. Astron. Soc., accepted, arXiv:1409.1923. | 0.847126 | 3.835489 |
Dark matter may not be part of a "dark sector" of particles that mirrors regular matter, as some theories suggest, say scientists studying collisions of galaxy clusters.
When clusters of galaxies collide, the hot gas that fills the space between the stars in those galaxies also collides and splatters in all directions with a motion akin to splashes of water. Dark matter makes up about 90 percent of the matter in galaxy clusters: Does it splatter like water as well?
New research suggests that no, dark matter does not splatter when clusters of galaxies collide, and this finding limits the kinds of particles that can make up dark matter. Specifically, the authors of the new research say it is unlikely that dark matter is part of an entire "dark sector" — a mirror version of the visible universe. [Dark Matter: A Cosmic Mystery Explained (Infographic)]
Colliding galaxy clusters
Our galaxy contains hundreds of billions of stars, and there are hundreds of billions of galaxies in the observable universe. There's also a lot of gas and dust between the stars and the galaxies. But all of those stars, galaxies, gas and dust make up only about 10 to 15 percent of the matter in the universe.
The other 85 to 90 percent is dark matter. Scientists don't know what dark matter is made of or where it comes from, only that it doesn't appear to reflect or radiate light. It does, however, exert a gravitational pull on the regular matter around it.
David Harvey, a postdoctoral researcher at the Swiss Federal Institute of Technology Lausanne, is one of many scientists currently trying to figure out what dark matter is made of. There are lots of ways to go about this, and Harvey decided to see what happens when dark matter collides with itself.
To do this, Harvey and his colleagues at the University of Edinburgh, where Harvey did his PhD work, looked at collisions among entire clusters of galaxies, where as much as 90 percent of the mass involved in the collision is dark matter, according to a statement from the Swiss Federal Institute of Technology Lausanne.
"[Galaxy cluster mergers] are incredibly messy," Harvey said. "You've got [the stars], the highest densities of dark matter and hot gas all swirling together."
Scientists have tried to use these galaxy cluster crashes to study dark matter for decades, but improved techniques for observing the different components of those mergers has inspired a revival, he said. "We wanted to have a big statistical sample that tries to average over all these different merging scenarios, and try to get a statistical idea of what dark matter is doing during these cosmological crashes."
During these incredibly large-scale mergers, scientists have observed that individual stars in these galaxies are so far apart that they very rarely run into one another. So, rather than creating a big, messy wreck, the stars sort of neatly fold together.
However, in between the galaxies is a thick gas full of charged particles. When the galaxy clusters collide, the gas splatters in all directions, like water splashed from a puddle, Harvey said.
"If we measure the dark matter [after the collision], and should it lie where the galaxies are, we know the dark matter is completely collisionless, and doesn't interact with itself at all," Harvey said. "And if it should lie where the gas is, we'd say that the dark matter is actually interacting with itself a lot, like a liquid."
The researchers gathered data on a total of 30 galaxy-cluster collisions. In order to see the stars, the gas and the dark matter, they needed observations from NASA's Hubble Space Telescope and Chandra X-ray Observatory. [Chandra Observatory's X-ray Universe in Photos]
Dark matter doesn't radiate or reflect light, but its gravitational pull can help scientists "see" it. Light that is passing near a very massive object will bend around it, in an effect called gravitational lensing. Scientists can see the bending of the light and use that to figure out where dark matter is present.
By looking at 30 galaxy-cluster mergers, the researchers showed that the dark matter behaves more like the stars: It doesn't splatter during these collisions, but instead remains largely unchanged by the merger.
The dark sector
The implications of the new finding go beyond galaxy mergers: They tell scientists something about what dark matter might be made of.
The gas that is found in between the galaxy clusters tends to splatter during collisions because it interacts with itself, the way a liquid does. Notice how liquids in microgravity tend to join together into bubbles — the material sticks together even though it isn't bound together like a solid.
Protons — the particles at the heart of every atom — interact with one another in a similar way. Harvey and his colleagues showed that dark matter clearly doesn't interact with itself the way the gas does; more specifically, it interacts with itself less than protons interact with one another.
Some theories of dark matter posit that it is part of a "dark sector" that is sort of like a mirror of the regular universe — in other words, that it contains dark versions of regular matter particles, like dark photons and dark electrons. In some of those theories, dark matter might be made up of dark protons.
"Chances are that dark matter is not made up of dark protons interacting with dark protons, and chances are, there is not a mirror universe out there with these dark particles," Harvey said. "The caveat is that theorists could change some of their parameters, so the field is still open to what [dark matter] could be, but we're narrowing it down."
- Top 10 Strangest Things in Space
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- Dark Matter Detected? Researchers See 'Possible Signal' | Video
Copyright 2015 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Copyright SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.831358 | 3.972102 |
Comet 2020 F8 has dimmed well below “eyes only” visibility and seems destined for obscurity. Now that it has passed Perigee (closest distance to the Earth) and is passing Perihelion (closest distance to the sun), there can be no expectation of brightening, based on distance alone. Another outburst of erupted gas and dust also seems unlikely, so this is probably the end of the story for C/2020 F8.
Next, I am thinking of a project to confirm the rotation period of a historical comet using the phase analysis as described in my Comet Update of April 26. This will utilize that data at the Comet Observation database. It will serve as proof that I am doing this analysis correctly.
Amateur astronomers can make valuable contributions to comet science by observing comets and submitting their observations to COBS as professional astronomers typically do not have telescope time required to acquire regular observations. We therefore encourage comet observers worldwide to submit their observations and contribute to the COBS database.”
Comet 2020 F8 has dimmed from its last outburst and is now just barely qualified to be “eyes only visible”. I call it that only in the abstract since I have attempted to spot it several times with binoculars without success. I live on the west side of Houston and the place where the comet is theoretically visible is in the northeastern sky – which is awash in city-light at best – just before dawn. My carefully chosen location is down south on a road that leads to Brazos Bend State Park where I was a volunteer telescope operator at the George Observatory.
You may ask why I did not use that telescope to view the comet. It is that the public viewing program at “The George” was suspended late last year for renovations to the observatory and museum facilities. It was all set for a grand re-opening when the current disruption concerning the Communist Chinese Xi Jinping Virus began.
My attempts at viewing the comet took place on mornings this past week when skies were allegedly clear. None were successful – due mostly to the aforementioned urban skies. The path of the comet is from the southern extreme of the Solar System – crossing into the northern skies – where it is now found – and exiting back to the south. Because it is closer to the Sun now, it can only be seen in the early morning. Later this month it will appear in the evening sky just after sunset. More on that later.
The diagram in Figure 1 shows the current positions of the comet and Earth. Mercury and Venus are seen but not labeled. I dotted the comet’s path when it occupies the southern part of the Solar System. With a considerable imaginative effort (and taking into account the direction of Earth and the comet), you can understand why it only appears in the early morning sky now and will appear just after sunset later.
Figure 2 is the updated light curve and shows the decline in brightness. Since it has now passed its closest point to the Earth, we could expect it to dim – if it were not still approaching the Sun. The Sun will illuminate the comet more – and heat it, which may induce another outburst of brightness.
Or…it could fall apart and disappear. No guarantees, you understand. 😉
The observations are being “handed over” from southern hemisphere observers to those in the north. That gap near the 15th is a result. There were single observations each day, but so far from the norm that I did not bother to plot them.
Comet 2020 F8 is now visible with “eyes only” – but just barely. The eruption of dust and gas that has brightened the comet so quickly has abated and the debris has apparently dispersed. Part of that has become the tail that is blown away by the solar wind and gas. The tail has been divided and twisted by the Sun’s magnetic field. Below isyet another photo by Gerald Rhemann @ Farm Tivoli, Namibia on May 4, 2020.
This is when the comet was at about magnitude 5.3. It is in fact a montage of five images. As of this writing, 2020 F8 is showing at magnitude 5.8. You will recognize the graph below as my calculation of brightness change due to total distance (Sun/Comet/Earth) with the average daily observed magnitude.
Below is an updated “light curve” that shows the distance-based brightness calculation with the daily average observations. The red dotted lines show the dates when the comet will be closest to the Earth (Perigee) an closest to the Sun (Perihelion). The green points show the combined effect on brightness due to the Sun/Comet/Earth distance.
The Comet has undergone three eruptions of brightness. The first was the eruption of Hydrogen (it is thought) that made the comet detectable in the first place. That part is not plotted. The next was around April 19th. That one complicated my rotation calculations. The third was the recent that peaked on May 31st.
2020 F8 is crossing into the Northern Hemisphere and I will attempt to spot it with binoculars or a telescope. If I locate it I will make sky charts for you readers. Orbit diagram below.
No doubt you are wondering what will be next. There could be another eruption. Comets are composed of ice and rocks. The ice can be any light elements or compounds like CO2 or water – all with differing points of sublimation (like evaporation, but straight from solid to gas). As those ices vaporize, dust and rocks are released.
Or, the comet could break apart and fade from view – like 2019 Y4 did recently.
Or, anything in between
That’s just the way comets are. 😉
Let me share a reader’s question:
Good article. Have you tried to see the comet yourself, or is beyond amateurs ability to view it?
Thanks, (Road Trip Interest Group Member)
Dear Road Trip Interest Group Member,
The comet (2020 F8) is just now coming in to a part of the sky where it will be visible in the Northern Hemisphere. It will be near the square of Pegasus in the early morning. It is low on the Eastern horizon at 5 AM now but the Sun rises soon after. I have not yet seen it for two reasons:
1. The City of Houston is East of where I am and drowning out the sky with city-glare.
2. The weather is persistently cloudy.
I have two viewing location in mind out near the George Observatory. The skies out there are darker because the neighbors all practice downward directed lighting – probably by state law since the Observatory is on state property.
If I can get a clear morning, I will drive out and have a look in the next few days. I will attach a finder chart(from Sky and Telescope Website )and include same in the next update. You can use that (which shows you the position relative to the constellations) and the phone app called Heavens-Above (to find where to look for the constellations at any moment) to find the comet.
I won’t encourage others until I – myself – can catch a glimpse.
Another Near Earth Object encounter. This time with a unique announcement:
Notice that 2020 JJ has an anomalous distance of encounter of zero AU. It is rounded off, of course. The managers of this source will be contacted to encourage more decimal places! By other sources, I find the “miss” distance to be about 16,200 miles which is indeed less than 0.1 Lunar Distances.
This, again is worthy of a more detailed diagram with a better picture of the Earth (Thanks, NASA!).
The approaching asteroid did not pass across the celestial equator – where all the geosynchronous communication satellites are – but further to the South.
The JPL Small Body Database Browser, which is also the source for the “circle and arrows” diagrams you have seen on these pages, has undoubtedly given us a more accurate figure. However, it does have some limitations, which are clearly explained in the website:
“This orbit viewer was implemented using two-body methods, and hence should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstances.”
The alert readers (most of you) will point out that “planetary encounter circumstances” is exactly what I am talking about. That statement means that when asteroids get close to a planet, their mutual gravity has a significant effect that is not calculated in this utility. So, that 16,200 miss distance is not keenly accurate and almost certainly too large. Not only that, but it also means that the orbit after the near encounter will have been altered. It will need to be recalculated and replaced in the database.
JPL has a utility for that, called the “Horizons system” and NASA has an organization to keep track of these things (and studies methods to avoid collisions) called the Planetary Defense Coordination Office. That said, rocks this small (about 13 feet across) are not easily detected far in advance. They are also less destructive should they fall to Earth. This one was small compared to the Chelyabinskmeteor.
Comet 2020 F8 is now visible with “eyes only”. But not from the Northern Hemisphere. I hasten to explain that the “crosshairs” appearing (below) on the brighter stars are artifacts of the telescope construction – diffractions caused by the mounting bracket of the secondary mirror.
This is when the comet was at about magnitude 6.3. As of this writing, 2020 F8 is showing at magnitude 5.3. You will recognize the graph below as my calculation of brightness change due to total distance (Sun/Comet/Earth) with the average daily observed magnitude. I warned you that comets can’t be predicted with simple models like that and now you see what I meant.
Again, the differences are due to eruptions of gas and dust, making a much more reflective target. The comet now qualifies for “eyes only” visibility. It is still something for which you would need to take a trip outside your sophisticated urban environment. But don’t even bother because – except for my readers in the Southern Hemisphere – it is still below the southern horizon. I am working on some sky charts for Lima, Peru. But that still requires a road trip to a dark sky. There may be something for you city dwellers later.
Update May 5: In Lima, the comet is in the Eastern sky just before dawn (unfortunately looking right across the well-lit city) at about 25 degrees altitude. The sun will be rising soon so here is the standard warning: Do not look at or near the Sun with binoculars or a telescope! Blindness may result.
There is also a meteor shower this morning, coming out of the West East and streaking across toward the city ocean.* Also, look for Mars, Jupiter and Saturn together in the Southeast. There are conflicting weather reports. One says mostly clear. If that works, “Sigrid, te quito la bruma Limeña!”. Otherwise – same as usual.
Use the reply window below for questions. If you don’t see the reply window, click on the title at the top of the article to make it appear below.
In 1979, Skylab – America’s first space station – was falling out of orbit and my sister called me – her space nerd brother – to worry about this thing that she feared would fall on her new baby. I tried to explain that the Earth is so big and the Skylab so small (relatively speaking) that the chances were nil that any person on Earth would be anywhere near where it fell.
I went on to point out that there are natural meteorites that fall to Earth constantly and they could amount to the equivalent of thousands of Skylabs every year. She never worried about those!
After that, she was not just worried – more like terrified!
I have since learned to advise people that they are more likely to be hit by a train, bitten by a shark and struck by lightning – all at the same time – than to be struck by anything falling from the sky. There is exactly one case of a person being hit by a meteorite. The lady was badly bruised, but not fatally.
I told you that to blunt the effect of telling you the following:
Another Near Earth Object passed by the Earth on April 28th, 2020. I have checked a couple of reliable sources and I can tell you that the nearest it came was about 29 thousand miles. And that sounds like a lot, since the earth itself is only about 8000 miles in diameter,
However, the NEO does come into our “territory” since we have satellites orbiting the Earth. You might think that satellites are only hundreds of miles above the Earth and that is where you are mistaken. I decided that those little diagrams with circles and arrows are insufficient for this one. Please see the diagram in Figure 1 for details.
As you see, the NEO this week is close enough to be of definite interest. However, it passed to the South of Earth – nowhere near the “belt” of geosynchronous satellites over the equator and over twice as far as the “cloud” of GPS satellites. And, of course nowhere near the Space Station.
The asteroid is about 60 feet across. Satellites are flimsy aluminum gadgets and would crumble before the NEO. But Space is big and satellites are small.
Another Near Earth Asteroid has zoomed by while no one was looking on April 22nd. It may surprise the readers to learn that these things are so common that I only consider the ones that pass as close as the Moon to be of interest. This one was at 0.4 Lunar Distances or about 95,542 miles.
The culprit is 2020 HF5 – a small rock, as asteroids go – that is only 52 feet across. These encounters are listed at https://spaceweather.com/ – just scroll down a bit to find a table.
The rock in question is very much is roughly the same size as an asteroid that exploded over Челябинске in Russia on my 58th birthday. (Feb 15, 2013) . The heat of re-entry, combined with the tremendous air pressure of its hyper-sonic trajectory caused it to explode at 12 to 15 miles above the surface.
There was a Russian teacher – Yulia Karbysheva – about my age who, like me, had been trained in Civil Defense exercises in elementary school. They taught us what to do in a nuclear attack. When the meteor lit up the sky, she had her students hide under the desks – as she (and I) had been trained to do. When the asteroid exploded and the shock wave arrived, it shattered all the windows and sent shards of glass over the desks – with the students safely beneath same. After almost a half century, that training finally paid off – for the students. Unfortunately, she was so concerned with the fourth-graders that she remained standing and was seriously injured. In all, about 112 people were hospitalized, mostly cuts from flying glass. There were some cases of flash blindness and ultraviolet burns. Don’t look at the flash! I learned that instinctively as a welder.
Our more recent visitor was similar in size, but with only about 1/2 the relative velocity as that meteor and would have about the one fourth the explosive potential. About 117 kilotons – 9 Hiroshima bombs equivalent.
What’s that? Oh…it’s the town’s name – “Chelyabinsk”.
Comet C/2019 Y4 has broken into pieces that are scattering and fading in brightness despite being closer to the Sun and Earth. I will include a Hubble Space Telescope photo here:
It will not be a “Great Comet”.
Comet 2020 F8 is now visible in a small telescope or binoculars and will probably be – at the very least – visible without such aids very soon. Below is a recent image from Universetoday.com
But, you won’t see it now because it is in the Southern sky and is being observed from New Zealand and Australia and other points in the Southern Hemisphere. It will arc over the Northern sky soon. In the previous update, I graphed the brightness to be expected due to distance alone. You can take this as a prediction of 6.3 as the peak magnitude. But, we all know that is almost certainly wrong – because we don’t have enough information. I have added the daily average observed magnitude (orange dots) in Figure 3, below.
The observations are, indeed following the prediction – somewhat. The differences can be attributed to eruptions of gas and dust, but also to the comet’s rotation. In college, I learned a method of analyzing sparsely collected observations to detect periodic changes. It goes something like this:
We cannot monitor objects in telescopes with enough resolution in time to detect a periodic variation along one cycle of rotation or pulsation. However, since we expect the oscillations to be more-or-less uniform over time, we can collect points from different oscillations, over an extended period and graph them as a single cycle.
But this requires that we know the period of the cycle. Astronomers have been historically starved for data and come up with some desperate solutions. In this case, we can try every possible period of oscillation, put the resulting data on graphs, and pick the one that looks like we think it should for a single cycle. In the olden days, this laborious amount of calculation could be out-sourced to graduate students or assigned as homework for undergraduates. If you want to imagine doing such calculations “by hand” go ahead. Me, I don’t have to use imagination because I did it – a few times.
The observations have a time associated with them. We establish a “zero point” and calculate a time value for each magnitude. Then each observation time is divided by the trial period. That leaves a fraction that is the position in the single “combined” oscillation we intend to graph. Then we change the trial period and repeat – a lot. Below is a “perfect” theoretical graph to be kept in mind while looking through all the trial graphs.
And before you ask “why didn’t you use a computer at UT in 1976, Steve?”, I should tell you that in the 70’s, a computer with a tiny fraction of your telephone’s capability was a huge machine in a large room attended by several “operators” who scheduled calculations on that hideously expensive device for days in advance. The data and the programs (apps) were read in on punch cards and the output was printed on green-and-white paper. What “memory“ was available held the simple operating system and your bare-bones program and input data for the time it took to complete the “job”. Then your data and program were immediately replaced with the next job. No time was available for undergraduate homework.
Now we have Excel spreadsheets instead of graduate students or IBM 360 “mainframes”. The needed calculations and a graph on the screen for one trial period is accomplished in a split second with a single click. The graph below was selected as “plausible” after 291 clicks. This indicates a period of four hours, 51 minutes.
The points plotted come from 74 observations over 14 days. I should mention that these were not the “raw observations” but were adjusted to remove the distance-related brightening (that green curve in Figure 3).
This was the “best-looking” result, but there were other “candidates” at six hours, seven minutes and at eight hours, 10 minutes. Nothing even close to “plausible” was found after that, up to and including a 30-hour trial period.
So, if you hear later that the comet has been determined to be rotating at a period like any of those – remember that you heard it here first! Otherwise, well I was wrong. Science has a long history of being wrong, so that’s OK. The important part is to not insist on your theory in the face of contrary evidence and accept that you were wrong. (Are you listening, Global Warming Devotees?) 😉
Use the reply window below for questions. If you don’t see the reply window, click on the title at the top of the page to make it appear below.
Comets are particularly unpredictable phenomena. The current case is C/2019 Y4, which has apparently broken up into at least three pieces – which at last sight were drifting away from each other. It’s visual magnitude has gone from a sudden brightening to 7.8, but then dropped to 8.8 after the break-up and shows no sign of recovering. This, despite the fact that is nearer to the Sun and the Earth than before. It is not visible to the naked eye, even in clear, dark skies. You might find it with a medium amateur telescope.
There is another, more recently discovered comet in the Solar System called C/2020 F8. It, too has undergone a sudden brightening, but is still a bit to dim to see – even in that theoretical dark, clear sky. Since it is in the Southern sky right now, you could not see it anyway.
I have made some diagrams of both comets with the JPL Small-Body Database Browser and added some explanatory text. The planets are all in the same orientations and positions in both.
“So, what next? “, you may ask. Well, as these comets approach the Earth and Sun – at different rates since the Earth and Sun are 1 AU apart – they will brighten. We cam predict the change due to distance alone. Below is a graph of distances predicted over time for C/2019 Y4 (refer to figure 1). The data are from the aforementioned JPL Small-Body Database Browser The graph was generated by your humble narrator in Excel.
The increase of brightness to be expected (if nothing about the comet itself changes) can be predicted by the total distance involved. Keep in mind that light spreads out such that a reduction of ½ the distance will result in 4 times the brightness. Remember that on this stellar Magnitude scale a reduction of 1 magnitude is the equivalent of more than a doubling (about 2.5 times) in brightness. I don’t make these rules, OK?
This needs some calibration since it calculates only differences. That calibration is taken from a recent observation as noted on the graph (also Excel) that follows.
The conclusion is that the peak brightness will be still below naked-eye visibility – around May 28th. Having said that, you will remember that this exercise assumes that the comet itself will not change. But that’s silly! We just saw it increase suddenly in brightness (far in excess of expectation) and then dim again! That was from eruptions of vaporizing ices, that apparently broke this comet into pieces. I told you these things are unpredictable, did I not?
So, why do this calculation of brightness due to proximity? Because it is all we can do! Keep that in mind the next time someone tells you they can predict the climate. 😉
The same sort of calculation can be done for this Johnie-come-lately comet that just showed up. I will skip all the intermediate explanations and go straight to the prediction chart.
You see that the new comet is likely to be brighter than poor old C/2019 Y4. It will probably become magnitude 6.3 – bright enough to see without binoculars or a telescope – out of city lights, in a dark clear sky -but just barely!
And, just now we have news of an observation from the Comet Observation Database . For April 19th (late in the day) the brightness was measured at magnitude 6.8. You can see the red cross on the graph. That is, however, one of four observations on that day – the other three were all magnitude 7.5. To change the whole prediction on a single observation would not be reasonable, so I will wait to do so until a few more observations are made. Did I mention that these things are unpredictable?
You may ask, “Steve, why did you choose such an uncertain occupation?”
I did not choose Astronomy. Astronomy chose me. It is actually a hobby because, while I wanted to be Carl Sagan, I found out they already had one. So, I wound up looking down through the Earth instead, because someone would pay me for that. Now I have nothing better to do. Well, I have other things to do – yes. But, who wants to mow the yard again?
Before you write me to say, “Why didn’t you photograph the comet, Steve?” – this image is from a telescope with 8 times the light-gathering power of mine. Add to that, the fact that they took 120 second exposures…twenty of them. To do that they had to track the comet as it moved through the background stars that make the streaks you see. Their telescope is guided by sophisticated computerized servos, while my ‘scope is on a mount made from a plywood box and is guided by “pushing with your hand”. Then they stacked those 20 photos together to make this image. These are professional Astronomers in a Swiss observatory while I am just a guy in a driveway in Houston.
I warn you that this is what Literature students call “a bear”! But my preliminary read tells me that the comet fragmentation could pre-sage a disappearance or it may be associated with sudden eruptions of activity that result in a brightening. A long-winded way of saying “Anything could happen”, this is. 😉
There are many reasons a comet might break up but the main two in this case (in my humble opinion) are probably thermal stress and gaseous eruptions of sub-surface ice bodies.
Update: A recently discovered comet in the Southern sky has undergone an “outburst” and is already as bright as Y4. It is not yet in the databases, so no cool diagrams, yet. Details in the next post. | 0.873307 | 3.535157 |
Shannon Stirone | Longreads | January 2019 | 37 minutes (9,047 words)
At 9,200 feet, there is 20 percent less oxygen than at sea level, enough to take all the air from my lungs after just three steps. But it didn’t stop Mike Brown and Konstantin Batygin from hastily shuffling into the lobby of Hale Pōhaku to check the weather forecast. They stared at the TV monitor, craning their necks, suitcases in one hand, fingers pointing to the screens with the other. “It’s Sunday,” Brown said, “there’s no new forecast until tomorrow. Damn.” We were at base camp on the dormant volcano Mauna Kea, on the big Island of Hawaii. The pair were here to use one of the most powerful telescopes in the world, called Subaru. Tomorrow night, December 3, marked the start of their sixth observing run and their next attempt to find the biggest missing object in our solar system, called — for the moment — Planet Nine.
The Onizuka Center for International Astronomy, located at Hale Pōhaku, looked exactly as you might imagine a Hawaiian dormitory built in the early 1980s would. Each table was covered in an azure nylon tablecloth with salt and pepper shakers. The backs of the chairs depicted scenes from around the island: Mauna Kea, palm trees, snow-capped volcanoes, sandy beaches. It was 7 p.m. when we arrived, and most everyone who lived and worked at these dorms was asleep. (In astronomers’ quarters, most people sleep during the day or wake at odd hours of the night to go to work.) The cafeteria was empty. “Oh my god, they have Pop-Tarts! They haven’t had Pop-Tarts here for ten years!” said Brown as he unwrapped the shiny foil package to put one in the toaster. This was a good sign — Pop-Tarts are the nonsuperstitious tradition of astronomical observing — and also dinner.
We would have a snack and go over the game plan for tomorrow night. Brown and Batygin sat down at one of the round tables, laptops out. Brown, a professor of planetary astronomy at the California Institute of Technology in Pasadena, felt optimistic. Batygin, a theoretical astrophysicist and professor of Planetary Sciences at Caltech, guessed it would take them 10 more years of observing. This is their dynamic. If the planet they’re looking for exists, it is likely six times the mass of Earth, with an atmosphere made of hydrogen and helium covering its rock-and-ice core. What makes it hard to find is its likely location: at least 400 times further away from the sun than our own planet, and 15 to 20 times further out than Pluto. As a theorist Batygin feels that he’s already mathematically proven its existence. But it’s generally accepted that for a planet to be considered discovered in the field of astronomy, the theory must also be accompanied by a photograph. This is where the Subaru telescope comes in. They know that Planet Nine is somewhere in between the constellation Orion and Taurus, but that’s about as exact as they can get, and they’ll need good weather to locate it. Right now the last predicted forecast showed fog. Even at six times the mass of earth, Planet Nine is so far away that it would appear as a barely visible point of light, even through the lens of the most powerful telescope they could get their hands on.
Brown felt optimistic. Batygin guessed it would take them 10 more years of observing.
Though it was only 7 p.m. it was time to settle in for the night. We took a series of wooden bridges faintly illuminated with reddish light to the dorms. (Red light does not affect night vision). Because of the reduced oxygen, the carry-on-size suitcase I had with me might as well have been the dead body of a weightlifter. We stopped to take a break to catch our breath, and looked up. There is hardly any light at Hale Pōhaku after sundown. An hour away from Kona or Hilo, there are no streetlights, no real building lights, no car lights, it’s just dark. What can be easy to forget for anyone that lives in or around a city, is that the night sky is not black, but gray. We are drowning ourselves with so much light that we don’t realize how much light the darkness really contains. Wherever Planet Nine is–if Planet Nine even is–its surface is touched by the sun’s light just like our planet, and as a result some of it is illuminated. The physical particles of light that travel the billions of miles between both bodies also move through space. Their journey begins at the sun, stirring around deep inside the core for thousands of years, moving eventually to the surface where they are finally released. This newly exposed light travels out into the cosmos and to distant unknown worlds. This is why we came, we had to escape the light in order to find it.
We stood there for a moment and as our eyes adjusted, the galaxy turned on. Clusters of stars became the entire sky. Each speck of light had traveled its own distance; traversed its path through the dark void of space, some from the time of the earliest human civilizations, light that left at the dawn of the invention of agriculture and cities, at the time this mountain was last covered in lava. Mike pointed over the hills to a hazy cone of yellow light that shot up like a triangle from the Earth, explaining it was a rare astronomical phenomenon some people wait their whole lives to see: “That is the zodiacal light. It is the sunlight reflecting off of the dust that’s floating in the asteroid belt. This is the best I’ve ever seen it. Wow.” Across the sky to the right was the arm of the Milky Way galaxy. It was as though a painter had dipped their brush in starlight and clouds and smeared it ever so carefully across the universe.
With dozens of astronomical discoveries to his name, 53-year-old Mike Brown has the distinction of having found more dwarf planets than any other human in history. Dwarf planets are hundreds of times smaller than Earth, so detecting them when they orbit so far out is extremely tricky. (Pluto, for example, is 500 times less massive than our planet.) In 2001, Brown discovered two dwarf planets called 2001 YH140 and 2001 YJ140. Two years later, using the Palomar Observatory in the mountains outside of San Diego, he caught some light from a distant Kuiper Belt object that no one had ever seen before. It was three times farther away than Pluto, and smaller too. The object was so distant that the view of the sun from its surface could be blotted out with the tip of a pen if held at arm’s length. He named it Sedna. Then, in 2005, he found another object — more massive but just a bit smaller than Pluto. He would later name this dwarf planet Eris after the Greek goddess of strife and discord, and oh how much strife this thing caused.
The International Astronomical Union decided that if there were other “Pluto-size” objects out there then maybe the title “planet” was not a good one for Pluto. Brown became known as the “Pluto Killer” — though mostly by way of his adopted Twitter handle. (Brown said he actually finds Pluto quite interesting, but only admits it under his breath so as not to ruin his bad boy reputation.)
Years later, two astronomers, Scott Sheppard and Chad Trujillo, noticed that a dozen distant Kuiper Belt objects appeared as though they were all operating in concert in the Unknown Regions of space, sharing certain orbital characteristics. Brown was intrigued by their 2014 paper, but thought something wasn’t quite right with their hypothesis. That same year Batygin, his former student, was working down the hall. Brown asked Batygin if he wouldn’t mind looking at the data with him. Though Brown briefly wondered about the possibility of a planet, he and Batygin quickly pivoted to the idea that enough collective gravity might have put the objects in this orbit. “We tried to examine every hypothesis other than a planet and took it very seriously,” said Batygin. “This is not like you come in one day and think a little bit about it then you’re done. It takes a lot of time. I made almost complete models for every single other hypothesis before we allowed ourselves to consider the planetary explanation. You have to rule out every other possibility first.”
They are not the first to be puzzled by oddities in the outer solar system. Not long after the discovery of Uranus in the 18th century, astronomers observed that the planet’s orbit wasn’t moving at the rate that predictions said it should. The planet appeared to randomly accelerate in its orbit, then decelerate. In 1846, French astronomer Urbain Le Verrier suggested this was the result of another large planet orbiting beyond Uranus that had not yet been found. As in all astronomical observation, an image must be taken in order to consider an object discovered, and no one had ever seen a planet beyond Uranus. Not only did Le Verrier suggest a planet as the cause, he predicted what he thought to be the location. As an expert in mathematics and celestial mechanics, Le Verrier was confident in his claim, so much so that he wrote to German astronomer Johann Galle who was working at the Berlin Observatory at the time, and told him to look at a specific point in the sky. Galle opened the letter on September 23, 1846 and right away he and his assistant, fellow astronomer Heinrich Louis d’Arrest, took to the telescope. Using Le Verrier’s coordinates along with a recently updated star chart, they were able to finally compare this moving object against the tapestry of unmoving stars — they found Neptune less than one hour later.
Brown and Batygin faced a version of the same question Le Verrier asked of himself 169 years ago: What is happening beyond where we can see?
Planet Nine’s Le Verrier is Batygin, who, as 2014 turned into 2015, took to every blackboard and computer simulation he had at his disposal to think over Sheppard and Trujillo’s hypothesis using math that only few people in the world understand. He spent more than a year, along with Brown, trying to figure out why these objects were clustered together in space.
Before Planet Nine, Batygin knew little about observing and Brown didn’t know much about theory, but Planet Nine cannot be found without both. If anyone knew the theory behind how planetary bodies behaved in space, it was Batygin. By 2014, he was a renowned theoretical astrophysicist, and the following year, was named among Forbes 30 Under 30. He had first distinguished himself at the age of 22, when he proved mathematically that our solar system was unstable — a problem Isaac Newton himself had hoped to solve — and that eventually (a few billion years from now) Mercury could either fall into the sun or collide with Venus, which would result in Mars’s ejection from the solar system. Now Brown and Batygin faced a version of the same question Le Verrier asked of himself 169 years ago: What is happening beyond where we can see?
Part of their job was first to try to find a solution less extreme— like a passing star or a galactic anomaly — than a giant undiscovered planet far off in the depths of the solar system, because, a hidden planet? That was absurd. But finally, in the spring of 2015, they both agreed, the only other explanation for this clustering of Kuiper Belt objects was indeed a planet — a big one. On January 20, 2016, they made the announcement proposing that our solar system has a giant planet orbiting far away from everything else. They told all astronomers with access to the most powerful telescopes to go and find it. They wanted to find it too.
Hale Pōhaku. Monday, December 3, 2018. 2:30 a.m.
We met in the cafeteria. It is suggested that all people observing on the summit spend several hours at base camp to adjust to the altitude to prevent dizziness, slurred speech, and death. The summit of the mountain is 13,796 feet and has only 60 percent of the oxygen found at sea level. We were up literally before dawn to begin adjusting to the observing schedule that would now be:
10:30 p.m.: Wake up and eat (Breakfast? Dinner?)
11 p.m.: Leave for the telescope
Midnight to 6 a.m.: Observe
Groggy and grunting, both Brown and Batygin dragged their feet down the stairs of the dorm’s living room. They do their thinking at base camp and their struggling at the summit. (According to Brown, “Thinking at 14,000 feet is not a good idea.”) Over Froot Loops and Cheerios, they carefully ran over their own computer simulations with updated search parameters, making inside jokes to each other and giggling. They sometimes debate the location of the planet for hours at a time. At this particular moment, Brown was not only certain that Planet Nine’s semimajor axis — that is the mean distance of the sun along its orbit — was 310, but he was just about willing to stake his life on it. Batygin disagreed: “The reason that we’re here right now is because it might not be at 310, it might be at 400.” Brown said, looking at me, “Like I said to Konstantin, if we don’t get any data, I’m done with this crap, I’m out.”
“Yeah, but you say that every time,” said Batygin.
To me, “He reminds me that I say that every time.”
“It’s not like you’re doing any actual work.”
“I’m actually doing a lot. It actually takes me a long time.”
It went on like this. At issue was how many data points they were using in their simulations. Brown had two, but Batygin thought this was wrong, and felt that Brown’s room for error (aka, “the wall”) was too small. While they consider themselves “regular Caltech nerds,” this was also reference to Game of Thrones, since all the distant Kuiper Belt objects are cold and living “beyond the wall.” Quick, someone hold the door for this fight:
“You know where else it could be?” said Batygin. “800 AU.”
“What is the error bar wall? If you try to fit the wall—”
“I don’t try to fit the wall.”
“If you did—”
“I don’t try to fit the wall. You try to fit the wall.”
“If you tried to fit the wall.”
This type of friendly, extremely nerdy, almost-marital bickering is typical of Brown and Batygin, and maybe even expected from two guys who have spent the past few years recreating the solar system together. They each run simulations that begin at some point in the past 4 billion years. Since we can’t go back in time to see what could have placed Planet Nine where it is or to actually find out where it is, they each recreate the growth of the planets over time. Their simulations can take from three days to three months to run, and they start them after all of the large planets have formed, some 3 to 4 billion years ago. In 2018 alone they ran more than 2,000 Planet Nine parameters with different masses and locations, averaging 38 new solar systems a week. As a result, the slight variations in data are what keep Brown and Batygin bickering and in check.
In order to find their planet, they need to use one of the most powerful telescopes on Earth to capture the light coming from such a great distance. The Subaru Telescope, which was first named the Japanese National Large Telescope, is owned and operated by the National Astronomical Observatory of Japan. Among telescopes its size, Subaru has the largest field of view and magnification available of any Earth-based telescope, which is why this is their only hope of finding the planet. The special camera on Subaru, the Hyper Suprime-Cam, is the real trick. At 10 feet high and 870 megapixels, it is able to focus down to the width of a human hair. The next day, they would try after an entire year without any usable data. This is the search for Planet Nine.
At 4 p.m., we went to bed.
Hale Pōhaku. Monday, December 3, 2018 (still). 11:15 p.m.
Brown speedwalked into the cafeteria, threw his black messenger bag onto one of the chairs of the round table, and with wide eyes whisper-yelled, “HOW IS THE WEATHER AT THE SUMMIT!?” The 30-second walk from the dorms to the common building was not great. It was raining. There was fog. Batygin and Surhud More, an astronomer and collaborator from the Japanese science team were prepared with an answer. “Only 10 percent humidity at the summit,” More replied trying to settle Brown’s nerves. Over the past three years Brown and Batygin have made five trips to the Subaru telescope on Mauna Kea. Of the 18 and a half days they have spent observing, only eight and a half nights have produced useful data. This was no time for fog, almost a four letter word but not quite.
The parking lot at Hale Pōhaku is paved, while most of the road to the summit is not. A sign at the edge of the parking lot reminds visitors to stop and switch into four-wheel drive for the 25-minute drive up the mountain. This delineation between paved road and unpaved road is a reminder that the journey is dangerous, it takes effort, caution. We must have patience, we must move slowly and remember this is a temporary visit. Our oxygen is about to be reduced by 40 percent, and we will see fewer stars because there is less oxygen in our blood to help our eyes focus. We drove at approximately four miles per hour with just the power of our headlights to prevent us from driving one foot to the right and plummeting down the mountain to our death.
I have been to the tops of mountains, but none like the summit of Mauna Kea. It is not just its meaning and value to the Hawaiian people that might influence the feeling there. When I stepped out of the car, I was grabbed by the wind, encircled, wrapped, and marked — human foreigner. It was cold, below freezing, and it was dark. Nearly the darkest part of any night is around midnight, but after my eyes adjusted, somehow there was a little light. Our bodies’ survival mechanisms kick in, pupils are automatically dilated, opened up as wide as possible. In darkness like this we are vulnerable and our animal brains know it. It is the same feeling I imagine I would have if suddenly placed on Mars. This land is not for humans. There is barely any oxygen, there is almost no water in the air. There is no life around, no plants, no birds, nothing — these rocks are the beginning and end of everything. Just enough light from the stars overhead reflected off the bright white paint of the domes. There were no smells. The wind hit me again like a giant palm to my body. Even the sound of the dirt and stone below my shoe was foreign, like stepping on glass but not quite. It was a sound I had never heard. I was not where I had been. I felt reverent and intrusive, almost disoriented. With each crunch of rock under my shoe I was reminded that this is old land. Original land. Volcanoes are monoliths formed from fire and water and air — a million-year-old history cracked and ached below my feet.
I have been to the tops of mountains, but none like the summit of Mauna Kea. I was grabbed by the wind, encircled, wrapped, and marked — human foreigner.
The mountain last saw fire from its peak 4,500 years ago. It was towards the end of the Bronze Age. Humans began to use the plow. The world’s population was only 25 million, and writing would soon begin in Sumeria and Egypt. I felt suddenly as though I had intruded on the past. Standing there being nearly blown over by the wind and pricked with the cold air felt like being in what in Celtic culture they call a “thin place.” The saying goes that the distance between heaven and earth is only three feet apart, but in a thin place, that distance collapses. Oftentimes it is used to describe the moment when a person is about to take their last breath, or right before they take their first. Where heaven meets the Earth — this is Mauna Kea.
For Hawaiians this mountain is sacred. The highest peak in all the Hawaiian islands, it is what they call a “wao akua,” which translates to “home of the gods.” The summit of the Mauna, or mountain, is the place where the gods live. Mauna Kea, in English, translates to “white mountain,” a nod to the snow-capped peaks, but the full name is Mauna a Wakea, or god of the sky. Traditionally, only religious leaders and Hawaiian royalty were allowed to travel to the top, the place for shrines, burials, and ceremonies. The summit has never been just for anyone — only those with the right could ascend the mountain and be in the presence of the gods. For this reason the use of the summit as a place for large telescopes and observing has been highly contested by the Native Hawaiian community, considering construction on the mountain as a desecration of their most sacred land. Now “science city” dominates it. Whether you believe in god, or the gods, or heaven or hell, or nothing at all, the summit of this ancient mountain and this sacred place felt as though the distance between the unreachable stars and the top of the Earth had collapsed and for as long as we were there, we existed in the thin place.
Mauna Kea, Subaru Observing Control Room. Tuesday, December 4, 2018. Midnight.
At 14,000 feet Brown’s fears of fog no longer mattered. “I can’t believe it’s so clear!” he said. After taking the elevator up to the third floor where the observing room is, they both nearly ran in, set down their stuff, and immediately got to work. Brown had his laptop open before his jacket was off and Batygin was already on a computer typing in a code that would deliver images to him during the night. They needed to get the telescope calibrated and focused on the patch of sky they would be observing. An engineer and support observer were each at their own computers next to the main screen, which had a countdown clock that read Time to Completion. In this instance, they were calibrating the telescope. It counted down: 136, 135, 134, 133. One computer screen hung from the top of the room that showed multiple views of various control rooms, one of which was in Tokyo where, every morning, they greet the Japanese team. Brown and Batygin had the last half of the night, midnight to 6 a.m., for observing. They would observe with half nights for four days, and the last three they would get the run of the telescope from sundown to sunrise.
The countdown reached zero, and the sound of a cuckoo clock went off. This sound marked the end of calibration. They were ready to observe. It also “cuckcooed!” every time an exposure finished. Their plan was to capture about 100 fields on every half night, weather permitting. The fields functioned like circles on a map, marking the total viewing area of the telescope: around 9 full moons worth. Every exposure lasted 60 seconds, and with each one came a new image of the sky. Batygin’s job was to look at random stars in the images to measure their width. The more circular the stars appeared in the camera, the better the seeing was. If he clicked on a star and it appeared jagged, it meant there was upper atmospheric turbulence; if it was slightly oval, the telescope was out of focus; if it appeared washed out, it meant that there was fog. All of this messed with their ability to capture a precise point of light. That’s a problem when your entire task is to capture a precise point of light. The windier the conditions, the more the stars’ light would smear across what is called an arc second. And to find Planet Nine they needed all arc second readings to be under 2.0, ideally under 1.0. Planet Nine likely travels — at the most — two arc seconds a night, so if the winds are too high in the upper atmosphere, so much that it’s smearing the stars into two or three arc seconds wide, the data become unusable. Think of zero arc seconds as being a perfect point in the sky; as the arc seconds creep up, the light gets blurrier, smearing out a little to the sides and blocking whatever possible planet might be hiding behind.
Brown named each field with four numbers in a spreadsheet and kept a log of stars’ arc seconds that Batygin randomly clicked on in that field. If the “seeing” was bad, Brown would make a note in the log and they would have to go back and reimage that field. This is where observing becomes less romantic and more like a creepy radio number station. They would wait to take about 10 images, and Batygin would then read off the numbers in batches: “4817 is 1.4. 4918 is 0.9. 4919 is 1.05. 5319 is 1.1. 5318 is 1.4,” and so on.
‘We have algorithms? Uh, no. I have spent most of my life writing these programs. This is not stuff you can get at the App Store.’
Minutes after starting up the cameras, they were collecting data. The weather was holding so spirits were high. Maybe a bit too high? Up at 14,000 feet one can get what is called an “altitude high,” which happens when the brain is deprived of oxygen. Some people get cranky, some get sleepy and mellow. Batygin gets happy. More, even, than normal. Every time he comes up to the summit, he has to use oxygen so he knew he was due for some air. There was a first aid cabinet with personal oxygen tanks that you strap around your waist with a belt and pre-wrapped plastic nose inserts. It was 12:45 a.m. and Batygin had not yet plugged in.
He was in the thick of collecting star data and writing down the next set of numbers to read off to Brown when he opened an image of stars. The sensors on the camera, all 116 of them, collect so much of the sky that as soon as you start to zoom in on any photo, not only do you fill the screen with so many stars that it looks like TV static, but galaxies appear, asteroids, you name it. The screen becomes littered with space stuff. With a black-and-white image open, he pointed to the screen and said, “I think I found Planet Nine!” He was joking, but to Brown’s ears, he sounded way too happy. Brown jumped up out of his seat, grumbled “Oh man” under his breath, and walked to the first aid cabinet for a monitor to test Batygin’s oxygen. It was below 70. His lips had turned a little purple, and he was way too excited to be up at midnight and working. Brown was worried about him, but Batygin laughed it off, with a facetious dying message to his wife: “Just tell Olga I love her.” He unwrapped the plastic tubes that strap around your head and placed them inside his nose. “I’m about to get way less happy,” Batygin said, half disappointed, half warning us all. He flipped the switch on the oxygen tank, the batteries started up and he took in one long deep breath.
The control room had more than two dozen computer monitors, most of which have specific readouts: the temperature of the telescope mirror, precipitation, wind speed, etc. Above the computers was a shelf with five speakers that each trace back to a microphone placed on the telescope. Every time the camera’s shutter opened and closed it made a sound like Optimus Prime mid-transformation. The volume was up loud so that staff could walk to the break room for coffee and still hear the shutter open and close, which is does every 60 seconds, followed by a cuckoo to mark the successful download of the exposure. Open, 60 seconds, close, “cuckoo!”
Subaru collects a lot of light and from a large swath of the sky. As a result, every night the team’s data contained hundreds of asteroids and Kuiper Belt objects, many that have never been seen before. Under normal circumstances, these appearances would warrant follow up, and even excitement, but there is an urgency to this search. Brown and Batygin don’t have time to chase these things night after night, which is what is required to “discover” something. These objects are just light that is collected and discarded. As Batygin and More sorted through images, measuring the seeing in each field, discussing numbers and computer codes, a new image came through and they zoomed in. Against the blue of the computer screen, a massive spiral galaxy appeared. It had a wispy ghostlike body with long almost jellyfish-like tendrils that stretched around on itself. We leaned over to look at the picture and said, “Oh wow!” which warranted a quick half-joking reply from Brown: “Ugh, galaxies. Those are the worst.”
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The trouble with looking for one thing in the sky is that our galaxy is full of stars, 100 billion of them, most of which annoy Brown to no end. If Planet Nine exists, it is so faint and so far away that it can easily get overpowered by a regular show-hogging ham of a star. The absolute worst place to look for Planet Nine is into the plane of our galaxy where a lot of those stars live. By 2 a.m., another package of Pop-Tarts had been opened. The numbers were coming in over 1.4 — not great. Brown decided they should move the telescope and begin observing on the other side of the galactic plane. They sent the request to the telescope operators to calculate how long the slew would take. They told him that because of the time of night, to get around the plane of the galaxy would take 40 minutes. “Forty minutes!” Brown exclaimed, “Shit, shit, fuck, fuck.”
Forty minutes is a long time. I was told that it costs a dollar a second to use this telescope, and 40 minutes is a lot of observing time lost when you only have six hours in one night to find a planet. He decided they would wait a few more hours until the galactic plane had moved overhead, so the slew that would have taken 40 minutes would only take 10. They would keep observing with the 1.4s until the 4 a.m. slew.
By 4:30, the slew was complete, and the brightness of the galactic plane was out of the way. Brown asked Batygin to read out the numbers.
“Yep! 7715 is 0.8. 7516 is 1.0. 7515 is 0.7. 7518 is 0.8.” They continued coming in under 1, a relief. Joking in the room resumed. An observer asked Batygin how they process the data after they return to Caltech, to which he replied, “Well, we have these algorithms—”
Brown interjected: “We have algorithms? Uh, no. I have spent most of my life writing these programs. This is not stuff you can get at the App Store.”
“You should sell your algorithms on Google Play,” joked Batygin.
“Ninety-nine cents,” said Brown, with a slight roll of his eyes. “Give me more numbers!”
At 5:50, we heard another “cuckoo!”. The dome began to close and the team packed up the Pop-Tarts and gear. Despite the 1.4s, the night marked the first successful collection of data in more than a year. All anyone could talk about was breakfast. There wasn’t any coffee at the summit, and warm eggs, potatoes, sausage, and enough coffee to fill a bucket was all that anyone wanted.
The beauty of leaving the summit after 6 a.m. was that it took around 25 minutes to get back to base camp: just enough time to watch the sun come up. In just under a minute the dark gray of twilight was swept away. The air was grayish blue, the rocks I had felt under my shoes earlier were a burnt umber, small and light. On Mauna Kea, the sun does not just rise, it cracks the sky open with an almost blinding yellow that is quickly seized and destroyed by an even brighter orange. Every second new colors appeared as banded layers of horizontal clouds. What I once understood to be light blue was slightly more light blue. It met and danced with lavender that bled like watercolor into mauve, then a soft pink. As we left the parking lot and started to drive down the mountain, other telescopes appeared. They were everywhere. Suddenly white and glossy silver, their towering domes stood atop the reddish soil of the peaks. They were massive. As we drove, the car shook from side to side from the road, like being in a paper airplane played with by the wind. We passed the red mounds of ancient volcanic vents that stood there, markers of lost time. The clouds, like the whitish gray of an old cobblestone street lingered in the valley below, and suddenly the purple sky began to turn.
Hale Pōhaku. Tuesday, December 4, 2018.7:30 a.m.
The living room just outside the cafeteria had a Christmas tree and completed jigsaw puzzle that looked like it had been baking in the sunlight since the dorms opened in 1983. There were three couches and cozy green chairs and a fireplace with red and white stockings, hung mostly with care. Batygin spent the day back at the dorm, first trying to figure out if a passing star could have perturbed Planet Nine, placing it into its weird orbit. Brown sorted through data from other telescopes trying to — surprise — find Planet Nine. He has spent nearly every free moment in Hawaii combing through data from the ZTF instrument on Palomar’s Samuel Oschin Telescope, the same telescope he used to find the dwarf planets that made him as famous as an astronomer can reasonably expect to be. So far anyway. Lunch was served at 1 p.m., but it would be our dinner. We would go to sleep at 3:30 p.m. and wake up at 11 p.m. to go back to the telescope.
The guys had no idea if they would find Planet Nine that week, and Brown’s mood oscillated accordingly. After they got back to Caltech and received the data from the headquarters in Tokyo, they would rely in large part on machine learning to sort through the roughly 160,000 images they’d have. They would take their list of candidates and run it through the computer, and any that came up as possible Planet Nines, as many as 1,000 images, would then be looked in the old school way: by eye. They would be looking for a tiny speck of moving light. “If ever there were one barely crawling across the screen,” Brown told me, “it would be an ‘Oh shit, that’s it moment.”
This search was different from Brown’s previous endeavors. “For my entire career what I feel like what I have been doing is exploring the solar system,” he told me. “It never occurred to me that there was more primary exploration left to do. So finding Planet Nine is the grandest exploration that can be done of the solar system right now. I wouldn’t want to be doing anything else.”
“I agree with everything Mike said,” added Batygin.
“First time today!” Brown replied.
“Cherish it. It’s not going to happen again.”
Batygin feels confident that the planet is there. It is not just the evidence of these clustered objects, but after four years of simulations and doing calculations that look like they are in some alien language, he feels that his equations confirm that this is a large mass object that is shepherding these objects into place. Planet Nine is doing this. He wants to know that his math is right, and the detection of Planet Nine would do that: “There’s a different thrill here for me which is actually the thrill of refutation of confirmation. With theory it’s almost like it emerges out of nothing. And really it’s only in our heads, it’s not something that we have seen before. It is a pure outcome of imagination and there’s a thrilling magnetism to that because that imagination might be right. For me that is the most amazing thing, being guided only by mathematics.”
‘The correct analogy is that there’s this singular somewhere in the ocean and you don’t know where — there is only one giant white whale and you need to go kill it because it bit your leg off.’
“I’ve never worked on a problem that’s taken this long,” Brown told me. “It is really difficult to sustain this effort for one singular purpose. It’s hard. Sometimes I think let’s just find it so I can do something else I’m tired of this stupid planet. That’s the hardest part for me other than the frustration of not knowing where to find it.” Batygin agreed. “There have been a few times in the last few years that I actually stopped working on Planet Nine,” he said. “I had moments where I felt like I was getting over-obsessed with this and kind of going in circles so I would make the conscious effort, for the next two months I’m not going to think about Planet Nine, how about magnetic fields of young giant planets or the Schrodinger equation? I took my mind off of things so I could come back with renewed enthusiasm.”
“There is only one way to win this survey, and that is to actually find it.” Brown continued. “The correct analogy is that there’s this singular somewhere in the ocean and you don’t know where — there is only one giant white whale and you need to go kill it because it bit your leg off. Sadly, I think that’s the right analogy.”
Hale Pōhaku. Tuesday, December 4, 2018. 11:15 p.m.
Every morning Brown selects a playlist for the drive to the summit. It is usually five songs long, which is about how long it takes to get to the telescope. Brown connected his phone as Batygin, who was driving, switched the car into four-wheel drive and Cake’s 1996 hit “The Distance” began playing. We climbed the rest of the way up the mountain listening to Eminem, Kanye West, Lynyrd Skynyrd (Brown is from Alabama), and Jon Bon Jovi (they attempted the high notes).
When we arrived at the summit it was windy, much more than the day before. These were 50-mile-an-hour gusts, close to the maximum the telescope could take. The upper atmosphere was turbulent too. The first batch of numbers came in all over 2.0, which was very, very bad. While they waited to see if the winds calmed down, Batygin sketched out a graph and an equation in Greek. He kneeled on the floor next to Brown and asked for his help. Despite the fact that when we arrived at the summit we were warned that the altitude would make it harder to do calculations, what Batygin had in his notebook was black-belt-level math, he solved it without seeming to break a sweat. Brown checked the numbers: “We’re getting these 2.6s and 2.9s, and these I declare to be shit.”
“Hold on, I’m still not oxygened up,” said Batygin.
“What is 4319?” Brown asked, referring to one of the fields they had just imaged.
“You’re showing 1.7, I’m showing 2.2. Can you check?”
“Yeah,” Batygin replied, “It’s 2.2. Sorry, got that wrong.”
“Please put on your oxygen.”
Batygin placed the plastic tubes into his nose and, like putting on a cool pair of life-saving sunglasses, slipped the rest of the plastic tubing over his ears, and took a deep breath of that “sweet, sweet oxygen.” The control room computers had read out charts on the screens that showed wind speed and upper atmosphere turbulence as a red spiky graph, literally off the charts. Because of Planet Nine’s slow pace across the cosmos, these 2.0s and higher were useless data. They were looking for a barely visible point of light; if the stars were blurring out all over the place, Planet Nine would remain hiding. “We are not collecting data that is worthwhile,” Brown said as he began putting together a back-up plan for his back-up plan. In their three years of using Subaru they’ve had, as Batygin puts it, “pretty shitty luck.” Not only has the weather been unpredictable and rainy, but, in May 2018, the nearby volcano Kilauea erupted, destroying more than 700 houses and displacing roughly 3,000 residents. There was concern that sustained seismic activity also meant that Subaru and its camera might be rendered useless for a good portion of the year, leaving the team without an opportunity to observe. Plus, sometimes the weather is so bad on the summit, they can’t even go up. “Last December we were sequestered in astronomers headquarters and hoped that it would stop hailing.” Batygin said. “We didn’t collect one image that whole run. It was really disappointing.”
The team checked on the numbers again, which were climbing beyond 2.5, nearly killing Brown every time. Just short of defeated he said, “Three arc seconds and I’m going to the beach,” then requested more numbers.
“OK, this is a record breaker, are you ready?” asked Batygin.
Brown, resigned: “Yeah.”
The entire room shouted: “3.3!”
“In all my twenty-five years of observing on Mauna Kea I have never had three arc seconds,” Brown said. Numbers this bad were like turning this gigantic 8.2-meter telescope into a one-meter telescope; it would be impossible to find Planet Nine like this. Brown sat at his computer, arms crossed, and said, “The seeing is crappy, but the good news is clouds are coming in!” Indeed a ghostlike cloud was creeping over the valley and heading straight toward the summit. They waited another 20 minutes or so before Brown asked how it was looking.
Batygin: “Ok, now THIS is a record. Are you ready? 4919 is 3.8.”
Entire room: “3.8!”
Brown: “3.8!? 3.8! I think … I officially declare failure, which will significantly influence the music mix on the way down.”
At 4:10 a.m. Brown and Batygin decided to try the other side of the galactic plane, in the hope that the seeing would be better, and indeed the numbers improved — back down to 1.3s and 1.5s. One of the tricky and interesting things about if this planet exists, is that if they find it, they will have absolutely no idea how it got there. While snacks were consumed and the room filled with a symphony of yawns, Batygin stared into space. He was doing the opposite of what one should do at 14,000 feet — thinking, writing code, and doing some complex math to try to figure out how the movement of our galaxy and passing stars could have affected Planet Nine over time in order to determine the planet’s location. By 5:20 a.m. the numbers were staying low, which was just enough to save this batch. At 5:51 a.m. we heard a cuckoo. The morning’s drive-down-the-mountain playlist appropriately began with the Rolling Stones’s “(I Can’t Get No) Satisfaction.”
On Mauna Kea, the sun does not just rise, it cracks the sky open with an almost blinding yellow that is quickly seized and destroyed by an even brighter orange.
As day broke, the sky filled again with purples and pinks, the colors of dreams. We drove down the road and watched the landscape change: Small reddish rocks turned into boulders remaining from the Ice Age, when these mountains were once covered in glaciers. A third of the way down, a random shrub appeared alone next to the road. As we approached Hale Pōhaku, small bee-size yellow wildflowers danced left to right in the breeze, and tall stalk-like plants nestled into the ancient volcanic rock. Anyone would say it was beautiful here, the thick marshmallow clouds hovering in the valley below, always threatening the mental well-being of the astronomers watching out the window.
Back at base camp, around the same round table with the nylon tablecloth, Batygin and Brown reflected on the previous four years. “We had this conversation about a year ago,” said Batygin. “We were driving up to Mauna Kea, and Mike was like, ‘I think … this is kind of weird,’ and it is at the end of the day. It is weird because we get on a plane and we go to a beautiful island and instead of spending time like normal people do in Hawaii, we go to the only part of the island that is completely dead, and we stay up all night looking at the sky trying to find something that basically we imagine to be there. It’s a strange behavior but man, it’s so satisfying.”
I left Mauna Kea on Wednesday afternoon, right as the team was due to go to sleep. They observed five more nights and the weather cooperated for all of them. It was the first meaningful collection of data in more than a year. I waited until they both got back home to call and find out how it went. I spoke to Brown first. It had been just over two weeks and all of the images collected from the week of observing had not yet reached his desk at Caltech. “I’m depressed,” he said. “I’m in my we’re-not-going-to-find-it mode.” If they don’t find it this time, Brown said, “It’s perfectly plausible that we’ve pointed in the right direction and we’ve missed it.”
Two more weeks passed, a new year arrived, and with it came their data. I asked if they found it but so far, Planet Nine has not made its big debut. They are just starting to sort through their data, though. There is still hope. The trip wasn’t exactly their last chance to find Planet Nine. They’ll return in February for another round of observing. If they don’t find it then? “We will just keep going,” Batygin told me, “and by ‘keep going’ what I mean is wait for LSST.” The LSST is the Large Synoptic Survey Telescope, which is being constructed in the Chilean desert. It will be fully operational in 2022; its mirror will be even larger than Subaru and will scan the skies every possible clear night. If Planet Nine is out there, this thing will find it. And at first, it will likely discover 100’s more long-period Kuiper Belt objects that will point the team to the direction of Planet Nine.
“There’s a 5 or 10 percent chance anytime you look you’ll miss it because there’s a star in the way,” said Brown, “but you know, it just means — increasingly when you don’t find it you have to wonder what the heck is really going on here. I don’t think the answer is that there is no Planet Nine, certainly the phenomena that Planet Nine does are not going away. I don’t think there’s any other solution aside from Planet Nine to explain those phenomena so the question is why are we potentially failing in our prediction of where it is?”
Batygin said that finding Planet Nine is so difficult that it is not just like searching for a needle in a haystack, it is like “you’re also looking for it with the lights off and a bunch of fog and your calculations tell you that there should be one more needle in this room somewhere.” Can the effort be worth it? According to Brown, yes. “This is like first-level exploration of our solar system. This is like, finding a new continent,” he said. “It’s hard to imagine that any effort that I could actually put in would be ridiculous if we can actually find this thing that’s in our solar system that nobody knows about.”
Batygin said, “It’s really easy to miss something when you’re scanning the sky once, it’s true when you’re looking for the One Thing. We may or may not find Planet Nine, and of course if we find it, great, if we don’t find it then it doesn’t really mean anything.”
‘Finding Planet Nine is the grandest exploration that can be done of the solar system right now. I wouldn’t want to be doing anything else.’
If they do find their planet, our daily life will mostly remain the same. Sure, mobiles over children’s beds might have nine planets putting them into a peaceful sleep; science textbooks will have to be edited and books about our solar system rewritten. But after the hullabaloo of the news cycle and the introduction of a new planet to all of humankind, things will go back to normal. But for science and the field of astronomy, it will help complete a puzzle and make for many new ones as well. If Planet Nine exists, and if it is found, not only will it serve as a way to understand the bulk of exoplanets that have been discovered around other stars, but it will also help us understand the history of our own solar system; it will help us understand more of how the planets came to be and why they settled where they did. It will be one of the 21st century’s greatest scientific discoveries. We have no idea what a six-Earth mass planet looks like. Uranus and Neptune are 14 and 17 Earth masses; Mars is 10 times less massive than Earth. There is nothing in our solar system that size. Six Earth masses could essentially be a core of a planet like Uranus and Neptune, and if Planet Nine exists that is likely its story. The team thinks that during the early days of the solar system, when the outer planets were forming, there was an additional planetary core, near where Uranus and Neptune were growing. But somewhere in those early days, the third core somehow got flung out by a gravitational interaction with Jupiter or Saturn, and as it was heading out of the solar system, became trapped by the gravity of the sun. Since that time it has been orbiting in the distant solar system, silently sculpting Kuiper Belt objects, marking evidence of its existence. If these objects do in fact point to Planet Nine, it will have been quite the planetary smoke signal, one so unlikely to be found.
And they’re not the only ones who’ve been scooped when searching for something. In January 1613, while observing Jupiter and its moons, Galileo caught a glimpse of what he thought was a “fixed star.” He marked a dark spot in his notebook and moved on. He had unknowingly detected the light from Neptune. And just months before Le Verrier predicted its existence, an observatory in England detected it three separate times, noting it as a star. Batygin takes comfort in facts like these. “When there is one thing you’re looking for in the night sky — even the world’s best astronomer, which certainly Galileo was really good — you’re going to miss it the first twenty-five times,” he said.
Many in the scientific community are still skeptical of Planet Nine’s existence. Batygin understands their skepticism: “Our firm belief is that only crazy people propose planets beyond Neptune.” But he and Brown have now joined the ranks of those throughout history who have said, “But what about a giant planet!” Only this time, they mean it, and they have the math to back it up. Batygin, being the theorist that he is, feels that he has already proven its existence, the same way Le Verrier predicted Neptune’s. Sure Galle was lucky that he happened to be using the telescope at the exact right time and that D’Arrest had brought a star chart with him, but even if he hadn’t, someone, someday would have found Neptune. For Planet Nine, its discovery day awaits. Until that day comes, if it ever does, they will keep searching.
After the observing run was complete, I asked the pair if they ever felt that trying to find Planet Nine was ridiculous, that the whole notion of a giant missing planet and the efforts they have gone to to find it ever make them feel defeated. They both gave me roughly the same response: no. Their answer brought to mind the French philosopher and writer Albert Camus. He thought a lot about the myth of Sisyphus and plucked his unfortunate mythical backstory away from the root of his actions, the eternal task of pushing a boulder up a mountain only to watch it fall back down again. For Camus, he symbolized the despair that can come from making consistent efforts only to be disappointed again and again with the outcome. However he saw this phenomenon with humankind. We have an ability to feel joy and find happiness in our tasks before a reward of completion ever arrives, even if it never does. “The struggle itself… is enough to fill a man’s heart,” he wrote.
Despite their constant disappointment and exhaustion, both Brown and Batygin find joy in the process of the search, in the not-knowing, in the wondering, and maybe sometimes even the waiting. “Man’s sole greatness is to fight against what is beyond him,” Camus said. So why do we bother going to the tops of mountains anyway? To see whatever is below, to understand if we are safe down there? We do it to feel bigger. To feel smaller. To get a new perspective, to do it and say we did it. There are many reasons to make that journey, to see what it is like on the other side, to get to know ourselves better. No one climbs a mountain without searching for an answer to something. So many hero stories begin or end at the top of a mountain. It is an act of completion, a marker of accomplishment, a reminder that one is alive and despite the absurdity of it all we can get ourselves to the top of the sky. Or maybe the attempt to reach the summit is in itself, enough. Camus said for this reason that “one must imagine Sisyphus happy.”
* * *
Shannon Stirone Shannon Stirone is a freelance writer based in California focused on NASA, space policy, and space exploration. Her work has appeared in Popular Science, The Atlantic, The New Republic, and elsewhere.
Editor: Kelly Stout
Fact checker: Matt Giles
Copy editor: Jacob Gross | 0.902685 | 3.040471 |
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a mass below the limiting mass for thermonuclear fusion of deuterium. Some researchers call them free-floating planets whereas others call them planetary-mass brown dwarfs. Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud but there is no consensus amongst astronomers on whether the formation process should be taken into account when classifying an object as a planet. Free-floating sub-brown dwarfs can be observationally indistinguishable from rogue planets, which formed around a star and were ejected from orbit. A sub-brown dwarf formed free-floating in a star cluster may be captured into orbit around a star, making distinguishing sub-brown dwarfs and large planets difficult. A definition for the term "sub-brown dwarf" was put forward by the IAU Working Group on Extra-Solar Planets, which defined it as a free-floating body found in young star clusters below the lower mass cut-off of brown dwarfs.
