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Imagine you're outside, walking happily on a beautiful sunny day. Suddenly, the light gets intense. You look up, and see a bright flash filling everything. Seconds later, a powerful wind starts pushing the clouds out of view at hypersonic speed. Buildings, trees, and people fly away, disintegrating into a billion pieces. Everything around you disappears and the sky is no longer blue, because the atmosphere has been blown away like a candle.
Sadly—or fortunately—you wouldn't be able to see this spectacular show, because you would have been dead a few minutes ago. But some lucky scientists have been able to observe this very thing—or something quite similar—for the first time and from a safe distance, on a completely different planet than Earth. It happened to HD 189733b, an exoplanet orbiting a star 63 light years away from us.
First, NASA's Swift telescope detected a furious X-ray flare from that distant star. Then, the Hubble Space Telescope observed as the nearby planet's upper atmosphere was blown away. The flare was just like the ones burped out by our Sun, but much stronger. In fact, scientists calculate that the planet received "three million times as many X-rays as Earth receives from a solar flare at the threshold of the X class."
In their observations, researchers found that at least 1,000 tons of gas were being ejected from the planet's atmosphere every second, with speeds that reached more than 300,000mph (482,803 km/h). What an amazing and frightening view this must be.
According to lead researcher Alain Lecavelier des Etangs at the Paris Institute of Astrophysics (IAP), this is "an unprecedented view of the interaction between a flare on an active star and the atmosphere of a giant planet."
This is HD 189733A, the star that blasted this planet. It's 80 percent the mass of our Sun.
The star's X-ray emission blowing off the planet's upper atmosphere.
Of course, that exoplanet is nothing like Earth. It's what astronomers call a hot Jupiter, a giant gas planet 14 percent larger than our own one-eyed neighbor. Inside the planet's deep atmosphere the temperatures reach 1,900 degrees Fahrenheit (1,030 C). But unlike our Jupiter, this one is so close to the star that can get affected by the star's flares.
Had it been a rocky planet like Earth, there probably wouldn't have been any atmosphere left, pretty much like Mercury. [NASA] | 0.841245 | 4.014835 |
Astronomers have found a bizarre asteroid orbiting the sun in the wrong direction while playing a risky game of "chicken" with the largest planet in the solar system.
The unnamed asteroid shares Jupiter's orbital space while moving in the opposite direction as the planet, which looks like a recipe for a collision, astronomers said. Yet somehow, the asteroid has managed to safely dodge Jupiter for at least tens of thousands of laps around the sun, a new study showed.
This mysteriously lucky asteroid was discovered in 2015 by astronomers using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) in Hawaii. It was given the provisional designation 2015 BZ509 with the nickname "BZ." Scientists noticed that the asteroid moves in the opposite direction of every planet and 99.99 percent of asteroids orbiting the sun, in a state known as retrograde motion.
While BZ appeared to be encroaching on Jupiter's orbit, researchers said they needed to observe the asteroid further to confirm their suspicion. The team, led by Paul Wiegert of Western University in Ontario, Canada, began tracking BZ using the Large Binocular Telescope (LBT) at the Mount Graham International Observatory in Arizona. From the new observations they made, the researchers confirmed that the rare, retrograde asteroid does indeed co-orbit Jupiter.
Other asteroids are known to orbit in retrograde, making the backwards motion by itself "unusual but not unique," Wiegert said in a statement. "The stranger thing is that BZ is also playing a cosmic game of 'chicken' with the giant planet Jupiter," he added. "The other retrograde asteroids tend to remain away from the planets."
About 6,000 asteroids share Jupiter's orbital path. Known as Trojan asteroids, they tend to cluster into two groups orbiting ahead of and behind Jupiter at the planet's two stable Lagrange points, located about 60 degrees ahead and 60 degrees behind Jupiter along its path around the sun. Because these asteroids orbit the sun in the same direction as the planet, called prograde motion, they won't collide with Jupiter, Wiegert said. BZ, on the other hand, makes a close call with every orbit, buzzing dangerously close to the gas giant.
"This is not what one would expect to be a very long-lived situation, but this study shows that BZ has done so safely for at least tens of thousands of 'laps,' avoiding [Jupiter] by weaving in and out of the planet's path every time they pass," Wiegert said. "2015 BZ509 is the first asteroid known to have this relationship with any of the planets. Calculations show it will continue to safely navigate its unusual path for the next million years at least." [The 7 Strangest Asteroids in the Solar System]
BZ may seem like a lucky asteroid, narrowly dodging its own demise over and over for such a long time. But surprisingly, Jupiter's gravity has played a big role in helping the asteroid to avoid such a collision, Wiegert said.
"BZ passes once inside and once outside Jupiter each time they orbit the sun, and the two gravitational tugs that Jupiter gives the asteroid cancel out, giving BZ opposing 'nudges' that keep it on track," Wiegert said. "Ironically, BZ would be more likely to crash into Jupiter if that planet had no gravity at all, because without the gravitational nudges, [the asteroid] would gradually drift out of sync with that planet."
The results of the study were published online today (March 29) in the journal Nature. | 0.866932 | 3.583678 |
While previously, researchers were not sure as to what was producing these unknown cosmic rays, a group of scientists believe they finally found out the culprit behind them.
“These results represent the first indications of where the Milky Way’s highest energy cosmic rays could come from,” says Associate Professor Gavin Rowell, from the University of Adelaide’s High Energy Astrophysics Group and leader of Australia’s participation in the HESS Collaboration.
“The most plausible ‘engine’ for this cosmic ray acceleration is the super-massive black hole right at the heart of our galaxy.”
According to a group of researchers, a number of ‘alien’ rays from outer space are hitting our planet. The group of researchers believes that the enigmatic rays are coming from a super-massive black hole which is located at the center of our galaxy. The supermassive black hole is believed to have the size of 4-5 million suns according to reports from German and Australian scientists.
The supermassive black hole is believed to be so strong that nothing, not even light, can escape is crushing clutch.
“The black hole’s gravity of course attracts lots of matter to it,” said Adelaide University astrophysicist Dr Gavin Rowell. “As the matter approaches the black hole, it spirals around, like water going down a plughole, and speeds up.”
According to reports recently published in the Journal Nature, the high energy cosmic rays which are comprised of charged atomic nuclei like protons, are accelerating from the center of the milky way towards us. While in the past, researchers were not sure where these enigmatic rays originated from, a new study has shown that Sagittarius A*, as the black hole has been called, is the sole responsible body, and not the remnants of dead stars as researchers speculated in previous theories.
Scientists believe that as it speeds up, matter becomes very energetic and hot which creates the ideal conditions to release and accelerate charged particles or cosmic rays.
“This is quite a theoretical area of physics but is generally well accepted as a very powerful process to accelerate particles,” Dr Rowell said. Other examples of this are sometimes observed near smaller black holes orbited by single stars.
“Cosmic rays account for up to half of the natural ionising radiation we experience in our lives,” said Dr Rowell, whose team observed coming from the Milky Way’s centre a series of gamma rays, a penetrating form of radiation and a “tracer” of cosmic rays.
“Based on the gamma rays, we found that the cosmic rays are packed with the highest energy that our galaxy is thought to produce,” he said.
“The most striking aspect is that the gamma ray emission properties tell us that they come from a source of cosmic rays with energies reaching 100 times higher than that of the Large Hadron Collider in CERN, Switzerland,” added Rowell. | 0.836889 | 3.872064 |
The Milky Way • We see a band of faint light running around the entire sky. • Galileo discovered it was composed of many stars. • With unaided eye you can see light and dark patches.
Measuring the Milky Way • William Herschel Star Counting • Assumed all stars same brightness • Did not know about interstellar medium • Diameter ~ 10,000 pc • Thickness ~ 2000 pc
Measuring the Milky Way Variable stars provide a better way to measure distances. Stars whose luminosity varies in a regular way are called intrinsic variables. Two types of intrinsic variables have been found: RR Lyrae stars, and Cepheids.
Measuring the Milky Way RR Lyrae • The upper plot is an RR Lyrae star. All such stars have essentially the same luminosity curve, with periods from 0.5 to 1 day. • The lower plot is a Cepheid variable; Cepheid periods range from about 1 to 100 days.
Measuring the Milky Way • Variable stars are typically giants near the end of their lives. • They are variable because of unstable hydrostatic eq. • Can be seen at great distances • Located along instability strip on H-R Dia.
Measuring the Milky WayTheperiod–luminosity relation • Discovered 2400 variable stars. • Observed Cepheid variable stars in LMC and SMC. • In 1912 discovered Period-Luminosity Relation for Cepheids • Cepheids could be used to estimate distances. Henrietta Leavitt (1868-1921)
Measuring the Milky WayTheperiod–luminosity relation • RR Lyrae stars have about the same luminosity (absolute mag.) • Cepheidsluminosity (absolute mag.) is linearly related to pulsation time. • This allows us to use m-M to calculate distances M
Measuring the Milky Way • Many RR Lyrae stars are found in globular clusters. • Harlow-Shapley used RR Lyrae stars in globular clusters to measure size of Milky Way. • Spherical shape at ~30,000 pc • Sun was NOT at center. • This was size of the Universe
Measuring the Milky Way We have now expanded our cosmic distance ladder one more step:
Galactic Structure This artist’s conception shows the various parts of our Galaxy, and the position of our Sun:
Our Parent Galaxy From Earth, see few stars when looking out of galaxy (red arrows), many when looking in (blue arrows). Milky Way is how our Galaxy appears in the night sky (b).
Our Parent Galaxy Our Galaxy is a spiral galaxy similar to these two examples Edge-on spiral Face-on spiral
Galactic Structure The Galactic halo and globular clusters formed very early; the halo is essentially spherical. All the stars in the halo are very old, and there is no gas and dust. The Galactic disk is where the youngest stars are, as well as star formation regions – emission nebulae, large clouds of gas and dust. Surrounding the Galactic center is the Galactic bulge, which contains a mix of older and younger stars.
Galactic Structure This infrared view of our Galaxy shows much more detail of the Galactic center than the visible-light view does, as infrared is not as much absorbed by gas and dust.
Galactic Structure Stellar orbits in the disk are in a plane and in the same direction; orbits in the halo and bulge are much more random.
The Formation of the Milky Way The formation of the Galaxy is believed to be similar to the formation of the solar system, but on a much larger scale:
Galactic Spiral Arms Measurement of the position and motion of gas clouds shows that the Milky Way has a spiral form:
Galactic Spiral Arms The spiral arms cannot rotate along with the Galaxy; they would “curl up”:
Galactic Spiral Arms Instead, they appear to be density waves, with stars moving in and out of them much as cars move in and out of a traffic jam:
Galactic Spiral Arms As clouds of gas and dust move through the spiral arms, the increased density triggers star formation. This may contribute to propagation of the arms. The origin of the spiral arms is not yet understood.
The Mass of the Milky Way Galaxy The orbital speed of an object depends only on the amount of mass between it and the Galactic center:
The Mass of the Milky Way Galaxy Once all the Galaxy is within an orbit, the velocity should diminish with distance, as the dashed curve shows. It doesn’t; more than twice the mass of the Galaxy would have to be outside the visible part to reproduce the observed curve.
The Mass of the Milky Way Galaxy • What could this “dark matter” be? It is dark at all wavelengths, not just the visible. • Stellar-mass black holes? • Probably no way enough could have been created • Brown dwarfs, faint white dwarfs, and red dwarfs? • Currently the best star-like option • Weird subatomic particles? • Could be, although no evidence so far
The Mass of the Milky Way Galaxy A Hubble search for red dwarfs turned up very few; any that existed should have been detected:
The Mass of the Milky Way Galaxy The bending of spacetime can allow a large mass to act as a gravitational lens: Observation of such events suggests that low-mass white dwarfs could account for about half of the mass needed. The rest is still a mystery.
The Galactic Center The Galactic center. The two arrows in the inset indicate the location of the center; it is entirely obscured by dust.
The Galactic Center These images, in infrared, radio, and X-ray, offer a different view of the Galactic center.
The Galactic Center The Galactic center appears to have a stellardensity a million times higher than near Earth; a ring of molecular gas 400 pc across; strong magnetic fields; a rotating ring or disk of matter a few parsecs across; and a strong X-ray source at the center
The Galactic Center Apparently, there is an enormous black hole at the center of the Galaxy, which is the source of these phenomena. An accretion disk surrounding the black hole emits enormous amounts of radiation.
The Galactic Center These objects are very close to the Galactic center. The orbit on the right is the best fit; it assumes a central black hole of 3.7 million solar masses.
Summary • Galaxy is stellar and interstellar matter bound by its own gravity • Our Galaxy is spiral • Variable stars can be used for distance measurement, through period–luminosity relationship • True extent of our Galaxy can be mapped out using globular clusters • Star formation occurs in disk, but not in halo or bulge
Summary, cont. • Spiral arms may be density waves • Galactic rotation curve shows large amounts of undetectable mass at large radii; called dark matter • Activity near Galactic center suggests presence of a 2–3 million solar-mass black hole | 0.830753 | 3.910589 |
Thursday, September 16, 2010
Geo-xcentricities; you too can be Galileo with just a pair of binoculars (and gaffer tape)
Other people, especially Ethan at Starts with a Bang and the Bad Astronomer, have dealt with the technical details (and I have an earlier discussion here and here). My goal is to get you, the ordinary person on the Clapham omnibus (or in my case, the Outer Harbour train, where I am writing this), to try and demonstrate the Earth is heliocentric for yourself and to do so with common household materials. After all, science is at heart a practical endeavour, and non-professionals should be able to find the evidence for themselves.
So for this journey into the starry spheres, we will need a pair of binoculars, a camera tripod, some cardboard and alfoil, and lots of gaffer tape. We also have some luck, as the sky is currently cooperating in the Geocentrism debunking stakes.
First we have to ask ourselves, which “geocentric” theory are we disproving. The classic geocentric theory is that of Ptolemy, in which the planets, Moon and the Sun all orbit the Earth. The most famous variant of this is Tycho Brahe’s helio-geocentric system, where the Sun and Moon orbits the earth and everything else orbits the Sun. There are important differences in the systems which we will explore later.
First off, let’s look at the phases of Venus. For this you will need binoculars and the camera tripod. You will also need a way of attaching the binoculars to the tripod. These days I use a special attachment (but this requires modern binoculars that have a screw thread on the body), but in the past I have used gaffer tape to good effect. Why attach the binoculars to the tripod? Because otherwise there will be too much shaking for you to see the image properly.
The image to the left is the setup I use for observing Sunspots (we come to that later), showing the binoculars gaffer taped to the tripod.
At the moment, Venus is prominent above the western horizon. Point your binocular lash-up at Venus, in my 10x50 binoculars Venus is very small but is a disk which has a distinct “half –Moon” shape. If your binoculars don’t have decent anti-glare coatings, you may have to observe in the early twilight in order to see Venus’s shape without internal reflections from the binocular lenses getting in the way.
As you watch over the coming weeks, you will see Venus expand in size and become more crescent- shaped. Sketch the shape so you can follow its progress. This is so fast you should see a visible change in just one week. By mid-October Venus will be a thin crescent almost 2/3rds bigger than when you started observing. By late October Venus has nearly doubled in size and is a thin, glistening wire. Then Venus vanishes into the Suns glare and reappears in the morning. Over the next few months you can watch Venus shrink and become a tiny disk.
And now you have demolished the Ptolemaic geocentric system. Venus does have phases in this system, but quite unlike what you see here (I leave it too the reader to work out what a Ptolemaic systems Venus phases would look like, you can see a model of Ptolemaic Mercury here, which will give you a good idea). And you have only taken almost 6 months to do it (what, you thought it would be easy). As a reward, here's an animation of the Phases of Venus.
Left image Jupiter above the eastern horizon, Right Image, Venus above the western horizon, both at the same time in the evening (around 8pm ish in mid September 2010).
Jupiter and three of its moons imaged with a mobile phone.
But Ah! The Medicean Stars, now known as the Galilean Moons, they will shuttle backwards and forwards during the nights as you watch. The realisation that these “stars” were Moons of Jupiter were not a blow to any form of geocentrism per se, although they were the second of a series of powerful blows against the Aristotelian physics that underpinned Ptolemy’s system, which aided its demise. Determining that these specks actually orbited Jupiter, and were not just accidentally there, took a lot of effort.
Try keeping track of these sparks, and without reference to an almanac, try and determine their orbits (heck, try and keep track of which near identical points of light are which). It may take a while, you will need to keep careful sketches, and track the Moons and Jupiter with respect to the stars as Jupiter moves through the heavens, but a) You are sketching Venus anyway and b) it will be well worth it (hey, you proving things for yourself!).
The next bit is more demanding. The Phases of Venus demolished the Ptolemaic Geocentric system, but the Tychonian- Geo-heliocentric system had Venus phases just like a pure heliocentric system (which is not surprising, as Tycho’s system is an inverted Copernican system). To eliminate the Tychonian system, we need to observe sunspots.
Luckily the Sun is coming out of its quiet phase, so you will have some to record. For this you will need to set up a safe binocular projection system (as shown above), where the image of the Sun is projected onto a surface so you can record the Sunspots. NEVER LOOK DIRECTLY AT THE SUN WITH BINOCULARS AS SEVERE EYE DAMAGE WILL RESULT.
Anyway, while you are recording the Phases of Venus and the orbits of Jupiters’ Moons, record the passage of Sunspots over the Suns face, over the 5-6 months you are recording the susposts, you will notice the path taken by the sunspots moves up and down. This is due to the Earths orbit not being exactly in the plane of the Suns rotation. In a geocentric system, with the Sun orbiting the earth once a day, this variation would show up on a daily basis, but what you observe can only be seen in a heliocentric system.
So, congratulations, you have just demonstrated that geocentric models don’t describe the solar system we see using very simple tools. It took a while, and was hard work, but you have demonstrated it yourself, and all the blovation of geocentricists won’t take that away (yes, Stellar parallax gets all the glory, but annual Sunspot variation was a powerful blow to Tychonian geocentric models). If you want to, you can take this further by making your own Foucault's Pendulum.
I don't know whether such a system was ever proposed by the followers of Tycho's view which remained popular deep into the 17th century; anyway, historians of science take the discovery of the aberration of starlight by Bradley in 1728 as the first direct proof of heliocentrism. And Bessel, who first measured the parallax, said so himself.
Bradley's insight was not needed to kill off Tycho anymore, though, as Kepler's understanding and Newton's explanation of the planetary orbits in 1689 had made it clear to those listening that everything works so much better with the Sun in the center. A 2003 article by O. Gingerich explains all that very well.
Well, once you have a rotating Earth it's no longer a Tychonian system (Tycho abhorred the idea of any motion of the Earth, and there is no good theoretical reason to tack on a rotating Earth), and because it is no longer an inverted mapping of the Copernican system, you have other problems. Certainly, anyone who was wielding Occams razor would look askance at the rotating Earth-Geo-heliocentric system (A Japanese astronomer did propose a system like this).
Sure you can come up with any range of weird ad-hoc tack-on's to Tycho's scheme, but Tycho's scheme itself was dead in the water with the solar sunspot annual variation.
pAnd People did come up with a whole range of weird versions of Tycho's sytem (eg. only Mercury and Venus orbiting the Sun, everything else orbiting Earth or common centre), but such ad-hoc modifications were never popular (for obvious Occam's Razor reasons).
Acceptance of the heliocentric Keplerian/Netonian scheme was patchy, rapid in some areas, and slow in others (like Scandinavia).
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Um ... that can only mean that the Sun is at the centre of the Earth. :-)
So here are two comentaries on heliocentric arguments, strangely and wrongly neglected, though the observations aren't such as one can make entirely for oneself.
First, we all know that neither stellar aberration nor parallax could have been observed in 1633, for lack of good enough instruments. And a Foucault pendulum, though possible to construct, required a theoretical analysis that exceeded the analytic tools available to Galileo. But there is a perfectly simple demonstration of terrestrial motion, available in the 17th century without a single improvement in technology or analysis: large-scale fluid motion.
From, say, 1550 onward, the ocean currents could have been roughly mapped if anyone had tried. It seems not to have occurred to anyone until a notorious Elephant's Child from the American colonies crossed the Atlantic a couple times, pestered the sailors with questions, and later wrote about the Gulf Stream.
It would have been harder, but still possible, to gather data about prevailing winds. And the first person to see that there was non-obvious stuff about winds, like winds from the East in a storm that was moving West was that same Benjamin Elephantson Franklin. Without a proper analysis of the Coriolis force, anyone who has understood inertial efects could have seen why the currents move in opposite directions in the two hemispheres!
Why do I seem to be the only person who ever thought of this as a low-tech demo available back then if only anyone had asked the questions?
Well, this is much too long, so I'll say more in another comment, pausing only to note the oddity that Galileo wanted to make his demonstration based on the motions of the waters, but he chose the wrong motions.
In fact, it's even stronger than you've mentioned. As you say, the apparent motion of sunspots slopes sometimes upwards, sometimes downwards. But it's better than that: the motions are curved (at most times), as you'd expect from things on a rotating sphere. And the curve is sometimes concave upwards, sometimes the reverse.
If you're moving around an object with a fixed axis of rotation, and you're out of the plane of its equator, this is exactly what you'd see. If you're not, then you can still kludge together some complicated motions, arbitrarily correlated, to account for it (as you can with the other sunspot motions), but who would want to?
Though Galileo used these motions in the Dialogue, and they were among the best arguments there, he did not discover them, and thereby hangs a tale.
Among the people denouncing the Starry Messenger and attacking it on religious grounds was one Franceso Sizzi (1585? - 1618). His book, the Dianoia, was an object of derision to the Jesuit astronomers, who by 1611 had confirmed most or all of the reports in the Messenger. Galileo's friends wanted to see him write one of his fine argumentative blasts at the foolishness, but Galileo "went so far as to apologize for Sizzi and said he had rather have his friendship than triumph in a quarrel with him." [Galileo at Work, Stillman Drake]
Only two years later, Sizzi had turned favorable to Galileo's ideas and sent a description of some new sunspot observations to Galileo's friend Orazio Morandi, who forwarded them to Galileo. It took Galileo some years to see the significance of these, but they are the basis of the sunspot argument he gave in the Dialogue.
Cast your bread upon the waters, and all that.
Everyone knows that a writer should Show and not Tell, but I'm not a good writer, so I'll mention how oddly this episode fits with the image of Galileo as an old meany whose rudeness alienated all his friends, as do other incidents throughout his life.
"....record the passage of Sunspots over the Suns face, over the 5-6 months you are recording the susposts, you will notice the path taken by the sunspots moves up and down. This is due to the Earths orbit not being exactly in the plane of the Suns rotation."
(It is, from the Tychonian viewpoint, due to the Sun's orbit not being exactly in the plane of the Earth's equator. As Einstein has already told us, the two cases are precisely the same, in terms of relative motion).
Think about it for a moment.
We are watching the Sun move, day after day, across the Earth's sky, and it appears each day on the horizon at a point slightly different from the point at which it appeared the day before.
Therefore the sunspots will *of course* also move just that same slight tiny little bit up or down every day, *since the Sun is doing exactly the same thing*!
But the observer would not *notice* the movements of the sunspots in his viewing apparatus on a daily basis, since they are so small.
Only over the 5-6 month period would the movement up or down of the sunspots (and hence, of course, of the *the Sun itself*) have become significantly noticeable.
What we have just described is a little thing called "the seasons".
We don't notice the change every day, but over six months we certainly notice that the day is much longer or much shorter, and this is *all that the author's experiment shows*! | 0.891213 | 3.36439 |
The Kepler Space Telescope’s planet-hunting days are over. NASA announced on 30 October that the spacecraft has run out of fuel and will soon be shut down completely.
Since its launch in 2009, the observatory has found more than 2600 confirmed planets beyond our solar system and many more exoplanet candidates that have yet to be confirmed. Kepler worlds account for about 70 per cent of the total exoplanets we’ve confirmed.
“Before Kepler, we didn’t know if planets were common or rare in our galaxy,” says NASA astrophysics division director Paul Hertz. Now we know that there is a diverse abundance of planets, both similar and different to those in our solar system. “Because of Kepler, what we think about our place in the universe has changed.”
Follow in the footsteps of Kepler and Brahe: Discover Prague on a New Scientist Discovery Tour
Its original mission was set to last only three and a half years, but despite the failure of two reaction wheels used for pointing the spacecraft in 2012 and 2013, it has been operating for more than nine and a half years.
We are getting close to being able to see signs of life on different worlds, says exoplanet pioneer Didier Queloz
The end of Kepler is not unexpected – the craft has been intermittently in sleep mode since late September due to trouble pointing it accurately. These issues were probably related to the low levels of fuel that have now run out completely.
“We collected every bit of possible science data and returned it all to the ground safely,” says Kepler system engineer Charlie Sobeck. “We didn’t have a drop of fuel left for anything else.” Now the team will power down Kepler and leave it to float in orbit around the sun, at a safe distance from Earth. Researchers will continue to comb through the data Kepler captured.
The Transiting Exoplanet Survey Satellite (TESS) was launched in April 2018 and has already begun to take on the mantle of Earth’s planet-hunter. Over the course of its lifetime, TESS is expected to follow up on the Kepler planets that have not yet been confirmed and find more than 20,000 new worlds.
More on these topics: | 0.873095 | 3.12429 |
In the previous log (which gained prominence last month by making it into the list of the top 78 logs ever written on this ambitious interplanetary adventure), we saw the plan for mapping Vesta from an altitude of 680 kilometers (420 miles). In this second high-altitude mapping orbit (HAMO2), the spacecraft circled the alien world beneath it every 12.3 hours. On the half of each orbit that it was on the day side, it photographed the dramatic scenery. As it passed over the night side, it beamed the precious pictures to the distant planet where its human controllers (and many of our readers) reside. Tirelessly repeating this strategy while Vesta rotated allowed Dawn's camera to observe the entirety of the illuminated land every five days.
The robot carried out its complex itinerary flawlessly, completely mapping the surface six times. Four of the maps were made not by pointing the camera straight down at the rocky, battered ground but rather at an angle. Combining the different perspectives of each map, scientists have a rich set of stereo images, allowing a full three dimensional view of the terrain that bears the scars of more than 4.5 billion years in the main asteroid belt between Mars and Jupiter.
NASA / JPL-Caltech / UCLA / MPS / DLR / IDA
Publicia crater (center-right) is located in Vesta’s northern hemisphere. The crater's base features mounds of material that probably tumbled down the crater’s sides. Although the crater looks fresher than most of its neighbors, the material in its base has its own small impact craters, suggesting Publicia has been around for a reasonably long time.
Dawn also mapped Vesta six times during the first high-altitude mapping orbit (HAMO1) in September and October 2011. The reason for mapping it again is that Vesta has seasons, and they progress more slowly than on Earth. Now it is almost northern hemisphere spring, so sunlight is finally reaching the high latitudes, which were under an impenetrable cloak of darkness throughout most of Dawn's residence here.
For most of the two centuries this mysterious orb had been studied from Earth, it was perceived as little more than a small fuzzy blob in the night sky. With the extensive imaging from HAMO1 and HAMO2, as well as from the low-altitude mapping orbit (LAMO), earthlings now know virtually all of the protoplanet's landscape in exquisite detail.
Mission controllers have continued to keep the distant spacecraft very busy, making the most of its limited time at Vesta. Pausing neither to rest nor to marvel or delight in its own spectacular accomplishments, when the robot finished radioing the last of its HAMO2 data to Earth, it promptly devoted its attention to the next task: ion thrusting.
Missions that use conventional propulsion coast almost all of the time, but long-time readers know that Dawn has spent most of its nearly five years in deep space thrusting with its advanced ion propulsion system, the exotic and impressive technology it inherited from NASA's Deep Space 1. Without ion propulsion, the exploration already accomplished would have been unaffordable for NASA's Discovery Program and the unique exploit to orbit both Vesta and dwarf planet Ceres would have been quite impossible. Ion propulsion not only enables the spacecraft to orbit residents of the main asteroid belt, something no other probe has attempted, but it also allows the interplanetary spaceship to maneuver extensively while at each destination, thus tailoring the orbits for the different investigations.
On July 25 at 9:45 a.m. PDT, as it has well over 500 times before, the sophisticated craft began emitting a beam of high-velocity xenon ions. In powered flight once again, it is now raising its orbital altitude. On August 26, the ship will be too far and traveling too fast for Vesta's gravity to maintain its hold. Dawn will slip back into orbit around the sun with its sights set on Ceres.
Although HAMO2 is complete, the spacecraft will suspend thrusting four times to direct its instruments at Vesta during the departure phase, much as it did in the approach phase. The approach pictures aided in navigation and provided tantalizing views of the quarry we had been seeking for so long. This time, however, we will see a familiar world receding rather than an unfamiliar one approaching. But as the sun creeps north, advancing by about three quarters of a degree of latitude per week, the changing illumination around the north pole will continue to expose new features.
On August 15, the craft will interrupt its ascent for four and a half days. By then, Dawn will be at an altitude of about 5,000 kilometers (3,100 miles), but it will still be in orbit. Before it resumes thrusting, it will coast to as high as 6,400 kilometers (4,000 miles) and then descend again. Meanwhile, four times during this period it will photograph the giant asteroid throughout a full Vestan day of 5 hours, 20 minutes. This is a familiar activity for the spacecraft, as it watched Vesta rotate beneath it from a similar vantage point during its spiral descent in July 2011. With Vesta's weak gravitational grip at this distance, Dawn would take more than a week to complete one revolution, so it will be almost as if the probe hovers in place as Vesta pirouettes before its camera. The itinerary is planned so the explorer will begin its observations while flying over the highest northern latitudes, and subsequently it will take the opportunity to observe lower latitudes as it sails down to the equator. The ship will circle so slowly that there will be time between acquiring each set of rotation images to point its main antenna to Earth to transmit its findings. After the third session, while waiting for the orbit to carry it to the latitude needed for the final one, mission planners are squeezing in a routine calibration of the camera and VIR. Dawn will turn to aim them at Jupiter. It is much too far away to reveal any new or interesting details, because the sensors are designed for mapping from close orbit. The planet will appear to be little more than a speck. (Terrestrial observers can gain a better view with binoculars.) But Jupiter is bright and easily seen from there, and it is so well studied that it is a useful reference source to verify that the instruments are still performing in top condition as they continue their discoveries at Vesta.
On August 22, nearly 6,000 kilometers (3,700 miles) over the night side, the probe will halt thrusting again. With the sun on the other side of the protoplanet, Dawn will see only a thin glowing crescent against the deep blackness of space, like a new moon. This is a perspective we have not yet had for Vesta, and although not much of the terrain will be visible, a few pictures to measure the strength of the sunlight's reflection at this extreme angle will be useful for understanding certain properties of the surface material. As a bonus, the view may prove to be quite aesthetically appealing.
Dawn will be patiently and gently thrusting at the moment of escape from Vesta on August 26 and will not even notice a change. It will be as serene and uneventful for the spacecraft (and operations team) as the moment of capture was. Shortly after, when it is around 17,000 kilometers (over 10,000 miles) away, it will watch Vesta rotate once again. On September 1, at a distance of 38,000 kilometers (almost 24,000 miles), it will gaze upon Vesta for the last time. By then, the world it has scrutinized for more than a year will be shrinking rapidly and few details will be visible. Although scientists will spend many years delving into the data the probe has returned, learning more and more not only about Vesta but also what it reveals about the dawn of the solar system, Dawn will leave it behind as it journeys deeper into the main asteroid belt in search of another uncharted world to explore.
Dawn view: NASA / JPL / UCLA / MPS / DLR / IDA / color composite by Daniel Mach�?ek; Hubble view: NASA / ESA / STScI / UMd
Vesta, as seen by Dawn and Hubble
Two views of the asteroid Vesta: the left is a composite natural color view taken from the Dawn spacecraft, and the right was captured by the Hubble Space Telescope.
Dawn is 740 kilometers (460 miles) from Vesta. It is also 2.94 AU (439 million kilometers or 273 million miles) from Earth, or 1,185 times as far as the moon and 2.89 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 49 minutes to make the round trip. | 0.858503 | 3.780356 |
Key Vocabulary: spacetime, speed, kinetic energy, joules, mass, wormhole, parsec, lightyear, galaxy, star system, dimension, time dilation
This weekend, Solo: A Star Wars Story premieres in theaters across the world. The movie tells the origins of the famous smuggler, Han Solo, how met he his best friend Chewbacca, and of course got how he got his hands on the fastest hunk of junk in the galaxy, the Millennium Falcon. It’s no secret I’m a Star Wars fan. As a kid, I idolized Han Solo, jumping into the driver seat of my parent’s minivan as it was parked in the driveway and pretending I was flying through a galaxy far, far away.
But how would traveling across the stars actually work? In Star Wars, ships cruise through hyperspace, traveling across an entire galaxy in what seems like only a few hours. Is traveling faster than light even possible? Can humans one day hop from star system to star system? And if we could, how would this look like?
To be clear, this is not an attempt to assess the scientific accuracy of Star Wars is (hint: it’s not). Rather, think of this as a fun exercise in learning about the weird and too often unrevealed aspects of our Universe.
I’ve got a bad feeling about this: Constraints in hyperspace
Before we can figure out how we could one day zoom around the Universe like Han and Chewie, we need to define what we definitely cannot do within the boundaries of what is physically possible. Not to be a Luke Buzzkiller, but based on our current understanding of physics, traveling faster than the speed of light would be challenging to say the least.
Our first problem is the amount of energy it would take to get our ship to light speed. Light travels at about 3.0 x10^8 m/sec. To give you an idea of how fast that is, it takes about 8.3 minutes for a particle of light to travel the 150 million km from the Sun to the Earth. The amount of energy required to move anything with more mass than a subatomic particle at the speed of light would be astronomical.
Exactly how much energy are we talking about? We can calculate this pretty easily by using the kinetic energy equation (KE=1/2mv² ). Since we already know our velocity (speed of light), all we would need is the mass. According to Wookiepedia, the cargo capacity of the Millennium Falcon is 100 metric tons or 100,000 kg. However, there is no reference to the mass of the ship itself. Let’s estimate that the ship is at least the mass of the cargo. When we plug the mass (100,000 kg) with the speed of light (3.0×10^8 m/sec), we get 4.5×10²¹ Joules, about an order of magnitude greater than the entire world’s annual energy output. An entire planet of nearly 8 billion people uses a tenth of the energy in one year than it would take to get the Millennium Falcon to light speed. So while not technically impossible, it would take technology well beyond our current abilities.
There’s another problem with traveling at the speed of light, this one coming from Albert Einstein and his theory of special relativity. To explain this, imagine two sports cars competing in a 10 km race. They both have a top speed of 100 km/hr, so they should both finish the race in the same amount of time, 6 minutes. However, if the second car travels at a slight angle towards the finish line, it will take slightly longer to complete the race. The first car wins because it is taking a straight path from the start to finish. The second car moving at an angle must travel both forward towards the finish line and side to side. To put it another way, the second card is using part of the 100 km/hr to go to the side, leaving less to move directly towards the finish line.
Einstein theorized that moving through space and time works the same way, that they were just different dimensions of the same continuum. We can move through space in 3 different dimensions; back and forth, right to left, and up and down. But we are also moving through the 4th dimension of time. And just like our race cars, the more speed we dedicate to moving through one dimension, the less we can move through the others.
Instead of thinking that speed of light is 3.0×10^8 m/s, think of it as the top speed of going through all dimensions in the Universe. The faster we move through space, the slower move through time. This isn’t typically a problem in our everyday lives; any speed you have ever traveled at is minuscule compared to the speed of light. But as you approach lightspeed, you would start experiencing time at a different rate than someone who is motionless.
This would have some real consequences for those traveling across the galaxy. Those moving closer to the lightspeed would dedicate more of their speed to travel through space instead of time. As a result, they would experience time at a different rate than some who was relatively motionless, a phenomenon called time dilation. Say you were to travel at the speed of light to get to Alpha Centauri, the closest star system to Earth about 4.3 light-years or 4.07×10¹³ km away. In the time that it would take you to make a round trip, you would experience 8.6 years pass as if everything was normal, but nearly 200 years would have passed on Earth, turning most of your friends and family into force ghosts.
It’s a complex problem to wrap one’s head around and almost seems too bizarre to be true. But amazingly enough, scientists have been able to verify Einstein’s predictions. Researchers at GSI Helmholtz Centre in Germany made a moving clock by accelerating lithium ions to one-third the speed of light. They measured the activity of electrons, which occur at a consistent rate and served as the “ticking” of the clock. They compared that to the “ticking” of lithium ions that were not moving and, just as Albert Einstein predicted more than 100 years earlier, the moving clock measured time at a slower rate.
Never tell me the odds! How we could, maybe, possibly, travel faster than light
Does this mean we are relegated to linger in our dim little corner of the Universe, only traveling to distant worlds in the movies and our imaginations? While physics certainly puts constraints on how fast we can go, there is potential for getting around on a galactic scale and a clue lies in one of the first lines we ever hear from Han Solo.
When Obi-Wan Kenobi and Luke Skywalker first meet Han and Chewie in the cantina on Tatooine, Han almost immediately brags about the speed of his ship, saying that the Millennium Falcon was able to make the Kessel Run in less than 12 parsecs. At first glance, this doesn’t make any sense; a parsec is a unit of distance roughly equal to 3.26 light-years or 3.08×10¹³ km, not a unit of time. Han was probably trying to pull a fast one on who he assumes to be a backwoods farm boy and a washed up old man by throwing out some impressive sounding jargon. But his braggadocio may shed give some insight on how faster than light travel would be possible.
To illustrate this point, take a piece of paper and write point A on the top. Then on the bottom, write point B, which should make both points around 15-20 cm away from each other. However, if you fold your paper in half, point A and point B become much closer to one another.
As we mentioned previously, Albert Einstein theorized that space and time were part of the same continuum, a fabric in which all objects in the Universe interact, with planets, light, and spaceships all moving through it. However, if you could create tunnel between two points on the space-time continuum, your trip across the galaxy could be much, much, shorter. These Einstein-Rosen bridges, or wormholes, are shortcuts that could at least theoretically allow us to cover great distances.
Take, for example, the Kessel Run, a hyperspace route used by scoundrels like as Captain Solo for smuggling contraband. If the Millennium Falcon were to make the trip in less than 12 parsecs, about 40 lightyears, it would cut hundreds if not thousands of lightyears off the journey between star systems. Indeed, researchers at the Autonomous University of Barcelona in Spain created a small wormhole in the lab, transmitting a magnetic field across two points in space. The ability to transport people through a wormhole is still a long way off, however, the idea is at least theoretically possible.
A bunch of mumbo-jumbo?
Speculating how the Millennium Falcon could trek through the stars is a fun exercise how faster than light travel could be possible. But even if Han were to take a wormhole through space-time, the journey would still be extremely long. The Milky Way is 100 thousand lightyears across (we previously had 100 million light-years across – our galaxy is big, but not quite that big); the light that reaches us from the other side of the galaxy was propagated when dinosaurs ruled the Earth. Even if you could take a shortcut, the trip would likely still be far beyond what humans could make in a single lifetime. The distances are just too vast and we have yet to make it past the Moon, a mere 400,000 km from Earth. Such technology, is centuries, if not millennia, away. Until that time, we are more or less stuck in our solar system
But as luck would have it, our solar system is an amazing place. There are at 6 least planets or moons that are at least potentially capable of supporting life. NASA is launching a mission to explore Jupiter’s moon Europa around 2025. Scientists believe there may be a water ocean underneath the surface, with a least a chance of supporting life. Suffice it to say that there’s plenty to explore right here in our own backyard
While we can’t take Star Wars literally in a scientific sense, the movies have inspired a host of innovations. From speeders to droids, even holograms and tractor beams, researchers are astonishingly close to developing technologies that mirror the films. Scientists have also speculated that space-time could be stretched, shrinking the immense distances to something more manageable to cross in a human lifetime.
Just remember that when you see a Star Wars movie, its purpose is not to be scientifically accurate. Its purpose is to be awesome. The familiar backdrop for learning about our mysterious and amazing Universe Stars Wars provides is simply an added bonus.
- What would it be like to fly in a real X-wing? We broke down the physics of piloting a starfighter in two parts. Read part 1 here and part 2 here.
- Researchers detecting gravitational waves, or ripples in the space-time continuum. Read our interview with Dr. Andy Bohn, an astrophysicist who worked on the project. | 0.803188 | 3.49031 |
Poor, dim-witted humanity.
We used to think we were the center of everything. That wasn’t that long ago, and even though we’ve made tremendous advancements in our understanding of our situation here in space, we still have huge blind spots.
For one, we’re only now waking up to the reality of interstellar objects passing through our Solar System.
In 2017, Oumuamua came for a brief visit, and was confirmed as an interstellar object. It’ll never return, and will spend an eternity travelling through the Universe.
Then a few months ago, we detected our first interstellar comet. An amateur astronomer—and telescope engineer—at a star party discovered it, and it was named after him. His name was Gennadiy Borisov, and it’s now called Comet 2L/Borisov. Pretty cool.
But these objects are difficult to study. They show up and leave quickly. Comet Borisov in particular was travelling very quickly, at 32.2 km/s (20 mp/s) relative to the Sun, when inbound to our Solar System.
So how about sending a spacecraft to visit one of these interstellar visitors?
That’s something that Richard Linares, an assistant professor in the Department of Aeronautics and Astronautics (AeroAstro) at MIT, has been thinking about. He’s got an idea.
He’s developing an idea for a “dynamic orbital slingshot for rendezvous with interstellar objects.” Now NASA’s getting involved. The NASA Innovative Advanced Concepts (NIAC) Program provides funding for “innovative aerospace concepts that could enable and transform future missions.” Now NIAC has selected Linares’ research proposal for Phase One funding.
NIAC is a well-known entity in space-science circles. They’ve funded studies into things like deep space probes powered by lightweight nuclear propulsion, sample-return systems for extreme environments, a Pluto Orbiter and Lander powered by Direct Fusion Drive, and dozens of others.
In a press release from MIT, Linares said “There are a lot of fundamental challenges with observing ISOs <Interstellar Objects> from Earth — they are usually so small that light from the sun needs to illuminate it in a certain way for our telescopes to even detect it.”
Not only is light a problem, so is the objects’ speed.
“And they are traveling so fast that it’s hard to pull together and launch a mission from Earth in the small window of opportunity we have before it’s gone,” Linares continued. “We’d have to get there fast, and current propulsion technologies are a limiting factor.”
So what’s his dynamic orbital slingshot, and how would it work?
The idea is centered around solar sails. Solar sails are a propulsion based on stellar pressure, or the pressure of photons from the Sun. By using a thin, light, reflective material to catch those protons, much like a sailboat’s sail catches the wind, spacecraft can be propelled through space. Look at The Planetary Society’s LightSail 2 spacecraft for an example.
Solar Sails have their limitations. They’re effective with very light spacecraft. But a lightweight spacecraft is all a part of Linares’ concept.
Linares’ concept would see a fleet of static satellites on the edges of our Solar System. They would have a very low mass-to-sail-area ratio. Even at the edges of our Solar System, there’s enough sunlight to propel a solar sail spacecraft, so long as the sail is large enough and the mass of the spacecraft is small enough.
This fleet of sentinels would maintain their positions until we detected an incoming ISO. Linares calls them statites, and since they’re stationary, their initial status has zero velocity. That’s part of the trick, and according to a press release, “Once released, the stored energy in the solar sail would leverage the gravitational pull of the sun to slingshot the statite in a freefall trajectory towards the ISO, allowing it to catch up.”
If things went well, the spacecraft could then dispatch a nano-satellite to orbit the ISO, and train its sensors on it. There’d be no need for the main spacecraft to slow down, which would complicate the mission enormously.
“Flyby missions tend to be easier because they don’t require you to slow down — you fly past the object and try to get as many pictures as you can in that window,” says Linares. “A rendezvous mission is harder because you have to slow down and match the speed of the object so you can stay with it for a while. But the longer you can stay around the interstellar object, the better pool of data you can collect. Good science happens up close.”
Linares is not the only behind this concept. There are three other researcheers involved, including Damon Landau at JPL. The team is taking a nine month period to work on their concept. They need to understand if it’s actually feasible or not, and they need to flesh out their concept.
Whether or not this concept could bear fruit, there’s no question about the scientific value of studying and ISO up close.
“Studying an interstellar body close-up would revolutionize our understanding of planet formation and evolution,” said team-member Benjamin Weiss, from the Department of Earth, Atmospheric and Planetary Sciences at MIT. “For the first time, we could obtain sensitive measurements of the bulk composition of other solar systems. We could also learn how quickly and how commonly objects transit between solar systems, which will tell us the feasibility of the interstellar transfer of life.”
NIAC has approved the concept for Phase One, a nine month study to determine viability. If that goes well, NIAC can approve a further Phase Two, then a Phase Three study. That would give the team more time to develop the concept.
NIAC awards are a tricky business. Some ideas might sound far-out at first, so there can be a fine line between fundable, and non-fundable. Would the Apollo mission to the Moon have been funded under NIAC? That’s a fun what-if, thought experiment.
“Winning a NIAC award such as this one is very prestigious, but also very difficult, because the proposer has to walk a fine line between an innovative idea that sounds almost like science fiction while being grounded in real physics,” says Olivier de Weck, a professor of aeronautics and astronautics and of engineering systems at MIT. “Professor Linares and his colleagues have done this perfectly, and this concept will enable the study of ISOs in an unprecedented way by essentially balancing out the two major things we get from our sun in new ways: gravity and radiation.”
There’s been some scientific inquiry into Oumuamua and Comet Borisov. But there wasn’t much time.
About a month ago, a pair of scientists published a paper on Oumuamua. They showed that it could have been ejected from its home solar system after its parent body was torn apart by tidal fragmentation.
Also in April 2020, another paper showed that Comet 2L/Borisov formed in a very cold environment. That paper showed that Borisov contained much more carbon monoxide than comets from our own Solar System.
But these are just tantalizing hints into the nature of interstellar objects.
We are at a disadvantage studying these ISOs, because they come and go so quickly. If Linares and his team can develop a way to study them, then we should do it. It doesn’t sound like it would be an enormously expensive proposition.
If we can leverage our current technology to understand these foreign objects better, we’ll learn more about other solar systems, and how different—or similar— they might be.
And then we’ll be that much less dim-witted. | 0.898537 | 3.488767 |
Scientists Discover a Large Amount of Water in an Exoplanet’s Atmosphere
Much like detectives study fingerprints to identify the culprit, scientists used NASA’s Hubble and Spitzer Space Telescopes to find the “fingerprints” of water in the atmosphere of a hot, bloated, Saturn-mass exoplanet some 700 light-years away. And, they found a lot of water. In fact, the planet, known as WASP-39b, has three times as much water as Saturn does.
Though no planet like this resides in our solar system, WASP-39b can provide new insights into how and where planets form around a star, say researchers. This exoplanet is so unique, it underscores the fact that the more astronomers learn about the complexity of other worlds, the more there is to learn about their origins. This latest observation is a significant step toward characterizing these worlds.
Using Hubble and Spitzer, astronomers analyzed the atmosphere of the “hot Saturn” exoplanet WASP-39b, and they captured the most complete spectrum of an exoplanet’s atmosphere possible with present-day technology. By dissecting starlight filtering through the planet’s atmosphere into its component colors, the team found clear evidence for water vapor. Although the researchers predicted they would see water, they were surprised by how much water they found – three times as much water as Saturn has. This suggests that the planet formed farther out from the star, where it was bombarded by icy material. Credits: Artist’s Concept: NASA, ESA, G. Bacon and A. Feild (STScI), and H. Wakeford (STScI/Univ. of Exeter)
Although the researchers predicted they’d see water, they were surprised by how much water they found in this “hot Saturn.” Because WASP-39b has so much more water than our famously ringed neighbor, it must have formed differently. The amount of water suggests that the planet actually developed far away from the star, where it was bombarded by a lot of icy material. WASP-39b likely had an interesting evolutionary history as it migrated in, taking an epic journey across its planetary system and perhaps obliterating planetary objects in its path.
“We need to look outward so we can understand our own solar system,” explained lead investigator Hannah Wakeford of the Space Telescope Science Institute in Baltimore, Maryland, and the University of Exeter in Devon, United Kingdom. “But exoplanets are showing us that planet formation is more complicated and more confusing than we thought it was. And that’s fantastic!”
Wakeford and her team were able to analyze the atmospheric components of this exoplanet, which is similar in mass to Saturn but profoundly different in many other ways. By dissecting starlight filtering through the planet’s atmosphere into its component colors, the team found clear evidence for water. This water is detected as vapor in the atmosphere.
Using Hubble and Spitzer, the team has captured the most complete spectrum of an exoplanet’s atmosphere possible with present-day technology. “This spectrum is thus far the most beautiful example we have of what a clear exoplanet atmosphere looks like,” said Wakeford.
“WASP-39b shows exoplanets can have much different compositions than those of our solar system,” said co-author David Sing of the University of Exeter in Devon, United Kingdom. “Hopefully this diversity we see in exoplanets will give us clues in figuring out all the different ways a planet can form and evolve.”
Located in the constellation Virgo, WASP-39b whips around a quiet, Sun-like star, called WASP-39, once every four days. The exoplanet is currently positioned more than 20 times closer to its star than Earth is to the Sun. It is tidally locked, meaning it always shows the same face to its star.
Its day-side temperature is a scorching 1,430 degrees Fahrenheit (776.7 degrees Celsius). Powerful winds transport heat from the day-side around the planet, keeping the permanent night-side almost as hot. Although it is called a “hot Saturn,” WASP-39b is not known to have rings. Instead, is has a puffy atmosphere that is free of high-altitude clouds, allowing Wakeford and her team to peer down into its depths.
Looking ahead, Wakeford hopes to use the James Webb Space Telescope — scheduled to launch in 2019 — to get an even more complete spectrum of the exoplanet. Webb will be able to give information about the planet’s atmospheric carbon, which absorbs light at longer, infrared wavelengths than Hubble can see. By understanding the amount of carbon and oxygen in the atmosphere, scientists can learn even more about where and how this planet formed.
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 conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.
Publication: H. R. Wakeford, et al., “The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint,” AJ, 2018; doi:10.3847/1538-3881/aa9e4e
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Crescent ♑ Capricorn
Moon phase on 12 February 2083 Friday is Waning Crescent, 25 days old Moon is in Capricorn.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 9 February 2083 at 16:39.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing first ∠1° of ♑ Capricorn tropical zodiac sector.
Lunar disc appears visually 0% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1943" and ∠1943".
Next Full Moon is the Worm Moon of March 2083 after 19 days on 4 March 2083 at 07:34.
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 25 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 1027 of Meeus index or 1980 from Brown series.
Length of current 1027 lunation is 29 days, 14 hours and 25 minutes. It is 1 hour and 16 minutes shorter than next lunation 1028 length.
Length of current synodic month is 1 hour and 41 minutes longer than the mean length of synodic month, but it is still 5 hours and 22 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠55.2°. At beginning of next synodic month true anomaly will be ∠89.1°. 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°).
4 days after point of perigee on 8 February 2083 at 11:16 in ♏ Scorpio. 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 23 February 2083 at 07:16 in ♉ Taurus.
Moon is 368 980 km (229 274 mi) away from Earth on this date. Moon moves farther next 10 days until apogee, when Earth-Moon distance will reach 404 622 km (251 420 mi).
9 days after its descending node on 3 February 2083 at 00:47 in ♌ Leo, the Moon is following the southern part of its orbit for the next 3 days, until it will cross the ecliptic from South to North in ascending node on 15 February 2083 at 23:06 in ♒ Aquarius.
23 days after beginning of current draconic month in ♒ Aquarius, the Moon is moving from the second to the final part of it.
1 day after previous South standstill on 11 February 2083 at 23:44 in ♐ Sagittarius, when Moon has reached southern declination of ∠-27.496°. Next 13 days the lunar orbit moves northward to face North declination of ∠27.467° in the next northern standstill on 26 February 2083 at 04:43 in ♊ Gemini.
After 4 days on 16 February 2083 at 18:15 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 | 3.103473 |
the solar system
Asteroids are dry, dusty lumps, made of rock, metal, or a mix of both, that orbit the sun. If their paths cross, asteroids can collide, break up, and be set on a path toward Earth. a chunk of asteroid landing on earth is termed a meteorite.
There are over a billion asteroids, and more than 200,000 have been discovered so far. Asteroids are material that failed to form a rocky planet some 4.6 billion years ago when the solar system's planets formed. They are mostly irregular in shape and range in size from several hundred miles across, down to
The Main Belt, the Trojans, and some individual asteroids are shown here. All asteroids orbit close to the planetary plane, in the same direction as the planets. Asteroids in the Main Belt take about 3-6 years to orbit. They spin as they orbit, in just hours.
boulder, pebble, and dust size. About 100 are larger than 125 miles (200 km).
over 90 percent of asteroids are in the main belt, also known as the asteroid belt. Ceres, the largest object in the Main Belt, was reclassified as a dwarf planet in 2006. Although the belt has more than a billion asteroids measuring over 1.25 miles (2 km) long, it is not crowded; thousands of miles separate asteroid from asteroid. the near-earth asteroids have orbits that take them outside the belt. the trojans are two groups that follow Jupiter's orbit, one ahead of the planet, the other behind.
both groups follow Jupiter's orbital period
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Venus last appeared in the morning sky in 2015 and 2016, when it appeared with Mars and Jupiter.
Brilliant Venus zips into the morning sky during April 2017 and dominates the morning sky until year’s end. During this morning appearance, Venus makes close appearances with the star Regulus and the planets Jupiter and Mars.