The smallest mass of gas cloud that could collapse to form a sub-brown dwarf is about 1 Jupiter mass. This is because to collapse by gravitational contraction requires radiating away energy as heat and this is limited by the opacity of the gas. A 3 MJ candidate is described in a 2007 paper. There is no consensus whether these companions of stars should be considered sub-brown dwarfs or planets. WD 0806-661 B DT Virginis c FW Tauri b HD 106906 b ROXs 42Bb There is no consensus whether these companions of brown dwarfs should be considered sub-brown dwarfs or planets; the 5–10MJ companion of 2MASS J04414489+2301513 2M1207b Also called Rogue planets: WISE 0855–0714 3–10 MJ about 7 light years away S Ori 52 UGPS J072227.51-054031.2 10–25 MJ 13 light years away Cha 110913-773444 5–15 MJ 163 light years away CFBDSIR2149-0403 4–7 MJ 130 light years away OTS 44 11.5 MJ 550 light years away Brown dwarf Giant planet Hot Jupiter Red dwarf Rogue planet List of planet types
A Splendid Hazard is a 1920 American silent drama film directed by Allan Dwan and starring Henry B. Walthall; the film is based on the 1910 book of the same name. The film was produced by the Mayflower Photoplay Company, it is not known whether the film survives. The main charter Karl Breitman thinks he is a descendant of Napoleon and tries bring back to France the French monarchy; as part of his plot he courts Hedda Gobert. After winning Hedda heart he takes the documents from her, he travels to America to visit Admiral Killigrew. He hopes, he finds a treasure map in the Admiral's home and travels to Corsica. Before finding the Napoleon wealth, he comes across someone, he challenges them to a duel. In the duel he is mortally wounded, he dies at Hedda. Henry B. Walthall as Karl Breitman Rosemary Theby as Hedda Gobert Norman Kerry as John Fitzgerald Ann Forrest as Laura Killigrew Hardee Kirkland as Adm. Killegrew Thomas Jefferson as Dr. Ferraud Philo McCullough as Arthur Cathewe J. Jiquel Lanoe as Jiquel Lanoe Joseph J. Dowling as Joseph Dowling A Splendid Hazard on IMDb
The 1925 Central Council Tournament Final was not the All-Ireland Final as is sometimes stated. It had no bearing on the destination of the 1925 All-Ireland Senior Football Championship, an inter-county Gaelic football tournament for the top teams in Ireland. While Galway's All-Ireland title was not on the line, there was prestige to play for, the chance to prove that they were worthy champions; this All-Ireland final was the last game of a second championship played in lieu of the original, in which Galway were made champions after Kerry and Cavan were disqualified. Galway's first All-Ireland football title, it followed two previous losing appearances in the final. "Kerry's Victory" on YouTube, a British Pathé newsreel of the game | 0.899287 | 3.821368 |
Formulations of Quantum MechanicsWe must try to distinguish a "formulation" of quantum mechanics from an "interpretation" of quantum mechanics, although it is difficult sometimes. For example, David Bohm's 1952 Pilot-Wave theory provided "hidden variables" in the form of a "quantum potential" that changes instantaneously (infinitely faster than light speed) throughout all space, in order to restore a deterministic view of quantum mechanics, which Bohm thought that Einstein wanted. Einstein was appalled. Many writers describe this as the "pilot-wave interpretation" and it is both a formulation and an interpretation. Different formulations in both classical and quantum mechanics provide exactly the same predictions and experimental results. But the mathematics of one formulation may yield solutions of a specific physical situation much more quickly and easily than others. Some are more easily generalized to relativistic mechanics. Some help us to "visualize" what is going on - the so-called "elements of reality" - in particular problems. Some are better at eigenvalues than transition probabilities, some better for bound/periodic systems than for "free" particles. Some find "constants of the motion" better. Some are better for quantum field theory than for quantum electrodynamics and so on. Just as there are many formulations of classical mechanics, there are many formulations (some analogous) of quantum mechanics.
Old Quantum Theory (Bohr-Sommerfeld, 1913)Bohr's original work is no longer an active formulation of quantum mechanics, because it explains relatively little, but that little was enough to find the various "quantum numbers" (principal, angular, magnetic, and spin) behind atomic structure and atomic spectral lines. With the help of Sommerfeld (angular momentum) and later Pauli (spin), the old quantum theory discovered the "allowed stationary states" and the "selection rules" for allowed transitions between those states in various atoms and later molecules. It could not calculate "transition probabilities" needed to explain the intensities of the spectral lines. Bohr quantized the electron orbits (visualized as planetary electrons traveling around a Rutherford nucleus), treating them as periodic bound systems. He did not quantize the "free" radiation emitted or absorbed when electrons "jump" from one orbit to another. Bohr thought it was classical electromagnetic radiation until at least 1925, ignoring Einstein's hypothesis of light quanta (1905), their connection to waves (1909), and their emission and absorption, along with his discovery of "stimulated" emission (1916). Bohr's "correspondence principle" allowed him to match up the transitions for states with large quantum numbers to classical behavior at large distances from the nucleus, which helped him to determine some physical constants (e.g., Rydberg). In the mid-1920's, Bohr's assistant Hendrik Kramers analyzed the allowed orbits into their Fourier components and developed a matrix of transitions between states. He showed that transition probabilites were proportional to the squares of the Fourier component waves. Werner Heisenberg helped Kramers with the calculations in a joint paper, and then returned to Göttingen where he extended the matrix idea to reformulate old quantum theory as "matrix mechanics." With the help of Max Born and Pascual Jordan, he could correctly calculate transition probabilities, explaining the strengths of spectral lines. Wolfgang Pauli used matrix mechanics to calculate the structure of the hydrogen atom, reproducing Bohr's results.
Matrix Mechanics (Heisenberg-Born-Jordan, 1925)While alone on an island recovering from an allergy attack, Werner Heisenberg wrote a paper about a new method to calculate transition probabilities and predict intensities for spectral lines. When Max Born looked at the paper, he recognized Heisenberg's work as matrix multiplications. Born and Pascual Jordan developed the mathematics for the first consistent formulation of quantum mechanics that could explain (and calculate transition probabilities for) Bohr's "quantum jumps." Heisenberg looked for quantitities that he called "observables," as opposed to Bohr's visualization of circular and elliptical orbits for the electrons. One of these is the system's energy, for example, which he could calculate without reference to an orbit. Heisenberg could also calculate position and momentum "observables," but these involved non-commuting operators (for which pq ≠ qp). Max Born knew that matrices have this non-commuting property. Heisenberg showed that in general, the "quantum conditions" are that pq - qp = ih, which later was written as a minimal condition known as the "uncertainty principle," pq - qp ≥ ih. Heisenberg's matrices are Hermitian, so its eigenvalues are real, and Heisenberg identified those eigenvalues with the possible values of an observable. The matrix elements of the Hamiltonian are diagonal (off-diagonal elements are all zero). Identifying the energy levels En in an atom as observables which provide no knowledge of the internal dynamics (e.g., electron position, momentum, periodicity, etc.), Heisenberg declared the "underlying reality" as unknowable in principle. In any case, matrix mechanics gives us no "visualization" of what is going on "really." The matrix elements of the polarization are periodic functions of the time that provide the frequencies and intensities of the spectral lines. Heisenberg's square (n x n) matrices are operators that operate on an n x 1 single-row or -column vector. In the Heisenberg picture these "state vectors" ( | ψ > in Dirac notation) are constants, and the operators A evolve in time.
iℏ dA / dt = [ A (t), H] + δA / δt (1)The operator H is the system Hamiltonian, the total (kinetic plus potential) energy.
Wave Mechanics (Schrödinger, 1926)In the Schrödinger picture, the operators are time-independent, and the vectors, called wave functions, evolve in time. The time-dependent Schrödinger equation is a linear partial differential equation very similar to Heisenberg's equation (1)
iℏ δψ / δt = H ψ (2)For a single particle of mass m moving in an electric (but not magnetic field), Schrödinger could write his equation in ordinary physical space as
iℏ δψ (r, t) / δt = [ - ℏ2 ∇2 / 2 m + V (r, t) ] ψ (r, t) (3)He could even write a two-particle wave function (important for the "entangled" particles in the EPR experiments), now in a six-dimensional space, δψ (r1, r2, t). But Schrödinger's easily "visualizable" wave functions were not the vectors of n-dimensional "configuration space" of Heisenberg's matrix mechanics. Von Neumann called it a Hilbert space, in which n can be infinite and range over both discrete and continuous eigenvalues. The Copenhagen-Göttingen school was interested in energy levels and "quantum jumps." Heisenberg had successfully explained the relative intensities of spectral lines in terms of transition probabilities. Pauli used matrix mechanics to derive the structure of the hydrogen atom. Schrödinger, on the other hand, built his "wave mechanics" with an emphasis on the "wave-particle duality" that Einstein had been advocating for twenty years. For Einstein. "reality" consisted of individual light quanta emitted and absorbed by the atoms. When there are large numbers of such quanta, the wavelike properties show up. Einstein imagined the waves to be a "ghost-field" that guided the light quanta to exhibit classical interference phenomena. Crests in the waves would have more quanta than the nodes. Louis de Broglie accepted Einstein's view that light waves consist of particles. De Broglie hypothesized that material particles might have wave characteristics that guide the particles. He proposed "pilot waves" with a wavelength related to the moomentum p of the particle.
λ = h / p (4)Schrödinger's breakthrough was finding the wave equation to describe de Broglie matter waves. Schrödinger and de Broglie argued that the electronic structure of atoms could be visualized as standing waves that fit an integer number of de Broglie wavelengths around each orbit. Schrödinger claimed he had found a natural explanation for integer quantum numbers that had merely been postulated by Bohr. Einstein hoped the wave theory might restore a continuous field explanation. Schrödinger interpreted an electron wave ψ as the actual electric charge density spread out in space. Einstein had strong reasons for objecting to this view as early as 1905 for light quanta, and Schrödinger gave up that interpretation. A few weeks after Schrödinger's final paper, Max Born offered his statistical interpretation, in which ψ is a probability amplitude (generally a complex number, which supports interference with itself), whose absolute square ψ*ψ is the probability of finding the electron somewhere. (cf. Kramers' transition amplitude, which was squared to provide the transition probability. ) Born acknowledged Einstein's similar view for the relation between light waves (the "ghost-field") and light particles (by then being called photons).
Poisson Bra-kets, Transformation Theory (Dirac, 1927)
Creation-Destruction Operators (Dirac-Jordan-Klein, 1927)
Density Matrix (Von Neumann, 1927)
Variational-Hamilton's Principle (Jordan-Klein, 1927)
Phase Space Distribution (Wigner, 1932)
Path Integral-Sum over Histories (Feynman, 1948)
Pilot-Wave (De Broglie-Bohm, 1952)
Hamilton-Jacobi/Action-Angle (Leacock-Padgett, 1983) | 0.820833 | 4.161239 |
An astronomical event you can see from your backyard
Venus, which is the brightest planet or star in the sky, will be joined on November 24 by Jupiter, which will be the second brightest at this time. Look to the western horizon at around sunset to see these two heavenly objects together in the sky. It is a great opportunity for kids to have a chance to learn about night sky viewing without needing to leave the suburbs.
Photo of Venus and Jupiter courtesy of Brocken Inaglory @ wikimedia
Venus is called the morning star because it is only visible either in the morning or early evening. This is because it lies between Earth and the sun, so for most of the night it will be on the far side from us. When this divine lady visits us, it is always the brightest of all the planets and the stars.
Image of Venus courtesy of NASA
Jupiter is the largest planet in our solar system and is the planet we Earth dwellers should be the most grateful for because it protects Earth by sucking up comets and asteroids with its powerful gravitational pull. It is usually the second brightest of the planets, which, along with Venus, makes it very easy to spot.
Image of Jupiter courtesy of NASA and the Hubble Telescope
Watching this conjunction is not very hard. In fact, both planets should be bright enough to be seen from suburban environments, though city centres might still have too much light pollution. The main thing that you need is a view of the western horizon.
Look towards the western horizon during dusk. Venus and Jupiter should become visible about 15 to 30 minutes after sunset. You will see 2 bright "stars" in the sky, and if you are in a suburban environment, they may be the main 2 stars visible. On the 24th they will only be 1.4 degrees apart, which is about the width of your finger when held up in front of you with an outstretched arm. They will remain visible for about an hour and half until they set.
On the days before and after the 24th, they will still also be close together. So you don't have to wait until that one night to spot them near each other in the sky.
Photographing a conjunction is also pretty easy. The planets will be visible at dusk, which means there will still be some light in the sky. This is the perfect time to take a photo with both the planets and terrain. The main thing you want is a tripod. If you are using a mobile phone, you can buy a phone tripod or adapters for regular camera tripods.
Image of a phone tripod courtesy of Ivan Radic @ Flickr
When you take the photograph you want a balance between the stars and the terrain, so you need to be able to adjust the length of the exposure. With mobile phones, you often need to download a night photography app that will help you do this. How good the results will be with a phone will depend on the quality of your phone's camera. The latest and most expensive phones having amazing cameras.
Photo of a Venus and Jupiter conjunction courtesy of cafuego @ Flickr
You may have looked to the sky and seen conjunctions before and not really paid much attention to them. But taking the opportunity to take your kids out to view conjunctions is very valuable. Often with urban and suburban living, we don't see much in the night sky, so we usually don't take time to watch the skies. But when the planets come together in the sky we can view them from our backyards and balconies. | 0.862649 | 3.023165 |
By : Lucy Connolly On : 27 Sep 2019 15:45
Astronomers have released awe-inspiring footage recreating the moment a black hole tears apart a star millions of light-years away.
NASA’S Transiting Exoplanet Survey Satellite (TESS), which has been tasked with searching space for new planets witnessed more than it bargained for.
The incredible phenomenon, called a tidal disruption event, is extremely rare – occurring only once every 10,000 to 100,000 years – and this is the first time TESS has captured such a moment.
You can check out the footage for yourself below:
The event, named ASASSN-19bt, was first discovered on January 29 this year by a worldwide network of 20 robotic telescopes headquartered at Ohio State University, according to NASA.
Although TESS was able to capture the phenomenon just months after launching in April 2018, NASA says scientists have only been able to observe approximately 40 tidal disruptions in history.
Padi Boyd, the TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said:
For TESS to observe ASASSN-19bt so early in its tenure, and in the continuous viewing zone where we could watch it for so long, is really quite extraordinary.
Future collaborations with observatories around the world and in orbit will help us learn even more about the different outbursts that light up the cosmos.
The full findings, which were published in The Astrophysical Journal, as per WOSU Radio, make clear that the conditions have to be just right for a black hole to tear apart a star; the star can’t be too close that it simply gets sucked up, and it can’t be too far that it bounces off and out into the galaxy.
Astronomers believe the black hole weighs around six million times the sun’s mass, and is located approximately 375 million light-years away in a galaxy of similar size to the Milky Way, NASA said.
Using their collected data, astronomers were able to determine that the temperature dropped by about 50 per cent – from around 71,500°F to 35,500°F – over a few days, and there was a low level of X-ray emission at the time of the event.
Although scientists are yet to fully understand why tidal disruptions produce so much UV emission and so few X-rays, S. Bradley Cenko, Swift’s principal investigator at Goddard, has offered a number of theories.
One such theory is that the light bounces through the newly created debris and loses energy, while another is that perhaps the disk forms further from the black hole than initially believed and so the light isn’t as affected by the object’s extreme gravity.
More early-time observations of these events may help us answer some of these lingering questions.
Whatever the answer is, I think we can all agree this is perhaps the most impressive footage to come out of NASA in recent years.
Mind = blown.
If you have a story you want to tell send it to UNILAD via [email protected]
A Broadcast Journalism Masters graduate who went on to achieve an NCTJ level 3 Diploma in Journalism, Lucy has done stints at ITV, BBC Inside Out and Key 103. While working as a journalist for UNILAD, Lucy has reported on breaking news stories while also writing features about mental health, cervical screening awareness, and Little Mix (who she is unapologetically obsessed with). | 0.831554 | 3.553258 |
Astronomers Discover 854 Ultra-Dark Galaxies in the Famous Coma Cluster
Led by Stony Brook’s Jin Koda, PhD, the discovery surpasses the 2014 find by more than 800
A color image made with B, R, and i-band images from the Subaru Telescope. A small region of 6 x 6 arcmin is cut out from large Coma Cluster images. Yellow circles show two of the 47 dark galaxies discovered last year, and green circles are the ones discovered in this new study. Image without the labels is here, image without the labels and circles is here.
STONY BROOK, NY, June 22, 2015 – A team of researchers from Stony Brook University and the National Astronomical Observatory of Japan (NAOJ) have discovered 854 “ultra-dark galaxies” in the Coma Cluster by analyzing data from the 8.2-meter Subaru Telescope. The new discovery, published in the June 2015 edition of the Astrophysical Journal Letters, surpasses the 2014 discovery of 47 mysterious dark galaxies by more than 800 and suggests that galaxy clusters are the key environment for the evolution of these mysterious dark galaxies.
“The findings suggests that these galaxies appear very diffuse and are very likely enveloped by something very massive, “said Jin Koda, PhD, principal investigator of the study and Associate Professor in the Department of Physics and Astronomy at Stony Brook University. The ultra-dark galaxies are similar in size to the Milky Way, but have only 1/1,000 of stars that our galaxy does (Figure 1.) The stellar population within such fluffy extended galaxies is subject to rapid disruption due to a strong tidal force detected within the cluster. “We believe that something invisible must be protecting the fragile star systems of these galaxies, something with a high mass,” said Dr. Koda. “That ‘something’ is very likely an excessive amount of dark matter.” The component of visible matter, such as stars, is calculated to contribute only one percent or less to the total mass of each galaxy. The rest – dark matter – accounts for more than 99 percent.
The Subaru Telescope revealed that these dark galaxies contain old stellar populations and shows a spatial distribution similar to those of other brighter galaxies in the Coma Cluster (Figure 2). It suggests that there has been a long-lived population of galaxies within the cluster and the amount of visible matter they contain, less than one percent, is extremely low compared to the average fraction within the universe.
A 2.9 x 2.9 degree field-of-view sky image of the Coma Cluster. (Left) An image from the Digitized Sky Survey (from a digitized photo-plate). Eighteen white squares are the coverage by the Subaru Telescope with the R-band filter. Red and yellow parts were observed in multiple bands with Subaru, which enabled the study of galaxy colors. The light blue region is the area in Figure 1. (Right) The distribution of the newly found dark galaxies. Blue circles indicate the ones of particularly large sizes (roughly the size of the Milky Way galaxy even though the total light is only 1/1,000 of the Milky Way).
(Credit: NAOJ/Stony Brook University)
These galaxies are dark because they have lost gas needed to create new stars during, or after, their largely unknown formation process billions of years ago. From their preferential presence within the cluster, it’s likely that the cluster environment played a key role in the loss of gas, which affects star formation within the galaxy. Several loss mechanisms are possible, including ram-pressure stripping by intra-cluster gas, gravitational interactions with other galaxies within the cluster, and gas outflows due to simultaneous supernova explosions triggered by the ram pressure or gravitational encounters.
Dark matter is one of the unresolved mysteries in Cosmology. Studies of such interplay between dark matter and stars and gas in galaxies are increasingly attracting attention from researchers. “This discovery of dark galaxies may be the tip of the iceberg,” said Dr. Koda. “We may find more if we look for fainter galaxies embedded in a large amount of dark matter, with the Subaru Telescope and additional observations may expose this hidden side of the Universe.”
Editor’s Note: Last year, Stony Brook started cluster faculty hires in the field of Cosmology in partnership with the Brookhaven National Laboratory (BNL). This initiative capitalizes on the new development of the upcoming Large Synoptic Survey Telescope (LSST) whose camera is being constructed at BNL. The team of researchers at Stony Brook University, including upcoming new faculty members, will continue to research dark matter, dark energy, and galaxy formation and evolution.
Jin Koda (Stony Brook University)
Masafumi Yagi (National Astronomical Observatory of Japan/ Hosei University) Hitomi Yamanoi (National Astronomical Observatory of Japan) Yutaka Komiyama (National Astronomical Observatory of Japan/ SOKENDAI – the Graduate University for Advanced Studies) | 0.886801 | 3.890363 |
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from the threshold chosen for describing an extinction event as "major", and the data chosen to measure past diversity.
Because most diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life. Extinction occurs at an uneven rate. Based on the fossil record, the background rate of extinctions on Earth is about two to five taxonomic families of marine animals every million years. Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to land animals.
The Great Oxygenation Event, which occurred around 2.45 billion years ago, was probably the first major extinction event. Since the Cambrian explosion, five further major mass extinctions have significantly exceeded the background extinction rate. The most recent and arguably best-known, the Cretaceous–Paleogene extinction event, which occurred approximately 66 million years ago (Ma), was a large-scale mass extinction of animal and plant species in a geologically short period of time. In addition to the five major mass extinctions, there are numerous minor ones as well, and the ongoing mass extinction caused by human activity is sometimes called the sixth extinction. Mass extinctions seem to be a mainly Phanerozoic phenomenon, with extinction rates low before large complex organisms arose.
Major extinction events
In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five mass extinctions. They were originally identified as outliers to a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applied to the accumulating data, it has been established that multicellular animal life has experienced five major and many minor mass extinctions. The "Big Five" cannot be so clearly defined, but rather appear to represent the largest (or some of the largest) of a relatively smooth continuum of extinction events.
- Ordovician–Silurian extinction events (End Ordovician or O–S): 450–440 Ma (million years ago) at the Ordovician–Silurian transition. Two events occurred that killed off 27% of all families, 57% of all genera and 60% to 70% of all species. Together they are ranked by many scientists as the second largest of the five major extinctions in Earth's history in terms of percentage of genera that became extinct.
- Late Devonian extinction: 375–360 Ma near the Devonian–Carboniferous transition. At the end of the Frasnian Age in the later part(s) of the Devonian Period, a prolonged series of extinctions eliminated about 19% of all families, 50% of all genera and at least 70% of all species. This extinction event lasted perhaps as long as 20 million years, and there is evidence for a series of extinction pulses within this period.
- Permian–Triassic extinction event (End Permian): 252 Ma at the Permian–Triassic transition. Earth's largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species (53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species, including insects). The highly successful marine arthropod, the trilobite, became extinct. The evidence regarding plants is less clear, but new taxa became dominant after the extinction. The "Great Dying" had enormous evolutionary significance: on land, it ended the primacy of mammal-like reptiles. The recovery of vertebrates took 30 million years, but the vacant niches created the opportunity for archosaurs to become ascendant. In the seas, the percentage of animals that were sessile dropped from 67% to 50%. The whole late Permian was a difficult time for at least marine life, even before the "Great Dying".
- Triassic–Jurassic extinction event (End Triassic): 201.3 Ma at the Triassic–Jurassic transition. About 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species became extinct. Most non-dinosaurian archosaurs, most therapsids, and most of the large amphibians were eliminated, leaving dinosaurs with little terrestrial competition. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments. The Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia (e.g., Koolasuchus).
- Cretaceous–Paleogene extinction event (End Cretaceous, K–Pg extinction, or formerly K–T extinction): 66 Ma at the Cretaceous (Maastrichtian) – Paleogene (Danian) transition interval. The event formerly called the Cretaceous-Tertiary or K–T extinction or K–T boundary is now officially named the Cretaceous–Paleogene (or K–Pg) extinction event. About 17% of all families, 50% of all genera and 75% of all species became extinct. In the seas all the ammonites, plesiosaurs and mosasaurs disappeared and the percentage of sessile animals (those unable to move about) was reduced to about 33%. All non-avian dinosaurs became extinct during that time. The boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds, the latter descended from theropod dinosaurs, emerged as dominant large land animals.
Despite the popularization of these five events, there is no definite line separating them from other extinction events; using different methods of calculating an extinction's impact can lead to other events featuring in the top five.
Older fossil records are more difficult to interpret. This is because:
- Older fossils are harder to find as they are usually buried at a considerable depth.
- Dating older fossils is more difficult.
- Productive fossil beds are researched more than unproductive ones, therefore leaving certain periods unresearched.
- Prehistoric environmental events can disturb the deposition process.
- The preservation of fossils varies on land, but marine fossils tend to be better preserved than their sought after land-based counterparts.
It has been suggested that the apparent variations in marine biodiversity may actually be an artifact, with abundance estimates directly related to quantity of rock available for sampling from different time periods. However, statistical analysis shows that this can only account for 50% of the observed pattern, and other evidence (such as fungal spikes)[clarification needed] provides reassurance that most widely accepted extinction events are real. A quantification of the rock exposure of Western Europe indicates that many of the minor events for which a biological explanation has been sought are most readily explained by sampling bias.
Research completed after the seminal 1982 paper has concluded that a sixth mass extinction event is ongoing:
- 6. Holocene extinction: Currently ongoing. Extinctions have occurred at over 1000 times the background extinction rate since 1900. The mass extinction is a result of human activity, driven by population growth and overconsumption of the earth's natural resources. The 2019 global biodiversity assessment by IPBES asserts that out of an estimated 8 million species, 1 million plant and animal species are currently threatened with extinction.
More recent research has indicated that the End-Capitanian extinction event likely constitutes a separate extinction event from the Permian–Triassic extinction event; if so, it would be larger than many of the "Big Five" extinction events.
List of extinction events
Mass extinctions have sometimes accelerated the evolution of life on Earth. When dominance of particular ecological niches passes from one group of organisms to another, it is rarely because the new dominant group is "superior" to the old and usually because an extinction event eliminates the old dominant group and makes way for the new one.
For example, mammaliformes ("almost mammals") and then mammals existed throughout the reign of the dinosaurs, but could not compete for the large terrestrial vertebrate niches which dinosaurs monopolized. The end-Cretaceous mass extinction removed the non-avian dinosaurs and made it possible for mammals to expand into the large terrestrial vertebrate niches. Ironically, the dinosaurs themselves had been beneficiaries of a previous mass extinction, the end-Triassic, which eliminated most of their chief rivals, the crurotarsans.
Another point of view put forward in the Escalation hypothesis predicts that species in ecological niches with more organism-to-organism conflict will be less likely to survive extinctions. This is because the very traits that keep a species numerous and viable under fairly static conditions become a burden once population levels fall among competing organisms during the dynamics of an extinction event.
Furthermore, many groups which survive mass extinctions do not recover in numbers or diversity, and many of these go into long-term decline, and these are often referred to as "Dead Clades Walking". However, clades that survive for a considerable period of time after a mass extinction, and which were reduced to only a few species, are likely to have experienced a rebound effect called the "push of the past".
Darwin was firmly of the opinion that biotic interactions, such as competition for food and space—the ‘struggle for existence’—were of considerably greater importance in promoting evolution and extinction than changes in the physical environment. He expressed this in The Origin of Species: "Species are produced and exterminated by slowly acting causes…and the most import of all causes of organic change is one which is almost independent of altered…physical conditions, namely the mutual relation of organism to organism-the improvement of one organism entailing the improvement or extermination of others".
Patterns in frequency
It has been suggested variously that extinction events occurred periodically, every 26 to 30 million years, or that diversity fluctuates episodically every ~62 million years. Various ideas attempt to explain the supposed pattern, including the presence of a hypothetical companion star to the sun, oscillations in the galactic plane, or passage through the Milky Way's spiral arms. However, other authors have concluded that the data on marine mass extinctions do not fit with the idea that mass extinctions are periodic, or that ecosystems gradually build up to a point at which a mass extinction is inevitable. Many of the proposed correlations have been argued to be spurious. Others have argued that there is strong evidence supporting periodicity in a variety of records, and additional evidence in the form of coincident periodic variation in nonbiological geochemical variables.
Mass extinctions are thought to result when a long-term stress is compounded by a short-term shock. Over the course of the Phanerozoic, individual taxa appear to be less likely to become extinct at any time, which may reflect more robust food webs as well as less extinction-prone species and other factors such as continental distribution. However, even after accounting for sampling bias, there does appear to be a gradual decrease in extinction and origination rates during the Phanerozoic. This may represent the fact that groups with higher turnover rates are more likely to become extinct by chance; or it may be an artefact of taxonomy: families tend to become more speciose, therefore less prone to extinction, over time; and larger taxonomic groups (by definition) appear earlier in geological time.
It has also been suggested that the oceans have gradually become more hospitable to life over the last 500 million years, and thus less vulnerable to mass extinctions,[note 1] but susceptibility to extinction at a taxonomic level does not appear to make mass extinctions more or less probable.
There is still debate about the causes of all mass extinctions. In general, large extinctions may result when a biosphere under long-term stress undergoes a short-term shock. An underlying mechanism appears to be present in the correlation of extinction and origination rates to diversity. High diversity leads to a persistent increase in extinction rate; low diversity to a persistent increase in origination rate. These presumably ecologically controlled relationships likely amplify smaller perturbations (asteroid impacts, etc.) to produce the global effects observed.
Identifying causes of specific mass extinctions
A good theory for a particular mass extinction should: (i) explain all of the losses, not just focus on a few groups (such as dinosaurs); (ii) explain why particular groups of organisms died out and why others survived; (iii) provide mechanisms which are strong enough to cause a mass extinction but not a total extinction; (iv) be based on events or processes that can be shown to have happened, not just inferred from the extinction.
It may be necessary to consider combinations of causes. For example, the marine aspect of the end-Cretaceous extinction appears to have been caused by several processes which partially overlapped in time and may have had different levels of significance in different parts of the world.
Arens and West (2006) proposed a "press / pulse" model in which mass extinctions generally require two types of cause: long-term pressure on the eco-system ("press") and a sudden catastrophe ("pulse") towards the end of the period of pressure. Their statistical analysis of marine extinction rates throughout the Phanerozoic suggested that neither long-term pressure alone nor a catastrophe alone was sufficient to cause a significant increase in the extinction rate.
Most widely supported explanations
Macleod (2001) summarized the relationship between mass extinctions and events which are most often cited as causes of mass extinctions, using data from Courtillot et al. (1996), Hallam (1992) and Grieve et al. (1996):
- Flood basalt events: 11 occurrences, all associated with significant extinctions But Wignall (2001) concluded that only five of the major extinctions coincided with flood basalt eruptions and that the main phase of extinctions started before the eruptions.
- Sea-level falls: 12, of which seven were associated with significant extinctions.
- Asteroid impacts: one large impact is associated with a mass extinction, i.e. the Cretaceous–Paleogene extinction event; there have been many smaller impacts but they are not associated with significant extinctions.
The most commonly suggested causes of mass extinctions are listed below.
Flood basalt events
The formation of large igneous provinces by flood basalt events could have:
- produced dust and particulate aerosols which inhibited photosynthesis and thus caused food chains to collapse both on land and at sea
- emitted sulfur oxides which were precipitated as acid rain and poisoned many organisms, contributing further to the collapse of food chains
- emitted carbon dioxide and thus possibly causing sustained global warming once the dust and particulate aerosols dissipated.
Flood basalt events occur as pulses of activity punctuated by dormant periods. As a result, they are likely to cause the climate to oscillate between cooling and warming, but with an overall trend towards warming as the carbon dioxide they emit can stay in the atmosphere for hundreds of years.
It is speculated that massive volcanism caused or contributed to the End-Permian, End-Triassic and End-Cretaceous extinctions. The correlation between gigantic volcanic events expressed in the large igneous provinces and mass extinctions was shown for the last 260 Myr. Recently such possible correlation was extended for the whole Phanerozoic Eon.
These are often clearly marked by worldwide sequences of contemporaneous sediments which show all or part of a transition from sea-bed to tidal zone to beach to dry land – and where there is no evidence that the rocks in the relevant areas were raised by geological processes such as orogeny. Sea-level falls could reduce the continental shelf area (the most productive part of the oceans) sufficiently to cause a marine mass extinction, and could disrupt weather patterns enough to cause extinctions on land. But sea-level falls are very probably the result of other events, such as sustained global cooling or the sinking of the mid-ocean ridges.
A study, published in the journal Nature (online June 15, 2008) established a relationship between the speed of mass extinction events and changes in sea level and sediment. The study suggests changes in ocean environments related to sea level exert a driving influence on rates of extinction, and generally determine the composition of life in the oceans.
The impact of a sufficiently large asteroid or comet could have caused food chains to collapse both on land and at sea by producing dust and particulate aerosols and thus inhibiting photosynthesis. Impacts on sulfur-rich rocks could have emitted sulfur oxides precipitating as poisonous acid rain, contributing further to the collapse of food chains. Such impacts could also have caused megatsunamis and/or global forest fires.
Most paleontologists now agree that an asteroid did hit the Earth about 66 Ma ago, but there is an ongoing dispute whether the impact was the sole cause of the Cretaceous–Paleogene extinction event.
Nonetheless, in October 2019, researchers reported that the Cretaceous Chicxulub asteroid impact that resulted in the extinction of non-avian dinosaurs 66 Ma ago, also rapidly acidified the oceans producing ecological collapse and long-lasting effects on the climate, and was a key reason for end-Cretaceous mass extinction.
Sustained and significant global cooling could kill many polar and temperate species and force others to migrate towards the equator; reduce the area available for tropical species; often make the Earth's climate more arid on average, mainly by locking up more of the planet's water in ice and snow. The glaciation cycles of the current ice age are believed to have had only a very mild impact on biodiversity, so the mere existence of a significant cooling is not sufficient on its own to explain a mass extinction.
It has been suggested that global cooling caused or contributed to the End-Ordovician, Permian–Triassic, Late Devonian extinctions, and possibly others. Sustained global cooling is distinguished from the temporary climatic effects of flood basalt events or impacts.
This would have the opposite effects: expand the area available for tropical species; kill temperate species or force them to migrate towards the poles; possibly cause severe extinctions of polar species; often make the Earth's climate wetter on average, mainly by melting ice and snow and thus increasing the volume of the water cycle. It might also cause anoxic events in the oceans (see below).
Global warming as a cause of mass extinction is supported by several recent studies.
The most dramatic example of sustained warming is the Paleocene–Eocene Thermal Maximum, which was associated with one of the smaller mass extinctions. It has also been suggested to have caused the Triassic–Jurassic extinction event, during which 20% of all marine families became extinct. Furthermore, the Permian–Triassic extinction event has been suggested to have been caused by warming.
Clathrate gun hypothesis
Clathrates are composites in which a lattice of one substance forms a cage around another. Methane clathrates (in which water molecules are the cage) form on continental shelves. These clathrates are likely to break up rapidly and release the methane if the temperature rises quickly or the pressure on them drops quickly—for example in response to sudden global warming or a sudden drop in sea level or even earthquakes. Methane is a much more powerful greenhouse gas than carbon dioxide, so a methane eruption ("clathrate gun") could cause rapid global warming or make it much more severe if the eruption was itself caused by global warming.
The most likely signature of such a methane eruption would be a sudden decrease in the ratio of carbon-13 to carbon-12 in sediments, since methane clathrates are low in carbon-13; but the change would have to be very large, as other events can also reduce the percentage of carbon-13.
It has been suggested that "clathrate gun" methane eruptions were involved in the end-Permian extinction ("the Great Dying") and in the Paleocene–Eocene Thermal Maximum, which was associated with one of the smaller mass extinctions.
Anoxic events are situations in which the middle and even the upper layers of the ocean become deficient or totally lacking in oxygen. Their causes are complex and controversial, but all known instances are associated with severe and sustained global warming, mostly caused by sustained massive volcanism.
It has been suggested that anoxic events caused or contributed to the Ordovician–Silurian, late Devonian, Permian–Triassic and Triassic–Jurassic extinctions, as well as a number of lesser extinctions (such as the Ireviken, Mulde, Lau, Toarcian and Cenomanian–Turonian events). On the other hand, there are widespread black shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions.
The bio-availability of essential trace elements (in particular selenium) to potentially lethal lows has been shown to coincide with, and likely have contributed to, at least three mass extinction events in the oceans, i.e. at the end of the Ordovician, during the Middle and Late Devonian, and at the end of the Triassic. During periods of low oxygen concentrations very soluble selenate (Se6+) is converted into much less soluble selenide (Se2-), elemental Se and organo-selenium complexes. Bio-availability of selenium during these extinction events dropped to about 1% of the current oceanic concentration, a level that has been proven lethal to many extant organisms.
British oceanologist and atmospheric scientist, Andrew Watson, explained that, while the Holocene epoch exhibits many processes reminiscent of those that have contributed to past anoxic events, full-scale ocean anoxia would take "thousands of years to develop".
Hydrogen sulfide emissions from the seas
Kump, Pavlov and Arthur (2005) have proposed that during the Permian–Triassic extinction event the warming also upset the oceanic balance between photosynthesising plankton and deep-water sulfate-reducing bacteria, causing massive emissions of hydrogen sulfide which poisoned life on both land and sea and severely weakened the ozone layer, exposing much of the life that still remained to fatal levels of UV radiation.
Oceanic overturn is a disruption of thermo-haline circulation which lets surface water (which is more saline than deep water because of evaporation) sink straight down, bringing anoxic deep water to the surface and therefore killing most of the oxygen-breathing organisms which inhabit the surface and middle depths. It may occur either at the beginning or the end of a glaciation, although an overturn at the start of a glaciation is more dangerous because the preceding warm period will have created a larger volume of anoxic water.
Unlike other oceanic catastrophes such as regressions (sea-level falls) and anoxic events, overturns do not leave easily identified "signatures" in rocks and are theoretical consequences of researchers' conclusions about other climatic and marine events.
A nearby nova, supernova or gamma ray burst
A nearby gamma-ray burst (less than 6000 light-years away) would be powerful enough to destroy the Earth's ozone layer, leaving organisms vulnerable to ultraviolet radiation from the Sun. Gamma ray bursts are fairly rare, occurring only a few times in a given galaxy per million years. It has been suggested that a supernova or gamma ray burst caused the End-Ordovician extinction.
One theory is that periods of increased geomagnetic reversals will weaken Earth's magnetic field long enough to expose the atmosphere to the solar winds, causing oxygen ions to escape the atmosphere in a rate increased by 3–4 orders, resulting in a disastrous decrease in oxygen.
Movement of the continents into some configurations can cause or contribute to extinctions in several ways: by initiating or ending ice ages; by changing ocean and wind currents and thus altering climate; by opening seaways or land bridges which expose previously isolated species to competition for which they are poorly adapted (for example, the extinction of most of South America's native ungulates and all of its large metatherians after the creation of a land bridge between North and South America). Occasionally continental drift creates a super-continent which includes the vast majority of Earth's land area, which in addition to the effects listed above is likely to reduce the total area of continental shelf (the most species-rich part of the ocean) and produce a vast, arid continental interior which may have extreme seasonal variations.
Another theory is that the creation of the super-continent Pangaea contributed to the End-Permian mass extinction. Pangaea was almost fully formed at the transition from mid-Permian to late-Permian, and the "Marine genus diversity" diagram at the top of this article shows a level of extinction starting at that time which might have qualified for inclusion in the "Big Five" if it were not overshadowed by the "Great Dying" at the end of the Permian.
Many other hypotheses have been proposed, such as the spread of a new disease, or simple out-competition following an especially successful biological innovation. But all have been rejected, usually for one of the following reasons: they require events or processes for which there is no evidence; they assume mechanisms which are contrary to the available evidence; they are based on other theories which have been rejected or superseded.
Scientists have been concerned that human activities could cause more plants and animals to become extinct than any point in the past. Along with human-made changes in climate (see above), some of these extinctions could be caused by overhunting, overfishing, invasive species, or habitat loss. A study published in May 2017 in Proceedings of the National Academy of Sciences argued that a “biological annihilation” akin to a sixth mass extinction event is underway as a result of anthropogenic causes, such as over-population and over-consumption. The study suggested that as much as 50% of the number of animal individuals that once lived on Earth were already extinct, threatening the basis for human existence too.
Future biosphere extinction/sterilization
The eventual warming and expanding of the Sun, combined with the eventual decline of atmospheric carbon dioxide could actually cause an even greater mass extinction, having the potential to wipe out even microbes (in other words, the Earth is completely sterilized), where rising global temperatures caused by the expanding Sun will gradually increase the rate of weathering, which in turn removes more and more carbon dioxide from the atmosphere. When carbon dioxide levels get too low (perhaps at 50 ppm), all plant life will die out, although simpler plants like grasses and mosses can survive much longer, until CO
2 levels drop to 10 ppm.
With all photosynthetic organisms gone, atmospheric oxygen can no longer be replenished, and is eventually removed by chemical reactions in the atmosphere, perhaps from volcanic eruptions. Eventually the loss of oxygen will cause all remaining aerobic life to die out via asphyxiation, leaving behind only simple anaerobic prokaryotes. When the Sun becomes 10% brighter in about a billion years, Earth will suffer a moist greenhouse effect resulting in its oceans boiling away, while the Earth's liquid outer core cools due to the inner core's expansion and causes the Earth's magnetic field to shut down. In the absence of a magnetic field, charged particles from the Sun will deplete the atmosphere and further increase the Earth's temperature to an average of ~420 K (147 °C, 296 °F) in 2.8 billion years, causing the last remaining life on Earth to die out. This is the most extreme instance of a climate-caused extinction event. Since this will only happen late in the Sun's life, such will cause the final mass extinction in Earth's history (albeit a very long extinction event).
Effects and recovery
The impact of mass extinction events varied widely. After a major extinction event, usually only weedy species survive due to their ability to live in diverse habitats. Later, species diversify and occupy empty niches. Generally, it takes millions of years for biodiversity to recover after extinction events. In the most severe mass extinctions it may take 15 to 30 million years.
The worst event, the Permian–Triassic extinction, devastated life on earth, killing over 90% of species. Life seemed to recover quickly after the P-T extinction, but this was mostly in the form of disaster taxa, such as the hardy Lystrosaurus. The most recent research indicates that the specialized animals that formed complex ecosystems, with high biodiversity, complex food webs and a variety of niches, took much longer to recover. It is thought that this long recovery was due to successive waves of extinction which inhibited recovery, as well as prolonged environmental stress which continued into the Early Triassic. Recent research indicates that recovery did not begin until the start of the mid-Triassic, 4M to 6M years after the extinction; and some writers estimate that the recovery was not complete until 30M years after the P-T extinction, i.e. in the late Triassic. Subsequent to the P-T extinction, there was an increase in provincialization, with species occupying smaller ranges – perhaps removing incumbents from niches and setting the stage for an eventual rediversification.
The effects of mass extinctions on plants are somewhat harder to quantify, given the biases inherent in the plant fossil record. Some mass extinctions (such as the end-Permian) were equally catastrophic for plants, whereas others, such as the end-Devonian, did not affect the flora.
- Elvis taxon
- Endangered species
- Geologic time scale
- Global catastrophic risk
- Holocene extinction
- Human extinction
- Kačák Event
- Lazarus taxon
- List of impact craters on Earth
- List of largest volcanic eruptions
- List of possible impact structures on Earth
- Medea hypothesis
- Nature timeline
- Rare species
- Signor–Lipps effect
- Snowball Earth
- The Sixth Extinction: An Unnatural History (nonfiction book)
- Timeline of extinctions in the Holocene
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- Calculate the effects of an Impact
- Species Alliance (nonprofit organization producing a documentary about Mass Extinction titled "Call of Life: Facing the Mass Extinction)
- Interstellar Dust Cloud-induced Extinction Theory
- Sepkoski's Global Genus Database of Marine Animals – Calculate extinction rates for yourself! | 0.911617 | 3.655347 |
What Exactly Is Space Junk—And Can It Be Cleaned Up?
Litter isn't just a problem here on Earth.
By its very definition, space should have a lot of, well, space. And while it does, there’s also a lot of something else these days: junk. This interstellar litter isn’t naturally occurring. Like the junk that’s choking our oceans and overtaking our land, it was put there by humans and is the result of a very specific mix of innovation and carelessness. Space junk is out of sight so most people don’t even know it’s there…but that doesn’t mean it’s not a problem. These 50 powerful photos prove the Earth still needs our help.
So, what is space junk?
Space junk is just what it sounds like: things that people don’t want or use anymore, just in space. In this case, it’s mostly discarded satellites, related equipment, and bits and pieces of both that have collided and created even more debris. There are approximately 2,000 live satellites currently orbiting the Earth and 3,000 failed ones, and those numbers are growing every year, according to the European Space Agency (ESA). “[Governments, space agencies, and private companies] launch many satellites that we use for phone calls, TV signals, weather satellites, scientific instruments, military satellites, and so on,” says Geoffrey C. Clayton, PhD, a physics and astronomy professor at Louisiana State University. “When these satellites die and stop working, they become space junk.” But that’s not all—space junk is also made up of pieces of the rockets that launched the satellites in the first place, along with bits that have broken off after collisions in orbit.
All of these pieces and bits add up to a staggering number. “There are just under 130 million pieces of space junk in Earth’s orbit,” says Alex Mak, associate director of the University of Toledo Ritter Planetarium. “Of these, about 128 million are smaller than about one centimeter—that’s about the size of a bolt or a screw—and about 35,000 of them are larger than 10 centimeters. The estimated total mass is about 2,000 tons.” And the reason that so much of it is so tiny? “Imagine you launched a satellite on a 12-year mission, turned it off when it completed the mission, and then it eventually collided with something else up there—now it’s in 20,000 little pieces,” Mak explains.
Here are another 24 space facts you never learned in school.
Is space junk dangerous?
Let’s start with the good news: It’s unlikely that space junk would ever be a danger to us here on Earth. “Most space junk burns up in our atmosphere due to friction well before reaching the ground,” says Mak. “There is only a handful of reported incidents of people or property being hurt by space junk.” According to Aerospace.org, a person has less than one in a trillion chance of being harmed.
Now, the not-so-great news. Errant space junk poses a bigger danger to functioning satellites and other spacecraft. There are currently around 29,000 pieces of space debris in orbit that pose “a severe collision risk with satellites and space missions,” according to Universe Today. This is mainly because it isn’t simply floating in space—it’s hurtling forward at thousands of miles per hour, on a potential collision course with one another. “Even a small piece of metal like a bolt coming at the Space Station at thousands of miles an hour would be very dangerous,” Clayton says. Just how dangerous? NASA makes this startling comparison: “Averaging speeds of 22,000 mph, a 1-centimeter paint fleck is capable of inflicting the same damage as a 550-pound object traveling 60 miles per hour on earth. A 10-centimeter projectile would be comparable to 7 kilograms of TNT.”
Depending on the size of the space junk, a collision could shorten a satellite’s life or outright destroy it. That would lead to potential disruptions in service and incredibly costly replacements. Plus, as Mak ironically notes, when space junk damages or destroys satellites, it creates even more space junk and debris, further adding to these problems.
What other kinds of problems could space junk pose?
The main concern is safe space travel. “Some fear that the low Earth orbits (LEOs) may someday become so crowded with space junk as to make it impossible for crewed missions to safely penetrate it on the way to higher orbits or beyond,” says Mak. Keep in mind that the majority of space junk (around 70 percent) is in low Earth orbit, or at less than 1,200 miles above our planet’s surface. Various agencies, including NASA and NORAD, keep track of space junk (and are mostly concerned with the larger bits), by the way, while the Silicon Valley space-mapping company LeoLabs has recently started tracking small debris.
This problem could be exacerbated by something called the Kessler Syndrome. This phenomenon could occur as space junk increasingly collides with other space junk, causing “a runaway chain reaction of collisions and more debris,” according to NASA. At a certain point, the resulting “collision cascading” would render orbits unusable not just in terms of space missions but also for satellites.
Can space junk be cleaned up?
The short answer: Yes. The longer answer is that this isn’t easy. First, there’s already so much out there, and cleanup is a technologically difficult, costly, and dangerous prospect. Mak notes that research is being conducted with approaches such as lasers, space harpoons, and even nets to retrieve or destroy unneeded satellites. In late 2019, the ESA contracted the Swiss company ClearSpace Today to create “the world’s first debris-removing space mission.” Set to launch by 2025, the ClearSpace-1 mission entails having a four-armed robot latch onto space junk, then dive toward Earth’s atmosphere, where would both would burn up, according to CNN.
But cleanup isn’t enough, not over the long haul. There also needs to be a concerted effort to mitigate the creation of more space junk. One way to do this is by thinking ahead in terms of the satellite’s design and ultimate end game. “Some satellites are now launched with a small engine that allows them to alter their orbits after the mission to either burn up or move out of the traffic lanes into what is referred to as a graveyard zone,” says Mak. While the best methods for the disposal of satellites and assorted space junk remain to be seen, one thing is clear: We need to do something to ensure that both space travel and the technology we use on a daily basis stay viable.
Next, check out these NASA discoveries that changed science textbooks. | 0.828133 | 3.504145 |
Camera obscura (plural camerae obscurae or camera obscuras, from Latin camera obscūra, “dark chamber”), also referred to as pinhole image, is the natural optical phenomenon that occurs when an image of a scene at the other side of a screen (or, for instance, a wall) is projected through a small hole in that screen as a reversed and inverted image (left to right and upside down) on a surface opposite to the opening. The surroundings of the projected image have to be relatively dark for the image to be clear, so many historical camera obscura experiments were performed in dark rooms.
The term "camera obscura" also refers to constructions or devices that make use of the principle within a box, tent, or room. Camera obscuras with a lens in the opening have been used since the second half of the 16th century and became popular as an aid for drawing and painting. The camera obscura box was developed further into the photographic camera in the first half of the 19th century when camera obscura boxes were used to expose light-sensitive materials to the projected image.
The camera obscura was used as a means to study eclipses without the risk of damaging the eyes by looking into the sun directly. As a drawing aid, the camera obscura allowed tracing the projected image to produce a highly accurate representation, especially appreciated as an easy way to achieve a proper graphical perspective.
Before the term "camera obscura" was first used in 1604, many others are attested: "cubiculum obscurum", "cubiculum tenebricosum", "conclave obscurum" and "locus obscurus".
A camera obscura device without a lens but with a very small hole is sometimes referred to as a "pinhole camera", although this more often refers to simple (home-made) lens-less cameras in which photographic film or photographic paper is used.
Rays of light travel in straight lines and change when they are reflected and partly absorbed by an object, retaining information about the color and brightness of the surface of that object. Lit objects reflect rays of light in all directions. A small enough opening in a screen only lets through rays that travel directly from different points in the scene on the other side, and these rays form an image of that scene when they are collected on a surface opposite from the opening.
The human eye (as well as those of other animals including birds, fish, reptiles etc.) works much like a camera obscura with an opening (pupil), a biconvex lens and a surface where the image is formed (retina).
A camera obscura device consists of a box, tent, or room with a small hole in one side. Light from an external scene passes through the hole and strikes a surface inside, where the scene is reproduced, inverted, (thus upside-down) and reversed (left to right), but with color and perspective preserved.
In order to produce a reasonably clear projected image, the aperture has to be about 1/100th the distance to the screen, or less.
As the pinhole is made smaller, the image gets sharper, but the projected image becomes dimmer. With too small a pinhole, however, the sharpness worsens, due to diffraction.
If the image is caught on a semi-transparent screen, it can be viewed from the back so that it is no longer reversed (but still upside-down).
Using mirrors it is possible to project a right-side-up image. The projection can also be diverted onto a horizontal surface (e.g., a table). The 18th-century overhead version in tents used mirrors inside a kind of periscope on the top of the tent .
The box-type camera obscura often has an angled mirror projecting an upright image onto tracing paper placed on the glass top. Although the image is viewed from the back, it is now reversed by the mirror.
Prehistory to 500 BCE: Possible inspiration for prehistoric art and possible use in religious ceremonies, gnomons
There are theories that occurrences of camera obscura effects (through tiny holes in tents or in screens of animal hide) inspired paleolithic cave paintings. Distortions in the shapes of animals in many paleolithic cave artworks might be inspired by distortions seen when the surface on which an image was projected was not straight or not in the right angle. It is also suggested that camera obscura projections could have played a role in Neolithic structures.
Perforated gnomons projecting a pinhole image of the sun were described in the Chinese Zhoubi Suanjing writings (1046 BCE–256 BCE with material added until circa 220 CE). The location of the bright circle can be measured to tell the time of day and year. In Arab and European cultures its invention was much later attributed to Egyptian astronomer and mathematician Ibn Yunus around 1000 CE.
500 BCE to 500 CE: Earliest written observations
The earliest known written record of the camera obscura is found in the Chinese text called Mozi, dated to the 4th century BCE, traditionally ascribed to and named for Mozi (circa 470 BCE-circa 391 BCE), a Han Chinese philosopher and the founder of Mohist School of Logic. These writings explain how the image in a "collecting-point" or "treasure house"[note 1] is inverted by an intersecting point (a pinhole) that collects the (rays of) light. Light coming from the foot of an illuminated person would partly be hidden below (i.e., strike below the pinhole) and partly form the top part of the image. Rays from the head would partly be hidden above (i.e., strike above the pinhole) and partly form the lower part of the image. This is a remarkably early correct description of the camera obscura; there are no other examples known that are dated before the 11th century.
Why is it that when the sun passes through quadri-laterals, as for instance in wickerwork, it does not produce a figure rectangular in shape but circular?
and further on:
"Why is it that an eclipse of the sun, if one looks at it through a sieve or through leaves, such as a plane-tree or other broadleaved tree, or if one joins the fingers of one hand over the fingers of the other, the rays are crescent-shaped where they reach the earth? Is it for the same reason as that when light shines through a rectangular peep-hole, it appears circular in the form of a cone?"
Many philosophers and scientists of the Western world would ponder this question before it became accepted that the circular and crescent-shapes described in this "problem" were actually pinhole image projections of the sun. Although a projected image will have the shape of the aperture when the light source, aperture and projection plane are close together, the projected image will have the shape of the light source when they are further apart.
In his book Optics (circa 300 BCE, surviving in later manuscripts from around 1000 CE), Euclid proposed mathematical descriptions of vision with "lines drawn directly from the eye pass through a space of great extent" and "the form of the space included in our vision is a cone, with its apex in the eye and its base at the limits of our vision." Later versions of the text, like Ignazio Danti's 1573 annotated translation, would add a description of the camera obscura principle to demonstrate Euclid's ideas.
500 to 1000: Earliest experiments, study of light
In the 6th century, the Byzantine-Greek mathematician and architect Anthemius of Tralles (most famous as a co-architect of the Hagia Sophia), experimented with effects related to the camera obscura. Anthemius had a sophisticated understanding of the involved optics, as demonstrated by a light-ray diagram he constructed in 555 CE.
In the 10th century Yu Chao-Lung supposedly projected images of pagoda models through a small hole onto a screen to study directions and divergence of rays of light.
1000 to 1400: Optical and astronomical tool, entertainment
Arab physicist Ibn al-Haytham (known in the West by the Latinised Alhazen) (965–1039) extensively studied the camera obscura phenomenon in the early 11th century. He provided the first competent geometrical and quantitative descriptions of the phenomenon and must have understood the relationship between the focal point and the pinhole,
Evidence that light and color do not mingle in air or (other) transparent bodies is (found in) the fact that, when several candles are at various distinct locations in the same area, and when they all face a window that opens into a dark recess, and when there is a white wall or (other white) opaque body in the dark recess facing that window, the (individual) lights of those candles appear individually upon that body or wall according to the number of those candles; and each of those lights (spots of light) appears directly opposite one (particular) candle along a straight line passing through that window. Moreover, if one candle is shielded, only the light opposite that candle is extinguished, but if the shielding object is lifted, the light will return.
He described a "dark chamber" and did a number of trials of experiments with small pinholes and light passing through them. This experiment consisted of three candles in a row and seeing the effects on the wall after placing a cutout between the candles and the wall.
The image of the sun at the time of the eclipse, unless it is total, demonstrates that when its light passes through a narrow, round hole and is cast on a plane opposite to the hole it takes on the form of a moon-sickle. The image of the sun shows this peculiarity only when the hole is very small. When the hole is enlarged, the picture changes, and the change increases with the added width. When the aperture is very wide, the sickle-form image will disappear, and the light will appear round when the hole is round, square if the hole is square, and if the shape of the opening is irregular, the light on the wall will take on this shape, provided that the hole is wide and the plane on which it is thrown is parallel to it.
Ibn al-Haytham also analyzed the rays of sunlight and concluded that they make a conic shape where they meet at the hole, forming another conic shape reverse to the first one from the hole to the opposite wall in the dark room. Ibn al-Haytham's writings on optics became very influential in Europe through Latin translations since circa 1200. Among those he inspired were Witelo, John Peckham, Roger Bacon, Leonardo Da Vinci, René Descartes and Johannes Kepler.
In his 1088 book, Dream Pool Essays, the Song Dynasty Chinese scientist Shen Kuo (1031–1095) compared the focal point of a concave burning-mirror and the "collecting" hole of camera obscura phenomena to an oar in a rowlock to explain how the images were inverted:
"When a bird flies in the air, its shadow moves along the ground in the same direction. But if its image is collected (shu)(like a belt being tightened) through a small hole in a window, then the shadow moves in the direction opposite of that of the bird.[...] This is the same principle as the burning-mirror. Such a mirror has a concave surface, and reflects a finger to give an upright image if the object is very near, but if the finger moves farther and farther away it reaches a point where the image disappears and after that the image appears inverted. Thus the point where the image disappears is like the pinhole of the window. So also the oar is fixed at the rowlock somewhere at its middle part, constituting, when it is moved, a sort of 'waist' and the handle of the oar is always in the position inverse to the end (which is in the water)."
Shen Kuo also responded to a statement of Duan Chengshi in Miscellaneous Morsels from Youyang written in about 840 that the inverted image of a Chinese pagoda tower beside a seashore, was inverted because it was reflected by the sea: "This is nonsense. It is a normal principle that the image is inverted after passing through the small hole."
English philosopher and Franciscan friar Roger Bacon (c. 1219/20 – c. 1292) falsely stated in his De Multiplicatione Specerium (1267) that an image projected through a square aperture was round because light would travel in spherical waves and therefore assumed its natural shape after passing through a hole. He is also credited with a manuscript that advised to study solar eclipses safely by observing the rays passing through some round hole and studying the spot of light they form on a surface.
A picture of a three-tiered camera obscura (see illustration) has been attributed to Bacon, but the source for this attribution is not given. A very similar picture is found in Athanasius Kircher's Ars Magna Lucis et Umbrae (1646).
Polish friar, theologian, physicist, mathematician and natural philosopher Erazmus Ciołek Witelo (also known as Vitello Thuringopolonis and by many different spellings of the name "Witelo") wrote about the camera obscura in his very influential treatise Perspectiva (circa 1270–1278), which was largely based on Ibn al-Haytham's work.
English archbishop and scholar John Peckham (circa 1230 – 1292) wrote about the camera obscura in his Tractatus de Perspectiva (circa 1269–1277) and Perspectiva communis (circa 1277–79), falsely arguing that light gradually forms the circular shape after passing through the aperture. His writings were influenced by Roger Bacon.
French astronomer Guillaume de Saint-Cloud suggested in his 1292 work Almanach Planetarum that the eccentricity of the sun could be determined with the camera obscura from the inverse proportion between the distances and the apparent solar diameters at apogee and perigee.
Kamāl al-Dīn al-Fārisī (1267–1319) described in his 1309 work Kitab Tanqih al-Manazir (The Revision of the Optics) how he experimented with a glass sphere filled with water in a camera obscura with a controlled aperture and found that the colors of the rainbow are phenomena of the decomposition of light.
French Jewish philosopher, mathematician, physicist and astronomer/astrologer Levi ben Gershon (1288–1344) (also known as Gersonides or Leo de Balneolis) made several astronomical observations using a camera obscura with a Jacob's staff, describing methods to measure the angular diameters of the sun, the moon and the bright planets Venus and Jupiter. He determined the eccentricity of the sun based on his observations of the summer and winter solstices in 1334. Levi also noted how the size of the aperture determined the size of the projected image. He wrote about his findings in Hebrew in his treatise Sefer Milhamot Ha-Shem (The Wars of the Lord) Book V Chapters 5 and 9.
1450 to 1600: Depiction, lenses, drawing aid, mirrors
Italian polymath Leonardo da Vinci (1452–1519), familiar with the work of Alhazen in Latin translation, and after an extensive study of optics and human vision, wrote the oldest known clear description of the camera obscura in mirror writing in a notebook in 1502, later published in the collection Codex Atlanticus (translated from Latin):
If the facade of a building, or a place, or a landscape is illuminated by the sun and a small hole is drilled in the wall of a room in a building facing this, which is not directly lighted by the sun, then all objects illuminated by the sun will send their images through this aperture and will appear, upside down, on the wall facing the hole. You will catch these pictures on a piece of white paper, which placed vertically in the room not far from that opening, and you will see all the above-mentioned objects on this paper in their natural shapes or colors, but they will appear smaller and upside down, on account of crossing of the rays at that aperture. If these pictures originate from a place which is illuminated by the sun, they will appear colored on the paper exactly as they are. The paper should be very thin and must be viewed from the back.
These descriptions, however, would remain unknown until Venturi deciphered and published them in 1797.
Da Vinci was clearly very interested in the camera obscura: over the years he drew circa 270 diagrams of the camera obscura in his notebooks . He systematically experimented with various shapes and sizes of apertures and with multiple apertures (1, 2, 3, 4, 8, 16, 24, 28 and 32). He compared the working of the eye to that of the camera obscura and seemed especially interested in its capability of demonstrating basic principles of optics: the inversion of images through the pinhole or pupil, the non-interference of images and the fact that images are "all in all and all in every part".
The oldest known published drawing of a camera obscura is found in Dutch physician, mathematician and instrument maker Gemma Frisius’ 1545 book De Radio Astronomica et Geometrica, in which he described and illustrated how he used the camera obscura to study the solar eclipse of 24 January 1544
Italian polymath Gerolamo Cardano described using a glass disc – probably a biconvex lens – in a camera obscura in his 1550 book De subtilitate, vol. I, Libri IV. He suggested to use it to view "what takes place in the street when the sun shines" and advised to use a very white sheet of paper as a projection screen so the colours wouldn't be dull.
Sicilian mathematician and astronomer Francesco Maurolico (1494–1575) answered Aristotle's problem how sunlight that shines through rectangular holes can form round spots of light or crescent-shaped spots during an eclipse in his treatise Photismi de lumine et umbra (1521–1554). However this wasn't published before 1611, after Johannes Kepler had published similar findings of his own.
Italian polymath Giambattista della Porta described the camera obscura, which he called "obscurum cubiculum", in the 1558 first edition of his book series Magia Naturalis. He suggested to use a convex mirror to project the image onto paper and to use this as a drawing aid. Della Porta compared the human eye to the camera obscura: "For the image is let into the eye through the eyeball just as here through the window". The popularity of Della Porta's books helped spread knowledge of the camera obscura.
In his 1567 work La Pratica della Perspettiva Venetian nobleman Daniele Barbaro (1513-1570) described using a camera obscura with a biconvex lens as a drawing aid and points out that the picture is more vivid if the lens is covered as much as to leave a circumference in the middle.
In his influential and meticulously annotated Latin edition of the works of Ibn al-Haytham and Witelo Opticae thesauru (1572) German mathematician Friedrich Risner proposed a portable camera obscura drawing aid; a lightweight wooden hut with lenses in each of its four walls that would project images of the surroundings on a paper cube in the middle. The construction could be carried on two wooden poles. A very similar setup was illustrated in 1645 in Athanasius Kircher's influential book Ars Magna Lucis Et Umbrae.
Around 1575 Italian Dominican priest, mathematician, astronomer, and cosmographer Ignazio Danti designed a camera obscura gnomom and a meridian line for the Basilica of Santa Maria Novella, Florence and he later had a massive gnomon built in the San Petronio Basilica in Bologna. The gnomon was used to study the movements of the sun during the year and helped in determining the new Gregorian calendar for which Danti took place in the commission appointed by Pope Gregorius XIII and instituted in 1582.
In his 1585 book Diversarum Speculationum Mathematicarum Venetian mathematician Giambattista Benedetti proposed to use a mirror in a 45-degree angle to project the image upright. This leaves the image reversed, but would become common practice in later camera obscura boxes.
Giambattista della Porta added a "lenticular crystal" or biconvex lens to the camera obscura description in the 1589 second edition of Magia Naturalis. He also described use of the camera obscura to project hunting scenes, banquets, battles, plays, or anything desired on white sheets. Trees, forests, rivers, mountains "that are really so, or made by Art, of Wood, or some other matter" could be arranged on a plain in the sunshine on the other side of the camera obscura wall. Little children and animals (for instance handmade deer, wild boars, rhinos, elephants, and lions) could perform in this set. "Then, by degrees, they must appear, as coming out of their dens, upon the Plain: The Hunter he must come with his hunting Pole, Nets, Arrows, and other necessaries, that may represent hunting: Let there be Horns, Cornets, Trumpets sounded: those that are in the Chamber shall see Trees, Animals, Hunters Faces, and all the rest so plainly, that they cannot tell whether they be true or delusions: Swords drawn will glister in at the hole, that they will make people almost afraid." Della Porta claimed to have shown such spectacles often to his friends. They admired it very much and could hardly be convinced by Della Porta's explanations that what they had seen was really an optical trick.
1600 to 1650: Name coined, camera obscura telescopy, portable drawing aid in tents and boxes
The earliest use of the term "camera obscura" is found in the 1604 book Ad Vitellionem Paralipomena by German mathematician, astronomer, and astrologer Johannes Kepler. Kepler discovered the working of the camera obscura by recreating its principle with a book replacing a shining body and sending threads from its edges through a many-cornered aperture in a table onto the floor where the threads recreated the shape of the book. He also realized that images are "painted" inverted and reversed on the retina of the eye and figured that this is somehow corrected by the brain. In 1607, Kepler studied the sun in his camera obscura and noticed a sunspot, but he thought it was Mercury transiting the sun. In his 1611 book Dioptrice, Kepler described how the projected image of the camera obscura can be improved and reverted with a lens. It is believed he later used a telescope with three lenses to revert the image in the camera obscura.
In 1611, Frisian/German astronomers David and Johannes Fabricius (father and son) studied sunspots with a camera obscura, after realizing looking at the sun directly with the telescope could damage their eyes. They are thought to have combined the telescope and the camera obscura into camera obscura telescopy.
In 1612, Italian mathematician Benedetto Castelli wrote to his mentor, the Italian astronomer, physicist, engineer, philosopher, and mathematician Galileo Galilei about projecting images of the sun through a telescope (invented in 1608) to study the recently discovered sunspots. Galilei wrote about Castelli's technique to the German Jesuit priest, physicist, and astronomer Christoph Scheiner.
From 1612 to at least 1630, Christoph Scheiner would keep on studying sunspots and constructing new telescopic solar-projection systems. He called these "Heliotropii Telioscopici", later contracted to helioscope. For his helioscope studies, Scheiner built a box around the viewing/projecting end of the telescope, which can be seen as the oldest known version of a box-type camera obscura. Scheiner also made a portable camera obscura.
In his 1613 book Opticorum Libri Sex Belgian Jesuit mathematician, physicist, and architect François d'Aguilon described how some charlatans cheated people out of their money by claiming they knew necromancy and would raise the specters of the devil from hell to show them to the audience inside a dark room. The image of an assistant with a devil's mask was projected through a lens into the dark room, scaring the uneducated spectators.
By 1620 Kepler used a portable camera obscura tent with a modified telescope to draw landscapes. It could be turned around to capture the surroundings in parts.
Dutch inventor Cornelis Drebbel is thought to have constructed a box-type camera obscura which corrected the inversion of the projected image. In 1622, he sold one to the Dutch poet, composer, and diplomat Constantijn Huygens who used it to paint and recommended it to his artist friends. Huygens wrote to his parents (translated from French):
I have at home Drebbel's other instrument, which certainly makes admirable effects in painting from reflection in a dark room; it is not possible for me to reveal the beauty to you in words; all painting is dead by comparison, for here is life itself or something more elevated if one could articulate it. The figure and the contour and the movements come together naturally therein and in a grandly pleasing fashion.
German Orientalist, mathematician, inventor, poet, and librarian Daniel Schwenter wrote in his 1636 book Deliciae Physico-Mathematicae about an instrument that a man from Pappenheim had shown him, which enabled movement of a lens to project more from a scene through the camera obscura. It consisted of a ball as big as a fist, through which a hole (AB) was made with a lens attached on one side (B). This ball was placed inside two-halves of part of a hollow ball that were then glued together (CD), in which it could be turned around. This device was attached to a wall of the camera obscura (EF). This universal joint mechanism was later called a scioptric ball.
In his 1637 book Dioptrique French philosopher, mathematician and scientist René Descartes suggested placing an eye of a recently dead man (or if a dead man was unavailable, the eye of an ox) into an opening in a darkened room and scraping away the flesh at the back until one could see the inverted image formed on the retina.
Italian Jesuit philosopher, mathematician, and astronomer Mario Bettini wrote about making a camera obscura with twelve holes in his Apiaria universae philosophiae mathematicae (1642). When a foot soldier would stand in front of the camera, a twelve-person army of soldiers making the same movements would be projected.
French mathematician, Minim friar, and painter of anamorphic art Jean-François Nicéron (1613–1646) wrote about the camera obscura with convex lenses. He explained how the camera obscura could be used by painters to achieve perfect perspective in their work. He also complained how charlatans abused the camera obscura to fool witless spectators and make them believe that the projections were magic or occult science. These writings were published in a posthumous version of La Perspective Curieuse (1652).
1650 to 1800: Introduction of the magic lantern, popular portable box-type drawing aid, painting aid
The use of the camera obscura to project special shows to entertain an audience seems to have remained very rare. A description of what was most likely such a show in 1656 in France, was penned by the poet Jean Loret. The Parisian society were presented with upside-down images of palaces, ballet dancing and battling with swords. The performance was silent and Loret was surprised that all the movements made no sound. Loret felt somewhat frustrated that he did not know the secret that made this spectacle possible. There are several clues that this was a camera obscura show, rather than a very early magic lantern show, especially in the upside-down image and the energetic movements.
German Jesuit scientist Gaspar Schott heard from a traveler about a small camera obscura device he had seen in Spain, which one could carry under one arm and could be hidden under a coat. He then constructed his own sliding box camera obscura, which could focus by sliding a wooden box part fitted inside another wooden box part. He wrote about this in his 1657 Magia universalis naturæ et artis (volume 1 – book 4 "Magia Optica" pages 199–201).
By 1659 the magic lantern was introduced and partly replaced the camera obscura as a projection device, while the camera obscura mostly remained popular as a drawing aid. The magic lantern can be seen as a development of the (box-type) camera obscura device.
The 17th century Dutch Masters, such as Johannes Vermeer, were known for their magnificent attention to detail. It has been widely speculated that they made use of the camera obscura, but the extent of their use by artists at this period remains a matter of fierce contention, recently revived by the Hockney–Falco thesis.
German philosopher Johann Sturm published an illustrated article about the construction of a portable camera obscura box with a 45° mirror and an oiled paper screen in the first volume of the proceedings of the Collegium Curiosum, Collegium Experimentale, sive Curiosum (1676).
Johann Zahn's Oculus Artificialis Teledioptricus Sive Telescopium, published in 1685, contains many descriptions, diagrams, illustrations and sketches of both the camera obscura and the magic lantern. A hand-held device with a mirror-reflex mechanism was first proposed by Johann Zahn in 1685, a design that would later be used in photographic cameras.
The scientist Robert Hooke presented a paper in 1694 to the Royal Society, in which he described a portable camera obscura. It was a cone-shaped box which fit onto the head and shoulders of its user.
From the beginning of the 18th century, craftsmen and opticians would make camera obscura devices in the shape of books, which were much appreciated by lovers of optical devices.
By the 18th century, following developments by Robert Boyle and Robert Hooke, more easily portable models in boxes became available. These were extensively used by amateur artists while on their travels, but they were also employed by professionals, including Paul Sandby and Joshua Reynolds, whose camera (disguised as a book) is now in the Science Museum in London. Such cameras were later adapted by Joseph Nicephore Niepce, Louis Daguerre and William Fox Talbot for creating the first photographs.
Role in the modern age
While the technical principles of the camera obscura have been known since antiquity, the broad use of the technical concept in producing images with a linear perspective in paintings, maps, theatre setups, and architectural, and, later, photographic images and movies started in the Western Renaissance and the scientific revolution. While, e.g., Alhazen (Ibn al-Haytham) had already observed an optical effect and developed a state of the art theory of the refraction of light, he was less interested to produce images with it (compare Hans Belting 2005); the society he lived in was even hostile (compare Aniconism in Islam) towards personal images. Western artists and philosophers used the Arab findings in new frameworks of epistemic relevance. E.g. Leonardo da Vinci used the camera obscura as a model of the eye, René Descartes for eye and mind and John Locke started to use the camera obscura as a metaphor of human understanding per se. The modern use of the camera obscura as an epistemic machine had important side effects for science. While the use of the camera obscura has dwindled, for those who are interested in making one it only requires a few items including: a box, tracing paper, tape, foil, a box cutter, a pencil and a blanket to keep out the light.
In 1827, critic Vergnaud complained about the use of camera obscura for many painting at that year's Salon exhibition in Paris: "Is the public to blame, the artists, or the jury, when history paintings, already rare, are sacrificed to genre painting, and what genre at that!... that of the camera obscura." (translated from French)
A freestanding room-sized camera obscura at the University of North Carolina at Chapel Hill. A pinhole can be seen to the left of the door.
A freestanding room-sized camera obscura in the shape of a camera. Cliff House, San Francisco
|Name||City or Town||Country||Comment||WWW Links|
|Astronomy Centre||Todmorden||England||80 inches (200 cm) table, 40° field of view, horizontal rotation 360°, vertical adjustment ±15°||Equipment on site#Camera obscura|
|Bristol Observatory||Bristol||England||View of Clifton Suspension Bridge||Clifton Observatory|
|Buzza Tower||Hugh Town, Isles of Scilly||England||View of the Isles of Scilly||Scilly Camera Obscura|
|Cheverie Camera Obscura||Chéverie, Nova Scotia||Canada||View of the Bay of Fundy||Cheverie Camera Obscura|
|Photographer's Gallery||London||England||View of Ramillies St||Photographer's Gallery|
|Constitution Hill||Aberystwyth||Wales||14-inch (356 mm) lens, which is claimed to be the largest in the world||Cliff Railway and Camera Obscura, Aberystwyth|
|Camera Obscura, and World of Illusions||Edinburgh||Scotland||Top of Royal Mile, just below Edinburgh Castle. Fine views of the city||Edinburgh's Camera Obscura|
|Camera Obscura (Greenwich)||Greenwich||England||Royal Observatory, Meridian Courtyard||http://www.rmg.co.uk/see-do/we-recommend/attractions/camera-obscura/|
|Camera Obscura and museum "Prehistory of Film"||Mülheim||Germany||Claimed to be the biggest "walk-in" Camera Obscura in the world. Installed in Broich Watertower in 1992||https://web.archive.org/web/20160921065718/http://www.camera-obscura-muelheim.de/cms/the_camera.html|
|Dumfries Museum||Dumfries||Scotland||In a converted windmill tower. Claims to be oldest working example in the world|||
|Foredown Tower||Portslade, Brighton||England||One of only two operational camera obscuras in the south of England|
|Grand Union Camera Obscura||Douglas||Isle of Man||On Douglas Head. Unique Victorian tourist attraction with eleven lenses||Visit Isle of Man|
|Camera Obscura (Giant Camera)||Golden Gate National Recreation Area, San Francisco, California||United States||Adjacent to the Cliff House below Sutro Heights Park, with views of the Pacific Ocean. In the Sutro Historic District, and on the National Register of Historic Places.||Giant Camera|
|Santa Monica Camera Obscura||Santa Monica, California||United States||In Palisades Park overlooking Santa Monica Beach, Santa Monica Pier, and the Pacific Ocean. Built in 1898.||Atlas Obscura|
|Long Island's Camera Obscura||Greenport, Suffolk County, New York||United States||In Mitchell Park overlooking the Peconic Bay and Shelter Island, New York. Built in 2004.||Long Island Camera Obscura|
|Griffith Observatory||Los Angeles, California||United States||Slowly rotates and gives a panoramic view of the Los Angeles Basin.||Griffith Park Camera Obscura|
|The Exploratorium's Bay Observatory Terrace||San Francisco, California||United States||Offers a view of San Francisco Bay, Treasure Island, and the Bay Bridge|||
|Cámara Oscura||Havana||Cuba||Located in Plaza Vieja, Havana. Offers a view of Old Havana|
|Cloud Chamber for the Trees and Sky||Raleigh, North Carolina||United States||On the campus of the North Carolina Museum of Art||http://ncartmuseum.org/art/detail/cloud_chamber_for_the_trees_and_sky/|
|Camera Obscura||Grahamstown||South Africa||In the Observatory Museum||http://www.sa-venues.com/things-to-do/easterncape/observatory-museum/|
|Kirriemuir Camera Obscura||Kirriemuir||Scotland||Offers a view of Kirriemuir and the surrounding glens.|
|Torre Tavira||Cadiz||Spain||Offers a view of the old town||https://www.torretavira.com/en/visiting-the-tavira-tower/|
|Camera Obscura, Tavira||Tavira||Portugal||Uses a repurposed water tower for the viewing room.||http://family.portugalconfidential.com/camera-obscura-in-the-tower-of-tavira/|
|Camera Obscura, Lisbon||Lisbon||Portugal||Installed in the Castle of Saint George, Lisbon.|
- In the 2003 film Girl with a Pearl Earring, Colin Firth's character uses a camera obscura to help him paint. The scene begins around 32 minutes into the film when he shows Scarlett Johansson's character that what she sees inside of the box is an image or a "picture made of light".
- The 1966 film Andrei Rublev by Russian director Tarkovsky includes a scene with a pinhole image via a hole in the door of a medieval room.
- In the 1997 film Addicted to Love Matthew Broderick's character sets up a camera obscura in an abandoned building opposite his ex-girlfriend's apartment.
- Camera Obscura is the title of several novels: an 1839 Dutch novel by Nicolaas Beets, the 1932 Russian novel by Vladimir Nabokov known in English as Laughter in the Dark, a 2002 novel by Lloyd Rose in the BBC Books Doctor Who series, a 2006 Slovenian novel by Nejc Gazvoda and a 2011 novel by Israeli-born writer Lavie Tidhar
- Camera Obscura was the name of an English new wave/synthpop duo formed in 1982.
- Camera Obscura is the title of a 1985 album by German singer Nico.
- Camera Obscura is the name of a Scottish indie pop band formed in 1996.
- Camera Obscura is the title of a track on the 2000 album The Screen Behind the Mirror by German musical project Enigma.
- In the Fatal Frame video game series, started in 2001, the Camera Obscura can be used to damage and pacify attacking ghosts.
- In A Matter of Life and Death 1946, Dr. Frank Reeves, Roger Livesey, uses a camera obscura to view the village around his home.
- A camera obscura is featured prominently in "Death in a Chocolate Box", episode eight in series 10 of the UK police procedural Midsomer Murders.
- In the 2017 film Wonder, Auggie Pullman creates a camera obscura which wins first place at his school science fair.
- Bonnington Pavilion – the first Scottish Camera Obscura, dating from 1708
- Black mirror
- Bristol Observatory
- Camera lucida
- History of cinema
- Hockney–Falco thesis
- Pepper's ghost
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it seems that, like Shen Kua, he had predecessors in its study, since he did not claim it as any new finding of his own. But his treatment of it was competently geometrical and quantitative for the first time.
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The genius of Shen Kua's insight into the relation of focal point and pinhole can better be appreciated when we read in Singer that this was first understood in Europe by Leonardo da Vinci (+ 1452 to + 1519), almost five hundred years later. A diagram showing the relation occurs in the Codice Atlantico, Leonardo thought that the lens of the eye reversed the pinhole effect, so that the image did not appear inverted on the retina; though in fact it does. Actually, the analogy of focal-point and pin-point must have been understood by Ibn al-Haitham, who died just about the time when Shen Kua was born.
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- Media related to Camera obscura at Wikimedia Commons | 0.844681 | 3.346474 |
When you think of animals that have been sent to space, what comes to mind? Humans of course, but maybe you also remember the first “higher primate” in space1, Ham the Chimpanzee (or Enos, the first primate to orbit the Earth). Or perhaps the dog Laika — the first animal to orbit the Earth2 — comes to mind. And of course, we’ve sent mice and insects and other organisms into space in the name of research as well.
What probably doesn’t immediately come to mind, however, are tortoises. But tortoises were exactly what the Soviets decided should be among the first animals to circle the Moon.
The Soviet’s Zond (translated: probe) program consisted of two distinct objectives. The first missions, Zond 1, 2, and 3, utilized the 3MV3 planetary probe and were designed to explore Mars and Venus. Zond 1 and 2 failed en route to their respective objective targets, while Zond 3 captured photos from the far side of the Moon on its way out on a Mars trajectory, though the timing wasn’t such that it would encounter the red planet.
Fueled by the “Moon race” between the United States and the Soviets, the following Zond missions employed the Soyuz 7K-L1 spacecraft and were all focused on the Moon. Zond 4 reached a distance of approximately 300,000km (186,411 miles) from the Earth before returning. Its trajectory took it on a course 180-degrees away from the Moon, and there are conflicting stories as to whether or not the Soviets intentionally sent the spacecraft on that course, or if there was a malfunction. It re-entered Earth’s atmosphere out of the Soviet’s control and was remotely detonated at an altitude of 10-15km (6-9 miles), and a couple of hundred kilometers off of the coast of Africa.
Finally, Zond 5 launched on September 14, 1968. Aimed for the Moon, it contained a biological payload including wine flies, meal worms, plants, bacteria, and… two Russian tortoises. Zond 5 took a circumlunar trajectory, which means it looped around the Moon, but didn’t go into multiple orbits around it. Think of a big, lop-sided, figure-eight, with the Earth within a large loop and the Moon within a smaller one. This is very similar to the emergency trajectory that Apollo 13 took, following the disastrous malfunctions that plagued that craft on its way to the Moon.
The tortoises spent a week in space before splashing down in the Indian Ocean. The tortoises reportedly lost 10% of their body weight during their trip, but remained active and showed no loss of appetite. These tortoises became among the first Earthly lifeforms to complete a lunar flyby and return safely to Earth, proving it possible, and paving the way for future vertebrates such as Neil Armstrong and Buzz Aldrin.
Zond 5 wasn’t the end of the line for our half-shelled cosmonaut friends; Zond 7 and Zond 8 each carried multiple tortoises. Tortoises then came out of a 5-year retirement to be sent up again, aboard Soyuz 20 in 1975. This time, they were in for the long-haul, spending a total of 90.5 days in space and consequently breaking the record for the longest amount of time an animal had spent in space. Finally, in February of 2010, the Iranian Space Agency sent up their first biological payload into a sub-orbital flight; aboard were two turtles.4,5
So now you know the story of tortoises in space. From being among the first animals to take a trip around the Moon, to breaking records for time in space, tortoises are very much a part of “animaled” spaceflight. Like all of the others that have made Earth’s space programs successful, I tip my hat to the shelled reptiles for their contributions.
- Monkeys had gone into space as early as the late 1940’s, though it wasn’t until 1957 when Laika, the dog, became the first animal to orbit the Earth. ↩
- And unfortunately, Laika was the first animal to die in orbit, as well. ↩
- Third-generation, Mars/Venus ↩
- Yes, I’m aware that there is a difference between tortoises and turtles, but the definitions can actually vary depending on which country you’re from. I haven’t been able to find out the specific species of the Testudine Iran sent to space, so they may or may not be tortoises. To be mentioned in this article, I say close enough! ↩
- And apparently, at least 64 people are outraged enough by this that they’ve “Liked” a “Save Turtles From Iran’s Space Program” Facebook page. ↩ | 0.822041 | 3.485688 |
Today’s technology can do amazing things.
Proof of how much mankind has progressed in the last few decades can be found on the surface of Mars, where NASA’s very own Alien rovers explore the red planet’s surface, searching for traces of life, and what Mars was like billions of years ago.
NASA’s Curiosity Rover—a car-sized rover—is part of NASA’s Mars Science Laboratory mission (MSL).
Curiosity was launched from Cape Canaveral on November 26, 2011, at 15:02 UTC aboard the MSL spacecraft and landed on Aeolis Palus in Gale Crater on Mars on August 6, 2012, 05:17 UTC.
The rover’s missions are to investigate the Martian climate and geology; assess whether the selected field site inside Gale Crater has ever offered environmental conditions favorable for microbial life, including investigation of the role of water; and planetary habitability studies in preparation for human exploration.
The Rover is used as the basis for the planet Mars 2020 Rover. Curiosity has been on Mars for 1950 Sols, or 2003 days as of January 30.
During more than 2000 days the Rover has spent exploring the Martian surface, it has snapped a great number of breathtaking images that have shown us how similar Mars is to Earth.
Thanks to the Curiosity rover, we’ve been able to see Mars from a never-before-seen perspective.
We have been able to identify numerous geological features on Mars, which have helped scientists determine that billions of years ago, the red planet was in fact much more like Earth, with oceans, rivers, and lakes covering its surface.
So, apart from being a mobile scientific laboratory, Curiosity has proven it’s a great photographer too.
Using data provided by Curiosity, photographer Andrew Bodrov has published the first and only 4-billion-pixel panorama image of Mars.
The images for panorama obtained by the two rover’s Mast Cameras:
- Narrow-Angle Camera (NAC), which has a 100 mm focal length
- Medium Angle Camera (MAC), which has a 34 mm focal length
The mosaic, which stretches 90000×45000 pixels, includes 295 images from NAC taken on Sols 136-149 and 112 images from MAC taken on Sol 137.
Here’s the image:
But there are of course other fascinating images that will surely take your breath away.
Here’s a different view:
A selfie on Mars:
Mars+NASA’s Curiosity Mars Rover+Night=Breathtaking 360 image.
Mars Panorama – Curiosity rover: Martian night. Out of this World by Andrew Bodrov. Artists impression.
Credit: 360pano.eu – 360º VR Photography & Video: | 0.862424 | 3.001157 |
On April 18, 2014 the SpaceX Dragon CRS-3 ISS resupply ship was launched into space. 23 minutes after the spacecraft left the ground, it would provide an amazing show to European observers. Just across the Atlantic, in the Netherlands, I was waiting with the telescope to see what I could capture from the launch. I never had such a favorable opportunity before to photograph an orbiting object so shortly after launch. The timing has to be exactly right and in most cases a satellite is still in a very low Earth orbit when it reaches Europe for the first time after launching from the Cape. This narrows the time window – usually at twilight – when the sun is still capable of illuminating the object. I once succeeded in observing the Space Shuttle with just-released external tank very low above the horizon from the Netherlands, a really amazing sight. You could even make out the appearance that the tank (which was orbiting some kilometers lower) entered Earth’s shadow a few seconds before the Shuttle did. There are no images from this observation as this was a very difficult sighting, just a few degrees above the horizon, way too low to obtain any useful images.
However, the Falcon 9 CRS-3 launch in April also was an amazing sight and was, thanks to the favorable elevation, well-photographed in high resolution. I was lucky that the Dragon was sent quickly after launch into a relatively high orbit, making illumination time sufficiently long to have a good chance to observe Dragon. As expected, the upper stage of the Falcon 9 rocket and the Dragon were close together when passing in the sky and there were two other items from the launch (solar panel covers) bracketing the pair. By switching the telescope rapidly between the two brightest objects, I was able to obtain detailed images of the capsule and the upper stage with a clearly visible Merlin rocket engine nozzle. Was this the first image of a rocket engine in space obtained with backyard equipment?
This was not the first time I acquired images of a SpaceX rocket engine from the ground; On May 22, 2012, the Dragon C2+ spacecraft (also known as COTS Demo Flight 2) launched from the Cape Canaveral Air Force Station Space Launch Complex 40. This Dragon was the first commercial cargo craft that docked to the ISS. The spacecraft lifted up on the two stage Falcon 9 rocket. Several days after the launch, my visibility window of the ISS orbit started, along with the orbit of the Dragon & rocket debris. I could not observe the flight of the Dragon to the ISS due to the later (day lit) window, but there were several favorable passes for the rocket and rocket debris. I visually observed one of the Falcon 9 fairings (cataloged as Debris C) on May 29 while it was clearly tumbling at a low rate, but this and the other fairing (Debris D) decayed on June 7 and June 9 respectively, well before any imaging could be obtained.
The most interesting remaining orbiting item of the Dragon C2+ launch, however, was the Falcon 9 second stage (or orbital/upper stage) with its big Merlin engine (type 1C). Several favorable passes over the observing location resulted in very useful observations and one of them in nearly excellent conditions. The Merlin engine can be seen clearly in the photograph. In contrast with what is usually the case with Soyuz rocket upper stages from launches of the Progress cargo ship (or Soyuz), the Falcon 9 upper stage looked very stable. No visible sign of tumbling motion was observed during all passes. The images below were obtained with a 10 inch aperture reflecting telescope and the object was tracked fully manually. We see two of the best images of the sequence in comparison with a model of the Falcon 9 upper stage below. The Merlin 1C engine can been seen splendidly. | 0.844154 | 3.019445 |
Researchers dealing with information from the Kepler objective have actually found an extra 18 Earth-sized worlds. The group utilized a more recent, more strict approach of combing through the information to discover these worlds. Amongst the 18 is the tiniest exoplanet ever discovered.
The Kepler objective was really effective and we now understand of more than 4,000 exoplanets in remote planetary systems. However there’s a comprehended tasting mistake in the Kepler information: it was much easier for the spacecraft to discover big worlds instead of little ones. The majority of the Kepler exoplanets are massive worlds, close in size to the gas giants Jupiter and Saturn.
It’s simple to comprehend why this is so. Certainly, bigger things are much easier to discover than smaller sized things. However a group of researchers in Germany have actually established a method to search Kepler’s information and they have actually discovered 18 little worlds that have to do with the size of Earth. This is substantial.
In case you’re not acquainted with planet-hunting strategies, and the Kepler spacecraft particularly, it utilized what’s called the “ transit approach” of discovering worlds. Each time a world passes in front of its star, that’s called a transit. Kepler was finely-tuned to spot the drop in starlight brought on by an exoplanet’s transit.
The drop in starlight is little, and really tough to spot. However Kepler was constructed for the function. The Kepler spacecraft, in mix with follow-up observations with other telescopes, might likewise figure out the size of the world, and even get a sign of the world’s density and other attributes.
Researchers highly presumed that the Kepler information was not agent of the population of exoplanets due to the fact that of the tasting predisposition. All of it boils down to the specifics of how Kepler utilizes the transit approach to discover exoplanets.
Because Kepler taken a look at over 200,000 stars to spot dips in starlight brought on by transiting exoplanets, much of the analysis of the Kepler information needed to be done by computer systems. (There aren’t sufficient impoverished astronomy college student on the planet to do the work.) So researchers depended on algorithms to comb the Kepler information for transits.
” Basic search algorithms try to recognize unexpected drops in brightness,” describes Dr. René Heller from MPS, very first author of the present publications. “In truth, nevertheless, an excellent disk appears somewhat darker at the edge than in the center. When a world relocates front of a star, it for that reason at first obstructs less starlight than at the mid-time of the transit. The optimum dimming of the star takes place in the center of the transit prior to the star ends up being slowly brighter once again,” he describes.
Here’s where exoplanet detection gets challenging. Not just does a bigger world trigger a higher drop in brightness than a smaller sized world, however a star’s brightness naturally changes too, making smaller sized worlds even harder to spot.
The technique for Heller and the group of astronomers was to establish a various or maybe “smarter” algorithm that takes into consideration the light curve of a star. To an observer like Kepler, the middle of the star is the brightest, and big worlds trigger an extremely unique, fast dimming of the light. However what about on the edge, or limb, of a star. Was it possible that transits of smaller sized worlds were going undiscovered because dimmer light?
By enhancing the level of sensitivity of the search algorithm, the group had the ability to address that concern with a convincing “yes.”
” Our brand-new algorithm assists to draw a more reasonable image of the exoplanet population in area,” sums up Michael Hippke of Sonneberg Observatory. “This approach makes up a substantial advance, particularly in the look for Earth-like worlds.”
The outcome? “In the majority of the planetary systems that we studied, the brand-new worlds are the tiniest,” stated co-author Kai Rodenbeck of the University of Göttingen and Max Planck Institute for Planetary System Research Study. Not just did they discover an extra 18 Earth-sized worlds, however they discovered the tiniest exoplanet yet, just 69% the size of the Earth. And the biggest of the 18 is hardly two times the size of Earth. This remains in sharp contrast to the majority of the exoplanets discovered by Kepler, which remain in the size series of Jupiter and Saturn.
Not just are these brand-new worlds little, however they’re closer to their stars than their previously-discovered brother or sisters. So not just is the brand-new algorithm offering us a more precise image of exoplanets populations by size, it’s likewise offering us a clearer image of their orbits.
Due to their distance to their stars, the majority of these worlds are scorchers with surface area temperature levels in excess of 100 Celsius, and some going beyond 1,000 Celsius. However there’s one exception: among them orbits a red dwarf star and seems in the habitable zone, where liquid water might continue.
There might be more smaller sized exoplanets concealed in the Kepler information. Up until now, Heller and his group have actually just utilized their brand-new strategy on a few of the stars taken a look at by Kepler. They concentrated on simply over 500 Kepler stars that were currently understood to host exoplanets. What will they discover if they analyze the other 200,000 stars?
It’s a clinical reality that each approach of determining something has an intrinsic tasting predisposition. It is among the restraints in any clinical research study. The group behind this brand-new exoplanet algorithm totally acknowledges that their approach might likewise include a tasting predisposition.
Smaller sized worlds at more remote orbits can have long orbital durations. In our Planetary System, Pluto takes 248 years to finish one orbit around the Sun. To spot a world like that, it might use up to 248 years of observation prior to we discovered a transit.
However, they forecast that they will discover more than 100 other Earth-sized exoplanets in the remainder of the Kepler information. That’s many, however may be a modest price quote, thinking about that the Kepler information covers over 200,000 stars.
The strength of the brand-new search algorithm will extend beyond the Kepler information. According to Prof. Dr. Laurent Gizon, Handling Director at the MPS, future planet-hunting objectives can likewise utilize it to improve their outcomes. “This brand-new approach is likewise especially beneficial to get ready for the upcoming PLATO(PLAnetary Transits and Oscillations of stars) objective to be released in 2026 by the European Area Firm”, stated Prof. Gizon.
The group released their lead to the journal Astronomy and Astrophysics Their paper is entitled ” Transit least-squares study. II. Discovery and recognition of 17 brand-new sub- to super-Earth-sized worlds in multi-planet systems from K2.” | 0.802047 | 3.780604 |
NASA's Insight Lander: What can Mars teach us about our planet?
The InSight mission will be the first mission ever to explore the deep insides of the Red Planet.
After a six-month space cruise, NASA's latest Mars mission is set to arrive at the Red Planet on Monday with a single goal: explore its deep insides.
InSight Lander - the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport - is the US space agency's first craft dedicated to peer beneath Mars' surface and study its interior.
Its landing, at around 20:00 GMT, will make it the first US robot to visit the planet since Curiosity in 2012.
But this is far from an easy feat - of the 44 NASA missions sent to Mars, only 18 have been successful.
Here's everything you need to know about the spacecraft, its landing and the information it has set out to gather.
What is InSight Lander?
NASA describes InSight Lander as the first outer space robotic explorer designed to give the billions-years-old Mars a "thorough checkup" by studying its crust, mantle and core.
But there are big challenges before this is achieved - including the "seven minutes of terror".
In order to land, the spacecraft will enter the Martian atmosphere at supersonic speed (almost 17 times the speed of sound), then hit the brakes to achieve a soft landing on the planet's red plains, in a region called Elysium Planitia that has been chosen for its geographical flatness.
"As in all missions to Mars, the challenge is to get the module to operate its instruments and to land into the atmosphere correctly," says Rafael Navarro-Gonzalez, a member of the Curiosity mission and a researcher at the Institute of Nuclear Sciences in National Autonomous University of Mexico (UNAM).
NASA engineers consider the agonising seven-minute period between entry, descent and landing the riskiest sequence in the entire mission.
It can take up to about 20 minutes for the spacecraft's signals to reach Earth, leaving mission planners waiting with bated breath to find out about if everything went according to plan. Unable to intervene, they rely on a perfect symphony of pre-programmed tasks, robotic devices and controlled explosions.
Once InSight successfully lands - if it survives the perilous entry - it must be properly aligned with the sun to keep producing power and charging its batteries.
"When using solar energy, it is important that the rover properly poses on the surface and that there are not big sandstorms that clog the solar panels," Navarro-Gonzalez told Al Jazeera.
NASA will do a live broadcast of the landing attempt on this link. The broadcast will begin at 19:00 GMT on Monday.
What kind of information will InSight gather?
NASA says the mission will measure what it describes as Mars' "vital signs": its pulse (seismology), temperature (heat flow) and reflexes (precision tracking).
The lander's main instruments include a seismometer to track quakes and a thermometer to measure the planet's interior temperature by "drilling" itself five meters deep into the Martian surface.
These instruments - provided respectively by the French and German space agencies - have a novel method of deployment: after landing, the craft will use a robotic arm to place them far from it to avoid any pollution of data.
Another instrument, a radio transmitter, will use the Doppler effect - an increase or decrease in the frequency of sound or light - to measure the "wobble" of the planet's rotation axis.
Jose Antonio Rodriguez Manfredi, a scientist at the InSight mission, told Al Jazeera that these instruments will allow NASA to record the planet's "seismic activity, the movements of the crust caused by meteoric impacts, the heat flow and physical properties of the terrain, and the variations that the planet may experience in its rotation period, daily, and in its translation around the sun".
He added that other instruments will register wind and temperature patterns, as well as variations in the atmospheric pressure and magnetic field.
What's the goal of gathering this information?
According to NASA, there was a time when the Earth and Mars were warm, wet and shrouded in thick atmospheres.
However, three or four billion years ago, something changed causing these "sibling" planets to take different paths.
By studying Mars at its core, InSight aims to go back in time and shed light into what factors resulted in producing an Earth full of life and a desolated Mars.
"The information collected will help us to understand the evolution of rocky planets inside and outside our solar system," Navarro-Gonzalez says, adding that the gathered date will help open a window into understanding life.
"Rocky planets like ours are essential for the emergence and evolution of life as we know it.
"Our goal is to find a second genesis of life, and we believe that Mars is the [place] where we can find it. In this way, we could revolutionise the biology from terrestrial to universal," Navarro-Gonzalez adds.
How is this relevant to people on Earth?
Manfredi says this type of missions do not only contribute in the greater knowledge of the universe and life but also result in improving people's everyday lives here on Earth.
"New materials and new technologies are constantly coming out of this type of projects which are later used in our daily life: mobile phones, the materials with which the bodies of cars or helmets are now built, medical advances that are tested in the Station International Space, among others," he says.
Manfredi adds that these missions also shape humanity's relationship with the universe, predicting that "it will not be long until we can see a human crew roaming" the Red Planet's surface.
"Mars still has many surprises to unveil," Manfredi says.
"In the future, missions - such as Nasa's next M2020 mission - will aim to bring samples back to Earth that will deepen our knowledge of the interior of the planet.
In 2020, three exploration vehicles from the US, Europe and China are already scheduled to attempt to land on Mars.
SpaceX, a private space corporation, has also hinted at a potential cargo mission to Mars in 2022 with the intention of paving a path for future manned missions.
"I believe that the human presence in space will continue to grow in the 21st century, and the next century," says Miguel Alcubierre, a researcher at the Institute of Nuclear Sciences in the UNAM.
"And little by little, we will expand through the solar system, perhaps reaching the next 22nd century to the moons of Jupiter and Saturn," he adds.
"Our expansion by the solar system is inevitable in the long term and a natural consequence of our technological development and our curiosity.
"If in 500 years we have not colonised the entire solar system, I think it would be very depressing and would indicate that something catastrophic happened that stopped us."
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If you have an Android OS smartphone, go to this link to read the news more easily You can download and install Ens.az from the store. | 0.825479 | 3.313444 |
There are a few questions regarding the Alcubierre drive here, so I'll pose this one and see what I get.
Currently, our space exploration vehicles, both manned and unmanned, are at the mercy of Kepler and Newton. We have some control over what direction we're pointed and how fast we're going, but our movement through space is governed by slingshotting around the Earth, Sun and other planets and moons, which allow us to gain, lose or maintain our velocity much more efficiently than any rocket could. There's no energy source nor thrust motor we can conceive of that's powerful or long-lived enough to allow us to ignore orbital motion and simply push, against the Sun and any other nearby gravity wells, to take a relatively straight-line path anywhere in our neighborhood.
Editing based on Deer Hunter's comment...
Let's now conceive of a drive system powerful enough that we no longer need to use gravity slingshotting as our primary means of propulsion outside LEO. The Alcubierre Drive is currently the most plausible future tech, but we could imagine virtually any drive system that would allow us to not only "win", handily, against the straight-line pull of anything in the Solar system, but be efficient enough that such a tug-o-war is a drop in the bucket for the fuel capacity of the ship equipped with such a drive. Such a drive system, even if it were subluminal, would be the gateway to the solar system (even half-light speed, impractical for interstellar travel, would make landing on Mars and coming back a day trip).
Here's the question; given a drive system, Alcubierre-based or otherwise, powerful enough that we no longer depend on gravity-based navigation maneuvers to get around, what role would gravity still play in our navigation and maneuvering? Obviously, where gravity helps us out, such as falling toward the Sun to cross the system, we could let it, and there's really no "standing still" (though even that could be possible with such a drive system, depending on your definition of "still"), but given that we'd have the ability to travel much faster than gravity could pull us, I imagine that gravity would be more hindrance than help; we'd simply adjust course to account for the effect of gravity wells as we pass by them, much as we currently do in airplanes to account for wind.
So, would gravity really matter anymore in the post-reactionary thrust engine era of space travel? Or would it, much like the wind to an airplane, simply be something to correct for? | 0.844576 | 3.594291 |
Cosmology: The Big Bang
Historically the assertion that our Universe began in a Big Bang was based on three observations: the “Hubble” expansion of the Universe, the observation of the 2.7 Kelvin cosmic microwave background radiation, and the synthesis of the light elements H, He, and Li that were produced in Big Bang nucleosynthesis in the first few minutes of our Universe’s life.
Recent high precision measurements of the CMB radiation and observations of high redshift Type 1A supernovae have greatly improved our understanding of the details of the Big Bang. However, the Li abundance continues to be a problem in understanding the Big Bang abundances.
This figure (right) shows the abundances of the nuclides produced in the Big Bang as a function of the Baryon to Photon ratio, i.e., essentially the density of the Universe during Big Bang Nucleosynthesis. The white boxes show the preferred abundances for 4He, D/H, and 7Li/H ratios, while the yellow boxes indicate statistically acceptable regions. The region in purple is thought to represent the correct value of the BP ratio. Although agreement appears somewhat marginal, it should be noted that the abundances are in fair agreement over ten orders of magnitude.
Boyd’s BBN Collaboration
Boyd and his collaborators have recently analyzed the myriad of nuclear reactions that contribute to BBN, and have identified those that might contribute the most uncertainty to the Li abundance.
See R.N. Boyd, C. Brune, G.M. Fuller, & C. Smith, Phys. Rev. D 82, 105005 (2010). | 0.830996 | 3.738113 |
Just less than 13,000 years ago, the climate cooled for a short while in many parts of the world, especially in the northern hemisphere. We know this because of what has been found in ice cores drilled in Greenland, as well as from oceans around the world.
Grains of pollen from various plants can also tell us about this cooler period, which people who study climate prehistory call the Younger Dryas and which interrupted a warming trend after the last Ice Age. The term gets its name from a wildflower, Dryas octopetala. It can tolerate cold conditions and was common in parts of Europe 12,800 years ago. At about this time a number of animals became extinct. These included mammoths in Europe, large bison in North America, and giant sloths in South America.
The cause of this cooling event has been debated a great deal. One possibility, for instance, is that it relates to changes in oceanic circulation systems. In 2007 Richard Firestone and other American scientists presented a new hypothesis: that the cause was a cosmic impact like an asteroid or comet. The impact could have injected a lot of dust into the air, which might have reduced the amount of sunlight getting through the earth’s atmosphere. This might have affected plant growth and animals in the food chain.
Research we have just had published sheds new light on this Younger Dryas Impact Hypothesis. We focus on what platinum can tell us about it.
How platinum fits into the picture
Platinum is known to be concentrated in meteorites, so when a lot of it is found in one place at one time, it could be a sign of a cosmic impact. Platinum spikes have been discovered in an ice core in Greenland as well as in areas as far apart as Europe, Western Asia, North America and even Patagonia in South America. These spikes all date to the same period of time.
Until now, there has been no such evidence from Africa. But working with two colleagues, Professor Louis Scott (University of the Free State) and Philip Pieterse (University of Johannesburg), I believe there is evidence from South Africa’s Limpopo province that partly supports the controversial Younger Dryas Impact Hypothesis.
The new information has been obtained from Wonderkrater, an archaeological site with peat deposits at a spring situated outside a small town to the north of Pretoria. In a sample of peat we have identified a platinum spike that could at least potentially be related to dust associated with a meteorite impact somewhere on earth 12,800 years ago.
The platinum spike at Wonderkrater is in marked contrast to almost constantly low (near-zero) concentrations of this element in adjacent levels. Subsequent to that platinum spike, pollen grains indicate a drop in temperature. These discoveries are entirely consistent with the Younger Dryas Impact Hypothesis.
Wonderkrater is the first site in Africa where a Younger Dryas platinum spike has been detected, supplementing evidence from southern Chile, in addition to platinum spikes at 28 sites in the northern hemisphere.
We are now asking a question which needs to be taken seriously: surely platinum-rich dust associated with the impact of a very large meteorite may have contributed to some extent to major climatic change and extinctions?
A meteorite crater in Greenland
Very recently a large meteorite crater with a diameter of 31km was discovered in northern Greenland, beneath the ice of the Hiawatha glacier. It is not certain that it dates to the time of the Younger Dryas, but the crater rim is fresh, and ice older than 12,800 years is missing.
It seems possible (but is not yet certain) that this particular crater relates to the hypothesised meteorite that struck the earth at the time of the Younger Dryas, with global consequences.
The effects of a meteorite impact may potentially have contributed to extinctions in many regions of the world. There is no doubt that platinum spikes in North America coincide closely with the extinction of animals on a big scale about 12,800 years ago.
Extinctions in Africa
In a South African context, my team is suggesting that platinum-rich cosmic dust and its associated environmental effects may have contributed to the extinction of large animals that ate grass. These have been documented at places such as Boomplaas near the Cango Caves in South Africa’s southern Cape, where important excavations have been undertaken.
At least three species went extinct in the African subcontinent. These included a giant buffalo (Syncerus antiquus), a large zebra (Equus capensis) and a large wildebeest (Megalotragus priscus). Each weighed about 500kg more than its modern counterpart.
There may have been more than one cause of these extinctions. Hunting by humans could have been a factor. And the large buffalo, zebra and wildebeest had already been affected by habitat changes at the end of the last Ice Age, which was at its coldest about 18,000 years ago.
What about human populations? A cosmic impact could have indirectly affected people as a result of local changes in environment and the availability of food resources, associated with sudden climate change. Stone tools relate to the cultural identity of people who lived in the past. Around 12,800 years ago in at least some parts of South Africa there is evidence of an apparently abrupt termination of the “Robberg” technology represented by stone tools found for example at Boomplaas Cave.
Coincidentally, North American archaeological sites indicate the sudden end of a stone tool technology called Clovis.
But it is too early to say whether these cultural changes relate to a common causal factor.
The Younger Dryas Impact Hypothesis, and the evidence to support it, is a reminder of how much can change when a rocky object hits the earth. Many asteroids are situated between Mars and Jupiter, and on occasion some come very close to our planet. The probability of a large one striking earth may seem to be low. But it’s not impossible.
Take Apophis 99942. It is classified as a potentially hazardous asteroid. It is 340 metres wide and will come exceptionally close to the earth (in relation to an Astronomical Unit, the distance between us and the sun) on Friday April 13 2029. The probability of its hitting us in ten years’ time is only one in 100,000. But the probability of an impact may be even higher at some time in the remote future.
What’s more, comets associated with the Taurid Complex approach the earth relatively closely at intervals of centuries. So a large asteroid or comet could fall to earth in the foreseeable future.
The Younger Dryas Impact Hypothesis is highly controversial. But the evidence suggests it is not improbable that a large meteorite struck the earth as recently as 12,800 years ago, with widespread consequences. | 0.855144 | 3.65752 |
In 2013, NASA’s Curiosity Rover detected a spike of methane gas in the Martian atmosphere. It was particularly exciting news at the time because methane is often a chemical byproduct of living organisms on Earth. On the other hand, methane can also be produced by geological processes, and so the discovery doesn’t automatically mean that life exists on the red planet.
A significant discovery like this one should have been confirmed with a second source shortly after being detected, but for whatever reason, that wasn’t the case. Fortunately, researchers are now picking up the slack nearly six years later. A new paper has been published this week in the journal Nature Geoscience after a team of researchers used data from the ESA’s Mars Express spacecraft to validate the Curiosity Rover’s 2013 findings.
Image Credit: Spacecraft image credit: ESA/ATG medialab; Mars: ESA/DLR/FU Berlin
“In general, we did not detect any methane, aside from one definite detection of about 15 parts per billion by volume of methane in the atmosphere, which turned out to be a day after Curiosity reported a spike of about six parts per billion,” elucidated study lead author Marco Giuranna.
“Although parts per billion in general means a relatively small amount, it is quite remarkable for Mars—our measurement corresponds to an average of about 46 tons of methane that was present in the area of 49,000 square kilometers observed from our orbit.”
As it turns out, methane gas doesn’t tend to last very long in the Martian atmosphere, and with that in mind, the methane that Curiosity detected in 2013 must have been produced somewhat recently. While this much is clear to planetary scientists, one blistering question remains: where did Mars’ methane actually come from?
The newly-published paper doesn’t reveal a definitive source of the methane gas on Mars, which isn’t particularly surprising given the lack of answers concerning the matter. On the other hand, it’s the first independent confirmation that Curiosity’s methane detection was anything but a fluke. Given the circumstances, researchers can’t do much apart from speculate about its source.
“Our new Mars Express data, taken one day after Curiosity’s recording, change the interpretation of where the methane originated from, especially when considering global atmospheric circulation patterns together with the local geology,” Giuranna added. “Based on geological evidence and the amount of methane that we measured, we think that the source is unlikely to be located within the crater.”
Upon doing some additional probing into the source of the methane, the researchers found that it may have originated East of Gale Crater. There, a bevy of geological faults exist; these may have ruptured permafrost in the area, freeing any methane gas that might’ve been trapped inside of it in the process. The novel idea is merely hypothetical, of course.
Without more data, it’s challenging to discern exactly where the methane gas on Mars came from. On the other hand, space agencies are ramping up Martian exploration as we speak, and it’s hoped that some of these missions could provide the insight we need for solving such mysteries. With that in mind, it should be interesting to see what we’ll learn as planetary scientists continue their search. | 0.865113 | 3.938319 |
Planetary scientists discovered unexpected and enormous ice avalanches on Saturn’s moon Iapetus, half of which is light-colored while the other is dark. Its mountains are 12 miles in height, which is twice the height of Mount Everest.
Kelsi Singer, graduate student in earth and planetary sciences at Washington University in St. Louis, and the lead author of a new study published in the journal Nature Geoscience states that this isn’t something that they were expecting to find on Iapetus.
The icy landslides are something similar to long-runout ones on Earth that are known as sturzstroms. They can travel distances 20 to 30 times the height they fall from. Typical landslides only travel about twice the height they fall from. This implies that the Iapetus landslides were probably caused by objects impacting the moon’s surface.
Planetary scientists aren’t yet sure on exactly what mechanism allows them to travel so far, but possible candidates include riding on a cushion of trapped air, sliding on groundwater or mud, sliding on ice, or slipping caused by strong acoustic vibrations. Singer thinks that on Iapetus the landslides are caused by frictional heating of ice.
The researchers analyzed images taken by NASA’s Cassini spacecraft as it orbited Saturn in 2004 and 2007. They measured the ratio of the landslide’s vertical to horizontal motion, and estimated the friction involved. The ratios indicate that the friction was caused by flash heating of the ice until it was slippery enough to slide on, without completely melting.
It could involve a phenomenon known as pre-melting, where only a thin layer of ice crystals melt. Since Iapetus is so cold, ice acts like rock on Earth. | 0.871005 | 3.689024 |
Check out this artist's impression of an super-violent supernova. The Very Large Telescope managed to obtain the first 3-D view of material after a star's explosion, traveling 100 million kilometers per hour. And check out a video below.
Astronomers using ESO's Very Large Telescope have for the first time obtained a three-dimensional view of the distribution of the innermost material expelled by a recently exploded star. The original blast was not only powerful, according to the new results. It was also more concentrated in one particular direction. This is a strong indication that the supernova must have been very turbulent, supporting the most recent computer models...
[Supernova 1987A] has been a bonanza for astrophysicists. It provided several notable observational ‘firsts', like the detection of neutrinos from the collapsing inner stellar core triggering the explosion, the localisation on archival photographic plates of the star before it exploded, the signs of an asymmetric explosion, the direct observation of the radioactive elements produced during the blast, observation of the formation of dust in the supernova, as well as the detection of circumstellar and interstellar material (eso0708).
New observations making use of a unique instrument, SINFONI , on ESO's Very Large Telescope (VLT) have provided even deeper knowledge of this amazing event, as astronomers have now been able to obtain the first-ever 3D reconstruction of the central parts of the exploding material.
This view shows that the explosion was stronger and faster in some directions than others, leading to an irregular shape with some parts stretching out further into space. | 0.858007 | 3.331217 |
T Sumner, P Wass, D Hollington, J Baird
LISA Pathfinder launched from Kourou in French Guiana on at 0404UTC on 3 December 2015. The mission is aimed at demonstrating the technology required for a gravitational wave observatory in space, eLISA. The High Energy Physics group at Imperial College have been involved in the project since the 1990s, calculating the effect of the high-energy cosmic ray environment on instrument performance, building components for the spacecraft’s instrument and preparing experiments and data analysis tools to carry out in orbit.
LISA Pathfinder details
In order to measure the tiny distortions in space produced by gravitational waves the forces acting on the test masses of eLISA must be reduced to a level below 6fN/√Hz at frequencies between 0.1mHz and 10mHz. LISA Pathfinder will make measurements to show that this challenging goal is feasible, compressing one arm of the LISA interferometer to 38cm within a single spacecraft.
The relative motion of two test masses will be measured with pico-meter accuracy using a laser interferometer. Deriving the relative acceleration of the masses provides a measure of the forces exerted on them that in eLisa could disturb gravitational wave observations. During the LISA Pathfinder mission a series of experiments will be conducted to measure and characterise the contribution to the limiting performance of the instrument coming from a range of physical effects.
In order to maintain the test masses in complete isolation from their environment, the spacecraft must follow their pure geodesic motion or free-fall through space. To do so a system of capacitive sensing is used to determine the test mass positions; on-board software uses the position information to command micro-Newton thrusters pushing the spacecraft against solar radiation pressure and keeping the test masses centred in their housings.
Test mass charging
If the test mass becomes charged, electric fields within the capacitive sensor can create an unwanted force on the test mass. Such a charge can build up because the spacecraft is constantly bombarded by high-energy cosmic rays – mostly protons and helium nuclei – which penetrate the shielding of the spacecraft. Occasionally eruptions of particles from the Sun will cause the test masses to become charged even more quickly.
Imperial College scientists have used physics simulation tools developed for high energy physics experiments to model the interaction of the cosmic rays with the spacecraft and instrument structure. The results of these simulations have enabled scientists to predict the disturbing effects of environmental test-mass charging and how often it will be necessary to discharge the test masses to maintain the best performance of the instrument. The particle flux responsible for charging will be monitored independently on board by a radiation monitor, providing diagnostic information to compare measured charge rates with predictions.
The test masses must be kept electrically neutral but without introducing additional force disturbances. Imperial College HEP group has designed and built a system of UV lamps that illuminate the gold surfaces of the test mass and surrounding sensor, liberating electrons by photoemission. By carefully controlling the illumination, the test mass can be positively or negatively charged until the net charge is zero.
The UV Lamp Unit (ULU) contains six UV mercury discharge lamps, control electronics and the communications interface with the rest of the spacecraft. The electronics that control the lamps were designed in-house by Imperial engineers and the structure of the unit was built in the physics instrumentation workshop. The light from the lamps is filtered and focused into specially designed fibre optics that deliver it from the outer structure of the spacecraft to the sensitive inner core of the instrument.
Rigorous testing had to be carried out to show that all components can withstand the harsh radiation environment of space as well as the mechanical vibrations and shocks that occur during launch. Once in space, repairs are impossible so each function of the unit has a spare or redundant counterpart that can be enabled in case of a failure. In orbit, all units on the spacecraft will be switched on and checked out to ensure no damage has occurred during launch and that the system is behaving as it was when tested on ground. When all systems have been given the OK the test masses will be released into free fall and the mission proper can begin.
LISA Pathfinder is an ultra-high precision physics laboratory in space. Mission operations will consist of a series of experiments aimed at measuring and characterising all the forces acting on the test masses.
A typical experiment involves injecting a known disturbance into the system, using coils to produce a magnetic field at the test mass for example, and measuring the force on the test mass that arises as a result. Later, during a ‘quiet’ measurement of force noise, the calculated coupling factor can be used to convert the measured background magnetic field into a contribution to the total force on the test mass. By repeating this process for all sources of force noise in the instrument it will be possible not only to demonstrate the feasibility of a gravitational wave observatory but to understand the improvements that must be made to achieve the performance goals of eLISA.
Experiments will be executed autonomously by the spacecraft from a plan defined up to 7 days in advance. Data from the satellite will analysed on a daily basis and the results used to update the experiment schedule. Given the short duration of the mission, scientists will have to work to an intensive schedule in order to obtain the maximum possible information from the on-board measurements. | 0.890249 | 3.732871 |
The sun spits up solar flares all the time. No big deal. But you know what it doesn’t normally do? Spit up superflares: events more than a thousand times powerful than regular solar flares. As far as we know, the sun has never superflared. According to new research, however, never say never.
In findings published Wednesday, scientists from England’s University of Warwick report they observed a nearby binary star, KIC 9655129, in the Milky Way, producing regular superflares. The star’s flares are quite similar to the sun’s own solar flares, leading the researchers to believe the sun has a potential to superflare.
Solar flares can cause major problems for the modern world. Practically everything humans do these days is tied to electricity. Last month, we reported on new research that suggests a pair of intense solar flares that hit the Earth during the Middle Ages would cripple the world’s electrical infrastructure if they were to strike today: They’d knock out a lot of communications equipment, and create large scale power blackouts. And those were just regular solar flares.
A typical superflare releases the energy equivalent of a 100 million megaton bombs. If the sun emitted a superflare, however, it would be closer to a billion megaton bombs.
In other words, we’d be fucked.
Lead author Chloe Pugh explains that superflares are actually a very common event in the rest of the Universe. “Most of the stellar flares that we see emitted from other stars are superflares,” she says. “Because the stars are so far away, we can only detect the brightest flares.”
The researchers sought to uncover the kind of physical process responsible for causing both stellar superflares and solar flares. They studied the pulsations associated with each type of flare using the Kepler space telescope, and found that the stellar flares emitted by KIC 9655129 exhibited wave patterns very similar to the sun’s own flares.
So the sun has the potential to emit a civilization-destroying superflare. Rest easy, people — Pugh says that it’s ”very unlikely in our lifetimes” the sun emits a superflare. That doesn’t mean we shouldn’t safeguard ourselves from the destruction a normal solar flare could bring, but at least we know our sun isn’t more prone to violence than the rest of the stars of the universe. | 0.821105 | 3.485707 |
Owls may be scarce near your favourite viewing spot, but the Northern Hemisphere spring sky contains one celestial owl that you can track down in small telescopes – Messier 97 (NGC 3587). Commonly called the Owl Nebula, M97 is a planetary nebula discovered by Pierre Méchain in 1781 that is currently ideally placed for observation almost overhead at nightfall in the constellation of Ursa Major, the Great Bear.
At the beginning of August, keen observers in the heart of the UK can celebrate the return of truly dark skies around 1am BST. But the naked-eye stars are out by 11pm, and if you cast your gaze two-thirds of the way from southeast horizon to overhead at this time you can see the so-called Summer Triangle in all its glory. Here’s our guide to some of the celestial highlights therein.
While truly massive stars go out in a blaze of glory, intermediate-mass stars — those between roughly one and eight times the mass of the Sun — are somewhat quieter. Such stars eventually form cosmic objects known as planetary nebulae, so named because of their vague resemblance to planets when seen through early, low-resolution telescopes.
This planetary nebula is known as Kohoutek 4-55 (or K 4-55). It is one of a series of planetary nebulae that were named after their discoverer, Czech astronomer Luboš Kohoutek. Such a nebula is formed from material in the outer layers of a red giant star that are expelled into interstellar space when the star is in the late stages of its life.
Planetary nebulae such as Hen 2-437 form when an ageing low-mass star — such as the Sun — reaches the final stages of life. The star swells to become a red giant, before casting off its gaseous outer layers into space. Hen 2-437 is a bipolar nebula — the material ejected by the dying star has streamed out into space to create the two icy blue lobes pictured here.
When stars that are around the mass of the Sun reach their final stages of life, they shed their outer layers into space, which appear as glowing clouds of gas called planetary nebulae. In the case of Menzel 2, otherwise known as PK 329-02.2, the nebula forms a winding blue cloud that perfectly aligns with two stars at its centre.
This new NASA/ESA Hubble Space Telescope image of the Twin Jet Nebula highlights the shimmering colours, shells and knots of expanding gas in striking detail. Two iridescent lobes of material stretch outwards from a central star system. Within these lobes two huge jets of gas are streaming from the star system at speeds in excess of one million kilometres per hour.
This extraordinary bubble, glowing like the ghost of a star in the haunting darkness of space, may appear supernatural and mysterious, but it is a familiar astronomical object: a planetary nebula, the remnants of a dying star. This is the best view of the little-known object ESO 378-1 yet obtained and was captured by ESO’s Very Large Telescope in northern Chile.
A dying star’s final moments are captured in this image of planetary nebula NGC 6565 in Sagittarius from the NASA/ESA Hubble Space Telescope. The death throes of this star may only last mere moments on a cosmological timescale, but this star’s demise is still quite lengthy by our standards, lasting tens of thousands of years. | 0.900053 | 3.887206 |
Gibbous ♌ Leo
Moon phase on 3 January 2094 Sunday is Waning Gibbous, 16 days old Moon is in Leo.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 1 day on 1 January 2094 at 16:51.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing first ∠3° of ♌ Leo tropical zodiac sector.
Lunar disc appears visually 9.9% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1951".
Next Full Moon is the Wolf Moon of January 2094 after 28 days on 31 January 2094 at 12:36.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 16 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 1162 of Meeus index or 2115 from Brown series.
Length of current 1162 lunation is 29 days, 11 hours and 18 minutes. This is the year's shortest synodic month of 2094. It is 40 minutes longer than next lunation 1163 length.
Length of current synodic month is 1 hour and 26 minutes shorter than the mean length of synodic month, but it is still 4 hours and 43 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠335.6°. At the beginning of next synodic month true anomaly will be ∠352.5°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
14 days after point of perigee on 19 December 2093 at 18:42 in ♑ Capricorn. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next day, until it get to the point of next apogee on 4 January 2094 at 09:27 in ♌ Leo.
Moon is 405 390 km (251 898 mi) away from Earth on this date. Moon moves farther next day until apogee, when Earth-Moon distance will reach 406 096 km (252 336 mi).
1 day after its ascending node on 2 January 2094 at 02:47 in ♋ Cancer, the Moon is following the northern part of its orbit for the next 12 days, until it will cross the ecliptic from North to South in descending node on 16 January 2094 at 02:40 in ♑ Capricorn.
1 day after beginning of current draconic month in ♋ Cancer, the Moon is moving from the beginning to the first part of it.
1 day after previous North standstill on 1 January 2094 at 17:59 in ♋ Cancer, when Moon has reached northern declination of ∠22.474°. Next 12 days the lunar orbit moves southward to face South declination of ∠-22.474° in the next southern standstill on 15 January 2094 at 19:36 in ♑ Capricorn.
After 13 days on 16 January 2094 at 19:05 in ♑ Capricorn, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.219033 |
Understanding How Galaxies Reionized the Universe
Sanchayeeta Borthakur, Arizona State University
Identifying the population of galaxies that was responsible for the reionization of the universe is a long-standing quest in astronomy. While young stars can produce large amounts of ionizing photons, the mechanism behind the escape of Lyman continuum photons (wavelength < 912 A) from star-forming regions has eluded us. To identify such galaxies and to understand the process of the escape of Lyman continuum, we present an indirect technique known as the residual flux technique. Using this technique, we identified (and later confirmed) the first low-redshift galaxy that has an escape fraction of ionizing flux of 21%. This leaky galaxy provides us with valuable insights into the physics of starburst-driven feedback. In addition, since direct detection of ionizing flux is impossible at the epoch of reionization, the residual flux technique presents a highly valuable tool for future studies to be conducted with the upcoming large telescopes such as the JWST. | 0.809609 | 3.653089 |
This article will cover just six of the many interesting aspects of black holes that are waiting for you to discover.
For this article, I won’t be talking about the supermassive black holes which are found at the centers of galaxies. I’ll be talking about the much smaller (and counterintuitively much stronger) stellar black holes. But hey, if you’re interested in learning about the big bruisers, here’s a link.
By the way, there’s some pretty hairy technical jargon flying around in the more academic circles of black hole theory.
The links I provide here will all be to Wikipedia articles, only because they don’t bombard you with advertisements. However, their articles tend to be on the technical side. So if you want less nerdgasm and a more readable explanation of the topics I link to here, Google is your friend!
It’s my aim with this article to simplify the topic to make it more approachable for a wider, less nerdy audience. So nerds (you know who you are), please forgive me for any errors of omission or less than precise turns of phrase!
1) How a Black Hole is Created
All stars are not created equal. For a star to be capable of becoming a stellar black hole, it has to be of a certain minimum mass. There are multiple opinions in the astrophysics community concerning what that minimum is.
You don’t have to worry about our Sun becoming a black hole. Sorry, but our nearest star doesn’t qualify. Too small. The most old Sol can expect is to expand into a red giant in 5 or 6 billion years before it collapses into a white dwarf. The minimum size for a star to become a black hole is roughly 4-5 solar masses.
Basically, a star needs to be massive enough to become a supernova when its fuel runs out and the star’s core collapses under its own gravity.
Except for a Type Ia supernova, all supernovae are caused by the gravitational collapse of a very massive star’s core, which happens at the end of the star’s life and it can no longer sustain the nuclear fusion that keeps it from collapsing under its own weight. Depending on other factors, the star will then become either a neutron star or a black hole.
2) Accretion Disk – All The Best Black Holes Have The Hottest Bling
An accretion disk is often found surrounding a massive celestial body, such as a star. Black holes, being pretty darn massive, are no exception.
The disk consists of diffuse material, such as gas and dust that has fallen into the central body’s gravitational influence.
As the material in the disk loses some of its angular momentum due to friction caused by rubbing against and bouncing off of other nearby particles, it begins to heat up as it falls lower in its orbit around the black hole.
Though scientists are unsure why, the accretion disks of some bodies, such as black holes, emit jets of radiation along their polar axes.
Less dense bodies, such as young stars and protostars radiate in the infrared band of the electromagnetic spectrum. But the gravitational forces of black holes are so intense that they radiate in the X-ray band. This is one of the tell-tale signs used to find a black hole.
One of the better known components of a black hole is its Event Horizon.
A black hole’s event horizon is either a spherical or an oblate spheroid region of space which surrounds the mass of the black hole. It doesn’t have any physical properties, per se.
The radius of the event horizon is determined by how massive the original star was, minus whatever mass was thrown off by the supernova explosion.
An event horizon’s radius is a property of the amount of mass contained within the black hole. But in a sense, its not physically “there”.
You can’t “see” it as you approach it. But it certainly has a gravitational effect on any matter which has the audacity to cross that line!
The beaten-to-death cliche for black holes is that “its gravity is so strong that nothing can escape it, not even light!”
Granted, it’s a reasonable description if not completely accurate. But its definitely a cliche.
Actually, how close you get to the black hole determines whether you’ll return home to tell the tale. When matter crosses the event horizon, then there’s no turning back.
At the point you cross the event horizon, to escape the black hole’s gravitational attraction, you’d have to be traveling faster than the speed of light, because at the event horizon, the escape velocity is the speed of light. And the Relativity Cops say that’s a speed limit you can’t break.
But before you get to that point, you’ll have other things to worry about.
4) Spaghettification – Believe Me, The Sauce is Gross!
The late great astrophysicist Stephen Hawking popularized the term “spaghettification”.
As an object approaches a very strong gravitational field, it is subjected to extreme tidal forces which stretch the object vertically and compress it horizontally.
A solid object will, of course, resist this attempt to stretch it into a noodle. But in the case of black holes, as the object gets closer to it, the tidal force increases to such an extreme that it is stretched and compressed beyond its ability to resist.
For example, if you were approaching a black hole, feet-first in your spaceship, the gravity gradient (the difference in gravitational force exerted between one side of an object and the other) would pull on your feet with more force than it pulled on your head, thereby stretching you out like a string of spaghetti!
Eventually, you’ll get to the point where your body can’t resist the stretching and you (and your ship) would be torn apart, long before you got anywhere near the event horizon.
5) Singularity – The Devil in the Dark
The culprit causing all this mayhem is the singularity at the black hole’s center. It’s the very reason the black hole exists at all! As I mentioned earlier, the mass of the original star determines the radius of the event horizon, but what happens to that mass is mind-blowing!
The reason a singularity is called “a singularity” is because all of the mass that was once contained in the star is now collapsed into a single point. I’m not talking about a point the size of a house or even the size of the period at the end of this sentence. I’m talking about a zero-dimensional geometric point!
This is the aspect of black holes that have astrophysicists pulling their hair out. They know that singularities exist, but they don’t know how they exist! All of the star’s mass has been squeezed into a point of infinite density by infinite gravity while spacetime has reached infinite curvature.
In other words, at the singularity, time and space do not exist as we know them and our current understanding of the laws of physics do not apply.
Unlike stars, planets, galaxies, nebulae, etc., black holes don’t shine or reflect any light. (They are called black holes, after all!) They can only be found indirectly by finding their accretion disks, or by how they affect other nearby celestial objects.
They were predicted to exist by Einstein’s General Theory of Relativity in 1915, but none were discovered until 1971.
So, next time you take a peek through a telescope or binoculars, don’t expect to see one. But if you’re as fascinated by black holes as many professional and amateur astronomers are, that shouldn’t stop you from researching them and enjoying all the fascinating details about the latest discoveries concerning black holes!
Did you like this post? Did you hate it? I’d love to hear from you!
Shoot me a comment below and let me know what you think about
the post, the website, questions, or even suggestions for future posts. | 0.869751 | 3.627269 |
How fast the universe is expanding?
Patterns in the distribution of galaxies can help us measure the expansion of the universe.
The universe has been expanding ever since the Big Bang. But there is a problem.
We don’t know exactly how fast it is expanding because there are tiny discrepancies in one of the most fundamental and controversial numbers in physics.
The Hubble constant (Ho) tells us how fast an object is currently moving away from us, where the velocity of the object is proportional to its distance from us.
“The more distant the galaxy, the faster it’s moving,” explained astrophysicist Tamara Davis of the University of Queensland.
Knowing just how fast this expansion is happening can give us clues about how old the universe is and what it is made of.
The currently accepted value of the Hubble constant is 70 kilometres per second per megaparsec, plus or minus 5km. A megaparsec is approximately 3.26 million light-years.
That gives us an age of 13.7 billion years for the universe.
But lately, in what some astrophysicists have dubbed a “crisis in cosmology”, different techniques for measuring the Hubble constant have yielded slightly different figures.
“Does this small discrepancy we’re looking at now indicate we’ve discovered something profound and new about the universe that we haven’t explained yet?” Professor Davis said.
“Or does it mean we’ve just stuffed up our measurements, and we’re not measuring it as accurately as we think we are?”
In the latest attempt to tackle the problem, researchers have harnessed the magnifying power of galaxies to warp spacetime and bend light.
A constant history of controversy
The discovery that the universe was expanding — made in the 1920s by both Georges Lemaitre and Edwin Hubble independently — revolutionised how we viewed cosmology.
“It told us that the universe had a beginning, amongst other things, which was contrary to what scientific views had been at the time,” Professor Davis said.
Almost as soon as Lemaitre and Hubble came up with what is now known as the Hubble-Lemaitre Law, there has been controversy around the value of Ho.
They initially proposed the figure of 500 km per second per megaparsec.
But there was a problem; if the universe was expanding that fast it only took two billion years to get to the size it is today.
“That’s why a lot of people didn’t believe the result initially, and didn’t believe the universe actually had a beginning and a Big Bang,” Professor Davis said.
We also knew that the oldest stars we could see in the sky were around 13 to 14 billion years old.
What came before the Big Bang?
Lemaitre and Hubble based their measurements on the brightness of blinking stars known as Cephid variables.
“And with the telescopes that they had at the time, they just didn’t have the technology or the accuracy to do that very well,” Professor Davis said.
As telescope technology improved astrophysicists wavered between figures of 50km per second per megaparsec to 100km per second per megaparsec.
In 1998 two teams, including one headed by Brian Schmidt at the Australian National University, discovered the rate of expansion was accelerating. They proposed the acceleration was caused by dark energy, which makes up 70 per cent of the universe.
Soon after, astrophysicists reached a consensus on the Hubble constant.
“It got to the point where everyone was like ‘Ah, phew we’re done. We know the Hubble constant now. It’s 70’,” Professor Davis said.
The expansion of the universe was originally measured using blinking stars, called Cephid stars.
But two decades later, the debate has flared up again, as more techniques give slightly different answers.
“It’s like that old quote: ‘A person with one watch knows the time, a person with two watches is never sure’,” Professor Davis said.
Tiny discrepancies have cropped up as the methods used to measure the Hubble constant have become so precise.
“We’re not questioning the expansion, we’re not even questioning in great detail how old the universe is, we’re just questioning the very precise nature of a 1 per cent difference.”
How do we measure the constant?
There are two components to how we calculate the Hubble constant: velocity and distance.
Velocity is measured by the wavelength of electromagnetic radiation from an object.
If something is moving away from us, the wavelength of signals will move towards the red end of the electromagnetic spectrum (known as a red shift). If it is moving towards us, the signal will be more towards the blue end (known as a blue shift).