This chart shows the rising time of bright planets, the moon, and stars near the planets’ orbital plane (ecliptic) compared to sunrise as calculated from U.S. Naval Observatory data for Chicago, Illinois in the Central Time Zone. Additionally, the times when Jupiter sets and Saturn sets are charted compared to sunrise. On April 7, Jupiter is at opposition and it sets in the west at sunrise. The time differences are also displayed for Civil Twilight, Nautical Twilight and Astronomical Twilight. At Astronomical Twilight, the sky is as dark as it gets naturally.
The rising time of Venus is represented by the green line on the chart. It enters the chart in mid-March, reaching its maximum rising time difference during the summer, and leaves the sky in early 2018. Notice that during the summer months of this appearance of Venus, the brilliant planet rises well before the beginning of twilight. It stands low in the eastern sky as the sky brightens.
As Venus appears earlier in the morning sky, Jupiter shines brightly in the western sky, until about May 20 when Jupiter sets as Venus rises. (Notice on the chart, Jupiter sets line crosses the Venus rises at May 20.) After this date Jupiter sets before Venus rises. Similarly, Saturn, while not as bright as Jupiter or Venus, reaches opposition on June 15, setting in the west as Venus rises in the eastern sky. Venus appears in the eastern morning sky and Saturn appears in the western sky until about July 25 when Saturn sets as Venus rises. After this date Saturn sets before Venus rises.
Later in the year, Venus appears near Regulus. This occurs near the date when the rising lines of Regulus and Venus intersect. The same occurs for Mars, Spica, and Jupiter. As Venus moves back into bright sunlight later in the year, it appears near Mercury, Antares and Saturn, although they appear together during bright twilight and out of view for most observers.
Venus has a close conjunction with Mars on October 5, followed by a very close (Epoch) conjunction with Jupiter on November 13.
The moon passes Venus each month, as our nearest celestial neighbor moves through its celestial path. Two dates (May 22 and July 20) are especially noteworthy when Venus and the moon appear about 3.5 degrees apart.
Venus moves between Earth and Sun on March 25, 2017; this is known as inferior conjunction. Since Venus has a shorter orbital path and faster speed, it quickly moves into the morning sky. The red line on the chart shows the division between morning and evening. The line pointing from the earth to the sun indicates noon. So at inferior conjunction, Venus rises with the sun, appears in the south at noon, and sets in the west at sunset.
Venus does not appear in the sky at midnight at mid-northern latitudes. That occurs when a planet is opposite the sun in the sky as seen from Earth. On the chart notice that the midnight line does not point toward Venus.
As Venus reaches this inferior conjunction, it passes above the sun. Because it is north, above the sun, it rises earlier than the sun. On conjunction morning it rises about 40 minutes before the sun. On the rising chart above, it first appears on the chart on March 14, 11 days before it reaches conjunction!
Venus was last at inferior conjunction on August 25, 2015, 589 days between inferior conjunctions.
The planet rapidly moves into the morning sky, rising earlier each morning. It is very close to our planet and sparkles in the morning sky. The brightness is from the proximity of the planet to Earth, its highly reflective clouds and the phase of the planet. (Yes, Venus shows phases when viewed through a telescope.) At this time Venus is about 170 times the moon’s distance, relatively close compared to other planets.
From April 15 through May 13, Venus appears brightest in our skies, with the mid-point on May 1, 2017. This is shown with the GB (greatest brightness) designation on the rising chart above.
Update: This image is from the beginning of the period of peak brightness. Venus rises during twilight during maximum brightness during this appearance.
Venus continues to rise earlier each morning. On the morning of May 22, the crescent moon appears about 3.5 degrees from Venus.
Update May 22: Venus and the moon appear together.
Venus reaches its greatest angular separation (46 degrees) from the sun on June 3. This is shown by the GE symbol (greatest elongation) on the rising chart above. It rises about 2 hours before sun near the beginning of twilight.
Venus Dazzles Morning Sky
Venus continues rising earlier as summer begins.
On July 14, Venus moves past Aldebaran. The closest approach is about 4 degrees.
The Binocular View
Update: Image of Venus and Aldebaran on July 14, 2017. Click the image to see the Hyades and the Pleiades.
More striking is the star cluster near Venus and Aldebaran: Hyades. The Hyades cluster is about 2.5 times farther away than ruddy Aldebaran. Through binoculars, Venus, Aldebaran and the jewel-like stars of the cluster sparkle against the black velvet of the predawn sky. Several dozen stars can be seen.
To the unaided eye, the Hyades resemble a check mark or a letter “V” if Aldebaran is included.
Clusters, like the Hyades, are used to refine distance measuring techniques as well descriptions of the lives of stars. These clusters are thought to form at approximately the same time. Stars that burn their nuclear fuels faster convert into other stellar forms sooner, such as red giants and red super giants. From these stellar models, the estimate of the sun’s total lifespan is about 10 billion years.
Over time these clusters break apart; the gravitational forces between the stars are not strong enough to keep the cluster together. The stars go their own way in their orbital path around the galaxy.
Our sun was likely formed in such a cluster and is now a lone star since it has gone into its own orbit around the Milky Way galaxy.
On the morning of July 20, the crescent moon again appears with Venus. The pair is separated by about 3.5 degrees.
In early August Venus rises about 3 hours before sunrise and begins to rise later each morning as displayed on the rising chart. For the rest of the year, it loses about 30 minutes each month.
On September 1, Venus passes about 1 degree from the Beehive star cluster. Like the Hyades described above, this is a stellar nursery. It is too far away to be easily seen. Binoculars will help with the view. Look around 5:15 a.m. CDT.
In late summer and early Autumn look for Venus and Sirius at the same time. Both are about the same height (altitude) above the eastern horizon. Venus stands in the east-northeast and Sirius appears in the southeast. Only the sun and moon shine brighter than Venus and Sirius is the brightest star in the night sky. See this link to view the last time Venus and Sirius appeared together in the morning sky.
Venus continues its rapid eastward movement as compared to the stars and descent toward the sun’s glow, passing about a half degree from Regulus on September 20. This pair rises about 2 hours before sunrise.
Update: September 20 — Brilliant Morning Star passes about one-half degree from Regulus.
Over a month later, Venus passes Spica. The gap is nearly 4 degrees.
The first planetary conjunction of this appearance is with Mars. On the morning of October 5, Venus passes 0.2 degrees from the Red Planet. The planets are close on a few mornings before and after the conjunction.
For more about Mars’ appearance during 2017-2019, see this article.
Update: October 5, 2017, Venus-Mars conjunction
Venus-Jupiter Epoch Conjunction
Update: Venus-Jupiter conjunction, November 13, 2017
Another Epoch (close) Conjunction of Venus and Jupiter occurs before sunrise on November 13. The distance is about .2 degrees. This conjunction is visible during twilight as the pair rises about 70 minutes before the sun.
The next conjunction between the pair is January 22, 2019 with the next epoch conjunction on April 30, 2022.
For more about the Venus-Jupiter Epoch Conjunction, see this article.
Venus continues its rapid descent into bright sunlight. Conjunctions occur with Mercury, Antares and Saturn, but they occur in bright twilight, out of the view of most observers.
On January 9, 2018 passes behind the sun at its superior conjunction and reappears in the evening sky.
The moon appears with Venus on the following dates:
April 23: 8 degrees
May 22: 3.5 degrees (See description in text)
June 20: 7 degrees
July 20: 3.5 degrees (See description in text)
August 19: 4.5 degrees
September 17: 6 degrees
September 18: 6 degrees
October 18: 5.5 degrees
Venus on April 2, 2017
Venus: May 8, 2017 (Even visible from the brightest city lights)
Venus: June 21, 2017
Venus: July 14, 2017
Venus: August 2, 2017
Venus: August 13, 2017
Venus, Sirius and Procyon: September 3, 2017
Venus, Regulus and Mercury: September 11, 2017
Venus, Sirius, the moon, and bright morning stars: September 15, 2017
Venus, Regulus, Mercury & Mars: September 15, 2017
Venus-Regulus conjunction: September 20, 2017
Venus: September 23, 2017
Venus, Mars & Regulus: September 25, 2017
Venus, Mars & Regulus: September 28, 2017
Venus and Mars, 3 degrees apart: September 30, 2017
Venus and Mars, 2.5 degrees apart, October 1, 2017.
Venus and Mars, 1.75 degrees apart, 3 days after conjunction, October 8, 2017.
Venus and Mars, 6.5 degrees apart, October 16, 2018.
Venus, October 20, 2017.
Venus, October 26, 2017
Venus and Jupiter, November 10, 2017
Venus and Jupiter, November 14, 2017
Venus provides a dazzling view of planetary, stellar and conjunctions during its morning appearance in 2017. | 0.906432 | 3.66655 |
Crossing the Borders: Discovery of Pluto
Story of Pluto discovery is truely a defining moment in astronomy: That incident opened a broader window to our Solar System exploration and ultimately allowed scientists to further understand how Solar System is formed and working. Nevertheless, this story is certainly an entertaining one when you find out how many little chances positioned Pluto to be discovered!
Almost 90 years before now, that was a thrilling news spread worldwide while the world was trying to recover from a world war and running for the next one. Those were the times when US was taking bigger steps on science and astronomy. And a young amateur American astronomer was about to make history.
Interested in ancient stories? Jump over! We will take you to a journey in the dustbin of history.
Still not interested? We did our best!
Jump down to answers of “Frequently Asked Questions” in the end of this article.
Background of Pluto Discovery
None of the discoveries in the history of science happens by snapping a finger. While systematic discovery of our neighbours in the sky has a history of hundreds of years, first step of direct discovery was probably one person raising the head up. She/he was probably just trying to understand what those shining things are..
Actually the history of science goes back to the collective memory of humanity, but this attitude could be ruining it. We don’t want that! 🙂
In any case we don’t need to go back that far since noone can see Pluto from Earth with bare eyes.
Discovery of Neptune – The First Step
However, we can easily go back to discovery of Neptune in 1846. Why would we do that? Because an important and new method was used for finding out new planets: Neptune was discovered by estimating its gravitational influence on Uranus orbit. And Neptune was found very close to where it was estimated to be with that practice.
So this was really remarkable because Newton’s gravitational laws were sufficiently working for planets as well!
New findings have always led to new questions in terms of science. And this time it was a simple one: Could there be more planets beyond Neptune?
Jacques Babinet was the first person to follow orbital path of Neptune and to search for similar disturbance. It was 2 years after the discovery and he had the chance to observe only a small portion of Neptune‘s complete orbit around Sun (which is 165 years). That’s why it was not that easy to conclude for him at that time. Although he estimated extremely bigger influence in the orbit, he still concluded that a much more bigger ninth planet was out there. In that aspect, he was substantially right.
Percival Lowell and Lowell Observatory In Search for Ninth Planet
Together with the end of 1800’s and beginning of 1900’s, more astronomers were interested in locating the next planetary target. And the name standing out in this search was Percival Lowell. He was an amateur astronomer and decided to build his own observatory in 1894, especially for observing Mars.
From 1906 till his death in 1916, Percival Lowell was mainly interested in perturbations on Neptune’s orbit. His calculations were indicating that there should have been a planet much more bigger than Earth farther than Neptune.
Percival Lowell died in 1916, but his legacy about Planet X was ready to be taken over!
Following Mr. Lowell’s death, the task and the observatory was stopped for a long time because of some legal issues. After 11 years in 1927, his brother A. Lawrance Lowell was luckily able to settle things down and made the observatory up and running. What is more, from 1927 to 1929, he was able to provide installation of a new telescope; which was going to be a part of planetary discoveries.
Clyde Tombaugh Steps In to Lowell Observatory
The observatory was back, funds were back and they had a new telescope. Time to cook the soup! It was time to initiate the program of finding Planet X.
The staff started working on this, but in short while the board understood that this is a job to handle with better focus and decided that a dedicated person should better deal with this mission.
On January 1929, a 24-years-old farmer and an amateur astronomer named Clyde William Tombaugh applied to Lowell Observatory with his hand sketches which he adapted from his observations from his own telescope. Lowell management were impressed by his sketches and hired him for this specific job with a $125 monthly salary. You will see how efficient his price/performance was!
His duty was to focus on a specific range of area in the night sky, store sky images on photographic plates and compare them with bare eyes.
Discovery of Pluto Takes Place!
Before Clyde Tombaugh was hired and even before the Lowell Observatory was re-established, no human being including the astronomers themselves: Gustaf Stromberg and Nicholas U Mayall knew that Pluto was already imaged in 1925. That’s another interesting story..
While that story remained as a secret for everyone, Clyde Tombaugh was working on his night duties photographing the night sky based on the clues from Percival Lowell‘s calculations.
In less than a year, Tombaugh took two different photos of the night sky on 23 and 29 January where Pluto was smiling to the cameras! The night sky views were carved on photographic plates and those plates were on the shelves. Eventually someone had to locate if something was there!
That was another duty of Tombaugh and on 18 February 1930, he realized that he already got it previous month. That is Pluto!
As Tombaugh located the new planet of the century, the board of observatory considered to observe the planet more and gather more information before making it public. Meanwhile they decided to wait until 13 March 1930, Percival Lowell‘s birthday to announce to the world that the 9th planet was discovered.
The announcement ceremony took place in Ashurst Hall where about 500 people were ready on their seats. Astronomer Carl Lampland was the person announcing the discovery. The hall was not very convenient for such audience and Lowell Observatory states as follows: “Unfortunately, few, if any, of the audience members heard this important message, since the soft-spoken Lampland could not be heard in the echo-filled, uncarpeted room”.
After The Pluto Discovery – A Newspaper Gallery
That was a big news, and the word was spread fast!
We have a collection of newspapers for you: Printed right after the discovery of Pluto. Sources for all images are seperately stated in the end of this article.
Scientific Background of Pluto Discovery
The reason it only took less than a year for Clyde Tombaugh to locate Pluto is known to be the legacy of Percival Lowell. He was a pioneer calculating the effects of a potential Planet X (that was the name of the “Wanted” planet those times). And his calculations were leading to a specific area where such planet should have approximately been on that phase of the orbit.
However, at this point there are some discrepancies: Pre-discovery calculations about Pluto did not quite match with reality. Percival Lowell’s calculations had an error margin hundreds of times more than the ones for Neptune. That was a huge difference, it worked well for Neptune after all!
How is that possible? Let’s find out.
Pluto was initially (beginning of 1900’s) estimated to have a mass 7 times bigger than Earth’s. Right after the discovery, it was stated that its mass is almost same with the mass of Earth. And now we know Pluto’s mass is 1/456 times of Earth.
What is more, Pluto was about 10 times fainter than it was predicted and was located within 6 degrees from where it was estimated to be.
This Pluto fact leads to something else: Scientists are still looking for a much more bigger Planet X in the outer Solar System. And for sure besides any kind of calculation errors, what Percival Lowell tried to find was not Pluto itself. He was probably trying to locate another Planet X which might be the one scientists of this era are still working on. And this subject still remains as a mystery!
We can easily conclude that either Mr. Lowell was looking for another planet or his calculations were wrong! Pluto was discovered while another planet was searched. Pluto was discovered by luck!
How Was Pluto Discovered? The Method of Discovery
It wasn’t easy to be an astronomer on first half of 1900’s. Because they did not have computers, they did not have any complex electronic devices. What they only had were bare eyes, mechanical devices and modern science of that era. Can you imagine how hard it can be to locate a pale planet billions of kilometers away while you don’t exactly know where it is?
As human found different ways of photography, not much time lost before directing the lenses to the sky. And for sure thousands of people did it before Clyde Tombaugh. However as mentioned earlier, you can not see Pluto light with your bare eyes or take its photo with an ordinary machine.
The method for spotting Pluto was as follows:
- Take pictures from different night skies on every possible day
- Compare pictures from different days.
- Than check if there is a light source moving or not.
Because the stars are incredibly far from our home, you can not observe them shifting positions in few days. This enables astronomers tracking Solar System Objects easily.
On those two images from 23 and 29 January 1930, one can detect only a single light source moving and that was our naughty planet Pluto where rest of the stable light sources were of other stars. Pluto was moving extremely slow and this easily eliminated the possibility of being a nearby asteroid. That was certainly a Trans-Neptunian planet!
How Was Pluto Discovered? Technical Details About Photographic Plates
Let’s go further into details about Tombaugh’s work in search for Planet Nine.
As stated above, Tombaugh was reflecting the telescopic images to photographic plates and looking for signs of moving light sources on them.
We can call above mentioned mechanism a specialized microscope. That device provided user to make comparisons on photographic plates. Those plates were 36×43 centimeters wide and the exposures were taken by a telescopic camera with a 33 centimeter diameter lens.
For easy comparison of images on two different plates of different dates, Tombaugh had a device called blink comparator which let user flip mirrors of different images on another easily.
Discovery of Pluto and Its Consequences
Pluto was the first planet discovered 84 years after Neptune. And those were the days when we were not quite sure about Solar System formation. You can clearly see that from the statements on above pieces of newspapers.
Besides that, Pluto was the first planet detected beyond the gas giants, and it meant a lot: As scientists had more understanding, it was realized that Pluto was not alone in that area: There was a huge disk made of thousands of icy rocks which was later going to be called Kuiper Belt. And Kuiper Belt was going to tell a lot more about formation of Solar System.
Above all, knowing how coincidentally Pluto was discovered in the bed of stars and its effects on astronomical comprehension clarifies the importance of finding that small pale dot: PLUTO.
Here is the part where you can find quick answers to your basic questions about discovery of Pluto. Please let us know in case you have further questions.
- When was Pluto discovered?
- Discovery date of Pluto is 18 February 1930.
- Who discovered Pluto?
- Clyde William Tombaugh was the discoverer.
- Where was Pluto discovered?
- Discovery of Pluto took place in Lowell Observatory, Flagstaff, AZ. The observatory is still open for visiting.
- How was Pluto discovered?
- Pluto was discovered by observing a specific range of night sky view on different days, recording thoses views on photographic plates and comparing those views. As the background stars are basically “stable”, possibly moving light sources belong to the planets or asteroids. Since Pluto was far away and moving respectively slower, discovery of Pluto: a planet beyond Neptune was easily confirmed.
- Pluto Safari
- Lowell Observatory
- 14 May 2015, David DeVorkin, “Finding Pluto With the Blink Comparator“
Link: ( https://airandspace.si.edu/stories/editorial/finding-pluto-blink-comparator )
- Vandebilt University Lecture Notes “Astronomy 201: The Solar System“, Spring 2003
- Newspaper sources:
- We aim to build a proper Pluto encyclopedia and your contributions are highly appreciated!
- Any deficiencies on this article? Please type to below comment box or contact us from this link. We are ready to check and clarify. | 0.849562 | 3.13267 |
A newly published study details the discovery of a new class of “hypervelocity stars” – stars that are moving at speeds of more than a million miles per hour relative to the Milky Way and that are fast enough to escape gravitational grasp of the Milky Way.
An international team of astronomers has discovered a surprising new class of “hypervelocity stars” – solitary stars moving fast enough to escape the gravitational grasp of the Milky Way galaxy.
“These new hypervelocity stars are very different from the ones that have been discovered previously,” said Vanderbilt University graduate student Lauren Palladino, lead author on the study. “The original hypervelocity stars are large blue stars and appear to have originated from the galactic center. Our new stars are relatively small – about the size of the sun – and the surprising part is that none of them appear to come from the galactic core.”
The discovery came as Palladino, working under the supervision of Kelly Holley-Bockelmann, assistant professor of astronomy at Vanderbilt, was mapping the Milky Way by calculating the orbits of Sun-like stars in the Sloan Digital Sky Survey, a massive census of the stars and galaxies in a region covering nearly one quarter of the sky.
“It’s very hard to kick a star out of the galaxy,” said Holley-Bockelmann. “The most commonly accepted mechanism for doing so involves interacting with the supermassive black hole at the galactic core. That means when you trace the star back to its birthplace, it comes from the center of our galaxy. None of these hypervelocity stars come from the center, which implies that there is an unexpected new class of hypervelocity star, one with a different ejection mechanism.”
Astrophysicists calculate that a star must get a million-plus mile-per-hour kick relative to the motion of the galaxy to reach escape velocity. They also estimate that the Milky Way’s central black hole has a mass equivalent to four million suns, large enough to produce a gravitational force strong enough to accelerate stars to hyper velocities. The typical scenario involves a binary pair of stars that get caught in the black hole’s grip. As one of the stars spirals in toward the black hole, its companion is flung outward at a tremendous velocity. So far, 18 giant blue hypervelocity stars have been found that could have been produced by such a mechanism.
Now Palladino and her colleagues have discovered an additional 20 sun-sized stars that they characterize as possible hypervelocity stars. “One caveat concerns the known errors in measuring stellar motions,” she said. “To get the speed of a star, you have to measure the position really accurately over decades. If the position is measured badly a few times over that long time interval, it can seem to move a lot faster than it really does. We did several statistical tests to increase the accuracy of our estimates. So we think that, although some of our candidates may be flukes, the majority are real.”
The astronomers are following up with additional observations.
The new rogues appear to have the same composition as normal disk stars, so the astronomers do not think that their birthplace was in the galaxy’s central bulge, the halo that surrounds it, or in some other exotic place outside the galaxy.
“The big question is: what boosted these stars up to such extreme velocities? We are working on that now,” said Holley-Bockelmann. | 0.823508 | 3.986317 |
The Hubble telescope is a space telescope, which was launched in the year 1990 to orbits the Earth. Its position above the atmosphere, that blocks and Deforms the light which reaches the Earth, gives it a view of the Universe which typically far surpasses that of ground based telescopes. The Hubble telescope is NASA’s one of the longest lasting and most successful science missions. By shedding light on many of the huge mysteries of astronomy, it has beamed thousands of images back to the Earth. Its look has helped in finding the identity of quasars, the existence of dark energy and the age of the Universe.
The discoveries of Hubble have changed the way scientists look at the Universe. Its aptitude to show the Universe in extraordinary detail has turned astronomical assumption into concrete confidence. Among its many inventions, Hubble has exposed the age of the Universe to be about 13 to 14 billion years. It is much more accurate than the old range of wherever from 10 to 20 billion years. The Hubble has played an important role in the discovery of dark energy; it is a mysterious force which accelerates the universe to go faster. It has also shown galaxies to scientists in all the stages of evolution. It also shows toddler galaxies which were around when the universe was still young. It helps the scientist to understand how galaxies form. Around young stars, it found clumps of gas, Protoplanetary discs and dust, probably perform as birthing grounds for new planets. The absolute amount of astronomy based on observations of Hubble has also helped in making it one of the most important observatories of history. The policies which govern the telescope have contributed to its unbelievable output.
The telescope is an instrument for the whole community of astronomers. In the world, any astronomer can submit a request time and proposal on the telescope. Then, the teams of experts select the observations to be performed. Once observations are finished and before the data are released to the whole scientific community, the astronomers have a year to practice their work.
From the earliest days of the invention of the telescope, it has faced many problems. But, the Hubble space telescope is the direct solution to this problem. Shifting air pockets in the atmosphere of the earth deform the view of the telescope on the ground. The atmosphere also incompletely absorbs and blocks the certain wavelength of radiation, such as X-rays, Gamma-rays and ultraviolet rays, before they reach the Earth. Scientists can have an excellent view of an object such as star by studying it in all the kinds of wavelength which it emits.
Work of Hubble Telescope
The Hubble telescope completes a spin around the Earth in every 97 minutes, by moving at the speed of about 8 km per second. In about 10 minutes, this speed is fast enough to travel across the United States. As it travels, the mirror of Hubble captures light and directs it into the several instruments of science. Actually, it is kind of telescope, which is known as a Cassegrain reflector. Light hits the primary mirror or main mirror of the telescope. It bounces off the primary mirror and comes across a secondary mirror. Through a hole in the center of the primary mirror, the secondary mirror focuses the light which leads to the science instruments on the telescope.
Often, people by mistake, believe that a power of telescope lies in the capacity to magnify objects. Actually, telescopes work by gathering more light than the human eye can capture on its own. The vision and light of the telescope depend on its mirror. The larger the mirror of the telescope, it can collect more light and its vision will also better. The size of Hubble’s primary mirror is 94.5 inches in diameter. The mirror of the Hubble is small and is compared with those of present ground based telescopes, which can be about 1000 cm and up. But, the location of Hubble, further than the atmosphere gives it amazing clarity.
Once, the mirror of the Hubble captures the light, its science instruments work individually or together to provide the observation. To examine the universe, each instrument is designed in a different way.
The wide field camera 3 (WFC3): – It sees three different types of light, near infrared, visible and near ultraviolet, while not at the same time. As compared to other instruments of Hubble, its resolution and field of view is much greater. The wide field camera 3 is one of Hubble’s new instruments and it will also be used to study dark matter and dark energy.
The Cosmic Origins spectrograph (COS): – The other new instrument of Hubble is a Spectrograph which completely sees in ultraviolet light. They act something like a prism and separates light from the cosmos into its constituent colors. COS will improve ultraviolet sensitivity of Hubble at least 10 times and when observing extra weak objects it will improve up to 70 times.
The advanced camera for survey (ACS): – This camera sees visible lights. It is intended to study some of the earliest doings in the Universe. ACS is helpful in detecting the most far-away objects in the Universe, it studies the development of a group of galaxies and it also searches for huge planets. Due to an electrical shot in the year 2007, it partially stopped working. But, in 4 May 2009, it was repaired during the servicing mission.
The space Telescope Imaging Spectrograph (STIS): – It is a Spectrograph, which sees visible, near infrared and ultraviolet light and it is known for its capability to chase black holes. It can map out larger objects such as galaxies. On 3 August 2003, due to technical failure, it stopped working. But, during the servicing mission 4, it was also repaired.
The Near Infrared Camera and Multi-object Spectrometer (NICMOS): – It is a heat sensor of Hubble. Its sensitivity to infrared light, perceived as heat by humans. It observes objects which are hidden by interstellar dust, such as stellar birth sites. And also look into deepest space.
In the year 1923, the first idea for the space telescope was arise. One of the founders of the rocketry, the German scientist Hermann Oberth, suggested to blasting a telescope into space aboard a rocket. The Space Telescope science institute was established in the year 1981, to manage the science program and to assess the proposals for telescope time. After the American Astronomer Edwin Hubble, the space telescope was changed into the Hubble space telescope. | 0.80754 | 3.785805 |
New Five-Planet Solar System Found by Citizen Scientists Using Kepler Data
We tend to think that scientific breakthroughs can only come from visionaries and crack teams of highly skilled, specialized researchers. And though that's often still the case, the Internet-savvy age we live in leaves ample opportunities for collaboration, along with endless outlets for the exchange of ideas, data and research.
The Exoplanet Explorers citizen scientist project, the brainchild UC Santa Cruz astronomer Ian Crossfield and Caltech staff scientist Jessie Christiansen, began its search for new planets on crowdsourcing research platform Zooniverse. But it was a feature on the ABC Australia television series Stargazing Live that ultimately yielded the most new data from citizens. Within two days of introducing the project on television, Exoplanet Explorers received over 2 million classifications from over 10,000 citizen scientists.
As citizens contributing to the Exoplanet Explorers shared, K2 had a whole new field of stars that might host planets, contained in a dataset called C12 that no astronomer had yet thought to look through.
Sorting through the upvoted, crowdsourced data, Christiansen eventually found a star with four planets orbiting it. Christainsen and the Expoplanet Explorers had stumbled upon the first system of exo-planets that was discovered entirely by crowdsourcing. They named the system K2-138.
These planets are orbiting in a resonance, a mathematical term for when each planet takes almost exactly 50 percent longer to orbit the star than the next planet further in. A fifth planet was also discovered on the same chain, with hints of a sixth as well.
"Some current theories suggest that planets form by a chaotic scattering of rock and gas and other material in the early stages of the planetary system's life," Christiansen said. "However, these theories are unlikely to result in such a closely packed, orderly system as K2-138," says Christiansen. "What's exciting is that we found this unusual system with the help of the general public."
The Kepler telescope continues to be instrumental in the discovery of new worlds. Last year, NASA announced that the telescope had discovered 1,284 new exoplanets by measuring the process of transit, when a planet passes in front of a star as viewed from Earth. Of those 1,284 new exoplanets, nine might support life.
Kepler's past discoveries included 100 new expoplanets in 2016, and a whopping 715 in 2014. As of last year, all these discoveries added up to 3,200 verified exoplanets on our star maps, 21 of which potentially support life. We can now add the Kepler's newest discoveries to the list. | 0.874986 | 3.198676 |
August 10, 2017 report
Jupiter-mass planet orbiting giant star discovered
(Phys.org)—An international team of astronomers has discovered a Jupiter-mass alien world circling a giant star known as HD 208897. The newly detected exoplanet was found as a result of high-precision radial velocity measurements. The discovery was detailed in a paper published Aug. 6 on the arXiv preprint server.
HD 208897 is a giant star of spectral type K0, located some 210 light years away from the Earth. It is about five times larger than our sun and has a mass of approximately 1.25 solar masses. The star is metal rich and at the early phase of ascent along the red giant branch. "Our stellar parameters indicate that HD 208897 is a metal-rich star that is at the base of RGB phase," the scientists wrote in the paper.
HD 208897 was one of the targets of an extensive observational campaign carried out from 2007 to 2017, the main goal of which is to search for substellar companions and planets around 50 evolved G and K-type stars. As a result of this survey, a group of researchers led by Mesut Yilmaz of the Ankara University, Turkey, found that 13 of the targets, including HD 208897, show significant radial velocity variations.
The researchers acquired 73 spectra of HD 208897 using the Coude Echelle Spectrograph (CES) installed on the 1.5-meter Russian-Turkish Telescope (RTT150) at TÜBİTAK National Observatory (TUG) in Antalya, Turkey. They also conducted follow-up spectroscopic observations of this star with the 1.88-meter telescope and the High Dispersion Echelle Spectrograph (HIDES) high-efficiency fiberfeeding system (HIDES-F) at the Okayama Astrophysical Observatory (OAO) in Japan. Moreover, the team observed the star photometrically at the Ankara University Kreiken Observatory (AUKR) to check photometric variability or detect any transit phenomena.
The long-lasting observational campaign allowed the astronomers to find a periodic signal, suggesting the presence of an unseen and probably low-mass companion of HD 208897.
"In this work, we report the first planet discovery around a giant star HD 208897 in our planet search program using the RTT150 and 1.88 m telescope at OAO," the paper reads.
The researchers revealed that the newly found planet has a minimum mass of 1.4 Jupiter masses. It is located at a distance of about 1.05 AU from the star and circles its host every 353 days. Notably, the extrasolar world has a nearly circular orbit.
According to the authors of the paper, their study demonstrates that it is possible to detect such lower mass planets in the range of Jupiter, even around giant stars, if long-term observations are carried out. They also emphasize the importance of the finding for our understanding of planet formation scenarios.
"This discovery will be important in understanding the planet formation around metal-rich intermediate-mass stars and the effect of stellar evolution on the planetary system configuration," the researchers concluded.
A Jupiter-mass planet around the K0 giant HD 208897, arXiv:1708.01895 [astro-ph.SR] https://arxiv.org/abs/1708.01895
For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G,K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements for the giant star HD 208897 using an iodine (I2) absorption cell. The measurements were made at T"UB.ITAK National Observatory (TUG, RTT150) and Okayama Astrophysical Observatory (OAO). For the origin of the periodic variation seen in the RV data of the star, we adopted a Keplerian motion caused by an unseen companion. We found that the star hosts a planet with a minimum mass of m2sini=1.40MJ, which is relatively low compared to those of known planets orbiting evolved intermediate-mass stars. The planet is in a nearly circular orbit with a period of P=353 days at about 1 AU distance from the host star. The star is metal rich and located at the early phase of ascent along the red giant branch. The photometric observations of the star at Ankara University Kreiken Observatory (AUKR) and the HIPPARCOS photometry show no sign of variation with periods associated with the RV variation. Neither bisector velocity analysis nor analysis of the Ca II and Halpha lines shows any correlation with the RV measurements.
© 2017 Phys.org | 0.832023 | 3.692895 |
It may seem hard to remember now, with thousands of planets of various types and sizes discovered throughout the galaxy, but back in the 1990s, the field of detecting exoplanets was still in its infancy, and the tools used to look for them were too. Now, an instrument first imagined to look for distant worlds is helping uncover hidden details on this one—and it owes much of its development to NASA funding.
Arsen Hajian builds small but mighty spectrometers—he likes to say his company’s hyperspectral imagers pack the high resolution of machines nearly 30 times larger and as much as 10 times more expensive. He founded his latest company in 2015 but has been working on spectrometers for more than 20 years.
“Back when Arsen was first working on some of this stuff, exoplanets were really something of a new field,” recalls Goddard Space Flight Center astrophysicist Stephen Rinehart. “People were looking for them using radial spectroscopy”—a technique using measurements of a star’s wobble to infer the presence of a planet tugging back at its sun. Although spectroscopy had been around since the 1800s, the existing tools weren’t precise enough to get the results astronomers wanted. Hajian was one of the engineers working to make better ones.
Rinehart, who has been unofficially collaborating with Hajian off and on since the two went to graduate school together, works on instrumentation for NASA’s Observational Cosmology Lab. “I focus on what kind of mission or instrument we need for the next bit of science: how to design it, what does it need to do, and then work on building it,” he says.
That expertise has offered him the opportunity to work on a range of missions from the Hubble Space Telescope to, most recently, the Transiting Exoplanet Survey Satellite (TESS), and has brought him back to Hajian’s spectrometers as he considers the next big space telescope.
In recent years, astronomers have moved away from radial spectroscopy, instead favoring a technique using photometric transits—catching the faint dimming of a star that comes when a planet passes between it and the observer. But Rinehart thinks the next-generation telescopes may combine the two techniques into transit spectroscopy, which could help “astronomers get some clues to what the atmosphere of the exoplanet is like.”
If NASA decides to go that route, he says, “we will want to build the biggest telescope we can, using the smallest spectrometer we can, which is where Arsen’s tool comes in.”
Although Hajian’s company, Hindsight Imaging Inc., is young, the technology is based on a discovery the physicist made decades earlier at the U.S. Naval Observatory—with funding from NASA.
Many scientists get Government grants through the National Science Foundation, Hajian says, but as a Government employee, he was discouraged from applying for those. Instead, he turned to funding mechanisms available from NASA, including both the Advanced Technology Initiative (ATI) and ROSES, or Research Opportunities in Space and Earth Sciences.
“Basically, all of my funding during my 13 years at the Naval Observatory came either from the Navy, NASA, or corporations,” Hajian recalls. The grants funded his efforts to build better spectrometers for star cataloging and exoplanet detection, of interest to both the Navy and NASA.
But his big breakthrough came in large part because his training was in another field altogether, he says: “I’m a radio astronomer by training; nobody taught me optics.”
Most spectrometers are either small and low-resolution or very large but high-powered, following what Hajian calls “one of the basic rules of optics: a telephoto lens (typically long and bulky) magnifies the image, while a fisheye lens (typically much smaller) demagnifies.”
But since radio astronomy doesn’t require that tradeoff, Hajian was open to looking for a different approach. He found one, essentially adding two extra reflecting surfaces to the standard optical design to change the shape of the light as it enters from a round point to a long and skinny ellipse, without changing the focal ratio.
The result? “We got around that law. It allowed us to build spectrometers that are a bit more than three times smaller in all three directions than conventional instruments. It saves on volume by a factor of about 30.”
The breakthrough, which Hajian has patented, didn’t happen all at once, but the NASA-funded work he did at the Naval Observatory gave him an important foundation for the work that came later. “The whole point was learning how to build spectrometers and understanding the problems that needed to be solved,” Hajian says.
“A lot of times it felt like beating your head against the wall: what makes a spectrometer good or bad, and how is it connected to all of the other things that matter? That took me a long time to figure out. Then figuring out how to build it took me less time.”
For now, Boston-based Hindsight mainly sells spectrometers as components to be integrated into larger instruments, and the company has quickly amassed “a wide variety of customers in multiple spectrometry markets,” Hajian says.
In the small but growing precision agriculture market, spectroscopy can be used to look for invasive species or for signs of plant disease, Hajian says, or to help farmers see precisely where they fertilized yesterday and where they didn’t.
Hindsight spectrometers are also integrated into devices that look for chemical explosives and monitor the content of medications. Both applications measure the spectrum of light absorbed, reflected, and emitted by a sample and compare it to the spectra of known substances, but they are packaged differently and use different software.
In mid-2017, the company also released its first two complete spectroscopy systems, one for detecting drugs and explosives at a short distance and another for detecting skin cancer. “The reason we have these two specific devices is because there is a lot of customer interest,” Hajian says. Hindsight already had orders for both, he added.
Down the road, he envisions game-changing medical advances from optical spectroscopy, including using spectrometers like his melanoma-detecting device to diagnose tumors underneath the skin, eliminating or reducing the need for biopsies.
He’s also working on devices that could replace traditional laboratory blood tests: “What we’re trying to do is deploy products where you look at a drop of blood or look at it through the skin, and right there you find out what is in your blood,” he explains.
The sky’s the limit, he says, for his devices. “In moderate volumes, our prices come down to affordable price points that are not possible with conventional technology. That opens up lots of opportunities, because if you can make it cheap and light and easy to use, it can fly off the shelves.”
And indeed, notes Rinehart, the sky’s no limit for applications at NASA. Beyond using the spectrometers on future space telescopes, another idea he is exploring is taking a small spectrometer, like what Hindsight is making, and putting it on a high-altitude balloon, to look for exoplanets and their atmospheric composition from near space.
That would put the instruments above 99 percent of the atmosphere, Rinehart says, which isn’t as good as 100 percent but would be a far less expensive way to “pick off the low-hanging fruit.”
And it wouldn’t be possible without a high-powered, very compact spectrometer. “This has always been the direction Hajian’s been going. He’s been working with the basic concepts for over 20 years now, coming up with better ways of doing things.” | 0.814751 | 3.839644 |
University of California San Diego researchers in the Department of Physics have shed light on the formation of supermassive black holes and galaxies. The research by Professor Shelley Wright, graduate student Andrey Vayner and their colleagues outlines the physics surrounding the formation of black holes and galaxies, improving scientific understanding of how the two grow in unison. Their findings, published in the Dec. 20, 2017 issue of Astrophysical Journal directly impact theoretical work on supermassive black holes’ and galaxies’ formation and evolution through cosmic time. Their work also provides important new clues on how black holes impact the star formation history of galaxies.
“Supermassive black holes are captivating,” acknowledged Wright, adding that their relationship to forming galaxies has puzzled astronomers for decades. “Understanding why and how galaxies are influenced by the supermassive black holes they harbor is an outstanding puzzle in their formation.”
These bright, vigorous supermassive black holes are known as “quasars.” Wright and Vayner—who led the research and served as first author on the paper titled, “Galactic-scale Feedback Observed in the 3C 298 Quasar Host Galaxy”—examined the energetics surrounding the powerful quasar-generated winds. Their measurements place the distant supermassive black hole and galaxy named 3C 298 at approximately 9.3 billion light years away.
“We study supermassive black holes in the very early universe when they are actively growing by accreting massive amounts of gaseous material,” explained Wright. “While black holes themselves do not emit light, the gaseous material they chew on is heated to extreme temperatures making them the most luminous objects in the universe.”
According to Wright, the team’s research revealed that the winds blow out through the entire galaxy and impact the growth of stars. “This is remarkable that the supermassive black hole is able to impact stars forming at such large distances,” she noted.
Today, neighboring galaxies show that the galaxy mass is tightly correlated with the supermassive black hole mass. Wright’s and Vayner’s research indicates that 3C 298 does not fall within this normal scaling relationship between nearby galaxies and the supermassive black holes that lurk at their center. But, in the early universe, their study shows that the 3C 298 galaxy is 100 times less massive than it should be given its behemoth supermassive black hole mass. This implies that the supermassive black hole mass is established well before the galaxy, and potentially the energetics from the quasar are capable of controlling the growth of the galaxy.
To conduct the study, the UC San Diego researchers utilized multiple state-of-the-art astronomical facilities. The first of these was the W. M. Keck Observatory instrument OSIRIS and its advanced adaptive optics (AO) system. An AO system allows ground-based telescopes to achieve higher quality images by correcting for the blurring caused by Earth’s atmosphere. The resulting images are as good as those obtained from space. The second major facility was the Atacama Large Millimeter/submillimeter Array, known as “ALMA,” an international observatory in Chile that is able to detect millimeter wavelengths using up to 66 antennae to achieve high resolution images of the gas surrounding the quasar.
“The most enjoyable part of researching this galaxy has been putting together all the data from different wavelengths and techniques,” said Vayner. “Each new dataset that we obtained on this galaxy answered one question and helped us put some of the pieces of the puzzle together. However, at the same time it created new questions about the nature of galaxy and supermassive black hole formation.”
Wright agreed, commenting that the data sets were “tremendously gorgeous” from both Keck Observatory and ALMA, offering a wealth of new information about the universe.
These findings are the first results from a larger survey of distant quasars and their energetics’ impact on star formation and galaxy growth. Vayner and his team will continue developing results on more distant quasars using the new facilities and capabilities from Keck Observatory and ALMA.
The Department of Physics’ graduate program in the Division of Physical Sciences at UC San Diego is listed #16 according to U.S. News and World Report rankings. The first students to enroll at UC San Diego in 1960 were graduate students in physics. | 0.817892 | 4.062966 |
The monster black hole that anchors our galaxy is safely 28,000 light years away from Earth. That’s a good thing, too. The region around that back hole is overflowing with dangerous radiation and fragmented stars. Astronomers observing the center of the Milky Way have spotted some unusual features that drive home just how violent the area is. The galaxy sports a pair of gargantuan “X-ray chimneys” that expel the matter and energy building up around the black hole.
UCLA professor of astronomy and astrophysics Mark Morris, who contributed to the research, likens the features to exhaust vents, bleeding off energy from the galaxy in the form of X-rays. The international team looked to the black hole, known as Sagittarius A* (pronounced “Sagittarius A Star”) in an effort to learn more about star formation in the Milky Way. All galaxies foster the development of stars, but the rate of new star formation can vary wildly. The fate of the matter and energy spiraling toward a galaxy’s central black hole can be a significant factor in star formation.
To track the material blasted out around Sagittarius A*, the researchers turned to the European Space Agency’s XMM-Newton satellite. This X-ray observatory launched almost 20 years ago, but it’s still going strong. The team used data from 2012, as well as 2016 to 2018 to see what the black hole was doing with all the stars getting smashed to bits in its general vicinity.
According to the researchers, Sagittarius A* produces “chimneys” of X-ray that extend north and south from the disk of the galaxy. The structures are more appropriately known as Fermi bubbles, massive cavities carved out of the gas cloud surrounding the galaxy. The north and south chimney both start within 160 light years of the black hole, extending outward about 25,000 light years. That’s almost the distance from Sagittarius A* to Earth.
The black hole in our galaxy is about 4 million times the size of the sun, but other galaxies have central black holes that are much larger. We can study the Milky Way close up, which could provide insights into how these more energetic galaxies work. Understanding how energy moves through the chimneys and into surrounding space could help explain why some regions become rich in star formation, and others are relatively barren.
- Hypervelocity Star Flung Out of Milky Way May Have Unusual Origin
- Gaia Spacecraft Creates Map of More Than 1 Billion Stars in Our Galaxy
- Scientists will try to directly image Sagittarius A*, the black hole at the center of the Milky Way | 0.816846 | 3.996825 |
Kepler-16 is another great discovery coming from the Kepler telescope, the 10th NASA Discovery mission which is devoted to finding Earth-size exoplanets by monitoring variations of brightness due to transit. Today the Kepler team found a circumbinary exoplanet, an exoplanet orbiting a binary star system. Did they find Tatooine?
In the large 105 deg2 field of view of the Kepler spacecraft, ~156,000 stars are being almost continuously observed by the 0.95m telescope. In 2010, the star number KIC 12644769 of the Kepler Input Catalog quickly got the attention of the Kepler team when they realized that it was an eclipsing binary star system, one of 1,879 detected after 44 days of operation. Binary stars, or pairs of stars orbiting around their center of mass, are common in our galaxy. It is now thought that 30% of stars are part of multiple systems. So the discovery of an eclipsing binary system is interesting but not such a big deal, until something else appeared around this late-K and M-dwarf star system. In a second catalog published in March 2011 and available on arXiv, the Kepler team gave a hint of their discovery. They mentioned the detection of a secondary event with a smaller intensity (<2%), suggesting that a sub-stellar object (aka an exoplanet) could be orbiting this binary system located 200 light-years from us.
Today an article published in Science reports the discovery of a Saturn-size (0.75 x RJupiter) planet orbiting this binary star system. A team led by Laurance Doyle, a researcher at the SETI Institute, shows that Kepler captured 3 revolutions of this exoplanet around the close-binary star system, meaning that 6 transits (3 per star) were recorded. After carefully inspecting the timing of these attenuations, they realized that the observed deviation of approximately 1 minute is due to the gravitational attraction of a third body less massive than Jupiter.
The masses, sizes and orbital elements of the binary star system (Kepler-16 A & B) and its exoplanet, named Kepler-16 (AB)-b (or b), were determined by developing a dynamical model able to fit the length and depth of the Kepler transit as well as additional radial-velocity observations recorded with the Tillinghast 1.5m telescope on Mt. Hopkins, Arizona. The two binary stars of the system, which are smaller and less massive than our Sun (0.69 & 0.20 x Msun for Kepler-16 A & B respectively), revolve around their center of mass at 0.22 AU. The binary system has a significantly eccentric orbit (e~0.16) with a period of 41.1 days. The exoplanet, Kepler-16 (AB)-b, has a circular orbit with a radius of 0.7 AU (the distance of Venus-Sun), also around the center of mass of the binary star system, in 229 days. Its mass (0.33 MJupiter), radius (0.75x RJupiter), and density (0.964 g/cc) are well constrained as well.
There is no equivalent in our solar system of such a large and dense exoplanet. Kepler-16b has the same size as Saturn but a higher density, suggesting that it could be made of a core of ice/rock (half its size) surrounded by an atmosphere in a configuration similar to Saturn in size but with a larger core. So this is not Tatooine, the mythical planet of the Star Wars movies, since it has no “surface” where Luke Skywalker or some carbon-based lifeform equivalent could trek. But you can imagine that the view from the exoplanet, or from one of its moons, would be striking since you would see a large orange star (Dang~1 deg so twice the apparent size of our Sun with a peak temperature at 0.65 um) and a smaller (Dang~ 20 arcmin, so smaller than our Sun) and fainter red star companion orbiting around each other in 41 days. Quite often, you would have two sunsets and two sunrises per day. Could it be any more romantic?
Without knowing much about the planet’s atmosphere, it is not possible to know its temperature, but the authors of the article estimated that it would be a cold world with a maximum temperature of ~200 K (-73° C, -100° F). This would not be very adequate for life forms as we know them in our solar system. But the real point of this discovery is that exoplanets around multiple systems, or circumbinary exoplanets, do exist.
It has been already suggested that CM Draconis, an eclipsing binary composed of two red dwarf stars, could have a large exoplanet, more massive than Jupiter, at 5 AU due to small timing variations in the eclipses. Anomalies in the orbital period of the eclipsing binary HW Vir were also explained by the presence of sub-stellar companions (19 and 8 x MJupiter) around the binary stars.
However, this new work has revealed, without a doubt, the existence of an exoplanet around a binary star system. Due to the unprecedented quality of the Kepler data, it has been possible to characterize both the stars and the exoplanet and determine their masses.
This is just a beginning. How this system, which is made of extremely coplanar objects, formed and evolved due to mutual perturbations will definitely get a lot of attention from observers and modelers alike. If you are an astronomer living in China or Russia, you should be able to photometrically observe one of the planetary transits on June 28, 2012. The Kepler team was indeed lucky to catch these planetary transits since the current orbital model predicts that they will cease to be visible from Earth in 2014 & 2018 for Kepler 16B and Kepler 16A respectively.
I discussed the results with my SETI Institute colleague Laurance Doyle, who was obviously excited by this discovery. On his office board, I could see a long list of KOI (Kepler Object of Interest) targets and some interesting diagrams showing different kind of multiple systems. He mentioned to me that Kepler has captured more of those circumbinary, or even circumternary, exoplanets. Kepler-16 gave them the opportunity to better understand the signal that they should expect from those systems, refining their search algorithm by looking for specific signatures such as a shift in the timing. So we should be ready for more of these planets around multiple stars, and they will force us to reinvent scenarios to explain the formation of planetary systems.
The authors finish the Science paper by mentioning that Kepler-16 “is a treasure for both exoplanetary and stellar astrophysical investigations”. I will add that it is also a challenge for our imagination and our research. This is a great time for astronomy, and students who are now thinking of joining us in this quest for life beyond Earth should realize how lucky they are to witness the post-Kepler astronomy era. | 0.847566 | 3.970838 |
Olivin-phyric Shergottites: SAU 090, SAU 125, NWA 1775, SAU 130, NWA 1068 Louise Michele, SAU 005-008, DAG 476, Dhofar 019.
Synonyms: picritic shergottites
General: The members of this group are named for Shergotty, an achondrite that fell in India, in 1865. Originally grouped with the HED group, it took more than a century to recognize the martian origin for Shergotty, and a few related falls and finds. More recently, it became more than obvious that the shergottites represent a rather heterogenous group, and thus subgroups were designed to comprise members with similar mineralogies, and formation histories. The subgroup of the olivine-phyric shergottites represents the youngest of these three groups, and maybe one of the most interesting classes of martian meteorites.
Description: Typically light to dark greenish rocks with more or less dull black fusion crusts. Most desert finds are devoid of remnant crust, and they are hard to distinguish from terrestrial igneous rocks. As the name implies, olivine-phyric shergottites all exhibit porphyritic textures of large olivine-crystals (phenocrysts) set in a fine-grained basaltic groundmass.
Mineralogy: Olivine-phyric shergottites are primarily composed of olivine phenocrysts set in a basaltic groundmass of pigeonite, plagioclase shock-converted to maskelynite, minor augite, and olivine. Accessory minerals are chromite, merrillite, ilmenite, ulvöspinel, and pyrrhotite. Due to some differences in mineralogy, the olivine-phyric shergottites are subdivided into the original olivine-phyric group, and the olivine-orthopyroxene-phyric group. The members of the latter group exhibit - often preferentially oriented - pyroxene phenocrysts besides the typical olivine phenocrysts.
Formation history: Considering the links between the basaltic and lherzolitic shergottites, older theories suggested that the olivine-phyric shergottites represent intermediate forms between these two groups. It was thought that they were formed through partial melting of lherzolitic and other source rocks, resulting in a magma that crystallized within an extruded lava flow near the martian surface. However, more recent studies suggest that the olivine-phyric shergottites formed from independent, olivine-saturated magmas on Mars that might have been parental to basaltic shergottites, making the olivine-phyric shergottites precursors of their younger basaltic cousins.
Origin: Planetary. Comparisons between various characteristics of the members of the SNC group, and data obtained about Mars by space probes and landers, such as Viking, Pathfinder, and the new Mars rovers Spirit and Opportinity, have provided strong proof for the martian origin of the SNCs, and today it is widely accepted that these achondrites actually represent genuine Mars rocks that have been blasted off of the surface of the Red Planet by major impacts. Recent studies suggest that most shergottites were probably derived from a few larger impacts in the Tharsis region of Mars, and Olympus Mons, the largest volcano in our solar system.
Members: Today, 9 distinct olivine-phyric shergottites are known, most of them having been recovered from the hot deserts of Africa, and Oman. Typical examples include Dar al Gani 476, the first Mars meteorite from the hot deserts, Dhofar 019, NWA 1068 (and its pairings, e.g. NWA 1775), as well as SaU 005/008, the largest Mars meteorite, with its pairings SaU 090, SaU 125, and SaU 130. | 0.830061 | 3.667202 |
I've seen many designs for creating artificial gravity within a habitat in space by rotating the habitat about a central axis. With today's science, can artificial gravity be generated in a vehicle, or habitat, that would mimic the gravity of earth (1-g)?
Short answer: No, we cannot create a stationary habitat that has a gravity-like force that does not depend on motion.
When we "feel" the force of gravity, what we actually feel is the ground pushing up on us. This is called the "Normal Force", and is a result of Newton's Third Law. The normal force you feel is the result of the Earth beneath you pushing you up and supporting your weight. However, if you were to go skydiving, when you jump out of a plane, there is nothing to support you, so you do not feel any force. You are in free fall. This is what the astronauts feel as they orbit the Earth.
When you're in a spinning space station, your inertia causes your body to want to move in a straight line. This is Newton's First Law. However, as your body tries to move in a straight line, it meets the wall of the space station, which is curving beneath you. The space station's wall resists you, and creates a normal force, which you feel like gravity. Imagine you are in a car that suddenly turns to the right. When it turns, you feel a "force" which pulls you to the left. This is your inertia, resisting the acceleration of the car. You press against the wall of the car, which presses back on you.
One way to recreate this without having a rotating system is by using a constantly, linearly accelerating vehicle, like a rocket. By firing its thrusters, the rocket would essentially push all of the occupants forward, creating a normal force, which you could interpret as a gravitational force. It's just like when you're in a car at a stoplight; when the car accelerates, you feel a "force" pushing you back in your seat.
However, having a rocket that is constantly accelerating would (a) require lots of fuel and (b) soon leave the solar system. Neither is good for a long-term space station. A rotating space station, however, is pretty easy, because once we spin the station up, there is nothing to slow it back down. Having a rotating system on another planet or moon, however, is a lot more difficult, for a host of reasons. The primary reason, however, is that the speed at which the station (or parts of it) would have to be rotating to create a 1g force is extremely high. (A similar question was asked here.)
Because gravity is, in a sense, the result of an object's inertia, there is no way we can create a gravity-like force without having the object undergo some form of acceleration, whether that be rotational or linear. SciFi movies, like Star Wars and Star Trek, where they have "artificial gravity generators" are entirely fictional, and we have no way of creating one with our understanding of physics.
A different explanation can be found here.
The answer is yes. Create a vehicle inside a hollow, stationary, radiation shield - about one-mile in diameter. Have the vehicle run on a magnetically-levitated track around the inside perimeter of the hollow tube. At the proper velocity artificial gravity, (even 1-g) can be produced inside the moving vehicle. Another similar vehicle could run on a separate track to match velocities and on-load, or off-load people or materials to the first vehicle. The vehicles could be pressurized to create conditions similar to an environment at sea-level on earth. This could be done on a moon, another planet, or in space. | 0.846509 | 3.516598 |
Earth Orbit, Solar Insolation Variability & Sea Level Change
Take look at the graphs in Figure 4.10, showing changes in sea level through the history of the Earth. The top figure covers 35 million years, the middle one covers a little more than 5 million years, and the bottom one zooms in to the past 500,000 years. What do you notice? Is there a regularity in the pattern of sea level ups and downs?
Through Earth’s history, there appears to have been a regular spacing of glacial maximum events, at roughly 120 thousand years (ky). When variations in Earth's orbit produce repetitive changes in climate and sea level, the observed cycles are often referred to as Milankovitch Cycles. Many sedimentary rock sequences have been shown to have stacking patterns that reflect these time scales, as do ice core data.
Mathematician Milutin Milankovitch proposed an explanation for the changes in the way the Earth orbits the sun. These changes define the sequence of ice ages and warm periods.
- The Earth’s orbit changes from being nearly circular to slightly elliptical (eccentricity). This cycle is affected by other planets in the solar system and has a period of around 100,000 years.
- The angle of tilt of the Earth’s axis changes from 22.1° to 24.5° (obliquity). This cycle has a period of 41,000 years.
- The direction of the tilt of the axis changes (precession) on a cycle of 26,000 years.
- These changes influence the length of the seasons and the amount of solar radiation received by the Earth.
Please watch this short video for a review of the Milankovitch cycles, if you are not already familiar.
Click for "5 Minutes Milankovitch Cycles Explanation" video transcript.
The Sun is the Earth's main energy source. In fact, it provides 99.96 percent of all the energy that drives the Earth's climate. Some of the energy produced by nuclear fusion in the sun's interior will eventually strike the top of the Earth's atmosphere. The amount of energy that does strike the atmosphere depends on two main factors: the total amount of energy produced and transmitted by the Sun, and the orbital cycles of the Earth with respect to the Sun. The energy transmitted by the Sun is in a constant state of flux depending on solar activities such as sunspots, solar flares, coronal loops, and coronal mass ejections. The relationship between the Earth's orbital cycles and climate change was proposed by Milutin Milankovitch. Milankovitch was a Serbian engineer, and during the 1930s, he proposed that the changes in the intensity of solar irradiation received on the Earth were affected by three fundamental factors: precession, obliquity, and eccentricity. These factors are now collectively known as the Milankovitch cycles. The Milankovitch cycles are widely accepted by climate change scientists and are well documented by, for example, the IPCC. A more detailed description of the cycles is available by clicking on the tab above, but the remainder of this video will provide an excellent overview. The Earth rotates on its axis every 24 hours. Around once in 27 days, the Sun also rotates on its axis. Its average distance from the Earth is approximately 150 million kilometers (93 million miles). It is an average distance because this Earth's orbit around the Sun is not fixed. Its orbit cycles from being almost a circle to that of an ellipse to almost a circle again. The cycle takes place over a period of around 100,000 years. The rotation of the Earth is at an angle to the vertical, and this angle changes over time. It moves from 22.1 degrees to 24.5 degrees and back again. This is over a time span of approximately 41,000 years. The Earth also goes through a cyclic wobble. It moves from its current position of the north pointing to the star Polaris to where the North points to the star Vega and returns to pointing at Polaris. The full cycle takes place between 19 to 26 thousand years. The combined effects caused the seasons to gradually cycle relative to the perihelion and aphelion, this over a time span of about 21 thousand years.[music]
How do these variations in Earth’s orbit affect climate and sea level? Collectively, variations in Earth's orbit (eccentricity, obliquity, and precession) can either reinforce signatures of cooling or warming, or they can work to counteract each other and produce less severe or ameliorated climate change. When the multiple variables reinforce each other, the amount of climate change and, as a result, sea level change can be significant. | 0.833605 | 3.653594 |
Planck was launched on 14 May 2009 on an Ariane 5 along with ESA’s Herschel infrared observatory. The mission was designed to study the Cosmic Microwave Background (CMB), the relic radiation from the Big Bang, with an accuracy defined by fundamental astrophysical limits.
At launch, the Herschel-Planck combination measured approximately 11 m high and 4.5 m wide, with a weight of about 5.7 tonnes. They separated soon after launch and headed into different orbits. The two spacecraft operated independently.
If Planck has been placed in orbit around Earth, heat from our planet, the Moon and the Sun would have interfered with its instruments, reducing their sensitivity. Instead, the telescope orbited the second Lagrange point of the Earth-Sun system (L2), a point in space located 1.5 million km from Earth. L2 has the important property that a spacecraft there can stay fixed in the Earth-Sun system and is situated on Earth’s night-side.
It was an excellent location for Planck: the satellite avoided unwanted emission from the Earth, Moon and Sun, which would otherwise confuse the signal from the CMB. Because Earth and the Sun are in the same general direction, it also offered good sky visibility for astronomical observations. In addition, this orbit kept Planck outside Earth’s radiation belts, which could have disturbed observations.
For more information, see L2, the second Lagrangian point.
It took Planck about 60 days to enter its final operational orbit around L2. The observatory settled into an orbit that resembles a halo around L2, with an average amplitude of | 0.862405 | 3.721031 |
In a lab buried under the Apennine Mountains of Italy, Elena Aprile, a professor of physics at Columbia University, is racing to unearth what would be one of the biggest discoveries in physics.
She has not yet succeeded, even after more than a decade of work. Then again, nobody else has, either.
Aprile leads the XENON dark matter experiment, one of several competing efforts to detect a particle responsible for the astrophysical peculiarities that are collectively attributed to dark matter. These include stars that rotate around the cores of galaxies as if pulled by invisible mass, excessive warping of space around large galaxy clusters, and the leopard-print pattern of hot and cold spots in the early universe.
For decades, the most popular explanation for such phenomena was that dark matter is made of as-yet undiscovered weakly interacting massive particles, known as WIMPs. These WIMPs would only rarely leave an imprint on the more familiar everyday matter.
That paradigm has recently been under fire. The Large Hadron Collider located at the CERN laboratory near Geneva has not yet found anything to support the existence of WIMPs. Other particles, less studied, could also do the trick. Dark matter’s astrophysical effects might even be caused by modifications of gravity, with no need for the missing stuff at all.
The most stringent WIMP searches have been done using Aprile’s strategy: Pour plenty of liquid xenon—a noble element like helium or neon, but heavier—into a vat. Shield it from cosmic rays, which would inundate the detector with spurious signals. Then wait for a passing WIMP to bang into a xenon atom’s nucleus. Once it does, capture out the tiny flash of light that should result.
These experiments use progressively larger tanks of liquid xenon that the researchers believe should be able to catch the occasional passing WIMP. Each successive search without a discovery shows that WIMPs, if they exist, must be lighter or less prone to leave a mark on normal matter than had been assumed.
In recent years, Aprile’s team has vied with two close competitors for the title of Most-thorough WIMP Search: LUX, the Large Underground Xenon experiment, a U.S.-based group that split from her team in 2007, and PandaX, the Particle and Astrophysical Xenon experiment, a Chinese group that broke away in 2009. Both collaborators-turned-rivals also use liquid-xenon detectors and similar technology. Soon, though, Aprile expects her team to be firmly on top: The third-generation XENON experiment—larger than before, with three and a half metric tons of xenon to catch passing WIMPs—has been running since the spring, and is now taking data. A final upgrade is planned for the early 2020s.
The game can’t go on forever, though. The scientists will eventually hit astrophysical bedrock: The experiments will become sensitive enough to pick up neutrinos from space, flooding the particle detectors with noise. If WIMPs haven’t been detected by that point, Aprile plans to stop and rethink where else to look.
Aprile splits her time between her native Italy and New York City, where in 1986 she became the first female professor of physics at Columbia University. Quanta caught up with her on a Saturday morning in her Brooklyn high-rise apartment that faces toward the Statue of Liberty. An edited and condensed version of the interview follows.
QUANTA MAGAZINE: How closely do you follow the theoretical back and forth about the nature of dark matter?
ELENA APRILE: For me, driving the technology, driving the detector, making it the best detector is what makes it exciting. The point right now is that in a couple of years, maybe four or five in total, we will definitely say there is no WIMP or we will discover something.
I don’t care much about what the theorists say. I go on with my experiment. The idea of the WIMP is clearly today still quite ideal. Nobody could tell you “No, you’re crazy looking for a WIMP.”
What do you imagine will happen over the next few years in this search?
If we find a signal, we have to go even faster and build a larger scale detector which we are planning already—in order to have a chance to see more of them, and have a chance to build up the statistics. If we see nothing after a year or two, the same story.
The plan for the collaboration, for me and how I drive these 130 people, is very clear for the next four or five years. But beyond that, we will go almost to the level that we start really to see neutrinos. If we end up being lucky—if a supernova goes off next to us and we see neutrinos—we will not have found dark matter, but still detect something very exciting.
How did you get started with this xenon detector technology?
I started my career as a summer student at CERN. Carlo Rubbia was a professor at Harvard and also a physicist at CERN. He proposed a liquid-argon TPC—time projection chamber. This was hugely exciting as a detector because you can measure precisely the energy of a particle, and you can measure the location of the interaction, and you can do tracking. So, that was my first experience, to build the first liquid-argon ‘baby’ detector—1977, yes, that’s when it started. And then I went to Harvard, and I did my early work with Rubbia on liquid argon. That was the seed that led eventually to the monstrous, huge liquid-argon detector called ICARUS.
Later, I left Rubbia and I accepted the position of assistant professor here at Columbia. I got interested in continuing with liquid-argon detectors, but for neutrino detection from submarines. I got my first grant from DARPA [the Defense Advanced Research Projects Agency]. They didn’t give a damn about supernova neutrinos, but they wanted to see neutrinos from the [nuclear] Russian submarines. And then we had Supernova 1987A, and I made a proposal to fly a liquid-argon telescope on a high-altitude balloon to detect the gamma rays from this supernova.
I studied a lot—the properties of argon, krypton, xenon—and then it became clear that xenon is a much more promising material for gamma-ray detection. So I turned my attention to liquid xenon for gamma-ray astrophysics.
How did that swerve into a search for dark matter?
I had this idea that this detector I built for gamma-ray astrophysics could have been, in another version, ideal to look for dark matter. I said to myself: “Maybe it’s worth going into this field. The question is hot, and maybe we have the right tool to finally make some progress.”
It’s atypical that the NSF [National Science Foundation], for someone new like me, will fund the proposal right away. It was the strength of what I had done all those years with the a liquid-xenon TPC for gamma-ray astrophysics. They realized that this woman can do it. Not because I’m very bold and I proposed a very aggressive program—which of course is typical of me—but I think it was the work that we did for another purpose which gave the strength to the XENON program, which I proposed in 2001 to the NSF.
What was it like to go from launching high-altitude balloons to working underground?
We had quite a few balloon campaigns. It’s something that I would do again, and I didn’t appreciate it then. You get your detector ready, you sit it on this gondola. At some point you are ready, but you can’t do anything because every morning you go and you wait for the weather guy to tell you if it’s the right moment to fly. In that scenario you are a slave to something bigger than you, which you can’t do anything about. You go on the launch pad, you look at the guy measuring, checking everything, and he says “No.”
Underground, I guess, there is no such major thing holding you from operating your detector. But there are still, in the back of your mind, thoughts about the seismic resilience of what you designed and what you built.
In a 2011 interview with The New York Times about women at the top of their scientific fields, you described the life of a scientist as tough, competitive and constantly exposed. You suggested that if one of your daughters aspired to be a scientist you would want her to be made of titanium. What did you mean by that?
Maybe I shouldn’t demand this of every woman in science or physics. It’s true that it might not be fair to ask that everyone is made of titanium. But we must face it—in building or running this new experiment—there is going to be a lot of pressure sometimes. It’s on every student, every postdoc, every one of us: Try to go fast and get the results, and work day and night if you want to get there. You can go on medical leave or disability, but the WIMP is not waiting for you. Somebody else is going to get it, right? This is what I mean when I say you have to be strong.
Going after something like this, it’s not a 9-to-5 job. I wouldn’t discourage anyone at the beginning to try. But then once you start, you cannot just pretend that this is just a normal job. This is not a normal job. It’s not a job. It’s a quest.
In another interview, with the Italian newspaper La Repubblica, you discussed having a brilliant but demanding mentor in Carlo Rubbia, who won the Nobel Prize for Physics in 1984. What was that relationship like?
It made me of titanium, probably. You have to imagine this 23-year-old young woman from Italy ending up at CERN as a summer student in the group of this guy. Even today, I would still be scared if I were that person. Carlo exudes confidence. I was just intimidated.
He would keep pushing you beyond the state that is even possible: “It’s all about the science; it’s all about the goal. How the hell you get there I don’t care: If you’re not sleeping, if you’re not eating, if you don’t have time to sleep with your husband for a month, who cares? You have a baby to feed? Find some way.” Since I survived that period I knew that I was made a bit of titanium, let’s put it that way. I did learn to contain my tears. This is a person you don’t want to show weakness to.
Now, 30 years after going off to start your own lab, how does the experience of having worked with him inform the scientist you are today, the leader of XENON?
For a long time, he was still involved in his liquid-argon effort. He would still tell me, “What are you doing with xenon; you have to turn to argon.” It has taken me many years to get over this Rubbia fear, for many reasons, probably—even if I don’t admit it. But now I feel very strong. I can face him and say: “Hey, your liquid-argon detector isn’t working. Mine is working.”
I decided I want to be a more practical person. Most guys are naive. All these guys are naive. A lot of things he did and does are exceptional, yes, but building a successful experiment is not something you do alone. This is a team effort and you must be able to work well with your team. Alone, I wouldn’t get anywhere. Everybody counts. It doesn’t matter that we build a beautiful machine: I don’t believe in machines. We are going to get this damn thing out of it. We’re going to get the most out of the thing that we built with our brains, with the brains of our students and postdocs who really look at this data. We want to respect each one of them.
Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences. | 0.879654 | 4.138052 |
Three billion years ago, Earth was a very different place. The Sun that shone on its oceans and continents was not as bright as it is today, and rather than the oxygen-rich atmosphere humans need to survive, methane played a much bigger role in the gas layer that encased our young planet. Despite their differences, this early Earth and our current one have something important in common: they could both support life.
For much of its existence, Earth has been inhabited. But if researchers remotely analyzed the atmosphere of that young Earth, they might have missed the evidence for life.
“The Earth has been many different things,” says Timothy Lyons, a professor in the Department of Earth and Planetary Sciences at the University of California, Riverside. “It is a remarkable story that our planet has maintained habitability for so long.”
Lyons heads up the NASA Astrobiology Institute’s “Alternative Earths” team, in which researchers are characterizing the Earth during different stages in its 4.5-billion-year existence.
“We’re looking at Earth’s past to refine our ability to look for biosignatures [the chemical fingerprints of life] beyond our planet and Solar System,” he says. “It is extrasolar planets that interest us most.”
Currently, there are more than 4,000 known exoplanets and thousands more awaiting confirmation. Scientists are developing remote methods to see if those planets are potentially habitable and maybe even inhabited. The signatures of any distant life will most likely be found in the gases belonging to the atmosphere of an exoplanet.
The changing Earth
While Earth is the only place in the Universe known to harbor life, there are many other previous, alternative versions of our home planet, as it changed throughout time, which also allowed life to survive and thrive.
“For more than four billion years, Earth has had oceans, and we’ve had life for most of that time, yet Earth has changed so profoundly throughout its history,” says Lyons.
Through the Alternative Earths research program, the team is able to “take this collected knowledge of the different states of our habitable and inhabited planet and extend this understanding higher – literally – to the atmosphere of a distant planet.”
By combining data from the geology, chemistry, and biology of Earth’s continents, oceans, and atmospheres from different time periods, the Alternative Earths team is modeling what the atmospheres of these early Earths would have looked like based, in part, on relationships with life in the underlying oceans. This ability to model ancient atmospheres and extend the lessons learned to atmospheres around distant planets is vital to the hunt for potentially habitable planets beyond our Solar System.
“The Earth has taught us many different lessons already,” Lyons says. “[Our research] is not looking for another Earth per se. It’s more about looking for the different pieces of what it is to be a planet that can sustain life. Once you know what those processes do on a planet like Earth, you can assemble them into countless other planetary scenarios that may or may not be able to do the same thing.”
Specifically, the team is investigating three different ancient Earths by collecting data from rocks to create a picture of the geology, chemistry, and biology of the planet at those times. The chapters of particular interest span from 3.2 to 2.4 billion years ago, when the earliest forms of life began to release oxygen into the atmosphere via photosynthesis; 2.4 to 2.0 billion years ago, when the ‘Great Oxidation Event’ occurred and oxygen flooded Earth’s atmosphere and oceans; and 2.0 billion to 500 million years ago, when life became increasingly complex, setting the stage for the organisms that would evolve to become the creatures that inhabit Earth today.
“Understanding the evolution of our own planet, including stages of remarkable stability as well as episodes of turmoil, is an essential first step towards understanding the diversity of habitable planets and life that we may encounter in the Universe,” says team member Stephanie Olson of the University of Chicago. Olson specializes in the interaction between the ocean and atmosphere of early Earth.
Blueprints for habitability
Researchers can also tweak their planetary models to create an infinite number of blueprints for possibly habitable exoplanets. For example, they can use models that can speed up the planet’s rotation, adjust the tilt of its axis, put all of the continents in one hemisphere (or remove them completely), or allow one side of the planet to face its star continuously. Continents are an integral component of oceans’ habitability. Through the weathering of land surfaces, nutrients enter the oceans to nourish the life within them, and the positions and elevations of these landmasses alter how these nutrients move to and through the oceans.
“These factors also influence the communication between the ocean and the atmosphere, and thus the detectability of life in the ocean,” Olson says. “Understanding how planetary parameters influence biological activity and ocean–atmosphere connectivity can help identify the most promising targets for exoplanet life detection that will be least vulnerable to biosignature false negatives.”
The possibility of false negatives – when there is actually life on an exoplanet but the signatures of that life escape detection – fascinates the Alternative Earths team.
In a 2017 paper led by Chris Reinhard at Georgia Tech, the Alternative Earths team flagged the danger of false negatives in the hunt for habitable planets. The presence of both methane and oxygen in an atmosphere has been viewed as a gold standard in the search for distant life. These two gases should not coexist in appreciable amounts, as they react rapidly with each other, but living organisms can constantly replenish them in the atmosphere, allowing this disequilibrium to persist.
However, if researchers were looking at early Earth over most, if not all, of its history, they may not have been able to detect both methane and oxygen in the ancient atmosphere, despite life being present for much of that time.
“[Detecting] atmospheric methane would have been problematic for most of the last ~2.5 billion years of Earth’s history,” Reinhard and colleagues write. For rocky worlds with oceans, such as Earth, these gases could be recycled within the oceans, rather than being detectable in the atmosphere. This possibility implies that “planets most conducive to the development and maintenance of a pervasive biosphere, such as those with weathering continents and vast oceans, will often be challenging to characterize using conventional atmospheric biosignatures”, they write.
Additionally, even if both oxygen and methane are present, they are not necessarily products of life.
Oxygen can be the result of photosynthesis, and microbes produce methane, but they can also form through photochemical and geological processes. In fact, the NASA Astrobiology Institute has a team investigating methane production via geological rather than biological reactions.
“The products of those reactions could sustain life on an ocean world, but the gases themselves may have nothing to do with life,” Lyons says. “You cannot evaluate what the gases mean without a rigorous context.”
“We typically view habitability as binary: a planet can either support life or it cannot, but there likely exists a spectrum of habitability,” adds Olson.
A proxy for oxygen
Researchers within the Alternative Earths team are combining what they know of the different states of our planet and using their data and associated computer simulations to generate examples of what chemical fingerprints, or synthetic spectra, scientists should be looking for around exoplanets.
Lyons points to ozone and seasonality as particularly important in the search for life on other planets.
“We’re big fans of ozone [O3] because it can be more easily detected by spectroscopic techniques than [molecular] oxygen [O2]” he says. “We want to look for ozone and its temporal variability as a proxy for O2 and its seasonality.”
The discovery of possible false negatives using traditional life-detection methods has pushed the team to think of new and perhaps even more robust signs of life. “That’s been the most fun part,” says Lyons.
While O2 may have been difficult to detect remotely from young Earth, ozone, which forms from O2, may not have been. This is only one example of the many ways in which Earth’s history informs our choice of possible exoplanetary targets for life detection.
However, if astrobiologists want to be able to look for ozone on exoplanets, they need to push for these experiments to be included on future missions.
“We’re only starting to get data from other planets,” Lyons says. “To acquire the right data from these planets in the future, we need to start planning now.” | 0.876776 | 3.833979 |
Venus is classified as a terrestrial planet and is sometimes called Earth's "sister planet" owing to their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth). It is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. Venus has the densest atmosphere of the four terrestrial planets, consisting mostly of carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K, Venus is by far the hottest planet in the Solar System. It has no carbon cycle to lock carbon back into rocks and surface features, nor does it seem to have any organic life to absorb it in biomass. Venus is believed to have previously possessed oceans, but these vaporized as the temperature rose due to the runaway greenhouse effect. The water has most probably photodissociated, and, because of the lack of a planetary magnetic field, the free hydrogen has been swept into interplanetary space by the solar wind. Venus's surface is a dry desertscape interspersed with slab-like rocks and periodically refreshed by volcanism.
|Adjective||Venusian or (rarely) Cytherean, Venerean|
|Semi-major axis||*108,208,000 km
|Orbital period||*224.698 day*0.615 190 yr
|Synodic period||583.92 days|
|Average orbital speed||35.02 km/s|
|Inclination||*3.394 58° to Ecliptic*3.86° to Sun’s equator|
|Longitude of ascending node||76.678°|
|Argument of perihelion||55.186°|
|Mean radius||*6,051.8 ± 1.0 km
|Surface area||*4.60×108 km2
|Mass||*4.868 5×1024 kg
|Mean density||5.243 g/cm3|
|Equatorial surface gravity||*8.87 m/s2*0.904 g|
|Escape velocity||10.36 km/s|
|Sidereal rotation period||−243.018 5 day (Retrograde)|
|Equatorial rotation velocity||6.52 km/h (1.81 m/s)|
|North pole right ascension||*18 h 11 min 2 s
|North pole declination||67.16°|
|Apparent magnitude||*brightest −4.9 (crescent)
|Surface pressure||93 bar (9.3 MPa)|
|Composition||*~96.5% carbon dioxide*~3.5% nitrogen|
Venus was the third destination of Earth Explorers and settlers right after The Ascent. (First Luna then Marsand then Venus) The first manned expedition took place in 2093, only a week after the first manned expedition to Mars. Josef Golgov of United Earth Territory Russia insisted on being called a Cosmonaut and he christened the first base on Venus Venera City, honoring the first Human probes launched by the Soviet Union in 1961.
Venus today is the most densely populated planet in the Sol System. 9 Billion Inhabitants call Venus home, while another 12 Million commute to the Planet everyday from around the Sol System but mostly from Earth. (by Transmatter Tunnel, System Tram and InterSystem Shuttles and Taxies) Unlike Mars no real Terra Formingefforts have been made and even tough technology exists to change Venus in a Garden world, Venusians have always voted against Terra Firming every time the subject came up. Twenty of the 56 Towns and cities are Domed Surface cities and the rest is underground.
Venus has the biggest planet based Space Port in the Sol System ( The largest Port is of course Sol Hub)
Venus is famous for its Zoo. Venera City Zoo (or simply Venus Zoo) is the largest most elaborate zoological facility in the known Universe with a unrivalled collection of life specimen of non sentient life forms. More than 1,500,000 Zoo keepers 55,000 Zoologists and 1,200,000 Janitors, Specialists and Technicians take care of nearly 20 Million specimen and over 50 Million life visitors annually. (In addition to countless virtual tours) everything on Venus revolves around |Zoology, Botany and Biology. The Zoo grew out of the Collection of the Neugruber Zoological Institute that is still on Venus. The University of Venusturns out the finest biologists and Zoologists. Companies on Venus manufacture Animal and pet foods, specialized Zoological Equipment and Bio-lab equipment. There are specimen dealers, Exotic Specimen dealers, Animal and Plant brokers, Zoo Facility Planers, Zoo Exhibit Construction Companies. Animal and Life From research institutes. In Gagarin City is the largest collection of Microbes and Bacteria (With a special Virus Section on a special Space Station around Venus) It is both a Mecca for Scientists and a High Secure area with special Safety conditions found in no other city.
Venus is represented as Planet in the Assembly only since 3500 , it was until then “a region of Terra”. The classical definition of Venus as a female Planet was attempted several times by small usually female movements but never gained enough traction to make any cultural changes. Except for Aphrodite City, which maintains an Female Only population and does not allow male residents. It did not last long and the “Aphrodite Movement” and the City almost died out, it was revived by a clever marketing company (Subdivision of DeNoir) and is again a Female Only City, but is a tourist attraction theme park with adult entertainment themes only (Minors are not admitted) that is almost as popular as the Zoo.
Venus is part of the Sol System Association Government based on Ceres and has a local Council for civil matters. Most of the Council is hired and are paid employees. The Five Venus Magistratesleading the Council are elected every 4 years from a pool of candidates by all Venusians. ( Magistrate Zoo, Magistrate Commerce, Magistrate Civil Services, Magistrate Civil Order, Magistrate Civil Engineering) The Planet is represented by a Representative that is a paid Employee of the Venusian Council. The Planet maintains Union Laws but has an extensive Local Ordinance Catalogue especially dealing with licensing and permits of life-form transfer, storage, display and such topics. There is a Special Court of the UnionJudicial Branch on Venus. Dealing exclusively with Life-form laws, permits, permit violations and the like. The same is true to a Special Branch of the Union Police that specialized in Life-form traffic in all its forms. Both the Court and the Police departments deal with such cases Union wide. Both departments are special trained and educated on Venus . The Union Fire Department has a special Bio Hazard Incident Response Team here
Union Installations: Union Post Office, Union Schools, Federal Police Precinct, Union Court, Union Fire Department (Bio Haz), Union College, Union Accredited University, Xchange, Science Council HQ,
Import: Anything related to Biology, Zoology, Life forms. Machinery, Luxury Goods, General Groceries
Export: Anything related to Biology, Zoology, Life Forms, Drugs, Bio Chemicals | 0.824799 | 3.785091 |
The space between stars is known as interstellar space, and so the space between galaxies is called intergalactic space. These are the vast empty spaces that sit between galaxies. For example, if you wanted to travel from the Milky Way to the Andromeda galaxy, you would need to cross 2.5 million light-years of intergalactic space.
Intergalactic space is as close as you can get to an absolute vacuum. There’s very little dust and debris, and scientists have calculated that there’s probably only one hydrogen atom per cubic meter. The density of material is higher near galaxies, and lower in the midpoint between galaxies.
Galaxies are connected by a rarefied plasma that is thought to posses a cosmic filamentary structure, which is slightly denser than the average density of the Universe. This material is known as the intergalactic medium, and it’s mostly made up of ionized hydrogen. Astronomers think that the intergalactic medium is about 10 to 100 times denser than the average density of the Universe.
This intergalactic medium can actually be seen by our telescopes here on Earth because it’s heated up to tens of thousands, or even millions of degrees. This is hot enough for electrons to escape from hydrogen nuclei during collisions. We can detect the energy released from these collisions in the X-ray spectrum. NASA’s Chandra X-Ray Observatory – a space telescope designed to search for X-rays – has detected vast clouds of hot intergalactic medium in regions where galaxies are colliding together in clusters.
We have written many articles about galaxies for Universe Today. Here’s an article about how intergalactic dust might be messing up observations, and here’s an article about a cosmic hurricane in a starburst galaxy.
We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies. | 0.880962 | 3.563565 |
NASA’s Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way. The feature spans 50,000 light-years and may be the remnant of an eruption from a supersized black hole at the center of our galaxy.
“What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center,” said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who first recognized the feature. “We don’t fully understand their nature or origin.”
The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be millions of years old. A paper about the findings has been accepted for publication in The Astrophysical Journal.
Finkbeiner and Harvard graduate students Meng Su and Tracy Slatyer discovered the bubbles by processing publicly available data from Fermi’s Large Area Telescope (LAT). The LAT is the most sensitive and highest-resolution gamma-ray detector ever launched. Gamma rays are the highest-energy form of light.
Other astronomers studying gamma rays hadn’t detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light interact with light and interstellar gas in the Milky Way. The LAT team constantly refines models to uncover new gamma-ray sources obscured by this so-called diffuse emission. By using various estimates of the fog, Finkbeiner and his colleagues were able to isolate it from the LAT data and unveil the giant bubbles.
Scientists now are conducting more analyses to better understand how the never-before-seen structure was formed. The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The structure’s shape and emissions suggest it was formed as a result of a large and relatively rapid energy release — the source of which remains a mystery.
One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way’s black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way’s center several million years ago.
“In other galaxies, we see that starbursts can drive enormous gas outflows,” said David Spergel, a scientist at Princeton University in New Jersey. “Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics.”
Hints of the bubbles appear in earlier spacecraft data. X-ray observations from the German-led Roentgen Satellite suggested subtle evidence for bubble edges close to the galactic center, or in the same orientation as the Milky Way. NASA’s Wilkinson Microwave Anisotropy Probe detected an excess of radio signals at the position of the gamma-ray bubbles.
The Fermi LAT team also revealed Tuesday the instrument’s best picture of the gamma-ray sky, the result of two years of data collection.
“Fermi scans the entire sky every three hours, and as the mission continues and our exposure deepens, we see the extreme universe in progressively greater detail,” said Julie McEnery, Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
NASA’s Fermi is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.
“Since its launch in June 2008, Fermi repeatedly has proven itself to be a frontier facility, giving us new insights ranging from the nature of space-time to the first observations of a gamma-ray nova,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “These latest discoveries continue to demonstrate Fermi’s outstanding performance.” | 0.918798 | 4.098638 |
A little over a year since its completion, China’s 500-metre Aperture Spherical Telescope (FAST for short) has just made its first confirmed discovery.
Astronomers used the giant dish to spot a pair of pulsars thousands of light years away, heralding big things for what is now the world’s largest single dish radio telescope.
The stars, called PSR J1859-01 and PSR J1931-01, were detected by the telescope back in August, but it took a few extra months until the Parkes telescope in Australia could confirm them as the real deal.
Both objects are dense, rapidly spinning stars surrounded by strong magnetic fields. These fields channel electromagnetic radiation into a beam that describes a circle with every rotation, much like a cosmic lighthouse.
Seen from Earth, the stars seem to pulse with every sweep, giving them their name pulsar. Their positions and timing make for useful landmarks in space, not to mention handy cosmic clocks for testing general relativity.
The pair discovered by FAST – also dubbed FP1 and FP2 – don’t stand out in terms of size, speed, or distance.
“FP1 is a pulsar with a spin period of 1.83 second and an estimated distance of 16 thousand light-years, and FP2, is a pulsar with a spin period of 0.59 second and an estimated distance of 4,100 light years,” says deputy chief engineer of FAST, Li Di.
For a comparison, the fastest pulsar turns on its axis an insane 642 times per second.
In February the European Space Agency found a pulsar that was a thousand times brighter than ever thought possible, 50 million light years away.
But give it a chance – FAST exceeds the 305 metre wide Arecibo Observatory in Puerto Rico as the largest dish of its kind, so far more impressive discoveries are surely yet to come.
“The two new discovered pulsars symbolise the dawn of a new era of systematic discoveries by Chinese radio telescopes,” says Yan Jun, director of the National Astronomical Observatories of China.
The US$185 million facility was built to collect radio waves washing over the planet from the far reaches of deep space, allowing researchers to pick up faint traces of radiation from ancient clouds of hydrogen gas, distant black holes, pulsars, or … just maybe … alien wifi.
The dish sits inside a giant sinkhole in Guizhou Province, southwest China, where limestone has dissolved away to leave a massive depression.
The stats are impressive; 4,450 panels give the dish a collection area of 196,000 square metres (about 2,109,700 square feet), more than doubling Arecibo’s coverage.
A bigger dish can collect more radio waves, which means detecting fainter signals; just the thing we need to see deeper into space, and therefore further back in time.
This hollow amid the surrounding hills provides a natural shelter from more Earthly radio waves, giving FAST a quiet spot to stare at the heavens.
Closer to home, the giant dish could also be used to track spacecraft travelling to Mars as part of China’s burgeoning space program.
China has been making extraordinary leaps in space-based technology in recent years, such as facilitating the first quantum-encrypted satellite link-up just a few weeks ago.
Earlier this year the China Aerospace Science and Technology Corporation announced it would be conducting a record 30 launches into space this year, maintaining a trend in recent years that could see it meet its goal of landing technology on Mars by 2020.
FAST is just one more example of the nation’s rapid progress in space technology. While it still has a few more tests to conduct to fine tune its processes, it won’t be long before the facility is available to astronomers all over the globe.
We can’t wait to see what else it discovers. | 0.879816 | 3.852252 |
Spring brings some of the finest, and easiest, astronomical viewing to the Hudson Valley’s night sky.
It’s a great time to see some of the best and brightest galaxies, as well as an array of double-stars, globular clusters (imagine a solar system made entirely of suns, thousands of suns), and nebulae (vast interstellar dust clouds and the remnants of dead stars).
To make the most of the following descriptions, you’ll need access to a star map. If you don’t have one, monthly magazines like Astronomy (astronomy.com) and Sky & Telescope (skyandtelescope.com) publish highly usable charts and maps to get you started. Alternatively, you can go straight to the Internet, at either of the above sites, and easily generate an accurate sky chart for your location tonight.
For the ultimate in desktop exploration and easy planning, planetarium software such as Starry Night (starrynight.com) for Mac or PC is the way to go; for Mac users, Starry Night also provides a free dashboard widget.
Easy to find between Leo (to the west) and Libra (to the east), Virgo is another very large constellation; in fact, after Hydra, it’s the second largest. Locate the constellation’s brightest star Spica by following the curve of the Big Dipper’s handle, through Arcturus in BoЪtes, to Spica in Virgo.
The galaxy M60 is 60 million light-years from earth and is 60 billion times as luminous as our sun. The majority of Virgo’s galaxies are part of the Virgo-Supercluster, a vast cluster of perhaps 1,500 galaxies, of which our galaxy, the Milky Way, is an outlying member.
Finally, Virgo has more confirmed exoplanets than any other constellation: 24 exoplanets orbiting 18 stars.
Lying well above the southern horizon at this time of year, Leo is a large constellation, some 30° across. Packed with gorgeous galaxies and double-stars, it’s well worth checking out.
The brightest star in Leo is Regulus, visible in the lower right part of the constellation, at the base of the “sickle” shape. This blue-white star is about 77.5 light-years from Earth—meaning its light has taken that long to land on your retina. Using binoculars, can you pick out its companion star?
One of the finest double-stars in the sky is Algieba, a “true double” with two yellow stars locked together in orbit, and spinning past each other once every 620 years.
In comparison, Denebola, a double star with blue/orange components, is an “optical double,” meaning the stars are not connected gravitationally; they are far apart in space and simply happen to lie on the same line of sight. Galaxy-wise M65, M66, and NGC 3628 form the Leo “Triplets”, a nice group of galaxies visible through your telescope all together in the same field of view. M65 and M66 are brighter than NGC 3628 but you can make out the latter’s elongated form; it looks very “edge-on”.
Lying along the southern horizon at midnight, and spanning a full 90°, Hydra is the largest constellation in the night sky.
The first galaxy to check out is M83, an impressive barred spiral galaxy; even a small telescope will pick up its obvious structure.
Visible as a small round cloud in binoculars, M68 is a globular cluster, floating in space some 33,000 light-years distant. Globular clusters are some of the oldest structures in our galaxy, and their formation and stability is something of a mystery. A telescope will resolve the cloud into individual suns. Spectacular.
If you’re in the mood for ghost hunting, check out NGC 3242, the Ghost of Jupiter, a fine “planetary” nebula—formed as a dying sun begins to cast off its outer layers. Even small scopes bring out its pale blue disc that appears about the same size as Jupiter (which is how it got its nickname).
by Sean O’Dwyer
PLANETS & METEORS
On April 3rd Saturn will be at opposition, meaning the sun and Saturn will be on diametrically opposite sides of the sky. This means it rises in the east as the sun sets in the west, and remains visible all night long. This is great because, at this point in its orbit, it comes closest to the Earth and therefore appears bigger and brighter than at other times. It’s the ideal time of year to view the ringed wonder. Even a small telescope can split the rings into their A and B components.
On April 21/22, the Lyrid Meteor Shower peaks. Not normally a huge shower, it can nonetheless produce meteors with very bright trails that last several seconds. Meteor showers are best viewed with the naked eye, wrapped in a warm blanket. | 0.912397 | 3.65426 |
Traditionally, two main types of landscape — continents and the sea — stand out on the moon. The prevailing shape of the relief of the lunar surface is the lunar seas, which are huge in size basins of dark color. Of course, there is no water in these seas, but so these depressions were named in the distant past for their dark color; these names have survived to this day. Smaller dark spots, by analogy with the seas, received the names of bays, lakes and swamps. The main seas are concentrated within the visible hemisphere. The largest marine formation is the Ocean of Storms. Adjacent to it is the Sea of Rains from the northeast, the Sea of Humidity and the Sea of Clouds from the south. In the eastern half of the disk visible from the earth, a chain stretched from the northwest to the southeast of the Sea of Clarity, the Sea of Tranquility and the Sea of Plenty. The Sea of Nectar adjoins this chain from the south, and the Sea of Crisis from the northeast. Relatively small marine areas are located on the border of the visible and reverse hemispheres. These are the East Sea, the Regional Sea, the Smith Sea and the South Sea. On the reverse side, there Continue reading
Stars whose mass is 1.5-3 times greater than that of the Sun will not be able to stop their compression at the stage of a white dwarf at the end of their lives. Powerful gravitational forces will squeeze them to such a density at which a “neutralization” of the substance takes place: the interaction of electrons with protons will lead to the fact that almost the entire mass of the star will be enclosed in neutrons. A neutron star is formed. The most massive stars can form into neutron stars after they explode like supernovae.
The concept of neutron stars is not new: the first assumption about the possibility of their existence was made by the talented astronomers Fritz Zwicky and Walter Baarde of California in 1934. (A little earlier in 1932, the possibility of the existence of neutron stars was predicted by the famous Soviet scientists L.D. Continue reading
About seven thousand years ago, a star suddenly exploded in a remote corner of outer space, dropping the outer layers of matter. A relatively large and massive star suddenly ran into a serious energy problem – its physical integrity was in jeopardy. When the boundary of stability was passed, an exciting, extremely powerful one of the most catastrophic explosions in the entire Universe broke out, giving rise to a supernova.
For six thousand years, light from this star from the constellation Taurus raced through outer space and finally reached Earth. It happened in 1054. In Europe, science was then slumbering, and among the Arabs it was experiencing a period of stagnation, but in another part of the Earth, observers noticed an object glistening majestically in the sky before sunrise. Continue reading | 0.885418 | 3.714365 |
Scotland’s Sky in April, 2018
Impressive conjunction before dawn for Mars and Saturn
The Sun climbs almost 10° northwards during April to bring us longer days and, let us hope, some decent spring-like weather at last. Our nights begin with Venus brilliant in the west and end with three other planets rather low across the south. Only Mercury is missing – after rounding the Sun’s near side on the 1st it remains hidden in Scotland’s morning twilight despite standing further from the Sun in the sky (27°) on the 29th than at any other time this year.
Edinburgh’s sunrise/sunset times change from 06:44/19:51 BST on the 1st to 05:32/20:50 on the 30th. The Moon is at last quarter on the 8th, new on the 16th, first quarter on the 22nd and full on the 30th.
Mars and Saturn rise together in the south-east at about 03:45 BST on the 1st and are closest on the following day, with Mars, just the brighter of the two, only 1.3° south of Saturn. Catch the impressive conjunction less than 10° high in the east-south-east as the morning twilight begins to brighten.
Both planets lie just above the so-called Teapot of Sagittarius but they are at very different distances – Mars at 166 million km on the 1st while Saturn is nine times further away at 1,492 million km.
Brightening slightly from magnitude 0.5 to 0.4 during April, Saturn moves little against the stars and is said to be stationary on the 18th when its motion reverses from easterly to westerly. Almost any telescope shows Saturn’s rings which are tipped at 26° to our view and currently span some 38 arcseconds around its 17 arcseconds disk.
Mars tracks 15° eastwards (to the left) and almost doubles in brightness from magnitude 0.3 to -0.3 as its distance falls to 127 million km. Its reddish disk swells from 8 to 11 arcseconds, large enough for telescopes to show some detail although its low altitude does not help.
Saturn is 4° below-left of Moon and 3° above-right of Mars on the 7th while the last quarter Moon lies 5° to the left of Mars on the next morning.
Orion stands above-right of Sirius in the south-west as darkness falls at present but has all but set in the west by our star map times. Those maps show the Plough directly overhead where it is stretched out of shape by the map projection used. We can extend a curving line along the Plough’s handle to reach the red giant star Arcturus in Bootes and carry it further to the blue giant Spica in Virgo, lower in the south-south-east and to the right of the Moon tomorrow night.
After Sirius, Arcturus is the second brightest star in Scotland’s night sky. Shining at magnitude 0.0 on the astronomers’ brightness scale, though, it is only one ninth as bright as the planet Jupiter, 40° below it in the constellation Libra. In fact, Jupiter improves from magnitude -2.4 to -2.5 this month as its distance falls from 692 million to 660 million km and is hard to miss after it rises in the east-south-east less than one hour before our map times. Look for it below-left of the Moon on the 2nd, right of the Moon on the 3rd, and even closer to the Moon a full lunation later on the 30th.
Jupiter moves 3° westwards to end the month 4° east of the double star Zubenelgenubi (use binoculars). Telescopes show the planet to be about 44 arcseconds wide, but for the sharpest view we should wait until it is highest (17°) in in the south for Edinburgh some four hours after the map times.
Venus’ altitude on the west at sunset improves from 16° to 21° this month as the evening star brightens from magnitude -3.9 to -4.2. Still towards the far side of its orbit, it appears as an almost-full disk, 11 arcseconds wide, with little or no shading across its dazzling cloud-tops. Against the stars, it tracks east-north-eastwards through Aries and into Taurus where it stands 6° below the Pleiades on the 20th and 4° left of the star cluster on the 26th. As it climbs into our evening sky, the earthlit Moon lies 6° below-left of Venus on the 17th and 12° left of the planet on the 18th.
The reason that we have such impressive springtime views of the young Moon is that the Sun’s path against the stars, the ecliptic, is tipped steeply in the west at nightfall as it climbs through Taurus into Gemini. The orbits of the Moon and the planets are only slightly inclined to the ecliptic so that any that happen to be towards this part of the solar system are also well clear of our horizon. Contrast this with our sky just before dawn at present, when the ecliptic lies relatively flat from the east to the south – hence the non-visibility of Mercury and the low altitudes of Mars, Saturn and Jupiter.
The evening tilt of the ecliptic means that, under minimal light pollution and after the Moon is out of the way, it may be possible to see the zodiacal light. This appears as a cone of light that slants up from the horizon through Venus and towards the Pleiades. Caused by sunlight reflecting from tiny particles, probably comet-dust, between the planets, it fades into a very dim zodiacal band that circles the sky. Directly opposite the Sun this intensifies into an oval glow, the gegenschein (German for “counterglow”), which is currently in Virgo and in the south at our map times – we need a really dark sky to see it though.
Diary for 2018 April
Times are BST.
1st 19h Mercury in inferior conjunction on Sun’s near side
2nd 13h Mars 1.3° S of Saturn
3rd 15h Moon 4° N of Jupiter
7th 14h Moon 1.9° N of Saturn
7th 19h Moon 3° N of Mars
8th 08h Last quarter
16th 03h New moon
17th 13h Saturn farthest from Sun (1,505,799,000 km)
17th 20h Moon 5° S of Venus
18th 03h Saturn stationary (motion reverses from E to W)
18th 15h Uranus in conjunction with Sun
22nd 23h First quarter
24th 05h Venus 4° S of Pleiades
24th 21h Moon 1.2° N of Regulus
29th 19h Mercury furthest W of Sun (27°)
30th 02h Full moon
30th 18h Moon 4° N of Jupiter
This is a slightly revised version, with added diary, of Alan’s article published in The Scotsman on March 31st 2018, with thanks to the newspaper for permission to republish here.
Posted on 31/03/2018, in Uncategorized and tagged Alan Pickup, Arcturus, ASE, Astronomical Society of Edinburgh, diary, gegenschein, Jupiter, Libra, Mars, Mercury, moon, Night Sky, orion, Pleiades, Sagittarius, Saturn, Scotland, Sirius, Taurus, The Scotsman, Venus, Virgo, zodiacal light, Zubenelgenubi. Bookmark the permalink. Leave a comment. | 0.91353 | 3.349574 |
I’ve always respected the “fiction” part of “science-fiction”. I believe that if you correctly put your premises and if you remain consistent, everything is OK.
Nevertheless, it should not be a problem to compare a fictive universe with a the real world, and this is precisely what I’m about to do here, once again.
In Ant-man, there is this special suit that allows a human to shrink to the size of an insect (hence the name « ant-man »), or even smaller. In the movie, they say that they achieve this by reducing the space between the atoms.
Scientifically, this is not absurd at all. We do this in a lab. Well… sort of. And not in every lab. But still.
For instance, in order to fuse two atoms of hydrogen, one has to make two hydrogen nuclei come close enough so that the short-range attraction of the strong-force overcomes the long-range repulsion of the electric-force. The point at which the repulsion becomes an attraction is called the Coulomb-barrier.
In a tokamak — a particle accelerator dedicated to nuclear fusion — this is achieved by heating hydrogen atoms to tremendous temperatures, at over hundreds of millions of degrees. Only at those temperatures are the particles moving fast enough so that, when they collide, they come close enough together to fuse.
Getting to such high temperatures is hard, so there is an other solution. We can create a smaller hydrogen atom !
For that, we create what is called “exotic atoms”, and in this case, muonic hydrogen.
In this type of hydrogen, the electron is replaced with a muon: a negative particle with the charge of an electron but a much greater mass (and also with a very short half-life).
Its greater mass allows the muon to orbit much closer to the nucleus, and the whole atom is much smaller than regular hydrogen. Having that, a H2 molecule can be smaller too and the two nuclei are closer together. Thus, the temperatures to reach in order to fuse them are much lower. This is called “cold fusion” (even if we still speak about thousands of degrees).
This is one example of making small atoms.
How-to turn Ant-Man into a black-hole ?
Applying the above to a human being, however, would not be possible. First of all, muons are not stable : they decay after a matter of milliseconds.
But if it were stable ? Would it be possible ?
Sadly… no : the guy would indeed turn into a black-hole.
In a solid, the space between atoms is already minimal (that’s why solids are not compressible, like gases). If one compresses a solid above a point (a very high point, like in dying stars), the atoms and matter collapses: electrons and protons fuse into neutrons.
In a neutron-star, all the empty space that usually surrounds an atom-nucleus is filled with neutrons and matter reach an enormous density. One cubic centimeter of a neutron-star would weigh as much as the Himalaya chain.
If ones goes even further in compressing matter, and if we have a very big neutron star, then even all those neutrons can't hold the pressure and the matter degenerates to an ultimate point: a singularity. In other words, all the mass is compressed to a single point in space and we get a black-hole.
Any amount of matter is enough to create a black-hole, as long as you compress it sufficiently.
Take the earth, for instance: if you compress it to a sphere with a radius of 0.9 cm, the size of a marble that is, it turns into a black-hole.
Each object has it’s own size under which it turns to a black-hole. That specific size is called it’s Schwartschild's Radius.
For a 80 kilo man, that size would be 1.18 × 10^-22 meter (a ten-thousandth of the size of a proton).
In the movie, it seems that Ant-Man, at one point, goes far bellow this point. He should turn into a black-hole at some point, but he doesn’t.
So, in Ant-man, this part is only “fiction”. I’ll pass on that.
How small can one get?
Another problem rises after that though: how small can he get?
Answer: not indefinitely small (but he could get indefinitely smaller, if he shrinks asymptotically).
Physics predicts a “smallest size” of all.
Nothing, no objects of measurable distances, could be smaller than that smallest size. This is Planck's length, and would be as small as 1,6 × 10^−35 meters.
The same goes for the smallest achievable duration, called Plank's time: 5,3 × 10^−44 second.
So if Ant-Man shrinks for ever, it will be asymptotically, but it won’t be smaller than 1,6 × 10^−35 meters.
Very interestingly, this seems to happen in the movie: at one point, he doesn’t shrink anymore, at least not as fast as before. Did they take the Planck-length into account? This would be great, even if I don’t really think so.
The problem of sound when you’re very small
At this point, there is another thing that’s not real in that movie: sound.
In the movie, Ant-man shrinks.
We see that it goes smaller than a cell, ok.
Then than an atom, great.
Than sub-atomic particles, well, still good.
And then… Then we do not really know what we see. In fact we do not know what’s below the level of quarks, inside protons and neutrons.
A bit like is the movie Interstellar which depicts the insides of a black-hole, everything is quite beautiful and fancy, but it has no scientific value: every thing is at best an educated representation, but nothing is really known there. But this is not what bugs me.
The real problem lies with the fact that Ant-Man hears his daughter crying when he shrinks.
If one gets smaller than an atom, sound would not be part of reality. Sound is propagated through the vibration of atoms, that finally hits our internal ear. If we are much smaller than an atom, no atom can hit our ears. Sound does not exist at that scale.
Same goes on with us being on Earth: the Earth rotates, but do we feel it? No, because we rotate with it. We can only know it because we see the rest of the sky and celestial bodies rotate.
For Ant-Man being inside an atom, if he vibrates with an atom, He should not notice it, hence he should not hear the voice of his daughter. A bit like we humans do not really feel the rotation of the earth or its revolution around the Sun.
This was, for me, the only real scientifically-noticeable problem in that movie.
Oh, and there is also that claim where Ant-Man keeps his momentum (his mass) when he shrinks, but how can he still ride an ant, if he still weights 80 kilos? | 0.850285 | 3.415857 |
An incredible new photo taken by a telescope in the Southern Hemisphere captures an odd couple shimmering beautifully in a star-forming region of a nearby galaxy.
The new photo was taken by the Very Large Telescope in Chile and shows two clouds of gas shining in blue and red in the Large Magellanic Cloud, about 163,000 light-years from the Milky Way. The European Southern Observatory, which oversees the Very Large Telescope, unveiled the image today (Aug. 6) along with a video tour of the photo of the dazzling cosmic clouds.
"The strikingly different colors of NGC 2014 and NGC 2020 are the result of both the different chemical makeup of the surrounding gas and the temperatures of the stars that are causing the clouds to glow," officials from ESO wrote in an image description. "The distances between the stars and the respective gas clouds also play a role."
The pink cloud, NGC 2014, is mostly composed of hydrogen gas. A cluster of young, hot stars emits radiation that strips electrons from the atoms in the gas, creating the red glow, ESO officials said. Stellar winds from the new stars cause the gas around them to scatter.
NGC 2020 is the blue circle of gas around the bright new star shining on the left hand side of the image. The star could be more than 10 times as hot as the surface of Earth's sun, ESO officials wrote.
"The distinctive blueish color of this rather mysterious object is again created by radiation from the hot star — this time by ionizing oxygen instead of hydrogen," ESO officials said of NGC 2020.
The Large Magellanic Cloud and its counterpart, the Small Magellanic Cloud, were named for the explorer Ferdinand Magellan. Although Magellan died in the Philippines before returning to Europe, his crew brought news of the celestial sights to the continent.
The Large Magellanic Cloud is about 14,000 light-years across, while the Milky Way extends about 100,000 light-years, ESO officials said. It is known as an irregular dwarf galaxy and plays host to less than one tenth the mass of the Milky Way. | 0.892316 | 3.140264 |
Heaviest star in the universe is almost 'too massive to exist'
Sept. 17, 2019
Astronomers have discovered the heaviest star in the universe that, they say, is more than twice the mass of our sun.
Amazingly, the star is only 15 miles across. That makes the density and the weight of it so huge as to be almost unimaginable.
It’s about 700,000 times heavier than Earth and is what’s known as a ‘neutron’ star – basically the compressed remains of a supernova. It happens when a giant star collapses in on itself in a massive explosion.
Despite bearing such an impressive title of ‘heaviest’ star in the known universe, it has a pretty uninspiring official name: J0740+6620.
According to the US team studying it, J0740+6620 is ‘the most massive neutron star ever detected — almost too massive to exist.’
The measurement approaches the limits of how compact a single object can be without crushing itself into a black hole.
It was detected about 4,600 light years from Earth by the Green Bank Telescope in West Virginia. One light year is about six trillion miles.
‘This neutron star is twice as massive as our Sun,’ said Paul Demorest, from the National Radio Astronomy Observatory (NRAO), in Charlottesville, Virginia.
‘This is surprising and that much mass means that several theoretical models for the internal composition of neutron stars now are ruled out.
‘This mass measurement also has implications for our understanding of all matter at extremely high densities and many details of nuclear physics.’