Distance is measured using either standard candles or standard rulers.
A standard candle is something that has a known brightness such as a Cephid star or, even more reliable, a supernova.
“By measuring how bright they appear, we can measure how far they are away,” Professor Davis said.
Supernovae such as Cassiopeia A are used as standard candles.
Standard rulers, on the other hand, use objects of a known size to calculate distance.
“We use big structures in the universe as a standard ruler,” Professor Davis said.
These include fluctuations in the afterglow of the Big Bang, known as the cosmic microwave background radiation, and patterns of galaxy distribution.
“We see the original patterns in the cosmic microwave background, which is essentially the afterglow from the Big Bang.”
Then billions of years later the pattern still persists in the pattern of galaxies we see because the galaxies formed from those original fluctuations.”
But it’s in these two methods of measuring distances where the problem for the Hubble constant arises.
“At moment the standard rulers are giving us numbers that are sort of 67 or 68km per second per megaparsec plus or minus about 0.5, whereas the standard candles are giving us numbers more like 73.5 plus or minus 1.”
What does warping spacetime tell us?
In the latest attempt to pin down the Hubble constant, researchers have used a technique called gravitational lensing to create a standard ruler.
This technique allows us to see more distant objects — in this case a quasar — using the gravitational power of closer galaxies.
Gravitational lensing bends spacetime and deflects light from distant objects.
“Gravity bends the path of light so we can see a distant object by light that’s travelled multiple different routes to reach us,” Professor Davis said.
The width between the different routes tells you how strong the gravity of the closer object is.
Not only does the light take different routes, but light travelling along those routes reaches us at different times so we detect one image of the background object before the other.
The measurement of this difference as well as the velocity of the rotating stars in the foreground galaxy gives us the mass of the foreground galaxy.
“We can compare that to how much bending we see and that gives us the standard ruler.”
Using this method, the researchers arrived at a figure of 82 km per second per megaparsecs, give or take 8 km, they reported in the journal Science.
That is higher than the current value for the Hubble constant, Professor Davis wrote in a separate commentary.
If correct, the number would make the universe younger than we think, but there is a big margin of error — the lower range (74km per second per megaparsec) is around the same figure given by standard candles — so the debate is far from over.
Other new methods, such as using gravitational waves from colliding stars to calculate Ho, could also help to solve the problem.
Why do we want to pin down this number?
Working out why there’s a difference in the distance measurement given by standard candles and standard rulers could help physicists solve some of the curliest questions in the cosmos.
If the different techniques really are measuring different expansion rates, it could mean something profound about the nature of gravity or the nature of our universe that has not been predicted by physics models.
“There’s still things we don’t understand about fundamental physics, and it’s getting harder and harder to find places where our predictions of fundamental physics don’t work,” Professor Davis said.
“But we still don’t know how the universe began.
“We still don’t know how to merge that beautiful theory of particles with our theory of gravity, and those two theories are actually contradictory in some ways.”
So when a number comes up that is different to what is predicted — albeit by a tiny margin — it could be significant.
“And debating whether it’s an observational error or it’s something that is more profound is exciting.” | 0.852662 | 4.016856 |
Robert Conrad, our Observing Chair, posted on Facebook about a close conjunction of Neptune with the 4.2 magnitude star Phi Aquarii in Aquarius. The pair will be less than 15 arc-seconds apart on Thursday, Sept 6th – that is about a third of Jupiter’s apparent size at opposition – so the pair will appear practically on top of each other.
But then just after midnight on Monday, Sept 9th (technically, it will be Tuesday at 00:07:12 am), Neptune reaches opposition when it is directly opposite the Sun as viewed from the Earth. Neptune will have moved slightly to the west of Phi Aquarii by then but is still close – within 10 arc=minutes.
If you haven’t seen Neptune then this is a great opportunity. Neptune is not visible to the naked-eye as its magnitude of 7.8 is well past the limit for naked-eye observations. You may get a glimpse of it using steady-supported binoculars but a 200x view through a 150 mm or larger telescope is required to resolve it into a disk. Either way, the 4.2 magnitude star Phi Aquarii is a good guide. AAVSO charts are on Robert’s post at:
Even better is to observe Neptune over several nights and notice its motion relative to Phi Aquarii. Neptune’s orbital period of 164.6 years makes it move slowly across the sky, it will still be together with Phi Aquarri in a one degree field of view on Oct 1st, 2019.
Recording the relative positions over several nights lets you avoids Galileo’s missed opportunity – there is evidence that Galileo observed Neptune on January 6th, 1613, and again on January 27, 1613 and noted a slight discrepancy in its position versus the background stars. However, there is no record that he made further observations and he likely thought it to be a fixed blue star rather than a planet.
Credit for Neptune’s discovery goes to Britain’s John Couch Adams and France’s Urbain Le Verrier who had worked out the position of a theoreticl 8th planet independently based on perturbations in the observed orbit of Uranus. Le Verrier’s analysis predicted the new planet’s location to with one degree of where it was observed by J. G. Galle and H. L. d’Arrest, staff astronomers at the Berlin Observatory, in 1846.
Neptune is a gas giant, like its near twin Uranus: it has more mass than Uranus but is slightly smaller because its greater mass cause more gravitational compression of its atmosphere. The methane in Neptune’s upper atmosphere absorbs the red light from the Sun but reflects the blue light from the Sun back into space. This is why Neptune appears blue. Neptune has the strongest winds of any planet in our solar system with wind speeds reaching 2,000 km/h, three time stronger than Jupiter’s. It has several large dark spots with the largest known as the Great Dark Spot – similar to the hurricane-like storms and the Great Red Spot on Jupiter. | 0.886335 | 3.584459 |
When NASA makes an investment, you know that whatever it is has to be something of galactic proportions.
The Arecibo Observatory in Puerto Rico is now one of those investments. Our space agency just gave $19 million to the University of Central Florida (which manages the observatory site for the National Science Foundation) for Arecibo to keep leveling up its asteroid patrol. Arecibo has some of the most hypersensitive planetary radar on Earth, and NASA wants that radar in its arsenal of instruments meant to keep rogue cosmic objects from smashing into us.
We’re already figuring out how to deflect asteroids, but if anyone is going to detect potentially dangerous NEOs (Near-Earth Objects) to take such action, it's the Arecibo Planetary Radar Group. They'll be spending up to 800 hours a year analyzing these objects, thanks in part to NASA funding.
“Our radar astrometry and characterization are critical for identifying objects that are truly hazardous to Earth and for the planning of mitigation efforts,” said Anne Virkki, the planetary radar program’s principal investigator.
Observations made at Arecibo could help NASA determine which NEOs may end up doing a face plant in our planet if they go unchecked — and what to do about them. Its William E. Gordon telescope is equipped with an S-band planetary radar system that is the most sensitive ever.
Arecibo has been zeroing in on suspicious NEOs since the mid-‘90s, with 60-120 objects analyzed each year. The observatory’s significance shot up after Congress made the identification of these objects a priority in 2005, when it made NASA responsible for finding out what things floating around in space could be dangerous. It was then that NASA decided to take preventative measures by requiring 90% of NEOs over 140 meters to be characterized by 2020.
While killer asteroids are a priority, they aren’t the only thing Arecibo is hunting. NASA can use its observations to decide on future scientific mission, which is how the OSIRIS-REx mission that studies Bennu (above) became a reality. It was data from Arecibo that convinced NASA that mission was worth backing. Some asteroids are also much trickier to land on than others, which explains why there was so much anxiety surrounding JAXA’s Hayabusa-2 mission to Ryugu, and how specific observations can tell space agencies where to go next.
The NASA grant will also give the observatory an assist with maintenance, operations, and system upgrades as the team sheds light on both threats and science opportunities.
“Arecibo plays an important role in discovery and advancing our knowledge of our solar system and our universe,” said facility director Francisco Cordova. “We also play a critical role in helping to protect our planet through providing knowledge and unique expertise. It’s part of our mission and one of the reasons we are so passionate about our work.” | 0.898925 | 3.260478 |
A simple electric circuit, where current is represented by the letter i. The relationship between the voltage (V), resistance (R), and current (I) is V=IR; this is known as Ohm's law.
An electric current is the rate of flow of electric charge past a point:2:622 or region.:614 An electric current is said to exist when there is a net flow of electric charge through a region.:832 Electric charge is carried by charged particles, so an electric current is a flow of charged particles. The moving particles are called charge carriers, and in different conductors may be different types of particle. In electric circuits the charge carriers are often electrons moving through a wire. In an electrolyte the charge carriers are ions, and in an ionized gas (plasma) are ions and electrons.
The SI unit of electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit:15 Electric current is measured using a device called an ammeter.:788
The conventional symbol for current is I, which originates from the French phrase intensité du courant, (current intensity). Current intensity is often referred to simply as current. The I symbol was used by André-Marie Ampère, after whom the unit of electric current is named, in formulating Ampère's force law (1820). The notation travelled from France to Great Britain, where it became standard, although at least one journal did not change from using C to I until 1896.
In a conductive material, the moving charged particles that constitute the electric current are called charge carriers. In metals, which make up the wires and other conductors in most electrical circuits, the positively charged atomic nuclei of the atoms are held in a fixed position, and the negatively charged electrons are the charge carriers, free to move about in the metal. In other materials, notably the semiconductors, the charge carriers can be positive or negative, depending on the dopant used. Positive and negative charge carriers may even be present at the same time, as happens in an electrolyte in an electrochemical cell.
A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers. The direction of conventional current is arbitrarily defined as the same direction as positive charges flow.
Since electrons, the charge carriers in metal wires and most other parts of electric circuits, have a negative charge, as a consequence, they flow in the opposite direction of conventional current flow in an electrical circuit.
Since the current in a wire or component can flow in either direction, when a variable I is defined to represent that current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram.[a]:13 This is called the reference direction of current I. If the current flows in the opposite direction, the variable I has a negative value. When analyzing electrical circuits, the actual direction of current through a specific circuit element is usually unknown until the analysis is completed. Consequently, the reference directions of currents are often assigned arbitrarily. When the circuit is solved, a negative value for the variable means that the actual direction of current through that circuit element is opposite that of the chosen reference direction.[b]:29
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship:
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.
Alternating and direct current
In alternating current (AC) systems, the movement of electric charge periodically reverses direction. AC is the form of electric power most commonly delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. Certain applications use different waveforms, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. An important goal in these applications is recovery of information encoded (or modulated) onto the AC signal.
In contrast, direct current (DC) is the unidirectional flow of electric charge, or a system in which the movement of electric charge is in one direction only. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. An old name for direct current was galvanic current.
Man-made occurrences of electric current include the flow of conduction electrons in metal wires such as the overhead power lines that deliver electrical energy across long distances and the smaller wires within electrical and electronic equipment. Eddy currents are electric currents that occur in conductors exposed to changing magnetic fields. Similarly, electric currents occur, particularly in the surface, of conductors exposed to electromagnetic waves. When oscillating electric currents flow at the correct voltages within radio antennas, radio waves are generated.
In electronics, other forms of electric current include the flow of electrons through resistors or through the vacuum in a vacuum tube, the flow of ions inside a battery or a neuron, and the flow of holes within metals and semiconductors.
Current can be measured using an ammeter.
Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current. Devices, at the circuit level, use various techniques to measure current:
- Shunt resistors
- Hall effect current sensor transducers
- Transformers (however DC cannot be measured)
- Magnetoresistive field sensors
- Rogowski coils
- current clamps
Joule heating, also known as ohmic heating and resistive heating, is the process of power dissipation:36 by which the passage of an electric current through a conductor increases the internal energy of the conductor:846, converting thermodynamic work into heat.:846, fn. 5 The phenomenon was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current through the wire for a 30 minute period. By varying the current and the length of the wire he deduced that the heat produced was proportional to the square of the current multiplied by the electrical resistance of the wire.
This relationship is known as Joule's Law.:36 The SI unit of energy was subsequently named the joule and given the symbol J.:20 The commonly known SI unit of power, the watt (symbol: W), is equivalent to one joule per second.:20
In an electromagnet a coil of wires behaves like a magnet when an electric current flows through it. When the current is switched off, the coil loses its magnetism immediately.
Electric current produces a magnetic field. The magnetic field can be visualized as a pattern of circular field lines surrounding the wire that persists as long as there is current.
Magnetic fields can also be used to make electric currents. When a changing magnetic field is applied to a conductor, an electromotive force (EMF) is induced,:1004 which starts an electric current, when there is a suitable path.
When an electric current flows in a suitably shaped conductor at radio frequencies, radio waves can be generated. These travel at the speed of light and can cause electric currents in distant conductors.
Conduction mechanisms in various media
In metallic solids, electric charge flows by means of electrons, from lower to higher electrical potential. In other media, any stream of charged objects (ions, for example) may constitute an electric current. To provide a definition of current independent of the type of charge carriers, conventional current is defined as moving in the same direction as the positive charge flow. So, in metals where the charge carriers (electrons) are negative, conventional current is in the opposite direction to the overall electron movement. In conductors where the charge carriers are positive, conventional current is in the same direction as the charge carriers.
In a vacuum, a beam of ions or electrons may be formed. In other conductive materials, the electric current is due to the flow of both positively and negatively charged particles at the same time. In still others, the current is entirely due to positive charge flow. For example, the electric currents in electrolytes are flows of positively and negatively charged ions. In a common lead-acid electrochemical cell, electric currents are composed of positive hydronium ions flowing in one direction, and negative sulfate ions flowing in the other. Electric currents in sparks or plasma are flows of electrons as well as positive and negative ions. In ice and in certain solid electrolytes, the electric current is entirely composed of flowing ions.
In a metal, some of the outer electrons in each atom are not bound to the individual atom as they are in insulating materials, but are free to move within the metal lattice. These conduction electrons can serve as charge carriers, carrying a current. Metals are particularly conductive because there are many of these free electrons, typically one per atom in the lattice. With no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there is zero net current within the metal. At room temperature, the average speed of these random motions is 106 metres per second. Given a surface through which a metal wire passes, electrons move in both directions across the surface at an equal rate. As George Gamow wrote in his popular science book, One, Two, Three...Infinity (1947), "The metallic substances differ from all other materials by the fact that the outer shells of their atoms are bound rather loosely, and often let one of their electrons go free. Thus the interior of a metal is filled up with a large number of unattached electrons that travel aimlessly around like a crowd of displaced persons. When a metal wire is subjected to electric force applied on its opposite ends, these free electrons rush in the direction of the force, thus forming what we call an electric current."
When a metal wire is connected across the two terminals of a DC voltage source such as a battery, the source places an electric field across the conductor. The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the charge carrier in a typical solid conductor.
For a steady flow of charge through a surface, the current I (in amperes) can be calculated with the following equation:
More generally, electric current can be represented as the rate at which charge flows through a given surface as:
Electric currents in electrolytes are flows of electrically charged particles (ions). For example, if an electric field is placed across a solution of Na+ and Cl− (and conditions are right) the sodium ions move towards the negative electrode (cathode), while the chloride ions move towards the positive electrode (anode). Reactions take place at both electrode surfaces, neutralizing each ion.
Water-ice and certain solid electrolytes called proton conductors contain positive hydrogen ions ("protons") that are mobile. In these materials, electric currents are composed of moving protons, as opposed to the moving electrons in metals.
In certain electrolyte mixtures, brightly coloured ions are the moving electric charges. The slow progress of the colour makes the current visible.
Gases and plasmas
In air and other ordinary gases below the breakdown field, the dominant source of electrical conduction is via relatively few mobile ions produced by radioactive gases, ultraviolet light, or cosmic rays. Since the electrical conductivity is low, gases are dielectrics or insulators. However, once the applied electric field approaches the breakdown value, free electrons become sufficiently accelerated by the electric field to create additional free electrons by colliding, and ionizing, neutral gas atoms or molecules in a process called avalanche breakdown. The breakdown process forms a plasma that contains enough mobile electrons and positive ions to make it an electrical conductor. In the process, it forms a light emitting conductive path, such as a spark, arc or lightning.
Plasma is the state of matter where some of the electrons in a gas are stripped or "ionized" from their molecules or atoms. A plasma can be formed by high temperature, or by application of a high electric or alternating magnetic field as noted above. Due to their lower mass, the electrons in a plasma accelerate more quickly in response to an electric field than the heavier positive ions, and hence carry the bulk of the current. The free ions recombine to create new chemical compounds (for example, breaking atmospheric oxygen into single oxygen [O2 → 2O], which then recombine creating ozone [O3]).
Since a "perfect vacuum" contains no charged particles, it normally behaves as a perfect insulator. However, metal electrode surfaces can cause a region of the vacuum to become conductive by injecting free electrons or ions through either field electron emission or thermionic emission. Thermionic emission occurs when the thermal energy exceeds the metal's work function, while field electron emission occurs when the electric field at the surface of the metal is high enough to cause tunneling, which results in the ejection of free electrons from the metal into the vacuum. Externally heated electrodes are often used to generate an electron cloud as in the filament or indirectly heated cathode of vacuum tubes. Cold electrodes can also spontaneously produce electron clouds via thermionic emission when small incandescent regions (called cathode spots or anode spots) are formed. These are incandescent regions of the electrode surface that are created by a localized high current. These regions may be initiated by field electron emission, but are then sustained by localized thermionic emission once a vacuum arc forms. These small electron-emitting regions can form quite rapidly, even explosively, on a metal surface subjected to a high electrical field. Vacuum tubes and sprytrons are some of the electronic switching and amplifying devices based on vacuum conductivity.
Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.
In a semiconductor it is sometimes useful to think of the current as due to the flow of positive "holes" (the mobile positive charge carriers that are places where the semiconductor crystal is missing a valence electron). This is the case in a p-type semiconductor. A semiconductor has electrical conductivity intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 10−2 to 104 siemens per centimeter (S⋅cm−1).
In the classic crystalline semiconductors, electrons can have energies only within certain bands (i.e. ranges of levels of energy). Energetically, these bands are located between the energy of the ground state, the state in which electrons are tightly bound to the atomic nuclei of the material, and the free electron energy, the latter describing the energy required for an electron to escape entirely from the material. The energy bands each correspond to many discrete quantum states of the electrons, and most of the states with low energy (closer to the nucleus) are occupied, up to a particular band called the valence band. Semiconductors and insulators are distinguished from metals because the valence band in any given metal is nearly filled with electrons under usual operating conditions, while very few (semiconductor) or virtually none (insulator) of them are available in the conduction band, the band immediately above the valence band.
The ease of exciting electrons in the semiconductor from the valence band to the conduction band depends on the band gap between the bands. The size of this energy band gap serves as an arbitrary dividing line (roughly 4 eV) between semiconductors and insulators.
With covalent bonds, an electron moves by hopping to a neighboring bond. The Pauli exclusion principle requires that the electron be lifted into the higher anti-bonding state of that bond. For delocalized states, for example in one dimension – that is in a nanowire, for every energy there is a state with electrons flowing in one direction and another state with the electrons flowing in the other. For a net current to flow, more states for one direction than for the other direction must be occupied. For this to occur, energy is required, as in the semiconductor the next higher states lie above the band gap. Often this is stated as: full bands do not contribute to the electrical conductivity. However, as a semiconductor's temperature rises above absolute zero, there is more energy in the semiconductor to spend on lattice vibration and on exciting electrons into the conduction band. The current-carrying electrons in the conduction band are known as free electrons, though they are often simply called electrons if that is clear in context.
Current density and Ohm's law
Current density is the rate at which charge passes through a chosen unit area.:31 It is defined as a vector whose magnitude is the current per unit cross-sectional area.:749 As discussed in Reference direction, the direction is arbitrary. Conventionally, if the moving charges are positive, then the current density has the same sign as the velocity of the charges. For negative charges, the sign of the current density is opposite to the velocity of the charges.:749 In SI units, current density (symbol: j) is expressed in the SI base units of amperes per square metre.:22
In linear materials such as metals, and under low frequencies, the current density across the conductor surface is uniform. In such conditions, Ohm's law states that the current is directly proportional to the potential difference between two ends (across) of that metal (ideal) resistor (or other ohmic device):
where is the current, measured in amperes; is the potential difference, measured in volts; and is the resistance, measured in ohms. For alternating currents, especially at higher frequencies, skin effect causes the current to spread unevenly across the conductor cross-section, with higher density near the surface, thus increasing the apparent resistance.
The mobile charged particles within a conductor move constantly in random directions, like the particles of a gas. (More accurately, a Fermi gas.) To create a net flow of charge, the particles must also move together with an average drift rate. Electrons are the charge carriers in most metals and they follow an erratic path, bouncing from atom to atom, but generally drifting in the opposite direction of the electric field. The speed they drift at can be calculated from the equation:
- is the electric current
- is number of charged particles per unit volume (or charge carrier density)
- is the cross-sectional area of the conductor
- is the drift velocity, and
- is the charge on each particle.
Typically, electric charges in solids flow slowly. For example, in a copper wire of cross-section 0.5 mm2, carrying a current of 5 A, the drift velocity of the electrons is on the order of a millimetre per second. To take a different example, in the near-vacuum inside a cathode ray tube, the electrons travel in near-straight lines at about a tenth of the speed of light.
Any accelerating electric charge, and therefore any changing electric current, gives rise to an electromagnetic wave that propagates at very high speed outside the surface of the conductor. This speed is usually a significant fraction of the speed of light, as can be deduced from Maxwell's equations, and is therefore many times faster than the drift velocity of the electrons. For example, in AC power lines, the waves of electromagnetic energy propagate through the space between the wires, moving from a source to a distant load, even though the electrons in the wires only move back and forth over a tiny distance.
The ratio of the speed of the electromagnetic wave to the speed of light in free space is called the velocity factor, and depends on the electromagnetic properties of the conductor and the insulating materials surrounding it, and on their shape and size.
The magnitudes (not the natures) of these three velocities can be illustrated by an analogy with the three similar velocities associated with gases. (See also hydraulic analogy.)
- The low drift velocity of charge carriers is analogous to air motion; in other words, winds.
- The high speed of electromagnetic waves is roughly analogous to the speed of sound in a gas (sound waves move through air much faster than large-scale motions such as convection)
- The random motion of charges is analogous to heat – the thermal velocity of randomly vibrating gas particles.
|Look up amperage in Wiktionary, the free dictionary.|
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ohm's law current proportional voltage resistance.
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Ohm's law current directly proportional.
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- Zangwill, Andrew (2013). Modern Electrodynamics. Cambridge University Press. ISBN 978-0-521-89697-9. | 0.80806 | 3.091542 |
For centuries, minerals were the only objects of study for crystallography. Today they are still important but the more ambitious challenges in this field are linked to worlds we do not know: extraterrestrial mineralogy, mineral processes in the deep interior of our planet, and the mineral chemistry of the initial states of the Earth and their possible role in the origin and infancy of life. The Curiosity rover exploring the surface of Mars carries on board the first X-ray diffraction device (CHEMIN) that has analysed Martian rock samples.
The first X-ray diffraction diagrams performed on Mars. They show the presence of gypsum and of clays, in other words showing a watery environment with neutral or lightly alkaline pH.
The exploration of outer space is an inevitable destiny of humanity. Getting to know the mineral composition of this outer world, including planets and moons, is the first vital step to future colonization. Designing and building new equipment that can develop crystallographic studies in those conditions is one of the challenges for 21st century science.
Meteorites, whether coming from the asteroid belt found between Mars and Jupiter, or whether provoked by impacts on other planets and moons, are made of different types of crystals. One of the challenges of mineralogy is to decode the information in the form, texture and structure of these crystals to reveal the history of our solar system.
We live on the Earth’s crust, a thin external layer of the Earth, which is only a few dozen kilometres thick. But the planet is an immense mineral sphere with a radius of almost 6,400 kilometres. In its depths, in the mantle and the core, mineral processes take place that directly affect the habitability and the ecosystems of the planet surface.
|The internal structure of Earth|
This deep crystalline world used to be the almost exclusive territory of science fiction. Its conditions of high pressure (millions of times the atmospheric pressure) and high temperature (up to 6500 ºC) made it practically inscrutable for experimental science. Today, diamond anvil cells enable us to reach these extraordinary pressures and at the same time follow the evolution of mineral transformations by X-ray diffraction. The information being obtained is completely changing our conception of the Earth’s interior and of its dynamics. The study of this fascinating world provides us with unpredictable discoveries and is another of the great scientific challenges of the future.
Putting a date on the moment when life appeared on planet Earth is crucial for understanding its origin and evolution as well as for understanding the actual geological evolution of our planet. Searching in the oldest rocks on Earth, palaeontologists have found microstructures from 3500 million years ago, which, due to their complex curve shapes, so different from typical crystalline forms, could be remains of the earliest life on Earth.
Biomorphs of silica and carbonate are self-organised crystalline materials created out of purely inorganic reactions that imitate forms of primitive life.
Surprisingly, it has been discovered that inorganic crystallization can create purely mineral structures that faithfully imitate primitive forms of life. Furthermore, they do so in chemical environments that most probably occurred on primitive Earth and that were very similar to those that created the ancient rocks that contain the supposed fossil remains.
Crystallization studies of self-organised mineral patterns are today a necessary tool for deciphering the authenticity of the possible remains of primitive life that are found in the oldest rocks on Earth, or in rocks of extraterrestrial origin. The two pictures above show stromatolitic structures created 2700 million years ago in Andalusians Hill, in the Tumbiana Formation, Australia.
Today there is no doubt that mineral reactions like serpentinization (the decomposition of the mineral olivine in the presence of water) are the source of carbon and simple organic molecules. Neither is there doubt that molecules like amino acids and lipids can be formed from non-biological reactions.
Partial decomposition of olivine by serpentinizatio.
However, the leap to structural and functional complexity that exists between these “simple” organic molecules created by mineral chemistry and the initial stages of earliest lift is enormous. A common idea is that the route that leads from one to the other must have been aided by efficient catalysers. It is thought that mineral crystalline structures were efficient catalytic substrates capable of empowering the self-assembly reactions of complicated organic structures.
One of the most explored groups of minerals is that of the clays. The surfaces of pyrite, the so-called iron-sulphur world, are the object of numerous studies.
Finally, the physical and chemical properties discovered in self-organised mineral patterns that are generated in extreme conditions make these structures a possible niche of interesting autocatalytic reactions.
The Earth is the only known planet in which matter has been able to self-organise into self-replicating structures with complex forms and behaviour, which we call life. How and where life originated is a mystery, probably the greatest mystery there is for us. The possible role of crystals and crystallization in the origin of life is also a mystery to be unravelled. | 0.833939 | 3.532582 |
NASA’s Wide Field Infrared Survey Telescope (WFIRST) will search for exoplanets, planets outside our solar system, toward the center of our Milky Way galaxy, where most stars are. Studying the properties of exoplanet worlds will help us understand what planetary systems throughout the galaxy are like and how planets form and evolve.
Combining WFIRST’s findings with results from NASA’s Kepler and Transiting Exoplanet Survey Satellite (TESS) missions will complete the first planet census that is sensitive to a wide range of planet masses and orbits, bringing us a step closer to discovering habitable Earth-like worlds beyond our own.
To date, astronomers have found most planets when they pass in front of their host star in events called transits, which temporarily dim the star's light. WFIRST data can spot transits too, but the mission will primarily watch for the opposite effect — little surges of radiance produced by a light-bending phenomenon called microlensing. These events are much less common than transits because they rely on the chance alignment of two widely separated and unrelated stars drifting through space.
"Microlensing signals from small planets are rare and brief, but they’re stronger than the signals from other methods,” said David Bennett, who leads the gravitational microlensing group at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Since it’s a one-in-a-million event, the key to WFIRST finding low-mass planets is to search hundreds of millions of stars.”
In addition, microlensing is better at finding planets in and beyond the habitable zone — the orbital distances where planets might have liquid water on their surfaces.
This effect occurs when light passes near a massive object. Anything with mass warps the fabric of space-time, sort of like the dent a bowling ball makes when set on a trampoline. Light travels in a straight line, but if space-time is bent — which happens near something massive, like a star — light follows the curve.
Any time two stars align closely from our vantage point, light from the more distant star curves as it travels through the warped space-time of the nearer star. This phenomenon, one of the predictions of Einstein’s general theory of relativity, was famously confirmed by British physicist Sir Arthur Eddington during a total solar eclipse in 1919. If the alignment is especially close, the nearer star acts like a natural cosmic lens, focusing and intensifying light from the background star.
Planets orbiting the foreground star may also modify the lensed light, acting as their own tiny lenses. The distortion they create allows astronomers to measure the planet’s mass and distance from its host star. This is how WFIRST will use microlensing to discover new worlds.
Familiar and exotic worlds
“Trying to interpret planet populations today is like trying to interpret a picture with half of it covered,” said Matthew Penny, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge who led a study to predict WFIRST’s microlensing survey capabilities. “To fully understand how planetary systems form we need to find planets of all masses at all distances. No one technique can do this, but WFIRST’s microlensing survey, combined with the results from Kepler and TESS, will reveal far more of the picture.”
More than 4,000 confirmed exoplanets have been discovered so far, but only 86 were found via microlensing. The techniques commonly used to find other worlds are biased toward planets that tend to be very different from those in our solar system. The transit method, for example, is best at finding sub-Neptune-sized planets that have orbits much smaller than Mercury’s. For a solar system like our own, transit studies could miss every planet.
WFIRST’s microlensing survey will help us find analogs to every planet in our solar system except Mercury, whose small orbit and low mass combine to put it beyond the mission’s reach. WFIRST will find planets that are the mass of Earth and even smaller — perhaps even large moons, like Jupiter’s moon Ganymede.
WFIRST will find planets in other poorly studied categories, too. Microlensing is best suited to finding worlds from the habitable zone of their star and farther out. This includes ice giants, like Uranus and Neptune in our solar system, and even rogue planets — worlds freely roaming the galaxy unbound to any stars.
While ice giants are a minority in our solar system, a 2016 study indicated that they may be the most common kind of planet throughout the galaxy. WFIRST will put that theory to the test and help us get a better understanding of which planetary characteristics are most prevalent.
Hidden gems in the galactic core
WFIRST will explore regions of the galaxy that haven’t yet been systematically scoured for exoplanets due to the different goals of previous missions. Kepler, for example, searched a modest-sized region of about 100 square degrees with 100,000 stars at typical distances of around a thousand light years. TESS scans the entire sky and tracks 200,000 stars, however their typical distances are around 100 light-years. WFIRST will search roughly 3 square degrees, but will follow 200 million stars at distances of around 10,000 light years.
Since WFIRST is an infrared telescope, it will see right through the clouds of dust that block other telescopes from studying planets in the crowded central region of our galaxy. Most ground-based microlensing observations to date have been in visible light, making the center of the galaxy largely uncharted exoplanet territory. A microlensing survey conducted since 2015 using the United Kingdom Infrared Telescope (UKIRT) in Hawaii is smoothing the way for WFIRST’s exoplanet census by mapping out the region.
The UKIRT survey is providing the first measurements of the rate of microlensing events toward the galaxy’s core, where stars are most densely concentrated. The results will help astronomers select the final observing strategy for WFIRST’s microlensing effort.
The UKIRT team’s most recent goal is detecting microlensing events using machine learning, which will be vital for WFIRST. The mission will produce such a vast amount of data that combing through it solely by eye will be impractical. Streamlining the search will require automated processes.
Additional UKIRT results point to an observing strategy that will reveal the most microlensing events possible while avoiding the thickest dust clouds that can block even infrared light.
“Our current survey with UKIRT is laying the groundwork so that WFIRST can implement the first space-based dedicated microlensing survey,” said Savannah Jacklin, an astronomer at Vanderbilt University in Nashville, Tennessee who has led several UKIRT studies. “Previous exoplanet missions expanded our knowledge of planetary systems, and WFIRST will move us a giant step closer to truly understanding how planets — particularly those within the habitable zones of their host stars — form and evolve.”
From brown dwarfs to black holes
The same microlensing survey that will reveal thousands of planets will also detect hundreds of other bizarre and interesting cosmic objects. Scientists will be able to study free-floating bodies with masses ranging from that of Mars to 100 times the Sun’s.
The low end of the mass range includes planets that were ejected from their host stars and now roam the galaxy as rogue planets. Next are brown dwarfs, which are too massive to be characterized as planets but not quite massive enough to ignite as stars. Brown dwarfs don’t shine visibly like stars, but WFIRST will be able to study them in infrared light through the heat left over from their formation.
Objects at the higher end include stellar corpses — neutron stars and black holes — left behind when massive stars exhaust their fuel. Studying them and measuring their masses will help scientists understand more about stars’ death throes while providing a census of stellar-mass black holes.
“WFIRST’s microlensing survey will not only advance our understanding of planetary systems,” said Penny, “it will also enable a whole host of other studies of the variability of 200 million stars, the structure and formation of the inner Milky Way, and the population of black holes and other dark, compact objects that are hard or impossible to study in any other way.”
The FY2020 Consolidated Appropriations Act funds the WFIRST program through September 2020. The FY2021 budget request proposes to terminate funding for the WFIRST mission and focus on the completion of the James Webb Space Telescope, now planned for launch in March 2021. The Administration is not ready to proceed with another multi-billion-dollar telescope until Webb has been successfully launched and deployed.
WFIRST is managed at Goddard, with participation by NASA's Jet Propulsion Laboratory and Caltech/IPAC in Pasadena, the Space Telescope Science Institute in Baltimore, and a science team comprising scientists from research institutions across the United States.
Banner: This illustration shows the concept of gravitational microlensing. When one star in the sky passes nearly in front of another, it can lens light from the background source star. If the nearer star hosts a planetary system, the planets can also act as lenses, each producing a short deviation in the brightness of the source. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
NASA’s Goddard Space Flight Center, Greenbelt, Md. | 0.947105 | 4.114504 |
Michael Perryman awarded prestigious Tycho Brahe Prize
6 June 2011Professor Michael Perryman, the scientific leader of ESA's Hipparcos mission, and a founding father of its successor mission, Gaia, has been awarded the 2011 Tycho Brahe Prize from the European Astronomical Society. The prize recognises the extraordinary work accomplished by Perryman in shepherding the field of astrometry to its successful leap into space-based observations and demonstrating the importance of measuring stellar positions for a plethora of astronomical applications.
Astrometry, the branch of astronomy dealing with the precise measurement of stellar positions, has a long history that dates back to ancient Greece and even earlier civilisations. The invention of the telescope in the seventeenth century represented a fundamental turning point in the field, allowing the compilation of larger and much more precise catalogues of stars than the famous ones created by Hipparchus (in the second century BC) and Tycho Brahe (in the sixteenth century AD), who had charted the sky with the naked eye.
The accuracy in astrometric measurements increased almost continuously throughout modern history, along with technological improvements to astronomical instrumentation, until it reached a point in the second half of the twentieth century when further significant improvements seemed beyond immediate reach. Observational barriers imposed by the Earth's atmosphere limited the accuracy that could be achieved with ground-based measurements of stellar positions: the next leap for astrometry would require a dedicated space telescope.
The Hipparcos mission was conceived in the late 1960s by French astronomer Pierre Lacroute and, when accepted into the ESA science programme in 1980, Perryman was appointed project scientist. In this role, he ensured that the scientific goals of the mission remained the key drivers throughout the development of the satellite. Hipparcos was launched in 1989 and, with Perryman assuming the role of operations manager in addition, observed for 3.5 years before operations ceased in March 1993.
The scientific reach of the Hipparcos mission has gone well beyond astrometry and has had profound implications for the fields of stellar and galactic astronomy, as well as cosmology and fundamental physics.
This prestigious award recognises Perryman's "crucial role in the fostering of high precision, global stellar astrometry from space, in particular the development of the Hipparcos mission," and acknowledges his pivotal work leading this fully European enterprise "through many difficulties to its ultimate success."
The exciting progress of the Hipparcos mission, from concept to launch and beyond, including an account of its many astronomical applications, is reported in Perryman's book "The Making of History's Greatest Star Map", published in 2010. The mission is also presented, in the broader framework of astrometry, in a comprehensive textbook also written by him, "Astronomical Applications of Astrometry: Ten Years of Exploitation of the Hipparcos Satellite Data", published in 2009.
Notes to Editors
The Tycho Brahe Prize of the European Astronomical Society is awarded annually in recognition of the development or exploitation of European instruments, or major discoveries based largely on such instruments.
ESA's Hipparcos space astrometry mission was a pioneering European project which pinpointed the three-dimensional positions of more than one hundred thousand stars with high precision, and more than one million stars with lesser precision.
Launched in August 1989 Hipparcos successfully observed the celestial sphere for 3.5 years before operations ceased in March 1993. Calculations from observations by the main instrument generated the Hipparcos Catalogue of 118 218 stars charted with the highest precision. An auxiliary star mapper pinpointed many more stars with lesser but still unprecedented accuracy, in the Tycho Catalogue of 1 058 332 stars. The Tycho 2 Catalogue, completed in 2000, brings the total to 2 539 913 stars, and includes 99 per cent of all stars down to magnitude 11, almost 100 000 times fainter than the brightest star, Sirius. Central to the mission's success were four major pan-European scientific teams: the Input Catalogue Consortium led by Dr Catherine Turon (Paris), the NDAC and FAST Data Analysis Consortia led by Prof. L. Lindegren (Lund) and Prof. J. Kovalevsky (Grasse) respectively, and the Tycho Data Analysis Consortium led by Prof. E. Hoeg (Copenhagen).
M. Perryman et al., "The Hipparcos Catalogue", A&A, 323, L49-52, 1997
M. Perryman, "The Making of History's Greatest Star Map", 2010 (book)
M. Perryman, "Astronomical Applications of Astrometry: Ten Years of Exploitation of the Hipparcos Satellite Data", 2009 (book) | 0.816652 | 3.360599 |
[tweetmeme only_single=false service=wp.me source=allinthegutter]
Ok, so you’re young, you’re surprisingly dusty, and you don’t match the models. No, not a picture of my geeky childhood, but the extrasolar planet HR 8799b. It orbits the star HR 8799 and, along with its two companions, is one of the two extrasolar planetary systems to be directly imaged, as shown above. Unsurprisingly it’s the dot labelled ‘b’.
If directly imaging extrasolar planets is hard (because they are so much fainter than their host stars), then taking spectra of them to study the composition of their atmospheres is, well, harder. This is just what astronomers at the University of Hawaii have managed to do for HR 8799b however, using the adaptive optics system on the Keck Telescope. To quote Trent Dupuy, one of the co-authors on the paper (from their handy press release),
Adaptive optics systems on Keck and other large ground-based telescopes make sharper images than even the Hubble Space Telescope. With adaptive optics, we are learning an incredible amount about objects that are smaller than the lowest-mass stars and larger than the most massive gas-giant planets in our solar system.
When they analysed their data they found little or no methane, which, since the amount of this gas can be used as a thermometer, meant that the planet is ~1200 Kelvin; this is ~400 Kelvin warmer than its predicted to be by the current best theoretical models. This, they think, is because it has more dust and clouds in its atmosphere than expected.
In related news, in a totally different part of the Galaxy, two more groups of astronomers (in Exeter and Florida) have also been taking spectra of two other extrasolar planets – HD 80606 b and XO-2b, this time using the Gran Telescopio Canarias. In these cases however, their big result is the first detection of potassium in their atmospheres, a result that this time was just what the modellers were expecting.
This is an exciting time for exoplanet work. The data are finally catching up with the models and, as usual some things match well, and some things raise more questions than they answer. Clearly, there are fun times ahead!
Brendan P. Bowler, Michael C. Liu, Trent J. Dupuy, Michael C. Cushing (2010). Near-Infrared Spectroscopy of the Extrasolar Planet HR 8799 b accepted by ApJ : 1008.4582
Knicole D. Colon, Eric B. Ford, Seth Redfield, Jonathan J. Fortney, Megan Shabram, Hans J. Deeg, & Suvrath Mahadevan (2010). Probing potassium in the atmosphere of HD 80606b with tunable filter
transit spectrophotometry from the Gran Telescopio Canarias submitted to MNRAS arXiv: 1008.4800v1
D. K. Sing, J.-M. Desert, J. J. Fortney, A. Lecavelier des Etangs, G. E. Ballester, J. Cepa, D. Ehrenreich, M. Lopez-Morales, F. Pont, M. Shabram, A. Vidal-Madjar (2010). GTC OSIRIS Transiting Exoplanet Atmospheric Survey: Detection of potassium in XO-2b from spectrophotometry submitted to A&A : 1008.4795 | 0.904023 | 3.833153 |
On December 15, 1612, Simon Marius (1573 — 1624) mathematician and astronomer, independently rediscovered the «Nebula in the Girdle of Andromeda», actually the Andromeda Galaxy (M31).
Marius was German astronomer, pupil of Tycho Brahe, one of the earliest users of the telescope and the first in print to make mention the Andromeda nebula.
He saw the object with a very moderate telescope and described it as looking like a «flame seen through horn».
He was not aware that this object had been noted previously by medieval Arab and Persian astronomers of the Middle Ages . Al Sufi (903-985 CE) known in the West as Azophi, was the first astronomer to describe the ‘nebulosity’ of the nebula in Andromeda in his book of constellations (atlas of heavens). Al Sufi was one of the most outstanding practical astronomers of the Middle Ages, as early as 964 AD.
The Andromeda galaxy is the most distant object in the sky that can be seen by the unaided eye.
Marius’ earliest astronomical activities also include observations of a comet in 1596 and of Kepler’s supernova in 1604. In 1608, he learned of telescopes and started to acquire the skills of producing one (like Galileo).
It is said that he independently discovered Jupiter’s Moons (despite Galileo’s claim of a plagiary, which had some evidence because it seems that he had already helped Capra in Padua to plagiate Galileo’s note describing the use of compass), and proposed the names they have since. | 0.883831 | 3.236735 |
Perpetual motion is the motion of bodies that continues forever. A perpetual motion machine is a hypothetical machine that can do work indefinitely without an energy source. This kind of machine is impossible, as it would violate the first or second law of thermodynamics.
These laws of thermodynamics apply regardless of the size of the system. For example, the motions and rotations of celestial bodies such as planets may appear perpetual, but are actually subject to many processes that slowly dissipate their kinetic energy, such as solar wind, interstellar medium resistance, gravitational radiation and thermal radiation, so they will not keep moving forever.
Thus, machines that extract energy from finite sources will not operate indefinitely, because they are driven by the energy stored in the source, which will eventually be exhausted. A common example is devices powered by ocean currents, whose energy is ultimately derived from the Sun, which itself will eventually burn out. Machines powered by more obscure sources have been proposed, but are subject to the same inescapable laws, and will eventually wind down.
In 2017, new states of matter, time crystals, were discovered in which on a microscopic scale the component atoms are in continual repetitive motion, thus satisfying the literal definition of "perpetual motion". However, these do not constitute perpetual motion machines in the traditional sense or violate thermodynamic laws because they are in their quantum ground state, so no energy can be extracted from them; they have "motion without energy".
The history of perpetual motion machines dates back to the Middle Ages. For millennia, it was not clear whether perpetual motion devices were possible or not, but the development of modern theories of thermodynamics has shown that they are impossible. Despite this, many attempts have been made to construct such machines, continuing into modern times. Modern designers and proponents often use other terms, such as "over unity", to describe their inventions.
Oh ye seekers after perpetual motion, how many vain chimeras have you pursued? Go and take your place with the alchemists.
There is a scientific consensus that perpetual motion in an isolated system violates either the first law of thermodynamics, the second law of thermodynamics, or both. The first law of thermodynamics is a version of the law of conservation of energy. The second law can be phrased in several different ways, the most intuitive of which is that heat flows spontaneously from hotter to colder places; relevant here is that the law observes that in every macroscopic process, there is friction or something close to it; another statement is that no heat engine (an engine which produces work while moving heat from a high temperature to a low temperature) can be more efficient than a Carnot heat engine operating between the same two temperatures.
In other words:
- In any isolated system, one cannot create new energy (law of conservation of energy). As a result, the thermal efficiency—the produced work power divided by the input heating power—cannot be greater than one.
- The output work power of heat engines is always smaller than the input heating power. The rest of the heat energy supplied is wasted as heat to the ambient surroundings. The thermal efficiency therefore has a maximum, given by the Carnot efficiency, which is always less than one.
- The efficiency of real heat engines is even lower than the Carnot efficiency due to irreversibility arising from the speed of processes, including friction.
Statements 2 and 3 apply to heat engines. Other types of engines which convert e.g. mechanical into electromagnetic energy, cannot operate with 100% efficiency, because it is impossible to design any system that is free of energy dissipation.
Machines which comply with both laws of thermodynamics by accessing energy from unconventional sources are sometimes referred to as perpetual motion machines, although they do not meet the standard criteria for the name. By way of example, clocks and other low-power machines, such as Cox's timepiece, have been designed to run on the differences in barometric pressure or temperature between night and day. These machines have a source of energy, albeit one which is not readily apparent, so that they only seem to violate the laws of thermodynamics.
Even machines which extract energy from long-lived sources - such as ocean currents - will run down when their energy sources inevitably do. They are not perpetual motion machines because they are consuming energy from an external source and are not isolated systems.
One classification of perpetual motion machines refers to the particular law of thermodynamics the machines purport to violate:
- A perpetual motion machine of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy.
- A perpetual motion machine of the second kind is a machine which spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However, it does violate the more subtle second law of thermodynamics (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.
- A perpetual motion machine of the third kind is usually (but not always)[self-published source] defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever due to its mass inertia (Third in this case refers solely to the position in the above classification scheme, not the third law of thermodynamics). It is impossible to make such a machine, as dissipation can never be completely eliminated in a mechanical system, no matter how close a system gets to this ideal (see examples in the Low Friction section).
"Epistemic impossibility" describes things which absolutely cannot occur within our current formulation of the physical laws. This interpretation of the word "impossible" is what is intended in discussions of the impossibility of perpetual motion in a closed system.
The conservation laws are particularly robust from a mathematical perspective. Noether's theorem, which was proven mathematically in 1915, states that any conservation law can be derived from a corresponding continuous symmetry of the action of a physical system. The symmetry which is equivalent to conservation of energy is the time invariance of physical laws. Therefore, if the laws of physics do not change with time, then the conservation of energy follows. For energy conservation to be violated to allow perpetual motion would require that the foundations of physics would change.
Scientific investigations as to whether the laws of physics are invariant over time use telescopes to examine the universe in the distant past to discover, to the limits of our measurements, whether ancient stars were identical to stars today. Combining different measurements such as spectroscopy, direct measurement of the speed of light in the past and similar measurements demonstrates that physics has remained substantially the same, if not identical, for all of observable time spanning billions of years.
The principles of thermodynamics are so well established, both theoretically and experimentally, that proposals for perpetual motion machines are universally met with disbelief on the part of physicists. Any proposed perpetual motion design offers a potentially instructive challenge to physicists: one is certain that it cannot work, so one must explain how it fails to work. The difficulty (and the value) of such an exercise depends on the subtlety of the proposal; the best ones tend to arise from physicists' own thought experiments and often shed light upon certain aspects of physics. So, for example, the thought experiment of a Brownian ratchet as a perpetual motion machine was first discussed by Gabriel Lippmann in 1900 but it was not until 1912 that Marian Smoluchowski gave an adequate explanation for why it cannot work. However, during that twelve-year period scientists did not believe that the machine was possible. They were merely unaware of the exact mechanism by which it would inevitably fail.
The law that entropy always increases, holds, I think, the supreme position among the laws of Nature. If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equations — then so much the worse for Maxwell's equations. If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.— Sir Arthur Stanley Eddington, The Nature of the Physical World (1927)
In the mid 19th-century Henry Dircks investigated the history of perpetual motion experiments, writing a vitriolic attack on those who continued to attempt what he believed to be impossible:
"There is something lamentable, degrading, and almost insane in pursuing the visionary schemes of past ages with dogged determination, in paths of learning which have been investigated by superior minds, and with which such adventurous persons are totally unacquainted. The history of Perpetual Motion is a history of the fool-hardiness of either half-learned, or totally ignorant persons."— Henry Dircks, Perpetuum Mobile: Or, A History of the Search for Self-motive (1861)
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One day man will connect his apparatus to the very wheelwork of the universe [...] and the very forces that motivate the planets in their orbits and cause them to rotate will rotate his own machinery.
Some common ideas recur repeatedly in perpetual motion machine designs. Many ideas that continue to appear today were stated as early as 1670 by John Wilkins, Bishop of Chester and an official of the Royal Society. He outlined three potential sources of power for a perpetual motion machine, "Chymical [sic] Extractions", "Magnetical Virtues" and "the Natural Affection of Gravity".
The seemingly mysterious ability of magnets to influence motion at a distance without any apparent energy source has long appealed to inventors. One of the earliest examples of a magnetic motor was proposed by Wilkins and has been widely copied since: it consists of a ramp with a magnet at the top, which pulled a metal ball up the ramp. Near the magnet was a small hole that was supposed to allow the ball to drop under the ramp and return to the bottom, where a flap allowed it to return to the top again. The device simply could not work. Faced with this problem, more modern versions typically use a series of ramps and magnets, positioned so the ball is to be handed off from one magnet to another as it moves. The problem remains the same.
Gravity also acts at a distance, without an apparent energy source, but to get energy out of a gravitational field (for instance, by dropping a heavy object, producing kinetic energy as it falls) one has to put energy in (for instance, by lifting the object up), and some energy is always dissipated in the process. A typical application of gravity in a perpetual motion machine is Bhaskara's wheel in the 12th century, whose key idea is itself a recurring theme, often called the overbalanced wheel: moving weights are attached to a wheel in such a way that they fall to a position further from the wheel's center for one half of the wheel's rotation, and closer to the center for the other half. Since weights further from the center apply a greater torque, it was thought that the wheel would rotate forever. However, since the side with weights further from the center has fewer weights than the other side, at that moment, the torque is balanced and perpetual movement is not achieved. The moving weights may be hammers on pivoted arms, or rolling balls, or mercury in tubes; the principle is the same.
Another theoretical machine involves a frictionless environment for motion. This involves the use of diamagnetic or electromagnetic levitation to float an object. This is done in a vacuum to eliminate air friction and friction from an axle. The levitated object is then free to rotate around its center of gravity without interference. However, this machine has no practical purpose because the rotated object cannot do any work as work requires the levitated object to cause motion in other objects, bringing friction into the problem. Furthermore, a perfect vacuum is an unattainable goal since both the container and the object itself would slowly vaporize, thereby degrading the vacuum.
To extract work from heat, thus producing a perpetual motion machine of the second kind, the most common approach (dating back at least to Maxwell's demon) is unidirectionality. Only molecules moving fast enough and in the right direction are allowed through the demon's trap door. In a Brownian ratchet, forces tending to turn the ratchet one way are able to do so while forces in the other direction are not. A diode in a heat bath allows through currents in one direction and not the other. These schemes typically fail in two ways: either maintaining the unidirectionality costs energy (requiring Maxwell's demon to perform more thermodynamic work to gauge the speed of the molecules than the amount of energy gained by the difference of temperature caused) or the unidirectionality is an illusion and occasional big violations make up for the frequent small non-violations (the Brownian ratchet will be subject to internal Brownian forces and therefore will sometimes turn the wrong way).
Buoyancy is another frequently misunderstood phenomenon. Some proposed perpetual-motion machines miss the fact that to push a volume of air down in a fluid takes the same work as to raise a corresponding volume of fluid up against gravity. These types of machines may involve two chambers with pistons, and a mechanism to squeeze the air out of the top chamber into the bottom one, which then becomes buoyant and floats to the top. The squeezing mechanism in these designs would not be able to do enough work to move the air down, or would leave no excess work available to be extracted.
Proposals for such inoperable machines have become so common that the United States Patent and Trademark Office (USPTO) has made an official policy of refusing to grant patents for perpetual motion machines without a working model. The USPTO Manual of Patent Examining Practice states:
With the exception of cases involving perpetual motion, a model is not ordinarily required by the Office to demonstrate the operability of a device. If operability of a device is questioned, the applicant must establish it to the satisfaction of the examiner, but he or she may choose his or her own way of so doing.
And, further, that:
A rejection [of a patent application] on the ground of lack of utility includes the more specific grounds of inoperativeness, involving perpetual motion. A rejection under 35 U.S.C. 101 for lack of utility should not be based on grounds that the invention is frivolous, fraudulent or against public policy.
The filing of a patent application is a clerical task, and the USPTO will not refuse filings for perpetual motion machines; the application will be filed and then most probably rejected by the patent examiner, after he has done a formal examination. Even if a patent is granted, it does not mean that the invention actually works, it just means that the examiner believes that it works, or was unable to figure out why it would not work.
The USPTO maintains a collection of Perpetual Motion Gimmicks.
The United Kingdom Patent Office has a specific practice on perpetual motion; Section 4.05 of the UKPO Manual of Patent Practice states:
Processes or articles alleged to operate in a manner which is clearly contrary to well-established physical laws, such as perpetual motion machines, are regarded as not having industrial application.
Examples of decisions by the UK Patent Office to refuse patent applications for perpetual motion machines include:
- Decision BL O/044/06, John Frederick Willmott's application no. 0502841
- Decision BL O/150/06, Ezra Shimshi's application no. 0417271
The European Patent Classification (ECLA) has classes including patent applications on perpetual motion systems: ECLA classes "F03B17/04: Alleged perpetua mobilia ..." and "F03B17/00B: [... machines or engines] (with closed loop circulation or similar : ... Installations wherein the liquid circulates in a closed loop; Alleged perpetua mobilia of this or similar kind ...".
Apparent perpetual motion machinesEdit
As "perpetual motion" can exist only in isolated systems, and true isolated systems do not exist, there are not any real "perpetual motion" devices. However, there are concepts and technical drafts that propose "perpetual motion", but on closer analysis it is revealed that they actually "consume" some sort of natural resource or latent energy, such as the phase changes of water or other fluids or small natural temperature gradients, or simply cannot sustain indefinite operation. In general, extracting work from these devices is impossible.
Some examples of such devices include:
- The drinking bird toy functions using small ambient temperature gradients and evaporation. It runs until all water is evaporated.
- A capillary action-based water pump functions using small ambient temperature gradients and vapour pressure differences. With the "Capillary Bowl", it was thought that the capillary action would keep the water flowing in the tube, but since the cohesion force that draws the liquid up the tube in the first place holds the droplet from releasing into the bowl, the flow is not perpetual.
- A Crookes radiometer consists of a partial vacuum glass container with a lightweight propeller moved by (light-induced) temperature gradients.
- Any device picking up minimal amounts of energy from the natural electromagnetic radiation around it, such as a solar powered motor.
- Any device powered by changes in air pressure, such as some clocks (Cox's timepiece, Beverly Clock). The motion leeches energy from moving air which in turn gained its energy from being acted on.
- The Atmos clock uses changes in the vapor pressure of ethyl chloride with temperature to wind the clock spring.
- A device powered by radioactive decay from an isotope with a relatively long half-life; such a device could plausibly operate for hundreds or thousands of years.
- The Oxford Electric Bell and Karpen Pile driven by dry pile batteries.
- In flywheel energy storage, "modern flywheels can have a zero-load rundown time measurable in years".
- Once spun up, objects in the vacuum of space—stars, black holes, planets, moons, spin-stabilized satellites, etc.—dissipate energy very slowly, allowing them to spin for long periods. Tides on Earth are dissipating the gravitational energy of the Moon/Earth system at an average rate of about 3.75 terawatts.
- In certain quantum-mechanical systems (such as superfluidity and superconductivity), very low friction movement is possible. However, the motion stops when the system reaches an equilibrium state (e.g. all the liquid helium arrives at the same level.) Similarly, seemingly entropy-reversing effects like superfluids climbing the walls of containers operate by ordinary capillary action.
In some cases a thought (or gedanken) experiment appears to suggest that perpetual motion may be possible through accepted and understood physical processes. However, in all cases, a flaw has been found when all of the relevant physics is considered. Examples include:
- Maxwell's demon: This was originally proposed to show that the Second Law of Thermodynamics applied in the statistical sense only, by postulating a "demon" that could select energetic molecules and extract their energy. Subsequent analysis (and experiment) have shown there is no way to physically implement such a system that does not result in an overall increase in entropy.
- Brownian ratchet: In this thought experiment, one imagines a paddle wheel connected to a ratchet. Brownian motion would cause surrounding gas molecules to strike the paddles, but the ratchet would only allow it to turn in one direction. A more thorough analysis showed that when a physical ratchet was considered at this molecular scale, Brownian motion would also affect the ratchet and cause it to randomly fail resulting in no net gain. Thus, the device would not violate the laws of thermodynamics.
- Vacuum energy and zero-point energy: In order to explain effects such as virtual particles and the Casimir effect, many formulations of quantum physics include a background energy which pervades empty space, known as vacuum or zero-point energy. The ability to harness zero-point energy for useful work is considered pseudoscience by the scientific community at large. Inventors have proposed various methods for extracting useful work from zero-point energy, but none have been found to be viable, no claims for extraction of zero-point energy have ever been validated by the scientific community, and there is no evidence that zero-point energy can be used in violation of conservation of energy.
- Although the machine would not work, the idea was that water from the top tank turns a water wheel (bottom-left), which drives a complicated series of gears and shafts that ultimately rotate the Archimedes' screw (bottom-center to top-right) to pump water to refill the tank. The rotary motion of the water wheel also drives two grinding wheels (bottom-right) and is shown as providing sufficient excess water to lubricate them.
- The device shown is a "mass leverage" device, where the spherical weights on the right have more leverage than those on the left, supposedly creating a perpetual rotation. However, there are a greater number of weights on the left, balancing the device.
- Angrist, Stanley (January 1968). "Perpetual Motion Machines". Scientific American. 218 (1): 115–122. Bibcode:1968SciAm.218a.114A. doi:10.1038/scientificamerican0168-114.
- Derry, Gregory N. (2002-03-04). What Science Is and How It Works. Princeton University Press. p. 167. ISBN 978-1400823116.
- Roy, Bimalendu Narayan (2002). Fundamentals of Classical and Statistical Thermodynamics. John Wiley & Sons. p. 58. Bibcode:2002fcst.book.....N. ISBN 978-0470843130.
- "Definition of perpetual motion". Oxforddictionaries.com. 2012-11-22. Retrieved 2012-11-27.
- Sébastien Point, Free energy: when the web is freewheeling, Skeptikal Inquirer, January February 2018
- Taylor, J. H.; Weisberg, J. M. (1989). "Further experimental tests of relativistic gravity using the binary pulsar PSR 1913 + 16". Astrophysical Journal. 345: 434–450. Bibcode:1989ApJ...345..434T. doi:10.1086/167917.
- Weisberg, J. M.; Nice, D. J.; Taylor, J. H. (2010). "Timing Measurements of the Relativistic Binary Pulsar PSR B1913+16". Astrophysical Journal. 722 (2): 1030–1034. arXiv:1011.0718v1. Bibcode:2010ApJ...722.1030W. doi:10.1088/0004-637X/722/2/1030.
- Grossman, Lisa (18 January 2012). "Death-defying time crystal could outlast the universe". newscientist.com. New Scientist. Archived from the original on 2017-02-02.
- Cowen, Ron (27 February 2012). ""Time Crystals" Could Be a Legitimate Form of Perpetual Motion". scientificamerican.com. Scientific American. Archived from the original on 2017-02-02.
- Powell, Devin (2013). "Can matter cycle through shapes eternally?". Nature. doi:10.1038/nature.2013.13657. ISSN 1476-4687. Archived from the original on 2017-02-03.CS1 maint: ref=harv (link)
- Gibney, Elizabeth (2017). "The quest to crystallize time". Nature. 543 (7644): 164–166. Bibcode:2017Natur.543..164G. doi:10.1038/543164a. ISSN 0028-0836. PMID 28277535.CS1 maint: ref=harv (link)
- Simanek, Donald E. (2012). "Perpetual Futility: A short history of the search for perpetual motion". The Museum of Unworkable Devices. Donald Simanek's website, Lock Haven University. Retrieved 3 October 2013.
- quote originally from Leonardo's notebooks, South Kensington Museum MS ii p. 92 McCurdy, Edward (1906). Leonardo da Vinci's note-books. US: Charles Scribner's Sons. p. 64.
- Rao, Y. V. C. (2004). An Introduction to Thermodynamics. Hyderabad, India: Universities Press (India) Private Ltd. ISBN 978-81-7371-461-0. Retrieved 1 August 2010.
- An alternative definition is given, for example, by Schadewald, who defines a "perpetual motion machine of the third kind" as a machine that violates the third law of thermodynamics. See Schadewald, Robert J. (2008), Worlds of Their Own - A Brief History of Misguided Ideas: Creationism, Flat-Earthism, Energy Scams, and the Velikovsky Affair, Xlibris, ISBN 978-1-4363-0435-1. pp55–56[self-published source]
- Wong, Kau-Fui Vincent (2000). Thermodynamics for Engineers. CRC Press. p. 154. ISBN 978-0-84-930232-9.
- Akshoy, Ranjan Paul; Sanchayan, Mukherjee; Pijush, Roy (2005). Mechanical Sciences: Engineering Thermodynamics and Fluid Mechanics. Prentice-Hall India. p. 51. ISBN 978-8-12-032727-6.
- Barrow, John D. (1998). Impossibility: The Limits of Science and the Science of Limits. Oxford University Press. ISBN 978-0-19-851890-7.
- Goldstein, Herbert; Poole, Charles; Safko, John (2002). Classical Mechanics (3rd ed.). San Francisco: Addison Wesley. pp. 589–598. ISBN 978-0-201-65702-9.CS1 maint: ref=harv (link)
- "The perpetual myth of free energy". BBC News. 9 July 2007. Retrieved 16 August 2010.
In short, law states that energy cannot be created or destroyed. Denying its validity would undermine not just little bits of science - the whole edifice would be no more. All of the technology on which we built the modern world would lie in ruins.
- "CE410: Are constants constant?", talkorigins
- Harmor, Greg; Derek Abbott (2005). "The Feynman-Smoluchowski ratchet". Parrondo's Paradox Research Group. School of Electrical & Electronic Engineering, Univ. of Adelaide. Retrieved 2010-01-15.
- Dircks, Henry (1861). Perpetuum Mobile: Or, A History of the Search for Self-motive. p. 354. Retrieved 17 August 2012.
- Jenkins, Alejandro (2013). "Self-oscillation". Physics Reports. 525 (2): 167–222. arXiv:1109.6640. Bibcode:2013PhR...525..167J. doi:10.1016/j.physrep.2012.10.007.
- "600 Parts, Form, and Content of Application - 608.03 Models, Exhibits, Specimens". Manual of Patent Examining Procedure (8 ed.). August 2001.CS1 maint: ref=harv (link)
- "700 Examination of Applications II. UTILITY - 706.03(a) Rejections Under 35 U.S.C. 101". Manual of Patent Examining Procedure (8 ed.). August 2001.CS1 maint: ref=harv (link)
- Pressman, David (2008). Nolo (ed.). Patent It Yourself (13, illustrated, revised ed.). Nolo. p. 99. ISBN 978-1-4133-0854-9.
- "Manual of Patent Practice, Section 4" (PDF). United Kingdom Patent Office. Cite journal requires
|journal=(help)CS1 maint: ref=harv (link)
- See also, for more examples of refused patent applications at the United Kingdom Patent Office (UK-IPO), UK-IPO gets tougher on perpetual motion, IPKat, 12 June 2008. Consulted on June 12, 2008.
- "Patents Ex parte decision (O/044/06)" (PDF). Retrieved 2013-03-04.
- "Challenge decision" (PDF). patent.gov.uk/. Retrieved 2019-11-14.
- ECLA classes F03B17/04 and F03B17/00B. Consulted on June 12, 2008.
- WO application 2008037004, Kwok, James, "An energy storage device and method of use", published 2008-04-03
- Munk, W.; Wunsch, C (1998). "Abyssal recipes II: energetics of tidal and wind mixing". Deep-Sea Research Part I: Oceanographic Research Papers. 45 (12): 1977. Bibcode:1998DSRI...45.1977M. doi:10.1016/S0967-0637(98)00070-3.
- Ray, R. D.; Eanes, R. J.; Chao, B. F. (1996). "Detection of tidal dissipation in the solid Earth by satellite tracking and altimetry". Nature. 381 (6583): 595. Bibcode:1996Natur.381..595R. doi:10.1038/381595a0.
- Amber M. Aiken, Ph.D. "Zero-Point Energy: Can We Get Something From Nothing?" (PDF). U.S. Army National Ground Intelligence Center.
Forays into "free energy" inventions and perpetual-motion machines using ZPE are considered by the broader scientific community to be pseudoscience.
- "Perpetual motion, on season 8 , episode 2". Scientific American Frontiers. Chedd-Angier Production Company. 1997–1998. PBS. Archived from the original on 2006.
- Martin Gardner, "'Dr' Bearden's Vacuum Energy", Skeptical Inquirer, January/February 2007
- Matt Visser (3 October 1996). "What is the 'zero-point energy' (or 'vacuum energy') in quantum physics? Is it really possible that we could harness this energy?". Phlogistin / Scientific American. Archived from the original on August 18, 1997. Retrieved 31 May 2013.
- "FOLLOW-UP: What is the 'zero-point energy' (or 'vacuum energy') in quantum physics? Is it really possible that we could harness this energy?". Scientific American. 18 August 1997.
|Wikisource has the text of the 1911 Encyclopædia Britannica article Perpetual Motion.|
- Perpetual motion at Curlie
- The Museum of Unworkable Devices
- Maruyama, Koji; Nori, Franco; Vedral, Vlatko (2009). "Colloquium: The physics of Maxwell's demon and information". Reviews of Modern Physics. 81 (1): 1–23. arXiv:0707.3400. Bibcode:2009RvMP...81....1M. doi:10.1103/RevModPhys.81.1.
- "Perpetual Motion - Just Isn't." Popular Mechanics, January 1954, pp. 108–111.
- In Our Time: Perpetual Motion, BBC discussion with Ruth Gregory, Frank Close and Steven Bramwell, hosted by Melvyn Bragg, first broadcast 24 September 2015. | 0.88063 | 3.380412 |
Astronomers confirm that Earth's mini-moon has left the orbit
Back in February, scientists spotted a mini-moon around Earth’s orbit and predicted that it may not stay there very long. Recently, they have also confirmed that the mini-moon has now left.
The mini-moon found by astronomers back in February, referred to as 2020 CD3, was confirmed by astronomers to have left the Earth’s orbit. Spotted by researchers from the Catalina Sky Survey observatory, it has yet to be determined whether this mini-moon was simply an asteroid that got caught in the planet’s orbit or if it was a fragment from the moon itself. It is said to measure between three to six feet in diameter, making it a very small moon circling the planet. Astronomers had already revealed that CD3 was not going to stay within Earth’s orbit for very long as they have a very unstable orbit around the planet.
Although this may be the first time scientists paid close attention to CD3, scientists who have closely observed the mini-moon believe that it first entered the Earth’s orbit three years prior. CD3 is not the first mini-moon that circled Earth either as back in 2006, scientists found a near-Earth asteroid measuring nine meters in diameter circling the planet. This mini-moon was referred to as 2006 RH120, the asteroid was found to orbit the Sun, but RH120 was also known to approach Earth and the moon as well.
It was because of its constant close-approach, the gravitational pull captured RH120, and spent nine months orbiting the Earth before leaving in June of 2007.
Meanwhile, Express previously reported just how a scenario where the Earth would be pushed out of the Solar System would occur.
Although the chances of this happening are very, very slim, there is still a chance that it may happen, and according to researchers from Sharif University, it may be caused by a wandering star. According to Paul M. Sutter, “As a star nears the Solar System, it can start to change the orbit of the Earth. When the Earth and the interloper are near, our planet can get a little bit of energy, a gentle gravitational tug-of-the-leash from the foreign visitor.”
Sutter then explained the consequences that may occur should that happen. He explained that even as the Earth leaves the Solar System, not all life on the planet will die. “But we have to be really, really clever because almost all life on Earth derives its energy from the sunlight and photosynthesis.” | 0.875949 | 3.152531 |
According to a report titled “Planet formation around binary stars: Tatooine made easy” recently submitted to the Astrophysical Journal, a pair of astrophysicists– Ben Bromley of the University of Utah and Scott Kenyon of the Smithsonian Astrophysical Observatory–have discovered a fourth star in a system of planets named 30 Ari, thus raising the quantity of known planet-bearing quadruple-sun systems to two.
Study lead author Lewis Roberts of NASA’s Jet Propulsion Laboratory in Pasadena, California stated: “Star systems come in myriad forms. There can be single stars, binary stars, triple stars, even quintuple star systems. It’s amazing the way nature puts these things together.”
The planetary system 30 Ari is located 136 light-years away from the sun in the constellation Aries. Scientists found a giant planet in the system back in 2009. It is approximately 10 times larger than Jupiter.
It orbits its main star every 335 days. The astronomers also reported that two stars are about 1,670 astronomical units away. (An AU is equivalent to the distance between Earth and the sun or almost 93 million miles.)
The newly-discovered star orbits its companion one time every 80 years, at a reported distance of 22 astronomical units but it does not influence the orbit of the planet even though it is that close. The astronomers say this is highly unusual and will study it further.
This is only the second time that a planet has been located in a four-star system. The first four-star planet called PH1b or Kepler-64b was discovered in 2012 by scientists using data from NASA’s Kepler mission.
A planet with more than one sun is less fiction and more science these days as researchers have found more than one planet that is reminiscent of Star Wars’ Luke Skywalker’s fictional home planet Tatooine.
Bromley concludes: “We took our sweet numerical time to show that the ride around a pair of stars can be just as smooth as around one,” when it concerns the early steps of the formation of a planet. “The ‘made easy’ part is really saying the same recipe that works around the sun will work around Tatooine’s host stars.”
Star Wars’ Tatooine 2-Sun Planet Is Real? | 0.869853 | 3.456855 |
New giant wind storm swirling near Jupiter's South Pole joins family of six other cyclones
Information from this mission can shed light on the atmospheres of Jupiter and other fellow gas giants Saturn, Uranus and Neptune. They can also help scientists better understand Earth's cyclones, says the research team
Scientists have observed a never-seen-before storm swirling on Jupiter's South Pole. This newbie joins six other storms that have made the south polar region their home.
"These cyclones are a new weather phenomena that have not been seen or predicted before," says Cheng Li, a Juno scientist from the University of California, Berkeley, in a statement.
Information from this mission can shed light on the atmospheres of Jupiter and other fellow gas giants Saturn, Uranus and Neptune. Furthermore, they can help us better understand Earth's cyclones, says the research team.
NASA's Juno spacecraft captured the images of the new storm when it flew past the planet for the 22nd time. The spacecraft has been keeping its eyes on Jupiter since 2016, informing scientists about the planet's magnetic field, water and ammonia in the deep atmosphere and its auroras.
Jupiter is known for its storms, the most iconic of them being the Great Red Spot — that is three times the size of Earth.
What sets the new storm apart is its pattern. The seven storms on the south pole together look like a hexagon, with six wind storms positioning itself on the six peaks and another wind storm occupying the central position.
"It's like having a family where there is a mother in the center and [now] there is a new baby brother," Alessandro Mura, from Italy's National Institute for Astrophysics, told Cosmos.
Juno's earlier encounters had mapped six of the seven wind storms on the south pole. And scientists believed none of these six storms would allow the seventh one to join in.
"It almost appeared like the polar cyclones were part of a private club that seemed to resist new members," says Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio, in a statement.
But the 22nd flyby had a surprise in store for the team of scientists. The new observation showed a smaller cyclone being brought to life, as it joined six other storms.
"The new data indicates we went from a pentagon of cyclones surrounding one at the center to a hexagonal arrangement," says Alessandro Mura, a Juno co-investigator at the National Institute for Astrophysics in Rome.
"This new addition is smaller in stature than its six more established cyclonic brothers: It's about the size of Texas. Maybe data from future flybys will show the cyclone growing to the same size as its neighbors," says Mura.
This discovery was not an easy one. The spacecraft dodged death just before the discovery: Juno's orbit was going to carry the spacecraft into Jupiter's shadow, which meant that it would not receive sunlight for 12 long hours.
As the spacecraft is solar-powered, failing to draw energy from the sun could be a death knell for the mission.
"While the team was trying to figure out how to conserve energy and keep our core heated, the engineers came up with a completely new way out of the problem: Jump Jupiter's shadow," says Bolton.
"It was nothing less than a navigation stroke of genius. Lo and behold, the first thing out of the gate on the other side, we make another fundamental discovery," he adds.
"Thanks to our navigators and engineers, we still have a mission. What they did is more than just make our cyclone discovery possible. They made possible the new insights and revelations about Jupiter that lie ahead of us," Bolton adds. | 0.852004 | 3.474095 |
What’s the first thing that comes to mind when someone says Neptune? Mercury? Pluto? Nothing exciting. Saturn? RINGS! Everyone knows about the rings. It’s the first planet anyone who gets a telescope for Christmas looks for. It’s the planet that’s hardest to make for a school project, but no one complains because those rings are so darned cool! Bad news, ring fans. NASA just announced that the planet is suffering from something called “ring rain” which is causing the rings to disappear and Saturn will soon be just another Uranus without the funny name jokes.
“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour.”
James O’Donoghue, NASA researcher and lead author of a new study published in Icarus, puts the ring rain in terms anyone who has been in a swimming pool or collected rainwater in a can can understand. The ring rain was first detected by the Voyager I and II fly-bys. The Cassini probe, which crashed through Saturn’s rings in a blaze of mission-ending glory last year, found that Saturn’s rings, which surprisingly are made of water ice chunks ranging from microscopic to yards in diameter, are actually dropping onto to the planet’s surface in massive hail-like downpours.
“From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn’s equator, and the rings have less than 100 million years to live.”
While 100 million years seems like a long time, NASA says it’s a blink of an eye in planetary terms. Saturn is estimated to be 4 billion years old and the current condition of the rings suggests they’re in the second half of their lifespan. That means there was most likely a time when Saturn had no rings at all. What’s more, it implies that other planets may have also had rings at one point.
“However, if rings are temporary, perhaps we just missed out on seeing giant ring systems of Jupiter, Uranus and Neptune, which have only thin ringlets today!”
Rings around Uranus! (We’ll pause while you insert your favorite joke here.) Thomas Cravens, University of Kansas professor of physics and astronomy and co-author of a second study on rain rings, waxes sentimental on the fact that we should be grateful we’re alive at a time we can enjoy Saturn’s rings … while they last.
“If it’s not being replenished, the rings aren’t going to last — you’ve got a hole in your bucket. Jupiter probably had a ring that evolved into the current wispy ring, and it could be for similar reasons. Rings do come and go. At some point they gradually drain away unless somehow they’re getting new material.”
Is anything replenishing Saturn’s rings? It doesn’t appear that way, and the wispy rings around Jupiter, Neptune and (here it comes again) Uranus show what future astronomers and explorers can expect to see. However, there’s one ray of hope … if Saturn acquired those rings later in life, perhaps Earth can too.
If there’s life on Uranus, they should start writing their revenge jokes now. | 0.876174 | 3.414867 |
Determining the shapes of smaller asteroids is a bit of a challenge. There are over a thousand asteroids larger than 30 kilometers in diameter, and we simply don’t have the resources to make high resolution images of them. Worse, some of them are small enough that even observations with the Hubble telescope wouldn’t produce a very clear image.
One way we can get an idea of the shape of asteroids is to look at the brightness of an asteroid over time. These are known as light curves, and they can be taken by small-ground based telescopes. In fact, measuring light curves over time is one way amateur astronomers contribute data. Their results can be very high quality, such as this one by Emmanuel Conseil.
Asteroids tend to rotate as they orbit, and as they do, different sides of them face the Sun. The amount of light we see depends on the brightness of the asteroid’s surface (its albedo) and the amount of the surface that is in light and shadow. By looking at the light curve of an asteroid, we can learn not only about its period of rotation, but also about the shape of the asteroid.
By observing the light curves over time, we get an idea of the illuminated surface over time. We can then use computer models to simulate the effect with different shapes. By tweaking the shape to match the light curve data, we can get an idea of the overall shape of an asteroid, such as in the image below.
When the NEAR spacecraft reached the asteroid Eros in 2000, we were able to put this method to the test. Models of Eros based upon light curve data had already been created, and these were in good agreement with the actual shape of Eros as seen in close images. We can’t use the light curve method to determine high resolution features, but it does give us a good basic idea of the shape.
What’s interesting about this method is how relatively low-tech it is. Light curves are pretty easy to get. A desktop computer has enough power to model asteroid shapes. Not all cutting edge research in astronomy needs the latest equipment. | 0.825004 | 3.722274 |
From: Jet Propulsion Laboratory
Posted: Wednesday, February 18, 2009
PASADENA, Calif. -- There is more than one way to make a dwarf galaxy, and NASA's Galaxy Evolution Explorer has found a new recipe. The spacecraft has, for the first time, identified dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way.
The findings surprised astronomers because most galaxies form in association with a mysterious substance called dark matter or out of gas containing metals. The infant galaxies spotted by the Galaxy Evolution Explorer are springing up out of gas that lacks both dark matter and metals. Though never seen before, this new type of dwarf galaxy may be common throughout the more distant and early universe, when pristine gas was more pervasive.
Astronomers spotted the unexpected new galaxies forming inside the Leo Ring, a huge cloud of hydrogen and helium that traces a ragged path around two massive galaxies in the constellation Leo. The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light.
"This intriguing object has been studied for decades with world-class telescopes operating at radio and optical wavelengths," said David Thilker of Johns Hopkins University, Baltimore, Md. "Despite such effort, nothing except the gas was detected. No stars at all, young or old, were found. But when we looked at the ring with the Galaxy Evolution Explorer, which is remarkably sensitive to ultraviolet light, we saw telltale evidence of recent massive star formation. It was really unexpected. We are witnessing galaxies forming out of a cloud of primordial gas."
In a recent study, Thilker and his colleagues found the ultraviolet signature of young stars emanating from several clumps of gas within the Leo Ring. "We speculate that these young stellar complexes are dwarf galaxies, although, as previously shown by radio astronomers, the gaseous clumps forming these galaxies lack dark matter," he said. "Almost all other galaxies we know are dominated by dark matter, which acted as a seed for the collection of their luminous components--stars, gas and dust. What we see occurring in the Leo Ring is a new mode for the formation of dwarf galaxies in material remaining from the much earlier assembly of this galaxy group."
Our local universe contains two large galaxies, the Milky Way and the Andromeda galaxy, each with hundreds of billions of stars, and the Triangulum galaxy, with several tens of billions of stars. It also holds more than 40 much smaller dwarf galaxies, which have only a few billion stars. Invisible dark matter, detected by its gravitational influence, is a major component of both giant and dwarf galaxies with one exception-tidal dwarf galaxies.
Tidal dwarf galaxies condense out of gas recycled from other galaxies and have been separated from most of the dark matter with which they were originally associated. They are produced when galaxies collide and their gravitational masses interact. In the violence of the encounter, streamers of galactic material are pulled out away from the parent galaxies and the halos of dark matter that surround them.
Because they lack dark matter, the new galaxies observed in the Leo Ring resemble tidal dwarf galaxies, but they differ in a fundamental way. The gaseous material making up tidal dwarfs has already been cycled through a galaxy. It has been enriched with metals--elements heavier than helium-- produced as stars evolve. "Leo Ring dwarfs are made of much more pristine material without metals," said Thilker. "This discovery allows us to study the star formation process in gas that has not yet been enriched."
Large, pristine clouds similar to the Leo Ring may have been more common throughout the early universe, Thilker said, and consequently may have produced many dark-matter-lacking, dwarf galaxies yet to be discovered.
The results of the new study reporting star formation in the Leo Ring appear in the February 19, 2009, issue of the journal Nature.
Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the mission and built the science instrument. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. South Korea and France are the international partners in the mission.
// end // | 0.810377 | 4.054801 |
The globular cluster M3 (NGC 5272; mag 6.2) in Canes Venatici will be well placed, high in the sky. It will reach its highest point in the sky at around midnight local time.
At a declination of +28°22', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 41°S.
From Ashburn, it will be visible all night. It will become visible around 20:57 (EDT) as the dusk sky fades, 37° above your eastern horizon. It will then reach its highest point in the sky at 01:11, 79° above your southern horizon. It will be lost to dawn twilight around 05:24, 37° above your western horizon.
At magnitude 6.3, M3 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or small telescope.
The position of M3 is as follows:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 17 April 2017|
20 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location. | 0.901567 | 3.191306 |
The experiments performed in the Frascati National Laboratories concern the study of the structure of matter, nuclear and sub-nuclear physics, astrophysics and cosmology. As in all the fields of physics, also in these fields experimental and theoretical research go hand in hand, complementing each other and helping to establish jointly a set of new knowledge. Experimental results, sometimes unexpected and surprising, need to be understood within the context of consistent and predictive theories, which should be as complete as possible. In turn, these theories lead to the prediction of new phenomena, which must be subjected experimental verification in order to ascertain the effective validity of the particular theories they stem from.
With the advancement of knowledge and the increasing levels of complexity achieved by physical theories, these verifications require increasingly complex challenges, and it is not uncommon that several decades can elapse between the formulation of theoretical predictions and the corresponding experimental verifications. A recent example is the discovery of the Higgs boson, whose existence was first postulated around 1964 and whose actual discovery required almost 50 years, until the joint announcement of 14 July 2012, when the two experimental collaborations ATLAS and CMS at CERN in Geneva confirmed the discovery of a new particle with a mass of approx. 125 times the mass of the proton, and with characteristics compatible (within the margins of experimental error) with those predicted by the theory for the Higgs boson.
Another very recent example concerns the detection of gravitational waves, whose existence was predicted in 1916 by Albert Einstein as an inevitable consequence of his theory of General Relativity. On 14 September 2015, at 09:50:45 (Universal Time), the two Laser Interferometer Gravitational-wave Observatory (LIGO) detectors in the US simultaneously observed a gravitational wave signal originating from the merger of two blacks holes, of estimated mass approx. 36 and 29 times the mass of the Sun, which took place 1.3 billion light-years away from us. After careful verification and rigorous statistical analyses the discovery was officially announced by the LISA and VIRGO collaborations on 11 February 2016, exactly a century after the theoretical prediction.
One of the main research activities carried out by the Theory Group of the Frascati National Laboratories concerns the study of possible extensions and generalizations of the current theoretical model of fundamental interactions, the so-called “Standard Model” of elementary particles
LEARN MORE ABOUT THE STANDARD MODEL
LEARN MORE ABOUT THE STANDARD MODEL
In the Standard Model, the elementary constituents of matter are two kinds of particles, called quarks and leptons. These interact with each other through the exchange of other particles, so-called force mediators, corresponding to the four fundamental forces of nature: electromagnetic force, mediated by the exchange of photons, strong nuclear force, whose mediators are called gluons, weak nuclear force, mediated by the exchange of Z and W bosons and, finally, gravitational forces, which can be described by the exchange of particles called gravitons. Each of these forces is related to a symmetry principle, that uniquely determines all the properties of the corresponding mediators.
Quarks and leptons are grouped into three families, each consisting of two different types of quarks (up-type quarks and down-type quarks) and two types of leptons (charged leptons and neutral leptons or neutrinos), for a total of 12 elementary constituents. Ordinary matter essentially consists of the first family of particles [see figure]. The protons and neutrons that make up atomic nuclei are composed of up and down quarks of the first family. Atoms in turn consist of atomic nuclei and a sufficient number of electrons (charged leptons of the first family) to render (in normal conditions) atoms electrically neutral. Finally, electron neutrinos (neutral leptons of the first family) are produced in large quantities in nuclear fusion reactions inside stars. According to the Standard Model, the particles of the second and third family have identical properties from the point of view of the strong, weak and electromagnetic interactions, and differ from those of the first family only in terms of mass: as regards particles with electric charge (quarks and charged leptons), those of the third family have masses greater than those of the second family, which in turn have a masses greater than those of the first family. For neutrinos, on the other hand, we do not yet know how the mass values are ordered with respect to the first, second and third family, and the possibility of an “inverse” ordering, in which neutrinos of the third family are the lightest ones, still remains open. The larger mass of the quarks and charged leptons of the second and third family has an important consequence: these particles are unstable and, as a result of weak interactions, they decay very rapidly into quarks and leptons of the first family. This explains why ordinary matter, being stable, only consists of particles of the first family.
The Standard Model very successfully describes the interactions of the elementary constituents of matter in a wide energy range: from a few electron-volts (eV) corresponding to the binding energy of electrons in atoms, up to approx. 100 billion of electron-volts (100 GeV – giga electron-volts) corresponding to the masses of the W and Z mediator bosons (via Einstein’s formula E=mc2). However, the Standard Model is not able to explain certain experimental data of indisputable validity, such as the existence of Dark Matter, the non vanishing mass of the neutrinos, and why the Universe is dominated by matter rather than by antimatter. This, together with the self-consistency of the theory and considerations of “aesthetic elegance”, suggests that the formulation of a theory more fundamental than the Standard Model, a theory able to account for all the above experimental observations as well as to provide an accurate description of fundamental phenomena at energies higher than those hitherto explored, is by now a necessary breakthrough. In particular, there is a strong expectation that the CERN Large Hadron Collider, built to study the physics of the fundamental constituents at an energy of around one trillion of electron-volts (1 TeV – tera electron-volt), can reveal new phenomena indicating which way to follow in the formulation of the new theory.
One of the main problems of the Standard Model concerns the mechanism of generation of the masses of the elementary constituents. The symmetry that governs the electromagnetic and weak interactions implies that the mediators of these forces, as well as the quarks and the leptons, must have zero mass. This is in clear contrast with experimental evidences which indicate that only the photon and the mediators of the strong nuclear interaction (the gluons) are actually massless, while the W and Z bosons, mediators of the weak interactions, have masses respectively of 80 and 90 times the mass of the proton. In the Standard Model this problem is accommodated by interpreting the masses of the elementary constituents as the result of a new interaction: the interaction with the Higgs field. The Higgs field constitutes a sort of “homogeneous medium”, disseminated throughout the space, moving through which the various particles acquire their mass. This mechanism is technically consistent, and its validity has been clearly strengthened by the discovery of the Higgs boson. But at the same time, the mechanism raises a number of theoretical problems, because unlike the four fundamental forces, the interaction of the Higgs field is not based on a principle of symmetry, and for this reason the mechanism is highly unstable at high energies. This instability leads to the conclusion that at high energies (in particular of the order of the TeV) new particles or new interactions should appear. Moreover, it is not at all clear why quarks and leptons of the second and third family have a mass (i.e. an interaction with the Higgs field) much greater than those of the first family. In the Standard Model, the hierarchy of the masses of the fundamental constituents remains an unsolved mystery.
Among the extensions of the Standard Model that have been proposed, which can explain some of (but usually not all) the problems of the Standard Model, is supersymmetry, a new symmetry that interconnects particles with different spin (or intrinsic angular moment) and that envisages the existence of a multitude of new particles with masses of the order of the TeV, and also more “exotic” models, that even predict the existence of additional space-time dimensions.
Besides the study of possible extensions of the Standard Model, the interests of the Theory Group of the LNF cover the vastness of the interests of contemporary physics: from models for interpreting the possible nature of Dark Matter and for predicting some of its properties, to theories that attempt to explain the origin of the asymmetry between the components of matter and antimatter in our Universe. From the theoretical study of the microscopic structure of solid materials to the physics of nanotechnologies, from computer simulations of quantum chromodynamics, i.e. the modern theory of strong nuclear interactions, to the development of new research projects for the future of the laboratories. A large part of the theoretical activity carried out at the LNF regards numerical simulations of complex processes, both for nuclear as well as for condensed matter physics. Although the Standard Model is a mathematical model based on a few relatively simple rules, and containing a small number of elementary constituents, obtaining precise predictions for macroscopic processes from this model constitutes a problem of an unimaginable complexity. Just think of atomic nuclei, the molecules of organic systems or the structure, dynamics and evolution of different astrophysical systems (such as the star cores, the supernovae, neutron stars and black holes). In all these cases we deal with bound states of an extremely large number of elementary constituents, whose macroscopic behaviour can be deduced from the elementary laws only by means of controlled approximations, together with the implementation of complex numerical simulations run on powerful latest-generation computers. | 0.807056 | 3.474621 |
Although it might seem like a hard core physics article, it is in fact an application of the philosophical insight permeating this blog and my book.
This blog version contains the abstract, introduction and conclusions. The full version of the article is available as a PDF file.
Journal Reference: IJMP-D Vol. 16, No. 6 (2007) pp. 983–1000.
The softening of the GRB afterglow bears remarkable similarities to the frequency evolution in a sonic boom. At the front end of the sonic boom cone, the frequency is infinite, much like a Gamma Ray Burst (GRB). Inside the cone, the frequency rapidly decreases to infrasonic ranges and the sound source appears at two places at the same time, mimicking the double-lobed radio sources. Although a “luminal” boom violates the Lorentz invariance and is therefore forbidden, it is tempting to work out the details and compare them with existing data. This temptation is further enhanced by the observed superluminality in the celestial objects associated with radio sources and some GRBs. In this article, we calculate the temporal and spatial variation of observed frequencies from a hypothetical luminal boom and show remarkable similarity between our calculations and current observations.
A sonic boom is created when an object emitting sound passes through the medium faster than the speed of sound in that medium. As the object traverses the medium, the sound it emits creates a conical wavefront, as shown in Figure 1. The sound frequency at this wavefront is infinite because of the Doppler shift. The frequency behind the conical wavefront drops dramatically and soon reaches the infrasonic range. This frequency evolution is remarkably similar to afterglow evolution of a gamma ray burst (GRB).
Gamma Ray Bursts are very brief, but intense flashes of rays in the sky, lasting from a few milliseconds to several minutes, and are currently believed to emanate from cataclysmic stellar collapses. The short flashes (the prompt emissions) are followed by an afterglow of progressively softer energies. Thus, the initial rays are promptly replaced by X-rays, light and even radio frequency waves. This softening of the spectrum has been known for quite some time, and was first described using a hypernova (fireball) model. In this model, a relativistically expanding fireball produces the emission, and the spectrum softens as the fireball cools down. The model calculates the energy released in the region as — ergs in a few seconds. This energy output is similar to about 1000 times the total energy released by the sun over its entire lifetime.
More recently, an inverse decay of the peak energy with varying time constant has been used to empirically fit the observed time evolution of the peak energy using a collapsar model. According to this model, GRBs are produced when the energy of highly relativistic flows in stellar collapses are dissipated, with the resulting radiation jets angled properly with respect to our line of sight. The collapsar model estimates a lower energy output because the energy release is not isotropic, but concentrated along the jets. However, the rate of the collapsar events has to be corrected for the fraction of the solid angle within which the radiation jets can appear as GRBs. GRBs are observed roughly at the rate of once a day. Thus, the expected rate of the cataclysmic events powering the GRBs is of the order of — per day. Because of this inverse relationship between the rate and the estimated energy output, the total energy released per observed GRB remains the same.
If we think of a GRB as an effect similar to the sonic boom in supersonic motion, the assumed cataclysmic energy requirement becomes superfluous. Another feature of our perception of supersonic object is that we hear the sound source at two different location as the same time, as illustrated in Figure 2. This curious effect takes place because the sound waves emitted at two different points in the trajectory of the supersonic object reach the observer at the same instant in time. The end result of this effect is the perception of a symmetrically receding pair of sound sources, which, in the luminal world, is a good description of symmetric radio sources (Double Radio source Associated with Galactic Nucleus or DRAGN).
Radio Sources are typically symmetric and seem associated with galactic cores, currently considered manifestations of space-time singularities or neutron stars. Different classes of such objects associated with Active Galactic Nuclei (AGN) were found in the last fifty years. Figure 3 shows the radio galaxy Cygnus A, an example of such a radio source and one of the brightest radio objects. Many of its features are common to most extragalactic radio sources: the symmetric double lobes, an indication of a core, an appearance of jets feeding the lobes and the hotspots. Some researchers have reported more detailed kinematical features, such as the proper motion of the hotspots in the lobes.
Symmetric radio sources (galactic or extragalactic) and GRBs may appear to be completely distinct phenomena. However, their cores show a similar time evolution in the peak energy, but with vastly different time constants. The spectra of GRBs rapidly evolve from region to an optical or even RF afterglow, similar to the spectral evolution of the hotspots of a radio source as they move from the core to the lobes. Other similarities have begun to attract attention in the recent years.
This article explores the similarities between a hypothetical “luminal” boom and these two astrophysical phenomena, although such a luminal boom is forbidden by the Lorentz invariance. Treating GRB as a manifestation of a hypothetical luminal boom results in a model that unifies these two phenomena and makes detailed predictions of their kinematics.
In this article, we looked at the spatio-temporal evolution of a supersonic object (both in its position and the sound frequency we hear). We showed that it closely resembles GRBs and DRAGNs if we were to extend the calculations to light, although a luminal boom would necessitate superluminal motion and is therefore forbidden.
This difficulty notwithstanding, we presented a unified model for Gamma Ray Bursts and jet like radio sources based on bulk superluminal motion. We showed that a single superluminal object flying across our field of vision would appear to us as the symmetric separation of two objects from a fixed core. Using this fact as the model for symmetric jets and GRBs, we explained their kinematic features quantitatively. In particular, we showed that the angle of separation of the hotspots was parabolic in time, and the redshifts of the two hotspots were almost identical to each other. Even the fact that the spectra of the hotspots are in the radio frequency region is explained by assuming hyperluminal motion and the consequent redshift of the black body radiation of a typical star. The time evolution of the black body radiation of a superluminal object is completely consistent with the softening of the spectra observed in GRBs and radio sources. In addition, our model explains why there is significant blue shift at the core regions of radio sources, why radio sources seem to be associated with optical galaxies and why GRBs appear at random points with no advance indication of their impending appearance.
Although it does not address the energetics issues (the origin of superluminality), our model presents an intriguing option based on how we would perceive hypothetical superluminal motion. We presented a set of predictions and compared them to existing data from DRAGNs and GRBs. The features such as the blueness of the core, symmetry of the lobes, the transient and X-Ray bursts, the measured evolution of the spectra along the jet all find natural and simple explanations in this model as perceptual effects. Encouraged by this initial success, we may accept our model based on luminal boom as a working model for these astrophysical phenomena.
It has to be emphasized that perceptual effects can masquerade as apparent violations of traditional physics. An example of such an effect is the apparent superluminal motion, which was explained and anticipated within the context of the special theory of relativity even before it was actually observed. Although the observation of superluminal motion was the starting point behind the work presented in this article, it is by no means an indication of the validity of our model. The similarity between a sonic boom and a hypothetical luminal boom in spatio-temporal and spectral evolution is presented here as a curious, albeit probably unsound, foundation for our model.
One can, however, argue that the special theory of relativity (SR) does not deal with superluminality and, therefore, superluminal motion and luminal booms are not inconsistent with SR. As evidenced by the opening statements of Einstein’s original paper, the primary motivation for SR is a covariant formulation of Maxwell’s equations, which requires a coordinate transformation derived based partly on light travel time (LTT) effects, and partly on the assumption that light travels at the same speed with respect to all inertial frames. Despite this dependence on LTT, the LTT effects are currently assumed to apply on a space-time that obeys SR. SR is a redefinition of space and time (or, more generally, reality) in order to accommodate its two basic postulates. It may be that there is a deeper structure to space-time, of which SR is only our perception, filtered through the LTT effects. By treating them as an optical illusion to be applied on a space-time that obeys SR, we may be double counting them. We may avoid the double counting by disentangling the covariance of Maxwell’s equations from the coordinate transformations part of SR. Treating the LTT effects separately (without attributing their consequences to the basic nature of space and time), we can accommodate superluminality and obtain elegant explanations of the astrophysical phenomena described in this article. Our unified explanation for GRBs and symmetric radio sources, therefore, has implications as far reaching as our basic understanding of the nature of space and time.
Photo by NASA Goddard Photo and Video | 0.842672 | 3.723029 |
After completing its first year of observations in the southern sky, NASA’s Transiting Exoplanet Survey Satellite has spotted some intriguing new exoplanets only 31 light-years away from Earth.
Multiple exoplanets — planets orbiting stars outside our solar system — were discovered orbiting an M-dwarf star, called GJ 357 in the Hydra constellation. The star is 40% cooler than our sun and only about a third of the sun’s mass and size. A study describing the three planets was published this week in the journal Astronomy & Astrophysics.
The first exoplanet discovered around the star was GJ 357 b.
The exoplanet is 22% larger and 80% more massive than Earth, making it a super-Earth. It’s 11 times closer to its star than Mercury is to our sun and the researchers estimate that it has an average temperature of 490 degrees Fahrenheit. This does not account for any potential warming effects of an atmosphere if it has one. It completes one orbit around the star every 3.9 days.
“We describe GJ 357 b as a ‘hot Earth,'” said Enric Pallé, study co-author and astrophysicist at the Institute of Astrophysics of the Canary Islands. “Although it cannot host life, it is noteworthy as the third-nearest transiting exoplanet known to date and one of the best rocky planets we have for measuring the composition of any atmosphere it may possess.”
The researchers also discovered more signals of exoplanets in the system.
GJ 357 d, a super-Earth that is 6.1 times the Earth’s mass, is the most intriguing because it orbits the star at a distance where the temperature might be just right to support liquid water on the surface.
“GJ 357 d is located within the outer edge of its star’s habitable zone, where it receives about the same amount of stellar energy from its star as Mars does from the Sun,” said Diana Kossakowski, study co-author at at the Max Planck Institute for Astronomy. “If the planet has a dense atmosphere, which will take future studies to determine, it could trap enough heat to warm the planet and allow liquid water on its surface.”
The researchers don’t know if the super-Earth is rocky like our own planet, but it orbits the star every 55.7 days and has a temperature of negative 64 degrees Fahrenheit. An atmosphere could cause it to be warmer.
“This is exciting, as this is humanity’s first nearby super-Earth that could harbor life — uncovered with help from TESS, our small, mighty mission with a huge reach,” said Lisa Kaltenegger, study author, associate professor of astronomy and director of Cornell’s Carl Sagan Institute. “With a thick atmosphere, the planet GJ 357 d could maintain liquid water on its surface like Earth and we could pick out signs of life with upcoming telescopes soon to be online.”
In the middle of those two planets is GJ 357 c. It’s 3.4 times the mass of Earth and zips around the planet every 9.1 days, reaching a temperature of 260 degrees Fahrenheit.
“In a way, these planets were hiding in measurements made at numerous observatories over many years,” said Rafael Luque, study author and doctoral student at the Canary Islands institute, who led the discovery team. “It took TESS to point us to an interesting star where we could uncover them.” | 0.861883 | 3.854384 |
"We have lots of data on this event, have dedicated lots of observation time, and we just can't figure out what exploded," said Neil Gehrels of NASA Goddard Space Flight Center - lead author on one of four reports appearing in this week's edition of the journal Nature. "All the data seem to point to a new but perhaps not so uncommon kind of cosmic explosion."
Gamma-ray bursts typically fall into one of two categories, long or short. The long bursts last more than two seconds and appear to be from the core collapse of massive stars forming a black hole. Most such bursts come from the edge of the visible universe. Short bursts, which are under two seconds and often last just a few milliseconds, appear to be the merger of two neutron stars or a neutron star with a black hole, which subsequently creates a new or bigger black hole.
The burst in question lasted for 102 seconds, but it lacked the hallmark of a supernova, or star explosion, commonly seen shortly after long bursts. Also, the burst's host galaxy has a low star-formation rate with few massive stars that could produce supernovae and long gamma-ray bursts.
"This was close enough to detect a supernova if it existed," said Avishay Gal-Yam of Caltech, lead author on another Nature report. "Even Hubble didn't see anything."
Certain properties of the burst concerning its brightness and the arrival time of photons of various energies, called the lag-luminosity relationship, suggest that burst behaved more like a short burst (from a merger) than a long burst. Yet no theoretical model of mergers can support a sustained release of gamma-ray energy for 102 seconds.
"This is brand new territory; we have no theories to guide us," said Gehrels. | 0.877015 | 3.794502 |
Our spacecraft have reached nearly every corner of our solar system, from the barren sun baked world of Mercury to the (soon to be visited) frigid ice ball of Pluto. We’ve gazed at all of them from afar many times but there are precious few we have made even robotic footfall on, with only a single other heavenly body having human footprints on it. Still from those few where we’ve been able to punch through the atmosphere the scenery we’ve been greeted with has been both strangely familiar yet completely alien. Mars is most famous of these but few are aware of the descent video from the Huygens probe that it made on its way down to Titan’s surface:
Titan gets its thick orange atmosphere from its mostly nitrogen atmosphere being tainted by methane which is thought to be constantly refreshed by cryovolcanoes on its surface. Whilst the mountain ranges and valleys you see were formed in much the same way as they were here on Earth those lakes you see in between them aren’t water, but hydrocarbons. Indeed much of Titan’s surface is covered in what is essentially crude oil although making use of it for future missions would likely be more trouble than its worth.
Still it’s amazing to see worlds that are so like ours in one aspect yet completely foreign in so many other ways. This rare insight into what Titan looks like from on high is not only amazing to see but it has also provided invaluable insight into what Titan’s world actually is. I honestly could watch videos like this for hours as it’s just so mesmerizing to see the surface of worlds other than our own.
It’s almost scary how similar Earth and Venus are in some respects. We’re roughly the same size, with Earth edging Venus out by 300KMs in diameter, and consequently roughly the same mass as well. The similarities end when you start looking further however with Venus being the hottest planet in our solar system due to its runaway greenhouse effect, it’s atmosphere a choking combination of carbon dioxide, nitrogen and sulphur. If there was ever a warning about the devastating potential about greenhouse gases it is our celestial sister Venus, but in that chaos lies an abundance of scientific data that could help us better understand ourselves and, hopefully, avoid the same fate.
Studying Venus’ atmosphere isn’t an easy task however as those extreme conditions have meant that the longest our probes have managed to survive down there is a couple hours. We can still do a lot of good work with satellites and spectral analysis but there’s really no substitute for actually being in the atmosphere for an extended period of time. Strangely enough whilst Venus’ atmosphere might be one of the most unforgiving in our solar system its composition, made up primarily of heavy than air elements, provides an unique opportunity that an atmospheric study craft could take advantage of. A concept craft that does just this is called the Venus Atmospheric Maneuverable Platform (VAMP) by Northrop Grumman.
The VAMP is part airship, part traditional aircraft which would spend the majority of its life high in Venus’ atmosphere. To do this the VAMP craft is extremely light, on the order of 500kgs, but it has a wingspan that exceeds that of a Boeing 737. The craft itself would be inflatable, allowing VAMP to cruise at altitudes between 55KM and 70KM above Venus’ surface. It can do this because of the incredible density of Venus’ atmosphere which makes even regular breathable air from Earth a powerful lifting gas. The only limit to its lifespan in the Venusian atmosphere would be its power source and since it could take advantage of the freely available sun a platform like VAMP could run for an incredibly long time.
The concept is actually a rework of another one that was designed to fly through the atmosphere of Saturn’s moon Titan, a mission many have wanted to undertake since the Huygens probe landed there a decade ago. The challenges of flying an aircraft there are far greater than that of Venus, primarily due to the much thinner atmosphere and huge drop in solar radiation to take advantage of. It would still be doable of course, however the mission profile you’d have to go with would have to be much less ambitious and the time frames much shorter. Still it surprises me that the concept didn’t go the other way around as putting balloons in Venus’ atmosphere has always been a concept that many wanted to explore.
Northrop Grumman appears to be quite serious about the VAMP project as they outlined many objectives they wanted to achieve for it back in 2013. I can’t seem to find much more on it unfortunately which means it’s likely still in the concept phase, hoping for a mission profile to come along that suits it. Considering how many incredible envelope pushing missions we’ve had of late I don’t think something like VAMP is too far out of left field, especially considering that it’s based on already proven technologies. Still it doesn’t seem like it will be too long before we have a plane soaring through another world’s atmosphere, another science fiction dream becoming a reality.
I romanticize space quite a lot here and in real life as well. The sheer scale of our universe is something that is so mind boggling that I simply have no choice but it stand in awe of it constantly, lest I become overwhelmed with the sheer insignificance of my life when compared to it. Still even with my helplessly deluded romantic view I still recognise that the universe is one harsh mistress and humanity’s entire existence is just a tiny blip on the greater timeline of the universe.
Knowing this one of my close friends proposed a question to me last night which he had seen on a craigslist ad some time ago. Whilst the ad has unfortunately been taken down there are still a couple news articles around to give you the general idea of the question:
Just look at the first, enticing sentence of the ad: “Astronaut needed for experimental flight to Titan.”
Perhaps you might be concerned that this ad was not, in fact, placed by NASA. Please, let me put your mind into horizontal mode. The advertiser assures all applicants that he has been “working on this project for near 40 years.” Indeed, the only reason he is seeking an Armstrong for his flight is that he himself seems to have weaker limbs now that the years have passed.
In the advertiser’s own persuasive and humane words: “I am certain you will make it safely to Titan but there will not be enough fuel to get home. This is for someone unique that has always wanted to see the universe first-hand and has perhaps a terminal view on life here at home. Here’s your shot at romantic history.”
For a moment suspend the notion that this is just some crackpot putting up a free ad on the Internet to get some lulz and take a step back to analyze the question. Would you, given the opportunity, be willing to travel further than any other human has before into some of the deepest reaches of the solar system and cement your place firmly in the history books at the cost of never coming back? It’s an intriguing notion and one that I initially struggled to find an appropriate answer for.
Then it dawned on me. Such an adventure is not noble nor romantic. It is, above all, a completely selfish endeavour.
The idea of long term space travel is one of those things that gets me all excited about all the possibility that such a thing would bring. Colonies on other worlds, telescopes showing completely different views of the universe and one day the hopes of finding another form of intelligent life. We’re quite capable of keeping people up in orbit for months at a time currently but we haven’t been able to send people off on their lonesome for more than a couple weeks. The question gives you the impression that not only is his propulsion system highly advanced but so is the life support systems to. It takes about 3 years to get to Titan and that’s a problem that even NASA is struggling to find solutions for.
However despite the improbability of an actual solution to a lot of engineering problems you have to question the reason for sending a single human to a far off world without the possibility of them ever coming back. We could argue at lenght that there’s an enormous amount of science that could be done and there would be nothing more inspiring than another human actually visiting another world. But in reality the scientific achievements could be done much easier by robotic spacecraft so the value a human provides there is completely moot. The point was made that the moon landings grabbed the attention of the entire world at the moment we touched down and that such an endeavour to Titan would do the same.
It wouldn’t though. Had we not made it possible for the Apollo astronauts to return we would have scarred the moon forevermore as the place where we sent some of our best and brightest to die merely for the point of placing a flag. The same can be said for sending someone on a one way trip to Titan and I know that the world couldn’t be inspired by a man they sent away just to die alone on another world.
I believe that humanity must expand beyond our mother planet not only because of our innate desire to explore but also to protect ourselves as a species. There is so much to learn from leaving our home world that just can’t be done any other way that ignoring space feels tantamount to condemning ourselves to an eternal prison of this gravity well. Whilst the first to pioneer the frontiers of other planets will always be celebrated sending them to their graves becomes a purely selfish endeavour for all those involved. We can not conquer the challenges the universe puts in front of us by planting flags or being first at something. We conquer them by overcoming all the challenges, including the one of coming back home.
This is a wholly different idea from that of trying to accomplish something, say summiting mount Everest, which could end up with one losing their life. Such endeavours form the core of the human spirit, undertaking a challenge to push the limits of what was thought possible. I make the argument that all of those who attempted such journeys always had the intention of coming back down as I know of no one who has undertaken such missions just to die once they reached their destination.
So in the end I decided that no, I wouldn’t take the trip. Sacrificing my life, or anyone elses, just for the sake of putting my name in the history books is not worth the price of admission. Additionally such an endeavour achieves nothing for the greater cause of humanity and only serves to mar the destination with the death of a person who’s only ambition was to be remembered after they died. Whilst that is a hope that we all carry there is little value in throwing your life away in such an endeavour and I will never celebrate those condemn themselves to such fates. | 0.851691 | 3.735195 |
The Japan Aerospace Exploration Agency (JAXA) has confirmed that the tiny particles inside the Hayabusa spacecraft’s sample return container are in fact from the asteroid Itokawa. Scientists examined the particles to determine if the probe successfully captured and brought back anything from the asteroid, and in a press release said “about 1,500 grains were identified as rocky particles, and most were determined to be of extraterrestrial origin, and definitely from Asteroid Itokawa.”
These are the first samples from an asteroid ever returned to Earth;
the only other extraterrestrial samples brought back to Earth came from the Apollo missions to the Moon. See correction, below.
Previously, JAXA said that although particles were inside the container, it wasn’t clear if they were from the asteroid or if they could be of terrestrial origin (dust from Earth that could have been inside the container).
The particles samples were collected from the chamber by a specially shaped Teflon spatula and examined with a scanning electron microscope. There were two chambers inside the container, and from the press release (in Japanese) it appears all the particles were found in one chamber, Chamber A.
Most of the particles are extremely small, about 10 microns in size and require special handling and equipment. Unfortunately they aren’t the “peanut-sized” chunks of rock that the mission originally hoped to capture. This will make analyzing the particles difficult, but not impossible.
During the seven-year round trip journey, Hayabusa arrived at Itokawa in November, 2005. The mechanism that was intended to capture the samples apparently failed, but scientists were hopeful that at least some dust had made its way into the return canister. After a circuitous and troubled-filled return trip home, the sample return capsule was ejected and landed in Australia in June of this year.
Here are the other successful sample return missions:
Apollo Moon missions (1969-1972)
Soviet Union’s Luna 16 (1970) returned 101 grams of lunar soil
Luna 20 (1974) returned 30 grams
Luna 24 (1976) returned 170.1 grams.
The Orbital Debris Collection (ODC) experiment, deployed on the Mir space station for 18 months during 1996–1997, used aerogel to capture interplanetary dust particles in orbit.
Genesis (2001-2004) captured and returned molecules collected from the solar wind. It crashed in the Utah desert, but samples were able to be retreived.
Stardust (1999-2006) collected particles from the tail of a comet, as well as a few interstellar dust grains. | 0.850149 | 3.59779 |
“We have seen what we thought was unseeable,” said Shep Doeleman, an astronomer at the Harvard-Smithsonian Center for Astrophysics, and director of the effort to capture the image, during a Wednesday news conference in Washington, D.C. The image, of a lopsided ring of light surrounding a dark circle deep in the heart of a galaxy known as Messier 87, some 55 million light-years away from Earth, resembled the Eye of Sauron, a reminder yet again of the implacable power of nature. It is a smoke ring framing a one-way portal to eternity. https://www.nytimes.com/2019/04/10/science/black-hole-picture.html
The New York Times reported on the first image ever revealed of a massive black hole at the far reaches of the galaxy Messier 87 this week. Titled Darkness Visible, Finally: Astronomers Capture First Ever Image of a Black Hole, the article, by Dennis Overbye, was written with language that at times approached poetry and science fiction, with overtones of awe and wonder. Overbye used descriptors like monster, phrases such as portal into eternity, and described the image as the place where “according to Einstein’s theory, matter, space and time come to an end and vanish like a dream.”
The results of years of work by astronomers working in collaboration on several continents, Wednesday’s news was announced at six locations on Earth simultaneously. Overbye wrote, “When the image was put up on the screen in Washington, cheers and gasps, followed by applause, broke out in the room and throughout a universe of astrofans following the live-streamed event.”
It has taken a century of scientific investigation to prove that Einstein’s theory of relativity, from which his theory of black holes arose, is indeed true and no longer simply a theory. In the NYTimes article, Overbye quotes Priyamvada Natarajan, an astrophysicist at Yale, who said “Einstein must be delighted. His theory has just been stress-tested under conditions of extreme gravity, and looks to have held up.” And astrophysicist Kip Thorne wrote in an email, “It is wonderful to see the nearly circular shadow of the black hole. There can be no doubt this really is a black hole at the center of M87, with no signs of deviations from general relativity.”
It’s fascinating to read how the team of roughly 200 astronomers put together the data, collected from eight radio observatories on six mountains and four continents. The data was taken during a period of ten days in April of 2017, and took the next two years to compile it into the stunning images revealed to the world this week. Here is a link to that article: https://www.nytimes.com/interactive/2019/04/10/science/event-horizon-black-hole-images.html
It is not easy to describe in words the elation that many of us feel at reading this week’s news, and seeing the black hole images for the first time in history. But a feeling of vindication is part of the larger and more complex web of feelings surrounding the evidence. In a world fraught with opinions passing as truth, outright lies and human egotism run amok, it is such a breath of fresh air to see, with human eyes, an image of a cosmic reality so vast that it is impossible to comprehend. The black hole that lies in the heart of galaxy Messier 87 is nearly seven billion times the mass of our own sun. This is a moment when even scientists will turn to poetry and prophetic words from long ago, as we attempt to grasp the incomprehensible as it is presented to us. In so many ways, for human beings, seeing is believing. This week, we are finally able to see a black hole, a cosmic force incomprehensibly huge.
I looked up quotes by Dr. Carl Sagan, who was a master of writing about science and humanity with eloquence and clarity. Here are some of his thoughts on the relationship between humans and the cosmos, taken from his seminal book, Cosmos, first published in 1980. With gratitude to Dr. Sagan, I offer them to you, dear readers.
“The Cosmos is all that is or was or ever will be. Our feeblest contemplations of the Cosmos stir us — there is a tingling in the spine, a catch in the voice, a faint sensation, as if a distant memory, of falling from a height. We know we are approaching the greatest of mysteries.”
“The size and age of the Cosmos are beyond ordinary human understanding. Lost somewhere between immensity and eternity is our tiny planetary home. In a cosmic perspective, most human concerns seem insignificant, even petty. And yet our species is young and curious and brave and shows much promise. In the last few millennia we have made the most astonishing and unexpected discoveries about the Cosmos and our place within it, explorations that are exhilarating to consider. They remind us that humans have evolved to wonder, that understanding is a joy, that knowledge is prerequisite to survival. I believe our future depends on how well we know this Cosmos in which we float like a mote of dust in the morning sky.”
“The surface of the Earth is the shore of the cosmic ocean. On this shore, we’ve learned most of what we know. Recently, we’ve waded a little way out, maybe ankle-deep, and the water seems inviting. Some part of our being knows this is where we came from. We long to return, and we can, because the cosmos is also within us. We’re made of star stuff. We are a way for the cosmos to know itself.”
― Carl Sagan, Cosmos, via https://www.goodreads.com/work/quotes/3237312-cosmos | 0.87231 | 3.06668 |
Dust Jets (ESO NTT Image)
This is the ESO WWW Home Page for Comet 1996 B2 (Hyakutake) which was the brightest comet in the sky since 1976. It passed within 15 million kilometres (0.1 AU) of the Earth on March 25, 1996, and reached its perihelion on May 1, 1996.
The latest, published (ground-based) observation is from October 24.45, 1996. On this date a magnitude of 16.8 was measured and no coma was seen anymore. (G. J. Garradd, Loomberah, N.S.W., Australia).
This page will be updated if new information and images — in particular from the ESO La Silla observatory — become available. However, the comet is now very faint and it is not likely that this will happen very often.
Enormous Ion Tail Observed! (April 2000)
In early April 2000, reports were published about some very interesting observations made with the Ulysses spacecraft. Travelling at a distance of no less than 570 million km from the comet's head, changes in the solar wind were observed that can be identified as interaction with the comet's ion tail. This is the longest ion tail ever observed from any comet and indicate that comets, in particular those that are much larger and more active that Hyakutake, may influence the conditions in interplanetary space much more than previously thought.
Various accounts of this discovery have been published, first in the Aptil 5, 2000, issue of Nature . Look also at:
"Old" News (August 4, 1997)
On IAU Circular 6696, issued on 8 July, 1997, M. J. Mumma and collaborators report: We searched for soft x-ray radiation from comet C/1996 B2 on 1996 Mar. 21-24 (r = 1.11-1.05 AU, Delta = 0.15-0.105 AU), using the Extreme Ultraviolet Explorer orbiting observatory. An image of soft x-rays in the range 70-180 eV was obtained with the Deep Survey Camera. It shows crescent-shaped emission with total luminosity of 1.0 x 10 25 photon/s within an aperture radius of 120 000 km. The emission is offset by 42 000 km sunward from the nucleus in the sky plane. Spectra were acquired over the range 7-70 nm (180-18 eV) and show both spectral lines and continuum emission.
On 28 July, 1997, a press release was issued by the University of Wisconsin (Madison) concerning a report to be published on 1 August, 1997, in the journal Science. It presents evidence that small, evaporating ice particles in the tail and surrounding the nucleus of Comet Hyakutake are producing most of the water and other gases seen from Earth.
This page has been elected
Planet Science Site of the Day (March 25, 1996) | 0.845794 | 3.769302 |
17TH CENTURY MATHEMATICS
Logarithms were invented by John Napier, early in the 17th Century
In the wake of the Renaissance, the 17th Century saw an unprecedented explosion of mathematical and scientific ideas across Europe, a period sometimes called the Age of Reason. Hard on the heels of the “Copernican Revolution” of Nicolaus Copernicus in the 16th Century, scientists like Galileo Galilei, Tycho Brahe and Johannes Kepler were making equally revolutionary discoveries in the exploration of the Solar system, leading to Kepler’s formulation of mathematical laws of planetary motion.
The invention of the logarithm in the early 17th Century by John Napier (and later improved by Napier and Henry Briggs) contributed to the advance of science, astronomy and mathematics by making some difficult calculations relatively easy. It was one of the most significant mathematical developments of the age, and 17th Century physicists like Kepler and Newton could never have performed the complex calculatons needed for their innovations without it. The French astronomer and mathematician Pierre Simon Laplace remarked, almost two centuries later, that Napier, by halving the labours of astronomers, had doubled their lifetimes.
The logarithm of a number is the exponent when that number is expressed as a power of 10 (or any other base). It is effectively the inverse of exponentiation. For example, the base 10 logarithm of 100 (usually written log10 100 or lg 100 or just log 100) is 2, because 102 = 100. The value of logarithms arises from the fact that multiplication of two or more numbers is equivalent to adding their logarithms, a much simpler operation. In the same way, division involves the subtraction of logarithms, squaring is as simple as multiplying the logarithm by two (or by three for cubing, etc), square roots requires dividing the logarithm by 2 (or by 3 for cube roots, etc).
Although base 10 is the most popular base, another common base for logarithms is the number e which has a value of 2.7182818… and which has special properties which make it very useful for logarithmic calculations. These are known as natural logarithms, and are written loge or ln. Briggs produced extensive lookup tables of common (base 10) logarithms, and by 1622 William Oughted had produced a logarithmic slide rule, an instrument which became indispensible in technological innovation for the next 300 years.
Napier also improved Simon Stevin’s decimal notation and popularized the use of the decimal point, and made lattice multiplication (originally developed by the Persian mathematician Al-Khwarizmi and introduced into Europe by Fibonacci) more convenient with the introduction of “Napier’s Bones”, a multiplication tool using a set of numbered rods.
Graph of the number of digits in the known Mersenne primes
Although not principally a mathematician, the role of the Frenchman Marin Mersenne as a sort of clearing house and go-between for mathematical thought in France during this period was crucial. Mersenne is largely remembered in mathematics today in the term Mersenne primes – prime numbers that are one less than a power of 2, e.g. 3 (22-1), 7 (23-1), 31 (25-1), 127 (27-1), 8191 (213-1), etc. In modern times, the largest known prime number has almost always been a Mersenne prime, but in actual fact, Mersenne’s real connection with the numbers was only to compile a none-too-accurate list of the smaller ones (when Edouard Lucas devised a method of checking them in the 19th Century, he pointed out that Mersenne had incorrectly included 267-1 and left out 261-1, 289-1 and 2107-1 from his list).
The Frenchman René Descartes is sometimes considered the first of the modern school of mathematics. His development of analytic geometry and Cartesian coordinates in the mid-17th Century soon allowed the orbits of the planets to be plotted on a graph, as well as laying the foundations for the later development of calculus (and much later multi-dimensional geometry). Descartes is also credited with the first use of superscripts for powers or exponents.
Two other great French mathematicians were close contemporaries of Descartes: Pierre de Fermat and Blaise Pascal. Fermat formulated several theorems which greatly extended our knowlege of number theory, as well as contributing some early work on infinitesimal calculus. Pascal is most famous for Pascal’s Triangle of binomial coefficients, although similar figures had actually been produced by Chinese and Persian mathematicians long before him.
It was an ongoing exchange of letters between Fermat and Pascal that led to the development of the concept of expected values and the field of probability theory. The first published work on probability theory, however, and the first to outline the concept of mathematical expectation, was by the Dutchman Christiaan Huygens in 1657, although it was largely based on the ideas in the letters of the two Frenchmen.
Desargues’ perspective theorem
The French mathematician and engineer Girard Desargues is considered one of the founders of the field of projective geometry, later developed further by Jean Victor Poncelet and Gaspard Monge. Projective geometry considers what happens to shapes when they are projected on to a non-parallel plane. For example, a circle may be projected into an ellipse or a hyperbola, and so these curves may all be regarded as equivalent in projective geometry. In particular, Desargues developed the pivotal concept of the “point at infinity” where parallels actually meet. His perspective theorem states that, when two triangles are in perspective, their corresponding sides meet at points on the same collinear line.
By “standing on the shoulders of giants”, the Englishman Sir Isaac Newton was able to pin down the laws of physics in an unprecedented way, and he effectively laid the groundwork for all of classical mechanics, almost single-handedly. But his contribution to mathematics should never be underestimated, and nowadays he is often considered, along with Archimedes and Gauss, as one of the greatest mathematicians of all time.
Newton and, independently, the German philosopher and mathematician Gottfried Leibniz, completely revolutionized mathematics (not to mention physics, engineering, economics and science in general) by the development of infinitesimal calculus, with its two main operations, differentiation and integration. Newton probably developed his work before Leibniz, but Leibniz published his first, leading to an extended and rancorous dispute. Whatever the truth behind the various claims, though, it is Leibniz’s calculus notation that is the one still in use today, and calculus of some sort is used extensively in everything from engineering to economics to medicine to astronomy.
Both Newton and Leibniz also contributed greatly in other areas of mathematics, including Newton’s contributions to a generalized binomial theorem, the theory of finite differences and the use of infinite power series, and Leibniz’s development of a mechanical forerunner to the computer and the use of matrices to solve linear equations.
However, credit should also be given to some earlier 17th Century mathematicians whose work partially anticipated, and to some extent paved the way for, the development of infinitesimal calculus. As early as the 1630s, the Italian mathematician Bonaventura Cavalieri developed a geometrical approach to calculus known as Cavalieri’s principle, or the “method of indivisibles”. The Englishman John Wallis, who systematized and extended the methods of analysis of Descartes and Cavalieri, also made significant contributions towards the development of calculus, as well as originating the idea of the number line, introducing the symbol ∞ for infinity and the term “continued fraction”, and extending the standard notation for powers to include negative integers and rational numbers. Newton‘s teacher Isaac Barrow is usually credited with the discovery (or at least the first rigorous statrement of) the fundamental theorem of calculus, which essentially showed that integration and differentiation are inverse operations, and he also made complete translations of Euclid into Latin and English.
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Forward to Descartes >> | 0.843318 | 3.210213 |
In the early hours of August 30, a Ukrainian amateur astronomer named Gennady Borisov spotted a strange comet zooming through our solar system.
The object, named C/2019 Q4 (Borisov), was moving too fast for it to be captured by the sun's gravity and is most likely an interstellar interloper.
Today, the Minor Planet Centre announced the comet is likely to be only the second known interstellar object to make a pit stop in our corner of the galaxy.
In October 2017, astronomers identified an asteroid-like rock known as Oumuamua, the first known interstellar object to pass through our solar system.
Astronomers say the latest object appears to be a comet given what they have identified as a tail streaking behind the interstellar visitor while it moves through space.
The comet has a "coma", the fuzzy sheath of dust and gas that forms as sunlight heats up a comet's icy surface, meaning scientists will be able to collect much more data on its composition than they could for Oumuamua.
The centre released an official "circular" - a document detailing information on the object's orbit - which highlighted the apparent comet's eccentric pattern.
"Based on the available observations, the orbit solution for this object has converged to the hyperbolic elements shown below, which would indicate an interstellar origin," reads the document.
Estimates on C/2019 Q4 project that the object could remain within our solar system for between six months to a full year.
"We don't know how bright it's going to be. That's always an issue with comets, so you've got that unpredictability, combined with the fact that it is interstellar. And this is the first interstellar comet we've seen," astronomy-software developer Bill Gray, told Forbes.
The mysterious cigar-shaped projectile known as Oumuamua, formally named object 1I/2017 U1, resembles both a comet and an asteroid, however, it doesn't conform to many of the other defining features usually associated with these objects, including its direction of spin and lack of a tail.
When astronomers spotted Oumuamua, they had just three weeks to observe it before it left our solar system.
Professional stargazer Robert Weryk first spotted the interstellar traveller in October, 2017 at the University of Hawaii's Haleakala Observatory.
Researchers had just weeks to collect as much data as possible before the strange visitor travelled beyond the reach of Earth's telescopes.
The object is now out of sight but could take up to 20,000 years before it leaves our solar system onto its next destination.
Interstellar objects like the ones recently discovered are particularly exciting for astronomers since they offer a rare glimpse of what other parts of the galaxy may look like.
Astronomers will now be able to compare their findings on Oumuamua with the most recent specimen. | 0.903927 | 3.90318 |
How old is the sun? How does the sun shine? These questions are two sides of the same coin, as we shall see.
The rate at which the sun is radiating energy is easily computed by using the measured rate at which energy reaches the earth’s surface and the distance between the earth and the sun. The total energy that the sun has radiated away over its lifetime is approximately the product of the current rate at which energy is being emitted, which is called the solar luminosity, times the age of the sun.
The older the sun is, the greater the total amount of radiated solar energy. The greater the radiated energy, or the larger the age of the sun, the more difficult it is to find an explanation of the source of solar energy.
To better appreciate how difficult it is to find an explanation, let us consider a specific illustration of the enormous rate at which the sun radiates energy. Suppose we put a cubic centimeter of ice outside on a summer day in such a way that all of the sunshine is absorbed by the ice. Even at the great distance between the earth and the sun, sunshine will melt the ice cube in about 40 minutes. Since this would happen anywhere in space at the earth’s distance from the sun, a huge spherical shell of ice centered on the sun and 300 million km (200 million miles) in diameter would be melted at the same time. Or, shrinking the same amount of ice down to the surface of the sun, we can calculate that an area ten thousand times the area of the earth’s surface and about half a kilometer (0.3 mile) thick would also be melted in 40 minutes by the energy pouring out of the sun.
In this section, we shall discuss how nineteenth-century scientists tried to determine the source of solar energy, using the solar age as a clue.
Conflicting Estimates of the Solar Age
The energy source for solar radiation was believed by nineteenth-century physicists to be gravitation. In an influential lecture in 1854, Hermann von Helmholtz, a German professor of physiology who became a distinguished researcher and physics professor, proposed that the origin of the sun’s enormous radiated energy is the gravitational contraction of a large mass. Somewhat earlier, in the 1840’s, J. R. Mayer (another German physician) and J. J. Waterson had also suggested that the origin of solar radiation is the conversion of gravitational energy into heat.1
Biologists and geologists considered the effects of solar radiation, while physicists concentrated on the origin of the radiated energy. In 1859, Charles Darwin, in the first edition of On The Origin of the Species by Natural Selection, made a crude calculation of the age of the earth by estimating how long it would take erosion occurring at the current observed rate to wash away the Weald, a great valley that stretches between the North and South Downs across the south of England. He obtained a number for the “denudation of the Weald” in the range of 300 million years, apparently long enough for natural selection to have produced the astounding range of species that exist on earth.
As Herschel stressed, the sun’s heat is responsible for life and for most geological evolution on earth. Hence, Darwin’s estimate of a minimum age for geological activity on the earth implied a minimum estimate for the amount of energy that the sun has radiated.
Firmly opposed to Darwinian natural selection, William Thompson, later Lord Kelvin, was a professor at the University of Glasgow and one of the great physicists of the nineteenth century. In addition to his many contributions to applied science and to engineering, Thompson formulated the second law of thermodynamics and set up the absolute temperature scale, which was subsequently named the Kelvin scale in his honor. The second law of thermodynamics states that heat naturally flows from a hotter to a colder body, not the opposite. Thompson therefore realized that the sun and the earth must get colder unless there is an external energy source and that eventually the earth will become too cold to support life.
Kelvin, like Helmholtz, was convinced that the sun’s luminosity was produced by the conversion of gravitational energy into heat. In an early (1854) version of this idea, Kelvin suggested that the sun’s heat might be produced continually by the impact of meteors falling onto its surface. Kelvin was forced by astronomical evidence to modify his hypothesis and he then argued that the primary source of the energy available to the sun was the gravitational energy of the primordial meteors from which it was formed.
Thus, with great authority and eloquence Lord Kelvin declared in 1862:
That some form of the meteoric theory is certainly the true and complete explanation of solar heat can scarcely be doubted, when the following reasons are considered: (1) No other natural explanation, except by chemical action, can be conceived. (2) The chemical theory is quite insufficient, because the most energetic chemical action we know, taking place between substances amounting to the whole sun’s mass, would only generate about 3,000 years’ heat. (3) There is no difficulty in accounting for 20,000,000 years’ heat by the meteoric theory.
Kelvin continued by attacking Darwin’s estimate directly, asking rhetorically:
What then are we to think of such geological estimates as [Darwin’s] 300,000,000 years for the “denudation of the Weald”?
Believing Darwin was wrong in his estimate of the age of the earth, Kelvin also believed that Darwin was wrong about the time available for natural selection to operate.
Lord Kelvin estimated the lifetime of the sun, and by implication the earth, as follows. He calculated the gravitational energy of an object with a mass equal to the sun’s mass and a radius equal to the sun’s radius and divided the result by the rate at which the sun radiates away energy. This calculation yielded a lifetime of only 30 million years. The corresponding estimate for the lifetime sustainable by chemical energy was much smaller because chemical processes release very little energy.
Who was right?
As we have just seen, in the nineteenth century you could get very different estimates for the age of the sun, depending upon whom you asked. Prominent theoretical physicists argued, based upon the sources of energy that were known at that time, that the sun was at most a few tens of million years old. Many geologists and biologists concluded that the sun must have been shining for at least several hundreds of millions of years in order to account for geological changes and the evolution of living things, both of which depend critically upon energy from the sun. Thus the age of the sun, and the origin of solar energy, were important questions not only for physics and astronomy, but also for geology and biology.
Darwin was so shaken by the power of Kelvin’s analysis and by the authority of his theoretical expertise that in the last editions of On The Origin of the Species he eliminated all mention of specific time scales. He wrote in 1869 to Alfred Russel Wallace, the codiscoverer of natural selection, complaining about Lord Kelvin:
Thompson’s views on the recent age of the world have been for some time one of my sorest troubles.
Today we know that Lord Kelvin was wrong and the geologists and evolutionary biologists were right. Radioactive dating of meteorites shows that the sun is 4.6 billion years old.
What was wrong with Kelvin’s analysis? An analogy may help. Suppose a friend observed you using your computer and tried to figure out how long the computer had been operating. A plausible estimate might be no more than a few hours, since that is the maximum length of time over which a battery could supply the required amount of power. The flaw in this analysis is the assumption that your computer is necessarily powered by a battery. The estimate of a few hours could be wrong if you computer were operated from an electrical power outlet in the wall. The assumption that a battery supplies the power for your computer is analogous to Lord Kelvin’s assumption that gravitational energy powers the sun.
Since nineteenth century theoretical physicists did not know about the possibility of transforming nuclear mass into energy, they calculated a maximum age for the sun that was too short. Nevertheless, Kelvin and his colleagues made a lasting contribution to the sciences of astronomy, geology, and biology by insisting on the principle that valid inferences in all fields of research must be consistent with the fundamental laws of physics.
We will now discuss some of the landmark developments in the understanding of how nuclear mass is used as the fuel for stars.
1 von Helmholtz and Mayer were two of the codiscoverers of the law of conservation of energy. This law states that energy can be transformed from one form to another but the total amount is always conserved. Conservation of energy is a basic principle of modern physics that is used in analyzing the very smallest (sub-atomic) domains and the largest known structure (the universe), and just about everything in between. We shall see later that Einstein’s generalization of the law of conservation of energy was a key ingredient in understanding the origin of solar radiation. The application of conservation of energy to radioactivity revealed the existence of neutrinos.
A Gimpse of a Solution | 0.825026 | 4.109365 |
As we say goodbye to Leo season, and look ahead to Virgo, we have one last Royal who will test you, and your resolve. Will you be able to stand up to her challenge?
The Astronomy: 71 Niobe is a large, slowly rotating main-belt asteroid. It was discovered by the German astronomer Robert Luther on August 13, 1861, and named after Niobe, a character in Greek mythology. In 1861, the brightness of this asteroid was shown to vary by German astronomer Friedrich Tietjen. In 2006, it was examined by radar using the Arecibo Observatory radio telescope in Puerto Rico. This was supplemented by optical observations intended to build a lightcurve. The resulting estimated rotation period of 35.6 hours, or 1.48 Earth days, superseded an earlier estimate of the rotation period as 14.3 hours. The radar data produced an estimate of a maximum equatorial diameter of 94 km, which is consistent with earlier estimates based upon infrared data if the shape is assumed to be slightly elongated. The rotation period was further refined to 35.864 ± 0.001 hours during observations through 2010. Six stellar occultations of this asteroid between 2004 and 2007 produced chords ranging from 13–72 km (8–45 mi), which are statistically consistent with the published maximum diameter estimates.