The researchers used an effect of Einstein’s theory of relativity to calculate its mass thanks to an orbiting companion star.
As the white dwarf passes directly in front of the pulsar this causing a delay for the time the radio waves take to reach earth.
The delay – called the Shapiro Effect – is caused by gravity enabling the mass of both stars to be precisely measured.
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Astronomers have captured images of radio jet waves blasting into outer space as a star was ripped apart by an enormous black hole. This actually took place over the course of 10 years, and an international team of scientists have followed the star’s complete destruction. It’s also the first time they’ve observed jets of radio waves emitting from a shredding star.
Twitter - @ABCscience
When stars get close to a supermassive black hole, they stretch out and send bright flares as a final act before their gases fall beyond the event horizon. These flares are registered on the X-ray, ultraviolet and visible light spectrum. Astronomers at the University of Turku in Finland were originally looking at a pair of colliding galaxies, known as Arp 299, hoping to see signs of supernovae.
Twitter - @ucddublin
Arp 299 is around 150 million light years away in the constellation Ursa Major, more commonly referred to as The Big Dipper. Due to the huge clouds of dust left behind by Arp 299’s massive young stars, the scientists had to go to less affected “long wavelengths of light with infrared and even radio waves,” said study co-author Stuart Ryder of the Australian Astronomical Observatory.
Twitter - @SPACEdotcom
During their initial observations, they caught a bright burst of infrared emissions coming from the dusty centre of one of the galaxies. They then used a series of radio telescopes, known as the VLBA, or Very Long Baseline Array, to received new radio signals from the area. Eventually they became brighter and size years later, in 2011, they could make out an elongated jet-like structure. Over the decade, 100 times the energy seen in a typical supernova explosion was observed. Check out the video below for more info... | 0.809123 | 3.542942 |
Puzzled experts say the "strange behaviour" is causing trouble for satellites and aircraft – and some think it could be an early sign that Earth's magnetic poles will soon flip.
Earth's magnetic field keeps us safe
Earth's magnetic field is vital to life on our planet.
It's an ever-changing force that protects us from cosmic radiation – and charged particles from the Sun.
The field is mostly generated by the ocean of super-hot liquid iron that makes up the outer core of Earth, around 3,000km below our feet.
It creates electrical currents that generate (and change) our electromagnetic field.
But the field is getting weaker: over the last 200 years, it's lost around 9% of its strength globally.
Our magnetic field is weakening – especially in South America
Now scientists have noticed a particular patch of reduced intensity, which has developed between South America and Africa.
It's called the South Atlantic Anomaly, and it's constantly changing.
Between 1970 and 2020, its minimum strength has dropped from 24,000 nanoteslas to 22,000, as tracked by the European Space Agency.
And the area has grown and moved westward at around 20km per year.
A second centre of reduced intensity has also appeared in the last five years, just southwest of Africa.
This could mean that the South Atlantic Anomaly may split up into two parts.
"The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously," said Jürgen Matzka, from the German Research Centre for Geosciences.
"We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly.
"The challenge now is to understand the processes in Earth's core driving these changes."
Magnetic pole reversal fears
Some scientists fear that the Earth's weakening magnetic field could mean Earth is heading for a pole reversal.
That would mean the north and south magnetic poles would switch places.
This has happened fairly regularly throughout Earth's history, approximately once every 250,000 years.
We're currently "overdue", because the last flip was around 780,000 years ago.
There's no evidence that this will happen soon, as fluctuations are common.
But satellites and spacecraft flying in the area are more likely to experience technical malfunctions due to the weaker magnetic field.
Magnetic north is MOVING
This "weakening" isn't the only big change happening to Earth's magnetic field, either.
Recent studies have also shown that the magnetic North Pole is rapidly changing.
Geographically, the North Pole never changes – but magnetic north does.
It's caught in a tug of war between two magnetic "blobs" deep below Earth's surface.
One of these "blobs" is in Canada and the other is in Siberia.
It's the latter blob that's winning, which is why magnetic north is drifting towards Siberia from the Canadian Arctic.
This has been the case since it was first measured in 1831, but its pace has sped up since the 1990s.
It was previously wandering at a rate of 0-15km per year, but it's now moving at 50-60km a year.
It means that the World Magnetic Model needs to be updated more frequently.
That's a vital navigation system, and is even used to guide our smartphones.
The way these "blobs" move and stretch dictates Earth's magnetic field.
"We can now pinpoint that a change in the circulation pattern of flow underneath Canada has caused a patch of magnetic field at the edge of the core, deep within the Earth, to be stretched out," said Phil Livermore, of the University of Leeds.
"This has weakened the Canadian patch and resulted in the pole shifting towards Siberia."
Pole reversals – the key facts
Here's what you need to know…
- A geomagnetic reversal is when the magnetic north and south poles switch
- That's not the same as geographic north and south – which don't move
- It means a compass designed to point to the North Pole would face the complete wrong direction
- Reversals have happened at least 183 times over the last 83million years
- The most recent was called the Brunhes-Matuyama reversal, which happened 780,000 years ago
- Experts believe it takes around 7,000 years for a reversal to complete
- A reversal happens spontaneously, due to the dynamic and unpredictable nature of Earth's liquid core
What's currently unclear is whether the pole will ever go back towards Canada.
At present, the pace is only increasing towards Siberia – but that might not always be the case.
"Models of the magnetic field inside the core suggest that, at least for the next few decades, the pole will continue to drift towards Siberia," explained Dr Livermore.
"However, given that the pole’s position is governed by this delicate balance between the Canadian and Siberian patch, it would take only a small adjustment of the field within the core to send the pole back to Canada."
In other news, Nasa has published mind-blowing photos of the surface of Mars.
The US military is developing a secretive network of spy satellites that will one day blanket Earth's orbit.
And Brits took stunning snaps of Elon Musk's Starlink satellites passing over the UK in April.
We pay for your stories! Do you have a story for The Sun Online Tech & Science team? Email us at [email protected]
Source: Read Full Article | 0.852171 | 3.367459 |
Rare blue moon comes Friday
Posted: Jul 29, 2015 5:18 PM CDT
(CNN) If anything unusual happens to you Friday, you'll be right to say it was \"once in a blue moon.\"
The July 31 appearance of the month's second full moon will be the first such occurrence in the Americas since August 2012. Every month has a full moon, but because the lunar cycle and the calendar year aren't perfectly synched, about every three years we wind up with two in the same calendar month.
But Earth's satellite will most likely not appear blue at all.
Typically, when a moon does take on a bluish hue, it is because of smoke or dust particles in the atmosphere, such as during a cataclysmic volcanic eruption.
Celestial events in the sky
One example of this happened in 1883, when the Indonesian volcano Krakatoa erupted, spewing so much ash into the atmosphere that the moon took on a cerulean tinge for years, night after night. After the massive explosion, which scientists believe rivaled a 100-megaton nuclear bomb, the volcanic debris caused vibrant red sunsets and the moon to have a bluish tint.
The dark blue tone of an evening sky can affect the coloring we perceive, as well.
So when the phrase \"once in a blue moon\" was coined, it meant something so rare you'd be lucky (or unlucky) to see in your lifetime, according to NASA's National Space Science Data Center.
The most recent blue moon that was truly blue in hue was in Edinburgh, Scotland, in September 1950. Astronomer Robert Wilson of the Royal Observatory observed the event and concluded that the moon was blue in color because the satellite's light was traveling through a patch of clouds that had particles of smoke and ash from forest fires burning in Alberta, Canada. Those particles crossed the Atlantic Ocean and hovered over Scotland during the lunar event, creating a rare spectacle, according to the National Oceanic and Atmospheric Administration.
Tips for moon watchers
Today's modern day usage of the phrase blue moon can be attributed to a Sky and Telescope writer who in the 1940s tried to clear up a confusing definition published by the Maine Farmers' Almanac. The U.S. Naval Observatory in Washington states that when a season has four full moons, the third one is called a blue moon.
This lunar event will not be seen again until January 2018. | 0.812208 | 3.088234 |
The intensive exploration of Mars is yielding a large amount of data about its properties and its past. However, two great enigmas are yet to be explained: what caused this planet to be different from planet Earth? Is there or has there been any biological activity on the Red Planet? Particularly revealing is the comparative study of both planets.
From a distance, the Earth and Mars show some striking differences. In the first case, the prevailing colors are white and blue, corresponding to clouds and the oceans, and the brown shades of the continents. Thus, the existence of water in its various states (solid in the polar icecaps, liquid in the oceans and seas, and gaseous in the atmosphere) is evident. And the presence of water almost immediately suggests the existence of life. In fact, even from orbiting satellites it is possible to notice the planet’s intense biological activity, as is the case of the Antarctic sea ice or the seasonal change of the forest lands.
Mars is quite different. Various shades of orange, caused by iron oxide, prevail on its surface. Depending on the season and the position relative to the Earth, a pole can be visible, although on this occasion the white color essentially denotes dry ice (solid carbon dioxide). However, several studies conducted in recent years have made it clear that there is water on Mars and that the dynamics of this compound is quite complex.
Mars has a thin atmosphere consisting essentially of carbon dioxide (95.32%), nitrogen (2.7%), argon (1.4 %) and traces of oxygen (0.13%). By contrast, the Earth’s atmosphere consists essentially of nitrogen (78.1 %), oxygen (20.94%), argon (0.93%) and a variable amount of carbon dioxide (around 0.035%, and increasing quickly). The average temperatures vary greatly: -55 degrees Celsius (ºC) in the case of Mars, with lows of around -133 ºC and highs of some +27 ºC; and an average of around +15 ºC in the case of the Earth, with lows of -89.4 ºC (in Vostok, the Antarctica, although temperatures of -93.2 ºC have been recorded recently nearby, in measurements taken by a satellite) and highs of +58 ºC or +56.7 ºC (in El Azizza, in Libya, or in Furnace Creek, in the U.S.). However, the Earth’s average temperature is affected by the greenhouse effect caused by gases in the atmosphere, mainly carbon dioxide, water vapor, ozone (molecules of oxygen with three atoms, instead of the two of the oxygen we breathe) and methane. Otherwise, the average temperature would be about 33 ºC lower, around -18 ºC, and therefore the water would be in solid state in most parts of the planet.
In the cases of Mars and the Earth, the internal structure is divided into three well-differentiated regions: crust, mantle and core. However, contrary to the Earth, Mars’ core is solid and does not create its own magnetic field. There are, however, local magnetic fields, “fossil” remains of a global field that may have existed as a result of a partially liquid core, as in the case of the Earth. The virtual absence of plate tectonics, as we know it on Earth, which causes strong volcanic activity and orogeny (mountain formation), means that Martian soil is much older than the Earth’s ocean floors and continents. For example, the great depression of the southern hemisphere, Hellas Planitia, was caused by the impact of a large celestial body some 3,900 million years ago. In the case of the Earth, evidence on the crust of an event like this would have ceased to exist a long time ago.
Figure 2: Diagram showing the topography of Mars, whose minimum (deep blue) and maximum heights (red-white) are found in a range of 16,000 kilometers. Note that Olympus Mons, the highest mountain in the Solar System, soars to a height of 21 kilometers above the level at which the pressure of the atmosphere is 6.1 millibar (the pressure at which the triple point of water is located), and which is called Mars datum (equivalent to the sea level on the Earth). Since the lowest point is found in Hellas Planitia (an old impact crater), at around 7 kilometers below the Mars datum, the difference is about 28 kilometers, significantly greater than the 18 kilometers that separate the depths of the Mariana Trench and the summit of Mount Everest. Credits: Mars Orbiter Laser Altimeter and NASA.
In any event, the comparison of the height profiles of both planets shows that they are very different: while most of the Earth’s continental land mass is concentrated in the northern hemisphere, which also lacks a polar continent, the northern hemisphere in Mars is dominated by the Vastitas Borealis depression, thousands of meters below the Mars datum. It is located at the height at which the pressure of the atmosphere is 6.1 millibar, where the triple point of water is found, defined as the point in the mass diagram (pressure versus temperature) at which a substance coexists in solid, liquid and gaseous state simultaneously. In the case of water, the exact values are 273.16 K (0.01 °C) at a pressure of 6.1173 millibar. Therefore, below the Mars datum (for example, the Hellas Planitia depths) it would be possible to find liquid water if the temperature were sufficiently high. Contrary to what happens in Mars, the Earth’s southern hemisphere is dominated by oceans and seas, although several continental masses that rise at considerable heights above sea level (such as the Antarctic Plateau) stand out in its topographic profile. The situation in Mars is more uniform. The greatest difference is the large amount of water in solid state concentrated on the Earth’s South Pole. It covers an area of some 14 million square kilometers in summer, but by including the sea ice it can expand to 30 million. In contrast, the size reached by the Martian Antarctica is much smaller, around 140,000 square kilometers, and its composition is very different since dry ice dominates, as mentioned earlier.
Curiously, in our Antarctica we find some of the closest similarities with Mars, namely low temperatures and reduced humidity. This is the case of the McMurdo valley system, located very near the coast, which geologically could have equivalents in Mars. Whether there is life or not, or there has ever been any biological activity, is still an open question. Some studies suggest that the Martian ground is too salty for life to have developed. However, in our own planet there are many examples of living creatures that develop in apparently hostile environments. These are known as extremophiles.
Several spaceships shave successfully landed on Mars. One of the most recent, which landed further north, was the Phoenix Mars Lander in 2008. Its images revealed a plain covered with polygonal shapes that resemble those present in similar regions of the Earth. It is permafrost that solidifies and melts seasonally, a clear evidence of the presence of water on the planet. Phoenix had suitable instrumentation for drilling and analyzing these structures, including their chemical composition, to try to determine if any organic compounds (although not necessarily biological) are present on the Arctic plains of Mars. Later, the Curiosity rover landed near the equator in 2012. It is still in operation and has conducted many experiments, including rock drilling. In any case, we should remember that at least on our planet there are living creatures (the extremophiles) that can grow in truly amazing environments: from acidic media to submarine volcanic calderas at high temperatures. The Río Tinto ecosystem is a typical example. Unfortunately, it cannot be ruled out that some of the probes that have landed on the Red Planet may have contaminated it with biological material.
Yes, both planets have interesting similarities and great differences. We could describe Mars as the Earth’s poor relation. However, we have just scratched a few sites on its surface. Most of its secrets remain unknown to man.
The Earth’s surface, with the height shown color-coded: blue for ocean floors and green, yellow and red for the continents. The greatest depth, in the oceanic trenches, is around 11,000 meters below sea level (deeper blue). The deeper reds denote heights of 5,000 meters above sea level. The maximum height difference on our planet is about 19,000 meters.
This text is an adapted summary of chapter 10 of the book “Visiones de Gaia: la Tierra desde el espacio” written by David Barrado and published by INTA (National Aerospace Technology Institute “Esteban Terradas”). To access the complete book in Spanish, click here. A bilingual, updated version of the article in English and Spanish in the open magazine by the BBVA Foundation.
David Barrado Navascués
Centro de Astrobiología, INTA-CSIC
European Space Astronomy Center (ESAC, Madrid) | 0.826161 | 3.898889 |
A diversity of worlds
BY DENISE BLOUGH
"I’ve always been a geek and a nerd,” says astronomy professor Scott Gaudi, recalling a time when his second grade teacher assigned his class to memorize the planets in order of distance from the sun. He went home and read an entire National Geographic picture atlas titled “Our Universe.” “I aced the homework assignment, no doubt, and I was hooked.”
What really struck Gaudi, the Thomas Jefferson Professor for Discovery and Space Exploration and vice chair of the Department of Astronomy, about the book was the idea of extraterrestrial life.
“There was a chapter on what life might look like on other bodies in the solar system,” Gaudi said, citing illustrations of creatures with giant ears so they could hear in Mars’ thin atmosphere and blimp-like beings that could float through existence in clouds on Jupiter.
Fast forward to today, and Gaudi still has his eyes on the sky. The award-winning astronomer has become a leader in the discovery of distant worlds — planets outside our solar system, known as exoplanets — through tireless research, education and advocacy.
Right around the dawn of the first exoplanet discoveries in the 1990s, Gaudi and Professor Emeritus Andrew Gould helped develop one of the main methods scientists use today to find other planets, called gravitational microlensing. This technique relies on extremely rare alignments between two stars, in which the light of the background star is pulled and warped around the star in front of it due to gravity. A planet orbiting the foreground star temporarily disturbs the warped light from the background star, allowing astronomers to detect it.
Due to its high sensitivity, gravitational microlensing can identify lower-mass planets like Earth around dim and distant stars, and it’s currently one of the only ways to detect planets in other galaxies. But because it relies on exceptionally rare phenomena, the best way to use it is by monitoring as many stars in the sky at once.
“If you looked at one star for 500,000 years, you might be lucky enough to see one of these chance alignments, and that’s a long time compared to the time it typically takes a graduate student to get their PhD,” Gaudi said, laughing. “So instead of doing that, we look at a hundred million stars on a regular basis.”
Gaudi has been involved in the discovery of more than 50 exoplanets, using both gravitational microlensing and the better-known transit method, which detects planets when they pass in front of and cast a shadow on their host star.
“Exoplanets are now found every day, which is amazing to me because I remember when I used to be able to name all of the known exoplanets,” Gaudi said. “I’ve been lucky to be part of that journey, from a field going from nothing, where we just knew about our solar system, to now knowing about this enormous diversity and complexity of planetary systems around other stars.”
What scientists have learned from more than 4,000 exoplanet discoveries is that planets are as diverse as humans — sure, there are some common traits, but each one is unique.
“Before we discovered these planets, most people thought that most solar systems would look like ours, and that almost certainly is not true. It’s almost certainly the case that our solar system is in the minority,” Gaudi said, adding that every star likely hosts at least one planet in its lifetime — meaning there are billions upon billions of planets in the Milky Way galaxy alone. “You find planets around dead stars; you find planets around high-mass stars; you find planets around low-mass stars; you find planets that are nothing like the ones in our solar system.”
Expect the unexpected
So far, the most abundant planets astronomers are seeing in the Milky Way are super-sized Earths and mini Neptunes, Gaudi said. But there have also been some pretty bizarre outliers.
One of those is also Gaudi’s favorite planet: KELT-9b, which Gaudi and his team discovered in 2017. The planet’s shockingly unusual properties threw them for such a loop they thought they had done something wrong. The Jupiter-like planet is the hottest gas giant exoplanet known, with a toasty temperature of about 7,600 degrees Fahrenheit — hotter than most stars and only 2,300 degrees cooler than the sun.
“We spent years trying to disprove that this was actually a planet because we thought it was so weird,” Gaudi said. “If I gave you the challenge of making up the weirdest planet in the universe, I would bet you’d have a hard time coming up with something weirder than this.”
He proudly keeps “baby pictures” of KELT-9b in his wallet, thanks to a gift from a former graduate student, and the planet recently enjoyed celebrity status as champion of the 2018 “Exocup,” a March Madness-style bracket in which exoplanets compete and advance based on public interest.
Astronomy brings us out of ourselves, so that we're not just living on this big pile of work; the third rock from the sun — that there's more than all that. And I think that's really important — just keeping people excited about what it means to be human and to be interested and explorers, which we all are at heart."
The most advanced telescopes (not) on Earth
Gaudi has had hands in pretty much every major exoplanet-finding telescope mission, including the recently retired Kepler space telescope (responsible for finding thousands of exoplanets, more than any other project) and the Ohio State-developed Kilodegree Extremely Little Telescope (KELT).
Developed by an Ohio State graduate student in 2006, KELT is a small telescope that uses the transit method. KELT’s small size and low sensitivity allows it to look at stars that are 100 to 10,000 times brighter than what larger telescopes can observe, meaning it can discover planetary systems with host stars bright enough to analyze their atmospheric content.
Gaudi is also the principal investigator of the Wide Field Infrared Survey Telescope’s (WFIRST) microlensing component, which is expected to identify as many as 1,400 new exoplanets.
NASA’s next flagship telescope following the James Webb telescope, the Wide Field Infrared Survey Telescope (WFIRST), will have the same sensitivity as the Hubble Space Telescope and survey 100 times more of the sky. The mission “will give us a complete census of exoplanets in our galaxy with a mass or radius greater than the Earth,” says Gaudi, who is principal investigator of WFIRST’s microlensing component. In addition, the Department of Astronomy’s Chris Hirata and David Weinberg are co-leading WFIRST’s dark energy science team, giving Ohio State a larger footprint in the project than any other institution with the accompanying NASA grants totaling millions. Credit: NASA.
"For WFIRST we are looking at hundreds of millions of stars for about 400 days and expect to find about 50,000 microlensing events,” Gaudi said. “By combining this with Kepler, this will give us a complete census of exoplanets in our galaxy with a mass or radius greater than the Earth.”
WFIRST will also test new technology, an instrument called a coronagraph, which will enable scientists to directly image nearby Jupiter-sized planets for the first time by blocking the light of a star to look for planets around it.
Additionally, Gaudi is co-chairing a potential future Habitable Exoplanet Observatory (HabEx), which could become NASA’s priority mission of the 2030s. HabEx would utilize even more advanced technology than WFIRST, giving it the ability to directly image and characterize Earth-like planets around sun-like stars, potentially looking for evidence of life. This would particularly be made possible with a “starshade,” a device shaped like a sunflower the size of a baseball diamond, to be launched in front of the telescope to block the light from a star while still allowing light from planets to come through.
“You have to wrap it up, launch it in a rocket and it has to unfurl to the precision of about a millimeter, and it has to be aligned to the telescope to about a meter,” explained Gaudi, adding that the starshade is being developed and tested at NASA’s Jet Propulsion Laboratory in Pasadena, California. “All of this sounds super hard, and it is, but the amazing thing is that we’ve been working on this technology for over a decade and we’re getting there.”
The mission is one of four potential projects being studied by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey, issued by the U.S. National Research Council to determine funding priorities within astronomy and astrophysics. Hubble, James Webb and WFIRST were each initiated through this process, and the results of the 2020 survey are expected to be released in early 2021.
“Now, for the first time, we have the technology and the scientific knowledge to actually go out and try to realize the dream that started when I read that book,” Gaudi said. “Something that used to be science fiction and a province of Hollywood or late-night discussions over beer is now a scientific endeavor, and it’s great for all of us to be alive during that time.”
Planets and politics
Gaudi also considers himself an accidental “astropolitician,” leading various NASA workgroups and speaking with legislators and policymakers to advocate for the importance of funding space missions and astronomy research.
He recently co-chaired a national committee charged by Congress to define long-term strategies for exoplanet research, and he’s made multiple trips to Capitol Hill to speak with legislators about the significance of WFIRST and exoplanets to Ohio State and the world at large.
“It’s a hard argument to make, because there are lots of other things we could be funding that are more practical, but I would argue — I’m a little biased, obviously — that astronomy is important for our society,” Gaudi said. “It brings us this sense of wonder; this idea that human beings can go and explore the universe.” | 0.912685 | 3.762174 |
NASA’s Galileo spacecraft got up close and personal with the Jovian moon Europa back in 1997, and researchers have just taken a fresh new look at the data collected by both Galileo’s magnetometer and plasma wave spectrometer instruments.
Image Credit: NASA
Upon closer examination, the researchers found substantial evidence to validate the longstanding notion that water plumes erupt from beneath Europa’s surface into space. They’ve published their findings in the journal Nature Astronomy this week.
But if scientists already knew that Europa sported plumes, then how are these findings at all significant? As it turns out, the only previous evidence for plumes on Europa were some fuzzy images snapped by the Hubble Space Telescope, but they were too blurry to reach certain conclusions.
The reexamined Galileo data, on the other hand, offers hard evidence to support the idea that these plumes erupted precisely where astronomers spotted them with the Hubble Space Telescope. That said, it’s like a eureka moment that has been realized more than two decades later.
Interest in exploring exoplanetary moons such as Enceladus and Titan has grown exponentially among scientists in recent years, as these moons sport potentially-habitable environments. The validation that Europa does, in fact, sport water plumes supports the argument for exploring these worlds up close.
Planetary scientists think that Europa hosts a sub-surface ocean and that these water plumes are tantamount to pressure release valves. If true, then life could exist just beneath Europa’s hard and icy surface.
To find out for sure, NASA would need to send a series of missions to Europa with ground-penetrating radar capabilities, among other things. Fortunately, NASA’s Europa Clipper spacecraft, planned for launch in the 2020’s, could provide some much-needed insight.
The findings after reexamining the old Galileo data bump up the urgency for such missions. That said, it should be interesting to see what we’ll find when we get there. | 0.858127 | 3.554971 |
The comet that is approaching to our Earth is discovered on December 28, 2019, in the zone of Ursa Major. Currently, it is located in Mars’ orbit, but it is approaching our planet. It was noticed by the Asteroid Terrestrial-Impact Last Alert System, also known as ATLAS. Experts claim that if the comet doesn’t break up in pieces, it will reach the closest point to the Sun.
ATLAS is the comet that is five-time larger than the size of Jupiter, which means that it is half of the size of the Sun. Because of it, when it passes next to the Earth, we will see something brighter than Venus. The precise size of the rocky ice core of the strange comet isn’t announced, but it is close as few miles, and it has a much massive atmosphere.
As we already said, ATLAS is currently in Mars’s Orbit, but its speed is increasing, and it is coming near the Earth. The comet will reach its closest point to our planet by the end of April. As it comes closer to the Sun, it is brighter and will reach to be the brightest object during the night, and became the comet of the generation.
ATLAS firstly was discovered on December 28, 2019, and it was detected as a comet with a diameter of 447,387 miles. On the other hand, the Sun has a diameter of 865,370 miles, but Jupiter has a diameter which is five times smaller than the comet, only 7,917 miles.
According to the experts, we don’t have to panic because it represents no danger to Earth. The closest point that it will reach our planet is going to be more than 72 million miles. Furthermore, the new comet has a tail that is long as its atmosphere, said Michael Jager from Austria, who is the one capturing images of the comet.
SpaceWeatherArchive reported that we shouldn’t find odd the fact that some comets grow that large as they throw prodigious amounts of gas and dust into space.
An astronomy website shared that the comet 17P/Holmes, when exploded, had an atmosphere that was larger than the Sun. Also, Great Comet in 1811, had come with the size of the Sun. Well, we need to wait and see whether the comet ATLAS will surpass the comets in the past, and become the comet over the comets.
The expected comet was noticed by the Asteroid Terrestrial-impact Last Alert system, and that is why the name is ATLAS. The last comet that could be seen from the northern hemisphere was noticed in 1997, and it was Hale-Bopp, which was a rare event for the astronomers. At that time they have required a telescope, but now, once it is closer, it is brighter, and we can see it with binoculars. The glow of ATLAS will be amplified by the Sun, but it is also brighter than the astronomers expected it would be until now.
Some people like Daniel Brown, an astronomy expert, believes that it will be a promising comet. And also, he says that as time passes, by the end of April, we will be witnesses of a stunning celestial event.
Until today, it represents the most massive green object in the Solar System. The color is made from diatomic carbon, which is a molecule with green color, often found in comets. The comet releases a beautiful green glow when the gas is formed in the near-vacuum of space.
Astronomers say that from day one of its discovering until now, there was a 4,000-fold increase in brightness. In the beginning, the comet was in Ursa Major and appeared 398,000 times dimmer in comparison to the stars that are vivid with a naked eye. At this moment, it is bright as an 8th magnitude star, which means that it is still invisible to a naked eye, but garden telescopes can quickly notice it. As it gets closer to the Sun, this comet emits better light. The reason why the comet is becoming brighter every moment is because it is throwing vast amounts of frozen gases, volatiles, according to Karl Battams of the Naval Research Lab, Washington DC. Also, he adds that this is the time where the comet is invisible to the naked eye, but it is easily vivid with binoculars.
Astronomer Matthijs Burgmeijer declared that if the assumptions become true, then this comet will be the most spectacular one since the records began.
The experts claim that ATLAS will reach from a conservative magnitude +2, which means it will be visible to the naked eye, to a great magnitude -11, which will make the comet brightest and most spectacular since their recording has started.
Our job now is to wait, and to be patient enough, because the comets can be unpredictable. Maybe this comet will be just as the previous, Ison, which was promising but didn’t give any results.
For one comet to be visible with a naked eye, it should be able to hold on to its ice. But, to do the previously mentioned process, it needs to have a large nucleus with a store of frozen gas. And the astronomers can’t confirm it at the moment, because it is too far from us. If the comet doesn’t contain a large nucleus, it will waste its gas, which will make it crumble and fade as it is approaching the Sun.
Battams says that he doesn’t have a favorable opinion of the survival of the comet, because according to him, it will break before it reaches its brightest point. According to his intuition, ATLAS is over-achieving, and because of that, it will start to fall apart, and completely vanish even before it is visible to the Earth.
Because of the similar trajectory and orbit, many scientists link this space object to the Great Comet of 1844. The trajectory of the comet would need more than 6,000-year orbit around the Sun, and it would take beyond the outer edges of the solar system.
Also, when the night comes, the comet will be visible in the north-northwest sky, and by the end of April, it will be visible with the naked eye. It is fascinating to see the development of the comet ATLAS during the upcoming weeks, especially for the astronomers who have the best equipment for these kinds of events.
There are different types of space rocks.
Asteroid represents a large chunk of rock that is abandoned from collisions. Mainly they take place between Mars and Jupiter in the Main Belt.
Comet represents a rock covered in ice, methane, and many different compounds. They have orbits which take them away, very far from the solar system.
A meteoroid is debris. Mainly meteoroids are miniature, and they are released in the atmosphere.
When one of these meteoroids reaches Earth, it becomes a meteorite.
Asteroids and comets usually create meteors, meteoroids, and meteorites. When the Earth goes through the tail of a particular comet, the debris burns certain ingredients in the atmosphere, and that is how the meteor shower is created. | 0.824414 | 3.443053 |
Scientists will now be able to measure how fast the universe is truly expanding with the kind of precision not possible before.
This, after an international team of astronomers led by Stockholm University, Sweden, captured four distinct images of a gravitationally lensed Type Ia supernova, named iPTF16geu.
To get a high-resolution view, the discovery team used the W. M. Keck Observatory’s OSIRIS and NIRC2 instruments with laser-guided adaptive optics at near-infrared wavelengths.
The resolution of the Keck adaptive optics images was equivalent to being able to distinguish the individual headlights of a car in San Francisco as viewed from Hawaii. The measurements confirmed the four separate images originated from iPTF16geu and that its light traveled for 4.3 billion years before reaching Earth.
“Resolving for the first time, multiple images of a strongly lensed supernova is a major breakthrough,” said Ariel Goobar, Professor at the Oskar Klein Centre at Stockholm University and lead author of the study. “We can measure the light-focusing power of gravity more accurately than ever before, and probe physical scales that may have seemed out of reach until now.”
The research, titled “iPTF16geu: A multiply-imaged gravitationally lensed Type Ia supernova,” published last week in the journal Science.
iPTF16geu was initially observed by the intermediate Palomar Transient Factory (iPTF), a Caltech-led international project that uses the Palomar Observatory to scan the skies and discover, in near real-time, fast-changing cosmic events such as supernovas using a fully-automated, wide-field survey.
It took some of the world’s leading telescopes to gather more detailed information about iPTF16geu. In addition to Keck Observatory, the discovery team also used the NASA/ESA Hubble Space Telescope and the European Southern Observatory (ESO) Very Large Telescope in Chile.
“The discovery of iPTF16geu is truly like finding a somewhat weird needle in a haystack,” said Rahman Amanullah, co-author and research scientist at Stockholm University. “It reveals to us a bit more about the universe, but mostly triggers a wealth of new scientific questions.”
Astronomers detect thousands of supernova every year, but only a few of those found are gravitationally-lensed. Because they are only visible for a short time, spotting them can be difficult.
“iPTF is known for finding supernova candidates, but the key is to image them with Keck Observatory’s cutting-edge adaptive optics while the supernova is still bright,” said Shri Kulkarni, John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science and co-author of the study. “Thanks to Keck Observatory’s ability to respond to such supernova events on short notice, the discovery team was able to produce fine images, which allowed them to successfully observe the light rise and fall from each of iPTF16geu’s four images.”
Standard candle sheds new light on expansion of Universe
This discovery is highly interesting to scientists because Type Ia supernovas can be used as a “standard candle” to calculate galactic distances.
A standard candle is an astrophysical object that emits a certain, known amount of light. In this case, the object is a Type Ia supernova, a class of dying stars that always explode with the same absolute brightness. If astronomers know such an object’s true luminosity, they can infer its distance from Earth. The dimmer the object, the farther away it is.
The magnifying power of gravitational lensing
This rare discovery is made possible through gravitational lensing, a phenomenon that was first predicted by Albert Einstein in 1912. As light of the distant object passes by a massive object such as a galaxy cluster in the foreground, it gets bent by gravity, just as light gets bent passing through a lens. When the foreground object is massive enough, it will magnify the object behind it. In iPTF16geu’s case, its light was magnified by up to 50 times and bent into four separate images by a galaxy in front of it.
The discovery team analyzed the four lensed images of iPTF16geu, measured how long it took for the light from each image to journey to Earth (light is not bent in the same way in each image, so the travel times are slightly different), then used the differences in the arrival times to calculate the expansion rate of the universe — known as the Hubble constant. | 0.903013 | 3.944385 |
The Dawn of the Tetraquark
May 22, 2014
On April 9, 2014, scientists at the Large Hadron Collider "unambiguously" observed a new particle dubbed Z(4430)−. This negatively charged particle is about 4.7 times more massive than a proton and deviates from the traditional quark model.1 But what is the traditional quark model, what does “unambiguously” mean, and what implications might this new particle have?
Particle Physics Timeline
Particle physics has a rich history tracing back to ancient Greek philosophers but has expanded greatly in the 20th and 21st centuries. The field describes the mechanisms of all the fundamental forces of nature as particles that transfer energy and momentum from one particle to another. These particles that mediate the forces on an atomic and subatomic level have become intertwined with the theories of the origin of our universe.
Before tackling the new “tetraquark,” we’ll begin with a timeline of particle physics and the fundamental physics behind the field as it stands today. The appendix to this article has a review of the history of particle physics.
Image Credit: Heide Doss/Physics Central
Forces of Nature
By the 1930s it was clear to scientists that there were four fundamental forces in nature that could describe all observed interactions.
• The gravitational force in which mass attracts mass. The strength of this force increases as mass increases and decreases as distance between masses increases. This is the weakest of all forces.
• The electromagnetic force in which like charges repel and opposite charges attract, and moving charges create magnetic fields which can interact with moving charged particles and other magnetic fields. This force increases as charge increases and decreases as the distance between charges increases.
• The weak nuclear force or weak force responsible for radioactive decay and involved in fusion processes. This was later found to be connected to the electromagnetic force and are thought to be two different manifestations of the same force called the electroweak force.
• The strong nuclear force or strong force, which holds together the nucleus of atoms. This force is much stronger than the other forces and its strength is felt only over distances on the order of a quadrillionth of a meter, or less.
Fields vs. Particles
Now that we have some history under our belt, let’s focus on the physics behind particles and fields. For example, electric charges exert forces on each other proportional to the size of the charges and inversely proportional to the distance between them squared. This helped inspire Faraday to think about this force in a new way:
Rather than describing the force between two charged particles one could describe a force field that any given charged particle could create. The force field created by a charged particle is called the electric field. It describes the force per charge that the charged particle creating the field would exert on another charge if it were there.
Place the actual charge within the field, and it feels a force equal to its charge multiplied by the electric field. The field can be thought of as the mechanism that allows two distant objects to interact. One often thinks of these force fields that permeate space as affecting the space. This is field theory.
The interaction between charged particles can also be described as the absorption or emission of particles (packets of electromagnetic energy) called photons. Energy and momentum are transferred between charged particles by the absorption or emission of a photon. In this case, the photon is the carrier of the electromagnetic force and energy. This is particle theory.
Richard Feynman described this exchange with what is known as Feynman diagrams (shown below).
The force between two electrons (e−) can be viewed as the passing of a photon (y) between them.
These particles can be virtual, meaning they pop into and out of existence from the vacuum field (which permeates all space).
Einstein showed that mass is a form of energy, and that mass can be turned into pure energy and energy into mass. As an example, an electron and a positron can annihilate and create two photons.
Similarly photons can interact and become an electron-positron pair, as shown below. Note that in Feynman diagrams antiparticles are represented as going backwards in time.
Feynman diagram of electron (e-) positron (e+) annihilation, producing two photons (y).
Image Credit: bitwise via Wikimedia Commons.
With all of this talk of particles abounding in the universe, you’d think they’d fill up a lot of space, but most of space is empty.
Our everyday experiences are filled with what appears to be solid material to us, but atoms have 99.99% of all their matter in a sphere with a diameter on the order of 10-15 m (a quadrillionth of a meter), yet, with all their electrons, an average atom extends over a size of about 10-10 m (ten billionth of a meter).
This means that the mass of an atom only takes up about a
thousandths quadrillionth of its entire spatial extent, most of it being empty. And beyond our world is a lot of empty space interspersed with planets, stars, and other extraterrestrial objects.
When you think of a vacuum you probably think of a volume of space that contains absolutely nothing. But quantum field theory posits that a vacuum field exists throughout all of space and it consists of constantly fluctuating fields that are zero on the average, but have a non-zero probability to become large.
As a side note, the Higgs field is part of the vacuum field. Particles with mass do so because of their interaction with the Higgs field, which permeates all space.
If a field becomes large at an instant then a pair of particles might pop into existence, which would soon annihilate. The vacuum can also be thought of as particles constantly being created and destroyed. This fits with Heisenberg’s Uncertainty Principle as well. If the lifetime of a particle is short, then its energy (and hence its mass) can be large.
In the 1950’s, scientists observed that there are particles that seem to be fundamental, meaning they are not made of anything else. An example of this is the electron, the muon, and neutrinos. These are called leptons, meaning light particles.
There were other particles found that had properties between those of leptons and protons, neutrons and other more massive particles. These are called mesons meaning middle particles. Examples of mesons are the pion and the rho meson. Mesons are important because they are involved in strong interactions (the type of interaction that holds the nucleus together).
In 1934 Hideki Yukawa theorized that the exchange of mesons was responsible for the strong nuclear force between nucleons, much like atoms absorb and emit electromagnetic energy, nucleons were believed to absorb and emit mesons. This is not true, however the idea that particles are exchanged during an interaction is the basis of quantum electrodynamics (QED) and quantum chromodynamics (QCD). QCD is quark theory.
Particles such as protons and neutrons are called baryons, or heavy particles. It was observed that there is a strong force, a manifestation of the strong interaction that holds the nucleus together.
Hadrons (strong particles) are particles that are involved in strong interactions and consist of mesons and baryons, but it was not understood why these particles were involved in strong interactions. Furthermore, there were some problems with symmetry and conservation rules that were not fitting with what scientists believed should happen. This is where the theory of quarks helped.
Because of issues of symmetry, it was thought that perhaps mesons and baryons were made up of smaller particles. In 1956 Murray Gell-Mann and George Zweig independently came up with a theory of these smaller particles. Gell-Mann named his particle the quark.
The quark was thought to make up mesons and baryons, and if it did exist, it would explain the observations made of baryons and mesons that seemed otherwise to contradict parts of their underlying theories.
It was also believed that gluons would be exchanged during strong force interactions in much the same way that photons are exchanged during electromagnetic interactions.
Assuming symmetrical relationships, gluons would be massless particles traveling at the speed of light that would be absorbed or emitted by quarks. These gluons would also (like photons) be involved in the creation of quarks and the annihilation of quarks.
With the introduction of quarks came a new set of fundamental particles that make up all that we know exists in matter. The table below lists all known elementary particles we know of.
The gauge bosons are the carries of the four fundamental forces of nature. The Z and W particles are exchanged in the electroweak interactions (they act like photons in electromagnetic interactions, however these have mass unlike all the other particles that at as carriers for the fundamental forces of nature).
The Higgs boson is still under scrutiny in the scientific community. The Higgs boson observed in 2013 has not yet been accepted as the one predicted by theory, but it has been accepted as a Higgs boson. Current theories suggest that the Higgs field and its corresponding particle (the Higgs boson) interact with W and Z particles, slowing them down and hence causing them to have mass.
The graviton (a massless particle theorized to be absorbed and emitted during gravitational interactions) has not yet been observed and is not listed below.
Table of quarks, leptons, and bosons.
Image Credit: Fermilab/DOE Office of Science Particle Data Group/PBS NOVA
Our everyday matter can now be described as:
Leptons (light particles) are fundamental particles that cannot be broken down further and do not contain quarks.
Mesons (middle particles) that consist of a quark and an antiquark. All particles have a “twin” particle or anti-particle. These are almost the same. The charge is always opposite in sign and some other characteristics are opposite.
Baryons (heavy particles) that are particles consisting of three quarks. For example the proton is made of two up quarks and a down quark and the neutron is made of an up quark and two down quarks. All baryons are made of three particles. The up and down quarks are the most stable and long-lived quarks found in nature.
Baryons and mesons make up a category of particles called hadrons. Hadrons (strong particles) are involved in strong interactions, which manifests the strong force. The strong force arises from the exchange of gluons.
Quarks have never been found isolated, i.e., just one quark on its own. If one were to try to get one quark on its own by having a high-energy collision, the energy involved to break apart a baryon or meson would be enough to also create sets of quark pairs, so one could not isolate a quark this way.
However, scattering experiments have provided enough evidence of all six types, or flavors, of quarks: up, down, charm, strange, top, and bottom. In the past, top and bottom were called truth and beauty and hence many particle physics groups have the word beauty associated with them.
Quarks also have a special type of charge besides electric charge. This new charge is called color charge, and not because it is associated with a color, but because there are three different types of this new charge and three types for the anti-charge, which lends itself well to the colors of light.
The primary charges are colored red, blue, and green (like the primary colors of light). The anti-colors, carried by anti-quarks, are: anti-blue which is yellow, because yellow light is made of red and green lights only; anti-red which is cyan, because blue and green lights make cyan; and anti-green which is magenta because blue and red lights make magenta.
Again, it is important here to stress that this color charge has nothing to do with light or color. It is some charge characteristic that quarks have that is not the electric charge, and it follows conservation rules like other charged particles.
Gluons also have color charge, and the strong force between quarks is called the color force. Quarks bound in groups always must be colorless, that is, their color charge must add up to make white, meaning there must be a red, green, and blue mixed together. The proton and neutron have this.
Mesons, which are only made of two quarks, then must be made of a quark and an anti-quark which carries an anti-color charge.
Below is a representation of the quarks, and their color charge, of a proton, neutron, and mesons.
From left to right: proton, neutron, pion+ (pi+ meson), with the quark color charge shown. A line above the quark symbol indicates an anti-quark. The squiggly line represents the interchange of gluons.
Image credit: Arpad Horvath via Wikimedia Commons.
In Feynman diagrams we can show how a neutron may undergo beta decay and turn into a proton, emitting an electron and neutrino. In the decay process, a down quark decays into an up quark emitting a W− particle. The W− particle then decays into an electron and a neutrino.
Feynmann diagram of beta decay.
Image credit: Joel Holdsworth via Wikimedia Commons.
This is the traditional quark model, and what is now called the standard model. It has had plenty of evidence to back it up, although there are a few things that have suggested that perhaps particle physicists don’t have it all figured out yet.
For example, the current standard model works great for hadrons made of two and three quarks. More quarks in one particle was not believed to occur, and was never observed — that is until recently.
The Tetraquark Emerges
Particles that seemed to deviate from the traditional quark model, in that they contained four quarks, were first observed in 2003. But there’s been insufficient evidence to claim a tetraquark exists — at least until now.
There were other claims in 2008 from CERN’s Large Hadron Collidor (LHC) and Japan’s Belle that pointed toward a tetraquark, and even a possible pentaquark observation, but none was sufficient enough to pass the required scientific criteria. That is until work published in April 2014 by the Large Hadron Collider Beauty experiment (LHCb) collaboration.1,2
The LHCb colloboration reported “unambiguously” finding the Z(4430)−, a particle of mass 4430 MeV or 4.756 u = 7.897 * 10-27 kg, and a negative electric charge equal to that of an electron. But what does “unambiguously” mean? It means that they put an extremely high criteria on finding it, and that it was observed in many more instances than the criteria they placed.
Particle physicists often describe the statistical significance of their measurements in terms of the standard deviation. The standard deviation is a measure of the variation in the data. When scientists use standard deviations to describe the significance of their results it means they are describing the probability of their measurements versus seeing such measurements by chance or by some other anomaly.
In every day terms, 2 sigma (2σ) means, ± 2 standard deviations of a normal curve, which encompasses 95.4% of the data, as shown below, with 4.6% on the sides. In most instances if you have found something to within 5% it means you are 95% sure that your measurements are valid and true, and 5% might be a fluke. Overall you have pretty good statistics backing you up.
If you have 3σ (3 on each side of the center as shown below) then you are up to 99.6% certain of your measurements. Note also that this is a two sided curve, meaning that one considers the standard deviations symmetrically.
Image of the normal distribution showing 3 standard deviations on each side of the mean value.
Image credit: Mwtoews vs Wikimedia Commons
Particle physicists tend to put a lower limit of 5σ on their findings, and often they are one sided curves, meaning they just consider the probability of chance at one end of the curve because the other side can be ruled out.
For the Higgs Boson that was recently found, it was 5σ above the mean, which means they only need to look at the little amount on the right side of the curve as the chance part. The probability of the observation occurring by chance or some fluke is then 1 in 3.5 million, and the scientists are 99.99997% sure they have found a valid measurement of a particle.
If it were a two-sided normal curve, and they could not rule out one side of the curve, then it would have been a 1 in 1.75 million chance. If they can do better than 5σ, then it is even more likely that they have found what they say they have found.
This tetraquark was found to be within 13.9σ. Consequently, the scientists are all but certain that their measurements are real and not a fluke.
They were able to obtain such high levels of certainty because they were able to produce more than 180 million collisions, which resulted in 25,200 observable decays to analyze. With so much data, they were able to determine a lot about this particle.
This particle’s measured mass is about 4.72 times more massive than the proton. From observations of the decay chain the researchers could rule out certain quantum numbers describing the particle by conservation laws. From their measurements they determined this particle to have a spin-parity of 1+, meaning if it is made up of quarks it must be made up of an even number since quarks have spin ½.
They also determined that the smallest number of quarks, and type of quarks that can make this particle are four quarks: charm, anti-charm, down, and anti-up, or:
This discovery has upended the traditional view that particles can’t be made of more than three quarks. Even though this particle was short-lived, it was clearly measured and clearly existed for some time. More than three quarks can combine to form a particle, and particle physicists will continue to try to understand the building blocks of all we know.
References and Resources1. Large Hadron Collider Beauty Experiment webpage, April 9, 2014 posting
2. LHCb collaboraion: Aaij, R. et al. Observation of the resonant character of the Z(4430)− state, Submitted to Physical Review Letters April 2014
3. Nambu, Y. Quarks, Frontiers in Elementary Particle Physics, World Scientific, Philadelphia (1985)
4. Giancoli, Physics, Sixth Ed., Ch 32, Pearson (2005)
5. Lamb, E., 5 Sigma – What’s That?, Scientific American, Observations Blog, 17 July 2012
6. David, Higgs: Is it one-sided or two-sided, Understanding Uncertainty, 7 March 2012.
“Produced by the Winton programme for the public understanding of risk based in the Statistical Laboratory in the University of Cambridge.”
Appendix: Particle Physics Background History
Although the ancient Greeks didn’t have access to vast particle colliders, they were still very interested in the smallest building blocks of the material world. The Greek Philosopher Democritus (460-370 BCE) and his mentor Leucippus, theorized that all matter was made up indivisible and unchanging elements they called atoms. Before 1900, however, not much was known about the parts of the atom as we know it today.
The electron was discovered in 1897, and scientists believed that electrons and positively charged objects mixed together like plum pudding to form an atom. This “plum pudding” model, took precedence until around 1911 when evidence pointed to a centralized, dense, and positively charged part of the atom.
Evidence suggested that positively charged particles incident on a thin sheet of metal foil usually went through the foil, but sometimes they bounced back at large angles. The conservation of momentum requires that the sum of the momenta in each direction of all the particles involved in a collision must be the same before and after the collision.
The momentum of a particle is simply its mass multiplied by its velocity. Using the conservation of momentum, physicists found that the incoming charged particles must have collided or interacted with something massive, positively charged, and concentrated in a tiny space.
Ernest Rutherford believed this to be where all the protons in an atom were located, with the electrons orbiting this massive center, much like planets orbit the Sun. The nucleus of an atom was discovered around 1911, and the proton (a hydrogen nucleus) was discovered in 1918. The neutron wasn’t even theorized until 1920, when studies found that the same atomic element sometimes had a different mass.
With the photoelectric effect and early quantum theorems between 1900-1920 came the idea that light, and all electromagnetic waves, could act as a particle called a photon. A photon is a discrete packet of energy. One of the patterns we find in nature is that nature is symmetric.
Based on this, Louis de Broglie in 1923 theorized that if electromagnetic waves could act like particles, then particles could act like waves. This provided an explanation for some concerns at the time for the orbital model of the atom. It is also a key part of quantum mechanics. Because of this inherent wave nature of matter, there is a limit on how well we can simultaneously know certain quantities that describe a particle.
This limit is called Heisenberg’s Uncertainty Principle, which puts a lower limit on how well we can simultaneously know a particle’s location and momentum, and also its energy at a given time.
In 1932, the neutron was discovered in experiments. Neutrons act as a buffer between protons. At this point, the core parts of the modern atom were finally known while elements, and their isotopes, were being discovered.
The nucleus does not fly apart, even though there are plenty of positively charged protons in it, and scientists had long-known that like charges repel (electromagnetic force). The neutrons in the nucleus were thought to be helpful in buffering the situation, but a new force was needed, and one that was significantly stronger than the electromagnetic force.
This new force was called the strong nuclear force. From observations, scientists determined that this force is extremely strong at distances on the order of 10-15 m (a femtometer) or a quadrillionth of a meter — roughly the size of the nucleus. At larger distances, the force is negligible.
Still more particles were being observed. In 1932, scientists also discovered the positron: a positively charged particle otherwise identical to the electron and the first “anti-matter” particle to be observed.
By 1933, much had been learned about radioactive decay, and Enrico Fermi introduced the idea that another force must be responsible for these decay processes and fusion processes. He called it the weak nuclear force. In 1968, it was theorized that the weak nuclear force and the electromagnetic force were both manifestations of a single force now called the electro-weak force.
In 1936 scientists discovered the muon, found in cosmic rays. Muons have all the same properties as electrons except their mass is about 206 times that of an electron. Next came neutrinos, theorized between 1930 and 1970, and discovered between 1956 and 2000. In 1950 the lambda baryon was discovered, and the sigma baryon was discovered. Particle accelerators were being built in the 1930s and the early description of particle theory was forming. | 0.826727 | 3.909768 |
October 22, 2015 – Observations by the NASA/ESA Hubble Space Telescope have taken advantage of gravitational lensing to reveal the largest sample of the faintest and earliest known galaxies in the Universe. Some of these galaxies formed just 600 million years after the Big Bang and are fainter than any other galaxy yet uncovered by Hubble. The team has determined, for the first time with some confidence, that these small galaxies were vital to creating the Universe that we see today.
An international team of astronomers, led by Hakim Atek of the Ecole Polytechnique Fédérale de Lausanne, Switzerland, has discovered over 250 tiny galaxies that existed only 600-900 million years after the Big Bang — one of the largest samples of dwarf galaxies yet to be discovered at these epochs. The light from these galaxies took over 12 billion years to reach the telescope, allowing the astronomers to look back in time when the universe was still very young.
Although impressive, the number of galaxies found at this early epoch is not the team’s only remarkable breakthrough, as Johan Richard from the Observatoire de Lyon, France, points out, “The faintest galaxies detected in these Hubble observations are fainter than any other yet uncovered in the deepest Hubble observations.”
By looking at the light coming from the galaxies the team discovered that the accumulated light emitted by these galaxies could have played a major role in one of the most mysterious periods of the Universe’s early history — the epoch of reionisation. Reionisation started when the thick fog of hydrogen gas that cloaked the early Universe began to clear. Ultraviolet light was now able to travel over larger distances without being blocked and the Universe became transparent to ultraviolet light.
By observing the ultraviolet light from the galaxies found in this study the astronomers were able to calculate whether these were in fact some of the galaxies involved in the process. The team determined, for the first time with some confidence, that the smallest and most abundant of the galaxies in the study could be the major actors in keeping the Universe transparent. By doing so, they have established that the epoch of reionisation — which ends at the point when the Universe is fully transparent — came to a close about 700 million years after the Big Bang.
Lead author Atek explained, “If we took into account only the contributions from bright and massive galaxies, we found that these were insufficient to reionise the Universe. We also needed to add in the contribution of a more abundant population of faint dwarf galaxies.”
To make these discoveries, the team utilised the deepest images of gravitational lensing made so far in three galaxy clusters, which were taken as part of the Hubble Frontier Fields program. These clusters generate immense gravitational fields capable of magnifying the light from the faint galaxies that lie far behind the clusters themselves. This makes it possible to search for, and study, the first generation of galaxies in the Universe.
Jean-Paul Kneib, co-author of the study from the Ecole Polytechnique Fédérale de Lausanne, Switzerland, explains, “Clusters in the Frontier Fields act as powerful natural telescopes and unveil these faint dwarf galaxies that would otherwise be invisible.”
Co-author of the study Mathilde Jauzac, from Durham University, UK, and the University of KwaZulu-Natal, South Africa, remarks on the significance of the discovery and Hubble’s role in it,“Hubble remains unrivalled in its ability to observe the most distant galaxies. The sheer depth of the Hubble Frontier Field data guarantees a very precise understanding of the cluster magnification effect, allowing us to make discoveries like these.”