The Myth: Niobe was a daughter of Tantalus and of either Dione, the most frequently cited, or of Eurythemista or Euryanassa, and the sister of Pelops and Broteas. She was mentioned in Homer’s Iliad which relates her proud hubris, for which she was punished by Leto, who sent Apollo and Artemis to slay all of her children, after which her children lay unburied for nine days while she abstained from food. Once the gods interred them, she retreated to her native Sipylus, “where Nymphs dance around the River Acheloos, and although being a stone, she broods over the sorrows sent from the Gods”. Later writers asserted that Niobe was wedded to Amphion, one of the twin founders of Thebes, where there was a single sanctuary where the twin founders were venerated, but in fact no shrine to Niobe. Niobe boasted of her fourteen children, seven male and seven female (the Niobids), to Leto who only had two children, the twins Apollo and Artemis. The number varies in different sources. Her speech which caused the indignation of the goddess was rendered in the following manner:
It was on occasion of the annual celebration in honor of Latona and her offspring, Apollo and Diana, when the people of Thebes were assembled, their brows crowned with laurel, bearing frankincense to the altars and paying their vows, that Niobe appeared among the crowd. Her attire was splendid with gold and gems, and her face as beautiful as the face of an angry woman can be. She stood and surveyed the people with haughty looks. “What folly,” said she, “is this! to prefer beings whom you never saw to those who stand before your eyes! Why should Latona be honored with worship rather than I? My father was Tantalus, who was received as a guest at the table of the gods; my mother was a goddess. My husband built and rules this city, Thebes; and Phrygia is my paternal inheritance. Wherever I turn my eyes I survey the elements of my power; nor is my form and presence unworthy of a goddess. To all this let me add, I have seven sons and seven daughters, and look for sons-in-law and daughters-in-law of pretensions worthy of my alliance. Have I not cause for pride? Will you prefer to me this Latona, the Titan’s daughter, with her two children? I have seven times as many. Fortunate indeed am I, and fortunate I shall remain! Will any one deny this?
Using arrows, Artemis killed Niobe’s daughters and Apollo killed Niobe’s sons. According to some versions, at least one Niobid (usually Meliboea) was spared. Their father, Amphion, at the sight of his dead sons, either killed himself or was killed by Apollo for having sworn revenge. Devastated, Niobe fled back to Mount Sipylus and was turned into stone, and, as she wept unceasingly, waters started to pour from her petrified complexion. Mount Sipylus indeed has a natural rock formation which resembles a female face, and it has been associated with Niobe since ancient times and described by Pausanias. The rock formation is also known as the “Weeping Rock”, since rainwater seeps through its porous limestone. The only Niobid spared stayed greenish pale from horror for the rest of her life, and for that reason she was called Chloris (the pale one).
Why She Matters: In astrological terms, Niobe is viewed mainly as a cautionary tale of Pride gone way too far, like Arachne. She is viewed as the worst possible scenario- Someone who is given much in life, is ungrateful and boastful, and who sees it all taken from her. She is also a foil for Artemis and Apollo, where their bloodlust is revealed- They are, at their core, hunters who will gleefully murder whatever prey their mother sets them to. In that sense they are far more Titan than Olympian. It is important to note that Niobe is part of the bloodline of Tantalus, and can be seen as sort of the end result of the Tantalus process- Once you finally get what you want, how will it change you? Who will you be upon the fulfillment of your desires? And if you were to lose it all, who are you then?
To find out where she shows up in your chart, go to astro.com, put in your birth details and in the extended options, all the way at the bottom, there will be a menu of additional objects. Under that is a blank space where you can enter the number 71, for Niobe. Once you have it entered, generate the chart! Where does Niobe affect your life? Let us know in the comments below! | 0.840239 | 3.25846 |
The Wide Field Infrared Survey Explorer (WISE) has been all snapped together and stuff and is ready to be launched into outer space from Vandenberg in November. This will be a major eye in the sky for cosmology, since it will be able to see things that heretofore only space insects could see....
Details in the following NASA press release:
PASADENA, Calif. -- NASA's Wide-field Infrared Survey Explorer, or WISE, has been assembled and is undergoing final preparations for a planned Nov. 1 launch from Vandenberg Air Force Base, Calif.
The mission will survey the entire sky at infrared wavelengths, creating a cosmic clearinghouse of hundreds of millions of objects -- everything from the most luminous galaxies, to the nearest stars, to dark and potentially hazardous asteroids. The survey will be the most detailed to date in infrared light, with a sensitivity hundreds of times better than that of its predecessor, the Infrared Astronomical Satellite.
"Most of the sky has never been imaged at these infrared wavelengths with this kind of sensitivity," said Edward Wright, the mission's principal investigator at UCLA. "We are sure to find many surprises."
On May 17, the mission's science instrument was delivered to Ball Aerospace & Technologies Corp. in Boulder, Colo., where it was attached to the spacecraft, built by Ball. The assembled unit was then blasted by sound to simulate the effects of launch. Tests for electronic "noise" in the detectors will be performed next.
The science instrument is a 40-centimeter (16-inch) telescope with four infrared cameras. A cryostat, or cooler, uses frozen hydrogen to chill the sensitive megapixel infrared detectors down to seven Kelvin (minus 447 degrees Fahrenheit). The instrument was built by Space Dynamics Laboratory in Logan, Utah.
Among expected finds from WISE are hundreds of thousands of asteroids in our solar system's asteroid belt, and hundreds of additional asteroids that come near Earth. Many asteroids have gone undetected because they don't reflect much visible light, but their heat makes them glow in infrared light that WISE can see. By cataloguing the objects, the mission will provide better estimates of their sizes, a critical step for assessing the risk associated with those that might impact Earth.
"We know that asteroids occasionally hit Earth, and we'd like to have a better idea of how many there are and their sizes," said Amy Mainzer of NASA's Jet Propulsion Laboratory, Pasadena, Calif., the mission's deputy project scientist. "Whether they are dark or shiny, they all emit infrared light. They can't hide from WISE."
The mission is also expected to find the coldest stars -- dim orbs called brown dwarfs that are too small to have ignited like our sun. Brown dwarfs are littered throughout our galaxy, but because they are so cool, they are often too faint to see in visible light. The infrared detectors on WISE will pick up the glow of roughly 1,000 brown dwarfs in our galaxy, including those coldest and closest to our solar system. In fact, astronomers say the mission could find a brown dwarf closer to us than the nearest known star, Proxima Centauri, located approximately 4 light-years away.
"We've been learning that brown dwarfs may have planets, so it's possible we'll find the closest planetary systems," said Peter Eisenhardt, the mission's project scientist at JPL. "We should also find many hundreds of brown dwarfs colder than 480 degrees Celsius (900 degrees Fahrenheit), a group that as of now has only nine known members."
In addition, the survey will reveal the universe's most luminous galaxies seen long ago in the dusty throes of their formation, disks of planet-forming material around stars, and other cosmic goodies. The observations will guide other infrared telescopes to the most interesting objects for follow-up studies. For example, NASA's Spitzer Space Telescope, the Herschel observatory just launched by ESA with significant NASA participation, and NASA's upcoming James Webb Space Telescope will direct their gaze at objects uncovered by WISE.
WISE will lift off from Vandenberg aboard a United Launch Alliance Delta II rocket. It will orbit Earth, mapping the entire sky in six months after a one-month checkout period. Its frozen hydrogen is expected to last several months longer, allowing WISE to map much of the sky a second time and see what has changed.
JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate. The mission's principal investigator, Edward Wright, is at UCLA. The mission was developed under NASA's Explorer Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory and the spacecraft was built by Ball Aerospace & Technologies Corp. Science operations and data processing will take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.
More information is online at http://wise.ssl.berkeley.edu/mission.html.
The Infrared Astronomical Satellite, launched in 1983, was a joint mission between NASA, the United Kingdom and the Netherlands. | 0.935111 | 3.624798 |
Astronomers have discovered what they think is a brand new black hole, and if they’re right, it’s no longer that a long way far from Earth. At a mere 1,000 mild-years away, the small black hole would be our cosmic neighbor — the nearest one to our planet ever found.
Being a black hollow, the item is impossible to see directly with contraptions from Earth, as no mild escapes it. So scientists working at the European Southern Observatory (ESO) in Chile certainly inferred that that item is where they think based on the moves of stars nearby, consistent with a new examine posted in Astronomy & Astrophysics.
It’s about 1,000 mild-years away, or roughly 9.five thousand, million, million km, within the Constellation Telescopium. That might not sound very near, but on the size of the Universe, it’s certainly right next door. Scientists observed the black hole from the manner it interacts with stars – one that orbits the hollow, and the alternative that orbits this inner pair. Normally, black holes are observed from the manner they have interaction violently with an accreting disc of gas and dust. As they shred this material, copious X-rays are emitted. It’s this high-power sign that telescopes detect, no longer the black hole itself.
So this is an unusual case, in that it is the motions of the stars, together called HR 6819, that have given the game away.
“This is what you may name a ‘darkish black hollow’; it’s virtually black in that sense,” stated Dietrich Baade, emeritus astronomer on the European Southern Observatory (ESO) corporation in Garching, Germany.
The ESO says that the hidden black hollow in HR 6819 is one in every of the first actual stellar-mass black holes found that do not engage violently with their on the spot surroundings and, therefore, appear certainly black. Its presence could most effective be spotted and the calculations of the mass could most effective be performed by studying the orbit of the star inside the internal pair. “An invisible object with a mass at least 4 times that of the Sun can best be a black hollow,” says ESO scientist Thomas Rivinius, who led the study.
This isn’t the cease of it. Scientists trust that this unique black hollow discovery could certainly lead them to affirm a 2d system, already underneath observation.
“We realised that some other system, known as LB-1, might also be one of these triple, though we’d want extra observations to mention for sure,” says Marianne Heida, a postdoctoral fellow at ESO and co-author of the paper. “LB-1 is a bit similarly far from Earth but still quite close in astronomical terms, so meaning that in all likelihood many more of those structures exist.” There is notion that by locating and analyzing these capability black holes, there may be some information about what brought about the formation of the rare stars, and how they have developed since. These uncommon stars have as tons as 8 instances the mass of the Sun on the very starting and they result in a supernova explosion which leaves behind a black hole. | 0.921944 | 3.902918 |
A massive supernova spotted in an isolated part of the universe has revealed a number of odd qualities, and just might be one of the most powerful explosions ever observed.
Observations of supernova, named SN 2016iet, have forced scientists to rethink how massive stars ended their lives in the early universe. It is the most massive star astronomers have ever seen die in a supernova explosion, officials with the Harvard-Smithsonian Center for Astrophysics said in a statement.
The star, located in a distant dwarf galaxy about a billion light-years from Earth, was first spotted by the European Space Agency's (ESA) Gaia satellite in November 2016. Following three years of observations, the team of scientists concluded that the supernova started off as a star 200 times the mass of the sun and formed in an isolated area around 54,000 light-years away from the center of its host dwarf galaxy (a light-year is the distance light travels in a year, roughly 6 trillion miles or 10 trillion kilometers).
"When we first realized how thoroughly unusual SN 2016iet is, my reaction was, 'Whoa – did something go horribly wrong with our data?'" Sebastian Gomez, Harvard University graduate student and lead author of the paper, said in the statement.
The star lost around 85% of its mass during its short-lived existence of only a few million years before it exploded, and the material it shed before its death collided with the debris from the explosion, which led to the supernova's unusual qualities.
"Everything about this supernova looks different, its change in brightness with time, its spectrum, the galaxy it is located in, and even where it's located within its galaxy," Edo Berger, astronomy professor at Harvard University and co-author of the study, said in the statement. "We sometimes see supernovas that are unusual in one respect but otherwise are normal; this one is unique in every possible way."
The supernova also had an unusually long duration, an odd chemical fingerprint and a lack of heavy metals in its environment — all qualities that have not been observed in any other supernova before it.
SN 2016iet marked the first observation of a pair-instability supernova that astronomers were able to observe. A pair-instability supernova occurs when the collapsing core of a dying star produces gamma-ray radiation that leads to the production of particle and antiparticle pairs, and those pairs cause a thermonuclear explosion that annihilates the star.
"The idea of pair-instability supernovas has been around for decades," Berger said. "But finally having the first observational example that puts a dying star in the right regime of mass, with the right behavior, and in a metal-poor dwarf galaxy is an incredible step forward."
The findings were published Aug. 15 in the Astrophysical Journal.
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- Huge Supernova Explosion Leaves Surprisingly Dusty Aftermath | 0.810747 | 4.013621 |
Thales of Miletus
|Died||c. 548/545 BC (aged c. 78)|
Thales of Miletus ( // THAY-leez; Greek : Θαλῆς (ὁ Μιλήσιος), Thalēs; c. 624/623 – c. 548/545 BC) was a Greek mathematician, astronomer and pre-Socratic philosopher from Miletus in Ionia, Asia Minor. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded him as the first philosopher in the Greek tradition, and he is otherwise historically recognized as the first individual in Western civilization known to have entertained and engaged in scientific philosophy.
Thales is recognized for breaking from the use of mythology to explain the world and the universe, and instead explaining natural objects and phenomena by naturalistic theories and hypotheses, in a precursor to modern science. Almost all the other pre-Socratic philosophers followed him in explaining nature as deriving from a unity of everything based on the existence of a single ultimate substance, instead of using mythological explanations. Aristotle regarded him as the founder of the Ionian School and reported Thales' hypothesis that the originating principle of nature and the nature of matter was a single material substance: water.
In mathematics, Thales used geometry to calculate the heights of pyramids and the distance of ships from the shore. He is the first known individual to use deductive reasoning applied to geometry, by deriving four corollaries to Thales' theorem. He is the first known individual to whom a mathematical discovery has been attributed.
The dates of Thales' life are not exactly known, but are roughly established by a few datable events mentioned in the sources. According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Diogenes Laërtius quotes the chronicle of Apollodorus of Athens as saying that Thales died at the age of 78 during the 58th Olympiad (548–545 BC) and attributes his death to heat stroke while watching the games.
Thales was probably born in the city of Miletus around the mid-620s BC. The ancient writer Apollodorus of Athenswriting during the 2nd century BC, thought Thales was born about the year 625 BC. Herodotus, writing in the fifth century BC, described Thales as "a Phoenician by remote descent". Tim Whitmarsh noted that Thales regarded water as the primal matter, and because thal is the Phoenician word for moisture, his name may have derived from this circumstance."
According to the later historian Diogenes Laërtius, in his third century AD Lives of the Philosophers , references Herodotus, Duris, and Democritus, who all agree "that Thales was the son of Examyas and Cleobulina, and belonged to the Thelidae who are Phoenicians."Their names are indigenous Carian and Greek, respectively. Diogenes then states that "Most writers, however, represent him as a native of Miletus and of a distinguished family." However, his supposed mother Cleobulina has also been described as his companion. Diogenes then delivers more conflicting reports: one that Thales married and either fathered a son (Cybisthus or Cybisthon) or adopted his nephew of the same name; the second that he never married, telling his mother as a young man that it was too early to marry, and as an older man that it was too late. Plutarch had earlier told this version: Solon visited Thales and asked him why he remained single; Thales answered that he did not like the idea of having to worry about children. Nevertheless, several years later, anxious for family, he adopted his nephew Cybisthus.
It has been claimed that he was roughly the professional equivalent of a contemporary option trader.
It is assumed that Thales at one point in his life visited Egypt, where he learned about geometry.Diogenes Laërtius wrote that Thales identifies the Milesians as Athenian colonists.
Thales (who died around 30 years before the time of Pythagoras and 300 years before Euclid, Eudoxus of Cnidus, and Eudemus of Rhodes) is often hailed as "the first Greek mathematician". While some historians, such as Colin R. Fletcher, point out that there could have been a predecessor to Thales who would have been named in Eudemus' lost book History of Geometry, it is admitted that without the work "the question becomes mere speculation." Fletcher holds that as there is no viable predecessor to the title of first Greek mathematician, the only question is whether Thales qualifies as a practitioner in that field; he holds that "Thales had at his command the techniques of observation, experimentation, superposition and deduction…he has proved himself mathematician."
Aristotle wrote in Metaphysics, "Thales, the founder of this school of philosophy, says the permanent entity is water (which is why he also propounded that the earth floats on water). Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption from this; and also from the fact that the seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things."
Thales involved himself in many activities, including engineering. [ clarification needed ]Some say that he left no writings. Others say that he wrote On the Solstice and On the Equinox . The Nautical Star-guide has been attributed to him, but this was disputed in ancient times. No writing attributed to him has survived. Diogenes Laërtius quotes two letters from Thales: one to Pherecydes of Syros, offering to review his book on religion, and one to Solon, offering to keep him company on his sojourn from Athens.
A story, with different versions, recounts how Thales achieved riches from an olive harvest by prediction of the weather. In one version, he bought all the olive presses in Miletus after predicting the weather and a good harvest for a particular year. Another version of the story has Aristotle explain that Thales had reserved presses in advance, at a discount, and could rent them out at a high price when demand peaked, following his prediction of a particularly good harvest. This first version of the story would constitute the first historically known creation and use of futures, whereas the second version would be the first historically known creation and use of options.
Aristotle explains that Thales' objective in doing this was not to enrich himself but to prove to his fellow Milesians that philosophy could be useful, contrary to what they thought,or alternatively, Thales had made his foray into enterprise because of a personal challenge put to him by an individual who had asked why, if Thales was an intelligent famous philosopher, he had yet to attain wealth.
Diogenes Laërtius tells us that Thales gained fame as a counselor when he advised the Milesians not to engage in a symmachia, a "fighting together", with the Lydians. This has sometimes been interpreted as an alliance. [ failed verification ] Another story by Herodotus is that Croesus sent his army to the Persian territory. He was stopped by the river Halys, then unbridged. Thales then got the army across the river by digging a diversion upstream so as to reduce the flow, making it possible to cross the river. While Herodotus reported that most of his fellow Greeks believe that Thales did divert the river Halys to assist King Croesus' military endeavors, he himself finds it doubtful.
Croesus was defeated before the city of Sardis by Cyrus, who subsequently spared Miletus because it had taken no action. Cyrus was so impressed by Croesus’ wisdom and his connection with the sages that he spared him and took his advice on various matters.[ citation needed ] The Ionian cities should be demoi, or "districts".
He counselled them to establish a single seat of government, and pointed out Teos as the fittest place for it; "for that," he said, "was the centre of Ionia. Their other cities might still continue to enjoy their own laws, just as if they were independent states."
Miletus, however, received favorable terms from Cyrus. The others remained in an Ionian League of twelve cities (excluding Miletus), and were subjugated by the Persians.[ citation needed ]
According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Thales also described the position of Ursa Minor, and he thought the constellation might be useful as a guide for navigation at sea. He calculated the duration of the year and the timings of the equinoxes and solstices. He is additionally attributed with the first observation of the Hyades and with calculating the position of the Pleiades. Plutarch indicates that in his day (c. AD 100) there was an extant work, the Astronomy, composed in verse and attributed to Thales.
Herodotus writes that in the sixth year of the war, the Lydians under King Alyattes and the Medes under Cyaxares were engaged in an indecisive battle when suddenly day turned into night, leading to both parties halting the fighting and negotiating a peace agreement. Herodotus also mentions that the loss of daylight had been predicted by Thales. He does not, however, mention the location of the battle.
Afterwards, on the refusal of Alyattes to give up his suppliants when Cyaxares sent to demand them of him, war broke out between the Lydians and the Medes, and continued for five years, with various success. In the course of it the Medes gained many victories over the Lydians, and the Lydians also gained many victories over the Medes. Among their other battles there was one night engagement. As, however, the balance had not inclined in favour of either nation, another combat took place in the sixth year, in the course of which, just as the battle was growing warm, day was on a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it actually took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on.
However, based on the list of Medean kings and the duration of their reign reported elsewhere by Herodotus, Cyaxares died 10 years before the eclipse.
Diogenes Laërtius BC and that Thales was the first sage. The same story, however, asserts that Thales emigrated to Miletus. There is also a report that he did not become a student of nature until after his political career. Much as we would like to have a date on the seven sages, we must reject these stories and the tempting date if we are to believe that Thales was a native of Miletus, predicted the eclipse, and was with Croesus in the campaign against Cyrus.tells us that the Seven Sages were created in the archonship of Damasius at Athens about 582
Thales received instruction from an Egyptian priest.[ citation needed ] It was fairly certain that he came from a wealthy, established family, in a class which customarily provided higher education for their children.[ citation needed ] Moreover, the ordinary citizen, unless he was a seafaring man or a merchant, could not afford the grand tour in Egypt, and did not consort with noble lawmakers such as Solon.[ citation needed ]
In Diogenes Laërtius' Lives of Eminent Philosophers Chapter 1.39, Laërtius relates the several stories of an expensive object that is to go to the most wise. In one version (that Laërtius credits to Callimachus in his Iambics) Bathycles of Arcadia states in his will that an expensive bowl "'should be given to him who had done most good by his wisdom.' So it was given to Thales, went the round of all the sages, and came back to Thales again. And he sent it to Apollo at Didyma, with this dedication...'Thales the Milesian, son of Examyas [dedicates this] to Delphinian Apollo after twice winning the prize from all the Greeks.'"
Early Greeks, and other civilizations before them, often invoked idiosyncratic explanations of natural phenomena with reference to the will of anthropomorphic gods and heroes. Instead, Thales aimed to explain natural phenomena via rational hypotheses that referenced natural processes themselves. For example, rather than assuming that earthquakes were the result of supernatural whims, Thales explained them by hypothesizing that the Earth floats on water and that earthquakes occur when the Earth is rocked by waves.
Thales was a hylozoist (one who thinks that matter is alive,i.e. containing soul(s)). Aristotle wrote ( De Anima 411 a7-8) of Thales: ...Thales thought all things are full of gods. Aristotle posits the origin of Thales thought on matter generally containing souls, to Thales thinking initially on the fact of, because magnets move iron, the presence of movement of matter indicated this matter contained life.
Thales, according to Aristotle, asked what was the nature (Greek arche ) of the object so that it would behave in its characteristic way. Physis (φύσις) comes from phyein (φύειν), "to grow", related to our word "be". (G)natura is the way a thing is "born", again with the stamp of what it is in itself.
Aristotle characterizes most of the philosophers "at first" (πρῶτον) as thinking that the "principles in the form of matter were the only principles of all things", where "principle" is arche, "matter" is hyle ("wood" or "matter", "material") and "form" is eidos.
Arche is translated as "principle", but the two words do not have precisely the same meaning. A principle of something is merely prior (related to pro-) to it either chronologically or logically. An arche (from ἄρχειν, "to rule") dominates an object in some way. If the arche is taken to be an origin, then specific causality is implied; that is, B is supposed to be characteristically B just because it comes from A, which dominates it.
The archai that Aristotle had in mind in his well-known passage on the first Greek scientists are not necessarily chronologically prior to their objects, but are constituents of it. For example, in pluralism objects are composed of earth, air, fire and water, but those elements do not disappear with the production of the object. They remain as archai within it, as do the atoms of the atomists.
What Aristotle is really saying is that the first philosophers were trying to define the substance(s) of which all material objects are composed. As a matter of fact, that is exactly what modern scientists are attempting to accomplish in nuclear physics, which is a second reason why Thales is described as the first western scientist,[ citation needed ] but some contemporary scholars reject this interpretation.
Thales was known for his innovative use of geometry. His understanding was theoretical as well as practical. For example, he said:
Megiston topos: apanta gar chorei (Μέγιστον τόπος· ἄπαντα γὰρ χωρεῖ.)
The greatest is space, for it holds all things.
Topos is in Newtonian-style space, since the verb, chorei, has the connotation of yielding before things, or spreading out to make room for them, which is extension. Within this extension, things have a position. Points, lines, planes and solids related by distances and angles follow from this presumption.
Thales understood similar triangles and right triangles, and what is more, used that knowledge in practical ways. The story is told in Diogenes Laërtius (loc. cit.) that he measured the height of the pyramids by their shadows at the moment when his own shadow was equal to his height. A right triangle with two equal legs is a 45-degree right triangle, all of which are similar. The length of the pyramid's shadow measured from the center of the pyramid at that moment must have been equal to its height.
This story indicates that he was familiar with the Egyptian seked , or seqed, the ratio of the run to the rise of a slope (cotangent).[ citation needed ] The seked is at the base of problems 56, 57, 58, 59 and 60 of the Rhind papyrus — an ancient Egyptian mathematical document.
More practically Thales used the same method to measure the distances of ships at sea, said Eudemus as reported by Proclus ("in Euclidem"). According to Kirk & Raven (reference cited below), all you need for this feat is three straight sticks pinned at one end and knowledge of your altitude. One stick goes vertically into the ground. A second is made level. With the third you sight the ship and calculate the seked from the height of the stick and its distance from the point of insertion to the line of sight (Proclus, In Euclidem, 352).
There are two theorems of Thales in elementary geometry, one known as Thales' theorem having to do with a triangle inscribed in a circle and having the circle's diameter as one leg, the other theorem being also called the intercept theorem. In addition Eudemus attributed to him the discovery that a circle is bisected by its diameter, that the base angles of an isosceles triangle are equal and that vertical angles are equal. According to a historical Note,when Thales visited Egypt, he observed that whenever the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal. Thales concluded that one could prove that all vertical angles are equal if one accepted some general notions such as: all straight angles are equal, equals added to equals are equal, and equals subtracted from equals are equal.
The evidence for the primacy of Thales comes to us from a book by Proclus who wrote a thousand years after Thales but is believed to have had a copy of Eudemus' book. Proclus wrote "Thales was the first to go to Egypt and bring back to Greece this study."He goes on to tell us that in addition to applying the knowledge he gained in Egypt "He himself discovered many propositions and disclosed the underlying principles of many others to his successors, in some case his method being more general, in others more empirical."
Other quotes from Proclus list more of Thales' mathematical achievements:
They say that Thales was the first to demonstrate that the circle is bisected by the diameter, the cause of the bisection being the unimpeded passage of the straight line through the centre.
[Thales] is said to have been the first to have known and to have enunciated [the theorem] that the angles at the base of any isosceles triangle are equal, though in the more archaic manner he described the equal angles as similar.
This theorem, that when two straight lines cut one another, the vertical and opposite angles are equal, was first discovered, as Eudemus says, by Thales, though the scientific demonstration was improved by the writer of Elements.
Eudemus in his History of Geometry attributes this theorem [the equality of triangles having two angles and one side equal] to Thales. For he says that the method by which Thales showed how to find the distance of ships at sea necessarily involves this method.
Pamphila says that, having learnt geometry from the Egyptians, he [Thales] was the first to inscribe in a circle a right-angled triangle, whereupon he sacrificed an ox.
In addition to Proclus, Hieronymus of Rhodes also cites Thales as the first Greek mathematician. Hieronymus held that Thales was able to measure the height of the pyramids by using a theorem of geometry now known as the intercept theorem, (after gathering data by using his walking-stick and comparing its shadow to those cast by the pyramids). We receive variations of Hieronymus' story through Diogenes Laërtius,Pliny the Elder, and Plutarch. According to Hieronymus, historically quoted by Diogenes Laërtius, Thales found the height of pyramids by comparison between the lengths of the shadows cast by a person and by the pyramids.
Due to the variations among testimonies, such as the "story of the sacrifice of an ox on the occasion of the discovery that the angle on a diameter of a circle is a right angle" in the version told by Diogenes Laërtius being accredited to Pythagoras rather than Thales, some historians (such as D. R. Dicks) question whether such anecdotes have any historical worth whatsoever.
Thales' most famous philosophical position was his cosmological thesis, which comes down to us through a passage from Aristotle's Metaphysics .In the work Aristotle unequivocally reported Thales' hypothesis about the nature of all matter – that the originating principle of nature was a single material substance: water. Aristotle then proceeded to proffer a number of conjectures based on his own observations to lend some credence to why Thales may have advanced this idea (though Aristotle did not hold it himself).
Aristotle laid out his own thinking about matter and form which may shed some light on the ideas of Thales, in Metaphysics 983 b6 8–11, 17–21. (The passage contains words that were later adopted by science with quite different meanings.)
That from which is everything that exists and from which it first becomes and into which it is rendered at last, its substance remaining under it, but transforming in qualities, that they say is the element and principle of things that are. …For it is necessary that there be some nature (φύσις), either one or more than one, from which become the other things of the object being saved... Thales the founder of this type of philosophy says that it is water.
In this quote we see Aristotle's depiction of the problem of change and the definition of substance. He asked if an object changes, is it the same or different? In either case how can there be a change from one to the other? The answer is that the substance "is saved", but acquires or loses different qualities (πάθη, the things you "experience").
Aristotle conjectured that Thales reached his conclusion by contemplating that the "nourishment of all things is moist and that even the hot is created from the wet and lives by it." While Aristotle's conjecture on why Thales held water as the originating principle of matter is his own thinking, his statement that Thales held it as water is generally accepted as genuinely originating with Thales and he is seen as an incipient matter-and-formist.[ citation needed ]
Thales thought the Earth must be a flat disk which is floating in an expanse of water.
Heraclitus Homericus states that Thales drew his conclusion from seeing moist substance turn into air, slime and earth. It seems likely that Thales viewed the Earth as solidifying from the water on which it floated and the oceans that surround it.
Writing centuries later, Diogenes Laërtius also states that Thales taught "Water constituted (ὑπεστήσατο, 'stood under') the principle of all things."
Aristotle considered Thales’ position to be roughly the equivalent to the later ideas of Anaximenes, who held that everything was composed of air.The 1870 book Dictionary of Greek and Roman Biography and Mythology noted:
In his dogma that water is the origin of things, that is, that it is that out of which every thing arises, and into which every thing resolves itself, Thales may have followed Orphic cosmogonies, while, unlike them, he sought to establish the truth of the assertion. Hence, Aristotle, immediately after he has called him the originator of philosophy brings forward the reasons which Thales was believed to have adduced in confirmation of that assertion; for that no written development of it, or indeed any book by Thales, was extant, is proved by the expressions which Aristotle uses when he brings forward the doctrines and proofs of the Milesian. (p. 1016)
According to Aristotle, Thales thought lodestones had souls, because iron is attracted to them (by the force of magnetism).
Aristotle defined the soul as the principle of life, that which imbues the matter and makes it live, giving it the animation, or power to act. The idea did not originate with him, as the Greeks in general believed in the distinction between mind and matter, which was ultimately to lead to a distinction not only between body and soul but also between matter and energy.[ citation needed ] If things were alive, they must have souls. This belief was no innovation, as the ordinary ancient populations of the Mediterranean did believe that natural actions were caused by divinities. Accordingly, Aristotle and other ancient writers state that Thales believed that "all things were full of gods." In their zeal to make him the first in everything some said he was the first to hold the belief, which must have been widely known to be false.[ citation needed ] However, Thales was looking for something more general, a universal substance of mind.[ citation needed ] That also was in the polytheism of the times. Zeus was the very personification of supreme mind, dominating all the subordinate manifestations. From Thales on, however, philosophers had a tendency to depersonify or objectify mind, as though it were the substance of animation per se and not actually a god like the other gods. The end result was a total removal of mind from substance, opening the door to a non-divine principle of action.[ citation needed ]
Classical thought, however, had proceeded only a little way along that path. Instead of referring to the person, Zeus, they talked about the great mind:
"Thales", says Cicero,"assures that water is the principle of all things; and that God is that Mind which shaped and created all things from water."
The universal mind appears as a Roman belief in Virgil as well:
According to Henry Fielding (1775), Diogenes Laërtius (1.35) affirmed that Thales posed "the independent pre-existence of God from all eternity, stating "that God was the oldest of all beings, for he existed without a previous cause even in the way of generation; that the world was the most beautiful of all things; for it was created by God."
Due to the scarcity of sources concerning Thales and the discrepancies between the accounts given in the sources that have survived, there is a scholarly debate over possible influences on Thales and the Greek mathematicians that came after him. Historian Roger L. Cooke points out that Proclus does not make any mention of Mesopotamian influence on Thales or Greek geometry, but "is shown clearly in Greek astronomy, in the use of sexagesimal system of measuring angles and in Ptolemy's explicit use of Mesopotamian astronomical observations."Cooke notes that it may possibly also appear in the second book of Euclid's Elements, "which contains geometric constructions equivalent to certain algebraic relations that are frequently encountered in the cuneiform tablets." Cooke notes "This relation however, is controversial."
Historian B.L. Van der Waerden is among those advocating the idea of Mesopotamian influence, writing "It follows that we have to abandon the traditional belief that the oldest Greek mathematicians discovered geometry entirely by themselves…a belief that was tenable only as long as nothing was known about Babylonian mathematics. This in no way diminishes the stature of Thales; on the contrary, his genius receives only now the honour that is due to it, the honour of having developed a logical structure for geometry, of having introduced proof into geometry."
Some historians, such as D. R. Dicks takes issue with the idea that we can determine from the questionable sources we have, just how influenced Thales was by Babylonian sources. He points out that while Thales is held to have been able to calculate an eclipse using a cycle called the "Saros" held to have been "borrowed from the Babylonians", "The Babylonians, however, did not use cycles to predict solar eclipses, but computed them from observations of the latitude of the moon made shortly before the expected syzygy." B.C., as one can see from the very unsatisfactory situation 400 years later; nor did the Babylonians ever develop any theory which took the influence of geographical latitude into account." Dicks examines the cycle referred to as 'Saros' – which Thales is held to have used and which is believed to stem from the Babylonians. He points out that Ptolemy makes use of this and another cycle in his book Mathematical Syntaxis but attributes it to Greek astronomers earlier than Hipparchus and not to Babylonians. Dicks notes Herodotus does relate that Thales made use of a cycle to predict the eclipse, but maintains that "if so, the fulfillment of the 'prediction' was a stroke of pure luck not science". He goes further joining with other historians (F. Martini, J.L. E. Dreyer, O. Neugebauer) in rejecting the historicity of the eclipse story altogether. Dicks links the story of Thales discovering the cause for a solar eclipse with Herodotus' claim that Thales discovered the cycle of the sun with relation to the solstices, and concludes "he could not possibly have possessed this knowledge which neither the Egyptians nor the Babylonians nor his immediate successors possessed." Josephus is the only ancient historian that claims Thales visited Babylonia.Dicks cites historian O. Neugebauer who relates that "No Babylonian theory for predicting solar eclipse existed at 600
Herodotus wrote that the Greeks learnt the practice of dividing the day into 12 parts, about the polos, and the gnomon from the Babylonians. (The exact meaning of his use of the word polos is unknown, current theories include: "the heavenly dome", "the tip of the axis of the celestial sphere", or a spherical concave sundial.) Yet even Herodotus' claims on Babylonian influence are contested by some modern historians, such as L. Zhmud, who points out that the division of the day into twelve parts (and by analogy the year) was known to the Egyptians already in the second millennium, the gnomon was known to both Egyptians and Babylonians, and the idea of the "heavenly sphere" was not used outside of Greece at this time.
Less controversial than the position that Thales learnt Babylonian mathematics is the claim he was influenced by Egyptians. Pointedly historian S. N. Bychkov holds that the idea that the base angles of an isosceles triangle are equal likely came from Egypt. This is because, when building a roof for a home – having a cross section be exactly an isosceles triangle isn't crucial (as it's the ridge of the roof that must fit precisely), in contrast a symmetric square pyramid cannot have errors in the base angles of the faces or they will not fit together tightly.Historian D.R. Dicks agrees that compared to the Greeks in the era of Thales, there was a more advanced state of mathematics among the Babylonians and especially the Egyptians – "both cultures knew the correct formulae for determining the areas and volumes of simple geometrical figures such as triangles, rectangles, trapezoids, etc.; the Egyptians could also calculate correctly the volume of the frustum of a pyramid with a square base (the Babylonians used an incorrect formula for this), and used a formula for the area of a circle...which gives a value for π of 3.1605—a good approximation." Dicks also agrees that this would have had an effect on Thales (whom the most ancient sources agree was interested in mathematics and astronomy) but he holds that tales of Thales' travels in these lands are pure myth.
The ancient civilization and massive monuments of Egypt had "a profound and ineradicable impression on the Greeks". They attributed to Egyptians "an immemorial knowledge of certain subjects" (including geometry) and would claim Egyptian origin for some of their own ideas to try and lend them "a respectable antiquity" (such as the "Hermetic" literature of the Alexandrian period).
Dicks holds that since Thales was a prominent figure in Greek history by the time of Eudemus but "nothing certain was known except that he lived in Miletus".A tradition developed that as "Milesians were in a position to be able to travel widely" Thales must have gone to Egypt. As Herodotus says Egypt was the birthplace of geometry he must have learnt that while there. Since he had to have been there, surely one of the theories on Nile Flooding laid out by Herodotus must have come from Thales. Likewise as he must have been in Egypt he had to have done something with the Pyramids – thus the tale of measuring them. Similar apocryphal stories exist of Pythagoras and Plato traveling to Egypt with no corroborating evidence.
As the Egyptian and Babylonian geometry at the time was "essentially arithmetical", they used actual numbers and "the procedure is then described with explicit instructions as to what to do with these numbers" there was no mention of how the rules of procedure were made, and nothing toward a logically arranged corpus of generalized geometrical knowledge with analytical 'proofs' such as we find in the words of Euclid, Archimedes, and Apollonius."So even had Thales traveled there he could not have learnt anything about the theorems he is held to have picked up there (especially because there is no evidence that any Greeks of this age could use Egyptian hieroglyphics).
Likewise until around the second century BC and the time of Hipparchus (c. 190–120 BC) the Babylonian general division of the circle into 360 degrees and their sexagesimal system was unknown. Herodotus says almost nothing about Babylonian literature and science, and very little about their history. Some historians, like P. Schnabel, hold that the Greeks only learned more about Babylonian culture from Berossus, a Babylonian priest who is said to have set up a school in Cos around 270 BC (but to what extent this had in the field of geometry is contested).
Dicks points out that the primitive state of Greek mathematics and astronomical ideas exhibited by the peculiar notions of Thales' successors (such as Anaximander, Anaximenes, Xenophanes, and Heraclitus), which historian J. L. Heiberg calls "a mixture of brilliant intuition and childlike analogies",argues against the assertions from writers in late antiquity that Thales discovered and taught advanced concepts in these fields.
John Burnet (1892) noted
Lastly, we have one admitted instance of a philosophic guild, that of the Pythagoreans. And it will be found that the hypothesis, if it is to be called by that name, of a regular organisation of scientific activity will alone explain all the facts. The development of doctrine in the hands of Thales, Anaximander, and Anaximenes, for instance, can only be understood as the elaboration of a single idea in a school with a continuous tradition.
In the long sojourn of philosophy, there has existed hardly a philosopher or historian of philosophy who did not mention Thales and try to characterize him in some way. He is generally recognized as having brought something new to human thought. Mathematics, astronomy, and medicine already existed. Thales added something to these different collections of knowledge to produce a universality, which, as far as writing tells us, was not in tradition before, but resulted in a new field.
Ever since, interested persons have been asking what that new something is. Answers fall into (at least) two categories, the theory and the method. Once an answer has been arrived at, the next logical step is to ask how Thales compares to other philosophers, which leads to his classification (rightly or wrongly).
The most natural epithets of Thales are "materialist" and "naturalist", which are based on ousia and physis. The Catholic Encyclopedia notes that Aristotle called him a physiologist, with the meaning "student of nature."On the other hand, he would have qualified as an early physicist, as did Aristotle. They studied corpora, "bodies", the medieval descendants of substances.
Most agree that Thales' stamp on thought is the unity of substance, hence Bertrand Russell:
The view that all matter is one is quite a reputable scientific hypothesis. ...But it is still a handsome feat to have discovered that a substance remains the same in different states of aggregation.
Russell was only reflecting an established tradition; for example: Nietzsche, in his Philosophy in the Tragic Age of the Greeks , wrote:
Greek philosophy seems to begin with an absurd notion, with the proposition that water is the primal origin and the womb of all things. Is it really necessary for us to take serious notice of this proposition? It is, and for three reasons. First, because it tells us something about the primal origin of all things; second, because it does so in language devoid of image or fable, and finally, because contained in it, if only embryonically, is the thought, "all things are one."
This sort of materialism, however, should not be confused with deterministic materialism. Thales was only trying to explain the unity observed in the free play of the qualities. The arrival of uncertainty in the modern world made possible a return to Thales; for example, John Elof Boodin writes ("God and Creation"):
We cannot read the universe from the past...
Boodin defines an "emergent" materialism, in which the objects of sense emerge uncertainly from the substrate. Thales is the innovator of this sort of materialism.
Later scholastic thinkers would maintain that in his choice of water Thales was influenced by Babylonian or Chaldean religion, that held that a god had begun creation by acting upon the pre-existing water. Historian Abraham Feldman holds this does not stand up under closer examination. In Babylonian religion the water is lifeless and sterile until a god acts upon it, but for Thales water itself was divine and creative. He maintained that "All things are full of gods", and to understand the nature of things was to discover the secrets of the deities, and through this knowledge open the possibility that one could be greater than the grandest Olympian.
Feldman points out that while other thinkers recognized the wetness of the world "none of them was inspired to conclude that everything was ultimately aquatic."He further points out that Thales was "a wealthy citizen of the fabulously rich Oriental port of Miletus...a dealer in the staples of antiquity, wine and oil...He certainly handled the shell-fish of the Phoenicians that secreted the dye of imperial purple." Feldman recalls the stories of Thales measuring the distance of boats in the harbor, creating mechanical improvements for ship navigation, giving an explanation for the flooding of the Nile (vital to Egyptian agriculture and Greek trade), and changing the course of the river Halys so an army could ford it. Rather than seeing water as a barrier Thales contemplated the Ionian yearly religious gathering for athletic ritual (held on the promontory of Mycale and believed to be ordained by the ancestral kindred of Poseidon, the god of the sea). He called for the Ionian mercantile states participating in this ritual to convert it into a democratic federation under the protection of Poseidon that would hold off the forces of pastoral Persia. Feldman concludes that Thales saw "that water was a revolutionary leveler and the elemental factor determining the subsistence and business of the world" and "the common channel of states."
Feldman considers Thales' environment and holds that Thales would have seen tears, sweat, and blood as granting value to a person's work and the means how life giving commodities travelled (whether on bodies of water or through the sweat of slaves and pack-animals). He would have seen that minerals could be processed from water such as life-sustaining salt and gold taken from rivers. He would’ve seen fish and other food stuffs gathered from it. Feldman points out that Thales held that the lodestone was alive as it drew metals to itself. He holds that Thales "living ever in sight of his beloved sea" would see water seem to draw all "traffic in wine and oil, milk and honey, juices and dyes" to itself, leading him to "a vision of the universe melting into a single substance that was valueless in itself and still the source of wealth."Feldman concludes that for Thales "...water united all things. The social significance of water in the time of Thales induced him to discern through hardware and dry-goods, through soil and sperm, blood, sweat and tears, one fundamental fluid stuff...water, the most commonplace and powerful material known to him." This combined with his contemporary's idea of "spontaneous generation" allow us to see how Thales could hold that water could be divine and creative.
Feldman points to the lasting association of the theory that "all whatness is wetness" with Thales himself, pointing out that Diogenes Laërtius speaks of a poem, probably a satire, where Thales is snatched to heaven by the sun.
In the West, Thales represents a new kind of inquiring community as well. Edmund Husserlattempts to capture the new movement as follows. Philosophical man is a "new cultural configuration" based in stepping back from "pregiven tradition" and taking up a rational "inquiry into what is true in itself;" that is, an ideal of truth. It begins with isolated individuals such as Thales, but they are supported and cooperated with as time goes on. Finally the ideal transforms the norms of society, leaping across national borders.
The term "Pre-Socratic" derives ultimately from the philosopher Aristotle, who distinguished the early philosophers as concerning themselves with substance.
Diogenes Laërtius on the other hand took a strictly geographic and ethnic approach. Philosophers were either Ionian or Italian. He used "Ionian" in a broader sense, including also the Athenian academics, who were not Pre-Socratics. From a philosophic point of view, any grouping at all would have been just as effective. There is no basis for an Ionian or Italian unity. Some scholars, however, concede to Diogenes' scheme as far as referring to an "Ionian" school. There was no such school in any sense.
The most popular approach refers to a Milesian school, which is more justifiable socially and philosophically. They sought for the substance of phenomena and may have studied with each other. Some ancient writers qualify them as Milesioi, "of Miletus."
Thales had a profound influence on other Greek thinkers and therefore on Western history. Some believe Anaximander was a pupil of Thales. Early sources report that one of Anaximander's more famous pupils, Pythagoras, visited Thales as a young man, and that Thales advised him to travel to Egypt to further his philosophical and mathematical studies.
Many philosophers followed Thales' lead in searching for explanations in nature rather than in the supernatural; others returned to supernatural explanations, but couched them in the language of philosophy rather than of myth or of religion.
Looking specifically at Thales' influence during the pre-Socratic era, it is clear that he stood out as one of the first thinkers who thought more in the way of logos than mythos . The difference between these two more profound ways of seeing the world is that mythos is concentrated around the stories of holy origin, while logos is concentrated around the argumentation. When the mythical man wants to explain the world the way he sees it, he explains it based on gods and powers. Mythical thought does not differentiate between things and persons[ citation needed ] and furthermore it does not differentiate between nature and culture[ citation needed ]. The way a logos thinker would present a world view is radically different from the way of the mythical thinker. In its concrete form, logos is a way of thinking not only about individualism[ clarification needed ], but also the abstract[ clarification needed ]. Furthermore, it focuses on sensible and continuous argumentation. This lays the foundation of philosophy and its way of explaining the world in terms of abstract argumentation, and not in the way of gods and mythical stories[ citation needed ].
Because of Thales' elevated status in Greek culture an intense interest and admiration followed his reputation. Due to this following, the oral stories about his life were open to amplification and historical fabrication, even before they were written down generations later. Most modern dissension comes from trying to interpret what we know, in particular, distinguishing legend from fact.
Historian D.R. Dicks and other historians divide the ancient sources about Thales into those before 320 BC and those after that year (some such as Proclus writing in the 5th century C.E. and Simplicius of Cilicia in the 6th century C.E. writing nearly a millennium after his era). The first category includes Herodotus, Plato, Aristotle, Aristophanes, and Theophrastus among others. The second category includes Plautus, Aetius, Eusebius, Plutarch, Josephus, Iamblichus, Diogenes Laërtius, Theon of Smyrna, Apuleius, Clement of Alexandria, Pliny the Elder, and John Tzetzes among others.
The earliest sources on Thales (living before 320 BC) are often the same for the other Milesian philosophers (Anaximander, and Anaximenes). These sources were either roughly contemporaneous (such as Herodotus) or lived within a few hundred years of his passing. Moreover, they were writing from an oral tradition that was widespread and well known in the Greece of their day.
The latter sources on Thales are several "ascriptions of commentators and compilers who lived anything from 700 to 1,000 years after his death" which include "anecdotes of varying degrees of plausibility" and in the opinion of some historians (such as D. R. Dicks) of "no historical worth whatsoever". Dicks points out that there is no agreement "among the 'authorities' even on the most fundamental facts of his life—e.g. whether he was a Milesian or a Phoenician, whether he left any writings or not, whether he was married or single-much less on the actual ideas and achievements with which he is credited."
Contrasting the work of the more ancient writers with those of the later, Dicks points out that in the works of the early writers Thales and the other men who would be hailed as "the Seven Sages of Greece" had a different reputation than that which would be assigned to them by later authors. Closer to their own era, Thales, Solon, Bias of Priene, Pittacus of Mytilene and others were hailed as "essentially practical men who played leading roles in the affairs of their respective states, and were far better known to the earlier Greeks as lawgivers and statesmen than as profound thinkers and philosophers."For example, Plato praises him (coupled with Anacharsis) for being the originator of the potter's wheel and the anchor.
Only in the writings of the second group of writers (working after 320 BC) do "we obtain the picture of Thales as the pioneer in Greek scientific thinking, particularly in regard to mathematics and astronomy which he is supposed to have learnt about in Babylonia and Egypt." Rather than "the earlier tradition [where] he is a favourite example of the intelligent man who possesses some technical 'know how'...the later doxographers [such as Dicaearchus in the latter half of the fourth century BC] foist on to him any number of discoveries and achievements, in order to build him up as a figure of superhuman wisdom."
Dicks points out a further problem arises in the surviving information on Thales, for rather than using ancient sources closer to the era of Thales, the authors in later antiquity ("epitomators, excerptors, and compilers") actually "preferred to use one or more intermediaries, so that what we actually read in them comes to us not even at second, but at third or fourth or fifth hand. ...Obviously this use of intermediate sources, copied and recopied from century to century, with each writer adding additional pieces of information of greater or less plausibility from his own knowledge, provided a fertile field for errors in transmission, wrong ascriptions, and fictitious attributions". Dicks points out that "certain doctrines that later commentators invented for Thales...were then accepted into the biographical tradition" being copied by subsequent writers who were then cited by those coming after them "and thus, because they may be repeated by different authors relying on different sources, may produce an illusory impression of genuineness."
Doubts even exist when considering the philosophical positions held to originate in Thales "in reality these stem directly from Aristotle's own interpretations which then became incorporated in the doxographical tradition as erroneous ascriptions to Thales".(The same treatment was given by Aristotle to Anaxagoras.)
Most philosophic analyses of the philosophy of Thales come from Aristotle, a professional philosopher, tutor of Alexander the Great, who wrote 200 years after Thales' death. Aristotle, judging from his surviving books, does not seem to have access to any works by Thales, although he probably had access to works of other authors about Thales, such as Herodotus, Hecataeus, Plato etc., as well as others whose work is now extinct. It was Aristotle's express goal to present Thales' work not because it was significant in itself, but as a prelude to his own work in natural philosophy. Geoffrey Kirk and John Raven, English compilers of the fragments of the Pre-Socratics, assert that Aristotle's "judgments are often distorted by his view of earlier philosophy as a stumbling progress toward the truth that Aristotle himself revealed in his physical doctrines." There was also an extensive oral tradition. Both the oral and the written were commonly read or known by all educated men in the region.
Aristotle's philosophy had a distinct stamp: it professed the theory of matter and form, which modern scholastics have dubbed hylomorphism. Though once very widespread, it was not generally adopted by rationalist and modern science, as it mainly is useful in metaphysical analyses, but does not lend itself to the detail that is of interest to modern science. It is not clear that the theory of matter and form existed as early as Thales, and if it did, whether Thales espoused it.
While some historians, like B. Snell, maintain that Aristotle was relying on a pre-Platonic written record by Hippias rather than oral tradition, this is a controversial position. Representing the scholarly consensus Dicks states that "the tradition about him even as early as the fifth century B.C., was evidently based entirely on hearsay....It would seem that already by Aristotle's time the early Ionians were largely names only to which popular tradition attached various ideas or achievements with greater or less plausibility".He points out that works confirmed to have existed in the sixth century BC by Anaximander and Xenophanes had already disappeared by the fourth century BC, so the chances of Pre-Socratic material surviving to the age of Aristotle is almost nil (even less likely for Aristotle's pupils Theophrastus and Eudemus and less likely still for those following after them).
The main secondary source concerning the details of Thales' life and career is Diogenes Laërtius, " Lives of Eminent Philosophers ".This is primarily a biographical work, as the name indicates. Compared to Aristotle, Diogenes is not much of a philosopher. He is the one who, in the Prologue to that work, is responsible for the division of the early philosophers into "Ionian" and "Italian", but he places the Academics in the Ionian school and otherwise evidences considerable disarray and contradiction, especially in the long section on forerunners of the "Ionian School". Diogenes quotes two letters attributed to Thales, but Diogenes wrote some eight centuries after Thales' death and that his sources often contained "unreliable or even fabricated information", hence the concern for separating fact from legend in accounts of Thales.
It is due to this use of hearsay and a lack of citing original sources that leads some historians, like Dicks and Werner Jaeger, to look at the late origin of the traditional picture of Pre-Socratic philosophy and view the whole idea as a construct from a later age, "the whole picture that has come down to us of the history of early philosophy was fashioned during the two or three generations from Plato to the immediate pupils of Aristotle".
Anaximander, was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia. He belonged to the Milesian school and learned the teachings of his master Thales. He succeeded Thales and became the second master of that school where he counted Anaximenes and, arguably, Pythagoras amongst his pupils.
Anaximenes of Miletus was an Ancient Greek Pre-Socratic philosopher active in the latter half of the 6th century BC. The details of his life are obscure because none of his work has been preserved. Anaximenes' ideas and philosophies are only known today because of comments made by Aristotle and other writers on the history of Greek philosophy.
Democritus was an Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe.
Empedocles was a Greek pre-Socratic philosopher and a native citizen of Akragas, a Greek city in Sicily. Empedocles' philosophy is best known for originating the cosmogonic theory of the four classical elements. He also proposed forces he called Love and Strife which would mix and separate the elements, respectively.
Heraclitus of Ephesus son of Bloson, was a pre-Socratic Ionian Greek philosopher, and a native of the city of Ephesus, in modern-day Turkey and then part of the Persian Empire.
Leucippus is reported in some ancient sources to have been a philosopher who was the earliest Greek to develop the theory of atomism—the idea that everything is composed entirely of various imperishable, indivisible elements called atoms. Leucippus often appears as the master to his pupil Democritus, a philosopher also touted as the originator of the atomic theory.
Aristotle and Theophrastos certainly made him [Leucippus] the originator of the atomic theory, and they can hardly have been mistaken on such a point."
Pythagoras of Samos was an ancient Ionian Greek philosopher and the eponymous founder of Pythagoreanism. His political and religious teachings were well known in Magna Graecia and influenced the philosophies of Plato, Aristotle, and, through them, Western philosophy. Knowledge of his life is clouded by legend, but he appears to have been the son of Mnesarchus, a gem-engraver on the island of Samos. Modern scholars disagree regarding Pythagoras's education and influences, but they do agree that, around 530 BC, he travelled to Croton in southern Italy, where he founded a school in which initiates were sworn to secrecy and lived a communal, ascetic lifestyle. This lifestyle entailed a number of dietary prohibitions, traditionally said to have included vegetarianism, although modern scholars doubt that he ever advocated for complete vegetarianism.
Pre-Socratic philosophy is ancient Greek philosophy before Socrates and schools contemporary to Socrates that were not influenced by him. In Classical antiquity, the pre-Socratic philosophers were called physiologoi. Their inquiries spanned the workings of the natural world as well as human society, ethics, and religion, seeking explanations based on natural principles rather than the actions of supernatural gods. They introduced to the West the notion of the world as a kosmos, an ordered arrangement that could be understood via rational inquiry. Coming from the eastern and western fringes of the Greek world, the pre-Socratics were the forerunners of what became Western philosophy as well as natural philosophy, which later developed into the natural sciences. Significant figures include: the Milesians, Heraclitus, Parmenides, Empedocles, Zeno of Elea, and Democritus.
The Seven Sages or Seven Wise Men was the title given by classical Greek tradition to seven philosophers, statesmen, and law-givers of the 6th century BC who were renowned for their wisdom.
Periander, was the Second Tyrant of the Cypselid dynasty that ruled over Corinth. Periander's rule brought about a prosperous time in Corinth's history, as his administrative skill made Corinth one of the wealthiest city states in Greece. Several accounts state that Periander was a cruel and harsh ruler, but others claim that he was a fair and just king who worked to ensure that the distribution of wealth in Corinth was more or less even. He is often considered one of the Seven Sages of Greece, men of the 6th century BC who were renowned for centuries for their wisdom.
Ancient Greek philosophy arose in the 6th century BC and continued throughout the Hellenistic period and the period in which Greece and most Greek-inhabited lands were part of the Roman Empire. Philosophy was used to make sense out of the world in a non-religious way. It dealt with a wide variety of subjects, including astronomy, mathematics, political philosophy, ethics, metaphysics, ontology, logic, biology, rhetoric and aesthetics.
Diogenes of Apollonia was an ancient Greek philosopher, and was a native of the Milesian colony Apollonia in Thrace. He lived for some time in Athens. His doctrines are known chiefly from Diogenes Laërtius and Simplicius. He believed air to be the one source of all being, and, as a primal force, to be intelligent. All other substances are derived from it by condensation and rarefaction. Aristotle has preserved a long passage by Diogenes concerning the organization of the blood vessels.
The Ionian Revolt, and associated revolts in Aeolis, Doris, Cyprus and Caria, were military rebellions by several Greek regions of Asia Minor against Persian rule, lasting from 499 BC to 493 BC. At the heart of the rebellion was the dissatisfaction of the Greek cities of Asia Minor with the tyrants appointed by Persia to rule them, along with the individual actions of two Milesian tyrants, Histiaeus and Aristagoras. The cities of Ionia had been conquered by Persia around 540 BC, and thereafter were ruled by native tyrants, nominated by the Persian satrap in Sardis. In 499 BC, the tyrant of Miletus, Aristagoras, launched a joint expedition with the Persian satrap Artaphernes to conquer Naxos, in an attempt to bolster his position. The mission was a debacle, and sensing his imminent removal as tyrant, Aristagoras chose to incite the whole of Ionia into rebellion against the Persian king Darius the Great.
Arche is a Greek word with primary senses "beginning", "origin" or "source of action", and later "first principle" or "element". By extension, it may mean "first place, power", "method of government", "empire, realm", "authorities", "command". The first principle or element corresponds to the "ultimate underlying substance" and "ultimate undemonstrable principle". In the philosophical language of the archaic period, arche designates the source, origin or root of things that exist. In ancient Greek philosophy, Aristotle foregrounded the meaning of arche as the element or principle of a thing, which although undemonstrable and intangible in itself, provides the conditions of the possibility of that thing.
The Ionian school of Pre-Socratic philosophy was centred in Miletus, Ionia in the 6th century BC. Miletus and its environs was a thriving mercantile melting pot of current ideas of the time. The Ionian School included such thinkers as Thales, Anaximander, Anaximenes, Heraclitus, Anaxagoras, and Archelaus. The collective affinity of this group was first acknowledged by Aristotle who called them physiologoi (φυσιολόγοι), meaning 'those who discoursed on nature'. The classification can be traced to the second-century historian of philosophy Sotion. They are sometimes referred to as cosmologists, since they were largely physicalists who tried to explain the nature of matter.
Archelaus was an Ancient Greek philosopher, a pupil of Anaxagoras, and may have been a teacher of Socrates. He asserted that the principle of motion was the separation of hot from cold, from which he endeavoured to explain the formation of the Earth and the creation of animals and humans.
Eudemus of Rhodes was an ancient Greek philosopher, considered the first historian of science, who lived from c. 370 BC until c. 300 BC. He was one of Aristotle's most important pupils, editing his teacher's work and making it more easily accessible. Eudemus' nephew, Pasicles, was also credited with editing Aristotle's works.
The eclipse of Thales was a solar eclipse that was, according to The Histories of Herodotus, accurately predicted by the Greek philosopher Thales of Miletus. If Herodotus's account is accurate, this eclipse is the earliest recorded as being known in advance of its occurrence. Many historians believe that the predicted eclipse was the solar eclipse of 28 May 585 BC. How exactly Thales predicted the eclipse remains uncertain; some scholars assert the eclipse was never predicted at all. Others have argued for different dates, but only the eclipse of 28 May 585 BC matches the conditions of visibility necessary to explain the historical event.
The Ionian Enlightenment was a set of advances in scientific thought, explanations on nature, and discovering the natural and rational causes behind observable phenomena, that took place in archaic Greece beginning in the 6th century BC. This movement began on the Ionian coast of western Anatolia by small numbers of forward-thinking Greeks from cities such as Miletus, Samos, and Halicarnassus. They saw the world as something ordered and intelligible, its history following an explicable course and its different parts arranged in a comprehensible system. Most historians agree that Thales, one of the Seven Sages of Greece, started this movement by predicting a solar eclipse that actually occurred, though some believe this feat to be false.
Apeiron is a Greek word meaning "(that which is) unlimited," "boundless", "infinite", or "indefinite" from ἀ- a-, "without" and πεῖραρ peirar, "end, limit", "boundary", the Ionic Greek form of πέρας peras, "end, limit, boundary". It is akin to Persian piramon, meaning "boundary, circumference, surrounding".
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The European Southern Observatory has released new images of nebula N44 in the Large Magellanic Cloud. Astronomers used the ESO’s Wide-Field-Imager on the 2.2 metre La Silla Observatory to capture the area with unprecedented clarity. N44 is approximately 1,000 light-years across and contains about 40 bright luminous blue stars. The blue stars live for a very short time and then explode as supernovae – some have already exploded in the area, creating some of the nebula’s visible material.
The two best known satellite galaxies of the Milky Way, the Magellanic Clouds, are located in the southern sky at a distance of about 170,000 light-years. They host many giant nebular complexes with very hot and luminous stars whose intense ultraviolet radiation causes the surrounding interstellar gas to glow.
The intricate and colourful nebulae are produced by ionised gas that shines as electrons and positively charged atomic nuclei recombine, emitting a cascade of photons at well defined wavelengths. Such nebulae are called “H II regions”, signifying ionised hydrogen, i.e. hydrogen atoms that have lost one electron (protons). Their spectra are characterized by emission lines whose relative intensities carry useful information about the composition of the emitting gas, its temperature, as well as the mechanisms that cause the ionisation. Since the wavelengths of these spectral lines correspond to different colours, these alone are already very informative about the physical conditions of the gas.
N44 in the Large Magellanic Cloud is a spectacular example of such a giant H II region. Having observed it in 1999 (see ESO PR Photos 26a-d/99), a team of European astronomers again used the Wide-Field-Imager (WFI) at the MPG/ESO 2.2-m telescope of the La Silla Observatory, pointing this 67-million pixel digital camera to the same sky region in order to provide another striking – and scientifically extremely rich – image of this complex of nebulae. With a size of roughly 1,000 light-years, the peculiar shape of N44 clearly outlines a ring that includes a bright stellar association of about 40 very luminous and bluish stars.
These stars are the origin of powerful “stellar winds” that blow away the surrounding gas, piling it up and creating gigantic interstellar bubbles. Such massive stars end their lives as exploding supernovae that expel their outer layers at high speeds, typically about 10,000 km/sec.
It is quite likely that some supernovae have already exploded in N44 during the past few million years, thereby “sweeping” away the surrounding gas. Smaller bubbles, filaments, bright knots, and other structures in the gas together testify to the extremely complex structures in this region, kept in continuous motion by the fast outflows from the most massive stars in the area.
The new WFI image of N44
The colours reproduced in the new image of N44, shown in PR Photo 31a/03 (with smaller fields in more detail in PR Photos 31b-e/03) sample three strong spectral emission lines. The blue colour is mainly contributed by emission from singly-ionised oxygen atoms (shining at the ultraviolet wavelength 372.7 nm), while the green colour comes from doubly-ionised oxygen atoms (wavelength 500.7 nm). The red colour is due to the H-alpha line of hydrogen (wavelength 656.2 nm), emitted when protons and electrons combine to form hydrogen atoms. The red colour therefore traces the extremely complex distribution of ionised hydrogen within the nebulae while the difference between the blue and the green colour indicates regions of different temperatures: the hotter the gas, the more doubly-ionised oxygen it contains and, hence, the greener the colour is.
The composite photo produced in this way approximates the real colours of the nebula. Most of the region appears with a pinkish colour (a mixture of blue and red) since, under the normal temperature conditions that characterize most of this H II region, the red light emitted in the H-alpha line and the blue light emitted in the line of singly-ionised oxygen are more intense than that emitted in the line of the doubly-ionised oxygen (green).
However, some regions stand out because of their distinctly greener shade and their high brightness. Each of these regions contains at least one extremely hot star with a temperature somewhere between 30,000 and 70,000 degrees. Its intense ultraviolet radiation heats the surrounding gas to a higher temperature, whereby more oxygen atoms are doubly ionised and the emission of green light is correspondingly stronger, cf. PR Photo 31c/03.
Original Source: ESO News Release | 0.891362 | 3.95642 |
These images taken by the NASA/ESA Hubble Space Telescope reveal Comet Holmes’s bright core. The images show that the coma, the cloud of dust and gas encircling the comet, is getting fainter over time. The coma was brightest in the image taken on 29 October 2007. It was two times fainter than on 31 October and nine times dimmer on 4 November (compared to the observations on 29 October).
The coma is getting fainter because it is expanding. A huge number of small dust particles were created during the 23 October outburst. Those particles have since been moving away from the nucleus and filling interplanetary space. The coma therefore is becoming more diffuse over time.
The nucleus, however, is still active and is producing a significant amount of new dust. So the region around the nucleus is still much brighter (at least 10 times brighter) than it usually is at this point in the comet’s orbit. | 0.865242 | 3.401204 |
eso1804 — Photo Release
Glory From Gloom
31 January 2018
A dark cloud of cosmic dust snakes across this spectacular wide field image, illuminated by the brilliant light of new stars. This dense cloud is a star-forming region called Lupus 3, where dazzlingly hot stars are born from collapsing masses of gas and dust. This image was created from images taken using the VLT Survey Telescope and the MPG/ESO 2.2-metre telescope and is the most detailed image taken so far of this region.
The Lupus 3 star forming region lies within the constellation of Scorpius (The Scorpion), only 600 light-years away from Earth. It is part of a larger complex called the Lupus Clouds, which takes its name from the adjacent constellation of Lupus (The Wolf). The clouds resemble smoke billowing across a background of millions of stars, but in fact these clouds are a dark nebula.
Nebulae are great swathes of gas and dust strung out between the stars, sometimes stretching out over hundreds of light-years. While many nebulae are spectacularly illuminated by the intense radiation of hot stars, dark nebulae shroud the light of the celestial objects within them. They are also known as absorption nebulae, because they are made up of cold, dense particles of dust that absorb and scatter light as it passes through the cloud.
Lupus 3 has an irregular form, appearing like a misshapen snake across the sky. In this image it is a region of contrasts, with thick dark trails set against the glare of bright blue stars at the centre. Like most dark nebulae, Lupus 3 is an active star formation region, primarily composed of protostars and very young stars. Nearby disturbances can cause denser clumps of the nebula to contract under gravity, becoming hot and pressurised in the process. Eventually, a protostar is born out of the extreme conditions in the core of this collapsing cloud.
The two brilliant stars in the centre of this image underwent this very process. Early in their lives, the radiation they emitted was largely blocked by the thick veil of their host nebula, visible only to telescopes at infrared and radio wavelengths. But as they grew hotter and brighter, their intense radiation and strong stellar winds swept the surrounding areas clear of gas and dust, allowing them to emerge gloriously from their gloomy nursery to shine brightly.
Understanding nebulae is critical for understanding the processes of star formation — indeed, it is thought that the Sun formed in a star formation region very similar to Lupus 3 over four billion years ago. As one of the closest stellar nurseries, Lupus 3 has been the subject of many studies; in 2013, the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile captured a smaller picture of its dark smoke-like columns and brilliant stars (eso1303).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and by Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.887801 | 3.801013 |
Quarter* ♏ Scorpio
Moon phase on 9 February 2053 Sunday is Waning Gibbous, 21 days old Moon is in Scorpio.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 6 days on 3 February 2053 at 04:57.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing about ∠9° of ♏ Scorpio tropical zodiac sector.