These results highlight the impressive possibilities of the Frontier Fields program with more galaxies, at even earlier time, likely to be revealed when Hubble peers at three more of these galaxy clusters in the near future. | 0.830285 | 4.082412 |
On Oct. 13, 2014, something very strange happened to the camera aboard NASA’s Lunar Reconnaissance Orbiter (LRO). The Lunar Reconnaissance Orbiter Camera (LROC), which normally produces beautifully clear images of the lunar surface, produced an image that was wild and jittery. From the sudden and jagged pattern apparent in the image, the LROC team determined that the camera must have been hit by a tiny meteoroid.
LROC is a system of three cameras mounted on the LRO spacecraft. Two Narrow Angle Cameras (NACs) capture high resolution black and white images. The third Wide Angle Camera captures moderate resolution images using filters to provide information about the properties and color of the lunar surface.
The NAC works by building an image one line at a time. The first line is captured, then the orbit of the spacecraft moves the camera relative to the surface, and then the next line is captured, and so on, as thousands of lines are compiled into a full image.
According to Mark Robinson, professor and principal investigator of LROC at ASU’s School of Earth and Space Exploration, the jittery appearance of the image captured is the result of a sudden and extreme cross-track oscillation of the camera. LROC researchers concluded that there must have been a brief violent movement of the left Narrow Angle Camera.
There were no spacecraft events like solar panel movements or antenna tracking that might have caused spacecraft jitter during this period. “Even if there had been, the resulting jitter would have affected both cameras identically,” Robinson said. “The only logical explanation is that the NAC was hit by a meteoroid.”
During LROC’s development, a detailed computer model was made to ensure the NAC would not fail during the severe vibrations caused by the launch of the spacecraft. The computer model was tested before launch by attaching the NAC to a vibration table that simulates launch. The camera passed the test with flying colors, proving its stability.
Using this detailed computer model, the LROC team ran simulations to see if they could reproduce the distortions seen on the Oct. 13 image and determine the size of the meteoroid that hit the camera. They estimate the impacting meteoroid would have been about half the size of a pinhead (0.8mm), assuming a velocity of about 4.3 miles (7 kilometers) per second and a density of an ordinary chondrite meteorite (2.7 grams/cm3).
“The meteoroid was traveling much faster than a speeding bullet,” Robinson said. “In this case, LROC did not dodge a speeding bullet, but rather survived a speeding bullet!”
How rare is it that the effects of an event like this were captured on camera? Very rare, according to Robinson. LROC typically only captures images during daylight and then only about 10 percent of the day, so for the camera to be hit by a meteor during the time that it was also capturing images is statistically unlikely.
“LROC was struck and survived to keep exploring the moon,” Robinson said, “thanks to Malin Space Science Systems’ robust camera design.”
“Since the impact presented no technical problems for the health and safety of the instrument, the team is only now announcing this event as a fascinating example of how engineering data can be used, in ways not previously anticipated, to understand what is happing to the spacecraft over 236,000 miles (380,000 kilometers) from the Earth," said John Keller, LRO project scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Launched on June 18, 2008, LRO has collected a treasure trove of data with its seven powerful instruments, making an invaluable contribution to our knowledge about the moon.
“A meteoroid impact on the LROC NAC reminds us that LRO is constantly exposed to the hazards of space,” said Noah Petro, deputy project scientist from NASA Goddard. “And as we continue to explore the moon, it reminds us of how precious are the data that is being returned.”
LRO is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland, as a project under NASA's Discovery Program. The Discovery Program is managed by NASA's Marshall Spaceflight Center in Huntsville, Alabama, for the Science Mission Directorate at NASA Headquarters in Washington.
The Lunar Reconnaissance Orbiter Camera was developed at Malin Space Science Systems in San Diego, California and Arizona State University.
The first wild back-and-forth line records the moment the left NAC radiator was struck by a meteoroid. Credit: NASA/Goddard Space Flight Center/Arizona State University | 0.812357 | 3.723489 |
Gamma rays are the highest energy photons on the electromagnetic spectrum. Their wavelength is similar to the size of an atom, and when two of them collide they tend to produce a matter-antimatter particle pair. They represent energy high enough to synthesize the fundamental particles of matter, and are produced in the highest energy environments in the cosmos. The interchange of matter and energy works both ways, so one of the ways gamma rays are generated is through annihilation of a matter-antimatter particle pair. Looking back to the beginning of the universe it gives us the earliest ‘chicken or egg’ dichotomy, but that is a topic for another time.
Gamma rays in the universe are produced by pulsars, supernovae and their remnants, and active galactic nuclei (galaxies with supermassive black holes). But there are other sources that were surprising, and we’re still unsure what some of them are.
Recently, a new gamma ray source was detected that confirms scientists’ long-standing suspicions – Colliding stellar winds from massive binary systems is producing gamma rays.
Stellar winds are not winds in the traditional sense. They are waves of charged particles, electrons and protons, radiated away by the strong magnetic fields of stars. The winds from our Sun are the result of solar flares and chaotic magnetic loops, and the end result is the gorgeous aurora that we see here on Earth.
But the stellar winds from the Sun are weak in comparison to that of massive stars, which have stronger magnetic fields, more intense flares, and release a consistently dense blast of charged particles into space. Now imagine putting two of these stars in a close orbit, both firing stellar winds off in all directions. The shock barrier where the winds from the two stars meet is colliding the charged particles together in a way that is similar to a supercollider on Earth, like the Large Hadron Collider at CERN.
The result is the production of gamma rays that are fired off in all directions, some of which make it to Earth to explain the source we see. The well known example of a gamma ray producing binary is Eta Carinae, a massive pair of stars in the southern sky. The stars weigh 120 and (30-80) solar masses respectively, and have a power output millions of times greater than the Sun. but it was the discovery of a second binary system producing gamma rays that confirms them as a standard source.
Moving forward, astronomers will look at more examples of massive binaries, while trying to characterize all of the strong gamma ray sources seen by Fermi. Looking at the universe across the electromagnetic spectrum let’s us understand its evolution as a whole, allowing us to do what science does best. Explain the past, understand the present, and predict the future. | 0.833701 | 4.137822 |
Astronomers using ALMA have detected various complex organic molecules around the young star V883 Ori. A sudden outburst from this star is releasing molecules from the icy compounds in the planet forming disk. The chemical composition of the disk is similar to that of comets in the modern Solar System. Sensitive ALMA observations enable astronomers to reconstruct the evolution of organic molecules from the birth of the Solar System to the objects we see today.
The research team led by Jeong-Eun Lee (Kyung Hee University, Korea) used the Atacama Large Millimeter/submillimeter Array (ALMA) to detect complex organic molecules including methanol (CH3OH), acetone (CH3COCH3), acetaldehyde (CH3CHO), methyl formate (CH3OCHO), and acetonitrile (CH3CN). This is the first time that acetone was unambiguously detected in a planet forming region or protoplanetary disk.
Various molecules are frozen in ice around micrometer-sized dust particles in protoplanetary disks. V883 Ori's sudden flare-up is heating the disk and sublimating the ice, which releases the molecules into gas. The region in a disk where the temperature reaches the sublimation temperature of the molecules is called the "snow line." The radii of snow lines are about a few astronomical units (au) around normal young stars, however, they are enlarged almost 10 times around bursting stars.
"It is difficult to image a disk on the scale of a few au with current telescopes," said Lee. "However, around an outburst star, ice melts in a wider area of the disk and it is easier to see the distribution of molecules. We are interested in the distribution of complex organic molecules as the building blocks of life."
Ice, including frozen organic molecules, could be closely related to the origin of life on planets. In our Solar System, comets are the focus of attention because of their rich icy compounds. For example, the European Space Agency's legendary comet explorer Rosetta found rich organic chemistry around the comet Churyumov-Gerasimenko. Comets are thought to have been formed in the outer colder region of the proto-Solar System, where the molecules were contained in ice. Probing the chemical composition of ice in protoplanetary disks is directly related to probing the origin of organic molecules in comets, and the origin of the building blocks of life.
Thanks to ALMA's sharp vision and the enlarged snow line due to the flare-up of the star, the astronomers obtained the spatial distribution of methanol and acetaldehyde. The distribution of these molecules has a ring-like structure with a radius of 60 au, which is twice the size of Neptune's orbit. The researchers assume that inside of this ring the molecules are invisible because they are obscured by thick dusty material, and are invisible outside of this radius because they are frozen in ice.
"Since rocky and icy planets are made from solid material, the chemical composition of solids in disks is of special importance. An outburst is a unique chance to investigate fresh sublimates, and thus the composition of solids." says Yuri Aikawa at the University of Tokyo, a member of the research team.
V883 Ori is a young star located at 1300 light-years away from the Earth. This star is experiencing a so-called FU Orionis type outburst, a sudden increase of luminosity due to a bursting torrent of material flowing from the disk to the star. These outbursts last only on the order of 100 years, therefore the chance to observe a burst is rather rare. However, since young stars with a wide range of ages experience FU Ori bursts, astronomers expect to be able to trace the chemical composition of ice throughout the evolution of young stars. | 0.847447 | 4.071933 |
The most distant object that NASA has ever investigated up close, 2014 MU69, orbits near the edge of the solar system, well beyond Pluto. Because of the desolate conditions out there, it’s remained virtually unchanged since the beginning of the solar system. Less than five years ago, astronomers didn’t even know it existed. Now they know what it looks like, thanks to images captured by a passing spacecraft.
The New Horizons spacecraft arrived at 2014 MU69—4 billion miles away from Earth—on New Year’s Eve, snapped hundreds of photographs, and then continued on, headed even deeper into space. On Wednesday, NASA released the first set of photographs.
Seen from Earth, 2014 MU69 looks like a tiny speck of light. Up close, it resembles, delightfully, a snowman.
2014 MU69 is so far away, details like this could never come into focus from Earth.“There’s no way to make anything like this, this type of observation, without having a spacecraft there,” Cathy Olkin, the deputy project scientist, told reporters at a press conference on Wednesday.
In 2015, New Horizons flew past Pluto and revealed a stunning icy world with towering mountains, smooth plains, and a feathery atmosphere. The probe had enough fuel to keep going after the encounter, and 2014 MU69 turned out to be along its path.
Nicknamed Ultima Thule, Latin for “beyond the known world,” the object is a contact binary, a cosmic configuration in which two separate objects become joined together. “They obviously came together at such a gentle speed—maybe a mile an hour, or a few miles an hour,” said Jeff Moore, the head of the geology team for New Horizons. “They really are sort of resting on each other.”
The snowman description is fitting for the conditions in the Kuiper Belt, where frozen bits and pieces left over from the formation of the solar system 4.6 billion years ago abound, receiving very little sunlight. It’s an incredibly cold place: The surface temperature of Pluto, the largest object in the region, is nearly –400 degrees Fahrenheit. If you could somehow build Frosty the Snowman out there, he’d last forever.
Unlike typical snowmen, Ultima Thule is red, roasted and darkened over time by cosmic radiation. Below, the photo on the right is a composite image from two of the three cameras aboard New Horizons. (The color looks more like iced coffee with a little half-and-half to me, but by planetary-science measures, it’s red.)
There’s more than one kind of ice in the universe, and the flyby data haven’t yet revealed the composition of Ultima Thule. The object may be made of water ice, nitrogen ice, or methane ice.
Ultima Thule is frozen another way—in time. The frigidness of the Kuiper Belt has kept Ultima Thule in pristine shape. The New Horizons data will describe the very material that shaped Earth and the other planets, and scientists hope the spacecraft’s scientific instruments collected some new information about this chapter in our cosmic history.
The newly released images are the first of many still to come. These were taken about a half hour before New Horizons made its closest approach to Ultima Thule, and at a moment when sunlight struck the object head-on. As the spacecraft flew past, the illumination shifted, and shadows emerged. It’s these shadows, scientists say, that will soon reveal whether Ultima Thule has hills, ridges, or craters.
It takes some time for data from New Horizons to reach Earth from a distance of 4 billion miles. Scientists will reveal the best, highest-resolution photographs in the coming weeks and months.
An uncomfortable question, unrelated to the science, hovered over the New Horizons team’s presentation on Wednesday. On Tuesday night, a Newsweek story from March prompted discussion on social media about NASA’s decision to use the name Ultima Thule, which arose out of a public naming contest. The term was coined more than 2,000 years ago by the Roman poet Virgil and has appeared frequently in literature as a descriptor for distant, mythical lands. Newsweek pointed out that the term was also adopted by the Nazi party as the name of a mythical Aryan homeland.
NASA officials were aware of this historical usage when they chose Ultima Thule and decided its ancient meaning outweighed the troubling connotations. “I think New Horizons is an example, one of the best examples, in our time of raw exploration, and the term Ultima Thule—which is very old, many centuries old, possibly over 1,000 years old—is a wonderful meme for exploration,” Alan Stern, the lead investigator of the New Horizons mission, said in response to a question from a reporter. “And that’s why we chose it. And I would say that just because some bad guys once liked the term, we’re not going to let them hijack it.”
But this shadow couldn’t dampen the jubilance in the room as the scientists shared the shape of their new discovery. To anyone used to the smooth, rounded architecture of planets and moons, this distant world might look funky. But the solar system is flush with oddly shaped clumps that don’t fit into neat schemes.
Billions of years ago, some of the material hurtling around the sun began to collide together. The gentler collisions allowed clumps of material to grow with each merger. Small clumps led to big clumps, and if they grew large enough, gravity tugged at their edges and collapsed them into spheres. Ultima Thule, about the size of a city, is too small for this effect.
“Most of the small bodies in the solar system are highly elongated,” Hal Weaver, the New Horizons project scientist, explained recently. “They just don’t have enough mass to form themselves into a perfect sphere.”
New Horizons is now headed deeper into the Kuiper Belt. The spacecraft left Earth in 2006 and, despite a few malfunctions along the way, remains healthy. Stern predicts it could keep going for another 15 to 20 years and plans to submit a new exploration proposal to NASA leadership. With Ultima Thule in the rearview, the spacecraft may set its sights on another target, prepared to extend humanity’s reach into the cosmos even further.
We want to hear what you think about this article. Submit a letter to the editor or write to [email protected]. | 0.88421 | 3.601293 |
On March 20th this year, the moon will pass between Earth and the Sun sending a slither of Northern Europe into darkness. For those in the UK, this partial eclipse will be the most impressive eclipse until three minutes of totality at 4:56pm on September 23rd, 2090. Calculating something so far ahead seems like an impressive feat but in fact astronomers can precisely work out exactly when and where eclipses will occur for not just the next hundred, but the next million years. Such is the way for most transiting exoplanets too, the calculations for which could probably be valid in thousands of years.
But a new planetary system, discovered by a team that includes Warwick astronomers (including me), doesn’t yet play by these rules. It consists of two planets orbiting their star, a late K star smaller than our sun, in periods of 7.9 and 11.9 days. The pair have radii 7- and 4-larger than Earth, putting them both between the sizes of Uranus and Saturn. They are the 4th and 5th planets to be confirmed in data from K2, the rejuvenated Kepler mission that monitors tens of thousands of stars looking for exoplanetary transits. (36 other planet candidates, including KIC201505350b & c, have been released previously).
But it is their orbits, rather than planetary characteristics, that have astronomers most excited. “The periods are almost exactly in a ratio of 1.5” explains Dave Armstrong, lead author of the study. This can be seen directly in how the star’s brightness changes over time. This lightcurve appears to have three dips of different depths, marked here by green, red and purple dips. ”Once every three orbits of the inner planet and two orbits of the outer planet, they transit at the same time”, causing the deep purple transits.
But this doesn’t just make for an interesting lightcurve; the closeness of these periods to a 3/2 ratio also causes other weird effects. “The planets perturb each other and change their period every orbit, so they never quite transit when you expect”, explains Arms. These shifts are called Transit Timing Variations (or TTVs).
The size of these TTVs is related to the mass of the planets, and some previous multi-planet systems have been weighed in this way. When the team went back to observe the larger planet less than 9 months later, they found that the transit time had shifted by more than an hour. And their period ratio of 1.5035 means the resulting TTVs are likely to continue increasing over a few years, potentially shifting the system more than a day from it’s current rhythm.
These TTVs also help prove that the planets are real. Their presence means that both objects are interacting with each other, so the planets must orbit the same star rather than being, say, two different background binaries. The team also used these shifts in transit time to constrain the planet masses, showing them to be less than 1.2 and 2.04 times that of Jupiter.
Not only is this one of the most interesting multi-planet systems yet discovered by Kepler, it is also one of the brightest (12th magnitude), making ground-based follow-up much easier than many Kepler systems. Most interestingly, precise spectrographs like HARPS and SOPHIE will be able to measure the tiny to-and-fro shift in the star’s velocity caused by the gravitation pull of planet on the star. This radial velocity would give a precise mass for the planets in the system and for the first time allow masses found by TTVs to be directly compared to those from RVs.
Examples of 3:2 resonance can be found everywhere in planetary science, including between Pluto & Neptune’s orbits, in the Kirkwood gap of the Asteroid Belt, and even between the planets around pulsar PSR1257+12. It is also thought that Jupiter and Saturn may have, at one point, become caught in a 3:2 resonance as they migrated inwards. This scenario, of planets caught in 3:2 resonance migrating inwards, could explain how these two sub-Jupiter sized planets came to be in such an unusual orbit.
These two planets could also help settle other dilemmas. “We’d like to answer questions like ‘Did they form there?’, ‘Did they migrate there and get stuck?’ and ‘will they eventually get ejected from the system, or crash into the star?’” suggests Armstrong. The best way to do this is simply by watching future transits and monitoring just how in-sync the planets really are. And maybe one day we could even begin to predict their eclipses as confidently as we can with those happening here on Earth.
The paper, submitted to A&A, can be found on ArXiV here. My work on the paper involved developing the tools to find the transiting planets in the K2 lightcurve. | 0.90333 | 3.947013 |
A world leader in modern cosmology and one of the most creative and significant theoreticians in modern astronomy. Her scientific work has been described by biographer Christine Cole Catley in The Book of New Zealand Women: Ko Kui Ma Te Kaupapa as “opening doors to the future study of the evolutions of stars, galaxies and even the Universe itself.” Beatrice Tinsley has profoundly affected what scientists know about the origin and size of the universe.
Tinsley’s research on how galaxies change and evolve over time changed the standard method for determining distances to far galaxies which, in turn, was significant in determining the size of the universe and its rate of expansion. At the time it was assumed that galaxies of the same type – spiral, elliptical or lenticular – would be a similar size, shape and luminosity. By comparing the size and luminosity of distant galaxies to nearby galaxies whose distance was already known, it was thought that an accurate distance could be obtained.
“Extraordinary and Profound”
The central tenet of Tinsley’s 1966 Ph.D thesis “Evolution of Galaxies and its Significance for Cosmology”, a dissertation described as “extraordinary and profound” by her professors at the University of Texas at Austin, was that internal changes owing to the evolution of stellar and non-stellar material occur in galaxies over long periods, so that determining distances based on morphology alone was unreliable. Factors such as the abundances of chemical elements, the mass of the galaxy and the rate of starbirth were all important parameters in determining the distance and age of the galaxy and, by inference, the size and age of the universe. Tinsley’s work formed the basis for contemporary studies of galactic evolution.
Beatrice Hill was born in 1941 in Chester, northwest England, the second daughter of an Anglican minister father and writer mother. After the war the family moved to New Zealand, first to Christchurch and then settled in New Plymouth, where Beatrice’s father was mayor for three years. At New Plymouth Girl’s High School, she was a brilliant student in a number of fields, excelling in mathematics, languages, writing and music (she played violin for the National Youth Orchestra for two years). However, at the age of 14 she decided that she wanted to be an astrophysicist. She graduated from New Plymouth Girls’ High School as Dux at 16, won a junior scholarship and went to Canterbury University to study mathematics, chemistry and physics. She completed a Master of Science with First Class Honours in Physics in 1961, marrying fellow physics student Brian Tinsley in the same year. After graduating, Brian was offered a job at the South West Centre for Advanced Studies, in Dallas, Texas and the couple moved there.
Unappreciated and unable to find a job in the macho atmosphere of Dallas, Beatrice took a part-time job teaching at the University of Texas at Austin, some 200 miles away. She enrolled for a Ph.D at Austin in 1964 and completed it in 1966, taking about a third of the time it takes most people to do a Ph.D thesis. In her papers she received marks of 99% and 100%, the first student in the department to achieve marks of over 80%.
The main strands of her research were into the evolution of galaxies and the stars within them, culminating in the idea that galaxies undergo significant changes over a relatively short time span (short, that is, compared to the age of the universe). She pioneered models of galactic evolution “more realistic than other models at the time, which combined a detailed understanding of stellar evolution with knowledge of the motions of stars and nuclear physics”, as described by a website biography (set up by San Francisco State University). Her models formed the basis of the first pictures of what “protogalaxies” (galaxies in their infancy) might look like.
Origin of the Universe
Her work on how the evolution of galaxies affects the origin and size of the universe had a profound effect on scientific knowledge. She also contributed to research to find out whether the universe is an open or closed system (that is, whether it has boundaries at the edges or whether it is able to keep expanding ad infinitum).
In 1974, her achievements led to her being awarded the Annie J Cannon Prize from the American Astronomical Society and the American Association of University Women, for her contributions to astronomy.
Yet professional recognition was still unforthcoming in Texas. As Catley quotes, stifled and intellectually unfulfilled, Tinsley wrote to her father: “The University of Texas in Dallas has kept me at the nearest possible level to nothing.” In spite of being asked to design an astronomy department for the University of Texas, and in spite of her startling scientific achievements, she was still not treated with professional respect by the university: her application for the job as head of the university’s astronomy department was not even answered.
She had reached a point in her life where she had to choose between staying in Texas with her family and saying goodbye to her scientific career, or taking the hard and less socially accepted road towards fulfilling her scientific promise. Knowing that she would never be taken seriously in Texas, she sought a divorce from her husband in 1974 and left Texas, taking a one year fellowship at the Lick Observatory, at the Santa Cruz campus of the University of California.
The following year she started to work as an assistant professor at Yale University and in 1978 became professor of astronomy at the university. It was in the same year that she discovered she had developed a malignant form of cancer, melanoma. She continued to research and publish papers, until shortly before her death, on 23rd March 1981.
Over a relatively short academic career of 14 years, Professor Tinsley authored or co-authored around 100 scientific papers, mostly concerned with the evolution of galaxies. In addition she was a valuable mentor to younger women scientists in America and New Zealand, particularly during her tenure as professor at Yale. She was gifted and dedicated as a teacher and mentor, as well as a scientist, qualities that were recognised during her tenure at Yale, before her untimely death.
In 1986, as a tribute to her, the American Astronomical Society established the Beatrice M. Tinsley Prize for outstanding creative contributions to astronomy or astrophysics. It was the only major award created by an American scientific society honouring a woman scientist. Her alma mater, the University of Texas at Austin, also created the Beatrice M Tinsley Visiting Professorship in astronomy in her honour.
Her achievements were recognised by New Zealand in early 2011, when the New Zealand Geographic Board named a Fiordland mountain in her honour. Mt Tinsley, standing at 1,537m, is found within the Kelper mountain range 15km west of Te Anau. Mt Tinsley lies a mere 5km from the newly named Mt Pickering – honouring Sir William Pickering, another famous New Zealand astronomer and fellow NZEdge hero.
In the meantime, to learn more about Beatrice Tinsley, you can look at:
Bowman, G. (1988) “Why does science get the female thumbs down?” New Zealand Woman’s Weekly, May 30, pp.14-16.
Catley, C.C. (1985) “Beatrice Hill Tinsley”, Springboard for Women. Picton, Cape Catley Ltd.
Catley, C.C. (1991) “Beatrice Tinsley” in Macdonald, C. Penfold, M & Williams, B. eds. The Book of Women in New Zealand: Ko Kui Ma Te Kaupapa. Wellington, Bridget Williams Books.
Catley, C.C. (1993) “Beatrice Tinsley”, New Zealand Official Yearbook. Wellington, Department of Statistics.
Catley, C.C. (2006) Bright Star: Beatrice Hill Tinsley, Astronomer. Auckland, Cape Catley Ltd.
Hill, E. (1986) My daughter, Beatrice Tinsley. New York. | 0.827313 | 3.53411 |
In fact, you’re doing it right now. Every single second of every single day you are advancing into your own future. You are literally moving through time, the same way you would move through space. It may seem pedantic, but it’s a very important point. Movement through time is still movement, and you are reaching your own future (whether you like it or not).
During the 1930s, venerable theoretical physicist Albert Einstein returned to the field of quantum mechanics, which his theories of relativity helped to create. Hoping to develop a more complete theory of how particles behave, Einstein was instead horrified by the prospect of quantum entanglement – something he described as “spooky action at a distance”.
Despite Einstein’s misgivings, quantum entanglement has gone on to become an accepted part of quantum mechanics. And now, for the first time ever, a team of physicists from the University of Glasgow took an image of a form of quantum entanglement (aka. Bell entanglement) at work. In so doing, they managed to capture the first piece of visual evidence of a phenomenon that baffled even Einstein himself.
Special Relativity. It’s been the bane of space explorers, futurists and science fiction authors since Albert Einstein first proposed it in 1905. For those of us who dream of humans one-day becoming an interstellar species, this scientific fact is like a wet blanket. Luckily, there are a few theoretical concepts that have been proposed that indicate that Faster-Than-Light (FTL) travel might still be possible someday.
A popular example is the idea of a wormhole: a speculative structure that links two distant points in space time that would enable interstellar space travel. Recently, a team of Ivy League scientists conducted a study that indicated how “traversable wormholes” could actually be a reality. The bad news is that their results indicate that these wormholes aren’t exactly shortcuts, and could be the cosmic equivalent of “taking the long way”!
In April of 2016, Russian billionaire Yuri Milner announced the creation of Breakthrough Starshot. As part of his non-profit scientific organization (known as Breakthrough Initiatives), the purpose of Starshot was to design a lightsail nanocraft that would be capable of achieving speeds of up to 20% the speed of light and reaching the nearest star system – Alpha Centauri (aka. Rigel Kentaurus) – within our lifetimes.
At this speed – roughly 60,000 km/s (37,282 mps) – the probe would be able to reach Alpha Centauri in 20 years, where it could then capture images of the star and any planets orbiting it. But according to a recent article by Professor Bing Zhang, an astrophysicist from the University of Nevada, researchers could get all kinds of valuable data from Starshot and similar concepts long before they ever reached their destination.
To recap, Breakthrough Starshot seeks to leverage recent technological developments to mount an interstellar mission that will reach another star within a single generation. The spacecraft would consist of an ultra-light nanocraft and a lightsail, the latter of which would accelerated by a ground-based laser array up to speeds of hundreds of kilometers per second.
Such a system would allow the tiny spacecraft to conduct a flyby mission of Alpha Centauri in about 20 years after it is launched, which could then beam home images of possible planets and other scientific data (such as analysis of magnetic fields). Recently, Breakthrough Starshot held an “industry day” where they submitted a Request For Proposals (RFP) to potential bidders to build the laser sail.
According to Zhang, a lightsail-driven nanocraft traveling at a portion of the speed of light would also be a good way to test Einstein’s theory of Special Relativity. Simply put, this law states that the speed of light in a vacuum is constant, regardless of the inertial reference frame or motion of the source. In short, such a spacecraft would be able to take advantage of the features of Special Relativity and provide a new mode to study astronomy.
Based on Einstein’s theory, different objects in different “rest frames” would have different measures of the lengths of space and time. In this sense, an object moving at relativistic speeds would view distant astronomical objects differently as light emissions from these objects would be distorted. Whereas objects in front of the spacecraft would have the wavelength of their light shortened, objects behind it would have them lengthened.
This phenomenon, known as the “Doppler Effect”, results in light being shifted towards the blue end (“blueshift”) or the red end (“redshift”) of the spectrum for approaching and retreating objects, respectively. In 1929, astronomer Edwin Hubble used redshift measurements to determine that distant galaxies were moving away from our own, thus demonstrating that the Universe was in a state of expansion.
Because of this expansion (known as the Hubble Expansion), much of the light in the Universe is redshifted and only measurable in difficult-to-observe infrared wavelengths. But for a camera moving at relativistic speeds, according to Prof. Zhang, this redshifted light would become bluer since the motion of the camera would counteract the effects of cosmic expansion.
This effect, known as “Doppler boosting”, would cause the faint light from the early Universe to be amplified and allow distant objects to be studied in more detail. In this respect, astronomers would be able to study some of the earliest objects in the known Universe, which would offer more clues as to how it evolved over time. As Prof. Zhang explained to Universe Today via email, this would allow for some unique opportunities to test Special Relativity:
“In the rest frame of the camera, the emission of the objects in the hemisphere of the camera motion is blue-shifted. For bright objects with detailed spectral observations from the ground, one can observe them in flight. By comparing their blue-shifted flux at a specific blue-shifted frequency with the flux of the corresponding (de-blueshifted) frequency on the ground, one can precisely test the Doppler boosting prediction in Special Relativity.”
In addition, the frequency and intensity of light – and also the size of distant objects – would also change as far as the observer was concerned. In this respect, the camera would act as a lens and a wide-field camera, magnifying the amount of light it collects and letting astronomers observe more objects within the same field of view. By comparing the observations collected by the camera to those collected by a camera from the ground, astronomers could also test the probe’s Lorentz Factor.
This factor indicates how time, length, and relativistic mass change for an object while that object is moving, which is another prediction of Special Relativity. Last, but not least, Prof. Zhang indicates that probes traveling at relativistic speeds would not need to be sent to any specific destination in order to conduct these tests. As he explained:
“The concept of “relativistic astronomy” is that one does not really need to send the cameras to specific star systems. No need to aim (e.g. to Alpha Centauri system), no need to decelerate. As long as the signal can be transferred back to earth, one can learn a lot of things. Interesting targets include high-redshift galaxies, active galactic nuclei, gamma-ray bursts, and even electromagnetic counterparts of gravitational waves.”
However, there are some drawbacks to this proposal. For starters, the technology behind Starshot is all about accomplishing the dream of countless generations – i.e. reaching another star system (in this case, Alpha Centauri) – within a single generation.
And as Professor Abraham Loeb – the Frank B. Baird Jr. Professor of Science at Harvard University and the Chair and the Breakthrough Starshot Committee – told Universe Today via email, what Prof. Zhang is proposing can be accomplished by other means:
>“Indeed, there are benefits to having a camera move near the speed of light toward faint sources, such as the most distant dwarf galaxies in the early universe. But the cost of launching a camera to the required speed would be far greater than building the next generation of large telescopes which will provide us with a similar sensitivity. Similarly, the goal of testing special relativity can be accomplished at a much lower cost.”
Of course, it will be many years before a project like Starshot can be mounted, and many challenges need to be addressed in the meantime. But it is exciting to know that in meantime, scientific applications can be found for such a mission that go beyond exploration. In a few decades, when the mission begins to make the journey to Alpha Centauri, perhaps it will also be able to conduct tests on Special Relativity and other physical laws while in transit.
Since ancient times, philosophers and scholars have sought to understand light. In addition to trying to discern its basic properties (i.e. what is it made of – particle or wave, etc.) they have also sought to make finite measurements of how fast it travels. Since the late-17th century, scientists have been doing just that, and with increasing accuracy.
In so doing, they have gained a better understanding of light’s mechanics and the important role it plays in physics, astronomy and cosmology. Put simply, light moves at incredible speeds and is the fastest moving thing in the Universe. Its speed is considered a constant and an unbreakable barrier, and is used as a means of measuring distance. But just how fast does it travel?
Speed of Light (c):
Light travels at a constant speed of 1,079,252,848.8 (1.07 billion) km per hour. That works out to 299,792,458 m/s, or about 670,616,629 mph (miles per hour). To put that in perspective, if you could travel at the speed of light, you would be able to circumnavigate the globe approximately seven and a half times in one second. Meanwhile, a person flying at an average speed of about 800 km/h (500 mph), would take over 50 hours to circle the planet just once.
To put that into an astronomical perspective, the average distance from the Earth to the Moon is 384,398.25 km (238,854 miles ). So light crosses that distance in about a second. Meanwhile, the average distance from the Sun to the Earth is ~149,597,886 km (92,955,817 miles), which means that light only takes about 8 minutes to make that journey.
Little wonder then why the speed of light is the metric used to determine astronomical distances. When we say a star like Proxima Centauri is 4.25 light years away, we are saying that it would take – traveling at a constant speed of 1.07 billion km per hour (670,616,629 mph) – about 4 years and 3 months to get there. But just how did we arrive at this highly specific measurement for “light-speed”?
History of Study:
Until the 17th century, scholars were unsure whether light traveled at a finite speed or instantaneously. From the days of the ancient Greeks to medieval Islamic scholars and scientists of the early modern period, the debate went back and forth. It was not until the work of Danish astronomer Øle Rømer (1644-1710) that the first quantitative measurement was made.
In 1676, Rømer observed that the periods of Jupiter’s innermost moon Io appeared to be shorter when the Earth was approaching Jupiter than when it was receding from it. From this, he concluded that light travels at a finite speed, and estimated that it takes about 22 minutes to cross the diameter of Earth’s orbit.
Christiaan Huygens used this estimate and combined it with an estimate of the diameter of the Earth’s orbit to obtain an estimate of 220,000 km/s. Isaac Newton also spoke about Rømer’s calculations in his seminal work Opticks (1706). Adjusting for the distance between the Earth and the Sun, he calculated that it would take light seven or eight minutes to travel from one to the other. In both cases, they were off by a relatively small margin.
Later measurements made by French physicists Hippolyte Fizeau (1819 – 1896) and Léon Foucault (1819 – 1868) refined these measurements further – resulting in a value of 315,000 km/s (192,625 mi/s). And by the latter half of the 19th century, scientists became aware of the connection between light and electromagnetism.
This was accomplished by physicists measuring electromagnetic and electrostatic charges, who then found that the numerical value was very close to the speed of light (as measured by Fizeau). Based on his own work, which showed that electromagnetic waves propagate in empty space, German physicist Wilhelm Eduard Weber proposed that light was an electromagnetic wave.
The next great breakthrough came during the early 20th century/ In his 1905 paper, titled “On the Electrodynamics of Moving Bodies”, Albert Einstein asserted that the speed of light in a vacuum, measured by a non-accelerating observer, is the same in all inertial reference frames and independent of the motion of the source or observer.
Using this and Galileo’s principle of relativity as a basis, Einstein derived the Theory of Special Relativity, in which the speed of light in vacuum (c) was a fundamental constant. Prior to this, the working consensus among scientists held that space was filled with a “luminiferous aether” that was responsible for its propagation – i.e. that light traveling through a moving medium would be dragged along by the medium.
This in turn meant that the measured speed of the light would be a simple sum of its speed through the medium plus the speed of that medium. However, Einstein’s theory effectively made the concept of the stationary aether useless and revolutionized the concepts of space and time.
Not only did it advance the idea that the speed of light is the same in all inertial reference frames, it also introduced the idea that major changes occur when things move close the speed of light. These include the time-space frame of a moving body appearing to slow down and contract in the direction of motion when measured in the frame of the observer (i.e. time dilation, where time slows as the speed of light approaches).
His observations also reconciled Maxwell’s equations for electricity and magnetism with the laws of mechanics, simplified the mathematical calculations by doing away with extraneous explanations used by other scientists, and accorded with the directly observed speed of light.
During the second half of the 20th century, increasingly accurate measurements using laser inferometers and cavity resonance techniques would further refine estimates of the speed of light. By 1972, a group at the US National Bureau of Standards in Boulder, Colorado, used the laser inferometer technique to get the currently-recognized value of 299,792,458 m/s.
Role in Modern Astrophysics:
Einstein’s theory that the speed of light in vacuum is independent of the motion of the source and the inertial reference frame of the observer has since been consistently confirmed by many experiments. It also sets an upper limit on the speeds at which all massless particles and waves (which includes light) can travel in a vacuum.
One of the outgrowths of this is that cosmologists now treat space and time as a single, unified structure known as spacetime – in which the speed of light can be used to define values for both (i.e. “lightyears”, “light minutes”, and “light seconds”). The measurement of the speed of light has also become a major factor when determining the rate of cosmic expansion.
Beginning in the 1920’s with observations of Lemaitre and Hubble, scientists and astronomers became aware that the Universe is expanding from a point of origin. Hubble also observed that the farther away a galaxy is, the faster it appears to be moving. In what is now referred to as the Hubble Parameter, the speed at which the Universe is expanding is calculated to 68 km/s per megaparsec.
This phenomena, which has been theorized to mean that some galaxies could actually be moving faster than the speed of light, may place a limit on what is observable in our Universe. Essentially, galaxies traveling faster than the speed of light would cross a “cosmological event horizon”, where they are no longer visible to us.
Also, by the 1990’s, redshift measurements of distant galaxies showed that the expansion of the Universe has been accelerating for the past few billion years. This has led to theories like “Dark Energy“, where an unseen force is driving the expansion of space itself instead of objects moving through it (thus not placing constraints on the speed of light or violating relativity).
Along with special and general relativity, the modern value of the speed of light in a vacuum has gone on to inform cosmology, quantum physics, and the Standard Model of particle physics. It remains a constant when talking about the upper limit at which massless particles can travel, and remains an unachievable barrier for particles that have mass.
Perhaps, someday, we will find a way to exceed the speed of light. While we have no practical ideas for how this might happen, the smart money seems to be on technologies that will allow us to circumvent the laws of spacetime, either by creating warp bubbles (aka. the Alcubierre Warp Drive), or tunneling through it (aka. wormholes).
Until that time, we will just have to be satisfied with the Universe we can see, and to stick to exploring the part of it that is reachable using conventional methods.
At the end of the millennium, Physics World magazine conducted a poll where they asked 100 of the world’s leading physicists who they considered to be the top 10 greatest scientist of all time. The number one scientist they identified was Albert Einstein, with Sir Isaac Newton coming in second. Beyond being the most famous scientist who ever lived, Albert Einstein is also a household name, synonymous with genius and endless creativity.
As the discoverer of Special and General Relativity, Einstein revolutionized our understanding of time, space, and universe. This discovery, along with the development of quantum mechanics, effectively brought to an end the era of Newtonian Physics and gave rise to the modern age. Whereas the previous two centuries had been characterized by universal gravitation and fixed frames of reference, Einstein helped usher in an age of uncertainty, black holes and “scary action at a distance”.
We’ve come a long way in 13.8 billion years; but despite our impressively extensive understanding of the Universe, there are still a few strings left untied. For one, there is the oft-cited disconnect between general relativity, the physics of the very large, and quantum mechanics, the physics of the very small. Then there is problematic fate of a particle’s intrinsic information after it falls into a black hole. Now, a new interpretation of fundamental physics attempts to solve both of these conundrums by making a daring claim: at certain scales, space and time simply do not exist.
Let’s start with something that is not in question. Thanks to Einstein’s theory of special relativity, we can all agree that the speed of light is constant for all observers. We can also agree that, if you’re not a photon, approaching light speed comes with some pretty funky rules – namely, anyone watching you will see your length compress and your watch slow down.
But the slowing of time also occurs near gravitationally potent objects, which are described by general relativity. So if you happen to be sight-seeing in the center of the Milky Way and you make the regrettable decision to get too close to our supermassive black hole’s event horizon (more sinisterly known as its point-of-no-return), anyone observing you will also see your watch slow down. In fact, he or she will witness your motion toward the event horizon slow dramatically over an infinite amount of time; that is, from your now-traumatized friend’s perspective, you never actually cross the event horizon. You, however, will feel no difference in the progression of time as you fall past this invisible barrier, soon to be spaghettified by the black hole’s immense gravity.
So, who is “correct”? Relativity dictates that each observer’s point of view is equally valid; but in this situation, you can’t both be right. Do you face your demise in the heart of a black hole, or don’t you? (Note: This isn’t strictly a paradox, but intuitively, it feels a little sticky.)
And there is an additional, bigger problem. A black hole’s event horizon is thought to give rise to Hawking radiation, a kind of escaping energy that will eventually lead to both the evaporation of the black hole and the destruction of all of the matter and energy that was once held inside of it. This concept has black hole physicists scratching their heads. Because according to the laws of physics, all of the intrinsic information about a particle or system (namely, the quantum wavefunction) must be conserved. It cannot just disappear.
Why all of these bizarre paradoxes? Because black holes exist in the nebulous space where a singularity meets general relativity – fertile, yet untapped ground for the elusive theory of everything.
Enter two interesting, yet controversial concepts: doubly special relativity and gravity’s rainbow.
Just as the speed of light is a universally agreed-upon constant in special relativity, so is the Planck energy in doubly special relativity (DSR). In DSR, this value (1.22 x 1019 GeV) is the maximum energy (and thus, the maximum mass) that a particle can have in our Universe.
Two important consequences of DSR’s maximum energy value are minimum units of time and space. That is, regardless of whether you are moving or stationary, in empty space or near a black hole, you will agree that classical space breaks down at distances shorter than the Planck length (1.6 x 10-35 m) and classical time breaks down at moments briefer than the Planck time (5.4 x 10-44 sec).
In other words, spacetime is discrete. It exists in indivisible (albeit vanishingly small) units. Quantum below, classical above. Add general relativity into the picture, and you get the theory of gravity’s rainbow.
Physicists Ahmed Farag Ali, Mir Faizal, and Barun Majumder believe that these theories can be used to explain away the aforementioned black hole conundrums – both your controversial spaghettification and the information paradox. How? According to DSR and gravity’s rainbow, in regions smaller than 1.6 x 10-35 m and at times shorter than 5.4 x 10-44 sec… the Universe as we know it simply does not exist.
“In gravity’s rainbow, space does not exist below a certain minimum length, and time does not exist below a certain minimum time interval,” explained Ali, who, along with Faizal and Majumder, authored a paper on this topic that was published last month. “So, all objects existing in space and occurring at a time do not exist below that length and time interval [which are associated with the Planck scale].”
Luckily for us, every particle we know of, and thus every particle we are made of, is much larger than the Planck length and endures for much longer than the Planck time. So – phew! – you and I and everything we see and know can go on existing. (Just don’t probe too deeply.)
The event horizon of a black hole, however, is a different story. After all, the event horizon isn’t made of particles. It is pure spacetime. And according to Ali and his colleagues, if you could observe it on extremely short time or distance scales, it would cease to have meaning. It wouldn’t be a point-of-no-return at all. In their view, the paradox only arises when you treat spacetime as continuous – without minimum units of length and time.
“As the information paradox depends on the existence of the event horizon, and an event horizon like all objects does not exist below a certain length and time interval, then there is no absolute information paradox in gravity’s rainbow. The absence of an effective horizon means that there is nothing absolutely stopping information from going out of the black hole,” concluded Ali.
No absolute event horizon, no information paradox.
And what of your spaghettification within the black hole? Again, it depends on the scale at which you choose to analyze your situation. In gravity’s rainbow, spacetime is discrete; therefore, the mathematics reveal that both you (the doomed in-faller) and your observer will witness your demise within a finite length of time. But in the current formulation of general relativity, where spacetime is described as continuous, the paradox arises. The in-faller, well, falls in; meanwhile, the observer never sees the in-faller pass the event horizon.
“The most important lesson from this paper is that space and time exist only beyond a certain scale,” said Ali. “There is no space and time below that scale. Hence, it is meaningless to define particles, matter, or any object, including black holes, that exist in space and time below that scale. Thus, as long as we keep ourselves confined to the scales at which both space and time exist, we get sensible physical answers. However, when we try to ask questions at length and time intervals that are below the scales at which space and time exist, we end up getting paradoxes and problems.”
To recap: if spacetime continues on arbitrarily small scales, the paradoxes remain. If, however, gravity’s rainbow is correct and the Planck length and the Planck time are the smallest unit of space and time that fundamentally exist, we’re in the clear… at least, mathematically speaking. Unfortunately, the Planck scales are far too tiny for our measly modern particle colliders to probe. So, at least for now, this work provides yet another purely theoretical result.
The paper was published in the January 23 issue of Europhysics Letters. A pre-print of the paper is available here.
It’s a cornerstone of modern physics that nothing in the Universe is faster than the speed of light (c). However, Einstein’s theory of special relativity does allow for instances where certain influences appear to travel faster than light without violating causality. These are what is known as “photonic booms,” a concept similar to a sonic boom, where spots of light are made to move faster than c.
And according to a new study by Robert Nemiroff, a physics professor at Michigan Technological University (and co-creator of Astronomy Picture of the Day), this phenomena may help shine a light (no pun!) on the cosmos, helping us to map it with greater efficiency.
Consider the following scenario: if a laser is swept across a distant object – in this case, the Moon – the spot of laser light will move across the object at a speed greater than c. Basically, the collection of photons are accelerated past the speed of light as the spot traverses both the surface and depth of the object.
The resulting “photonic boom” occurs in the form of a flash, which is seen by the observer when the speed of the light drops from superluminal to below the speed of light. It is made possible by the fact that the spots contain no mass, thereby not violating the fundamental laws of Special Relativity.
Another example occurs regularly in nature, where beams of light from a pulsar sweep across clouds of space-borne dust, creating a spherical shell of light and radiation that expands faster than c when it intersects a surface. Much the same is true of fast-moving shadows, where the speed can be much faster and not restricted to the speed of light if the surface is angular.
At a meeting of the American Astronomical Society in Seattle, Washington earlier this month, Nemiroff shared how these effects could be used to study the universe.
“Photonic booms happen around us quite frequently,” said Nemiroff in a press release, “but they are always too brief to notice. Out in the cosmos they last long enough to notice — but nobody has thought to look for them!”
Superluminal sweeps, he claims, could be used to reveal information on the 3-dimensional geometry and distance of stellar bodies like nearby planets, passing asteroids, and distant objects illuminated by pulsars. The key is finding ways to generate them or observe them accurately.
For the purposes of his study, Nemiroff considered two example scenarios. The first involved a beam being swept across a scattering spherical object – i.e. spots of light moving across the Moon and pulsar companions. In the second, the beam is swept across a “scattering planar wall or linear filament” – in this case, Hubble’s Variable Nebula.
In the former case, asteroids could be mapped out in detail using a laser beam and a telescope equipped with a high-speed camera. The laser could be swept across the surface thousands of times a second and the flashes recorded. In the latter, shadows are observed passing between the bright star R Monocerotis and reflecting dust, at speeds so great that they create photonic booms that are visible for days or weeks.
This sort of imaging technique is fundamentally different from direct observations (which relies on lens photography), radar, and conventional lidar. It is also distinct from Cherenkov radiation – electromagnetic radiation emitted when charged particles pass through a medium at a speed greater than the speed of light in that medium. A case in point is the blue glow emitted by an underwater nuclear reactor.
Combined with the other approaches, it could allow scientists to gain a more complete picture of objects in our Solar System, and even distant cosmological bodies.
Nemiroff’s study accepted for publication by the Publications of the Astronomical Society of Australia, with a preliminary version available online at arXiv Astrophysics
It sounds like science fiction, but the time you experience between two events depends directly on the path you take through the universe. In other words, Einstein’s theory of special relativity postulates that a person traveling in a high-speed rocket would age more slowly than people back on Earth.
Although few physicists doubt Einstein was right, it’s crucial to verify time dilation to the best possible accuracy. Now, an international team of researchers, including Nobel laureate Theodor Hänsch, director of the Max Planck optics institute, has done just this.
Tests of special relativity date back to 1938. But once we started going to space regularly, we had to learn to deal with time dilation on a daily basis. GPS satellites, for example, are basically clocks in orbit. They travel at a whopping speed of 14,000 kilometers per hour well above the Earth’s surface at a distance of 20,000 kilometers. So relative to an atomic clock on the ground they lose about 7 microseconds per day, a number that has to be taken into account for them to work properly.
To test time dilation to a much higher precision, Benjamin Botermann of Johannes Gutenberg-University, Germany, and colleagues accelerated lithium ions to one-third the speed of light. Here the Doppler shift quickly comes into play. Any ions flying toward the observer will be blue shifted and any ions flying away from the observer will be red shifted.
The level at which the ions undergo a Doppler shift depends on their relative motion, with respect to the observer. But this also makes their clock run slow, which redshifts the light from the observer’s point of view — an effect that you should be able to measure in the lab.
So the team stimulated transitions in the ions using two lasers propagating in opposite directions. Then any shifts in the absorption frequency of the ions are dependent on the Doppler effect, which we can easily calculate, and the redshift due to time dilation.
The team verified their time dilation prediction to a few parts per billion, improving on previous limits. The findings were published on Sept. 16 in the journal Physical Review Letters.
Time Reborn: From the Crisis of Physics to the Future of the Universe is one of those books intended to provoke discussion. Right from the first pages, author Lee Smolin — a Canadian theoretical physicist who also teaches philosophy — puts forward a position: time is real, and not an illusion of the human experience (as other physicists try to argue).
Smolin, in fact, uses that concept of time as a basis for human free will. If time is real, he writes, this is the result: “Novelty is real. We can create, with our imagination, outcomes not computable from knowledge of the present.”
Physics as philosophy. A powerful statement to make in the opening parts of the book. The only challenge is understanding the rest of it.
Smolin advertises his book as open to the general reader who has no background in physics or mathematics, promising that there aren’t even equations to worry about. He also breaks up the involved explanations with wry observations of fatherhood, or by bringing up anecdotes from his past.
It works, but you need to be patient. Theoretical physics is so far outside of the everyday that at times it took me (with education focusing on journalism and space policy, admittedly) two or three readings of the same passage to understand what was going on.
But as I took my time, a whole world opened up to me.
I found myself understanding more about Einstein’s special and general relativity than I did in readings during high school and university. The book also made me think differently about cosmology (the nature of the universe), especially in relation to biological laws.
While the book is enjoyable, it is probably best not to read it in isolation as it is a positional one — a book that gathers information scientifically and analytically, to be sure, but one that does not have a neutral point of view to the conclusions.
We’d recommend picking up other books such as the classic A Brief History of Time (by physicist Stephen Hawking) to learn more about the universe, and how other scientists see time work. | 0.898489 | 3.616244 |
The discovery of planets from outside the solar system is a new and fast-growing field of research. As of July 2001 there are 67 planets recorded from outside our own solar system. The first such planet was reported in the scientific journal Nature as recently as 1995 by Michel Mayer and Didier Queloz from the University of Geneva. This first discovery was around star 51 Pegasi. Shortly afterwards, in 1996, Geoffrey Marcy and Paul Butler from the USA reported a planet around the star Upsilon Andromedae — a discovery which subsequently revealed an entire planetary system associated with this star.
Compared to the intense brightness of a star, planets are invisible and cannot therefore be directly observed. It has long been known, however, that the presence of planets can be inferred by the gravitational pull they exert on their parent star. This should produce a tell-tale wobble in the motion of the star, which can be used to reveal the presence of an unseen planet.
Success in detecting wobble in the motion of a start has come from the analysis of the light emitted by the star. This allows us to measure the speed of the star. Spectroscopy — the analysis of starlight — splits up the light from a star into a spectrum and a measure of the shift of the absorption lines (the Doppler Shift) is used to calculate how fast the start is moving. [Visit http://exoplanets.org — go to 'Public Information', then 'The Doppler Detection Method'.] Stars which show a changing velocity are candidates for stars with planetary systems. If the change in velocity has a regular periodicity which is shown to be in accord with Kepler's Laws of planetary motion, then a planet may be inferred. By 1995 astronomers had improved the sensitivity of their spectroscopic methods such that the precision of velocity measurements had been increased from about 1 km/sec down to 20 m/sec. This paved the way for the first observations of a planet around star 51 Pegasi.
A second technique for detecting extrasolar planets is the observation of changes in star brightness. If a planet passes over the surface of the star, in certain conditions, the brightness of the star will be reduced. In the autumn of 1999 a 2% dimming of the star HD 209458 was observed at exactly the time predicted from calculations made of the orbit of an inferred planet. These observations provided important confirmatory evidence of results obtained using the Doppler method. [Visit http://exoplanets.org — go to 'Public Information', then 'Various Planetary Detection Methods'.]
Most of the recorded extra-solar planets to date have a mass close to that of Jupiter. Such planets are large gaseous planets, with a mass of about 1% of the sun. In March 2000 planets with a smaller mass were first detected and two planets with the mass of Saturn were found orbiting the stars HD 46375 and HD 16141.
Close analysis of the data from the star Upsilon Andromedae, 44 AU (astronomical units, i.e. earth-sun distances) away showed that there were three planets present. The innermost is ¾ the mass of Jupiter, 0.06 AU from the star and orbits the star in just 4.6 days; the middle planet is twice the mass of Jupiter, orbits at 0.3 AU from the star and takes 242 days to orbit. The outer planet has a mass four times that of Jupiter, is a distance 2.5 AU from the star and takes 3.5-4 years to orbit the star. These observations are of particular interest to astronomers and initially were a great surprise for these observations are very different from the pattern of planets in our own solar system. It was not expected that planets orbiting other stars would be large and very close to their parent star.
Details of planets associated with the star Upsilon Andromeda are at http://www.jtwinc.com/extrasolar/mainframes.html, select 'Planets of normal stars', select 'Upsilon Andromedae'. | 0.909729 | 3.836945 |
Solar System Exploration
New analysis of data from NASA's Cassini spacecraft finds auroras at Saturn's poles may keep its atmosphere warm.
Data From NASA's Cassini May Explain Saturn's Atmospheric Mystery
Fun — and even educational — NASA activities to do at home.
10+ Things to Do with NASA at Home
Whether you're doing it for the nerd cred or the pie, this week on #10Things, we've got all the ways you can celebrate #PiDay with NASA.
10 Ways to Celebrate Pi Day with NASA on March 14
NASA is preparing to send the drone-like Dragonfly to the intriguing moon, Titan. Here are five reasons Saturn's largest moons is so enticing.