Lunar disc appears visually 7.8% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1798" and ∠1944".
Next Full Moon is the Worm Moon of March 2053 after 23 days on 4 March 2053 at 17:09.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 21 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 656 of Meeus index or 1609 from Brown series.
Length of current 656 lunation is 29 days, 17 hours and 19 minutes. It is 2 hours and 39 minutes longer than next lunation 657 length.
Length of current synodic month is 4 hours and 35 minutes longer than the mean length of synodic month, but it is still 2 hours and 28 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠217.6°. At the beginning of next synodic month true anomaly will be ∠251.9°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
8 days after point of perigee on 1 February 2053 at 05:49 in ♋ Cancer. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 3 days, until it get to the point of next apogee on 13 February 2053 at 01:22 in ♐ Sagittarius.
Moon is 398 590 km (247 672 mi) away from Earth on this date. Moon moves farther next 3 days until apogee, when Earth-Moon distance will reach 405 090 km (251 711 mi).
3 days after its ascending node on 6 February 2053 at 03:39 in ♍ Virgo, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 20 February 2053 at 15:44 in ♓ Pisces.
3 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the beginning to the first part of it.
9 days after previous North standstill on 31 January 2053 at 05:58 in ♋ Cancer, when Moon has reached northern declination of ∠18.289°. Next 4 days the lunar orbit moves southward to face South declination of ∠-18.230° in the next southern standstill on 13 February 2053 at 20:10 in ♐ Sagittarius.
After 9 days on 18 February 2053 at 16:31 in ♒ Aquarius, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.122442 |
The cosmic lens to the edge of the universe
Today it is the farthest ‘ telescope ‘ known that nature has made available, but it is not made of glass, mirrors and gears. Its lens is a galaxy far away, at 9.4 billion light years from us, so that its mass has allowed deflecting and amplifying light from another galaxy placed exactly behind it, as required by Einstein’s General Theory of Relativity. To find it was an international team of astronomers led by Arjen van der Wel of the Max Planck Institute for Astronomy and who has participated Andrea Gratian, a researcher at INAF – Observatory Astronomic in Roma.
And to be able to identify this galaxy took two ‘ artificial ‘telescopes and yes, those made of glass, mirrors and a lot of electronic gear, including the most advanced tools for the exploration of the cosmos built to date by man, the telescope binocular LBT (Large Binocular Telescope) in which the INAF is one of the partners, as well as the Hubble Space Telescope.
The discovery of the galaxy – lens was entirely fortuitous. The team was actually looking very massive and evolved objects at long distances in the universe, in the portion of the sky scanned by the Hubble Space Telescope as part of the candles. The candidate objects were then observed with the spectrograph LIGHTS (the instrument Multifunction Large Binocular Telescope Near- infrared Utility with Camera and Integral Field Unit) at the Large Binocular Telescope. It soon became apparent from the data that one of the spectra reproduced the expected characteristics, as it appeared to come from a very young, celestial object and at the same time as far as the other nominated galaxies.
So Van der Wel and his team are back to compare the spectrum with suspicion images produced by the Hubble Space Telescope of the same portion of the sky, finding that the corresponding object was an evolved galaxy which had a ring of blue color, associated to the young galaxies which are in the middle of star formation. A pretty clear indication that exactly behind the galaxy, perfectly aligned along our line of sight, there was another galaxy, whose light was deflected and focused for the phenomenon of gravitational lensing. Combining the available images and subtracting the contribution due to the image bright stars in the galaxy in the foreground, evidence emerged of suspicion, or the so-called ‘ Einstein ring ‘: a circle light, the result of the bending of light from the galaxy remote from the more ‘close‘. The quotes are a must, since the object that has played the role of the natural lens is exceptional distance of 9.4 billion light years, and the effect was produced at a time when the universe was less than a third of its current age. But this discovery is valuable to astronomers also in another respect: the intensity of the gravitational lens is directly related to the mass of the celestial object that acts as a lens. The greater the mass of the galaxy, both the part of ordinary matter that obscures, the more marked is the refraction of light. “This event permits us to predict the mass of the elliptical galaxy by studying its effect of gravitational lensing,” illuminates Andrea Gratian, co-writer of the paper describing the discovery, published today on the website of The Astrophysical Journal Letters. “Therefore we are capable to ‘calibrate’ the supplementary ways and means for the estimation of the masses that are done in an indirect way, that is by comparing the light of distant galaxies with the theoretical predictions which in turn are calibrated to reproduce the physical properties of the galaxies in our cosmic vicinity “. There is an alternative important phase that this finding raises. “Our recent data points to that this type of alignments in the early universe is very rare,” continued Gratian. “The fact that we found this particular configuration in a very small portion of the sky may indicate that cosmic objects that are behind gravitational lenses are far more numerous than expected and it may change the knowledge we have of the early universe. In future investigations, in this field, LBT will continue to play a decisive role. ” | 0.894193 | 3.989093 |
This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.
SALT LAKE CITY — Early this morning, an unmanned spacecraft traveling at 77,000 miles per hour sent its final data transmissions back to earth as it willingly plunged into Saturn’s gaseous atmosphere and disappeared forever.
For the last 13 years, the Cassini spacecraft has been orbiting Saturn while recording data on the planet and its most interesting features. With water, gasses, space dust, asteroids and at least 53 moons in its orbit, Saturn could be viewed as a microcosm of our solar system.
“You really can think of it as a planetary system on its own,” said Ben Bromely, the physics and astronomy chair at the University of Utah.
Because no planet in our solar system has such a diversity of material present in its orbit, Cassini gave astronomers and researchers like Bromely the chance to investigate a range of questions that are relevant to our broader understanding of the cosmos.
Bromely studies the processes that lead to the formation of planets, and he is particularly interested in what Cassini has revealed about Saturn’s moons.
“It has informed us about fundamental processes that take place among planetary material and other stars,” Bromely notes. “So, it’s really like a laboratory for how things have formed. In that way, it tells us more directly about the formation of other planets like earth.”
Measuring 22 feet across, Cassini weighed about 6.2 tons when it was launched in 1997. About half of that weight was fuel, which was nearly spent when Cassini pierced Saturn’s inhospitable upper atmosphere and made its final recordings of precious data that could only be obtained by means of a suicide mission.
The other half of that weight included a dozen instruments and a detachable probe with six instruments of its own that parachuted onto the surface of the moon Titan in 2005. Cassini’s instruments continuously recorded physical, electrical and magnetic data for scientists like Bromely to interpret.
Among those instruments were a pair of digital cameras, which sent back over 400,000 incredible images that anyone can appreciate.
Here are just a few of the highlights:
To see a full gallery, visit NASA’s Cassini website. The Cassini-Huygens mission was supported by NASA, the European Space Agency and the Italian Space Agency.
Robert Lawrence has worked in academic research and public health and now writes about science. He studied biochemistry at the University of Utah and Arizona State University. You can find more of his work at www.robertlawrencephd.com. | 0.841248 | 3.496584 |
Neutron stars are the most extreme objects in the universe that have been proven to exist. Black holes are very likely, but we’re still not 100% sure about them. A black hole is like a giant squid in the ocean. We’re pretty sure they exist, but nobody has caught one. The neutron star on the other hand is like a blue whale, everybody knows they exist, and they are massive, rare, and beautiful. Of course, once we know something exists, the next logical step is to figure out how it behaves, to characterize and generalize it, and to identify where it’s likely to be found. So what do we know about neutron stars?
Because a Neutron star would become a black hole if it became massive enough, there must be an upper limit to how large it can be. Similarly, if the star that produced it wasn’t massive enough, we wouldn’t end up with a neutron star in the first place. This means there is a range of possible masses for a neutron star. But how can we figure it out? We know the lower limit from studies of supernova explosions and the dynamics of massive stars. The upper limit is more interesting though. How big can a Neutron star become before it collapses into a black hole?
A Neutron star is characterized by incredible density, a huge amount of mass crammed into a relatively small space. If the Sun were compressed into a neutron star, it would be only the size of a large city. A single teaspoon of neutron star would weigh as much as a mountain. That’s how dense it is.
And if you keep adding mass to a neutron star, it can’t keep growing forever. Eventually there will come a point where it’s density increases so much that it will collapse into a black hole. For a nonrotating star, we can calculate this critical point. But there’s a catch; If the star is rotating, it’s inertia will resist the collapse, meaning you can add even more mass without it collapsing into a black hole. And the faster it rotates, the more mass you can add to it without reaching the critical point of collapse.
But there is a limit to this too, because if a star rotates quickly enough, there is nothing to prevent it from breaking apart. So there must be some absolute maximum mass for a stable rotating Neutron star that will neither collapse, nor fly apart. But this quantity is very hard to calculate, because it requires us to know the equation of state of the Neutron star. Or does it?
An equation of state is the relationship of the properties of matter for a given object. It’s usually the relationship between temperature, pressure, volume, etc. The ideal gas law PV=nRT is a simple equation of state you may remember from Chemistry. Finding the equation of state for a Neutron star, on the other hand, is very difficult, and mostly unknown.
So barring a scientific breakthrough, there’s no way to find the upper mass limit for a neutron star. Well guess what happened?
A Scientific Breakthrough!
Astronomers in Germany have found a mathematical way to describe the mass of a neutron star, without relying on the equation of state, essentially cancelling it out of the equations. “It is quite remarkable that a system as complex as a rotating neutron star can be described by such a simple relation,” declares Prof. Luciano Rezzolla, one of the authors of the publication and Chair of Theoretical Astrophysics at the Goethe University in Frankfurt. “Surprisingly, we now know that even the fastest rotation can at most increase the maximum mass of 20% at most,” remarks Rezzolla.
It’s all part of a series of recent relations discovered for Neutron stars, and it’s transforming our understanding of their properties. The next task is to identify what can be learned from the new relation, and how it can help characterize and prove new theories of how Neutron stars behave. And where one relation ends, the next begins, meaning an understanding of the upper limit of Neutron stars leads in to an understanding of the lower limit of our giant squid – Black holes. | 0.822928 | 3.848976 |
A measure of the true brightness of an object. The absolute brightness or magnitude of an object is the apparent brightness or magnitude it would have if it were located exactly 32.6 light-years (10 parsecs) away. For example, the apparent brightness of our Sun is much greater than that of the star Rigel in the constellation Orion because it is so close to us. However, if both objects were placed at the same distance from us, Rigel would appear much brighter than our Sun because its absolute brightness is much larger.
The coldest possible temperature, at which all molecular motion stops. On the Kelvin temperature scale, this temperature is the zero-point (0 K), which is equivalent to -273°C and -460°F.
The process by which light transfers its energy to matter. For example, a gas cloud can absorb starlight that passes through it. After the starlight passes through the cloud, dark lines called absorption lines appear in the star’s continuous spectrum at wavelengths corresponding to the light-absorbing elements.
A dark line in a continuous spectrum caused by absorption of light. Each chemical element emits and absorbs radiated energy at specific wavelengths, making it possible to identify the elements present in the atmosphere of a star or other celestial body by analyzing which absorption lines are present.
A model for the universe in which a repulsive force counteracts the attractive force of gravity, driving all the matter in the universe apart at speeds that increase with time. Recent observations of distant supernova explosions suggest that we may live in an accelerating universe.
A relatively flat, rapidly rotating disk of gas surrounding a black hole, a newborn star, or any massive object that attracts and swallows matter. Accretion disks around stars are expected to contain dust particles and may show evidence of active planet formation. Beta Pictoris is an example of a star known to have an accretion disk.
A very bright, compact region found at the center of certain galaxies. The brightness of an active galactic nucleus is thought to come from an accretion disk around a supermassive black hole. The black hole devours matter from the accretion disk, and this infall of matter provides the firepower for quasars, the most luminous type of active galactic nucleus.
A galaxy possessing an active galactic nucleus at its center.
An optical camera aboard the Hubble Space Telescope that uses CCD detectors to make images. The camera covers twice the area, has twice the sharpness, and is up to 10 times more efficient than the telescopes Wide Field and Planetary Camera 2. The ACS wavelength range spans from ultraviolet to near-infrared light. The cameras sharp eye and broader viewing area allow astronomers to study the life cycles of galaxies in the remotest regions of the universe. Astronauts installed the camera aboard the telescope in March 2002, but the camera experienced an electrical short in 2007 that shut down all but one data channel. During Servicing Mission 4 in 2009, astronauts replaced the failed circuit boards and added a new power supply box to restore power to the camera.
The fading fireball of a gamma-ray burst – a sudden burst of gamma rays from deep space – that is observable in less energetic wavelengths, such as X-ray, optical, and radio. After an initial explosion, an expanding gamma-ray burst slows and sweeps up surrounding material, generating the afterglow, which is visible for several weeks or months. The afterglow is usually extremely faint, making it difficult to locate and study.
A mixture of two or more metals. Brass (a mixture of copper and zinc) and bronze (a mixture of copper and tin) are common alloys.
A process by which lighter elements capture helium nuclei (alpha particles) to form heavier elements. For example, when a carbon nucleus captures an alpha particle, a heavier oxygen nucleus is formed.
A type of telescope mounting that supports the weight of the telescope and allows it to move in two directions to locate a specific target. One axis of support is vertical (called the altitude) and allows the telescope to move up and down. The other axis is horizontal (called the azimuth) and allows the telescope to swing in a circle parallel to the ground. This makes it easy to position the telescope: swing it around in a circle and then lift it to the target. However, tracking an object as the Earth turns is more complicated. The telescope needs to be adjusted in both directions while tracking, which requires a computer to control the telescope.
To make larger or more powerful; increase. Radio signals are amplified because they are very weak.
The size of a wave from the top of a wave crest to its midpoint.
A property that an object, such as a planet revolving around the Sun, possesses by virtue of its rotation or circular motion. An object’s angular momentum cannot change unless some force acts to speed up or slow down its circular motion. This principle, known as conservation of angular momentum, is why an object can indefinitely maintain a circular motion around an axis of revolution or rotation.
The ability of an instrument, such as a telescope, to distinguish objects that are very close to each other. The angular resolution of an instrument is the smallest angular separation at which the instrument can observe two neighboring objects as two separate objects. The angular resolution of the human eye is about a minute of arc. As car headlights approach from a far-off point, they appear as a single light until the separation between the lights increases to a point where they can be resolved as two separate lights.
The apparent size of an object as seen by an observer; expressed in units of degrees (of arc), arc minutes, or arc seconds. The moon, as viewed from the Earth, has an angular diameter of one-half a degree.
An electrical device used to send or receive electromagnetic waves. The aerial (a long piece of metal attached to the front or rear fender) on a car is the antenna for the radio.
Matter made up of elementary particles whose masses are identical to their normal-matter counterparts but whose other properties, such as electric charge, are reversed. The positron is the antimatter counterpart of an electron, with a positive charge instead of a negative charge. When an antimatter particle collides with its normal-matter counterpart, both particles are annihilated and energy is released.
A measure of the brightness of a celestial object as it appears from Earth. The Sun is the brightest object in Earth’s sky and has the greatest apparent magnitude, with the moon second. Apparent brightness does not take into account how far away the object is from Earth.
One arc minute is 1/60 of a degree of arc. The angular diameter of the full moon or the Sun as seen from Earth is about 30 arc minutes.
One arc second is 1/60 of an arc minute and 1/3600 of an arc degree. The apparent size of a dime about 3.7 kilometers (2.3 miles) away would be an arc second. The angular diameter of Jupiter varies from about 30 to 50 arc seconds, depending on its distance from Earth.
An orderly arrangement or impressive display. For radio telescopes, an array is a group of individual radio dishes that work together. The VLA (Very Large Array) has 27 telescope dishes arranged in a “Y” pattern.
A consortium of educational and other non-profit institutions that operates world-class astronomical observatories. Members include five international affiliates and 29 U.S. institutions, including the Space Telescope Science Institute in Baltimore, Maryland, the science operations center for NASA’s Hubble Space Telescope.
A small solar system object composed mostly of rock. Many of these objects orbit the Sun between Mars and Jupiter. Their sizes range anywhere from 33 feet (10 meters) in diameter to less than 620 miles (1,000 kilometers). The largest known asteroid, Ceres, has a diameter of 579 miles (926 kilometers).
A region of space between Mars and Jupiter where the great majority of asteroids is found.
A scientist who studies the universe and the celestial bodies residing in it, including their composition, history, location, and motion. Many of the scientists at the Space Telescope Science Institute are astronomers. Astronomers from all over the world use the Hubble Space Telescope.
The average distance between the Earth and the Sun, which is about 150 million kilometers (93 million miles). This unit of length is commonly used for measuring the distances between objects within the solar system.
The study of the universe and the celestial bodies that reside in it, including their composition, history, location, and motion.
The layer of gases surrounding the surface of a planet, moon, or star.
The blurring of an image due to the layer of gases surrounding the surface of Earth. As starlight travels through the atmosphere, pockets of air act like little lenses and bend the light in unpredictable ways. This distortion causes stars to appear to twinkle.
The smallest unit of matter that possesses chemical properties. All atoms have the same basic structure: a nucleus containing positively charged protons with an equal number of negatively charged electrons orbiting around it. In addition to protons, most nuclei contain neutral neutrons whose mass is similar to that of protons. Each atom corresponds to a unique chemical element determined by the number of protons in its nucleus.
The positively charged core of an atom consisting of protons and (except for hydrogen) neutrons, and around which electrons orbit.
A phenomenon produced when the solar wind (made up of energized electrons and protons) disturbs the atoms and molecules in a planet’s upper atmosphere. Some of the energy produced by these disturbances is converted into colorful visible light, which shimmers and dances. Auroras have been seen on several planets in our solar system. On Earth, auroras are also known as the “Northern Lights” (aurora borealis) or “Southern Lights” (aurora australis), depending on in which polar region they appear.
An imaginary line through the center of an object. The object rotates around this line.
A galaxy with a “bar” of stars and interstellar matter, such as dust and gas, slicing across its center. The Milky Way is thought to be a barred spiral galaxy.
The distance between two or more telescopes that are working together as a single instrument to observe celestial objects. The wider the baseline, the greater the resolving power.
A high-energy astrophysics “experiment” used to investigate gamma-ray bursts (GRBs). BATSE consisted of eight detectors that were mounted on the corners of NASAs Earth-orbiting Compton Gamma-Ray Observatory, whose mission ended in 2000.
Batteries provide all the electrical power to support Hubble operations during the night portion of its orbit, when the telescope is in Earth’s shadow. The telescope's orbit is approximately 97 minutes long. Roughly 61 minutes of Hubble’s orbit are in sunlight and 36 minutes are in Earth’s shadow. During Hubble’s sunlight or daytime period, the solar arrays provide power to the onboard electrical equipment. The solar arrays also charge the spacecraft’s batteries so they can power the spacecraft during the night portion of Hubble’s orbit. Hubble has six nickel-hydrogen batteries. These batteries, which had been onboard Hubble since the telescope was launched in 1990, were replaced during Servicing Mission 4.
A space-based X-ray observatory built and operated by the Italian Space Agency and the Netherlands Agency for Aerospace Programs. BeppoSAX has been instrumental in identifying and locating gamma-ray bursts.
A broadly accepted theory for the origin and evolution of our universe. The theory says that the observable universe started roughly 13.7 billion years ago from an extremely dense and incredibly hot initial state.
A system of two stars orbiting around a common center of mass that are bound together by their mutual gravitational attraction.
A region of space containing a huge amount of mass compacted into an extremely small volume. A black hole’s gravitational influence is so strong that nothing, not even light, can escape its grasp. Swirling disks of material – called accretion disks – may surround black holes, and jets of matter may arise from their vicinity.
The shortening of a light wave from an object moving toward an observer. For example, when a star is traveling toward Earth, its light appears bluer.
A massive, hot star that appears blue in color. Spica in the constellation Virgo is an example of a blue star.
Large, brilliant meteors that enter the Earth’s atmosphere. Friction between a fast-moving meteor and Earth’s air molecules generates tremendous heat, which causes the meteor to heat up, glow, and perhaps disintegrate. In some cases, the meteor literally explodes, leaving a visible cloud that dissipates slowly.
An object too small to be an ordinary star because it cannot produce enough energy by fusion in its core to compensate for the radiative energy it loses from its surface. A brown dwarf has a mass less than 0.08 times that of the Sun.
The spherical structure at the center of a spiral galaxy that is made up primarily of old stars, gas, and dust. The Milky Way’s bulge is roughly 15,000 light-years across.
A meteorite with embedded pebble-sized granules that contain significant quantities of organic (complex carbon-rich) matter.
A type of reflecting telescope whose eyepiece is located behind the primary mirror. The primary mirror is cast with a hole in the center. When light enters the telescope, it reflects from the primary mirror to the secondary mirror. The secondary mirror reflects the light back through the hole in the primary mirror to the eyepiece.
Of or relating to the sky or visible objects in the sky, like the Moon, Sun, planets, comets, asteroids, stars, and galaxies.
An object in the sky – examples include the Moon, the Sun, planets, comets, asteroids, stars, and galaxies.
An imaginary sphere encompassing the Earth that represents the sky. Astronomers chart the sky using the celestial coordinates of the sphere to locate objects in the cosmos. This sphere is divided into 88 sections called constellations. Objects are sometimes named for the major constellation in which they appear.
A temperature scale on which the freezing point of water is 0°C and the boiling point is 100°C.
A type of pulsating star whose light and energy output vary noticeably over a set period of time. The time period over which the star varies is directly related to its light output or luminosity, making these stars useful standard candles for measuring intergalactic distances.
A space-based X-ray observatory; also known as the Advanced X-ray Astrophysics Facility (AXAF). Chandra is designed to observe X-rays from high-energy regions of the universe, such as hot gas in the remnants of exploded stars. The satellite was launched and deployed in July 1999.
An electronic detector that records visible light from stars and galaxies to make photographs. These detectors are very sensitive to the extremely faint light of distant galaxies. They can see objects that are 1,000 million times fainter than the eye can see. CCDs are electronic circuits composed of light-sensitive picture elements (pixels), tiny cells that, placed together, resemble mesh on a screen door. The same CCD technology is used in digital cameras.
A pure substance consisting of atoms or ions of two or more different elements. The elements are in definite proportions. A chemical compound usually possesses properties unlike those of its constituent elements. For example, table salt (the common name for sodium chloride) is a chemical compound made up of the elements chlorine and sodium.
The chemical (i.e., pre-biological) changes that transformed simple atoms and molecules into the more complex chemicals needed for the origin of life. For example, hydrogen atoms in the cores of stars combine through nuclear fusion to form the heavier element helium.
The building blocks that enable life to form and to sustain itself. Life as we know it requires a source of energy, organic (carbon-based) compounds, and water. Scientists believe that atmospheric detection of water, oxygen, methane, carbon dioxide, and other compounds can signal the possibility of life on a planet.
Visible light is made of different colors. When visible light passes through a glass lens or a prism, it gets dispersed, or split, into its many colors. A lens focuses each color at a different point, causing a fringe of color to appear around bright objects. Looking at only red and blue light:
The middle layer of the solar atmosphere between the photosphere and the corona. The chromosphere is roughly 10,000 kilometers (6,200 miles) thick and is composed primarily of hydrogen. It varies in temperature from below 10,000 Kelvin (18,000°F) to over 100,000 Kelvin (180,000°F).
A geometric model of the universe in which the overall structure of the universe closes upon itself like the surface of a sphere. The rules of geometry in a closed universe are like those that would apply on the surface of a sphere.
A system of two moveable mirrors used in solar telescopes. The mirrors follow the Sun and keep its image in the same location as Earth rotates.
The area of a telescope’s primary light-collecting mirror. A telescope’s light-gathering power rises with an increase in its collecting area.
A galactic “car wreck” in which two galaxies pass close enough to gravitationally disrupt each other’s shape. The collision rips streamers of stars from the galaxies, fuels an explosion of star birth, and can ultimately result in both galaxies merging into one.
An event involving a collision of objects; for example, the excitation of a hydrogen atom when it is hit by an electron.
The visual perception of light that enables human eyes to differentiate between wavelengths of the visible spectrum, with the longest wavelengths appearing red and the shortest appearing blue or violet.
The cloud of gas and dust that forms around a comet’s nucleus. This cloud is created when the solar wind strikes the surface of the nucleus.
A ball of rock and ice, often referred to as a “dirty snowball.” Typically a few kilometers in diameter, comets orbit the Sun in paths that either allow them to pass by the Sun only once or that repeatedly bring them through the solar system (as in the 76-year orbit of Halley's Comet). A comet’s “signature” long, glowing tail is formed when the Sun’s heat warms the coma or nucleus, which releases vapors into space.
The core of a comet, made up of ice, dirt, and rock.
A comet that became gravitationally bound to Jupiter, colliding with the planet in July 1994. Prior to entering the planet's atmosphere, the comet broke into several distinct pieces, each with a separate coma and tail.
A tail is made up of dust and gas from a comet’s coma. A tail forms when the solar wind separates dust and gas from the coma, pushing it outward and away from the Sun in either a slightly curved path (for dust) or a straight path (for gas).
A space-based observatory that collected high-energy gamma-ray light from celestial objects. The Compton satellite consisted of the BATSE, COMPTEL, EGRET, and OSSE instruments. Astronauts aboard the space shuttle Atlantis deployed the CGRO into low-Earth orbit in April 1991. The satellite plunged into the Pacific Ocean in June 2000. Concave vs. convex
A fundamental law of physics, which states that the total amount of mass and energy in the universe remains unchanged. However, mass can be converted to energy, and vice versa.
A geometric pattern of bright stars that appears grouped in the sky. Ancient observers named many constellations after gods, heroes, animals, and mythological beings. Leo (the Lion) is one example of the 88 constellations.
The transfer of heat through a liquid or gas caused by the physical upwelling of hot matter. The heat transfer results in the circulation of currents from lower, hotter regions to higher, cooler regions. An everyday example of this process is boiling water. Convection occurs in the Sun and other stars.
The region below a star’s surface where energy flows outward by the rising of hot gas known as convection.
The central region of a planet, star, or galaxy.
The outermost layer of the atmosphere of a star, including the Sun. The corona is visible during a solar eclipse or when special adapters or filters are attached to a telescope to block the light from the star’s central region. The gaseous corona extends millions of kilometers from the stars surface and has a temperature in the millions of degrees.
Regions in the corona from which the high-speed solar wind is known to originate. Coronal holes, usually found near the Sun’s poles, are large regions in the corona that are less dense and cooler than the surrounding region.
An apparatus installed during the 1993 First Servicing Mission. By placing small and carefully designed mirrors in the telescope, COSTAR successfully improved restored Hubble's vision to its original design goals. All the new instruments installed during the servicing missions have internal corrections for spherical aberration and do not require the services of COSTAR. Hubble’s last original instrument, the Faint Object Camera, was replaced by the Advanced Camera for Surveys during SM3B. COSTAR was replaced by the Cosmic Origins Spectrograph during Servicing Mission 4 and returned to Earth in the space shuttle.
The relative proportions of chemical elements in the Sun, the solar system, and the local region of the Milky Way galaxy. These proportions are determined by studies of the spectral lines in astronomical objects and are averaged for many stars in our cosmic neighborhood. For example, for every million hydrogen atoms in an average star like our Sun, there are 98,000 helium atoms, 360 carbon atoms, 110 nitrogen atoms, 850 oxygen atoms, and so on.
Electromagnetic energy filling the universe that is believed to be the radiation remaining from the Big Bang. It is sometimes called the “primal glow.” This radiation is strongest in the microwave part of the spectrum but has also been detected at radio and infrared wavelengths. The intensity of the cosmic microwave background from every part of the sky is almost exactly the same.
Radiative energy filling the universe that is believed to be the radiation remaining from the Big Bang. It is sometimes called the “primal glow.” This radiation is strongest in the microwave part of the spectrum but has also been detected at radio and infrared wavelengths. The intensity of the cosmic microwave background from every part of the sky is almost exactly the same.
A spectrograph that detects ultraviolet light. A spectrograph works by breaking up light from an object into its individual wavelengths so that its composition, temperature, motion, and other chemical and physical properties can be analyzed. COS will study the structure of the universe and how galaxies, stars and planets formed and evolved. Astronauts installed COS during SM4.
High-energy atomic particles that travel through space at speeds close to the speed of light; also known as cosmic-ray particles.
This principle states that the distribution of matter across very large distances is the same everywhere in the universe and that the universe looks the same in all directions. According to this principle, our view of the universe is like the view from a boat on an ocean, which is essentially the same for any other person on any other boat on any other ocean. Measurements of matter and energy in the universe on the largest observable scales support the cosmological principle.
The investigation of the origin, structure, and development of the universe, including how energy, forces, and matter interact on a cosmic scale.
A bowl-shaped depression caused by a comet or meteorite colliding with the surface of a planet, moon, or asteroid. On geologically active moons and planets (like Earth), craters can result from volcanic activity.
The minimum average density that matter in the universe would need in order for its gravitational pull to slow the universe's expansion to a halt.
Originally the main material used to make flat planes of glass for windows, it is composed of soda-lime glass. It can be used to make lenses and prisms. Crown glass bends and disperses, or spreads out, light less than flint glass.
A region of interstellar space that contains a rich concentration of gas and dust. Such a cloud is often irregular in shape but sometimes has a well-defined edge. Visible light cannot pass through these clouds, so they obscure the light from stars beyond them.
A mysterious force that seems to work opposite to that of gravity and makes the universe expand at a faster pace.
Matter that is too dim to be detected by telescopes. Astronomers infer its existence by measuring its gravitational influence. Dark matter makes up most of the total mass of the universe.
One of two celestial coordinates required to locate an astronomical object, such as a star, on the celestial sphere. Declination is the measure of angular distance of a celestial object above or below the celestial equator and is comparable to latitude. To familiarize yourself with declination, hold out your arm in the direction of the North Star (Polaris). You are now pointing at plus 90 degrees declination. Move your arm downward by 90 degrees. You are now pointing at 0 degrees declination.
One degree of arc is 1/360 of a full circle. The apparent sizes of objects as seen from Earth can be measured in degrees of arc. The angular diameter of the full moon or the Sun as seen from Earth is one-half of a degree.
The ratio of the mass of an object to its volume. For example, water has a density of one gram of mass for every milliliter of volume.
A device used to measure the amount of electromagnetic radiation emitted by celestial objects. Frequently, detectors are used to sense light that is not visible.
A special form of hydrogen (an isotope called “heavy hydrogen”) that has a neutron as well as a proton in its nucleus.
The distance from one side of a circle to the other measured through the center. For telescopes, the diameter of a lens or mirror is measured from one side to the opposite side, passing through the center.
The separation of heavy matter from light matter, thus causing a variation in density and composition. Differentiation occurs in an object like a planet as gravity draws heavier material toward the planet’s center and lighter material rises to the surface.
A device that splits light into its component parts or spectrum. A diffraction grating often consists of a mirror with thousands of closely spaced parallel lines, which spread out the light into parallel bands of colors or distinct fine lines or bars.
A visible image that is recorded by an electronic detector and subdivided into small picture elements (pixels). Each element is assigned a number that corresponds to the brightness recorded at its physical location on the detector. Computer software converts the numerical information into a visual image. The Hubble Space Telescope records digital images.
Visible light is actually made up of different colors. Each color bends by a different amount when refracted by glass. That’s why visible light is split, or dispersed, into different colors when it passes through a lens or prism. Shorter wavelengths, like purple and blue light, bend the most. Longer wavelengths, like red and orange light, bend the least.
The change in the wavelength of sound or light waves caused when the object emitting the waves moves toward or away from the observer; also called Doppler shift. In sound, the Doppler effect causes a shift in sound frequency or pitch (for example, the change in pitch noted as an ambulance passes). In light, an object’s visible color is altered and its spectrum is shifted toward the blue region of the spectrum for objects moving toward the observer and toward the red for objects moving away.
A system of two stars that are gravitationally bound to each other. They orbit each other around a common center. They can also be called binary stars.
A relatively small galaxy. The Large and Small Magellanic Clouds, visible in the Southern Hemisphere, are two dwarf irregular galaxies that are neighbors of the Milky Way.
A celestial body within the solar system that shares the characteristics of planets. It orbits the Sun, is not a moon, and has a spherical or nearly spherical shape. Unlike a planet, however, a dwarf planet has not cleared away any loose cosmic rubble from its orbit. Dwarf planets include Ceres, Pluto, and Eris.
The third planet from the Sun and one of four terrestrial planets in the inner solar system. Earth, the only planet where water exists in large quantities, has an atmosphere capable of supporting myriad life forms. The planet is 150 million kilometers (93 million miles) away from the Sun. Earth has one satellite “the Moon.”
Traveling around Earth, in the path followed by an object moving in the gravitational field of Earth. For example, the telescope travels around, or orbits, Earth because Earth’s gravitational field keeps the telescope in its path, or orbit.
A fundamental force that governs all interactions among electrical charges and magnetism. Essentially, all charged particles attract oppositely charged particles and repel identically charged particles. Similarly, opposite poles of magnets attract and like magnetic poles repel.
A form of energy that propagates through space as vibrations of electric and magnetic fields; also called radiation or light. All electromagnetic radiation is a form of light.
The entire range of wavelengths of electromagnetic radiation, including radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.
The science dealing with the physical relationship between electricity and magnetism. The principle of an electromagnet, a magnet generated by electrical current flow, is based on this phenomenon.
A negatively charge elementary particle that typically resides outside the nucleus of an atom but is bound to it by electromagnetic forces. An electron’s mass is tiny: 1,836 electrons equals the mass of one proton.
A unit of energy that is equal to the energy that an electron gains as it moves through a potential difference of one volt. This very small amount of energy is equal to 1.602 * 10-19 joules. Because an electron volt is so small, engineers and scientists sometimes use the terms MeV (mega-million) and GeV (giga-billion) electron volts.
A substance composed of a particular kind of atom. All atoms with the same number of protons (atomic numbers) in the nucleus are examples of the same element and have identical chemical properties. For example, gold (with 79 protons) and iron (with 26 protons) are both elements, but table salt is not because it is made from two different elements: sodium and chlorine. The atoms of a particular element have the same number of protons in the nucleus and exhibit a unique set of chemical properties. There are about 90 naturally occurring elements on Earth.
Particles smaller than atoms that are the basic building blocks of the universe. The most prominent examples are photons, electrons, and quarks.
A special kind of elongated circle. The orbits of the solar system planets form ellipses.
A galaxy that appears spherical or football-shaped. Elliptical galaxies are comprised mostly of old stars and contain very little dust and “cool” gas that can form stars.
A bright line in a spectrum caused by emission of light. Each chemical element emits and absorbs radiated energy at specific wavelengths. The collection of emission lines in a spectrum corresponds to the chemical elements contained in a celestial object.
Natural processes that wear or grind away the surface of an object. On Earth, the major agents of erosion are water and wind.
The minimum velocity required for an object to escape the gravity of a massive object.
A fifteen-member consortium of European countries for the design, development, and deployment of satellites. The Space Telescope European Coordinating Facility (ST-ECF) supports the European astronomical community in exploiting the research opportunities provided by the Earth-orbiting Hubble Space Telescope. The ESA members are Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom, with Canada as a cooperating state.
The spherical outer boundary of a black hole. Once matter crosses this threshold, the speed required for it to escape the black hole’s gravitational grip is greater than the speed of light.
A greater-than-minimum energy state of any atom that is achieved when at least one of its electrons resides at a greater-than-normal distance from its parent nucleus.
The process of allowing electromagnetic radiation to fall on light-sensitive materials such as photographic films or plates. An exposure is also the image created by the process. A long exposure time is needed in order to obtain an image of dim and distant celestial objects.
A planet that orbits a star other than the sun.
An adjective that means “beyond the Earth.” The phrase “extraterrestrial life” refers to possible life on other planets.
The lens or lens group closest to the eye in an optical instrument such as a telescope or microscope.
A temperature scale on which the freezing point of water is 32°F and the boiling point is 212°F.
An instrument aboard the Hubble Space Telescope that recorded high-resolution images of faint celestial objects in deep space. Built by the European Space Agency, the camera collected ultraviolet and visible light from celestial objects. The camera served as Hubble’s telephoto lens recording the most detailed images over a small field of view. The FOC’s resolution allowed Hubble to single out individual stars in distant star clusters. The instrument was replaced in March 2002 during Servicing Mission 3B.
An instrument aboard the Hubble Space Telescope that acted like a prism to separate light from the cosmos into its component colors, providing a wavelength fingerprint of the object being observed. Such information yields clues about an objects temperature, chemical composition, density, and motion. Spectrographic observations also reveal changes in celestial objects as the universe evolves. The instrument was replaced in February 1997 during the Second Servicing Mission.
The region of the infrared spectrum that exhibits the longest wavelengths and the lowest frequencies and energies.
A geological term that refers to a fracture or a break in a hard surface like the Earth’s crust. This area is a zone of weakness and may be the site of earthquakes or volcanoes. All planets or moons with a hard crust are candidates for faults or breaks on their surfaces.
The area of the sky visible through a telescope. The telescope’s viewing area is measured in degrees, arc minutes, or arc seconds. A telescope that can just fit the full moon into its complete viewing area has a field of view of roughly 30 arc minutes.
A type of window that absorbs certain colors of light while allowing others to pass through. Astronomers use filters to observe how celestial objects appear in certain colors of light or to reduce the light of exceptionally bright objects. For example, a pair of sunglasses acts as a type of filter, reducing the amount of incoming light while still allowing some light to pass through to the eyes.
Rotating wheels in a telescope instrument that allow specific colors of light from a celestial object to pass through and form an image on the detector. The Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope has 12 filter wheels, each of which holds four filters.
Cameras that help keep the Hubble Space Telescope pointed precisely in the right direction. These targeting devices aboard the telescope lock onto guide stars and measure their positions relative to the object being viewed. Adjustments based on these precise readings keep Hubble pointed in the right direction. The sensors also are used to perform celestial measurements.
A nuclear process that releases energy when heavyweight atomic nuclei break down into lighter nuclei. Fission is the basis of the atomic bomb.
Small telescopes with wide fields of view that are aboard the Hubble Space Telescope and used in conjunction with the Fine Guidance Sensors. The star trackers locate the bright stars that are used to orient the telescope for scientific observations.
A sudden and violent outburst of solar energy that is often observed in the vicinity of a sunspot or solar prominence; also known as a solar flare.
A geometric model of the universe in which the laws of geometry are like those that would apply on a flat surface such as a table top.
The lead glass that was produced in the United States and the United Kingdom prior to the 1860s. This glass is used to make telescope lenses and prisms. Flint glass bends and disperses, or spreads out, light more than crown glass.
The flow of fluid, particles, or energy through a given area within a certain time. In astronomy, this term is often used to describe the rate at which light flows. For example, the amount of light (photons) striking a single square centimeter of a detector in one second is its flux.
A spacecraft that travels past a celestial object. Frequently, such a spacecraft is unmanned and takes images of the object.
Focal length (shown in orange) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror – the point where parallel rays of light meet, or converge.
The focal point of a lens or mirror is the point in space where parallel light rays meet after passing through the lens or bouncing off the mirror. A “perfect” lens or mirror would send all light rays through one focal point, which would result in the clearest image.
Describes the number of wave crests passing by a fixed point in a given time period (usually one second). Frequency is measured in Hertz (Hz).
A nuclear process that releases energy when light atomic nuclei combine to form heavier nuclei. Fusion is the energy source for stars like our Sun.
The central hub or nucleus of a galaxy. The Milky Way’s galactic center is about 28,000 light-years from Earth.
A flattened disk of gas and young stars in a galaxy. Some galactic disks have material concentrated in spiral arms (as in a spiral galaxy) or bars (as in barred spirals).
Spherical regions around spiral galaxies that contain dim stars and globular clusters. The radius of the halo surrounding the Milky Way extends some 50,000 light-years from the galactic center.
The central concentration of matter (stars, gas, dust, and perhaps a black hole) in a galaxy, typically spanning no more than a few light-years in diameter.
The imaginary projection of the Milky Way’s disk on the sky. Most of the galaxy’s stars and interstellar matter reside in this disk. Objects in the galaxy are often referred to as being above, below, or in the galactic plane.
A collection of stars, gas, and dust bound together by gravity. The smallest galaxies may contain only a few hundred thousand stars, while the largest galaxies have thousands of billions of stars. The Milky Way galaxy contains our solar system. Galaxies are classified or grouped by their shape. Round or oval galaxies are elliptical galaxies and those showing a pinwheel structure are spiral galaxies. All others are called irregular because they do not resemble elliptical or spiral galaxies.
A collection of dozens to thousands of galaxies bound together by gravity.
The study of the birth of galaxies and how they change and develop over time.
A vast collection of galaxy clusters that may contain tens of thousands of galaxies spanning over a hundred million light-years of space. Galaxy superclusters are the largest structures in the universe.
A brief, intense, and powerful burst of gamma rays, the highest-energy, shortest-wavelength radiation in the electromagnetic spectrum. These bursts emanate from distant sources outside our galaxy and last only a few seconds. They are the brightest and most energetic explosions known.
The part of the electromagnetic spectrum with the highest energy; also called gamma radiation. Gamma rays can cause serious damage when absorbed by living cells.
One of Jupiter’s largest moons. Ganymede, the largest satellite in our solar system, is about 5300 kilometers (3300 miles) wide and larger than the planet Mercury.
A glowing cloud of gas in interstellar space. The cloud of gas may be either an emission nebula, which absorbs ultraviolet light from nearby stars and re-radiates visible light, or a reflection nebula, which reflects light off of its dust particles.
A large planet with a small, rocky core and a deep atmosphere composed mostly of hydrogen and helium. Our solar system contains four gas giants: Jupiter, Saturn, Uranus, and Neptune. This group is also known as Jovian planets.
A theory Einstein developed to explain how gravity influences space and time.
An adjective meaning “centered on the Earth.” Most early civilizations had a geocentric view of the universe.
Also known as geostationary. An orbit in which an object circles the Earth once every 24 hours, moving at the same speed and direction as the planet’s rotation. The object remains nearly stationary above a particular point, as observed from Earth. The International Ultraviolet Explorer (IUE) and some weather satellites are examples of satellites in geosynchronous orbit.
A dying star that has used up the hydrogen fuel in its core and has begun to expand. Giant stars are generally larger than our Sun.
A measure of computer data storage capacity equal to approximately a billion bytes. In computer language, a byte of information represents a letter or digit. So, a billion bytes is equal to a billion letters.
A collection of hundreds of thousands of old stars held together by gravity. Globular clusters are usually spherically shaped and are often found in the halos of galaxies. Each star belonging to a cluster revolves around the cluster’s common center of mass.
A science instrument aboard the Hubble Space Telescope that made finely detailed spectroscopic observations of ultraviolet sources. The GHRS was removed from Hubble in February 1997 and replaced with the Space Telescope Imaging Spectrograph.
NASAs flight control center in Greenbelt, Maryland, which receives data from orbiting observatories such as the Hubble Space Telescope (HST). HST digital data are then relayed to the Space Telescope Science Institute in Baltimore, Maryland, where they are interpreted into pictures. Goddard also conducts scientific investigations, develops and operates space systems, and works toward the advancement of space science technologies.
A theory stating that that strong and weak nuclear forces and electromagnetic forces are varying aspects of the same fundamental force.
The process by which a large-scale structure grows as its gravity attracts smaller building blocks. Astronomers believe that all the large-scale structures (such as galaxies, galaxy clusters, and galaxy superclusters) that we see in the universe today formed through gravitational clustering.
A value used in the calculation of the gravitational force between objects. In the equation describing the force of gravity, “G” represents the gravitational constant and is equal to 6.672 * 10-11 Nm2/kg2.
A condition that occurs when an object’s inward-pulling gravitational forces exceed the outward-pushing pressure forces, thus causing the object to collapse on itself. For example, when the pressure forces within an interstellar gas cloud cannot resist the gravitational forces that act to compress the cloud, then the cloud collapses upon itself to form a star.
A massive object that magnifies or distorts the light of objects lying behind it. For example, the powerful gravitational field of a massive cluster of galaxies can bend the light rays from more distant galaxies, just as a camera lens bends light to form a picture.
The reddening of light from a very massive object caused by photons escaping and traveling away from the object’s strong gravitational field. An example of gravitational redshift is light escaping from the surface of a neutron star.
An effect through which an orbiting object, such as a spacecraft or a comet, gains or loses speed by virtue of the gravitational might of a planet or other celestial object that it passes. For example, the Cassini spacecraft in its journey to Saturn used a gravity assist from Earth to increase its velocity by about 36,000 kilometers per hour (22,300 miles per hour).
The attractive force between all masses in the universe. All objects that have mass possess a gravitational force that attracts all other masses. The more massive the object, the stronger the gravitational force. The closer objects are to each other, the stronger the gravitational attraction.
One of the most energetic gamma-ray bursts (GRBs) ever detected, occurring at 4:47 a.m. EST, January 23, 1999. The “burst” equaled the power of nearly 10 million billion suns. It became the first GRB to be viewed simultaneously in both gamma-ray and optical wavelengths.
A circulating storm located in Jupiter’s upper atmosphere. The storm, which rotates around the planet in six days, is the width of two to three Earths. Galileo first observed the spot in the 17th century.
The result of a planet’s atmosphere trapping infrared heat, rather than allowing it to escape into space. This effect increases the planet’s surface temperature, a phenomenon known as global warming.
The minimum energy state of an atom that is achieved when all of its electrons have the lowest possible energy and therefore are as close to the nucleus as possible.
A small collection of galaxies bound together by gravity. The number of galaxies in a group can range from a few to dozens. The Milky Way is a member of the Local Group, a collection of more than 30 galaxies.
A star that a telescopes guidance system locks onto to ensure that a celestial object is followed and observed as the telescope moves, owing either to the Earths rotation or the telescopes orbital trajectory. The Hubble Space Telescope uses two of its three Fine Guidance Sensors to detect and lock onto guide stars. The telescopes science operations center has more than 15 million guide stars in its database the Guide Star Catalogue.
A spinning wheel mounted on a movable frame that assists in stabilizing and pointing a space-based observatory. Gyroscopes are important because they measure the rate of motion as the observatory moves and help ensure the telescope retains correct pointing during observations. The gyroscopes provide the general pointing of the telescope while the fine guidance sensors provide the fine tuning. Gyroscopes are used in navigational instruments for aircraft, satellites, and ships. The Hubble Space Telescope has six gyroscopes for navigation and sighting purposes.
A region around a star where planets with liquid water may be present. A planet on the near edge of the habitable zone would have a surface temperature slightly lower than the boiling point of water. A planet on the distant edge of the habitable zone would have a surface temperature slightly higher than the freezing point of water.
An adjective meaning “centered on the Sun.”
Half of a spherical or roughly spherical body; for example, the northern and southern halves of the Earth, above and below the equator.
A plot showing the relationship between the brightness (luminosity) and the surface temperatures of many stars. Often the spectral class, which is based on the temperature of the star, is used as a label.
An original science instrument aboard the Hubble Space Telescope that made very rapid photometric observations of celestial objects in near-ultraviolet to visible light. The instrument was removed in December 1993 during the First Servicing Mission.
A galaxy in which a cosmic phenomenon, such as a supernova explosion or a gamma-ray burst, has occurred.
A number that expresses the rate at which the universe expands with time. Ho appears to be between 60 and 75 kilometers per second per megaparsec.
A tiny region of the northern sky near the Big Dipper toward which the Hubble Space Telescope was pointed for ten straight days in 1995. Because this observation was designed to detect very faint light from the most distant galaxies Hubble can observe, the field contains few bright celestial objects. Seemingly devoid of light, this small area provided a “keyhole” view of the universe’s past, reaching across space and time to see infant galaxies. By probing these remote regions of space, astronomers are gaining more information on galaxy development.
A tiny region of the southern sky near the Southern Cross toward which the Hubble Space Telescope was pointed for ten straight days in 1998. Because this observation was designed to detect very faint light from the most distant galaxies Hubble can observe, the field contains few bright celestial objects. Seemingly devoid of light, this small area provided a “keyhole” view of the universe’s past, reaching across space and time to see infant galaxies. By probing these remote regions of space, astronomers are gaining more information on galaxy development.
Mathematically expresses the idea that the recessional velocities of faraway galaxies are directly proportional to their distance from us. Hubble’s Law describes the relationship of velocity and distance by the equation V = Ho * d, where V is the object’s recessional velocity, d is the distance to the object, and Ho is the Hubble constant. Essentially, the more distant two galaxies are from each other, the faster they are traveling away from each other. American astronomer Edwin Hubble discovered this relationship in 1929 when he observed that galaxies and clusters of galaxies were generally moving away from each other.
An orbiting telescope that collects light from celestial objects in visible, near-ultraviolet, and near-infrared wavelengths. The telescope was launched April 24, 1990 aboard the NASA Space Shuttle Discovery. The 12.5-ton (11,110-kg), tube-shaped telescope is 13.1 m (43 ft) long and 4.3 m (14 ft) wide. It orbits the Earth every 96 minutes and is mainly powered by the sunlight collected by its two solar arrays. The telescopes primary mirror is 2.4 m (8 ft) wide. The telescope is operated jointly by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). HST is one of the many NASA Origins Missions, which include current satellites such as the Far Ultraviolet Space Explorer (FUSE) and future space observatories such as the James Webb Space Telescope (JWST).
A device capable of intensifying light from a faint source so that it may be more easily detected.
When one body strikes another with great force. Some examples include a meteor colliding with the Moon or a comet, such as Shoemaker-Levy 9, slamming into Jupiter.
A large depression on a moon or a planet. An impact crater is created when an asteroid, a comet, or a meteorite strikes the moon or the planet with great force.
A collision between two solar system bodies that releases exceptionally large amounts of energy. Some examples are the 1908 Siberian Tunguska impact by a comet or an asteroid and the asteroid that struck Earth 65 million years ago, which may have led to the extinction of the dinosaurs and other species of the Cretaceous-Tertiary era.
The part of the Deep Impact spacecraft that crashed into comet 9P/Tempel 1. When launched, the impactor and the flyby spacecraft were attached to each other. The spacecraft launched the impactor a day before the crash. As the impactor punched through the comet’s crust, the flyby craft recorded the event from a safe distance away.
The theory that the universe expanded very rapidly shortly after the Big Bang.
Radiation that has longer wavelengths and lower frequencies and energies than visible light.
The part of the electromagnetic spectrum that has slightly lower energy than visible light, but is not visible to the human eye. Just as there are low-pitched sounds that cannot be heard, there is low-energy light that cannot be seen. Infrared light can be detected as the heat from warm-blooded animals.
An instrument that collects the infrared radiation emitted by celestial objects. There are several Earth- and space-based infrared observatories. The Infrared Telescope Facility, an Earth-bound infrared telescope, is the U.S. national infrared observing facility at the summit of Mauna Kea, Hawaii. A planned space-based infrared observatory is the Space Infrared Telescope Facility (SIRTF).
Any device that measures and/or records energy from astronomical objects. Some astronomical instruments include spectrometers, photometers, spectroheliographs, and charge-coupled devices.
The amount, degree, or quantity of energy passing through a point per unit time. For example, the intensity of light that Earth receives from the Sun is far greater than that from any other star because the Sun is the closest star to us.
An instrument that combines the signal from two or more telescopes to produce a sharper image than the telescopes could achieve separately.
The process used to combine the signal from two or more telescopes to produce a sharper image than each telescope could achieve separately.
The longest operating (1978 – 1996) and most productive ultraviolet space observatory launched into a high geosynchronous orbit.
Dust, gas, and other debris found within the solar system.
The region of space surrounding our Sun. Asteroids, comets, Earth, and the solar wind are examples of things occupying interplanetary space.
Small particles of solid matter, similar to smoke, in the space between stars.
The sparse gas and dust located between the stars of a galaxy.
The dark regions of space located between the stars.
A law that describes any quantity, such as gravitational force, that decreases with the square of the distance between two objects. For example, if the distance between two objects is doubled, then the gravitational force exerted between them is one-fourth as strong. Likewise, if the distance to a star is doubled, then its apparent brightness is only one-fourth as great.
Radiation that the eye cannot detect, such as gamma rays, radio waves, ultraviolet light, and X-rays.
The innermost of Jupiter’s four large moons. Due to Jupiter’s gravitational might, Io is geologically active; its surface is peppered with volcanoes that send sulfurous eruptions into its thin atmosphere. Io appears to have the most active volcanoes in the solar system.
An atom with one or more electrons removed (or added), giving the atom a positive (or negative) charge.
The process by which ions are produced, typically by collisions with other atoms or electrons, or by absorption of electromagnetic radiation.
A region of the Earth’s upper atmosphere where solar radiation ionizes the air molecules. This region affects the transmission of radio wave and extends from 50 to 400 kilometers (30 to 250 miles) above the Earth's surface.
A bagel-shaped region of trapped sulfur ions around Jupiter that originates from the surface of Io, one of Jupiter’s moons. Gravitational tidal forces between Jupiter, other Galilean moons, and Io cause tidal friction in Io’s interior, producing geysers that spew sulfur at tremendous speeds. Some of the sulfur ions leave Io’s surface and become trapped around Jupiter.
A galaxy that appears disorganized and disordered, without a distinct spiral or elliptical shape. Irregular galaxies are usually rich in interstellar matter, such as dust and gas. The Large and Small Magellanic Clouds are examples of nearby irregular galaxies.
An atom of a given element having a particular number of neutrons in the nucleus. Isotopes of a given element differ in the numbers of neutrons within the nucleus. Adding or subtracting a neutron from the nucleus changes an atoms mass but does not affect its basic chemical properties.
Narrow, high-energy streams of gas and other particles generally ejected in two opposite directions from some central source. Jets appear to originate in the vicinity of an extremely dense object, such as a black hole, pulsar, or protostar, with a surrounding accretion disk. These jets are thought to be perpendicular to the plane of the accretion disk.
The atmosphere surrounding the giant, massive planet Jupiter. The Jovian atmosphere is composed primarily of hydrogen (90 percent) and helium (10 percent). Other minor ingredients include water, hydrogen sulfide, methane, and ammonia.
The planets Jupiter, Saturn, Uranus, and Neptune. They are called Jovian planets because of similarities in their composition and location. This group is also known as the “giant planets,” the “gas planets” and, when grouped with the planet Pluto, the “outer planets.”
The hurricane-force, high-velocity motion of gas molecules in Jupiter's atmosphere. The wind speed increases as one travels deeper into Jupiter's atmosphere. The various patterns of atmospheric winds are easily identified in Jupiter's upper cloud layer.
The fifth planet from the Sun and the largest planet in our solar system, twice as massive as all the other planets combined. Jupiter is a gaseous planet with a very faint ring system. Four large moons and numerous smaller moons orbit the planet. Jupiter is more than five times the Earth’s distance from the Sun. It completes an orbit around the Sun in about 12 Earth years.
Two telescopes known as the world's largest optical and infrared telescopes, jointly operated by the California Institute of Technology and the University of California. The telescopes comprise the W.M. Keck Observatory and are located on the summit of Hawaii’s dormant Mauna Kea volcano.
The temperature scale most commonly used in science, on which absolute zero is the lowest possible value. On this scale, water freezes at 273 K and boils at 373 K.
Three laws, derived by 17th century German astronomer Johannes Kepler, that describe planetary motion.
A measure of distance in the metric system equal to 1000 meters or about 0.6 of a mile.
The energy that an object has by virtue of its motion.
The world’s largest collection of telescopes, located high above the Sonora Desert in Arizona. Eight astronomical research institutions share the 22 optical and two radio telescopes at Kitt Peak. The National Optical Astronomy Observatories oversee site operations at the observatory.
A region in our outer solar system where many short-period comets originate. The orbits of short-period comets are less than 200 years. This region begins near Neptune's orbit at 30 astronomical units (AU) and extends to about 50 AU away from the Sun. An astronomical unit is the average distance between Earth and the Sun. The Kuiper Belt may have as many as 100 million comets.
A carefully ground or molded piece of glass, plastic, or other transparent material that causes light to bend and either come together or spread apart to form an image.
A set of two lenses, one concave and one convex, made from different types of glass. Together the lenses correct both spherical and chromatic aberrations. A single lens alone cannot correct these aberrations.
A plot showing how the light output of a star (or other variable astronomical object) changes with time.
The distance that a particle of light (photon) will travel in a year – about 10 trillion kilometers (6 trillion miles). It is a useful unit for measuring distances between stars.
The solid part of a planet's surface, composed of the crust and upper mantle. On Earth, it includes the continents and the sea floor.
A small cluster of more than 30 galaxies, including the Andromeda galaxy, the Magellanic Clouds, and the Milky Way galaxy.
A comet having an orbital period greater than 200 years and usually moving in a highly elliptical, eccentric orbit. Comets have orbits that take them great distances from the Sun. Most long-period comets pass through the inner solar system only once. Hale-Bopp is an example of a long-period comet.
The amount of energy radiated into space every second by a celestial object, such as a star. It is closely related to the absolute brightness of a celestial object.
A darkening of the Moon, as viewed from Earth, caused when our planet passes between the Sun and the Moon.
A specific wavelength (91.2 nm) that corresponds to the energy needed to ionize a hydrogen atom (13.6 eV). Galactic space is opaque at wavelengths shorter than the Lyman limit. Subsequently, light from cosmic objects at wavelengths less than the Lyman limit is exceedingly difficult to detect.
Two dwarf irregular galaxies known as the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The galaxies are in the Local Group. The closer LMC is 168,000 light-years from Earth. Both galaxies can be observed with the naked eye in the southern night sky.
A region of space in which magnetic forces may be detected or may affect the motion of an electrically charged particle. As with gravity, magnetism has a long-range effect and magnetic fields are associated with many astronomical objects.
Imaginary lines used to visualize a magnetic field. Magnetic field lines are related to the strength of the magnetic object’s influence and point in the same direction as a compass needle would.
A region of space above the Earth’s (or other planet’s) atmosphere where magnetic fields influence the motions of charged particles. The magnetosphere magnetically deflects or traps charged particles from space that would otherwise bombard the planet’s surface.
Enlargement in the size of an optical image. For telescopes, magnification is not as important as the ability to gather light, which depends on the diameter of the primary lens or mirror.
The process of enlarging the size of an optical image.
The interior region of a terrestrial (rocky) planet or other solid body that is below the crust and above the core.
A dark, flat, large region on the surface of the Moon. The term is also applied to the less well-defined areas on Mars. Although maria literally means “seas,” watery regions do not exist on the Moon or Mars. Marias on the Moon may be evidence of past volcanic lava flows.
The fourth planet in the solar system and the last member of the hard, rocky planets (the inner or terrestrial planets) that orbit close to the Sun. The planet has a thin atmosphere, volcanoes, and numerous valleys. Mars has two moons: Deimos and Phobos.
NASA center overseeing the research, development, and implementation of three primary areas essential to space flight: reusable space transportation systems, generation and communication of new scientific knowledge, and management of all space lab activities. Located in Huntsville, Alabama, the center aided in the design, development, and construction of the Hubble Space Telescope.
A measure of the total amount of matter contained within an object.
A highly efficient energy-generation process in which equal amounts of matter and antimatter collide and destroy each other, thus producing a burst of energy.
Equals one million parsecs (3.26 million light-years) and is the unit of distance commonly used to measure the distance between galaxies.
The closest planet to the Sun. The temperature range on Mercury’s surface is the most extreme in the solar system, ranging from about 400C (750°F) during the day to about – 200°C (-300°F) at night. Mercury, which looks like Earth’s moon, has virtually no atmosphere, no moons, and no water.
A bright streak of light in the sky caused when a meteoroid enters the Earth’s atmosphere. The streak of light is produced from heat generated by the meteoroid traveling into the Earth’s atmosphere.
The remains of a meteoroid that plunges to the Earth’s surface. A meteorite is a stony or metallic mass of matter that did not completely vaporize when it entered the Earth’s atmosphere.
A small, solid object moving through space. A meteoroid produces a meteor when it enters the Earth’s atmosphere.
A chemical compound consisting of five atoms: one of carbon and four of hydrogen. On Earth, methane is a colorless, odorless gas and is the principal ingredient of natural gas. In the cold vacuum of space, methane is a white solid but, when hit by sunlight, it can become a gas.
A very small meteoroid with a diameter of less than a millimeter. Micrometeoroids form the bulk of the interplanetary solid matter scattered throughout the solar system.
An electromagnetic wave in the region between infrared and radio wavelengths. Microwave wavelengths fall between one millimeter and one meter.
The Milky Way, a spiral galaxy, is the home of Earth. The Milky Way contains more than 100 billion stars and has a diameter of 100,000 light-years.
The building blocks of rocks. They are naturally occurring substances formed through geological processes, and often have a crystalline form. They can be single elements (such as gold or silver) or compounds (such as quartz, marble or turquoise).
A group of several theories developed in the early to mid-20th century that explains how small particles are affected by light, how measurements change when objects move very fast, and how gravity affects space and time.
A relatively dense, cold region of interstellar matter where hydrogen gas is primarily in molecular form. Stars generally form in molecular clouds. Molecular clouds appear as dark blotches in the sky because they block all the light behind them.
The average speed of the molecules in a gas of a given temperature.
A tightly knit group of two or more atoms bound together by electromagnetic forces among the atoms’ electrons and nuclei. For example, water (H2O) is two hydrogen atoms bound with one oxygen atom. Identical molecules have identical chemical properties.
A large body orbiting a planet. On Earth’s only moon, scientists have not detected life, water, or oxygen on this heavily cratered body. The Moon orbits our planet in about 28 days.
The support structure for a telescope that bears the weight of the telescope and allows it to be pointed at a target. The mounting of today’s research telescopes also allows astronomers to track the object as it appears to move across the sky.
A skin or blanket of insulation covering the Hubble Space Telescope, which protects the observatory from temperature extremes. This insulation protects the telescope from the cold of outer space and also reflects sunlight so that the telescope does not become too warm. The MLI on Hubble is made up of many layers of aluminized Kapton, with an outer layer of aluminized Teflon.
A Federal agency created on July 29, 1958 after President Dwight Eisenhower signed the National Aeronautics and Space Act of 1958. NASA coordinates space exploration efforts as well as traditional aeronautical research functions.
The region of the infrared spectrum that is closest to visible light. Near-infrared light has slightly longer wavelengths and slightly lower frequencies and energies than visible light.
An instrument that sees objects in near-infrared wavelengths, which are slightly longer than the wavelengths of visible light. (Human eyes cannot see infrared light.) NICMOS is actually three cameras in one, each with different fields of view. Many secrets about the birth of stars, solar systems, and galaxies are revealed in infrared light, which can penetrate the interstellar gas and dust that blocks visible light. In addition, light from the most distant objects in the universe shifts into infrared wavelengths due to the universes expansion. By studying objects and phenomena in this spectral region, astronomers probe our universes past, present, and future; and learn how galaxies, stars, and planetary systems form. Astronauts installed NICMOS aboard the Hubble Space Telescope in February 1997 during the Second Servicing Mission.
A cloud of gas and dust located between stars and/or surrounding stars. Nebulae are often places where stars form.
The idea that our solar system originated in a contracting, rotating cloud of gas that flattened to form a disk as it contracted. According to this theory, the Sun formed at the center of the disk and the planets formed in concentric bands of the disk.
The eighth planet and the most distant giant gaseous planet in our solar system. The planet is 30 times the Earth’s distance from the Sun, and each orbit takes 165 Earth years. Neptune is the fourth largest planet and has at least eight moons, the largest of which is Triton. Neptune has a ring system, just like all the giant gaseous outer planets.
A neutral, weakly interacting elementary particle having a very tiny mass. Stars like the Sun produce more than 200 trillion trillion trillion neutrinos every second. Neutrinos from the Sun interact so weakly with other matter that they pass straight through the Earth as if it weren’t there.
A device designed to detect neutrinos.
A neutral (no electric charge) elementary particle having slightly more mass than a proton and residing in the nucleus of all atoms other than hydrogen.
An extremely compact ball of neutrons created from the central core of a star that collapsed under gravity during a supernova explosion. Neutron stars are extremely dense: they are only 10 kilometers or so in size, but have the mass of an average star (usually about 1.5 times more massive than our Sun). A neutron star that regularly emits pulses of radiation is known as a pulsar.
Covers that protect Hubbles damaged external blankets and help to maintain the telescopes normal operating temperatures. The covers are made of specially coated stainless steel foil, which is trimmed to fit each particular equipment bay door.
A type of reflecting telescope whose eyepiece is located along the side of the telescope. When light enters the telescope, it reflects from the primary mirror to the secondary mirror. The secondary mirror reflects the light at a right angle through the side of the telescope to the eyepiece.
Radiation that is not produced from heat energy – for example, radiation released when a very fast-moving charged particle (such as an electron) interacts with a magnetic force field. Because the electron’s velocity in this case is not related to the gas temperature, this process has nothing to do with heat.
A direction determined by the projection of the Earth’s North Pole onto the celestial sphere. It corresponds to a declination of +90 degrees. The North Star, Polaris, sits roughly at the NCP.
Half of a spherical or roughly spherical body; for example, the Northern Hemisphere of Earth is the half above the equator.
A binary star system (consisting of a white dwarf and a companion star) that rapidly brightens, then slowly fades back to normal.
The process by which an atomic nucleus is transformed into another type of atomic nucleus. For example, by removing an alpha particle from the nucleus, the element radium is transformed into the element radon.
The core of a comet, made up of ice, dirt, and rock.
The portion of the entire universe that can be seen from Earth.
In science, an observation is a fact or occurrence that is noted and recorded. The Hubble Space Telescope is a tool astronomers use to make observations of celestial objects.
A structure designed and equipped for making astronomical observations. Observatories are located on Earth and in space.
A vast spherical region in the outer reaches of our solar system where a trillion long-period comets (those with orbital periods greater than 200 years) reside. Comets from the Oort Cloud come from all directions, often from as far away as 50,000 astronomical units.
The degree to which light is prevented from passing through an object or a substance. Opacity is the opposite of transparency. As an object’s opacity increases, the amount of light passing through it decreases. Glass, for example, is transparent and most clouds are opaque.
Also known as a galactic cluster, an open cluster consists of numerous young stars that formed at the same time within a large cloud of interstellar dust and gas. Open clusters are located in the spiral arms or the disks of galaxies. The Pleiades is an example of an open cluster.
A geometrical model of the universe in which the overall structure of the universe extends infinitely in all directions. The rules of geometry in an open universe are like those that would apply on a saddle-shaped surface.
The point at which a planet appears opposite the Sun in our sky. During the Martian opposition, for example, Mars and the Sun are on opposite sides of the Earth.
A telescope that gathers and magnifies visible light. The two basic types of optical telescopes are refracting (using lenses) and reflecting (using mirrors). The Hubble Space Telescope is an example of a reflecting telescope.
A person who grinds lenses and mirrors.
The science that deals with the properties of light; in this case specifically dealing with the way light changes directions when it is either refracted and dispersed by a lens or reflected from a mirror.
The act of traveling around a celestial body; or the path followed by an object moving around a celestial body. For example, the planets travel around, or orbit, the Sun because the Sun’s gravity keeps them in their paths, or orbits.
A region in the upper atmosphere that has high concentrations of ozone (triatomic oxygen, 03). The ozone layer protects the Earth by absorbing the Sun’s high-energy ultraviolet radiation.
If cross-sections of a spherical surface and a parabolic surface were made by slicing each surface in half, these would be the shapes you would see.
The apparent shift of an object’s position when viewed from different locations. Parallax, also called trigonometric parallax, is used to determine the distance to nearby stars. As the Earth’s position changes during its yearly orbit around the Sun, the apparent locations of nearby stars slightly shift. The stars' distances can be calculated from those slight shifts with basic trigonometric methods.
A useful unit for measuring the distances between astronomical objects, equal to 3.26 light-years and 3.085678 * 1013kilometers, or approximately 18 trillion miles. A parsec is also equivalent to 103,132 trips to the Sun and back.
The perfect lens does not exist. Due to the nature of glass, light is dispersed when passing through glass. In the case of convex lenses, red light bends less than blue light, so the focal points are in different places, making the image blurry. A single lens cannot counter this effect.
A comet in a closed, elliptical orbit within our solar system. These comets typically have orbital periods of less than 200 years. Many comets have orbits that keep them in the inner solar system and allow their trajectories to be calculated with great accuracy and precision. Perhaps the best-known periodic comet is Halley’s comet, whose orbital period is 76 years.
A chart of all the known chemical elements arranged according to the number of protons in the nucleus (also known as the atomic number). Elements with similar properties are grouped together in the same column.
A relationship that describes how the luminosity or absolute brightness of a Cepheid variable star depends on the period of time over which that brightness varies.
Regularly occurring changes in the appearance of the Moon or a planet. Phases of the Moon include new, full, crescent, first quarter, gibbous, and third quarter.
The release of electrons from a solid material when it is struck by radiant energy, such as visible or ultraviolet light, X-rays, or gamma rays.
An instrument that measures the intensity of light. Astronomers use photometers to measure the brightness of celestial objects.
A technique for measuring the brightness of celestial objects.
A packet of electromagnetic energy, such as light. A photon is regarded as a charge-less, mass-less particle having an indefinitely long lifetime.
The extremely thin, visible surface layer of the Sun or a star. The average temperature of the Sun’s photosphere is about 5800 Kelvin (about 10,000°F). Although the Sun is completely made up of gas, its gas is so dense that we cannot see through it. When we look at the Sun, we are seeing the photosphere.
One of four flat mirrors inside the Hubble Space Telescope. Each mirror is tilted at a 45-degree angle to the incoming light, diverting a small portion of it to the optical detectors or to one of the fine guidance sensors.
A light-sensitive picture element on a charge-coupled device (CCD) or some other kind of digital camera. A pixel is a tiny cell that, placed together with other pixels, resembles the mesh on a screen door. The Hubble Space Telescopes Wide Field and Planetary Camera2 has four CCDs, each containing 640,000 pixels. Each pixel collects light from a celestial object and converts it into a number. The numbers (all 2,560,000 of them) are sent to ground-based computers, which convert them into an image. The greater number of pixels, the sharper the image.
The graphical representation of the mathematical relationship between the frequency (or wavelength) and intensity of radiation emitted from an object by virtue of its heat energy.
An object that orbits a star. Although smaller than stars, planets are relatively large and shine only by reflected light. Planets are made up mostly of rock or gas, with a small, solid core. In our solar system, the inner planets "Mercury, Venus, Earth, and Mars" are the rocky objects, and most of the outer planets – Jupiter, Saturn, Uranus, and Neptune – are the gaseous ones. Because Pluto is made largely of ice, like a comet, some astronomers do not consider it a true planet.
An expanding shell of glowing gas expelled by a star late in its life. Our Sun will create a planetary nebula at the end of its life.
A small body of rock and/or ice – under 10 kilometers (6 miles) across – formed during the early stages of the solar system. Planetesimals are the building blocks of planets, but many never combined to form large bodies. Asteroids are one example of planetesimals.
A substance composed of charged particles, like ions and electrons, and possibly some neutral particles. Our Sun is made of plasma. Overall, the charge of a plasma is electrically neutral. Plasma is regarded as an additional state of matter because its properties are different from those of solids, liquids, and normal gases.
A column of material that is shaped like a long feather.
A dwarf planet whose small size and composition of ice and rock resembles the comets in the Kuiper Belt, a region beyond Neptunes orbit where Pluto resides. Pluto was considered the ninth planet until August 2006, when the International Astronomical Union reclassified it as a dwarf planet. Plutos orbit is more elliptical than those of the eight solar system planets.
The energy of an object owing to its position in a force field or its internal condition, as opposed to kinetic energy, which depends on its motion. Examples of objects with potential energy include a diver on a diving board and a coiled spring.
A large convex lens in a refracting telescope that captures light from celestial objects and focuses it toward the eyepiece.
A large mirror in a reflecting telescope that captures light from celestial objects and focuses it toward a smaller secondary mirror. The primary mirror in the Hubble Space Telescope measures 94.5 inches (2.4 meters) in diameter.
The location where light reflected from the primary mirror of a reflecting telescope comes into focus. Placing a secondary mirror in the light path allows the light to be focused elsewhere, in a more convenient location for the science instruments.
Element building that occurred in the early universe when the nuclei of primordial matter collided and fused with one another. Most of the helium in the universe was created by this process.
Usually a triangular-shaped piece of glass used to refract, or bend, light. The shape of the glass causes the light to disperse, or spread out, as it bends, producing a rainbow of colors from the white light.
An eruption of gas from the chromosphere of a star. Solar prominences are visible as part of the corona during a total solar eclipse. These eruptions occur above the Sun’s surface (photosphere), where gases are suspended in a loop, apparently by magnetic forces that arch upward into the solar corona and then return to the surface.
The apparent motion of a star across the sky (not including a star’s parallax), arising from the star’s velocity through space with respect to the Sun.
Matter that is beginning to come together to form a galaxy. It is the precursor of a present-day galaxy and is sometimes called a “baby galaxy.”
A positively charged elementary particle that resides in the nucleus of every atom.
A series of nuclear events occurring in the core of a star whereby hydrogen nuclei (protons) are converted into helium nuclei. This process releases energy.
A small body that attracts gas and dust as it orbits a young star. Eventually, it may form a planetary body.
A collection of interstellar gas and dust whose gravitational pull is causing it to collapse on itself and form a star.
A neutron star that emits rapid and periodic pulses of radiation.
A basic building block of protons, neutrons, and other elementary particles.
The brightest type of active galactic nucleus, believed to be powered by a supermassive black hole. The word “quasar” is derived from quasi-stellar radio source, because this type of object was first identified as a kind of radio source. Quasars also are called quasi-stellar objects (QSOs). Thousands of quasars have been observed, all at extreme distances from our galaxy.
A method of detecting, locating, or tracking an object by using beamed, reflected, and timed radio waves. RADAR also refers to the electronic equipment that uses radio waves to detect, locate, and track objects.
The component of an object’s velocity (speed and direction) as measured along an observer's line of sight.
The process by which electromagnetic energy moves through space as vibrations in electric and magnetic fields. This term also refers to radiant energy and other forms of electromagnetic radiation, such as gamma rays and X-rays.
An event involving the emission or absorption of radiation. For example, a hydrogen atom that absorbs a photon of light converts the energy of that radiation into electrical potential energy.
The spontaneous decay of certain rare, unstable, atomic nuclei into more stable atomic nuclei. A natural by-product of this process is the release of energy.
The part of the electromagnetic spectrum with the lowest energy. Radio waves are the easiest way to communicate information through the atmosphere or outer space.
Boxes that house Hubbles gyroscopes. Each rate sensor unit contains two gyroscopes. Astronauts remove the rate sensor units when they replace gyroscopes, so gyroscopes are always replaced two at a time.
One of four spinning flywheels aboard the Hubble Space Telescope. The flywheels work together to make the observatory rotate either more rapidly or less rapidly toward a new target.
The part of the radio telescope that detects long wavelength electromagnetic radiation and converts it to an electrical signal so that we can sense it.
The velocity at which an object moves away from an observer. The recessional velocity of a distant galaxy is proportional to its distance from Earth. Therefore, the greater the recessional velocity, the more distant the object.
An old, bright star, much larger and cooler than the Sun. Betelgeuse (alpha Orionis) is an example of a red giant.
The lengthening of a light wave from an object that is moving away from an observer. For example, when a galaxy is traveling away from Earth, its light shifts to the red end of the electromagnetic spectrum.
Reflection occurs when light changes direction as a result of "bouncing off" a surface like a mirror.
A type of telescope, also known as a reflecting telescope, that uses one or more polished, curved mirrors to gather light and reflect it to a focal point.
Refraction is the bending of light as it passes from one substance to another. Here, the light ray passes from air to glass and back to air. The bending is caused by the differences in density between the two substances.
A type of telescope that uses a transparent convex lens to gather light and bend it to a focal point.
The layer of loose rock resting on bedrock (sometimes called mantle rock), found on the Earth, the Moon, or a planet. Regolith is made up of soils, sediments, weathered rock, and hard, near-surface crusts. On the surface of the Moon, regolith is a fine rocky layer of fragmentary debris (or dust) produced mainly by meteoroid collisions.
A theory of physics that describes the dynamical behavior of matter and energy. The consequences of relativity can be quite strange at very high velocities and very high densities. A direct result of the theory of relativity is the equation E=mc2, which expresses a relationship between mass (m), energy (E), and the speed of light(c).
A measure of the smallest separation at which a telescope can observe two neighboring objects as two separate objects.
The ability of a telescope to distinguish objects that are very close to each other as two separate objects.
The orbital motion of one object around another. The Earth revolves around the Sun in one year. The moon revolves around the Earth in approximately 28 days.
A coordinate used by astronomers to locate stars and other celestial objects in the sky. Right ascension is comparable to longitude, but it is measured in hours, minutes, and seconds because the entire sky appears to pass overhead over a period of 24 hours. The zero hour corresponds to the apparent location of the Sun with respect to the stars on the day of the vernal (spring) equinox (approximately March 21).
A long, narrow depression on the Moon’s surface. A rille can be straight, have a sweeping arc, or meander, with many curves going in random directions.
A terrestrial telescope that searches for the optical counterparts of gamma-ray bursts. When orbiting satellites detect a gamma-ray burst, ROTSE begins searching for its visible-light afterglow. ROTSE-I (an array of four electronic telephoto cameras) and ROTSE-II (a set of identical telescopes) are located in Los Alamos, New Mexico.
The smallest distance at which two celestial bodies can remain in a stable orbit around each other without one of them being torn apart by tidal forces. The distance depends on the densities of the two bodies and their orbit around each other.
A planet located in the inner solar system and made up mostly of rock. The rocky planets are Mercury, Venus, Earth, and Mars. This group is also known as terrestrial planets.
The spin of an object around its central axis. Earth rotates about its axis every 24 hours. A spinning top rotates about its center shaft.
A man-made object that orbits Earth, the Moon, or another celestial object.
The sixth planet in the solar system, noted for its obvious ring structure. Saturn is almost ten times the Earth’s distance from the Sun. The planet completes a circuit around the Sun in about 30 Earth years. Saturn is the second largest and the least dense planet in our solar system. The planet has more than 21 moons, including Titan, the second largest known moon in our solar system.
The distance from the ‘center’ of a black hole to its ‘edge’ (called an event horizon). If the Earth became a black hole, all of its mass would be squeezed into a sphere with a Schwarzschild radius of 0.03 cm, about the size of a bacterium.
A flash of light produced when gamma rays strike a certain material. The high energy of gamma rays makes them hard to capture but they can be detected using scintillation.
A gas or gases, such as helium, that a planet discharges from its interior after having lost its primary or primordial atmosphere.
A small mirror in a reflecting telescope that redirects light from the larger primary mirror toward the light-sensitive scientific instruments. In a Cassegrain-type telescope like the Hubble Space Telescope, the secondary mirror is slightly convex and directs light from the primary mirror back through a hole in the center of the primary mirror.
The transfer of energy throughout a celestial object, such as a planet, resulting from an external impact or an internal event. On Earth, seismic waves are generated primarily by earthquakes.
Hubble was the first space telescope designed to be serviced in space. Scientists believed that periodic servicing missions would extend Hubble's operating life and keep the observatory up-to-date. Astronauts have visited Hubble five times. The first servicing mission was in December 1993 and the second in February 1997. The third mission was split into two visits. Part A took place in December 1999 and part B in March 2002. The final servicing mission visit occurred in May 2009.
A galaxy characterized by a moderately bright, compact active galactic nucleus, presumably powered by a black hole.
A high-pressure wave that travels at supersonic speeds. Shock waves are usually produced by an explosion.
A comet that orbits mainly in the inner solar system. Short-period comets usually orbit the Sun in less than 200 years. Halley’s comet is an example of a short-period comet.
A black hole’s center, where the matter is thought to be infinitely dense, the volume is infinitely small, and the force of gravity is infinitely large.
When Hubble reaches the end of its mission, NASA must be able to safely return the telescope to Earth. When that time comes, the space shuttle will no longer be operating, so another means of capturing the telescope must be available. The soft capture mechanism is a compact device that, when attached to the Hubble Space Telescope, will assist in its safe de-orbit. This device has structures and targets that will allow a next generation space vehicle to more easily capture and guide the telescope into a safe, controlled re-entry.
Two rigid, wing-like arrays of solar panels that convert sunlight directly into electricity to operate the Hubble Space Telescopes scientific instruments, computers, and radio transmitters. Some of the energy generated is stored in onboard batteries so the telescope can operate while in Earths shadow (which is about 36 minutes out of each 97-minute orbit). The solar arrays are designed for replacement by visiting astronauts during servicing missions.
The average amount of solar radiation reaching a planet; usually expressed in watts (energy per unit time) per square meter. For Earth, the solar constant equals 1,372W/m2. Each planet has a unique solar constant depending on its distance from the Sun.
The periodic changing of the Sun’s magnetic field, which determines the number of sunspots and the amount of particles emitted in the solar wind. The period of the cycle is about 11 years.
A phenomenon in which the Moon’s disk passes in front of the Sun, blocking sunlight. A total eclipse occurs when the Moon completely obscures the Sun's disk, leaving only the solar corona visible. A solar eclipse can only occur during a new phase of the Moon.
The midpoint in the solar cycle where the amount of sunspot activity and the output of cosmic particles and solar radiation is highest.
The beginning and the end of a sunspot cycle when only a few sunspots are usually observed, and the output of particles and radiation is normal.
Two rigid, wing-like structures that convert sunlight directly into electricity to operate a space telescope’s scientific instruments, computers, and radio transmitters. Some of the energy generated is stored in onboard batteries so the telescope can operate while in Earth’s shadow.
The Sun and its surrounding matter, including asteroids, comets, planets and moons, held together by the Sun’s gravitational influence.
A special reflecting telescope designed to study our closest star, the Sun. Solar telescopes differ from normal telescopes in that they are stationary and use small tracking mirrors to direct sunlight into the primary mirror. This is necessary because the Sun appears to move across the sky due to Earth’s rotation.
Streams of charged particles flowing from the Sun at millions of kilometers an hour. The composition of this high-speed solar wind may vary, but it always streams away from the Sun. The solar wind is responsible for the Northern and Southern Lights on Earth and causes the tails of comets to point away from the Sun.
A direction determined by the projection of the Earth’s South Pole onto the celestial sphere. The SCP is exactly 180 degrees from the North Celestial Pole and corresponds to a declination of -90 degrees.
Half of a spherical or roughly spherical body; for example, the Southern Hemisphere of Earth is the half below the equator.
A space-borne infrared telescope that will study planets, comets, stars, galaxies, and other celestial objects. NASA plans to launch SIRTF in December 2002 on a Delta rocket. SIRTF represents the fourth and final satellite in NASA’s Great Observatories program, which includes the Hubble Space Telescope and the Chandra X-Ray Observatory.
A reusable U.S. spacecraft operated by astronauts and used to transport cargo, such as satellites, into space. The spacecraft used rockets to launch into space, but it landed like an airplane. A space shuttle carried the Hubble Space Telescope into space in 1990. Astronauts aboard subsequent space shuttles had visited the telescope to service it. The space shuttle was retired in 2011.
The Space Telescope Imaging Spectrograph (STIS) is a general-purpose spectrograph that spans ultraviolet, visible, and near-infrared wavelengths. It was installed in February 1997 during the Second Servicing Mission. A spectrograph works by breaking up light from an object into its individual wavelengths so that its composition, temperature, motion, and other chemical and physical properties can be analyzed. STIS stopped functioning in 2004 due to a power supply failure, but astronauts replaced a low-voltage power supply board during Servicing Mission 4.
The astronomical research center responsible for operating the Hubble Space Telescope as an international scientific observatory. Located in Baltimore, Maryland, STScI is managed by AURA (Association of Universities for Research in Astronomy) under contract to the National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF). STScI will conduct the science and mission operations for the James Webb Space Telescope and supports other astronomy programs.
The four-dimensional coordinate system (three dimensions of space and one of time) in which physical events are located.
A classification scheme that groups stars according to their surface temperatures and spectral features.
In a spectrum, an emission (bright) or absorption (dark) at a specific frequency or wavelength.
An instrument that spreads electromagnetic radiation into its component frequencies and wavelengths for detailed study. A spectrograph is similar to a prism, which spreads white light into a continuous rainbow.
An instrument used in solar telescopes to photograph the Sun in a single wavelength of light. Different wavelengths reveal different features of the Sun’s surface.
The study and interpretation of a celestial object’s electromagnetic spectrum. A spectrograph or spectrometer is used to analyze an object’s electromagnetic spectrum.
The entire range of electromagnetic rays from the longest radio waves to the shortest gamma rays. Arranged from longest to shortest wavelengths, the spectrum of electromagnetic radiation includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays and gamma rays.
The speed at which light (photons) travels through empty space is roughly 3 * 108 meters per second or 300 million meters per second.
Spherical aberration is an optical defect of a lens or mirror caused by its rounded shape. Spherical lenses and mirrors produce a distorted (blurry) image.
The shape of a spherical lens causes a problem called spherical aberration.
In spherical aberration, parallel light rays that pass through the central region of the lens focus farther away than light rays that pass through the edges of the lens. The result is many focal points, which produce a blurry image. To get a clear image, all rays need to focus at the same point.
The shape of a spherical telescope mirror causes a problem called spherical aberration.
In spherical aberration, parallel light rays that bounce off the central region of a spherical mirror focus farther away than light rays that bounce off the edges. The result is many focal points, which produce a blurry image. To get a clear image, all rays need to focus at the same point.
A pinwheel structure, composed of dust, gas, and young stars, that winds its way out from the core of a normal spiral galaxy and from the ends of the bar in a barred spiral galaxy.
A spiral-shaped system of stars, dust, and gas clouds. A typical spiral galaxy has a spherical central bulge of older stars surrounded by a flattened galactic disk that contains a spiral pattern of young, hot stars, as well as interstellar matter.
Gamma-ray flashes produced in Earth's atmosphere by severe lightning storms and upper atmospheric events.
An object whose properties allow us to measure large distances through space. The absolute brightness of a standard candle can be determined without a measurement of its apparent brightness. Comparing the absolute brightness of a standard candle to its apparent brightness therefore allows us to measure its distance. For example, the distinct variations of Cepheid variable stars in other galaxies tell us their absolute brightness. By accurately measuring the apparent brightness of these stars, astronomers can precisely determine the distance to the galaxy in which they reside.
A huge ball of gas held together by gravity. The central core of a star is extremely hot and produces energy. Some of this energy is released as visible light, which makes the star glow. Stars come in different sizes, colors, and temperatures. Our Sun, the center of our solar system, is a yellow star of average temperature and size.
A galaxy undergoing an extremely high rate of star formation. Starburst galaxies contain massive, deeply embedded stars that are among the youngest stars observed.
A group of stars born at almost the same time and place, capable of remaining together for billions of years because of their mutual gravitational attraction.
Random noise in a radio receiver. It can also be heard in telephone lines and cell phones.
A black hole formed from the death of a massive star during a supernova explosion. A stellar black hole, much like a supermassive black hole, feeds off of nearby material – in this case, the dead star. As it gains mass, its gravitational field increases.
The process of change that occurs during a star’s lifetime from its birth to its death.
A region in space where stars are forming from a cloud of gas and dust.
The apparent change in the position of a nearby star when observed from Earth due to our planet’s yearly orbit around the Sun. This method allows astronomers to calculate distances to stars that are less than 100 parsecs from Earth.
The force that binds protons and neutrons within atomic nuclei and is effective only at distances less than 10-13 centimeters.
The star at the center of our solar system. An average star in terms of size and mass, the Sun is a yellow dwarf of spectral type G2. It is about 5 billion years old, contains 2 * 1030 kilograms of material, and has a diameter more than 100 times that of Earth.
A region on the Sun’s photosphere that is cooler and darker than the surrounding material. Sunspots often appear in pairs or groups with specific magnetic polarities that indicate electromagnetic origins.
The change in strength of the Sun’s magnetic field, which determines the number of sunspots and the amount of particles emitted in the solar wind. The period of the cycle is about 11 years.
A black hole possessing as much mass as a million or a billion stars. Supermassive black holes reside in the centers of galaxies and are the engines that power active galactic nuclei and quasars.
The explosive death of a massive star whose energy output causes its expanding gases to glow brightly for weeks or months. A supernova remnant is the glowing, expanding gaseous remains of a supernova explosion.
The glowing, expanding gaseous remains of a supernova explosion.
A tail is made up of dust and gas from a comet’s coma. A tail forms when the solar wind separates dust and gas from the coma, pushing it outward and away from the Sun in either a slightly curved path (for dust) or a straight path (for gas).
An instrument used to observe distant objects by collecting and focusing their electromagnetic radiation. Telescopes are usually designed to collect light in a specific wavelength range. Examples include optical telescopes that observe visible light and radio telescopes that detect radio waves.
A measure of the amount of heat energy in a substance, such as air, a star, or the human body. Because heat energy corresponds to motions and vibrations of molecules, temperature provides information about the amount of molecular motion occurring in a substance.
A measure of computer data storage capacity equal to approximately a thousand billion bytes (or a thousand gigabytes). In computer language, a byte of information represents a letter or digit. So, a thousand billion bytes is equal to a thousand billion letters.
Planets whose density and chemical makeup are similar to those of Earth.
The four planets of the inner solar system (Mercury, Venus, Earth, and Mars) are called terrestrial planets because they are made up mostly of rock.
An accepted idea used to explain nature. Theories not only explain an observed event, they can also be used to predict what will happen. Sometimes, an idea that is really a hypothesis is incorrectly called a theory. A true scientific theory is a hypothesis that makes predictions. Those predictions have been tested and have proven to be accurate.
Radiation released by virtue of an object's heat, namely, the transfer of heat energy into the radiative energy of electromagnetic waves. Examples of thermal radiation are sunlight, the orange glow of an electric range, and the light from in incandescent light bulb.
Minerals composed of oxygen and the metal titanium. Titanium oxides frequently contain other metals. One such titanium oxide is the mineral ilmenite, which contains titanium, oxygen, and iron. Ilmenite is found in both lunar rock and Earth rocks.
A network of four communication satellites used to relay data and commands to and from U.S. spacecraft, including the Hubble Space Telescope. The Goddard Space Flight Center provides the day-to-day management and operations of TDRSS, the first space-based global tracking system.
The largest of Neptune’s satellites. Triton has an atmosphere and is roughly the size of Earth’s moon. It has an “ice cap” of frozen nitrogen and methane with “ice volcanoes” that erupt liquid nitrogen, dust, and methane compounds from beneath its frozen surface.
A class of very young, flaring stars on the verge of becoming normal stars fueled by nuclear fusion.
Unstable and disorderly motion, as when a smooth, flowing stream becomes a churning rapid.
Electromagnetic radiation with shorter wavelengths and higher energies and frequencies than visible light. UV light is lower in frequency than X-rays.
The part of the electromagnetic spectrum that has slightly higher energy than visible light, but is not visible to the human eye. Just as there are high-pitched sounds that cannot be heard, there is high-energy light that cannot be seen. Too much exposure to ultraviolet light causes sunburns.
The totality of space and time, along with all the matter and energy in it. Current theories assert that the universe is expanding and that all its matter and energy was created during the Big Bang.
The third largest planet in the solar system and the seventh from the Sun. Uranus is 19 times the Earth’s distance from the Sun and completes a circuit around the Sun in about 84 Earth years. This gaseous, giant outer planet has a visible ring system and over 20 moons, the largest of which is Titania. Uranus is tipped on its side, with a rotation axis in nearly the same plane as its orbit.
A region containing charged particles trapped in the Earth’s magnetic force field (magnetosphere). The belt’s lower boundary begins at about 800 kilometers (496 miles) above the Earth’s surface and extends thousands of kilometers into space.
A star whose luminosity (brightness) changes with time.
Launched by the U.S. in the 1960s to monitor the Limited Nuclear Test Ban Treaty. The satellite's mission was to detect the gamma rays produced during nuclear blasts. Although not intended for astronomical studies, the Vela satellite provided useful celestial data, detecting an unexpected blast of cosmic gamma radiation in 1967. The satellite discovered several other gamma-rays bursts during the years of the Vela project, which ceased operation in 1979.
The speed of an object moving in a specific direction. A car traveling at 35 miles per hour is a measurement of speed. Observing that a car is traveling 35 miles per hour due north is a measurement of velocity.
An inner, terrestrial (rocky) planet that is slightly smaller than Earth. Located between the orbits of Mercury and Earth, Venus has a very thick atmosphere that is covered by a layer of clouds that produce a “greenhouse effect” on the planet. Venus’s surface temperature is roughly 480°C (900°F), making it the hottest planet in the solar system.
One of the world’s premier radio observatories, consisting of 27 antennas arranged in a huge “Y” pattern. The VLA spans up to 22 miles (36km) across, which is roughly one and a half times the size of Washington, D.C. Each antenna is 81 feet (25 meters) in diameter. Located in Socorro, New Mexico, the telescopes work in tandem to produce a sharper image than any single telescope could record.
The part of the electromagnetic spectrum that human eyes can detect; also known as the visible spectrum. The colors of the rainbow make up visible light. Blue light has more energy than red light.
A break or vent in the crust of a planet or moon that can spew extremely hot ash, scorching gases, and molten rock. The term volcano also refers to the mountain formed by volcanic material.
A vibration in some media that transfers energy from one place to another. Sound waves are vibrations passing in air. Light waves are vibrations in electromagnetic fields.
The distance between two wave crests. Radio waves can have lengths of several feet; the wavelengths of X-rays are roughly the size of atoms.
Light is measured by its wavelength (in nanometers) or frequency (in Hertz).
One wavelength: equals the distance between two successive wave crests or troughs.
Frequency (Hertz): equals the number of waves that passes a given point per second.
The force that governs the change of one kind of elementary particle into another. This force is associated with radioactive processes that involve neutrons.
The hot, compact remains of a low-mass star like our Sun that has exhausted its sources of fuel for thermonuclear fusion. White dwarf stars are generally about the size of the Earth.
The Hubble Space Telescopes workhorse instrument, WFPC2 snapped high-resolution images of faraway objects. Its 48 filters allowed scientists to study precise wavelengths of light and to sense a range of wavelengths from ultraviolet to near-infrared light. The instruments four CCDs (charge-coupled devices) collected information from stars and galaxies to make photographs. WFPC2 was installed aboard the Hubble telescope during the December 1993 servicing mission and was replaced by Wide Field Camera 3 in 2009 during Servicing Mission 4.
This new camera replaced the Wide Field and Planetary Camera 2 during Servicing Mission 4. WFC3 has the latest CCD (charge-coupled device) technology and optical coatings which provide a broader range of colors, spanning ultraviolet, visible, and near-infrared wavelengths. WFC3 will greatly enhance Hubble's observational capabilities by studying a diverse range of objects and phenomena, from early and distant galaxy formation to nearby planetary nebulae, and finally our own backyard – the planets and other bodies of our solar system.
A collection of eight separate, yet interconnected, cameras originally used as the main optical instrument on the Hubble Space Telescope. Four cameras were used in tandem to observe in either wide-field, low-resolution mode or narrow-field, high-resolution (planetary) mode. The Wide Field and Planetary Camera2 replaced the WF/PC during the December 1993 servicing mission.
Identifies the magnifying power of a lens or mirror. For example, a 50-power telescope makes the image 50 times larger than it is when viewed without the telescope.
The part of the electromagnetic spectrum with energy between ultraviolet light and gamma rays. X-rays are used in medicine to detect broken bones and cavities in teeth. Astronomers can detect X-rays from exploding stars and black holes.
Celestial objects that give off X-rays. These exotic objects are producing very energetic radiation and include black holes, neutron stars (pulsars), supernovae remnants, and the centers of galaxies.
A special telescope used to detect X-rays – high-energy electromagnetic radiation. The high energy of X-rays means they will go through rather than bounce off a “normal” telescope mirror. Instead, the mirrors are arranged so the X-rays skip across them much like a stone skips across the surface of a lake.
The point on the celestial sphere that is directly above the observer. Holding a balloon overhead places the balloon at your zenith. Although celestial objects appear to rise and set as they move across the sky, they rarely reach the zenith point. | 0.942666 | 4.088489 |
Physicists Locate Long Lost Soviet Reflector on Moon
Posted on: Apr 29, 2010
A team of physicists led by a professor at UC San Diego has pinpointed the location of a long lost light reflector left on the lunar surface by the Soviet Union nearly 40 years ago that many scientists had unsuccessfully searched for and never expected would be found.
The French-built laser reflector was sent aboard the unmanned Luna 17 mission, which landed on the moon November 17, 1970, releasing a robotic rover that roamed the lunar surface and carried the missing laser reflector. The Soviet lander and its rover, called Lunokhod 1, were last heard from on September 14, 1971.
“No one had seen the reflector since 1971,” said Tom Murphy, an associate professor of physics at UCSD. He heads a team of scientists engaged in a long-term effort to look for deviations of Einstein’s theory of general relativity by measuring the shape of the lunar orbit to within an accuracy of one millimeter, or about the thickness of a paperclip. This is accomplished by timing the reflections of pulses of laser light from reflectors left on the moon by Apollo astronauts and turning the timing measurement into a distance.
“We routinely use the three hardy reflectors placed on the moon by the Apollo 11, 14 and 15 missions,” said Murphy, “and occasionally the Soviet-landed Lunokhod 2 reflector—though it does not work well enough to use when illuminated by sunlight. But we yearned to find Lunokhod 1.”
Three reflectors are required to lock down the orientation of the moon. A fourth adds information about tidal distortion of the moon, and a fifth enhances that information.
“Lunokhod 1, by virtue of its location, would provide the best leverage for understanding the liquid lunar core, and for producing an accurate estimate of the position of the center of the moon—which is of paramount importance in mapping out the orbit and putting Einstein’s gravity to a test,” said Murphy.
Murphy said his team had occasionally looked for the Lunokhod 1 reflector over the last two years, but faced tall odds against finding it until recently. The breakthrough came last month when the high-resolution camera on NASA’s Lunar Reconnaissance Orbiter, or LRO, obtained images of the landing site. The camera team, led by Mark Robinson at Arizona State University, identified the rover as a sunlit speck on the image—miles from where Murphy and his team had been searching. (see: http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100318.html ) But until now the existence of the reflector or its precise location was unknown.
“It turns out we were searching around a position miles from the rover,” said Murphy. “We could only search one football-field-sized region at a time. The recent images from LRO, together with laser altimetry of the surface, provided coordinates within 100 meters, and then we were in business and only had to wait for time on the telescope in good observing conditions.”
On April 22, his team sent pulses of laser light from the 3.5 meter telescope at the Apache Point Observatory in New Mexico, zeroing in on the target coordinates provided by the LRO images. Murphy, together with Russet McMillan of the Apache Point Observatory in Sunspot, NM, and UCSD physics graduate student Eric Michelsen found the long lost Lunokhod 1 reflector and pinpointed its distance from earth to within one centimeter. They then made a second observation less than 30 minutes later that allowed the team to triangulate the reflector’s latitude and longitude on the moon, in other words its exact spot on the moon, to within 10 meters—“not bad for a half-hour’s work,” said Murphy. In the coming months, he estimates it will be possible to establish the reflector’s coordinates to better than one-centimeter precision.
The return signal from the reflector was measured by Murphy’s team as a collection of individual particles, or photons, of laser light.
“We quickly verified the signal to be real and found it to be surprisingly bright: at least five times brighter than the other Soviet reflector, on the Lunokhod 2 rover, to which we routinely send laser pulses,” Murphy said. “The best signal we’ve seen from Lunokhod 2 in several years of effort is 750 return photons, but we got about 2,000 photons from Lunokhod 1 on our first try. It’s got a lot to say after almost 40 years of silence.”
The discovery of the Soviet reflector came as a surprise, because scientists had actively searched for it for nearly four decades without success. Many scientists had speculated that the Lunokhod 1 rover might have fallen into a crater or parked badly, with its reflector not facing the earth, which would have prevented it from being located by laser pulses.
“Not only now do we know that Lunokhod 1 is there, we also know that it is parked perfectly so that its reflector faces earth,” said Murphy. “In fact, the signal is so surprisingly strong that the rover could not be in anything but a level parking spot with its last commanded roll on the lunar surface deliberately oriented toward the earth.”
Murphy and his colleagues found in a study they published this month that lunar dust may be obscuring the reflectors on the moon. see: Moon Dust His team found that the laser light they bounce off reflectors on the moon is fainter than expected and dims even more whenever the moon is full.
“Near full moon, the strength of the returning light decreases by a factor of ten,” he adds. “We need to understand what is causing this if we are contemplating putting additional scientific equipment on the moon. Finding the Lunokhod 1 reflector will add important clues to this study.”
Murphy’s project, dubbed APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation), is supported by the National Science Foundation and NASA, and includes scientists at the University of Washington, Harvard University, the Massachusetts Institute of Technology, Humboldt State University and the Apache Point Observatory. | 0.802094 | 3.637325 |
12 to 16 Years Old
PLANETS OF OUR SOLAR SYSTEM
There are 8 planets in our solar system, four inner planets and four outer planets. The inner planets are rocky and comprise of Mercury, Venus, Earth and Mars. The four outer planets are made of gas and comprise of Jupiter, Saturn, Uranus and Neptune.
All the planets are round in shape, and all orbit around the Sun in a roughly circular orbit, with Neptune being the exception.
Venus and Uranus both rotate clockwise, all the other planets rotate counter-clockwise.
|Average distance from the Sun:||58 million km
(36 million miles)
|Surface temperature:||-180°C to 430°C
(-290°F to 800°F)
|Length of day:||59 days|
|Length of year:||88 Earth days|
|Number of moons:||0|
Mercury is the smallest planet in our solar system, and its size means it cannot hold on to its atmosphere.
Although it is 18 times smaller than Earth, it is much denser due to its larger core of iron and nickel, and because Mercury rotates slower on its axis, its core produces a magnetic field that is 100 times weaker than that of Earth.
The temperatures on Mercury are high enough to melt lead, but at the poles it is so cold that there may be water ice at the bottom of the deep craters.
The first spacecraft to visit Mercury was Mariner 10 in 1974. It sent back over 12,000 pictures showing the planet having a heavily cratered surface. The best known crater is the Caloris Basin which is 1,300 km (800 miles) across. This crater may have been formed by an impact that sent shock waves around the planet as on the opposite side to the crater is a jumble of mountains.
When Mercury passes in front of the Sun, this is known as a transit. The next transit is on 9 May 2016.
Space missions to Mercury:
Mariner 10 – Launched 3 November 1973 and carried out three flybys in 1974 and 1975. During these flybys Mariner 10 took photos of half of the planet’s surface, and sent back data on the planet’s magnetic field, and temperatures.
Messenger – Launched 3 August 2004. It carried out three flybys in 2008 and 2009; then in March 2011 a year-long science orbit of Mercury began. Messenger was intentionally crashed into Mercury on April 30th 2015 after four years orbiting Mercury.
|Average distance from the Sun:||108 million km
(67 million miles)
|Length of day:||243 days|
|Length of year:||224.7 Earth days|
|Number of moons:||0|
Venus is the second planet from the Sun and is very similar to Earth in terms of size, mass and composition, but its thick layer of clouds makes it unsuitable for water and life.
It is so hostile that even the few spacecraft that have landed on the surface only lasted for a few hours.
The planet is covered in thick clouds that are made of sulphuric-acid and a blanket of carbon dioxide gas which traps the heat. Any person landing on Venus would die from a combination of acid burns, roasting, crushing and suffocation.
There are also more than 1,600 volcanoes on Venus.
The highest mountains on Venus are the Maxwell Montes which rise 12 km (7.5 miles) above the surface.
The wind speed on Venus is about 350 km/hr (220 mph); the clouds can circulate around the planet in about 4 days.
About 80% of the Sun’s light is reflected off the atmosphere, making Venus the second brightest object in the night sky, and 20% of the light reaches the surface. Its brightness makes Venus the Evening Star and the Morning Star.
Venus spins clockwise so the Sun rises in the West and sets in the East, and its day is longer than its year.
Space missions to Venus:
Pioneer Venus 1 – Launched 20 May 1978 and entered the orbit of Venus on 4 December 1978. The mission lasted 14 years.
Pioneer Venus 2 – Launched 8 August 1978 – launched 3 probes on 20 November 1978 which reached the Venusian atmosphere on 9 December 1978 which ended the mission.
Venera 13 – Launched 30 October 1981. Venus flyby and landing on 1 March 1982.
Venera 14 – Launched 4 November 1981. Landed on Venus on 5 March 1982.
Magellan – Launched 4 May 1989, entered the orbit of Venus on 10 August 1990, mission ended 12 October 1994.
Venus Express – Launched 9 November 2005. Mission ended 16 December 2014.
When the Venera 13 and 14 landers landed on Venus in March 1982, they sent back pictures showing an orange sky and a desert covered in different size rocks which appear to be flat, suggesting they are made of thin layers of lava. It is estimated that at least 85% of Venus is covered in volcanic rock.
There were a number of missions to Venus, some were flybys by spacecraft on their way to other planets/comets etc.
|Average distance from the Sun:||149,598 km
(92,956 million miles)
|Length of day:||23.934 hours|
|Length of year:||365.26 Earth days|
|Number of moons:||1|
Earth is the fifth largest planet in the solar system and the third from the Sun. It has an atmosphere of approximately 78% nitrogen, 21% oxygen, with trace amounts of water, argon, carbon dioxide and other gases. 71% of the surface is covered in water, and it is the only planet with plant and animal life on it (as far as we know).
The age of our planet is 4.6 billion years and we spin at a speed of 1,609 km/hr (1000 mph).
The Earth is tilted at 23½° which gives us our seasons. When the North Pole is pointed at the Sun, it will be summer in the northern hemisphere, but when the North Pole is pointed away from the Sun then it will be summer in the southern hemisphere.
Over a 26,000 year cycle the direction of the Earth’s axis also changes. This means that after 13,000 years the seasons for winter and summer reverse before returning to their original positions after another 13,000 years.
|Average distance from the Sun:||228 million km
(142 million miles)
|Surface temperature:||-125 to 25°C
(-195 to 77°F)
|Length of day:||24.5 hours|
|Length of year:||687 Earth days|
|Number of moons:||2|
Mars is the fourth planet from the Sun and had rocks which contain iron which has rusted. The fine red dust makes Mars appear orange-red.
The two poles have permanent ice caps. The north pole has an ice cap made of water ice and is 3 km (1.8 miles) thick, and the south pole’s ice cap is made of carbon dioxide and is thicker and colder at -110°C (-166°F).
The atmosphere on Mars is very thin and contains mainly carbon dioxide.
The winds on Mars can reach speeds of up to 400 km/h (250 mph), this creates dust storms which can reach 1,000 m (3,000 ft.) in height, covers vast areas of the planet and last for months.
Mars has the largest volcano in the solar system called Olympus Mons. It is 600 km (373 miles) across and would cover most of England. Its height is 26 km (16 miles), that is 3 times higher than Mount Everest, and at the top is a crater 90 km (56 miles) across.
The Valles Marineris is a system of canyons 4,000 km (2,485 miles) long.
There have been more missions to Mars than any other planet:
Mariner 4 – 1964 (flyby)
Mariner 7 – 1969 (flyby)
Mariner 9 – 1971 (orbiter)
Mars 5 – 1973-1974 (orbiter)
Viking 1 – 1975-1976 – first successful lander
Viking 2 – 1975-1978
Mars Pathfinder – 1997 – delivered first successful rover
Mars Global Surveyor – 1997-2006
Mars Express – 2003
Beagle 2 – 2003 – UK lander believed to have crashed on Mars but in 2015 it was found intact, but the solar panels had not deployed properly to uncover the radio antenna, it was therefore unable to contact Earth
Phoenix – 2008
Spirit – 2004
Opportunity – 2004 – still operational
Curiosity – 2012 – still operational
|Average distance from the Sun:||780 million km
(484 million miles)
|Cloud top temperature:||-143°C
|Length of day:||9.93 hours|
|Length of year:||11.86 Earth years|
|Number of moons:||63|
Jupiter is the fifth planet from the Sun. It is gas giant and the largest planet in the solar system; the other 7 planets could fit inside Jupiter.
Jupiter has a core of rock, metal and hydrogen compounds.
The rest of the planet comprises of an inner layer of metallic hydrogen, an outer layer of liquid hydrogen and helium, and the part that we see is hydrogen and helium gas.
The gases near the core are liquid due to the high temperatures, but it is cold nearer the surface of the planet.
Jupiter comprises of 90% hydrogen (H) gas. The remainder is helium (He), methane (CH4), ammonia (NH3), water (H2O) and ethane (C2H6). It is the liquefaction of these gases that make clouds.
The most famous feature on Jupiter is the Great Red Spot. This was first recorded in 1664, but has halved in size since then.
The white bands of clouds circling Jupiter are known as zones, and the brown bands are called belts.
The clouds at the equator move at more than 45,000 km/h (28,000 mph).
There are some thin, dark rings of dust encircling the planet. These were discovered by Voyager 1 in 1979.
The four main moons of Jupiter are called Io, Europa, Ganymede and Callisto, and are known as the Galilean Moons.
Io is the most volcanically active body in the solar system with temperatures reaching up to 1,500°C (2,730°F) in some hot spots. The volcanoes are caused by Jupiter’s gravity pulling on Io and heating it up.
Europa is similar in size to our Moon and is covered in ice which is continually being renewed. There may be liquid water about 10-20 km (6-12 miles) below the surface.
Ganymede is the largest moon in the solar system with a diameter of 5,260 km (3,270 miles), and is larger than Mercury. It may have a 3-layer interior:
- small, iron-rich core
- rocky mantle
- icy shell on top
There may be a salty ocean 200 km (125 miles) beneath the surface.
Callisto is the moon that is furthest away from Jupiter, and its surface is heavily cratered and dates back billions of years. It is a bit smaller than Mercury, is a mixture of ice and rock, and like Ganymede may have a salty ocean beneath its surface.
Space missions to Jupiter include:
Pioneer 10 – launched 03/1972 – flyby
Pioneer 11 – launched 04/1973 – flyby
Voyager 2 – launched 08/1977 – flyby
Voyager 1 – launched 09/1977 – flyby
Galileo – launched 10/1989 – orbiter and probe
Ulysses – launched 10/1990 – solar orbiter – flew by Jupiter – took some measurements
Cassini – launched 10/1997 – flyby
New Horizons – flyby on its way to Pluto – launched 01/2006
Juno – launched 08/2011 – orbiter – to arrive July 2016
JUICE – due for launch 2022 – orbiter
|Average distance from the Sun:||1,400 million km
(870 million miles)
|Cloud top temperature:||-180°C
|Length of day:||10.6 hours|
|Length of year:||29.4 Earth years|
|Number of moons:||62|
Saturn is the sixth planet from the Sun and is a gas giant. As well as being the second largest planet in the solar system, it is also surrounded by an impressive ring system made from ice and rock.
The ring system comprises of 3 large and bright rings, C, B and A. Then there are the faint outer rings, F, G, and E. The D ring is inside the C ring.
The B ring is the widest at 25,500 km (15,800 miles) across and 5-15 m (15-50 ft.) thick.
There are gaps between some of the rings, the largest being between the A and B rings, called the Cassini Division. These gaps are caused by the gravity of Saturn’s moons sweeping the area clear.
Sometimes white areas appear on Saturn; these are giant storms with wind speeds up to 1,800 km/hr (1,100 mph).
Storms also occur at Saturn’s poles, and like the hurricanes on Earth, they have an “eye”.
Like Earth, Saturn can have auroras (rings of light).
Saturn has 62 moons, most of which are small.
The main moons which lie within Saturn’s rings are:
The largest moons that lie outside Saturn’s rings are:
Phoebe – has its own ring made of ice and dust
Hyperion – tumbles as it orbits Saturn and looks like a sponge
Iapetus – covered in dust on one side which comes from Phoebe
Titan – second largest moon in the Solar System, bigger than Mercury, has its own atmosphere. The Cassini orbiter launched a probe, Huygens, to land on titan on 14 January 2005, the first and only spacecraft to land on a world in the outer solar system.
Space missions to Saturn:
Pioneer 11 – launched 5 April 1973 – flyby 1 September 1979 – final contact 24 November 1995
Voyager 2 – launched 20 August 1977 – flyby 26 August 1981
Voyager 1 – launched 5 September 1977 – fly by 12 August 1980
Cassini – launched 15 October 1997 – arrived 1 July 2004 – Orbiter - launched Huygens lander to Triton – 24 February 2004 – landed 14 January 2006 – mission still ongoing
|Average distance from the Sun:||2,870 million km
(1,784 million miles)
|Cloud top temperature:||-216°C
|Length of day:||17.25 hours|
|Length of year:||84 Earth years|
|Number of moons:||27|
Uranus is the seventh planet from the Sun. It is a blue gas planet with storms that travel around the planet at twice the speed of Earth’s hurricane winds, and spins in the opposite direction to Earth.
It was discovered by William Herschel in 1781.
It is thought that Uranus may have collided with a planet-size body which caused it to tip on to its side, this means its poles face the sun which each pole having 21 years of sunlight then 21 years of darkness.
Uranus is surrounded by 13 dark, thin rings which are made up of dust and boulders. These rings are less than 10 km (6 miles) across.
The shepherd moons, Cordelia and Ophelia, keep the particles of the rings in place.
The main moons of Uranus are:
Miranda – the smallest with canyons 12 times deeper than the Grand Canyon
Ariel – the brightest moon
Umbriel – heavily cratered
Titania – one of the largest moons
Oberon – the first moon to be discovered in 1787 by William Herschel
The only space mission to Uranus was a flyby by Voyager 2.
|Average distance from the Sun:||4,500 million km
(2,800 million miles)
|Cloud top temperature:||-220°C
|Length of day:||16 hours|
|Length of year:||165 Earth years|
|Number of moons:||13|
Neptune is the eight planet from the Sun, and like Uranus is a blue gas planet, the colour being caused by methane gas in its atmosphere.
Neptune was discovered by Johann Galle in 1846 after its position was calculated by John Couch Adams and Urbain Le Verrier.
The core of Neptune produces heat which rises causing large storms and which are the fastest in the solar system. These winds can travel around Neptune at speeds of up to 2,000 km/hr (1,240 mph).
Neptune had a feature called the Great Dark Spot, but this only lasted a few years.
Another short-lived feature was a white cloud called Scooter which took only 16.8 days to go around the planet.
Neptune’s largest moon is called Triton, which is smaller than our Moon but larger than Pluto. It has a surface temperature of -235°C (-391°F), making it one of the coldest places in the solar system, and is covered in frozen nitrogen gas.
Neptune’s gravity is pulling Triton closer to the planet.
Neptune has 6 inner moons, the largest of which is Proteus. Proteus takes 27 hours to orbit Neptune.
Five of the moons orbit at a distance of more than 15 million km (9 million miles) and are probably captured comets.
Like Saturn and Uranus, Neptune has a ring system comprising of six very narrow, dark rings. There are four moons which lie inside the ring system, with Galatea and Despine acting as shepherd moons, keeping two of the rings in shape.
The two brightest rings are called Adams ring and Le Verrier.
Like Uranus, there has only been one mission to Neptune and that was a flyby by Voyager 2. | 0.865952 | 3.324898 |
Quarter ♓ Pisces
Moon phase on 19 November 2004 Friday is First Quarter, 7 days young Moon is in Pisces.Share this page: twitter facebook linkedin
First Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 53% and growing larger. The 7 days young Moon is in ♓ Pisces.
* The exact date and time of this First Quarter phase is on 19 November 2004 at 05:50 UTC.
Moon rises at noon and sets at midnight. It is visible high in the southern sky in early evening.
Moon is passing first ∠1° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 0.2% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1938" and ∠1942".
Next Full Moon is the Beaver Moon of November 2004 after 7 days on 26 November 2004 at 20:07.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 7 days young. Earth's natural satellite is moving through the first part of current synodic month. This is lunation 60 of Meeus index or 1013 from Brown series.
Length of current 60 lunation is 29 days, 11 hours and 2 minutes. It is 28 minutes longer than next lunation 61 length.
Length of current synodic month is 1 hour and 42 minutes shorter than the mean length of synodic month, but it is still 4 hours and 27 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠327.5°. At the beginning of next synodic month true anomaly will be ∠345.8°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of perigee on 14 November 2004 at 13:54 in ♐ Sagittarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 10 days, until it get to the point of next apogee on 30 November 2004 at 11:25 in ♋ Cancer.
Moon is 369 822 km (229 797 mi) away from Earth on this date. Moon moves farther next 10 days until apogee, when Earth-Moon distance will reach 405 953 km (252 247 mi).
8 days after its descending node on 11 November 2004 at 07:43 in ♏ Scorpio, the Moon is following the southern part of its orbit for the next 4 days, until it will cross the ecliptic from South to North in ascending node on 24 November 2004 at 04:05 in ♉ Taurus.
22 days after beginning of current draconic month in ♈ Aries, the Moon is moving from the second to the final part of it.
3 days after previous South standstill on 15 November 2004 at 14:59 in ♐ Sagittarius, when Moon has reached southern declination of ∠-28.013°. Next 9 days the lunar orbit moves northward to face North declination of ∠27.963° in the next northern standstill on 29 November 2004 at 08:28 in ♋ Cancer.
After 7 days on 26 November 2004 at 20:07 in ♉ Taurus, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.259508 |
A rare crash at the Milky Way's core
(Phys.org) —University of Michigan astronomers could be the first to witness a rare collision expected to happen at the center of the galaxy by spring.
With NASA's orbiting Swift telescope, the U-M team is taking daily images of a mysterious gas cloud about three times the mass of Earth that's spiraling toward the supermassive black hole at the Milky Way's core. From our vantage point, the core lies more than 25,000 light years away in the southern summer sky near the constellations Sagittarius and Scorpius.
The gas cloud, called G2, was discovered by astronomers in Germany in 2011. They expected it to hit the black hole, called Sagittarius A* (pronounced Sagittarius A-star by astronomers), late last year. That didn't happen, but the cloud continues to drift closer. Astronomers now predict that the impact will occur in the next few months.
Astronomers have never seen anything like this, much less with a front-row seat.
"Everyone wants to see the event happening because it's so rare," said Nathalie Degenaar, who leads this imaging effort as a Hubble research fellow in the Department of Astronomy at the College of Literature, Science, and the Arts.
Supermassive black holes are believed to lurk at the centers of all elliptical and spiral galaxies. The Milky Way's, by comparison, is dim—about a hundred million times fainter than scientists might expect. But it's likely the more common variety, Degenaar said.
"We think that the fainter ones are the majority, but it's very difficult to study those," she said. "We just can't see them. Ours is the only one we can study to understand what their role is in the universe."
The collision will give astronomers a unique opportunity to see how faint supermassive black holes feed and perhaps why they don't consume matter in the same way as their brighter counterparts in other galaxies. While black holes themselves are invisible and don't permit light to escape, the material falling into them shines in X-rays.
Since 2006, Degenaar and her colleagues have been using Swift's X-ray instruments to observe not just Sagittarius A*, but also some smaller black holes and neutron stars that reside at the galaxy's center with it. Neutron stars are the smallest, most dense star remnants from those that aren't quite massive enough to collapse into black holes.
The Swift observatory is the only telescope providing daily updates at X-ray wavelengths where the crash will show up most profoundly, the researchers said. Those capabilities, coupled with a research tool developed by Mark Reynolds, an assistant research scientist in astronomy at U-M, will help provide the first evidence of the collision. This tool quickly analyzes changes in the X-ray brightness of images across days—a sudden increase could signal impact. It also immediately posts the images online.
While astronomers expect to see a change in brightness, they don't know how dramatic it will be because they aren't sure exactly what the gaseous G2 object is. If it's all gas, the region would glow in the X-ray band for years to come as the black hole slowly swallows the cloud. But another possibility is that G2 could be shrouding an old star. If that's the case, the display would be less spectacular as Sagittarius A* slurped from the cloud while the star slipped by, dense enough to fight its grasp.
"I would be delighted if Sagittarius A* suddenly became 10,000 times brighter. However it is possible that it will not react much—like a horse that won't drink when led to water," said Jon Miller, a U-M associate professor of astronomy who also works on the project. "If Sagittarius A* consumes some of G2, we can learn about black holes accreting at low levels—sneaking midnight snacks. It is potentially a unique window into how most black holes in the present-day universe accrete."
Black holes play a key role in the life cycles of galaxies.
"They eat matter from their surroundings and blow matter back. The way they do that influences the evolution of the entire galaxy—how stars are formed, how the galaxy grows, how it interacts with other galaxies," Degenaar said. "Even more broadly, the way galaxies evolved is important for the evolution of the whole universe, how it came into being and how it's changing." | 0.851732 | 3.847152 |
Unless you live underground or in a very cloudy part of the world, it was pretty hard to miss the crazy conjunction of Venus and Jupiter Monday night that, when joined by the crescent moon, smiled on one side of Earth while frowning on the other.
Best known for being the brightest planet visible without the aid of a telescope, Venus gets even more interesting when you have the technology to peer under her skirts, so to speak, using wavelengths of light that are invisible to the human eye.
—Image courtesy ESA/MPS/DLR/IDA
In ultraviolet light, ESA’s Venus Express probe shows the planet as a smoky blue sphere with roiling bands of light and dark that highlight its complex structures of sulfuric acid clouds.
The big mystery, however, is which chemical in the Venusian clouds is absorbing UV light and thus creating the darker areas.
The planet’s dense cloud layer definitely covers the surface pretty thoroughly, as seen in optical images.
So why should some regions reflect UV while others absorb?
The shroud of clouds over Venus, as seen by the MESSENGER spacecraft in June 2007
—Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Meanwhile, in infrared the planet appears in fiery hues of orange, red, and near-black that show how high and how hot its cloud tops are—the darker the zone, the cooler the clouds.
Mixing the two sets of images allowed researchers, led by Dmitri Titov of the Max Planck Institute for Solar System Research in Germany, to link the mysterious dark zones seen in UV light to a process called natural convection.
—VMC ultraviolet image courtesy ESA/MPS/DLR/IDA; VIRTIS infrared image courtesy ESA/ VIRTIS/ INAF-IASF/ Obs. de Paris-LESIA
When water boils in a pot, the flame gets H2O molecules near the bottom hot and thus less dense, so they rise to the surface.
Colder molecules then sink to replace them, get heated up themselves, and rise back up. This process creates currents in the liquid, which we see as the familiar bubbling cauldron.
What Titov and co. found out is that in UV light, Venus sports a particularly dark region near its equator, signaling a concentration of the mysterious chemical.
In infrared, temperatures in this same region match a pattern of convection—clouds near the surface get heated up enough by the planet’s nightmare greenhouse effect that the atmosphere starts to “boil” and the clouds rise.
So. It seems Venus’s clouds are boiling, and this has something to do with the distribution of chemicals inside.
But the study still can’t answer the burning question of what exactly is this odd absorbent cloud component?
Back to you, science. | 0.847671 | 3.910962 |
Crescent ♊ Gemini
Moon phase on 25 March 2015 Wednesday is Waxing Crescent, 6 days young Moon is in Gemini.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 20 March 2015 at 09:36.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠13° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 2.7% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1872" and ∠1924".
Next Full Moon is the Pink Moon of April 2015 after 10 days on 4 April 2015 at 12:06.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 6 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 188 of Meeus index or 1141 from Brown series.
Length of current 188 lunation is 29 days, 9 hours and 21 minutes. It is 5 minutes longer than next lunation 189 length.
Length of current synodic month is 3 hours and 23 minutes shorter than the mean length of synodic month, but it is still 2 hours and 46 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠9.9°. At beginning of next synodic month true anomaly will be ∠27.1°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
5 days after point of perigee on 19 March 2015 at 19:38 in ♓ Pisces. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 7 days, until it get to the point of next apogee on 1 April 2015 at 12:59 in ♍ Virgo.
Moon is 382 856 km (237 896 mi) away from Earth on this date. Moon moves farther next 7 days until apogee, when Earth-Moon distance will reach 406 012 km (252 284 mi).
4 days after its descending node on 21 March 2015 at 02:19 in ♈ Aries, the Moon is following the southern part of its orbit for the next 9 days, until it will cross the ecliptic from South to North in ascending node on 4 April 2015 at 03:17 in ♎ Libra.
17 days after beginning of current draconic month in ♎ Libra, the Moon is moving from the second to the final part of it.
11 days after previous South standstill on 14 March 2015 at 01:39 in ♐ Sagittarius, when Moon has reached southern declination of ∠-18.262°. Next day the lunar orbit moves northward to face North declination of ∠18.241° in the next northern standstill on 26 March 2015 at 14:29 in ♊ Gemini.
After 10 days on 4 April 2015 at 12:06 in ♎ Libra, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.206299 |
Because of the longer exposure times used by the Hyper Suprime-Cam survey, the asteroids look bean-shaped or elongated in the HSC search. This trailing is due to the asteroid’s relative motion to the Earth. We’re seeing it move and therefore its light is deposited in slightly different positions along the camera’s field-of-view during the exposure, creating a streak or trail. As far as we can find in the scientific literature, nearly all main-belt comets were detected in images will little trailing. We found one example, that we wanted to share with you. Below is a well-known image of Main Belt Comet 107P/Wilson-Harrington. This observation was actually taken back in 1949 (on glass plates!) by the 48-inch Oschin Schmidt telescope on Mt. Palomar for use in the Palomar Observatory Sky Survey (Fun Fact – I used the same telescope for my thesis survey for distant Kuiper belt objects nearly 60 years later).
Yanga Fernandez, Lucy McFadden, Carey Lisse, Eleanor Helin, and Alan Chamberlin went back to these observations in 1996/1997 and found that this asteroid was active as an MBC with a visible tail! You can find their paper here (unfortunately it’s behind a paywall, but you can read the paper abstract for free). The asteroid is very streaked, a bit more than what you typically see on the Comet Hunters HSC search, but it gives you an idea. The tail is faint and diffuse, but visible off to the left of the streak.
In case you need help spotting the tail, I’ve annotated this version below with magenta arrows pointing to the tail.
I wrote this sitting on a plane on the way to Grapevine, Texas. I’m on my way to the American Astronomical Society winter meeting. It is the largest meeting of astronomers in the United States. I’ll be presenting a talk on Comet Hunters about the Hyper Suprime-Cam search.
A question that pops up from time to time on Comet Hunters Talk is whether or not we can see the shape of an asteroid in the HSC and Suprime-Cam observations. The answer to that is no. The Subaru Telescope does not have the resolution to resolve the shape of the asteroid. The asteroid is viewed by the telescopes and cameras as point-like and smeared out to the turbulence in the atmosphere and the optics of the cameras just like the background stars, so we can’t infer anything about the shape of the asteroid in most case just from what we see in the Comet Hunters images displayed on the site. In the HSC workflow, many of the asteroids look streaked or ‘bean shaped’ compared to the stationary background stars. This is due to the asteroid’s motion. The HSC observations are close to 150 seconds, and in that amount of time some asteroid orbits have on-sky velocities that move a noticeable number of pixels elongating the asteroid’s appearance in the image.
But there are other ways to indirectly probe the shape of the asteroid. You can use the varying amount of light reflected by the asteroid over time to estimate the shape of the asteroid and how it rotates. Asteroids don’t produce their own light source. In the optical wavelengths (what our eyes can see), asteroids are reflecting a portion of the Sun’s light. How much surface area and the type of surface changes the amount of sunlight reflected back to the Earth. If the object is very round, you’ll see a nearly uniform amount of light from the object. If the asteroid is oblong, you’ll see the object brighter when the longer axis is facing Earth and a see it is fainter when the smaller axis as the body rotates. This picture can be complicated if there is compositional differences on the asteroid’s surface and how much light those different surface types absorb and reflect sunlight. I high recommend checking out Pedro Lacerda’s light curves of small solar system bodies website to see simulated light curves (brightness measurements over time) of small solar system bodies. | 0.809567 | 3.831896 |
Jan 10, 2018
No precipitation of any kind was detected on Titan.
The Cassini mission to Saturn is over, but planetary scientists continue to analyze its data set. One of the most studied objects around Saturn is its giant moon, Titan.
Scientists believe that liquid methane exists on the surface of Titan, constantly replenished by methane raining out of its atmosphere. However, images from the Huygens lander revealed a landscape with the consistency of damp sand. A field of small pebbles extended to the horizon. Spectrographic analysis of the “rocks” indicated that they are made of water ice. Ice acts like rock when it is at a temperature of minus 179 Celsius. What Huygens did not detect was liquids of any kind.
According to a Cornell University press release, astronomers recently constructed a new topographic map of Titan. Several new features, including some small mountains and two depressions in its equatorial region were found. Titan’s “lakes” are also a topic of research in the consensus community. However, Electric Universe proponents think differently about the potential for liquid hydrocarbons on its surface.
One discovery leads to a puzzle: researchers found that “…lakes exist hundreds of meters above sea level, and that within a watershed, the floors of the empty lakes are all at higher elevations than the filled lakes in their vicinity.”
Another mystery is that the lakes are contained in sharply-defined depressions. As the announcement states, they “…literally look like you took a cookie cutter and cut out holes in Titan’s surface.” They are also enclosed by steep ridges, some of them hundreds of meters high.
Titan’s low gravity means that methane gas is constantly escaping from its atmosphere. Sunlight also causes the methane molecule to dissociate into its carbon and hydrogen constituents. Conventional theories state that Titan is billions of years old, so why do the lakes exist?
Team members speculate that so-called “cryo-volcanoes” replenish Titan’s atmosphere. They are thought to bring gases out from the interior as Titan is squeezed and twisted by Saturn’s tidal forces. However, in an Electric Universe, it is more likely that Titan retains its atmosphere because it is a relative newcomer to the Solar System. Saturn contains a great deal of methane in its atmosphere, so if Titan came into existence just a few thousand years ago, it has not had time to lose the gas to space.
A previous Picture of the Day noted that flowing methane (or ethane) has never been found on Titan and that the entire line of reasoning follows from an assumption without foundation. The so-called “river valleys” on Titan do not look as if they were carved-out by flowing liquids. Electric Universe advocates predicted that an examination of the images would reveal the “rilles” going uphill and downhill, rather than always downhill, as a moving stream would do. Rather, what we see on Titan are probably electric discharge effects.
On July 8, 2009, Cassini detected a flash of light from Titan. The infrared reflection came from an area known as Kraken Mare (“Monster Ocean”) that covers more than 400,000 square kilometers. Riverbeds seem to flow into several of the presumed lakes. A previous Picture of the Day suggested that the lakes on Titan are similar to the “maria” on the Moon. Moreover, all the “river” channels on Titan are dry, with dark, flat floors. In reality, Titan’s Kraken Mare resembles Mare Serenitatis—the same rilles are present on Titan as on the Moon.
In previous Picture of the Day articles about the Moon, “sinuous rilles” were identified as the scars left by plasma discharges of immense proportions. Practically every body in the Solar System, other than the gas giant planets, exhibit such rille structures.
Electric Universe advocate Wal Thornhill observed that the images from Cassini are “…typical of arc machining of the surface. I would compare them directly to the scalloped scarring on Jupiter’s moon Io and the flat, melted floor depressions that result. Such floors would be expected to give a dark radar return.”
The “lakes” are close by the vast dune fields in the polar regions, suggesting an electrical origin. Since electrical activity has been shown to carve the surface of other rocky bodies, why should it be a surprise to find that it was also at work on Titan? The infrared light seen by Cassini was reflected by the hard, glassified crust left by an interplanetary plasma discharge. | 0.851913 | 3.840704 |
The upper layers in the atmospheres of gas giants – Saturn, Jupiter, Uranus and Neptune – are hot, just like Earth’s. But unlike Earth, the Sun is too far from these outer planets to account for the high temperatures. Their heat source has been one of the great mysteries of planetary science.
The above false-color composite image shows auroras (depicted in green) above the cloud tops of Saturn’s south pole. The 65 observations used here were captured by Cassini’s visual and infrared mapping spectrometer on Nov. 1, 2008. Credit: NASA/JPL/ASI/University of Arizona/University of Leicester
New analysis of data from NASA’s Cassini spacecraft finds a viable explanation for what’s keeping the upper layers of Saturn, and possibly the other gas giants, so hot: auroras at the planet’s north and south poles. Electric currents, triggered by interactions between solar winds and charged particles from Saturn’s moons, spark the auroras and heat the upper atmosphere. (As with Earth’s northern lights, studying auroras tells scientists what’s going on in the planet’s atmosphere.)
The work, published April 6 in Nature Astronomy, is the most complete mapping yet of both temperature and density of a gas giant’s upper atmosphere – a region that has, in general, been poorly understood.
By building a complete picture of how heat circulates in the atmosphere, scientists are better able to understand how auroral electric currents heat the upper layers of Saturn’s atmosphere and drive winds. The global wind system can distribute this energy, which is initially deposited near the poles toward the equatorial regions, heating them to twice the temperatures expected from the Sun’s heating alone.
The aurora at Saturn’s southern pole is visible in this false-color image. Blue represents the aurora; red-orange is reflected sunlight. The image was gathered by Cassini’s ultraviolet imaging spectrograph (UVIS) on June 21, 2005. Credit: NASA/JPL/University of Colorado
“The results are vital to our general understanding of planetary upper atmospheres and are an important part of Cassini’s legacy,” said author Tommi Koskinen, a member of Cassini’s Ultraviolet Imaging Spectograph (UVIS) team. “They help address the question of why the uppermost part of the atmosphere is so hot while the rest of the atmosphere – due to the large distance from the Sun – is cold.” | 0.842377 | 3.984129 |
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