Why is NASA Sending Dragonfly to Titan? Here are Five Reasons
The Voyager imaging team asked for the photo to show Earth’s vulnerability — to illustrate how small, fragile and irreplaceable it is on a cosmic scale.
10 Things You Might Not Know About Voyager's Famous 'Pale Blue Dot' Photo
Spitzer, designed to reveal the far, cold and dusty side of the universe, made discoveries its designers never even imagined, including a previously unseen ring of Saturn.
10 Things Spitzer Taught Us About Our Solar System
The first map showing the global geology of Saturn's largest moon, Titan, has been completed and fully reveals a dynamic world of dunes, lakes, plains, craters and other terrains.
The First Global Geologic Map of Titan Completed
The next full Moon will be on Sunday afternoon, October 13, 2019, The Moon will appear full for about three days centered on this time, from Saturday morning to Tuesday morning.
October 2019: The Next Full Moon is the Hunter's Moon
Cassini scientists have found the ingredients for amino acids condensed onto ice grains emitted by Saturn's sixth-largest moon.
New Organic Compounds Found in Enceladus Ice Grains
Mini robots that can roll, fly, float and swim, then morph into a single machine? Together they form Shapeshifter, a developing concept for a transformational vehicle to explore treacherous, distant worlds.
NASA Designing Shapeshifting Robots for Saturn's Moons
Saturn is so beautiful that astronomers cannot resist using the Hubble Space Telescope to take yearly snapshots of the ringed world when it is at its closest distance to Earth.
Saturn's Rings Shine in Hubble's Latest Portrait
A new theory, based on radar data from NASA's Cassini mission, proposes that some of Titan's lakes formed when pockets of nitrogen blew out basins that filled with methane.
New Models Suggest Titan Lakes Are Explosion Craters
The next full Moon will be early Saturday morning, September 14, 2019. Find out what else to watch for in the skies during the next few weeks.
September 2019: The Next Full Moon is the Harvest Moon
After its launch in 2021, NASA’s James Webb Space Telescope will observe Saturn as part of a comprehensive solar system program.
NASA's Webb Telescope Will Survey Saturn and its Moon Titan
After nearly 16 years of exploring the cosmos in infrared light, NASA's Spitzer Space Telescope will be switched off permanently on Jan. 30, 2020.
How NASA's Spitzer Has Stayed Alive for So Long
Images collected during Cassini's superclose orbits in 2017 are giving scientists new insight into the complex workings of the rings.
NASA's Cassini Reveals New Sculpting in Saturn Rings
There’s way more to Saturn than its rings. The planet also boasts a collection of exotic, and still mysterious, moons.
10 Things: Unsolved Mysteries of Saturn's Moons
Our solar system is a stormy place. Join us on a tour of storms.
10+ Things: Tour of Storms Across the Solar System
Dust and ice from Saturn's vast rings accretes onto the moons embedded within and near the rings.
Cassini Finds Saturn's Rings Coat Tiny Moons
Meet the women leading two of humankind's two most distant space missions.
Women at the Helm
The next full Moon will be on Feb. 19, 2019.
February 2019: The Next Full Moon is the Crow Moon
New data from NASA's Cassini spacecraft may solved a longstanding mystery. The length of a day on Saturn: 10 hours, 33 minutes and 38 seconds.
Scientists Finally Know What Time It Is on Saturn
New measurements of the mass of Saturn's rings reveal their age — and something they have in common with dinosaurs.
NASA's Cassini Data Show Saturn's Rings Relatively New
New NASA research confirms that Saturn's rings are being pulled into Saturn by gravity as a dusty rain of ice particles under the influence of Saturn’s magnetic field.
NASA Research Reveals Saturn is Losing Its Rings at "Worst-Case-Scenario" Rate
November 16 marks the premiere of a unique film and musical experience inspired by the Hubble Space Telescope’s famous Deep Field image
Hubble's Visualizations of the Universe Form Heart of New "Deep Field" Film | 0.865495 | 3.135105 |
As the Chinese proverb says, “May you live in interesting times,” and while the promise of Comet ISON dazzling observers didn’t exactly pan out as hoped for in early 2014, we now have a bevy of binocular comets set to grace evening skies for northern hemisphere observers. Comet 2012 K1 PanSTARRS has put on a fine show, and comet C/2014 E2 Jacques has emerged from behind the Sun and its close 0.085 AU passage near Venus and has already proven to be a fine target for astro-imagers. And we’ve got another icy visitor to the inner solar system beating tracks northward in the form of Comet C/2013 V5 Oukaimeden, and a grand cometary finale as comet A1 Siding Spring brushes past the planet Mars. That is, IF a spectacular naked eye comet doesn’t come by and steal the show, as happens every decade or so…
Anyhow, here’s a rapid fire run down on what you can expect from three of these binocular comets that continue to grace the twilight skies this Fall.
(Note that mentions of comets “passing near” a given object denote conjunctions of less than an angular degree of arc unless otherwise stated).
C/2014 E2 Jacques:
Discovered by amateur astronomer Cristovao Jacques on March 13th of this year from the SONEAR Observatory in Brazil, Comet E2 Jacques has been dazzling observers as it passed 35 degrees from the north celestial pole and posed near several deep sky wonders as it transited the constellation of Cassiopeia.
Mid-September finds Jacques 55 degrees above the NE horizon at dusk for northern hemisphere viewers in the constellation Cygnus. It then races southward parallel to the galactic equator, keeping in the +7th to +8th magnitude range before dropping down below +10th magnitude in late October. After this current passage through the inner solar system, Comet Jacques will be on a shortened 12,000 year orbit.
-Brightest: Mid-August at +6th magnitude.
-Perihelion: July 2nd, 2014 (0.66 AU).
-Closest to Earth: August 28, 2014 (0.56 AU).
Some key upcoming dates:
Sep 10: Passes the +3.9 magnitude star Eta Cygni.
Sep 14: Passes near the famous optical double star Albireo and crosses into the constellation of Vulpecula.
Sep 16: Passes in front of the +4.4 magnitude star Alpha Vulpeculae.
Sep 20: Crosses the Coathanger asterism.
Sep 21: Crosses into the constellation Sagitta.
Sep 24: Crosses into Aquila.
Oct 5: Crosses the galactic plane.
Oct 14: passes near the +7.5 magnitude open cluster NGC 6755.
Oct 15: Drops back below +10th magnitude?
C/2013 V5 Oukaïmeden
Pronounced Ow-KAY-E-Me-dah, (yes, it’s a French name, with a very metal umlaut over the “ï”!) comet C/2013 V5 Oukaïmeden was discovered by the Moroccan Oukaïmeden Sky Survey (MOSS) located in the Atlas Mountains in Morocco. After completing a brief dawn appearance in early September, the comet moves into the dusk sky and starts the month of October located 38 degrees east of the Sun at about 14 degrees above the southwestern horizon as seen from latitude 30 degrees north at sunset. Southern hemisphere observers will continue to have splendid dawn views of the comet through mid-September at its expected peak. Comet Oukaïmeden is currently at +8th magnitude “with a bullet” and is expected to top out +6th magnitude in late September shortly before perihelion and perhaps remain a binocular object as it crosses the constellation Libra in October.
And its also worth noting that as comet A1 Siding Spring (see below) makes a close physical pass by Mars on October 19th, Comet Oukaïmeden makes a close apparent pass by Saturn as seen from our Earthly vantage point the evening before! To be sure, the dusk apparition of Comet Oukaïmeden will be a tough one, but if you can track down these bright guidepost objects listed below, you’ll have a chance at spying it.
-Perihelion: September 28th, 2014 (0.63 AU from the Sun).
-Closest to Earth: September 16th, 2014 (0.48 AU).
Some key upcoming dates:
Sep 10 through Oct 4: Threads across the borders of the constellations Hydra, Pyxis, Antlia and Centaurus.
Sep 18: Passes near the +3.5 magnitude star Xi Hydrae.
Sep 19: Passes near the +4.3 magnitude star Beta Hydrae.
Sep 25: Passes 1.5 degrees from the +8th magnitude Southern Pinwheel Galaxy M83.
Oct 1: Passes in front of the +10.2 globular cluster NGC 5694.
Oct 3: Passes into Libra.
Oct 11: Passes near the +8.5 magnitude globular cluster NGC 5897.
Oct 16: Crosses the ecliptic plane northward.
Oct 18: Passes less than two degrees from Saturn.
Oct 25: Passes less than a degree from the 2 day old Moon and the +3.9 magnitude star Gamma Librae.
C/2013 A1 Siding Spring
This comet was discovered on January 3rd, 2013 from the Siding Spring observatory in Australia, and soon caught the eye of astronomers when it was discovered that it would make a nominal pass just 139,000 kilometres from Mars on October 19th.
As seen from the Earth, Comet A1 Siding Spring has just broken 10th magnitude and vaults up towards the planet Mars low to the southwest at dusk this Fall for northern hemisphere observers. A1 Siding Spring is expected to top out at +8th magnitude this month before its Mars encounter, and is on a one million year plus orbit.
-Brightest: Early to Mid-September.
-Perihelion: October 25th, 2014.
-Closest to Earth: October 28th, 2014 (1.4 AU).
Some key upcoming dates:
Sep 17: Passes into the constellation Telescopium.
Sep 20: Passes near the +8.5 magnitude globular NGC 6524.
Sep 21: Passes into the constellation Ara.
Sep 22: Passes the +3.6 magnitude star Beta Arae.
Sep 25: Crosses into Scorpius.
Sep 30: Passes the +3 magnitude star Iota Scorpii.
Oct 3: Passes near the +7.2 magnitude globular NGC 6441.
Oct 5: Passes 2 degrees from Ptolemy’s cluster M7.
Oct 8: Passes in front of the Butterfly cluster M6.
Oct 10: Crosses the galactic plane.
Oct 11: Crosses into Ophiuchus.
Oct 19: Passes just 2’ arc minutes from Mars as seen from Earth.
Oct 22: Passes north of the ecliptic.
Oct 30: Drops back below +10th magnitude?
Key moonless windows for evening comet viewing as reckoned from when the Moon wanes from Full to New are: September 9th to September 24th and October 8th to the 23rd.
Looking for resources to find out just what these comets and others are up to? The COBS Comet Observers database is a great resource for recent observations, as is Seiichi Yoshida’s Weekly Comet page. For history and current info, Gary Kronk’s Cometography is also a great treasure trove to delve into, as are the Yahoo! Comet and Comet Observer mailing lists.
Be sure to check out these fine icy visitors to the inner solar system coming to a sky near you. We fully expect to see more outstanding images of these comets and more filling up the Universe Today Flickr forum! | 0.87449 | 3.50607 |
Researchers Catch Supermassive Black Hole Burping — Twice
Using data from several telescopes including NASA's Chandra X-ray Observatory, astronomers have caught a supermassive black hole snacking on gas and then "burping" — not once but twice, as described in our latest press release.
This graphic shows the galaxy, called SDSS J1354+1327 (J1354 for short) in a composite image with data from Chandra (purple), and the Hubble Space Telescope (HST; red, green and blue). The inset box contains a close-up view of the central region around J1354's supermassive black hole. A companion galaxy to J1354 is shown to the north. Researchers also used data from the W.M. Keck Observatory atop Mauna Kea, Hawaii and the Apache Point Observatory (APO) in New Mexico for this finding.
Chandra detected a bright, point-like source of X-ray emission from J1354, a telltale sign of the presence of a supermassive black hole millions or billions of times more massive than our sun. The X-rays are produced by gas heated to millions of degrees by the enormous gravitational and magnetic forces near the black hole. Some of this gas will fall into the black hole, while a portion will be expelled in a powerful outflow of high-energy particles.
By comparing images from Chandra and HST, the team determined that the black hole is located in the center of the galaxy, the expected location for such an object. The X-ray data also provide evidence that the supermassive black hole is embedded in a heavy veil of dust and gas.
The two-course meal for the black hole comes from a companion galaxy that collided with J1354 in the past. This collision produced a stream of stars and gas that links J1354 and the other galaxy. The separate outbursts from the black hole are caused by different clumps from this stream being consumed by the supermassive black hole. The researchers determined these two "burps" happened about 100,000 years apart.
The team used optical data from HST, Keck and APO to show that electrons had been stripped from atoms in a cone of gas (the green emission in the lower left of the inset) extending some 30,000 light years south from the galaxy's center. This stripping was likely caused by a burst of radiation from the vicinity of the black hole, indicating that the first of the two feasting events had occurred. Evidence for the second, more recent feast comes from the small source of green emission located at the northern tip of the Chandra source in the inset.
Julie Comerford from the University of Colorado at Boulder presented the team's findings in a January 11th, 2018 press briefing at the 231st meeting of the American Astronomical Society held in Washington D.C. A paper on the subject was published in a recent issue of The Astrophysical Journal and is available online. Co-authors on the new study include postdoctoral fellows Rebecca Nevin, Scott Barrows and Francisco Muller-Sanchez of CU Boulder, Jenny Greene of Princeton University, David Pooley from Trinity University, Daniel Stern from the Jet Propulsion Laboratory in Pasadena, California, and Fiona Harrison from the California Institute of Technology.
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Read the privacy statement | 0.833516 | 3.88517 |
When an electron revolves around a nucleus, It uses its energy in form of kinetic energy and so it release energy and then moves . It means that it release energy continuously, Otherwise, if it does not release energy(in form of Kinetic energy) continuously. Then its motion around nucleus is not possible.Please make me understand this concept?
Do you expect the moon to fall on the earth soon, from loosing its kinetic energy? If there is no interaction (as with tides for example) kinetic energy is conserved and the moon will still be turning around the earth, even though it is moving away due to the tidal interαction, when the sun becomes a giant dwarf. This is because the moon is captured around the earth by the gravitational force, a very weak force in comparison to the electromagnεtic one, but effective for large masses.
The planetary model for the electron around the nucleus fails because of the nature of the electromagnetic interaction: an accelerating charge radiates away energy , as the Maxwell equations show. The electron in orbit has angular acceleration and it will radiate electromagnetic waves, classically , and fall in the nucleus. So the planetary model fails since atoms exist and are stable .
The Bohr model postulated stable orbits in the planetary model, i.e. radiation forbidden for orbits with transitions fitting the data for the hydrogen atom. It has been superseded by quantum mechanics and the solutions of the Schrodinger equation for the Hydrogen atom. | 0.875594 | 3.159724 |
So you want to estimate surface gravity on a fictional planet? Easy!
One of the things I had to do as part of the rework of my novel The Tau Ceti Diversion, is to try and work out the surface gravity of my fictional planets. From the Kepler data, there are two exoplanets located in the Tau Ceti system that are likely to be in the system’s habitable zone, or where there is the possibility of liquid water on the surface, and perhaps life as we know it.
To play around with my estimates of gravity, I used ratioed rearrangements of Newton’s law of gravity (law of universal gravitation) and a simple formula relating the density of a spherical planet to its mass and radius (these are at the bottom of the post in the ADDENDUM).
WARNING: MATHS CONTENT!!!
Here’s Newtons famous law:)
The two planets thought to be in Tau Ceti’s habitable zone are denoted Tau Ceti e and Tau Ceti f. What is known about these two planets is their likely orbit, eccentricity, and their mass. All of these properties have been derived by calculation, based on observed data, so are all known to within appropriate error bounds, but I’m leaving the error off my scribblings so things don’t get too messy.
Tau Ceti e is thought to be around 4.3 Earth Masses, or Me (i.e. 4.3 times as heavy as Earth), while Tau Ceti f, the planet that orbits a bit further out, is thought to be around 6.67 Me. For the astronomically minded, these two planets orbit at around 0.55 and 1.35 AU from Tau Ceti respectively.
So, here’s where I cheated a bit, like any good engineer. I started with the answer I wanted and calculated backwards to see if the answer I wanted led to reasonable base assumptions. This is not as cheeky as it sounds, because when you have an insoluble problem (i.e. not enough data is known for an explicit result), an iterative approach is often used.
For my story to work, I needed a surface gravity on my planet of no more than 1.2g – that’s twenty percent higher than Earth’s. But how could I get a gravity that low on a planet that was over 4 times the mass of Earth? The answer is that surface gravity is a function of mass and radius, or going a step further along the calculation path, mass and density.
I used a ratioed form of Newton’s law that allowed me to relate the ratio of two planets gravitational forces to the ratios of their masses and radii. I already knew the ratio of the gravities ( assumed at gTCe/gE= 1.2) and the ratio of the masses (MTCe/ME = 4.3), so could calculate the ratio of radii (rE/rTCe) at 1.89. Using another formula that related the ratio of the two planet’s densities to their ratioed mass and radii, I could then calculate their ratioed densities (dens TCe/ densE) at 0.63. So at the end of all that, to have a surface gravity of 1.2 g, Tau Ceti e would have to have a density of 63% of Earth’s. Is that reasonable?
The density of Earth is 5.514 g/cm3, not too much different from the density of a rocky planet like Mercury (5.427 g/cm3), but a lot higher than other solar system planets like Jupiter and Uranus (1.326 g/cm3 and 1.27 g/cm3 respectively), comprised of lighter materials. A surface gravity of 1.2g on Tau Ceti e would put its density at around 3.5 g/cm3, less dense than our own rocky planets, but certainly in a feasible range.
So what sort of densities would you expect for the Tau Ceti system? One clue is the metallicity of the system, which is a measure of the ratio of iron to hydrogen in the star’s makeup. In the case of Tau Ceti, this is estimated to be around one third of our own sun. This indicates the star is likely to be older than the Sun, made up of stellar remnants left over from less evolved stars that have not had time to form as much of the heavier elements in their internal fusion factories.
So Tau Ceti is made up of lighter elements. Based on this, it was reasonable to assume that the planets in the Tau Ceti system would also be made up of proportionally lighter elements, and quite possibly in the range I had estimated. Tau Ceti e and Tau Ceti f are also large planets – much larger than our own Earth – so having a density in between Earth and our own gas giants also made sense to me.
Using the same planetary density I had calculated for Tau Ceti e, for the larger Tau Ceti f, gave me a surface density of around 1.4g for the bigger planet – just a little too high for feasible human colonisation – and that fit nicely with my story as well.
It was a lot of fun playing with these calculations, and thankfully the known science fit with my story, at least with some comfortable wiggle room!
Check out what challenges that increased gravity provided for my intrepid explorers in my novel The Tau Ceti Diversion!
Read it now on Amazon!
For those interested in the maths. . .
Density formula: densp= Mp / (4/3*pi()*rp^3)
densp= Density of Planet (kg/m3)
Mp = mass of planet (kg)
rp = radius of planet (m)
In ratio form: densp1/densp2= Mp1/Mp2 *(rp2/rp1)^3
Ratio of Newtons law relating gravity, mass and radius of two planets:
gp1/gp2= Mp1/Mp2 *(rp2/rp1)^2 | 0.915882 | 3.484134 |
Hubble's new image of Comet ISON shows the comet streaking across space on its course toward the Sun. It's a beautiful picture, and it lets us know that a.) ISON doesn't appear to be shattering and b.) ISON's jet seems to have vanished. But how do we get that information from the picture you see below?
Comet expert (and blog guest contributer!) Dr. Jian-Yang Li created a mathematical computer model of Comet ISON's coma — the fuzzy, spherical cloud of material that forms around a comet's nucleus when it nears the Sun — using the latest Hubble data. By subtracting that model from the reality of the data, we can see where the two differentiate.
It's best explained with a metaphor. Imagine you have a hill. The hill has an overall shape, but it also has bumps that may be difficult to see.
Now imagine you could create a hill that is the same shape, but without the bumps. If you could use that model of the hill to subtract the overall shape of the hill, all that would be left behind are the bumps, which are then quite obvious. We then exaggerate the bumps — ... | 0.807111 | 3.322152 |
Indeed, I missed it ... but apparently I didn't miss much. Comet 252P/LINEAR, the brighter of two comets that passed us at the same time, never got brighter than magnitude 5.5 (barely naked eye, yet another of many binocular events). It was fading at magnitude 6 in late May and is now beyond human sight. The other comet, P/2016 BA14, was too small to be visible to the human eye, but still was the closest comet in 246 years.
The following articles from March 2016 elaborates further the event:
Green Comet Will Pass Near Earth—With a Twin -- A Rare Double Comet Is Buzzing By
"A rapidly brightening green comet is making a historically close encounter with Earth on Monday, March 21. And following right behind it like a tagalong sibling is a second, smaller comet. The green comet, named 252P/LINEAR, is passing within 3.2 million miles (5.2 million kilometers) of Earth—about 14 times farther than the moon. While this may not sound very close, it’s actually the fifth closest comet on record. And its trailing partner will come even closer, making it the third closest in recorded history ..."
"In late March, 2016, two small comets swept by Earth. One (P/2016 BA14) was the closest comet in 246 years, while the other (252P/LINEAR) was the 5th closest known comet in recorded history. The second comet moved into skies visible from the Northern Hemisphere in late March and early April, and many hoped it would become bright enough to be seen with the unaided eye. It has, but only barely. For the most part, it has remained an inconspicuous object in the predawn sky, visible to those who search with binoculars or telescopes ... This comet will remain in our sky through about June ..."
"Two comets are headed for a historic flyby of Earth this week, and you don't want to miss them. The bigger of the two bodies, known as 252P/LINEAR, is about 750 feet in size and surrounded by an emerald green cloud of gas. It is expected to make its closest approach to our planet on March 21 at 5:14 a.m. PDT. At that time, it will come within 3.3 million miles of Earth, or about 14 times farther from our planet than the moon on March 21. The next day, at 7:30 a.m. PDT, a second, smaller comet known as P/2016 BA14 will come even closer --flying within 2.2 million miles of our planet or 9.2 times farther from the Earth than the moon. That will make it the closest comet to fly past Earth since 1770, according to Sky & Telescope, and the second closest comet to zip past Earth in recorded history ...
It is extremely improbable that two totally independent comets would fly so close to Earth at almost the same time ... Although their orbits are not identical, they are close enough to suggest that they may be two pieces of the same comet that broke apart in the recent past."
Only two other comets are known to have come closer to Earth in recorded history. They are 55P/Tempel-Tuttle, believed to have passed at a distance of 2.1 million miles on October 26, 1366, and Lexell’s comet (D/1770 L1), which passed on July 1, 1770 and missed Earth by only 1.4 million miles.
But those were singular comet close passes. This was TWO!
OF COURSE, NOTHING HAPPENED. EARTH WAS NOT DESTROYED, NOR DID I EXPECT IT WOULD BE. THIS EVENT WAS SOMETHING THAT COULD DEFINITELY BE DISCUSSED LATER.
So, what makes this March event so important for us know about, especially after the fact?
First of all, what is important about this event is that it made history. There has never been two comets that passed earth this close at the same time.
Secondly, the question one must now pose is whether this was a foreshadowing of a major prophetic event to come soon or is it setting an historical base 7 precedent for such an event occurring in the spring of 2023?
What is the prophetic event in question?
The Warning: A worldwide warning is to be experienced by everyone on earth. Its purpose will be to call humanity to amend its behaviour and return to God.
The Miracle: A great miracle will occur in the late winter or early spring within one year after the warning.
Signs of the Miracle: Permanent signs of the miracle will remain for all time at a pine grove near Garabandal and other selected locations of Marian apparitions.
The Chastisement: A terrible chastisement will occur during which many will die. Other prophecies indicate that this chastisement will eliminate up to two-thirds of humanity.
Two of the girls, Conchita Gonzalez, now aged 67, and Jacinta Gonzales, also age 67, described the first supernatural event, The Warning, in a series of interviews:
"It is a phenomenon which will be seen and felt in all the world and everywhere; I have always given as an example that of two stars that collide. This phenomenon will not cause physical damage, but it will horrify us because at that very moment we will see our souls and the harm we have done. It will be as though we were in agony but we will not die by its effects but perhaps we will die of fright or shock to see ourselves. May the Virgin forgive me if I do not explain it the way it is, but I am trying to tell you ... after knowing what the Warning will be like that day."
"The Virgin told us that the Warning and Miracle will be the last warnings or public spectaculars that God will give us. This is why I believe that after them we will be near the end of time."
"To me, it's like two stars ... that crash and make a lot of noise and a lot of light but they don't fall... It's something that's not going to hurt us but we're going to see it. In that moment, we're going to see our conscience. You're going to see everything wrong that you're doing."
"The Warning is something that is first seen in the air everywhere in the world and immediately is transmitted into the interior of our souls. It will last for a very little time, but it will seem a very long time because of its effect within us. It will be for the good of our souls, in order to see in ourselves our conscience, the good and the bad that we've done. Then we'll feel a great love toward our heavenly parents and ask forgiveness for all our offences."
"CONDITIONS AT THEIR WORST": Jacinta Gonzales - April 1983
"The Virgin said that the Warning would come when conditions were at their worst. It wouldn't be just the persecution either because many people will no longer be practicing their religion."
One year later will then come The Miracle and a short time after, as little as several months or as long as a few years, a global holocaust called The Chastisement. It is unclear whether conditions of war will already be in progress at the time of The Warning.
Conchita Gonzalez says she will announce to the world the coming of The Miracle eight days before it happens. As to The Warning, only Mari-Loli knew the year, and knowledge of that died with her on April 20, 2009 when she succumbed to lupus at age 59.
So, two months ago on March 21, the unthinkable finally happened: two comets made history as the closest that two such bodies have ever passed the Earth within a period of 26 hours. One of them alone was the second closest comet in recorded history, the first being Lexell's in 1770. The other was the 5th closest in all history. Together they were the first event of their kind: an historical precedent.
Now that this event has taken place, some variation of it is free to occur again. When is impossible to say. Regardless of appearances there is no "date setting" on this or my other website. There are however, "windows of opportunity" made possible by the base 7 phenomenon of historical repetition that dominates time and space. Of course God can always set his own date for an event ... and it doesn't have to conform to the base 7 phenomenon.
Those who believe in the Garabandal warning should take note of the March 21-22 event ... for it may have been a preview of The Warning. Or, if you will, it may have been a warning about The Warning.
Next time around, the two comets that approach close to Earth may not simply pass our planet harmlessly within 26 hours of each other at distances of a few million miles ... next time they may be on a direct course to impact the earth or crash into each other high above in our heavens.
Although March 2023 is now a "window of opportunity" one would be ill-advised to keep eyes glued to that date only. It could happen next year or in 2018. Or it could happen in 2037. Or 2060. One Garabandal scholar believes "The Miracle" will occur in the spring of 2020. If he is right, the Warning might then occur in March or April 2019.
But whether one agrees or not, it very much appears we have been given a celestial warning ... about The Warning.
The Miracle follows within 12 months, leaving physical evidence of its appearance. What form The Miracle will take we do not know, but in 1971 Conchita did narrow the months down to March, April, or May, insisting that it will not occur in either February or June. That brings us then to a period that bottoms out around October/November for The Chastisement which will also come from outer space.
So, to summarize: The Warning may be a catastrophe from space that, at the last second, will miraculously terminate far enough away to spare this planet and its inhabitants (we hope). The Chastisement will be a catastrophe from space that will succeed in causing great destruction to earth and its inhabitants.
This will likely take the form of Planet X as it reaches it closest point to earth, a large celestial object also known by the ancient names of Nibiru and Marduk and the biblical prophetic name of Wormwood. Both will bring great terror as mankind watches and awaits.
And what is The Chastisement like?
What They Saw
At a certain time not a single motor is going to operate throughout the world, a terrible heat will come from the sky, and during this time of heat people will look for water and they will not be able to find it, and they are going to attempt to kill one another in their desperation ... But they will lose their strength and fall to the ground. Then it will be understood that it is God alone Who has permitted this. Then we saw a crowd in the midst of flames ... many people will hurl themselves into lakes and seas, but the water will boil and, instead of putting out the great fiery heat, it will excite the flames and make them even more intense ... the chastisement is more terrible than we can possibly imagine because it will come directly from the hand of God ...
This Marian prophecy was revealed over a number of years from 1973 to 1979 to the late Veronica Lueken during Rosary Vigils at the Vatican Pavilion Site in Flushing Meadows Park, New York. Here is a condensed version:
"My child and My children, do not be affrighted by My words. The world shall not come to an end. The Eternal Father has given His promise to mankind, that the world shall never be made extinct again, as in the past with the time of the floods. However, your world shall be cleansed with a 'baptism of fire'. Only a few, in the multitudes upon earth, shall be saved...
I have spoken to you of the BALL OF REDEMPTION to meet with much speculation from souls, I shall explain now, how this will come about: The ball will descend from the atmosphere of your earth: it will be from the heavens; it will not be man-made; it will be part of the universe.
YOU WILL BE PLANET STRUCK!
In this chastisement, My children, billions will be lost. Many lives will be lost. You bring upon yourself a punishment far greater than ever has been seen upon earth and never shall be seen again, for when you go through this chastisement, there will be few creatures left upon earth.
Can you not understand that when the Ball of Redemption is sent upon you three-quarters of your world shall be gone?"
Is the "Ball of Redemption" the recently-discovered "Planet Nine", now moving towards the sun and inner solar system in its highly elliptical, comet-like orbit, or a fiery brown dwarf star hurtling in our direction and as of yet unseen -- a sun that collapsed inwardly, a dark star that has tremendous gravitational influence on everything that it passes, a death star.
According to experts like Immanuel Velikovsky and Zecharia Sitchin, this object was once called Typhon, Marduk, Mazda, Shiva, Wotan, Nibiru, Pallas Athena, and many other names by the ancients during its last passage 3500 years ago in 1495 BC -- the time of Exodus:
Abraham Rockenbach's "De cometis tractus novus methodicus" (1602) --
In the year of the world 2453 (1495 BC) -- as many trustworthy authors, on the basis of many conjectures, have determined -- a comet appeared which Pliny also mentioned in his second book. It was fiery, of irregular circular form, with a wrapped head; it was in the shape of a globe and was of terrible aspect. It is said that King Typhon ruled at that time in Egypt ... Certain authorities assert that the comet was seen in Syria, Babylonia, India, in the sign of Capricorn, in the form of a disc, at the time when the children of Israel advanced from Egypt toward the Promised Land, led on their way by the pillar of cloud during the day and by the pillar of fire at night.
Pliny's "Natural History" --
A terrible comet was seen by the people of Ethiopia and Egypt, to which Typhon, the king of that period, gave his name; it had a fiery appearance and was twisted like a coil, and it was very grim to behold: it was not really a star so much as what might be called a ball of fire.
According to the calculations of Velikovsky and Sitchin, it must return again sometime between 2005 and 2105. When it does, it will come close to earth, causing it to stop in its rotation for three days. Then, in the space of one hour, the earth will shift 90 degrees. During that one hour billions will die. Estimates are that as few as 600,000,000 people will survive. | 0.807458 | 3.479048 |
This post is about dark matter and is the latest in my series on cosmology, the study of the origin and evolution of the Universe as a whole. As readers of my previous posts will recall, dark matter makes up about 27% per cent of the mass of the Universe.
Evidence for dark matter
Our solar system contains the Sun, eight planets with their moons and various minor bodies such as dwarf planets, comets and asteroids. If we plot the speed that each planet orbits the Sun against its distance from the Sun, then we get the curve shown below.
The graph above shows the speed at which the planets orbit the Sun in kilometres per second, plotted against their distance from the Sun in astronomical units (AUs). 1 AU is just under 150 million km and is the average distance between the Earth and the Sun.
The way that the speed of the planets’ orbits falls off with their distance from the Sun indicates that nearly all the mass of the Solar System is concentrated in its centre at the Sun. The further away a planet is from the Sun, the weaker the Sun’s gravitational pull and the more slowly it orbits. See Note 1.
Jupiter, the most massive planet, has only 0.1% the mass of the Sun. In fact the total sum of the masses of all the planets, their moons, dwarf planets (like Pluto), asteroids and comets in the Solar System is less than 1% of the mass of the Sun. This means that the effects of gravity caused by the other bodies in the Solar System on the speed of the planets’ orbit are insignificant.
The Sun belongs to the Milky Way galaxy, which contains about 400 billion stars (Cain 2013). If you were to look at the Milky Way from a great distance, it would look as shown below.
What the Milky way galaxy would look like from outside
All the stars in the Milky Way rotate around its centre, and the Sun rotates at a speed of 782,000 km/hour (Cain 2008). However, the distance between the Sun and the galactic centre is so great (nearly 30,000 light years) that it takes around 230 million years to complete a full revolution. This vast period of time is sometimes called a cosmic year.
Most of the stars in the Milky Way are concentrated near its centre. So if, like the Solar System, most of the matter in the Milky Way were in the form of stars, then it too would be concentrated at its centre. We would expect that as we get further from the centre of mass, then the stars would revolve around the centre of the galaxy more slowly in the same way that the planets orbit more slowly as we get further from the Sun. We would expect a rotation curve (a plot of the speed that a star orbits the centre of the galaxy against its distance) in which the orbital speed falls off with distance from the galactic centre, similar to A in the diagram below.
In fact the orbital speed of a star around the centre of the galaxy does not fall off with its distance from the galactic centre. The rotation curve for our Milky Way galaxy is actually like B in the diagram above. The only way that these results can reconciled with our existing laws of physics is for there to be a large amount of matter in the outer regions of our galaxy which is not in the form of stars. The pull of gravity due to this matter means that the rotation curve does not fall off with distance. Because it does not emit light it is called dark matter and, to produce the flat rotation curves observed for our galaxy, most of its matter must be in the form of dark matter.
In the 1970’s astronomers measured the rotation curves of other spiral galaxies. It became clear that all spiral galaxies had rotation curves in which the speed at which a star orbits the centre of the galaxy does not decrease as a function of the distance from the centre of the galaxy. An early pioneer of this work was the American astronomer Vera Rubin (1928- ) pictured below.
In an influential scientific paper presented in 1980 she and her colleagues presented observations of the rotation curves of a large number of spiral galaxies (Rubin et al 1980). All of these showed rotation curves similar to the Milky Way. To explain her observations, spiral galaxies would need to be surrounded by an invisible dark matter halo which would, in general, have about five times the amount of matter that is held in the galaxy in the form of stars.
This diagram shows a typical spiral galaxy surrounded by an invisible dark matter halo. The bright centre of the galaxy is shown in white and the outer regions of the galaxy are shown in light brown. The dark matter halo, which although shown in blue is invisible, is not flattened in a disk like the galaxy and extends to about 3 times the galaxy’s radius.
Since Rubin’s pioneering work, it is now generally accepted that most of the mass of galaxies is in the form of dark matter.
Clusters and groups of galaxies.
In general, galaxies are found in groups and clusters, the largest of which contain thousands of galaxies. The speed at which these galaxies are moving with respect to each other in these groups and clusters is often very high. For large clusters, such as the one shown below, individual galaxies can be moving at speeds of over 1000 km/s (3,600,000 km/h) relative to each other. To prevent the galaxy groups and clusters from flying apart, something must be holding them together. The most widely accepted explanation of this is that there must be a great deal of dark matter in most galaxy groups and clusters, and it is the force of gravity due to all this dark matter which binds the cluster together.
Part of the Virgo Cluster, a large cluster of galaxies about 50 million light years from Earth
Other Evidence for dark matter
Other evidence for dark matter comes from gravitational lensing, where the strong gravity from clumps of dark matter which lie between a very distant object and Earth actually form a “gravitational lens” and bend light rays causing two images of a very distant object to be seen.
A gravitational lens caused by the large amount of dark matter around a cluster of galaxies (D) causes two separate images (B and C) of a very distant galaxy (A) to be seen.
I won’t say any more about this in this post, but if you would like to know more about gravitational lensing caused by dark matter click here for an interesting article from the phys.org website.
In addition, cosmologist believe that clumps of dark matter were the seeds of galaxy formation. Without dark matter there wouldn’t be enough matter for galaxies to form. How galaxies form is such a huge topic that I could write several posts about it so I will come back to this at a later date.
What is the nature of dark matter?
As you will recall from my previous post ordinary matter is made up of atoms. Some dark matter may be in the form of ordinary matter in objects such as brown dwarfs. These are objects which are midway in size between the lightest stars and large planets such as Jupiter. Because they emit little or no light, brown dwarfs are extremely difficult to detect.
However, for reasons which I’ll discuss in a future post, cosmologists believe that although some dark matter is in objects such as brown dwarfs, most dark matter isn’t made up of atoms. Instead it is made up of an entirely different kind of matter altogether. Various candidates have been suggested for the particles which make up dark matter but none has ever been detected by astronomers or in any particle physics experiment. The nature of dark matter is one of the great unsolved problems in physics.
This post is the fifth in my series about cosmology. The other posts are:
(1) The Universe Past, Present and Future. This describes what is meant by the Universe and gives an overview of its origins, evidence for its expansion and discusses its ultimate fate. To view this post click here.
(2) A brief history of the Universe. This gives a history of the Universe from just after the big bang until the current date. To view this post click here.
(3) Dark Energy. This post gives the reasons why cosmologist believe dark energy exists and why it makes up nearly 70% of the mass of the Universe. To view this post click here.
(4) Dark Energy over Time. This post discusses how the amount of dark energy in the Universe has varied over time and its implications on its future evolution. To view this post click here.
1 It is fairly easy to show, using high school physics, that if all the matter in the Solar System is concentrated in the Sun, then the speed of a planet’s orbit is proportional to the inverse square root of its distance from the Sun.
Cain, F (2008) Sun orbit, Available at: http://www.universetoday.com/18028/sun-orbit/(Accessed: 19 February 2015).
Cain, F (2013) How Many Stars are There in the Universe?, Available at:http://www.universetoday.com/102630/how-many-stars-are-there-in-the-universe/(Accessed: 19 February 2015).
Rubin, V. C.; Ford, W. K. & Thonnard, N. (1980) Rotational properties of 21 Sc galaxies with a large range of luminosities and radii, from NGC 4605 (R = 4kpc) to UGC 2885 (R = 122 kpc). The Astrophysical Journal, Vol. 238, 471–487 | 0.857335 | 3.868052 |
Mid December nights are cold and often snowy on the Western Slope. But, here’s an observing challenge: Catch the peak of this year’s Geminid Meteor Shower on the night of December 13th to 14th.
Meteor showers usually happen when Earth crosses the path of comets, bodies of dirty ice that travel around the Sun in eccentric orbits. Then, small particles of ice and rock shed from a comet may enter Earth’s atmosphere at tens of thousands of miles per hour. Seventy five to 45 miles above the ground, these particles are heated rapidly to incandescence and disintegrate in Earth’s atmosphere, resulting in visible meteors.
The Geminid Shower is a bit different from most meteor showers. Its parent body is not a comet, but a rocky asteroid, called Phaethon. Unlike most asteroids, which orbit the Sun between Mars and Jupiter, Phaethon’s orbit extends from beyond Mars to inside the orbit of Mercury, coming to within 13 million miles of the Sun. When nearest the Sun, Phaethon reaches temperatures of 1400 degrees F and ejects a dust tail composed mostly of silicate minerals.
Each year during mid December, Earth crosses Phaethon’s orbit, and particles that were ejected from Phaethon earlier plunge into our atmosphere, creating colorful meteors. Some of these can be very bright. The name “Geminid” refers to the meteors’ apparent origin point in the sky. This is in the constellation Gemini, an effect of our Earthly perspective on Phaethon’s orbit.
This year’s Geminid Shower takes place under a waning crescent Moon, so even fainter meteors may be visible. From a dark place, look high in the sky, sometime between 8 p.m. and morning twilight. No optical aid is needed. If skies are clear, you may see up to 120 meteors per hour. The peak of the Shower is predicted for 12:30 a.m. on December 14, but meteors may be visible through much of the night in all parts of the sky. But remember - dress warmly!
Western Slope Skies is produced by members of the Black Canyon Astronomical Society. This episode was written and recorded by Art Trevena. | 0.865719 | 3.560086 |
Image credit: ESO
A team of astronomers have spotted an otherwise normal star make a close pass with the supermassive black hole that lurks at the centre of our Milky Way Galaxy. At its closest approach, the star was only 17 light-hours away from the black hole (three times the distance of the Sun to Pluto). Images of the region were gathered over 10 years using the adaptive optics system on the European Southern Observatory’s Paranal Observatory.
An international team of astronomers , lead by researchers at the Max-Planck Institute for Extraterrestrial Physics (MPE), has directly observed an otherwise normal star orbiting the supermassive black hole at the center of the Milky Way Galaxy.
Ten years of painstaking measurements have been crowned by a series of unique images obtained by the Adaptive Optics (AO) NAOS-CONICA (NACO) instrument on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. It turns out that earlier this year the star approached the central Black Hole to within 17 light-hours – only three times the distance between the Sun and planet Pluto – while travelling at no less than 5000 km/sec.
Previous measurements of the velocities of stars near the center of the Milky Way and variable X-ray emission from this area have provided the strongest evidence so far of the existence of a central Black Hole in our home galaxy and, implicitly, that the dark mass concentrations seen in many nuclei of other galaxies probably are also supermassive black holes. However, it has not yet been possible to exclude several alternative configurations.
In a break-through paper appearing in the research journal Nature on October 17th, 2002, the present team reports their exciting results, including high-resolution images that allow tracing two-thirds of the orbit of a star designated “S2”. It is currently the closest observable star to the compact radio source and massive black hole candidate “SgrA*” (“Sagittarius A”) at the very center of the Milky Way. The orbital period is just over 15 years.
The new measurements exclude with high confidence that the central dark mass consists of a cluster of unusual stars or elementary particles, and leave little doubt of the presence of a supermassive black hole at the centre of the galaxy in which we live.
Quasars and Black Holes
Ever since the discovery of the quasars (quasi-stellar radio sources) in 1963, astrophysicists have searched for an explanation of the energy production in these most luminous objects in the Universe. Quasars reside at the centres of galaxies, and it is believed that the enormous energy emitted by these objects is due to matter falling onto a supermassive Black Hole, releasing gravitational energy through intense radiation before that material disappears forever into the hole (in physics terminology: “passes beyond the event horizon” ).
To explain the prodigious energy production of quasars and other active galaxies, one needs to conjecture the presence of black holes with masses of one million to several billion times the mass of the Sun. Much evidence has been accumulating during the past years in support of the above “accreting black hole” model for quasars and other galaxies, including the detection of dark mass concentrations in their central regions.
However, an unambiguous proof requires excluding all possible other, non-black hole configurations of the central mass concentration. For this, it is imperative to determine the shape of the gravitational field very close to the central object – and this is not possible for the distant quasars due to technological limitations of the currently available telescopes.
The centre of the Milky Way
The centre of our Milky Way galaxy is located in the southern constallation Sagittarius (The Archer) and is “only” 26,000 light-years away . On high-resolution images, it is possible to discern thousands of individual stars within the central, one light-year wide region (this corresponds to about one-quarter of the distance to “Proxima Centauri”, the star nearest to the solar system).
Using the motions of these stars to probe the gravitational field, observations with the 3.5-m New Technology Telescope (NTT) at the ESO La Silla Observatory (Chile) (and subsequently at the 10-m Keck telescope, Hawaii, USA) over the last decade have shown that a mass of about 3 million times that of the Sun is concentrated within a radius of only 10 light-days of the compact radio and X-ray source SgrA* (“Sagittarius A”) at the center of the star cluster.
This means that SgrA* is the most likely counterpart of the putative black hole and, at the same time, it makes the Galactic Center the best piece of evidence for the existence of such supermassive black holes. However, those earlier investigations could not exclude several other, non-black hole configurations.
“We then needed even sharper images to settle the issue of whether any configuration other than a black hole is possible and we counted on the ESO VLT telescope to provide those”, explains Reinhard Genzel, Director at the Max-Planck Institute for Extraterrestrial Physics (MPE) in Garching near Munich (Germany) and member of the present team. “The new NAOS-CONICA (NACO) instrument, built in a close collaboration between our institute, the Max-Planck Institute for Astronomy (MPIA: Heidelberg, Germany), ESO and the Paris-Meudon and Grenoble Observatories (France), was just what we needed to take this decisive step forward”.
The NACO observations of the Milky Way centre
The new NACO instrument was installed in late 2001 at the VLT 8.2-m YEPUN telescope. Already during the initial tests, it produced many impressive images, some of which have been the subject of earlier ESO press releases .
“The first observations this year with NACO gave us right away the sharpest and ‘deepest’ images of the Milky Way Centre ever taken, showing a large number of stars in that area in great detail”, says Andreas Eckart of the University of Cologne, another member of the international team that is headed by Rainer Sch?del, Thomas Ott and Reinhard Genzel from MPE. “But we were still to be overwhelmed by the wonderful outcome of those data!”
Combining their infrared images with high-resolution radio data, the team was able to determine – during a ten-year period – very accurate positions of about one thousand stars in the central area with respect to the compact radio source SgrA*, see PR Photo 23c/02.
“When we included the latest NACO data in our analysis in May 2002, we could not believe our eyes. The star S2, which is the one currently closest to SgrA*, had just performed a rapid swing-by near the radio source. We suddenly realised that we were actually witnessing the motion of a star in orbit around the central black hole, taking it incredibly close to that mysterious object”, says a very happy Thomas Ott, who is now working in the MPE team on his PhD thesis.
In orbit around the central black hole
No event like this one has ever been recorded. These unique data show unambiguously that S2 is moving along an elliptical orbit with SgrA* at one focus, i.e. S2 orbits SgrA* like the Earth orbits the Sun, cf. the right panel of PR Photo 23c/02.
The superb data also allow a precise determination of the orbital parameters (shape, size, etc.). It turns out that S2 reached its closest distance to SgrA* in the spring of 2002, at which moment it was only 17 light-hours away from the radio source, or just 3 times the Sun-Pluto distance. It was then moving at more than 5000 km/s, or nearly two hundred times the speed of the Earth in its orbit around the Sun. The orbital period is 15.2 years. The orbit is rather elongated – the eccentricity is 0.87 – indicating that S2 is about 10 light-days away from the central mass at the most distant orbital point .
“We are now able to demonstrate with certainty that SgrA* is indeed the location of the central dark mass we knew existed. Even more important, our new data have “shrunk” by a factor of several thousand the volume within which those several million solar masses are contained”, says Rainer Sch?del, PhD student at MPE and also first author of the resulting paper.
In fact, model calculations now indicate that the best estimate of the mass of the Black Hole at the centre of the Milky Way is 2.6 ? 0.2 million times the mass of the Sun.
No other possibilities
According to the detailed analysis presented in the Nature article, other previously possible configurations, such as very compact clusters of neutron stars, stellar size black holes or low mass stars, or even a ball of putative heavy neutrinos, can now be definitively excluded.
The only still viable non-black hole configuration is a hypothetical star of heavy elementary particles called bosons, which would look very similar to a black hole. “However”, says Reinhard Genzel, “even if such a boson star is in principle possible, it would rapidly collapse into a supermassive black hole anyhow, so I think we have pretty much clinched the case!”
“Most astrophysicists would accept that the new data provide compelling evidence that a supermassive black hole exists in the center of the Milky Way. This makes even more likely the supermassive black hole interpretation for the enormous concentration of dark mass detected at the center of many other galaxies”, says Alvio Renzini, VLT Programme Scientist at ESO.
So what remains to be done? The next big quest now is to understand when and how these supermassive black holes formed and why almost every massive galaxy appears to contain one. The formation of central black holes and that of their host galaxies themselves increasingly appear to be just one problem and the same. Indeed, one of the outstanding challenges for the VLT to solve in the next few years.
There is also little doubt that coming interferometric observations with instruments at the VLT Interferometer (VLTI) and the Large Binocular Telescope (LBT) will also result in another giant leap within this exciting field of research.
Andreas Eckart is optimistic: “Perhaps it will even be possible with X-ray and radio observations in the next few years to directly demonstrate the existence of the event horizon.”
Original Source: ESO News Release | 0.919094 | 3.950337 |
Gas-giant planets orbiting close to other stars have powerful magnetic fields, many times stronger than our own Jupiter, according to a new study by a team of astrophysicists. It is the first time the strength of these fields has been calculated from observations.
The team, led by Wilson Cauley of the University of Colorado, also includes associate professor Evgenya Shkolnik of Arizona State University’s School of Earth and Space Exploration. The other researchers are Joe Llama of Northern Arizona University and Antonino Lanza of the Astrophysical Observatory of Catania in Italy. Their report was published July 22 in Nature Astronomy.
“Our study is the first to use observed signals to derive exoplanet magnetic field strengths,” says Shkolnik. “These signals appear to come from interactions between the magnetic fields of the star and the tightly orbiting planet.”
More than 3,000 exoplanet systems containing over 4,000 planets have been discovered since 1988. Many of these star systems include what astronomers call “hot Jupiters.” These are massive gaseous planets presumed to be like the Sun’s Jupiter but orbiting their stars at close distances, typically about five times the star’s diameter, or roughly 20 times the Moon’s distance from Earth.
Such planets travel well inside their star’s magnetic field, where interactions between the planetary field and the stellar one can be continual and strong.
Previous studies, the team says, have placed upper limits on exoplanet magnetic fields, for example from radio observations or derived purely from theory.
“We combined measurements of increased stellar emission from the magnetic star-planet interactions together with physics theory to calculate the magnetic field strengths for four hot Jupiters,” says lead author Cauley.
The magnetic field strengths the team found range from 20 to 120?gauss. For comparison, Jupiter’s magnetic field is 4.3 gauss and Earth’s field strength is only half a gauss, although that is strong enough to orient compasses worldwide.
The astrophysicists used telescopes in Hawaii and France to acquire high-resolution observations of emission from ionized calcium (Ca II) in the parent stars of the four hot Jupiters. The emission comes from a star’s hot, magnetically heated chromosphere, a thin layer of gas above the cooler stellar surface. The observations let the team calculate how much energy was being released in the stars’ calcium emission.
Says Shkolnik, “We used the power estimates to calculate magnetic field strengths for the planets using a theory for how the planets’ magnetic fields interact with the stellar magnetic fields.”
Cauley explains, “Magnetic fields like to be in a state of low energy. If you twist or stretch the field like a rubber band, this increases the energy stored in the magnetic field.” Hot Jupiters orbit very close to their parent stars and so the planet’s magnetic field can twist and stretch the star’s magnetic field.
“When this happens,” Cauley says,”energy can be released as the two fields reconnect, and this heats the star’s atmosphere, increasing the calcium emission.”
Astrophysicists have suspected that hot Jupiters would, like our own Jupiter, have magnetic fields produced deep inside them. The new observations provide the first probe of the internal dynamics of these massive planets.
“This is the first estimate of the magnetic field strengths for these planets based on observations, so it’s a huge jump in our knowledge,” Shkolnik notes. “It’s giving us a better understanding of what is happening inside these planets.”
She adds that it should also help researchers who model the internal dynamos of hot Jupiters. “We knew nothing about their magnetic fields—or any other exoplanet magnetic fields—and now we have estimates for four actual systems.”
The field strengths, the team says, are larger than one would expect considering only the rotation and age of the planet. The standard dynamo theory of planetary magnetic fields predicts field strengths for the sampled planets that are much smaller than what the team found.
Instead, the observations support the idea that planetary magnetic fields depend on the amount of heat moving through the planet’s interior. Because they are absorbing a lot of extra energy from their host stars, hot Jupiters should have larger magnetic fields than planets of similar mass and rotation rate.
“We are pleased to see how well the magnitude of the field values corresponded to those predicted by the internal heat flux theory,” says Shkolnik. “This may also help us work toward a clearer understanding of magnetic fields around temperate rocky planets.”
More information: P. Wilson Cauley et al. Magnetic field strengths of hot Jupiters from signals of star–planet interactions. Nature Astronomy 2019. DOI: 10.1038/s41550-019-0840-x
Image: This illustration shows a hot Jupiter orbiting so close to a red dwarf star that the magnetic fields of both interact, producing activity on the star. Astrophysicists have used that activity to calculate field strengths in four hot Jupiter star-and-planet systems.
Credit: NASA, ESA and A. Schaller (for STScI) | 0.867906 | 4.005012 |
RIT astronomers on team watching young protostar
RIT astronomers on team announcing the rapidly spinning protostar
NASA’s Goddard Space Flight Center
X-ray observations have revealed something curious about the young star that illuminates McNeil’s Nebula, a glowing jewel of cosmic dust in the Orion constellation: The object is a protostar rotating once a day, or 30 times faster than the sun. The stellar baby also has distinct birthmarks—two X-ray-emitting spots, where gas flows from a surrounding disk, fueling the infant star.
The young star, V1647 Orionis, first made news in early 2004, when it erupted and lit up McNeil’s Nebula, located 1,300 light years away in a region of active star formation within the constellation of Orion. The initial outburst died down in early 2006, but then V1647 Ori erupted again in 2008, and has since remained bright.
More recently, astronomers combined 11 observations of V1647 Ori from NASA’s Chandra X-ray Observatory, the Japan-led Suzaku satellite, and the European Space Agency’s XMM-Newton to determine the source of the high-energy emission. The team began monitoring the star shortly after its eruption in 2004 and continued to keep watch through 2010, a period covering both eruptions.
Strong similarities among X-ray light curves captured over this six-year period allowed the lead author on the study, Kenji Hamaguchi, astrophysicist at NASA’s Goddard Space Flight Center, to identify cyclic X-ray variations. Hamaguchi and the rest of the team determined the star is rotating once per day, making V1647 among the youngest stars whose spin has been determined using an X-ray-based technique. Results from the study will appear in the paper “X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori,” in the July 20 issue of The Astrophysical Journal.
“The observations give us a look inside the cradle at a very young star,” says co-author Joel Kastner, a professor of imaging science and astronomical sciences and technology at Rochester Institute of Technology. “It’s as though we’re able to see its beating heart. We’re actually able to watch it rotate. We caught the star at a point where it is rotating so fast as it gains material that it’s barely able to hold itself together. It’s rotating at near break-up speed.”
The team identified V1647 Ori as a protostar in formation. “Based on infrared studies, we suspect that this protostar is no more than a million years old, and probably much younger,” Hamaguchi says.
V1647 Ori presently feeds on gas channeled from a surrounding disk and will likely continue to do so—though not nearly so rapidly—for millions of years. At that point it will finally be able to generate its own energy by fusing hydrogen into helium in its core like the sun and other mature stars.
Hamaguchi’s analysis focused on repetitive behavior found in the data from all three of the X-ray observatories. By combining data, he pieced together a picture showing the daily rotation of two X-ray-emitting spots on V1647 Ori that are thousands of times hotter than the rest of the star.
The hot spots are located at opposite sides of the star, with the southerly one five times brighter than its companion. Each spot is about the diameter of the sun. In comparison, the low density of V1647 Ori bloats the star itself to nearly five times the size of the sun.
“We think these spots are showing us X-ray-emitting regions that are very tightly constrained to a couple positions on the star by magnetic fields,” says Kastner, director of the Laboratory for Multiwavelength Astrophysics in RIT’s Chester F. Carlson Center for Imaging Science. “For six years, through two different eruptions, we’ve seen it rotate like this. That means the magnetic field configuration—the overall geometry between the disk and the star—is very stable. At the same time, the local disruption of magnetic fields probably generates the X-rays.”
“One attractive possibility for driving such high-speed matter involves magnetic fields that are undergoing a continual cycle of shearing and reconnection in mass accretion,” says co-author David Weintraub, professor of astronomy at Vanderbilt University.
In this picture, X-ray outbursts result from interplay of the magnetic fields belonging to the star and the disk. The star spins faster than the disk and winds up the magnetic fields until they snap like rubber bands. The pent up energy creates a powerful blast when the tangled magnetic fields fall back into place. The process, called magnetic reconnection, also powers X-ray flares on the sun.
During the outbursts, the star’s luminosity varied at optical and infrared wavelengths. The astronomers associated this to changes in the protostar’s main energy source, the inflow of matter onto the star. Because changes in the X-ray brightness of V1647 Ori closely followed those in the optical and infrared, the team established that its higher-energy emission is also closely linked to accretion.
“V1647 Ori gave us the first direct evidence that a protostar surges in X-ray activity as its rate of mass accretion rises,” says co-author Nicolas Grosso, an astrophysicist of the French National Center for Scientific Research at the Strasbourg Astronomical Observatory.
The finding that an accretion burst could be accompanied a surge of high-energy X-rays during the formation of a young star was originally announced by essentially the same study team, led by Kastner, in a paper published in Nature in 2004. In that paper, the team first argued that X-rays emitted by V1647 Ori were coming from material falling onto the star from a surrounding disk.
Up until then, the more widely accepted mechanism for producing X-rays from protostars was thought to be via coronae that are far more powerful than the sun’s, Kastner explains. Signatures in X-ray observations of a handful of stars in formative stages had led to the hunch that accretion might also contribute to or even dominate protostellar X-ray emission. The eruptions of V1647 Ori and a few other young stars that were accompanied by elevated X-ray emission levels have since underscored this connection, Kastner notes.
“The exciting and unexpected thing about our fresh look at the whole set of X-ray data for V1647 Ori is that this is the first time we’ve seen a star in such an early stage of formation with a regular rotation that you can measure in X-rays,” Kastner says.
Kastner and team hope to confirm the X-ray study’s findings at infrared wavelengths using NASA’s Spitzer Space Telescope.
Additional co-authors on the study include Michael Richmond, professor of physics at RIT; David Principe, a doctoral candidate in RIT’s Astrophysical Sciences and Technology program; and William Teets, a recent doctoral recipient in physics and astronomy from Vanderbilt University. | 0.905801 | 3.773278 |
An alert over a close shave by a threatening asteroid has been called off after it was found to be a passing spaceprobe called Rosetta. The alarm was raised by the Minor Planet Center, the world’s official HQ for logging newly discovered space rocks and checking for any “Near Earth Objects” that threaten a devastating impact.
They issued an email circular to professional observatories last week announcing that an asteroid had been detected that would miss the Earth by a whisker on Tuesday, November 13.
The near miss, by 5,600 km – less than half the diameter of the Earth – looked set to be one of the closest on record. The MPC, which is run by the Smithsonian Astrophysical Observatory, Massachusetts, for the International Astronomical Union, even gave the body an official label, 2007 VN84.
Detailed observations by astronomers worldwide who discover and monitor potentially deadly asteroids were used to calculate an accurate track for the incoming “missile”.
Britain’s Royal Astronomical Society was preparing a special announcement to the media on Monday to reveal one of the closest cosmic shaves with disaster ever recorded. Then one sharp-eyed scientist, Denis Denisenko, 36, of Moscow, spotted that the asteroid’s track matched that of a European comet-chasing spaceprobe called Rosetta.
The craft, which is the size of a box van, is scheduled to make a swing past Earth on Tuesday for a gravity boost to speed it like a slingshot on its ten-year journey to Comet Churyumov-Gerasimenko.
Rosetta, launched in March, 2004, by the European Space Agency (ESA) has already made one swing-by of Earth in March 2005, another past Mars in February this year, and it will pass us again in November 2009.
Ironically, the unmanned probe will also fly close to and study two minor planets, Steins and Lutetia, during two journeys through the asteroid belt in 2008 and 2010.
Denisenko emailed an online discussion group for asteroid observers revealing his discovery. Embarrassed officials at the Minor Planet Center were forced to email a fresh circular announcing: “The minor planet 2007 VN84 does not exist and the designation is to be retired.”
But they added: “This incident highlights the deplorable state of availability of positional information on distant artificial objects (whether in earth orbit or in solar orbit). A single source for information on all distant artificial objects would be very desirable.”
Despite the red faces, the MPC perform vital work and there have been very real near misses by genuinely threatening asteroids that demand monitoring. The world’s biggest digital camera recently joined the search for them.
The Rosetta probe, which is due to plant a lander on its target comet in 2014, measures 2.8 x 2.1 x 2.0 metres. Its enormous solar panel “wings” stretch 32 metres from tip to tip and each is 32 sq metres in area.
Update: Rosetta’s flyby was a complete success with the probe right on course and producing some spectacular photos of the Earth as it approached.
Our picture is an ESA artist’s impression of Tuesday’s flyby by Rosetta.
★ Keep up with space news and observing tips. Click here to sign up for alerts to our latest reports. No spam ever - we promise! | 0.874286 | 3.239125 |
By Mireia Montes Quiles
Astronomers have captured the first image ever of a black hole. As part of the Event Horizon Telescope (EHT) project, the team simultaneously took observations using telescopes around the globe to take one of the most detailed images ever of a black hole 55 million light-years away from us.
What is all this fuss about?
A collaboration of more than 200 scientists have taken the very FIRST IMAGE of a black hole! This is an incredible achievement and it is technically amazing; they used 8 telescopes observing at the same time…
Wait… what is a black hole, again?
A black hole is a region of space where the gravitational field is so intense that no matter or radiation can escape. The center of the black hole, the singularity, is a point in spacetime that contains ALL the mass of the black hole; where the density is infinite. The gravity that this singularity produces is so strong that there is a region where not even light can escape. The edge of it, the point of no return, is called the event horizon. Like the telescope! Exactly.
Aaah! Got it. Can you explain this image to me? Why does it look like an orange donut?
Actually, we are not seeing the black hole because no light can escape from it.
An active black hole, like this one, has an accretion disk: a disk of gas and dust surrounding and feeding it. The friction heats this gas to temperatures of billions of degrees and consequently it glows. The path of this light is affected by the strong gravity of the black hole, bending it if it passes nearby. This is what creates the ring of light in the image. If too close, photons (light) are then trapped in orbits around the black hole, and eventually will fall into it. This region of photon orbits is the famous shadow of the black hole, 2.5 time larger than the event horizon, the hole of the donut.
The colour just represents how intense the emission of light is, brighter at the bottom because the black hole is spinning**.
How did they take this image?
The image has been taken in radio wavelengths, the ones used by radios in the past! Astronomers can take these radio waves and use a technique called interferometry to combine the information from different telescopes. This technique uses the separation between the telescopes to simulate a telescope of the size of this separation. For these observations, they used EIGHT telescopes around the globe, which means that it was basically a telescope the SIZE OF THE EARTH!
Why do we need such a big telescope?
Because we want to take such a detailed picture that we could see objects of the size of the solar system in a galaxy 55 million light-years away. To give you an idea of the detail we need, what we are seeing in this picture is the size of an orange on the moon. What?? Crazy.
Why is this image so important?
Apart from the fact that this is a technical success, with this image we are able to tell that Einstein’s theory of General Relativity accurately predicts what happens in these regions of such strong gravity. The theory predicts that the structure is nearly circular, which is what we have seen.
*Or a thousand times more massive than Sagittarius A*, the black hole of our galaxy.
** This effect is called relativistic or Doppler beaming. It tells us the direction where the black hole is spinning: clockwise in the sky.
Follow Mireia on Twitter | 0.869043 | 3.949781 |
Authors: Yoast-Hull, Gallagher, Halzen, Kheirandish, and Zweibel
First Author’s Institution: University of Wisconsin-Madison/Wisconsin IceCube Particle Astrophysics Center
Status: Submitted to Physical Review D, [open access]
What is the Cygnus region?
The Cygnus X region is a particularly interesting region of the sky. Located in the Galactic plane and named because it is located in the Cygnus constellation, it is the largest star-forming region in the entire Milky Way. It contains massive clouds of molecular gas, which are important for star formation, and many young stars. Gamma rays (the most energetic form of electromagnetic radiation) have also been detected in the region by a number of other experiments, including Fermi-LAT and Milagro. In gamma rays, point sources and regions of extended emission make the area very confusing. One of the most interesting extended regions is known as the “Cygnus Cocoon“.
In some scenarios, the interactions that produce gamma rays are also expected to produce neutrinos, tiny little particles that are useful as astrophysical messengers. Detecting neutrinos from the Cygnus X region is interesting because it would give evidence that a PeVatron lies in the Galactic disk. A PeVatron is a source that accelerates protons up to 1 PeV and are one of the key components to determining exactly how cosmic-ray acceleration* works, one of the great unsolved mysteries in particle astrophysics. To give an idea of the energy scale, this is orders of magnitude larger than what the Large Hadron Collider can accelerate to on Earth! The HESS experiment made waves earlier this year when they announced that they had seen evidence of a PeVatron at the Galactic center (Astrobites writeup here), but to date, this is still the only PeVatron discovered.
*You may wonder why we focus on gamma rays and neutrinos instead of cosmic rays themselves. For one, they are a lot easier to interpret, since they are both neutral and don’t curve in magnetic fields on their journey to Earth.
The authors set out to determine if the neutrino spectra from the Cygnus region has a large enough flux to be detected by IceCube, a neutrino experiment located in Antarctica. This was a multi-step process: first, they came up with a model for the interstellar medium in the region by deriving gas column densities and incorporating dust maps into a calculation of the interstellar radiation field. They then modeled the gamma ray emission in the region by comparing with observations to make sure there was rough agreement and then calculated the corresponding neutrino flux.
Results and Implications
Unfortunately, it turns out that the neutrino flux associated with diffuse emission in the Cygnus X region is much below IceCube’s sensitivity, eliminating the possiblity that neutrinos will be detected from the region.
However, looking at the Cocoon region gives a different picture. The calculated neutrino spectra at 1 PeV is just above IceCube’s discovery potential for point sources. Since the Cocoon is extended, the discovery threshold is slightly lower in reality and there is an even a greater chance of IceCube seeing something.
The authors also looked at a small region of the Cygnus Cocoon that is coincident with a molecular cloud. They chose this region because it is likely to be associated with hadronic emission (which would create neutrinos) from a single cosmic-ray accelerator such as a supernova remnant or pulsar wind nebula. The neutrino flux from this molecular cloud is regrettably too low to be detected by IceCube.
With our current understanding of the area, there is a chance that the overall Cocoon region could be detected in neutrinos (see the figure above). If this happens, it will increase our knowledge of how cosmic-ray accelerators are distributed in the sky, and provide the first evidence of a PeVatron in the Galactic disk. | 0.906747 | 4.010451 |
Happy New Year! Welcome to January 2016, and if you haven’t made a New Year’s resolution yet (or you have made one but want to sneakily change it,) why not challenge yourself to star gaze this year. Star gazing is a brilliant past time and is a wonderful activity that all the family can get involved in. Set yourself a goal each month, and try and spot something fantastic. Our monthly guide to the night sky will be able to help you over the course of the year.
To start out your year of stargazing, there is a wonderful meteor shower at the start on the month. The Quadrantids meteor shower will be at its peak on 3rd and 4th of January. This shower runs annually from 1st – 5th January and is produced by dust grains left behind by the comet known as 2003 EH1. This particular comet is an extinct comet. What’s that I hear you ask? Well an extinct comet is a comet that has expelled most of its volatile ice, and has very little left to form a tail. At its peak, the Quadrantids meteor shower can produce up to 40 meteors per hour. These meteors will radiate from the constellation of Boötes, but they can appear anywhere in the night sky.
If you were lucky enough to have received binoculars or even a telescope for Christmas you could try looking for Comet Catalina (C/2013 US10 Catalina). It is just outside the limit of unaided eye visibility, but binoculars should reveal it as a small fuzzy blob of light. On 1 January 2016, the comet was close to Arcturus in the constellation Bootes and was easily found and the comet will spend the first half of January moving between Arcturus and the tip of the Plough’s handle. You can follow the comet’s progress with the chart at this link.
Two other good targets for new binoculars and telescopes are the planets Mars and Jupiter. Look south in the morning before sunrise to see them flanking the constellation of Virgo. Just before dawn a faint Saturn and a brilliant Venus will be seen in the brightening sky. Very, very low down (you’ll need an empty horizon) and tough to see will be little Mercury, making it just possible to see all the classical planets roughly aligned in the sky.
On 10th January there will be a New Moon in the sky. There will be no moonlight in the sky to hinder your viewing, so why not wrap up warm with lots of blankets and jumpers, and go outside and see what you can see. We do not recommend going out in wet weather, not only will you get soaked, but you’ll be cold too!
Try looking out for the Winter Circle this month. The circle (although it looks more like a hexagon to me) is an asterism made up of six stars that all belong to different constellations. As the name would suggest, the Winter Circle is found in the sky around winter time. Don’t try looking for it in the summer, as it won’t be there. The stars found in the Winter Circle are: Rigel, Aldebaran, Capella, Pollux, Procyon and Sirius.
Rigel, also known as Beta Orionis, is the brightest star in the constellation of Orion the Hunter. It is also the seventh brightest star in the sky, with a visual magnitude of 0.13. Although it has the Bayer designation of “Beta,” it is almost always brighter than Alpha Orionis, commonly known as Betelgeuse.
Aldebaran is an orange giant star about 65 light years away from the Earth. It is found in the constellation of Taurus. The name Aldebaran is derived from Arabic and it roughly translates into “The Follower.” It is a double star, and William Herschel was the first person to discover the faint companion in 1782, however the star was shown to be a double star in 1888 by the astronomer Sherburne Wesley Burnham (who ended up compiling the Burnham Double Star Catalogue).
Capella is the brightest star in the constellation of Auriga. The name Capella is derived from the diminutive of the Latin “capra”, meaning “goat,” hence the term “little goat,” for the star. Capella is also known as Alpha Aurigae, and it appears to be a single star in the sky, however it is actually a star system of four stars in two binary pairs. This star system is roughly 42.8 light years away from Earth.
Pollux is the brightest star in the constellation of Gemini. About 34 light years from us, this star is even brighter than its neighbour in the sky, Castor (which is about 51 light years away). Pollux is an evolved giant star with an orange hue meaning that this star has exhausted the supply of hydrogen in its core and switched to thermonuclear fusion of hydrogen in a shell surrounding the core. Pollux is larger than our Sun and is about two times the mass of our Sun, and nine times the radius. It has at least one planet, β Gem b, a gas giant about twice as massive as Jupiter which was recently named Thestias.
Procyon can be found in the constellation of Canis Minor, and it is the brightest star in this constellation. It has a visual apparent magnitude of 0.34, and is a classified binary star system. It is the eighth brightest star in the sky. The name Procyon comes from the Greek “Prokyon,” meaning “Before the Dog,” since it preceded the “Dog Star,” Sirius as it travels across the sky. Now you’ve heard of the Summer Triangle, which you can see in the sky during the summer time and is made up of three different stars (Vega, Deneb and Altair) belonging to three different constellations, well Procyon just so happens to form one of the three vertices of the Winter Triangle. The other two stars belonging to this triangle are Betelgeuse and Sirius and these two can be found in different constellations. Betelgeuse is found in Orion and Sirius is found in Canis Major.
The final star in the Winter Circle is Sirius and it can be found in the constellation of Canis Major. This is the brightest star in the Earth’s night sky and has a visual apparent magnitude of -1.46. We’ve written a lot about this star before so I won’t bog you down in the nitty gritty details, but here are some cool facts about this star. Sirius’ Bayer Designation is Alpha Canis Majoris, and what the naked eye sees as a single star, is a actually a binary system. It consists of a white main-sequence star of spectral type A1V, termed Sirius A and a faint white dwarf companion of spectral type DA2, termed Sirius B. Sirius is gradually moving closer to the solar system so it will increase in brightness over the next 60,000 years.
To complete this glorious month of stargazing there will be a full moon on 24th January. Naturally this moon has many names, including the Native American name of the Full Wolf Moon. It is known as the Wolf Moon because at this time of the year the hungry wolves would howl outside the tribe’s camps. It is also known as the Moon after Yule as it is the first full moon after the winter solstice. This name however is not quite relevant to this full moon this year, as we had a full moon on Christmas day, so that technically would have been the Moon after Yule.
(Article by Heather Taylor, Education Support Officer) | 0.842121 | 3.230851 |
When Time Stands Still:
Exploring Stationary Planets
© Michele Finey 2015, 2020
Note: This article was first published in the Oct/Nov 2015 edition of The Mountain Astrologer. Slight changes and edits have been made to this version.
As planets move through the zodiac, they take us on a journey through time. Past, present and future are examined through the lens of a chart of the heavens calculated for a specific moment. Planets that appear to be stationary represents key moments in that journey when, in a sense, time appears to stand still.
In a traditional context, slow and stationary planets are perceived as debilitated, afflicted, or malefic. For the most part, they are considered to be weak. Yet, some astrologers, both ancient and modern, interpret stationary planets in quite a different way.
In Ptolemy’s Tetrabiblos, we read that stationary planets are akin to rising planets in terms of their potency. Ptolemy believed that a stationary planet — far from being weak or afflicted — was arguably one of the most powerful planets in a chart. Whether Ptolemy was an astrologer or simply a scribe who catalogued the astrological consensus of his time, his view was that stationary planets were very strong indeed:
“… the effect will be strengthened and augmented by their matutine or stationary position; but weakened and diminished by their being vespertine, or situated under the sunbeams, or by their midnight culmination
How we interpret stationary planets may depend on the type of chart we are examining. For example, in a horary chart, the stationary planet is thought to impede. Its lack of apparent motion is said to prevent further developments. This makes logical sense, because in horary work we are mostly concerned with that exact moment. As a rule, we don’t examine transits or progressions to the horary chart, so if a key planet is stationary, then the matter concerned is most likely at a standstill, at least for the foreseeable future.
Speedy motion symbolises strong impulse, so when a significator is direct in motion and moving swiftly, we judge whatever it signifies as moving directly towards its objectives and having a strong impetus to make something happen. This is a signature of someone with a strong will and a clear sense of purpose (however misguided that purpose may be). By contrast, a significator that moves slowly is regarded as hindered or impeded, suggesting hesitancy or protracted labouring over something difficult to accomplish.
In the June/July 2014 issue of The Mountain Astrologer, Kenneth Johnson’s article, ‘The Many Faces of Mercury Retrograde,’ discusses some of the ways that astrologers through the ages have interpreted stationary (and retrograde) planets. Vettius Valens, for example, was of the view that such planets were debilitated and weak, but Johnson points out that, in Indian tradition, retrograde and stationary planets were considered to be stronger than when moving direct.
So, where does that leave us? Just how should we interpret these motionless planets that appear to be changing course? Are they strong or weak?
Whether stationing retrograde or direct, planets that have no (or very little) apparent motion hover at the same zodiacal position for days, sometimes weeks. If we think of the zodiac as being a journey through time, then when planets are moving retrograde, they are, in a sense, venturing back into the past before resuming forward motion once more. When they are stationary, the present moment is therefore magnified, accentuated, or highlighted. Time appears to stand still. Planets are close to the Earth when retrograde, so their station marks a special moment in space–time when the planet concerned is very accessible. This suggests that planets are indeed strengthened by being stationary.
Those people born when a planet is stationary and appearing to change direction are likely to embody the nature of this planet to a great extent, for better or worse.
A stationary direct (SD) planet in a natal chart will progress over the years and will pick up speed. Conversely, a planet that is slowing down will turn retrograde by progression at some future time. We are not static organisms; we grow and evolve. Planets that station retrograde, or direct by progression often mark major turning points in life. Since the stationary planet is in the process of changing direction, this implies that it can herald reversals of fortune.
In the natal chart, a stationary planet can present us with problems and challenges, or can be a real asset. Either way, they are powerful.
In Retrograde Planets, Erin Sullivan says of the stationary retrograde (SR) planet:
“One often finds it difficult if not impossible to express oneself to one’s satisfaction. This can result in obsessive or compulsive types of behaviour or dedication to rigorous detailed work which through its thoroughness satisfies one’s sense of completion and success.”
SR planets can present us with some big challenges. We have to dig deep to find the fortitude required to harness their energy. These planets therefore foster endurance, staying power, focus, and dedication. The frustration that can accompany the SR planet is often a catalyst, but for some individuals, the challenges may be too much. This could be why stationary planets are said to block or impede. There is a powerful urge to express the stationary planet, but its lack of motion means that it takes a great deal of stamina and time to get results.
Of the SD planet, Sullivan says:
“[It] has already constellated a great amount of power and is virtually trembling for an avenue for expression. Unless there are other aspects to the planet that promote a channel for the energy, then it is likely to have little grounding in the early years of one’s life.”
When resuming forward momentum, the stationary direct planet urges us to get moving, but at the same time this planet is not easy to master, especially early in life. It’s raw and fresh and has to move into uncharted territory. Over time, as the planet progresses, we have an opportunity to develop this natal planet, to express it outwardly as it gains momentum and speed, but at first it can be a real monkey on our back.
“The past can’t be changed, but the future is ours to shape, if we make the effort.”
— His Holiness, the 14th Dalai Lama (Jupiter SD 13.28 SC)
The stationary retrograde planet tends to be more challenging than the stationary direct one. But whether we view these planets in a positive or negative light, whether they are capable of impeding or empowering, may ultimately depend on other factors, such as sign placement, or aspects to the stationary planet that can aid our interpretation.
Still, other questions remain. What orb of exactness should we apply to stationary planets? In other words, how slow does a planet have to be for its slower motion to be considered significant? And what about the so-called shadow periods? These are the times before and after a station when the planet is travelling direct, but moving over the same degrees it traverses when retrograde. I decided to look more closely at stationary planets to try to answer some of these questions.
Over recent years, there has been a lot of discussion surrounding what are called ‘shadow periods’ — times when a planet is moving in direct motion, just before and after its retrograde period, and passing over the same degrees that it travels when retrograde. It has been said that these shadow times have some of the elements of retrograde periods, only to a lesser extent.
Personally, I am not convinced that shadow periods have any merit. If you factor in these shadow degree areas and plot them over time, you will see why. In the case of Mercury, there are three retrograde passages every year, each of which spans three weeks. If we add on the shadow periods, we have an extra six weeks of shadow time per retrograde. This equates to about six months of the year when Mercury will be either retrograde or in shadow. Although Mercury is well known for its capacity as a trickster, six months seems rather a long time.
In the case of Mars, it will be shadowy or retrograde for about six months every two years — roughly 25% of its synod. For Saturn, there are approximately six weeks between the end of one shadow period and the start of the next one. With the slower-moving planets, you end up with overlapping, or double, shadows. Uranus is always in shadow or retrograde and in the case of Neptune and Pluto, one shadow period is still in effect when the next shadow period commences. (See Table 3,)
|Dec. 12, 2014||April 15, 2015||Sept. 25, 2015||Jan. 16, 2016*|
|12°58’ Cap||15°32’ Cap||12°58’ Cap||15°32’ Cap|
|Dec. 29, 2015*||April 18, 2016||Sept. 26, 2016||Jan. 17, 2017|
|14°55’ Cap||17°29’ Cap||14°55’ Cap||17°29’ Cap|
Table 3: Pluto’s shadow. Two successive retrograde periods of Pluto are shown with their shadow periods. *Note that the first shadow period is in effect until Jan. 16, 2016 and overlaps with the next shadow, which commences on Dec. 29, 2015.
I have not personally investigated these ‘double shadows’ to see if they have any particular astrological significance, but on the face of it, this calls into question the whole concept of shadow periods. If you go along with the idea of shadow periods, then you also have to accept that, for some planets, there are double shadows.
Setting aside the idea of shadow periods, the real question is: What kind of orb should we allow for a stationary planet? In other words, how slowly does a planet have to be moving to have some kind of added intensity or other effect?
Apparent retrograde motion occurs as part of a planet’s synodic cycle: the number of days between one conjunction with the Sun and the next. In the case of Venus and Mercury, each of which makes two solar conjunctions per cycle, this is the number of days between one inferior conjunction and the next. Most astrology software programs allow a few days for stations, and all stationary planets are flagged S for the same number of days. But if you consider that the length of each planet’s orbit differs, it is technically more accurate to allow for a variable orb according to a planet’s speed.
Table 1: The number of days of each planet’s synodic cycle
Average Speeds and Orbs for Stations
Because planets move at different speeds and have synodic cycles that vary in length, the orb we apply to stations should take this into account. Using a planet’s average speed is one way to do this. But it turns out that a planet’s average speed is not an easy thing to calculate. It depends on a range of factors, such as the time period over which its motion is averaged. For Mercury and Venus, in particular, this can yield quite different results.
In Deborah Houlding’s series on Horary in TMA, she points out that the average speeds for Mercury and Venus are often said to be the same as the Sun.
Other sources, however, list their average speeds as being significantly faster than the Sun, which is true. Astronomically, Mercury and Venus do move faster than the Sun.
In the Solar Fire astrological software, the average daily speeds for Mercury and Venus are the same as for the Sun: 59°08’ when in fact they move much faster. I am not a computer programmer, so I have no idea why the speeds of Mercury and Venus are not accurate, but it must have something to do with the fact they are inferior planets. But I won’t labor the point here.
Using Solar Fire, the default setting flags planets with an S for two days before and two days after each exact station. Thanks to the developers of this fantastic astrology software, we are offered a choice in the way we set orbs for stations.
In the preference settings for stations, the default setting is option 1. This option gives you an orb of two days before and two days after each exact station, so that any planet falling within this time range will be flagged with an S to indicate that it is barely moving. You will notice that the colour of the S in a chart will change at the exact moment of the station. This is the default setting, so unless you change it, all stationary planets will be flagged with an S for four days at their station retrograde and again for four days when they turn direct. For a very long time, I used this setting — until it occurred to me that choosing a variable orb would take into account the different synodic cycles (shown in Table 1) and speeds of the planets (see Table 4, **).
Diagram: Screen shot of Solar Fire’s preference settings for stationary planets. Option 1 is the default setting; option 4 takes into account each planet’s speed and their different cycles.
Preference 4 lets you choose a percentage of a planet’s average speed, so that any planet moving slower than this will be flagged S.
|Planet||Average speed||Highest speed||Lowest speed|
Table 4: Average speed of the planets
(Source: http://www.starfisher.cz/starfisher/EN/ )
After choosing this setting, I set to work examining every chart in my database, in total, thousands of charts. I tweaked the percentage up and down, looking at natal and event charts to determine an orb that worked for all stationary planets.
After spending weeks looking through my database and trying different percentages in option 4, I decided to use 30%. This means that whenever a planet is moving slower than 30% of its average speed, it will be flagged with an S.
In the case of Mercury, using the 30% rule gives you a window of 4 to 8 days per station, which might account for any kind of so-called shadow effect. Rather than having a shadow of six weeks, you have a period of 4–8 days when Mercury is considered to be within orb of station, or slow enough to have a noticeable effect.
Note that because some planets have more elliptical orbits than others, their speed will be faster in some signs and slower in others, so their station orb will differ be slightly different from one chart to another according to its sign placement. Mars, Pluto, Chiron, and Mercury have quite elliptical orbits, and as a result, the length of their stations will be slightly different in each chart you calculate.
While 30% might seem high, keep in mind that this is a percentage of average speed, and average speeds are much slower than a planet’s fastest motion. Though the way in which average speeds are calculated can vary, this setting works well — that is, the themes of the stationary planet in question appear to be quite obvious or prominent in the event or life of the individual.
In the case of Venus and Mercury, you may want to consider mentally factoring in an extra day or two before and after the S appears in charts, to account for the way that average speeds are calculated within your astrology software.
Since Mars has the longest synodic cycle, it also has the longest orb duration for its station. Using this 30% rule, Mars will be flagged S for about three to four weeks at each station. (See Table 5, **.)
The 30% rule captures a range of charts that seem to support and validate this setting. Of course, you may have other ideas about what kind of orb to give to a station, but I urge you to consider the 30% rule as a starting point. Do your own research and see what works for you. But whatever you decide, it is important to consider a variable orb, rather than a blanket 4 day time period for all stationary planets.
|Planet||Synod||Approximate station orb|
using the 30% rule
|Mars||780 days||21–28 days|
|Venus||584 days||15 days|
|Ceres||467 days||18–20 days|
|Jupiter||399 days||15 days|
|Saturn||378 days||12 days|
|Chiron||373 days||8–14 days|
|Uranus||369 days||8 days|
|Neptune||367 days||7 days|
|Pluto||367 days||4–7 days|
|Mercury||116 days||4–8 days|
Table 5: Planetary synods and station periods (using the 30% rule)
It’s a common mistake to think that Pluto has the longest synodic cycle, when actually it’s Mars. Consider that, from one year to the next, Pluto will not move very far, so its conjunctions with the Sun will occur at 367 day intervals. But Mars is situated in a similar part of the solar system as the Earth, so when viewed from Earth, Mars and the Sun only join in conjunction every 780 days, making Mars the longest synod.
Mars has the least frequently occurring retrograde cycle, and it’s fair to say that it’s probably the most challenging. Because Mars is associated with forward momentum, drive, action, and activity, its stations can denote critical times when progress comes to a halt. Although stationary Mars can impede one’s energy and drive, it can also produce incredible stamina and staying power.
The different ways that astrologers interpret stationary planets may come down to the fact that, for some of us, the difficulties that these planets create can push us to strive for bigger and better things, but in other cases they can create insurmountable obstacles that we cannot overcome. The stationary planet can be both a hindrance and our greatest asset.
The painstaking research undertaken by Michel Gauquelin (who was himself born with Mars SR) revealed that Mars rising or culminating is associated with sports champions. It’s a proven signature for athletic prowess. Yet, in the charts of some other outstanding athletes, Mars is stationary. Usain Bolt (SD), Martina Navratilova (SD), and Rafael Nadal (SR) are three examples. Having an ‘immobile’ Mars has not impeded their competitive spirit, energy, or drive, but has actually intensified it. There are also a number of great athletes with Mars retrograde, including Steffi Graf, Billie Jean King, and Tiger Woods. If a retrograde or stationary Mars only blocks or thwarts the action of Mars, how is it that we find it in the charts of elite sports champions?
We also know that Gauquelin found that Mars rising or culminating is associated with the medical profession. Using the 30 per cent rule, the charts of both Sigmund Freud and Carl Jung we find Mars is stationary direct in the 11th house (Placidus) a symbol of their pioneering work in the fields of psychiatry and psychology.
|Ella Armitage, pioneering female archaeologist||SR 05°38’ Sco|
|Lance Armstrong, cyclist/athlete and drug cheat||SD 12°27’ Aqu|
|Julian Assange, activist/Wikileaks founder||SR 21°33’ Aqu|
|Lauren Bacall, actor||SD 25°35’ Aqu|
|Truman Capote, author||SD 25°48’ Aqu|
|Joe Frazier, boxer||SD 05°11’ Gem|
|Dr. William Masters, sex researcher||SR 29°44’ Leo|
|Karen Silkwood, activist/whistleblower||SD 14°08’ Can|
|Mark Spitz, Olympic swimmer/gold-medalist||SR 11°02’ Lib|
|Samantha Stosur, tennis champion||SR 28°06’ Sco|
Table 2: More examples of stationary Mars
Stations in Natal and Event charts
If you calculate the chart for Christopher Reeve’s tragic accident using the 4 day default setting for stations, Mercury appears retrograde and asteroid Hygeia (health and healing) is direct. If you calculate this event chart using the 30% rule, both Mercury and Hygeia are flagged S, which highlights the fact that both planets were about to station and were therefore significant factors at that time. Similarly, in Reeve’s natal chart, using the standard 4 day orb, Hygeia would be flagged R, but using the 30 per cent rule it’s flagged S.
At the time of his accident, the transiting Mercury station at 17°55’ Gemini was in tight opposition to his natal Mars at 18°15’ Sagittarius, which sits in his 5th house (Placidus). Reeve’s chart has a very tight quincunx between Mars and Uranus in his natal chart, an aspect well known to be associated with accidents. This aspect was repeated in the heavens on the day he fell from his horse. With the transiting Mercury station powerfully positioned in its own sign of Gemini, opposing Reeve’s natal Mars, we have an extra factor that suggests the potential for an accident. Some moments in time are indeed more significant than others.
In the chart of England’s King George III, we see Mercury stationary retrograde in its own sign of Gemini and involved in a stellium with Saturn, Venus, and Neptune. The actual station of Mercury took place three-and-a-half days before his birth, so if you use the default setting for stations, Mercury would be flagged R rather than S. The exact station took place at 26°20’ Gemini.
George III, known colloquially as ‘mad King George,’ developed a peculiar condition that was never accurately diagnosed. Some sources have suggested that the condition was a genetic blood disorder called porphyria. Recent research seems to have virtually ruled out this theory, and it is now thought that he suffered from a type of mania or other psychiatric condition.
One of the key symptoms of his illness was a tendency to talk incessantly. His speech became manic, and he would rave on incoherently, unable to stop himself. His written correspondence also showed this same tendency; sentences would run on and on, as his train of thought became increasingly confused. Towards the close of his life, he talked nonstop for days, not pausing to eat or sleep.
When his illness first surfaced, George himself was of the view that the condition was triggered by his intense grief over the loss of his youngest and beloved daughter, Princess Amelia, who died at the age of 27 on November 2, 1810.
SR Mercury in its own sign describes his inability to stop talking. Note that the Sun and Chiron are also positioned in Gemini, making a total of six planets in the sign of communication. The sextile to Jupiter in Aries would have served to exacerbate this condition.
King George simply had no way out of this compulsion. He was destined to endlessly repeat himself, literally stuck in time. Whether or not it was grief that triggered his condition, by the end of his life he was completely insane — also blind and deaf, suffering from dementia, and unable to walk. George III died in January 1820.
Just as Mars is connected with sports and medicine, Jupiter is associated with actors, playwrights, top executives, military leaders, journalists, and politicians. Gauquelin showed conclusively that this planet is prominent in the charts of individuals engaged in these professions. In terms of character traits, the typical Jupiter type is extroverted, proud, authoritarian, humorous, ambitious, and independent, among other Jovian qualities.
When researching charts that contain a stationary Jupiter, I was interested to discover that these occupations and traits cropped up time and again. In terms of both profession and personality, people born when Jupiter was stationary, or travelling at less than 30% of its average speed, strongly embodied the Jupiter archetype. The list of well-known people below includes a number of evangelists, spiritual leaders, politicians, actors, performers, activists, and other larger-than-life characters. Several people in this list are also given to hubris, another symptom of a hyper-functioning Jupiter.
On first inspection, it seemed that Jupiter was stationary in the charts of entertainers far more often than in randomly selected charts. To test this, I looked at the percentage of people expected to have a slow or stationary Jupiter (using the 30% rule), compared to the entertainers.
Jupiter’s orbit is not too eccentric. Jupiter will be travelling at less than 30% of its average speed for around 15–16 days at each station. Therefore, every synodic cycle of Jupiter (which is 399 days), we would expect to find Jupiter flagged S for about 30 days. This equates to 7.5%–8%.
As I looked through my client database, I created a sample group, a total of 509 charts in all. Jupiter was found to be stationary in 37 of these charts, which is 7.27%. So far, so good. In another control group, I have the birth data of some Mensa members that I collected in the 1980s, which contains 241 individuals. Searching this group for stationary Jupiter, I found 17 charts, which is 7.05%.
However, for entertainers — a group within the Solar Fire database containing a total of 435 charts — there are 42 charts with a stationary Jupiter. This is 9.65%, a higher number than expected by chance. (If it were 7.5%, there would be only 32 charts.) Looking at the Music & Dance database in Solar Fire — which contains many of the same charts as the Entertainment database, but also has a number of additional charts, 294 in all — we find that 32 of these individuals have Jupiter stationary, which is 10.88%. (In this case, the expected number of charts, based on 7.5%, is 22.)
I then combined these groups, deleted any duplicates, and added a few notable performers whose charts I had collected previously, building a file of 678 entertainers, including dancers, musicians, actors, composers, and directors. Charts containing a stationary Jupiter in this larger group totalled 65, or 9.58% — again, above the average.
It’s worth noting that Jupiter stations when making a trine to the Sun. But if you’re calculating charts using the 30% rule, a slow Jupiter will not necessarily be making a trine to the Sun. In some cases where Jupiter is flagged S, the orb of the Jupiter–Sun trine stretches out to 11 degrees, which is generally considered too wide an orb for a trine. In the following list of well-known people with a slow or stationary Jupiter (see Table 6, **), some have a Jupiter–Sun trine and others don’t. This serves to illustrate that it seems to be the slow Jupiter, rather than the Jupiter–Sun trine, that is the key factor in how S Jupiter manifests.
|Spiro Agnew, politician||SR 15°46’ Can|
|Kathleen Battle, opera singer||SD 19°07’ Sag|
|Chuck Berry, musician||SD 17°21’ Aqu|
|Bilawal Bhutto, Pakistani politician||SR 06°07’ Gem|
|Justin Bieber, singer||SR 14°39’ Sco|
|John Wilkes Booth, actor/assassin||SD 08°51’ Vir|
|Marlon Brando, actor/activist||SR 19°54’ Sag|
|Jeff Buckley, musician||SR 04°28’ Leo|
|Dr. Jim Cairns, politician/socialist||SD 12°30’ Aqu|
|Irene Cara, singer/actor||SR 01°59’ Sag|
|Samuel Taylor Coleridge, poet/philosopher||SD 22°48’ Aqu|
|Jimmy Connors, tennis star||SR 20°54’ Tau|
|Tom Cruise, actor/Scientologist||SR 12°41’ Pis|
|Leonardo DiCaprio, actor/environmentalist||SD 08°06’ Pis|
|Melissa Etheridge, singer||SR 07°08’ Aqu|
|Dakota Fanning, actor||SR 14°37’ Sco|
|Greta Garbo, actor||SR 06°25’ Gem|
|Judy Garland, actor/singer||SD 09°00’ Lib|
|Julia Gillard, Australian politician||SD 27°23’ Cap|
|Billy Graham, evangelist||SR 15°48’ Can|
|Xanana Gusmao, East Timorese politician||SD 17°30’ Lib|
|Adolf Hitler, Nazi dictator||SR 08°15’ Cap|
|Whitney Houston, singer/performer||SR 19°29’ Ari|
|John Howard, politician/Prime Minister||SR 08°46’ Ari|
|Robert Hughes, actor/convicted sex offender||SD 19°07’ Sag|
|Dalai Lama XIV, spiritual leader||SD 13°28’ Sco|
|Karl Marx, philosopher/socialist||SR 12°57’ Cap|
|Jim Morrison, musician/singer||SR 27°01’ Leo|
|Wolfgang Amadeus Mozart, composer/musician||SR 18°31’ Lib|
|Rupert Murdoch, media baron||SD 10°29’ Can|
|Aristotle Onassis, shipping magnate||SD 26°28’ Tau|
|Robert Plant, musician/performer||SD 19°08’ Sag|
|Charlotte Rampling, actor||SR 27°19’ Lib|
|Robert Redford, actor/director||SD 14°41’ Sag|
|Keith Richards, musician||SR 27°02’ Leo|
|Peter Sellers, actor||SD 12°41’ Cap|
|George Bernard Shaw, playwright||SR 09°10’ Ari|
|Paul Simon, musician||SR 21°26’ Gem|
|O. J. Simpson, sports champion/actor/criminal||SD 17°45’ Sco|
|Bruce Springsteen, musician/performer||SD 22°23’ Cap|
|Jimmy Swaggart, evangelist||SR 23°15’ Sco|
|Donald Trump, TV personality/politician||SD 17°27’ Lib|
|Tina Turner, singer/performer||SD 28°53’ Pis|
|H. G. Wells, writer/socialist||SD 22°26’ Cap|
Table 6: Well-known people born with stationary Jupiter
While more research needs to be done, these findings tell us that stationary or slow-moving planets are very far from being inert. Perhaps they really are the most powerful planets after all.
Chart Data and Sources
Christopher Reeve, September 25, 1952; 3:12 a.m. EDT; Manhattan, NY, USA (40°N46’, 73°W59’); A: birth certificate in hand, no time; Linda Clark quotes a letter from him with the time. Horseback-riding accident, May 27, 1995; 3:03 p.m. EDT; Culpeper, VA, USA (38°N28’, 78°W00’); source: public record. http://www.penguinrandomhouse.com/books/139937/still-me-by-christopher-reeve/
George III, June 4, 1738 New Style; 7:30 a.m. LMT; London, England (51°N30’, 00°W10’): B: Dana Holliday quotes John Brooke’s 1982 biography, George III, for “between 6:00 and 7:00 a.m.” Lois Rodden quotes Miss Pamela Clark, Deputy Registrar of the Royal Archives, for the same (May 24 Old Style
All other data have been retrieved from various software and Internet sources, including Solar Fire and AstroDatabank (http://www.astro.com), and from my personal research of births and events in the public record. None of the birth dates is in contention. A precise birth time or birthplace is not necessary for ascertaining whether a planet is stationary.
References and Notes
(All URLs were accessed in June 2015.)
2. Deborah Houlding, “An Introduction to Horary Astrology, Part 5: Accidental Strengths and Afflictions,” in TMA, Oct./Nov. 2013, pp. 75–76.
3. Erin Sullivan, Retrograde Planets: Traversing the Inner Landscape, Samuel Weiser, Inc., 1992, 2000, p.125
4. Ibid., p.126
5. Houlding, op. cit., p. 76.
6. All charts shown or cited in this article are calculated using the 30% rule for determining stationary planets. Any planet moving slower than 30% of its average speed is flagged S.
© 2015, 2020 Michele Finey – all rights reserved | 0.845563 | 3.528268 |
The location of four new fast radio bursts -- FRB 180924, FRB 181112, FRB 190102, and FRB 190608 -- have been traced back to galaxies that are still forming new stars at a moderate rate, just like our Milky Way galaxy. Dr Bhandari’s research published in The Astrophysical Jour
The new Moon is extremely tiny, estimated to have a diameter panning a maximum of six meters, and is essentially an asteroid that might be breaking away from the Earth's orbit really soon
Astronomers are testing an idea developed by Albert Einstein about a century ago to resolve a longstanding puzzle over what is driving the accelerated expansion of the universe.
The study suggests that astronomers have a solid chance of doing something that's never been done before: detect a supernova fast enough to witness what happens at the very beginning of a star's demise.
Located 250 light-years away, the star HIP 102152 is more like the Sun than any other solar twin - except that it is nearly four billion years older. This older twin may be host to rocky planets and gives us an unprecedented chance to see how the Sun will look when it ages, researchers said.
Astronomers have found a mini planet beyond our solar system that is the smallest of more than 800 extra-solar planets discovered, scientists said on Wednesday.
Astronomers have discovered the largest known structure in the universe - a group of quasars so large it would take four billion years to cross it while traveling at speed of light.
Astronomers have captured one of the flattest galaxies known in the universe, sitting like a silver needle in the haystack of space. The NASA/ESA Hubble Space Telescope produced a beautiful image of the spiral galaxy IC 2233, one of the flattest galaxies known, the US space agency said.
Astronomers using the Hubble Space Telescope have found seven galaxies that formed relatively shortly after the Universe's birth some 13.7 billion years ago, scientists said on Wednesday, describing them "as baby pictures of the universe."
A large asteroid that flies in nearly the same orbit as Earth will make a close pass by the planet, but there's no chance of an impact - at least for hundreds of years, astronomers said on Wednesday.
Astronomers have uncovered new evidence that suggests that space-borne X-ray detectors could be the first to spot new supernovae signalling ...
An international team of astronomers has produced the first map of the universe as it was 11 billion years ago, filling a gap between the Big Bang and the rapid expansion that followed.
An Anglo-German team of astronomers has discovered a new planet orbiting a nearby sun at just the right distance for an Earth-like climate that could support life
Astronomers have discovered two 'super-luminous' massive stars which exploded 12.5 billion years ago, believed to be the oldest supernovae ever detected.
Planets supporting alien life beyond the solar system will be found within the next 50 years, says renowned astronomer Sir Patrick Moore.
An earth-sized planet has been found orbiting Alpha Centauri, the star nearest to the earth at over four light years away, but which would still take ...
The search for a home, away from home will never end. Even as we continue to live our sheltered lives on ... | 0.900662 | 3.7426 |
If you look low in the western sky just after sunset, you will see three planets in an irregular row: from left to right, Venus, Mars and Saturn. Venus is the brightest of the three and, with the use of a telescope or binoculars, appears as a narrowing crescent.
Venus was at its greatest elongation — its farthest distance from the sun — on Aug. 20. Now it’s rounding the sun and getting closer to Earth. [Photos: Venus Crosses the Sun]
Astronomers use a magnitude scale to measure the brightness of objects in the sky, with larger numbers indicating fainter objects. The brightest objects in the sky are magnitude 1 or less; the faintest objects that can be seen with the naked eye are magnitude 6.
Currently, Venus shines bright at a magnitude –4.4, with Saturn at magnitude 1.0 and Mars slightly fainter at magnitude 1.5.
This sky map shows where to look to spot all three planets tonight, weather permitting.
Just to the left of Venus is the star Spica in the constellation Virgo, like Saturn magnitude 1.0. Riding high above all four is the brighter star Arcturus in Bootes, magnitude –0.1.
Because Venus is lit by the sun from behind, its crescent shape, as seen in a telescope or binoculars, is getting narrower, like a waning crescent moon, as it moves in front of the sun. Any telescope will show the crescent shape, and it is even visible through binoculars.
In this part of Venus' orbit, the view does a balancing act between the planet's decreasing distance from the Earth (which makes it look brighter) and the decreasing width of its crescent (which makes it fainter). The two balance out Sept. 23, when Venus will be its brightest of this year, magnitude –4.6. The planet will then start to drop ever closer to the sun, passing between Earth and the sun on Oct. 29.
Venus will pass just south of the sun at this time. But Venus will pass directly in front of the sun on June 5, 2012. This transit of Venus last occurred June 8, 2004, and won’t happen again until December 2117.
Moving planets in space
Returning to the view tonight, after the three planets in the west have set, turn around and face the east: You will see the moon rising, one day past full, shortly followed by the planet Jupiter to its left.
So, just as three planets exit stage right, a new planet enters stage left.
If you miss these events tonight, try again tomorrow night, but don’t delay any further, as the planets move on without any regard for human observers.
If you’ve been following the movements of the planets over the last few weeks, you will have seen Mars, Saturn and Venus shift from a tight triangle on Aug. 5 — with Mars and Saturn to the left of Venus — to an Aug. 10 arrangement with Venus in the middle.
Mars and Venus were closest, less than 2 degrees apart, on Aug. 18, and have now drawn apart so that the three planets appear in an irregular line. This is about as close as planets ever get to aligning in real life.
For observers in the Northern Hemisphere, Saturn is now getting perilously close to the sun and will soon be lost, reappearing at dawn in November.
- Photos — Venus Crosses the Sun, Part 2
- Telescopes for Beginners
- See Jupiter and the Moon: 6 Degrees of Separation
This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions. | 0.835664 | 3.602995 |
Observations by an international team of astronomers with the UVES spectrometer on ESO’s Very Large Telescope at the Paranal Observatory (Chile) have thrown new light on the earliest epoch of the Milky Way galaxy.
The first-ever measurement of the Beryllium content in two stars in a globular cluster (NGC 6397) – pushing current astronomical technology towards the limit – has made it possible to study the early phase between the formation of the first generation of stars in the Milky Way and that of this stellar cluster. This time interval was found to amount to 200 – 300 million years.
The age of the stars in NGC 6397, as determined by means of stellar evolution models, is 13,400 ? 800 million years. Adding the two time intervals gives the age of the Milky Way, 13,600 ? 800 million years.
The currently best estimate of the age of Universe, as deduced, e.g., from measurements of the Cosmic Microwave Background, is 13,700 million years. The new observations thus indicate that the first generation of stars in the Milky Way galaxy formed soon after the end of the ~200 million-year long “Dark Ages” that succeeded the Big Bang.
The age of the Milky Way
How old is the Milky Way ? When did the first stars in our galaxy ignite ?
A proper understanding of the formation and evolution of the Milky Way system is crucial for our knowledge of the Universe. Nevertheless, the related observations are among the most difficult ones, even with the most powerful telescopes available, as they involve a detailed study of old, remote and mostly faint celestial objects.
Globular clusters and the ages of stars
Modern astro physics is capable of measuring the ages of certain stars, that is the time elapsed since they were formed by condensation in huge interstellar clouds of gas and dust. Some stars are very “young” in astronomical terms, just a few million years old like those in the nearby Orion Nebula. The Sun and its planetary system was formed about 4,560 million years ago, but many other stars formed much earlier. Some of the oldest stars in the Milky Way are found in large stellar clusters, in particular in “globular clusters” (PR Photo 23a/04), so called because of their spheroidal shape.
Stars belonging to a globular cluster were born together, from the same cloud and at the same time. Since stars of different masses evolve at different rates, it is possible to measure the age of globular clusters with a reasonably good accuracy. The oldest ones are found to be more than 13,000 million years old.
Still, those cluster stars were not the first stars to be formed in the Milky Way. We know this, because they contain small amounts of certain chemical elements which must have been synthesized in an earlier generation of massive stars that exploded as supernovae after a short and energetic life. The processed material was deposited in the clouds from which the next generations of stars were made, cf. ESO PR 03/01.
Despite intensive searches, it has until now not been possible to find less massive stars of this first generation that might still be shining today. Hence, we do not know when these first stars were formed. For the time being, we can only say that the Milky Way must be older than the oldest globular cluster stars.
But how much older?
Beryllium to the rescue
What astrophysicists would like to have is therefore a method to measure the time interval between the formation of the first stars in the Milky Way (of which many quickly became supernovae) and the moment when the stars in a globular cluster of known age were formed. The sum of this time interval and the age of those stars would then be the age of the Milky Way.
New observations with the VLT at ESO’s Paranal Observatory have now produced a break-through in this direction. The magic element is “Beryllium”!
Beryllium is one of the lightest elements – the nucleus of the most common and stable isotope (Beryllium-9) consists of four protons and five neutrons. Only hydrogen, helium and lithium are lighter. But while those three were produced during the Big Bang, and while most of the heavier elements were produced later in the interior of stars, Beryllium-9 can only be produced by “cosmic spallation”. That is, by fragmentation of fast-moving heavier nuclei – originating in the mentioned supernovae explosions and referred to as energetic “galactic cosmic rays” – when they collide with light nuclei (mostly protons and alpha particles, i.e. hydrogen and helium nuclei) in the interstellar medium.
Galactic cosmic rays and the Beryllium clock
The galactic cosmic rays travelled all over the early Milky Way, guided by the cosmic magnetic field. The resulting production of Beryllium was quite uniform within the galaxy. The amount of Beryllium increased with time and this is why it might act as a “cosmic clock”.
The longer the time that passed between the formation of the first stars (or, more correctly, their quick demise in supernovae explosions) and the formation of the globular cluster stars, the higher was the Beryllium content in the interstellar medium from which they were formed. Thus, assuming that this Beryllium is preserved in the stellar atmosphere, the more Beryllium is found in such a star, the longer is the time interval between the formation of the first stars and of this star.
The Beryllium may therefore provide us with unique and crucial information about the duration of the early stages of the Milky Way.
A very difficult observation
So far, so good. The theoretical foundations for this dating method were developed during the past three decades and all what is needed is then to measure the Beryllium content in some globular cluster stars.
But this is not as simple as it sounds! The main problem is that Beryllium is destroyed at temperatures above a few million degrees. When a star evolves towards the luminous giant phase, violent motion (convection) sets in, the gas in the upper stellar atmosphere gets into contact with the hot interior gas in which all Beryllium has been destroyed and the initial Beryllium content in the stellar atmosphere is thus significantly diluted. To use the Beryllium clock, it is therefore necessary to measure the content of this element in less massive, less evolved stars in the globular cluster. And these so-called “turn-off (TO) stars” are intrinsically faint.
In fact, the technical problem to overcome is three-fold: First, all globular clusters are quite far away and as the stars to be measured are intrinsically faint, they appear quite faint in the sky. Even in NGC6397, the second closest globular cluster, the TO stars have a visual magnitude of ~16, or 10000 times fainter than the faintest star visible to the unaided eye. Secondly, there are only two Beryllium signatures (spectral lines) visible in the stellar spectrum and as these old stars do contain comparatively little Beryllium, those lines are very weak, especially when compared to neighbouring spectral lines from other elements. And third, the two Beryllium lines are situated in a little explored spectral region at wavelength 313 nm, i.e., in the ultraviolet part of the spectrum that is strongly affected by absorption in the terrestrial atmosphere near the cut-off at 300 nm, below which observations from the ground are no longer possible.
It is thus no wonder that such observations had never been made before, the technical difficulties were simply unsurmountable.
VLT and UVES do the job
Using the high-performance UVES spectrometer on the 8.2-m Kuyen telescope of ESO’s Very Large Telescope at the Paranal Observatory (Chile) which is particularly sensitive to ultraviolet light, a team of ESO and Italian astronomers succeeded in obtaining the first reliable measurements of the Beryllium content in two TO-stars (denoted “A0228” and “A2111”) in the globular cluster NGC 6397 (PR Photo 23b/04). Located at a distance of about 7,200 light-years in the direction of a rich stellar field in the southern constellation Ara, it is one of the two nearest stellar clusters of this type; the other is Messier 4.
The observations were done during several nights in the course of 2003. Totalling more than 10 hours of exposure on each of the 16th-magnitude stars, they pushed the VLT and UVES towards the technical limit. Reflecting on the technological progress, the leader of the team, ESO-astronomer Luca Pasquini, is elated: “Just a few years ago, any observation like this would have been impossible and just remained an astronomer’s dream!”
The resulting spectra (PR Photo 23c/04) of the faint stars show the weak signatures of Beryllium ions (Be II). Comparing the observed spectrum with a series of synthetic spectra with different Beryllium content (in astrophysics: “abundance”) allowed the astronomers to find the best fit and thus to measure the very small amount of Beryllium in these stars: for each Beryllium atom there are about 2,224,000,000,000 hydrogen atoms.
Beryllium lines are also seen in another star of the same type as these stars, HD 218052, cf. PR Photo 23c/04. However, it is not a member of a cluster and its age is by far not as well known as that of the cluster stars. Its Beryllium content is quite similar to that of the cluster stars, indicating that this field star was born at about the same time as the cluster.
From the Big Bang until now
According to the best current spallation theories, the measured amount of Beryllium must have accumulated in the course of 200 – 300 million years. Italian astronomer Daniele Galli, another member of the team, does the calculation: “So now we know that the age of the Milky Way is this much more than the age of that globular cluster – our galaxy must therefore be 13,600 ? 800 million years old. This is the first time we have obtained an independent determination of this fundamental value!”.
Within the given uncertainties, this number also fits very well with the current estimate of the age of the Universe, 13,700 million years, that is the time elapsed since the Big Bang. It thus appears that the first generation of stars in the Milky Way galaxy was formed at about the time the “Dark Ages” ended, now believed to be some 200 million years after the Big Bang.
It would seem that the system in which we live may indeed be one of the “founding” members of the galaxy population in the Universe.
The research presented in this press release is discussed in a paper entitled “Be in turn-off stars of NGC 6397: early Galaxy spallation, cosmochronology and cluster formation” by L. Pasquini and co-authors that will be published in the European research journal “Astronomy & Astrophysics” (astro-ph/0407524).
Original Source: ESO News Release | 0.923889 | 4.092102 |
As far as tourist destinations go, our solar system appears to be fairly low on the universe’s list of best places to visit: Astronomers have only ever detected two interstellar visitors passing through our neighborhood. Even though our visitor count remains low, those two wanderers have given us a glimpse of the truly unusual vagabonds traversing the cosmos. The first —— was so weird .
The second visitor, rogue comet 2I/Borisov,— but new analysis shows our second interstellar visitor is pretty odd, too.
Two studies, published in the journal Nature Astronomy on Monday, examined Borisov using the space-based Hubble Telescope and the ground-based Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. Astronomers were particularly fortunate with Borisov observations because, unlike ‘Oumuamua, it was spotted in the customs line , giving them a chance to observe it.
Hubble and ALMA were pointed at Borisov in December and January as it moved through our corner of space just outside the orbit of Mars. As it got closer to the sun, Borisov warmed up, causing it to expel some of the gases trapped inside. This gave researchers with Hubble and ALMA a chance to study different wavelengths of light emitted by the interstellar visitor and determine what gases it contains.
“This is the first time we’ve ever looked inside a comet from outside our solar system,” said Martin Cordiner, an astrochemist with NASA’s Goddard Flight Center and first author on the paper, in a release. “It is dramatically different from most other comets we’ve seen before.”
Both studies show Borisov is extremely rich in carbon monoxide. It’s not strange to find carbon monoxide in a comet, but the levels seen by Hubble and ALMA are off the charts, measuring about three times higher than comets from our home solar system. Because carbon monoxide only freezes at extremely cold temperatures, the research teams suggest it likely formed at the dark, outer edges of a distant star system before being flung toward us.
Borisov’s story is kind of grim, even for a space rock. In the paper by Dennis Bodewits, professor of physics at Auburn University, and colleagues, the authors speculate that Borisov may have begun its life around an M-type star, one of the most common types of stars in our neck of the woods. The team suggests a giant planet orbiting such a star may have kicked Borisov loose, launching it into the depths of space. From there, it wandered, alone and incredibly cold, for millions of years until physics and fate brought it close enough to our sun for it to heat up and burst to life.
As it streams through our region of space now, more recent notice in The Astronomer’s Telegram shows the secondary fragment is no longer visible. Unfortunately, has prevented a more concerted look at the tourist because many of the major observatories that can still view the comet here on Earth have closed.like a cookie dunked in tea. Recent images of Borisov showed it cracking apart and a small fragment being ejected into space. A
Hubble should be able to track Borisov into 2021, but ground-based telescopes like ALMA will likely lose sight of it in the coming months. While the small window of opportunity to learn more about Borisov is closing, there’s no doubt our solar system will play host to a third rogue tourist some time in the near future — here’s hoping it’s just as weird.
An Asteroid Bigger Than The Empire State Building Poses ‘No Danger’ On Saturday Night, Says NASA – Forbes
A huge near-Earth asteroid will pass our planet tonight at a safe distance of 3.2 million miles, according to NASA.
After a spate of doom-laden headlines the space agency felt the need yesterday to update a previous post about near-Earth asteroids with the following note:
“Asteroid 2002 NN4 will safely pass by the Earth on June 6 at a distance of approximately 3.2 million miles (5.1 million kilometers), about 13 times further away from the Earth than the Moon is. There is no danger the asteroid will hit the Earth.”
Asteroid 2002 NN4’s closest approach to Earth will be at 11:20 p.m. EDT. on Saturday, June 6, 2020.
NASA also tweeted the same advice:
NASA Asteroid Watch then tweeted this image of the asteroid’s trajectory:
How big is Asteroid 2002 NN4?
Asteroid 2002 NN4 is huge. Measuring between 820 feet and 1,870 feet (250 meters to 570 meters) according to Space.com. New York City’s Empire State Building is 443.2 meters tall, including its antenna.
That’s over a dozen times bigger than the asteroid that exploded over Chelyabinsk, Russia, in 2013. That was the biggest meteor for over a century.
Would asteroid 2002 NN4 be dangerous if it hit Earth?
Yes—asteroid 2002 NN4 is city-killer size, but it’s not going to cause any harm to anyone.
Wishing you clear skies and wide eyes.
Crew Dragon with two NASA astronauts docks to ISS – TASS
NEW YORK, May 31. /TASS/. The Crew Dragon spacecraft with Doug Hurley and Bob Behnken on board has successfully docked to the International Space Station (ISS), as follows from a NASA broadcast on Sunday.
The spacecraft began approaching the ISS about two hours before docking than was carried out 10:16 ahead of the schedule. The Crew Dragon spacecraft was launched using the SpaceX Falcon 9 rocket at 22.22 pm Moscow time on May 30 from the Cape Canaveral, Florida.
Crew Dragon is a configuration of the cargo spacecraft Dragon, which had already delivered cargoes to the ISS. A Falcon-9 rocket put the cargo vehicle in space on March 2. Its docking with the ISS was carried out automatically the next day.
NASA stopped crewed flights in 2011 after the Space Shuttle program came to an end. From that moment on all astronauts were delivered to the ISS and back by Russia’s Soyuz spacecraft. Originally the Untied States was to start using commercial spacecraft for crewed missions in 2017.
Toddler could be battling rare syndrome in response to COVID-19 – Winnipeg Free Press
More than a month after testing positive for COVID-19, a Winnipeg toddler is fighting another illness – a possible rare inflammatory syndrome that could be part of the body’s reaction to new viruses.
The girl’s mother told CBC News doctors are trying to find out whether the one-year-old has developed Kawasaki disease, or multi-system inflammatory syndrome in children, now that she is negative for COVID-19 but is still seriously ill.
To read more of this story first reported by CBC News, click here.
The Winnipeg Free Press and CBC Manitoba recognize each other as trusted news sources. This content is made available to our readers as part of an agreement to collaborate to better serve our community. Any questions about CBC content should be directed to: [email protected]
Spurs’ Gregg Popovich: U.S. ‘is in trouble and the basic reason is race’ – Sportsnet.ca
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What is Astrology?
If you live in a city, it is easy to forget how magnificent and marvelous the night sky can be. The few stars that are bright enough to be seen pale in comparison to the sparkling array of manmade lights spanning bridges, climbing buildings, or flashing by on the freeway. But if you are ever lucky enough to be far from civilization on a clear, moonless night, it is easy to understand the fascination and awe that all cultures and all religions have felt toward the celestial wonder of the stars and planets.
Astrology was born from this wonder. It found structure in the cyclic dance of the planets across the skies and meaning from the regularity of the seasons.
There are many misconceptions about astrology.
First, astrology is not the newspaper horoscope. What the majority of people know about astrology is a simplistic offshoot that could be called “what’s your sign.” This got its start in the 1930’s when H.R. Naylor, a British astrologer, published an article in The Sunday Express interpreting Princess Margaret’s chart shortly after her birth. The article was wildly popular and Naylor, knowing a good commercial venture when he saw one, began offering a regular column using interpretations of the Sun in a particular sign. The practice soon spread and now there is scarcely a newspaper or general audience magazine in the Western world that doesn’t have its astrology column. While this type of popular Sun Sign horoscope is fun, it is not very useful.
Even though they share the same names, astrological signs are not the same as the astronomical constellations.
Western geocentric astrologers use tropical (earth-based) calculations to create a chart or a map of the sky viewed from a particular time and place here on earth. This map uses the astrological signs as a coordinate system that begins with the Spring Equinox. Unlike the constellations, each astrological sign is exactly 30 degrees in width. The planets are located in a sign based on their longitude in relation to this astrological zodiac.
The tropical zodiac is based on the relation of the earth to the sun and uses its position to mark:
- the equinoxes when the Sun is directly over the equator
- 0 degrees Aries - the vernal (spring) equinox
- 0 degrees Libra - the autumnal equinox
- and the Soltices, when the Sun is at its most northern and southern points:
- 0 degrees Cancer - the summer equinox for the northern hemisphere
- 0 degrees Capricorn - the winter equinox for the nothern hemisphere
Another misconception is that astrology represents the worship of the stars or the belief that the stars are the architects of our fate, about which nothing can be done. Again, not true. Astrologers believe believe that we can discover a meaningful relationship between the position of the planets at a particular moment of time and ourselves.
How does it work? Why does it work?
Astrologers don't have an agreed upon answer. But they have many of the same questions as critics of astrology. Some questions astrologers ask include:
- Is there a meaningful relationship between living beings here on Earth, the very large environment of our solar system and our visible universe?
- Are inner states influenced by, correlate with, or created by planetary position and relationships?
- Is astrology merely a type of word play that uses a dense set of symbols?
- What parts of astrological interpretation can be measured through research that uses the scientific method?
- Is astrology a type of divination? Is astrology both scientific and divinitory?
- Is prediction in astrology more like a psychological diagnosis, a weather or economic prediction, a psychic prediction, or just an intuitive guess based on the astrologer's understanding of human nature?
Astrologers do not agree on any one answer to these questions. But they do believe that there is value in being aware of the rhythms and cycles of the solar system as reflected here on earth. This proposition does not fit into our current science. While there are a few suggestive research studies, they are not sufficient for the majority of scientists who still automatically dismiss astrology.Different astrologers have proposed different descriptions of how astrology works. Some describe it as a synchronistic activity or that there is a correlation between celestial movement and terrestrial events; some state there is an as yet unknown physical mechanism which creates a relationship between planetary motion and human events; some describe astrology as a divinatory system; and some state that regardless of whether or not there is any reality to astrology, there is a strong psychological value to the use of astrological symbolism.
Psychology and counseling astrology do have common ground. However, psychology attempts to discover the condition of an individual through exposing his/her behavior in relationship with inner states of being; astrology explores an individual by examining his/her life events and circumstances.
Whether you view astrology as a vital, living tradition, or a relic from our past that has no place in modern society, it is inescapable that astrology’s development and symbolism have enriched our culture for over 2,000 years. The development of philosophy, psychology, astronomy, mathematics and science all owe a great debt to astrologers. The symbols of astrology are embedded in much of the world's great literature and art. The meanings of these symbols are embedded in our language. Therefore, regardless of what one believes, there is value in exploring how astrology has been and is being used. | 0.872981 | 3.002099 |
October 5, 2016 – Astronomers have used NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton X-ray observatory to discover an extremely luminous, variable X-ray source located outside the center of its parent galaxy. This peculiar object could be a wandering black hole that came from a small galaxy falling into a larger one.
Astronomers think that supermassive black holes, with some 100,000 to 10 billion times the sun’s mass, are in the centers of most galaxies. There is also evidence for the existence of so-called intermediate mass black holes, which have lower masses ranging between about 100 and 100,000 times that of the sun.
Both of these types of objects may be found away from the center of a galaxy following a collision and merger with another galaxy containing a massive black hole. As the stars, gas and dust from the second galaxy move through the first one, its black hole would move with it.
A new study reports the discovery of one of these “wandering” black holes toward the edge of the lenticular galaxy SDSS J141711.07+522540.8 (or, GJ1417+52 for short), which is located about 4.5 billion light years from Earth. This object, referred to as XJ1417+52, was discovered during long observations of a special region, the so-called Extended Groth Strip, with XMM-Newton and Chandra data obtained between 2000 and 2002. Its extreme brightness makes it likely that it is a black hole with a mass estimated to be about 100,000 times that of the sun, assuming that the radiation force on surrounding matter equals the gravitational force.
The main panel of this graphic has a wide-field, optical light image from the Hubble Space Telescope. The black hole and its host galaxy are located within the box in the upper left. The inset on the left contains Hubble’s close-up view of GJ1417+52. Within this inset the circle shows a point-like source on the northern outskirts of the galaxy that may be associated with XJ1417+52.
The inset on the right is Chandra’s X-ray image of XJ1417+52 in purple, covering the same region as the Hubble close-up. This is a point source, with no evidence seen for extended X-ray emission.
The Chandra and XMM-Newton observations show the X-ray output of XJ1417+52 is so high that astronomers classify this object as a “hyper-luminous X-ray source” (HLX). These are objects that are 10,000 to 100,000 times more luminous in X-rays than stellar black holes, and 10 to 100 times more powerful than ultraluminous X-ray sources, or ULXs.
At its peak XJ1417+52 is about ten times more luminous than the brightest X-ray source ever seen for a wandering black hole. It is also about 10 times more distant than the previous record holder for a wandering black hole.
The bright X-ray emission from this type of black hole comes from material falling toward it. The X-rays from XJ1417+52 reached peak brightness in X-rays between 2000 and 2002. The source was not detected in later Chandra and XMM observations obtained in 2005, 2014 and 2015. Overall, the X-ray brightness of the source has declined by at least a factor of 14 between 2000 and 2015.
The authors theorize that the X-ray outburst seen in 2000 and 2002 occurred when a star passed too close to the black hole and was torn apart by tidal forces. Some of the gaseous debris would have been heated and become bright in X-rays as it fell towards the black hole, causing the spike in emission.
The location and brightness of the optical source in the Hubble image that may be associated with XJ1417+52 suggest that the black hole could have originally belonged to a small galaxy that plowed into the larger GJ1417+52 galaxy, stripping away most of the galaxy’s stars but leaving behind the black hole and its surrounding stars at the center of the small galaxy. If this idea is correct the surrounding stars are what is seen in the Hubble image.
A paper by Dacheng Lin (University of New Hampshire) and colleagues describing this result appears in The Astrophysical Journal and is available online. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations. | 0.829771 | 3.992937 |
Pick of the Pics and Updating Magic Universe
Mirror-image molecules sorted in the Orion Nebula
But Pasteur’s hope for a cosmic driver comes true only locally
A predominance of either left-handed or right-handed versions of molecules is likely within huge dust clouds imaged by Japanese astronomers. The electric field of light rays coming from the clouds corkscrews to the left or corkscrews to the right, with “circular polarization”. The different kinds of clouds are clearly distinguishable in a massive star-forming region within the Orion Nebula, called BN/KL. Yellow denotes left-handed light, and red, right-handed. The largest yellow and red features are about 100 times wider than the Solar System, and the astronomers suggest that the polarized light will favour the formation of left-handed or right-handed molecules. The conspicuous dots left of centre near the bottom are bright young stars of the Trapezium group — strong winds from which have helped the astronomers by blowing away dust that otherwise would obscure the BN/KL region of interest. Credit: Near-infrared (2.14 μm) image with the SIRPOL polarization instrument, NAOJ.
On seeing this report by Tsubasa Fukue and Motohide Tamura of the National Astronomical Observatory of Japan (with colleagues in Japan, UK, Australia and USA) my mind went straight back to Louis Pasteur.
Although immortalized for the germ theory of disease, Pasteur’s initial claim to fame came from a discovery he made as a young student – namely that molecules from living sources have effects on the polarization of light, but the same molecules made synthetically do not. This is the phenomenon of chirality, or handedness. Chemists had to learn to think three-dimensionally about versions of molecules that are mirror images of each other. In the example shown here, every amino acid molecule in living things on Earth is of the left-handed (L) kind.
Molecular handedness is a fundamental feature of life and Pasteur suspected that some fundamental feature of the Universe was responsible for it. The phenomenon has been both a puzzle and a spur for investigators of the origin of life. The fact that carbon compounds in meteorites show the same bias in handedness as that seen on Earth suggests that some physical process was at work throughout the Solar System, at least.
The astronomers now offer an answer. Circularly polarized light pervading the dust cloud in which the Sun and its planets were born would have prompted our molecular bias. The scenario is made convincing by the sheer size of the clouds in Orion possessing one polarity or the other. But it ‘s not the Universe-wide mechanism that Pasteur expected. It seems that if the Solar System had originated in a cloud with the opposite kind of circularly polarized light, all our amino acids would be dextro. | 0.855298 | 3.901626 |
One of the more intriguing issues for the Wide-field Infrared Survey Explorer (WISE) satellite is the question of nearby objects that might be causing problems with the Oort Cloud. Specifically, we’re interested in learning whether an object like the hypothesized ‘Nemesis’ — a tiny companion star to the Sun — or a closer gas giant (‘Tyche’) — might cause disruption to cometary orbits that would create episodes in which more comets than usual make their way into the inner Solar System. Find such an object and you may be able to explain what some have been arguing, that there are periodic variations in the timing of giant impacts, a regular and revealing pattern.
Of course, periodic changes in the frequency of impacts could be caused by something other than a companion star or unknown planet. Another suggested mechanism is the motion of our Solar System through the main plane of the Milky Way, causing the gravitational influence of nearby stars to tug on Oort Cloud comets on a repeated basis. In both cases, we’re wondering whether the age estimates for various craters shows us a pattern, something that tells of impact cycles varying between 13 and 50 million years depending on which theory you look at. Earth would have long periods with few impacts and then a wave of increased impact activity.
Image: Barringer Crater, also known as Meteor Crater, in Arizona. This crater was formed around 50,000 years ago by the impact of a nickel-iron meteorite. Near the top of the image, the visitors center, complete with tour buses on the parking lot, provides a sense of scale. Credit: National Map Seamless Viewer/US Geological Service.
Enter Coryn Bailer-Jones (Max-Planck-Institut für Astronomie), whose new work in Monthly Notices of the Royal Astronomical Society argues that perceived periodic patterns in impact activity are nothing more than a statistical artifact. In other words, the idea that there is an ebb and flow to cometary strikes is not actually found in the data. This does not mean the situation is static. Bailer-Jones says there may be a slight increase in impact events over the past 250 million years under this scenario, but a long-term pattern of periodic variability does not appear in his analysis.
He goes on to argue that the evidence for disruptions of the Oort Cloud relies on a problem with traditional statistical reasoning, saying “There is a tendency for people to find patterns in nature that do not exist. Unfortunately, in certain situations traditional statistics plays to that particular weakness.” The problem, explored in this MPIA news release, is that those studying periodicities in impact crater data have to take into account whether the periodicity they are testing against was derived from their data in the first place or posited independent of observation. If the latter, the argument can be flawed because a bias has been introduced from the outset. That bias operates against the ‘null hypothesis’ against which the periodicities would be measured.
The alternative chosen by Bailer-Jones is to work on the problem through Bayesian statistics, an approach that begins with multiple hypotheses and uses the data to adjust the probabilities for each. I am no statistician, and my hope is that some of the more mathematically inclined of our readers will have a go at the paper to tell me how sound Bailer-Jones’ conclusions are. In any case, the point is that in all the data sets, periodic variation in cratering is disfavored, and the author argues that the craters we see on Earth do not suggest regular waves of impact events:
“From the crater record there is no evidence for Nemesis. What remains is the intriguing question of whether or not impacts have become ever more frequent over the past 250 million years.”
The latter issue is interesting because such an increase in impact rates would, in Bailer-Jones view, make the usual null hypothesis assuming constant impact probability invalid, thus calling into question any study that finds a periodic change in impact events. So instead of periodic variations in impacts, we’re looking at a trend within the past 250 million years of a steady increase in such events. This may in turn be explained by the fact that smaller craters erode more easily, and older craters have more time to erode away. In other words, larger and younger craters are easier to find than smaller, older ones. The question of whether the increase in impact activity is real, then, may have to be resolved by looking at impact craters on the Moon, where there are no natural processes at work that can lead to craters being filled and eroded.
Image: The Nördlinger Ries, or Ries, was formed when a meteor hit the area 15 million years ago. The resulting crater, roughly 20 km in diameter, has since been filled in and eroded. In this natural-colour satellite image, it can just be made out as a circular structure, much less clearly defined than the Barringer Crater, which is significantly younger. Credit: NASA/J. Allen using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.
WISE data should eventually give us the definitive word on large objects in nearby space. Until then, Bailer-Jones’ work is, “Bayesian time series analysis of terrestrial impact cratering,” Monthly Notices of the Royal Astronomical Society, published early online 27 June, 2011 (abstract). | 0.840469 | 3.951209 |
The world is currently going mad for Pokémon Go, so it seems like the perfect time to answer the most burning of scientific questions: what would a black hole Pokémon be like?
Black holes are, well, black. Their gravity is so strong that if you get close enough, nothing, not even light, can escape. I think that’s about as dark as you can get!
After picking Dark as a primary type, I thought Ghost was a good secondary type, since black holes could be thought of as the remains of dead stars. This also fit well with black holes not really being made of anything—they are just warped spacetime—and so are ethereal in nature. Of course, black holes’ properties are grounded in general relativity and not the supernatural.
In the games, having a secondary type has another advantage: Dark types are weak against Fighting types. In reality, punching or kicking a black hole is a Bad Idea™: it will not damage the black hole, but will certainly cause you some difficulties. However, Ghost types are unaffected by Fighting-type moves, so our black hole Pokémon doesn’t have to worry about them.
Height: 0’04″/0.1 m
Real astrophysical black holes are probably a bit too big for Pokémon games. The smallest Pokémon are currently the electric bug Joltik and fairy Flabébé, so I’ve made our black hole Pokémon the same size as these. It should comfortably fit inside a Pokéball.
Measuring the size of a black hole is actually rather tricky, since they curve spacetime. When talking about the size of a black hole, we normally think in terms of the Schwarzschild radius. Named after Karl Schwarzschild, who first calculated the spacetime of a black hole (although he didn’t realise that at the time), the Schwarzschild radius correspond to the event horizon (the point of no return) of a non-spinning black hole. It’s rather tricky to measure the distance to the centre of a black hole, so really the Schwarzschild radius gives an idea of the circumference (the distance around the edge) of the event horizon: this is 2π times the Schwarschild radius. We’ll take the height to really mean twice the Schwarzschild radius (which would be the Schwarzschild diameter, if that were actually a thing).
Weight: 7.5 × 1025 lbs/3.4 × 1025 kg
Although we made our black hole pocket-sized, it is monstrously heavy. The mass is for a black hole of the size we picked, and it is about 6 times that of the Earth. That’s still quite small for a black hole (it’s 3.6 million times less massive than the black hole that formed from GW150914’s coalescence). With this mass, our Pokémon would have a significant effect on the tides as it would quickly suck in the Earth’s oceans. Still, Pokémon doesn’t need to be too realistic.
Our black hole Pokémon would be by far the heaviest Pokémon, despite being one of the smallest. The heaviest Pokémon currently is the continent Pokémon Primal Groudon. This is 2,204.4 lbs/999.7 kg, so about 34,000,000,000,000,000,000,000 times lighter.
Within the games, having such a large weight would make our black hole Pokémon vulnerable to Grass Knot, a move which trips a Pokémon. The heavier the Pokémon, the more it is hurt by the falling over, so the more damage Grass Knot does. In the case of our Pokémon, when it trips it’s not so much that it hits the ground, but that the Earth hits it, so I think it’s fair that this hurts.
Black holes are beautifully simple, they are described just by their mass, spin and electric charge. There’s no other information you can learn about them, so I don’t think there’s any way to give them a gender. I think this is rather fitting as the sun-like Solrock is also genderless, and it seems right that stars and black holes share this.
Sticky Hold prevents a Pokémon’s item from being taken. (I’d expect wild black hole Pokémon to be sometimes found holding Stardust, from stars they have consumed). Due to their strong gravity, it is difficult to remove an object that is orbiting a black hole—a common misconception is that it is impossible to escape the pull of a black hole, this is only true if you cross the event horizon (if you replaced the Sun with a black hole of the same mass, the Earth would happily continue on its orbit as if nothing had happened).
Soundproof is an ability that protects Pokémon from sound-based moves. I picked it as a reference to sonic (or acoustic) black holes. These are black hole analogues—systems which mimic some of the properties of black holes. A sonic black hole can be made in a fluid which flows faster than its speed of sound. When this happens, sound can no longer escape this rapidly flowing region (it just gets swept away), just like light can’t escape from the event horizon or a regular black hole.
Sonic black holes are fun, because you can make them in the lab. You can them use them to study the properties of black holes—there is much excitement about possibly observing the equivalent of Hawking radiation. Predicted by Stephen Hawking (as you might guess), Hawking radiation is emitted by black holes, and could cause them to evaporate away (if they didn’t absorb more than they emit). Hawking radiation has never been observed from proper black holes, as it is very weak. However, finding the equivalent for sonic black holes might be enough to get Hawking his Nobel Prize…
The starting two moves are straightforward. Gravity is the force which governs black holes; it is gravity which pulls material in and causes the collapse of stars. I think Crunch neatly captures the idea of material being squeezed down by intense gravity.
Level 16 — Vacuum Wave
Vacuum Wave sounds like a good description of a gravitational wave: it is a ripple in spacetime. Black holes (at least when in a binary) are great sources of gravitational waves (as GW150914 and GW151226 have shown), so this seems like a sensible move for our Pokémon to learn—although I may be biased. Why at level 16? Because Einstein first predicted gravitational waves from his theory of general relativity in 1916.
Level 18 — Discharge
Black holes can have an electric charge, so our Pokémon should learn an Electric-type move. Charged black holes can have some weird properties. We don’t normally worry about charged black holes for two reasons. First, charged black holes are difficult to make: stuff is usually neutral overall, you don’t get a lot of similarly charged material in one place that can collapse down, and even if you did, it would quickly attract the opposite charge to neutralise itself. Second, if you did manage to make a charged black hole, it would quickly lose its charge: the strong electric and magnetic fields about the black hole would lead to the creation of charged particles that would neutralise the black hole. Discharge seems like a good move to describe this process.
Why level 18? The mathematical description of charged black holes was worked out by Hans Reissner and Gunnar Nordström, the second paper was published in 1918.
Level 19 —Light Screen
In general relativity, gravity bends spacetime. It is this warping that causes objects to move along curved paths (like the Earth orbiting the Sun). Light is affected in the same way and gets deflected by gravity, which is called gravitational lensing. This was the first experimental test of general relativity. In 1919, Arthur Eddington led an expedition to measure the deflection of light around the Sun during a solar eclipse.
Black holes, having strong gravity, can strongly lens light. The graphics from the movie Interstellar illustrate this beautifully. Below you can see how the image of the disc orbiting the black hole is distorted. The back of the disc is visible above and below the black hole! If you look closely, you can also see a bright circle inside the disc, close to the black hole’s event horizon. This is known as the light ring. It is where the path of light gets so bent, that it can orbit around and around the black hole many times. This sounds like a Light Screen to me.
These are three moves which with the most black hole-like names. Dark Void might be “black hole” after a couple of goes through Google Translate. Hyperspace Hole might be a good name for one of the higher dimensional black holes theoreticians like to play around with. (I mean, they like to play with the equations, not actually the black holes, as you’d need more than a pair of safety mittens for that). Shadow Ball captures the idea that a black hole is a three-dimensional volume of space, not just a plug-hole for the Universe. Non-rotating black holes are spherical (rotating ones bulge out at the middle, as I guess many of us do), so “ball” fits well, but they aren’t actually the shadow of anything, so it falls apart there.
I’ve picked the levels to be the masses of the two black holes which inspiralled together to produce GW150914, measured in units of the Sun’s mass, and the mass of the black hole that resulted from their merger. There’s some uncertainty on these measurements, so it would be OK if the moves were learnt a few levels either way.
When gas falls into a black hole, it often spirals around and forms into an accretion disc. You can see an artistic representation of one in the image from Instellar above. The gas swirls around like water going down the drain, making Whirlpool and apt move. As it orbits, the gas closer to the black hole is moving quicker than that further away. Different layers rub against each other, and, just like when you rub your hands together on a cold morning, they heat up. One of the ways we look for black holes is by spotting the X-rays emitted by these hot discs.
As the material spirals into a black hole, it spins it up. If a black hole swallows enough things that were all orbiting the same way, it can end up rotating extremely quickly. Therefore, I thought our black hole Pokémon should learn Rapid Spin as the same time as Whirlpool.
I picked level 63, as the solution for a rotating black hole was worked out by Roy Kerr in 1963. While Schwarzschild found the solution for a non-spinning black hole soon after Einstein worked out the details of general relativity in 1915, and the solution for a charged black hole came just after these, there’s a long gap before Kerr’s breakthrough. It was some quite cunning maths! (The solution for a rotating charged black hole was quickly worked out after this, in 1965).
Level 77 — Hyper Beam
Another cool thing about discs is that they could power jets. As gas sloshes around towards a black hole, magnetic fields can get tangled up. This leads to some of the material to be blasted outwards along the axis of the field. We’ve some immensely powerful jets of material, like the one below, and it’s difficult to imagine anything other than a black hole that could create such high energies! Important work on this was done by Roger Blandford and Roman Znajek in 1977, which is why I picked the level. Hyper Beam is no exaggeration in describing these jets.
After using Hyper Beam, a Pokémon must recharge for a turn. It’s an exhausting move. A similar thing may happen with black holes. If they accrete a lot of stuff, the radiation produced by the infalling material blasts away other gas and dust, cutting off the black hole’s supply of food. Black holes in the centres of galaxies may go through cycles of feeding, with discs forming, blowing away the surrounding material, and then a new disc forming once everything has settled down. This link between the black hole and its environment may explain why we see a trend between the size of supermassive black holes and the properties of their host galaxies.
To finish off, since black holes are warped spacetime, a space move and a time move. Relativity say that space and time are two aspects of the same thing, so these need to be learnt together.
It’s rather tricky to imagine space and time being linked. Wibbly-wobbly, timey-wimey, spacey-wacey stuff gets quickly gets befuddling. If you imagine just two space dimension (forwards/backwards and left/right), then you can see how to change one to the other by just rotating. If you turn to face a different way, you can mix what was left to become forwards, or to become a bit of right and a bit of forwards. Black holes sort of do the same thing with space and time. Normally, we’re used to the fact that we a definitely travelling forwards in time, but if you stray beyond the event horizon of a black hole, you’re definitely travelling towards the centre of the black hole in the same inescapable way. Black holes are the masters when it comes to manipulating space and time.
There we have it, we can now sleep easy knowing what a black hole Pokémon would be like. Well almost, we still need to come up with a name. Something resembling a pun would be traditional. Suggestions are welcome. The next games in the series are Pokémon Sun and Pokémon Moon. Perhaps with this space theme Nintendo might consider a black hole Pokémon too? | 0.804432 | 3.724593 |
When the Mercury Transfer Module of the BepiColombo mission fires its electric propulsion thrusters an ion beam is extracted. This is created through the ionization of xenon propellant, generating the charged particles that can be accelerated further using an electric field.
Together with gravity assist flybys at Earth, Venus and Mercury, the thrust from the ion beam provides the means to travel to the innermost planet.
After escaping the pull of Earth’s gravity with the Ariane 5 launcher, the spacecraft is on an orbit around the Sun. The transfer module then has to use its thrusters to brake against the mighty pull of the Sun’s gravity. It also has to tune the shape of its orbit in order to make a series of nine gravity assist flybys at the planets before finally delivering the mission’s two science spacecraft into Mercury orbit.
This image is an excerpt from a supercomputer simulation that models the flow of plasma around the spacecraft just after the high energy ion beam is switched on. An outline of the composite spacecraft with its extended solar arrays is included for reference.
The simulation tracks the particles in the beam as well as those that diffuse around the spacecraft, which are created by the interaction of the high energy beam ions with the neutral xenon atoms that also flow out of the thruster. It shows the density of the plasma flowing around the spacecraft and its evolution: red represents high density, blue is low density (see animation for detailed scale).
Although the animation is several seconds long it has been slowed down, representing a mere eight milliseconds of real time – the time necessary for the plasma to reach a steady state.
The simulation was performed to demonstrate that the plasma produced by the thruster is not damaging to the spacecraft: its materials, including solar arrays or instruments, for example, or to the electric propulsion system itself. The simulations also confirmed there are no spurious or dangerous charging events.
Inflight measurements will verify the simulation results and help improve ways in which the generated plasma, spacecraft and space environment interactions can be better modelled.
BepiColombo is a joint endeavour between ESA and JAXA. After their seven-year interplanetary journey, the two science orbiters – the Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter – will start their main mission to provide the most in-depth study of mysterious Mercury to date.
The spacecraft begin transferring to Europe’s spaceport in Kourou this week, where an intensive period of preparations will ready the mission for launch later this year.
The simulations were performed by Félicien Filleul as part of ESA’s Young Graduate Trainee programme. | 0.819969 | 3.805325 |
June 20, 2017
Written by Jamie Ludwig
Magnetars are one of the most extreme and mysterious objects in space. They’re surprisingly small, they’re incredibly dense, and, like their name suggests, they pack one heck of a magnetic pull.
Shine on You Crazy Magnetar
The Navy SEAL 40% Rule Can Help You Achieve Mental Toughness
At the final stage of a star’s life, it explodes into a supernova. As it collapses in on itself, it outshines all of its neighbors before fading slowly away. If the living star was big enough, it leaves over a neutron star: a star so dense that, although it can often be the diameter of a small city, a teaspoon of its matter weighs at least a billion tons. Meanwhile, they spin fast—really fast. Hundreds of times per second fast. All this density equates to a really powerful magnetic field — about a trillion times more powerful than Earth’s. But magnetars? Scientists aren’t sure why, but they’re an especially magnetic form of neutron star. Their magnetic fields measure at about 1,000 trillion times that of Earth.
Scientists have been on the search for magnetars since 1979, when a shock of gamma rays (later identified as coming from magnetar SGR 0525-66) pulsed through the solar system, resulting in space equipment disruptions and atmospheric abnormalities. In the decades since, fewer than 25 neutron stars out of about 2,000 across the galaxy have been dubbed magnetars, though a handful of other candidates are pending confirmation. From Earth’s standpoint, that’s a good thing. In 2004, effects from an explosion, or “starquake,” of SGR 1806-20, (50,000 light years away), was powerful enough to impact the Earth. It damaged and disabled satellites, and even partially ionized the planet’s upper atmosphere.
Come Closer, My Dear
All that, and you can understand why magnetars have earned the status of the most powerful magnet that’s been discovered in the universe so far. In fact, a magnetar’s magnetic field is so powerful that even coming within 600 milesof one would destroy your nervous system and change your molecular structure. Just a little bit closer and the gravitational force would literally tear you apart — starting at the atomic level. Good thing the closest one is thousands of light years away. For the time being, scientists will just have to study these magnetic space oddities from afar. | 0.862683 | 3.608922 |
Researchers propose a new way to detect the elusive graviton
(Phys.org) —Among the four fundamental forces of nature, only gravity has not had a basic unit, or quanta, detected. Physicists expect that gravitational force is transmitted by an elementary particle called a graviton, just as the electromagnetic force is carried by the photon.
While there are deep theoretical reasons why gravitons should exist, detecting them may be physically impossible on Earth.
For example, the conventional way of measuring gravitational forces – by bouncing light off a set of mirrors to measure tiny shifts in their separation – would be impossible in the case of gravitons. According to physicist Freeman Dyson, the sensitivity required to detect such a miniscule distance change caused by a graviton requires the mirrors to be so massive and heavy that they'd collapse and form a black hole.
Because of this, some have claimed that measuring a single graviton is hopeless. But what if you used the largest entity you know of – in this case the universe – to search for the telltale effects of gravitons. That is what two physicists are proposing.
In the paper, "Using cosmology to establish the quantization of gravity," published in Physical Review D (Feb. 20, 2014), Lawrence Krauss, a cosmologist at Arizona State University, and Frank Wilczek, a Nobel-prize winning physicist with MIT and ASU, have proposed that measuring minute changes in the cosmic background radiation of the universe could be a pathway of detecting the telltale effects of gravitons.
Krauss and Wilczek suggest that the existence of gravitons, and the quantum nature of gravity, could be proved through some yet-to-be-detected feature of the early universe.
"This may provide, if Freeman Dyson is correct about the fact that terrestrial detectors cannot detect gravitons, the only direct empirical verification of the existence of gravitons," Krauss said. "Moreover, what we find most remarkable is that the universe acts like a detector that is precisely the type that is impossible or impractical to build on Earth."
It is generally believed that in the first fraction of a second after the Big Bang, the universe underwent rapid and dramatic growth during a period called "inflation." If gravitons exist, they would be generated as "quantum fluctuations" during inflation.
Ultimately, these would evolve, as the universe expanded, into classically observable gravitational waves, which stretch space-time along one direction while contracting it along the other direction. This would affect how electromagnetic radiation in the cosmic microwave background (CMB) radiation left behind by the Big Bang is produced, causing it to become polarized. Researchers analyzing results from the European Space Agency's Planck satellite are searching for this "imprint" of inflation in the polarization of the CMB.
Krauss said his and Wilczek's paper combines what already is known with some new wrinkles.
"While the realization that gravitational waves are produced by inflation is not new, and the fact that we can calculate their intensity and that this background might be measured in future polarization measurements of the microwave background is not new, an explicit argument that such a measurement will provide, in principle, an unambiguous and direct confirmation that the gravitational field is quantized is new," he said. "Indeed, it is perhaps the only empirical verification of this very important assumption that we might get in the foreseeable future."
Using a standard analytical tool called dimensional analysis, Wilczek and Krauss show how the generation of gravitational waves during inflation is proportional to the square of Planck's constant, a numerical factor that only arises in quantum theory. That means that the gravitational process that results in the production of these waves is an inherently quantum-mechanical phenomenon.
This implies that finding the fingerprint of gravitational waves in the polarization of CMB will provide evidence that gravitons exist, and it is just a matter of time (and instrument sensitivity) to finding their imprint.
"I'm delighted that dimensional analysis, a simple but profound technique whose virtues I preach to students, supplies clear, clean insight into a subject notorious for its difficulty and obscurity," said Wilczek.
"It is quite possible that the next generation of experiments, in the coming decade or maybe even the Planck satellite, may see this background," Krauss added. | 0.808165 | 3.962134 |
Comet Tempel 1 – Learn About The Comet NASA Smashed Into
High-Speed Hit And Run
Comet Tempel 1 is classified as a short period Jupiter-family comet with a current orbital period of 5.5 years that was first discovered in 1867. Tempel 1 is famous for being the comet that NASA’s Deep Impact deliberately hit with a high-speed impactor in 2005 creating a dramatic burst of dust and gases.
Fast Fun Summary Facts!
- Discovered By: Wilhelm Tempel on 3 April 1867
- Name: Comet 9P/Tempel 1
- Maximum Apparent Magnitude: 11
- Nucleus Size: 6 km (3.73 miles)
- Aphelion: 4.75 AU
- Perihelion: 1.54 AU
- Eccentricity: 0.5096
- Inclination: 10.47°
- Orbital Period: 5.56 years
More Interesting Facts About The Tempel 1 Comet!
- The comet was initially discovered on April 3rd 1867 by Wilhelm Tempel and was determined to be in orbit within the main Asteroid belt and is therefore classified as a periodic Jupiter-family comet; these are comets that have relatively short orbital periods of less than 20 years.
- The faint comet was lost for many years as astronomers did not realize that its interactions with the Planet Jupiter were altering its orbit! Comets like Temple 1 orbiting in the main Asteroid belt near Jupiter tend to have unstable orbits that evolve over time due to perturbations and their outgassing.
- If you want to view Tempel 1 yourself, you’re going to need a decent telescope as it’s quite faint with an apparent magnitude of only 11, much fainter than can be seen with the naked eye.
- Comet Tempel 1 is most famous for being the target of the 370 kg impactor probe deployed from the NASA Deep Impact mission in July 2005 when the comet was near perihelion. The successful impact at 10.2 km/s (which struck with the equivalent kinetic energy of 4.8 tonnes of TNT) meant that Deep Impact became the first spacecraft to impact and excavate material from the surface of a comet.
- The dramatic bright spray of material from the impact was imaged and studied by the main Deep Impact probe, as well as Earth-based and space-based telescopes, to determine the chemical composition of Tempel 1.
- The comet was found to contain a variety of compounds in addition to silicates (which you’d expect of a rocky surface) and water-ice which was ejected from 1 metre below the crust of the surface.
- A follow-up NASA mission called the NExT mission utilizing the existing Stardust spacecraft made a flyby of Tempel 1 in 2011 to image the 150 m (490 ft) crater that Deep Impact had created.
- Interestingly, Tempel 1 will make a close flyby within 0.02 AU of Mars on October 17, 2183. Maybe Human’s will have a base on Mars’ by then to witness that! | 0.817208 | 3.687831 |
When Edwin Hubble devised his now famous "tuning-fork" diagram in 1926, he sought to organize galaxies' many shapes into a sensible, well-ordered sequence.
He realized that spirals sometimes sport a central bar and sometimes do not, and that ellipticals are gigantic star balls — all bulge and no arms. In Hubble's scheme lenticulars represent a hybrid of those types, and all the peculiar-shaped leftovers became known as irregulars.
Yet I'll admit that when I see or hear the word "galaxy," I conjure up a vision of just one of these: an immense, stately spiral of stars like the one shown at lower right. Seasoned observers can rattle off the names of dozens of pinwheels from memory: the Andromeda galaxy, M51 and M101 in Ursa Major, and M74 in Pisces, to name a few. Ellipticals and irregulars rarely come to mind.
Cosmologists spend a lot of time thinking about spiral galaxies too — not to admire their beauty but to figure out how they exist at all. Their very shape indicates a star system that's been stable and largely unperturbed for billions of years. Yet the early universe was hardly a tranquil place. Crowding caused many young galaxies to collide, merge, and tear each other asunder.
So it's a minor miracle (and a topic of considerable debate) how all the spirals we see today managed to endure all that mayhem unscathed. "The formation of spirals is a problem," admits Christopher Conselice, a galaxy specialist at the University of Nottingham. "We don't know how they formed, or how they survive all those mergers."
Now that telescopes can peer to ever-grater distances and thus farther back in time, astronomers are attempting to take a census of the shapes and numbers of galaxies that existed 6 to 8 billion years ago. Using observations from the Sloan Digital Sky Survey and from the Hubble Space Telescope, François Hammer and Rodney Delgado-Serrano (Paris Observatory) led an effort to catalog 116 local galaxies and 148 distant ones, respectively. In effect, they've created two Hubble sequences: one for the present and one for the circumstances 6 billion years ago. Their results appear in two articles just published in the European journal Astronomy & Astrophysics.
Surprisingly, the assorted beasts in the galaxy zoo were very different long ago. Peculiar-shaped irregular galaxies were far more common (52% of the total) and spirals relatively scarce (31%) — just the opposite of what's observed today (10% irregulars, 72% spirals).
Using computer models to trace the role of interstellar gas and rates of star formation during mergers, Hammer and his team conclude that many of the spiral galaxies seen today must have resulted from collisions between irregular systems. They can't prove that spirals arose phoenix-like from the ashes of titanic collisions — the Hubble views don't reveal scads of merging galactic blobs. But the model suggests that spirals were "rebuilt" following particularly gas-rich mergers.
But Tanner and Delgado-Serrano aren't the only ones trying to crack the Hubble sequence. A competing paper, just published in the Monthly Notices of the Royal Astronomical Society, concludes that spirals would not have fared well in the bump-and-grind chaos of the early universe. Instead, argue Andrew Benson (Caltech) and Nick Devereux (Embry-Riddle Aeronautical University), spirals abound today because they managed to escape violent interactions. "The dense galaxy clusters we see today are actually unusual," Benson explains. "The quiet regions of the universe, then and now, are more common than we thought."
The Benson-Devereux computer model, called GALFORM, takes a set of assumed starting conditions and runs it forward through time. In a sense, Benson notes, the more we know about the early universe, the more difficult the modeling becomes. GALFORM incorporates the effects of unseen dark matter (which helps draw galaxies together quickly) and even more perplexing dark energy (which then pushes them apart). The result is a very good (but not perfect) match to the numbers and types of galaxies observed today and at times past.
One hurdle shared by all these models is that we don't yet know the true shapes of the earliest galaxies. Benson points to the celebrated Hubble Deep Field image, for example, in which "they just look like blobs of light" that sometimes appear as weird chains and other shapes that aren't seen now.
Fortunately, a massive new effort — approved just three weeks ago — will use the revamped Hubble Space Telescope to observe the early universe with unprecedented clarity. Led by Sandra Faber (University of California, Santa Cruz) and Harry Ferguson (Space Telescope Science Institute), the Cosmology Survey Multi-Cycle Treasury Program will employ Hubble's new Wide Field Camera 3 to survey some 250,000 galaxies in five regions of the sky. With luck, the resulting views should reveal crucial details about how galaxies looked at least 12 billion years ago. Don't expect results anytime soon, though. Faber and Ferguson don't yet know how much HST time they'll need — but it's at least a 100 orbits' worth!
If you're impatient (or even if you're not), then let me suggest that you join Galaxy Zoo — a "citizen-science" effort to classify ancient galaxies and scan them for supernovas. | 0.867969 | 4.101822 |
A stunning time-lapse video of Earth captured from the International Space Station shows a lightning storm flashing over the U.S. and "possible satellites" orbiting overhead.
The European Space Agency (ESA) created the video using images taken by French astronaut Thomas Pesquet, a member of the Expedition 51 crew on the orbiting complex.
"Time lapse over California with a thunderstorm on the horizon," Pesquet wrote in a caption posted with the video on Flickr. "These time lapses are made on Earth by taking many pictures and playing them one after the other. There are usually around 25 pictures for a second of video." [Photos: Earth's Lightning Seen from Space]
About halfway through the video, you may notice some small, bright objects streaking through the sky. ESA officials told Space.com that these are "probably functioning satellites," though scientists were unable to confirm which satellites they were. "The giveaway is the fact that the lights are not tumbling, which indicates they are actively controlled," ESA communications officer Daniel Scuka said in an email.
ESA's Space Debris Office determined that the objects are most likely not space junk, because "the objects' brightness in the video is consistent with intact objects," officials said. And they're probably not meteors, either, said Detlef Koschny, a scientist in ESA's Space Situational Awareness Program office who studies near-Earth objects.
Koschny explained that a bright meteor burning up in the atmosphere typically has a duration of a second or less, possibly 2 or 3 seconds for larger objects. This movie, however, runs 25 times faster than real time, he said, meaning the objects are bright for several tens of seconds.
The objects' altitude doesn't fit that of meteors, either, he added. "The typical altitude of a meteor is around 80 to 110 kilometers [50 to 68 miles]. This corresponds to the height of the airglow, which is visible curving above the Earth as a brightish band," Koschny said. "These objects are higher, at least 300 km [186 miles]. Meteors would not be visible in that height."
Watching storms from space
When lightning illuminates the sky, it is considered an indication of strong updrafts before or during a thunderstorm, according to the National Weather Service. As air swirls around in a turbulent, stormy atmosphere, the friction generates electrical charges in the clouds. As those charges build up, it leads to electrification and lightning that can be seen both from the ground and in space.
Looking through the windows of the International Space Station (ISS) may seem like a convenient way to monitor storms from space, but astronauts at the orbiting lab don't spend much time storm-watching. Also, their vantage point is limited. The ISS flies roughly 250 miles (400 km) above Earth, and astronauts on board cannot see Earth's north or south poles due to the station's orbit. And because it travels at about 17,500 mph (28,000 km/h), the ISS doesn't stay over the same place for very long.
Last year, however, NASA launched the most powerful lightning mapper yet; it's on the GOES-16 satellite (previously known as GOES-R), which is in geostationary orbit above the Americas. The instrument, called the Geostationary Lightning Mapper (GLM), can view lightning beneath it to a resolution of about 6.2 miles (10 km).GLM beamed back its first photo of lightning from space in March.
Space.com senior producer Steve Spaleta contributed to this report. You can follow Elizabeth Howell @howellspace, or Space.com @Spacedotcom. We're also on Facebook and Google+. Original article on Space.com. | 0.811969 | 3.22376 |
The speedy planet Mercury makes a predawn appearance in the eastern morning sky during late September. Likely the best date to view Mercury is on September 29, 2016 when the moon appears below it as the chart shows above. The chart above shows the pair at about 50 minutes before sunrise as seen from the Chicago area. Find a clear eastern horizon. At this time Mercury appears about 8 degrees above the eastern horizon, immediately above a thin crescent moon.
The cycle begins when Mercury passes between the earth and sun (inferior conjunction) on September 13. It rapidly rises into the morning sky. The chart above shows the rising time of Mercury, the moon, Jupiter and Spica compared to sunrise. Mercury rarely appears in a dark sky. It reaches its greatest separation from the sun (greatest elongation), shown as GEW on the chart, and then descends back into bright twilight until it passes on the far side of the sun at superior conjunction on October 27.
On September 29, the moon rises at about the same time as Mercury and its view in the sky is depicted at the top of this article.
On October 11, Jupiter and Mercury rise at the same time, at the beginning of Nautical twilight, the time when the horizon can be distinguished. This chart shows that they are less than one degree apart. This chart is calculated for 30 minutes before sunrise when the sky is moderately bright. Use binoculars to locate the planets.
Mercury is a difficult planet to locate. At this greatest elongation, it is only 18 degrees west of the sun, yet the angle the plane of the solar system makes with our horizon makes Mercury easily spotted in bright twilight. As the inner most planet, Mercury is always near the sun. The chart above shows Mercury at greatest elongation along with the its imaginary orbit.
The September morning sky provides a view of Mercury and the reappearance of Jupiter after its Epoch Conjunction with Venus.
Our images and charts collections are available here –> http://goo.gl/Sfp1ur | 0.825618 | 3.063251 |
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Calculating the mass of a Black Hole has been a cosmological riddle among the scientists over last two decades. There was an intuition, that a celestial body could be so massive that it can bend space-time in such a manner, that anything, even light could not get an exemption from its gravitational pull. This hypothetical concept was coined in brief by astronomer John Michell in November 1784.
Karl Schwarzschild’s statement
After the development of the GTR (General Theory of Relativity), the experiment shows that light motion gets bent with the influence of gravity. By figuring out a solution (to the Einstein’s field equation) Karl Schwarzschild stated the gravitational field about a point mass and a spherical mass.
With the progression of science and technology, after analyzing the data of gravity waves, detecting with gravity telescopes and from other experiments, and using some relevant theories, scientists inferred a model of a black hole.
Theories related to the creation of black holes
There are many theories related to the creation of black holes. One popular theory is that, after the death of a massive star, the gravitational pull is so massive that it can overcome the radiation pressure and collapse the star according to the Chandrasekhar limit (1.4 solar mass). An argument opposed the theory that, unknown functioning stops the collapse, this theory was somewhat trailed by a white dwarf, whose mass exceeds the Chandrasekhar Limit, could collapse into a neutron star, and it is stable as indicated by Pauli’s exclusion principle. Yet later an estimation arose that, some neutron stars (>3 solar mass), could debacle into the black hole under the Chandrasekhar Limit prediction and also presumes that laws of physics weren’t probably going to violate and shut the process down, for some stars from transforming to black holes.
Predictions indicate that physical information would be disappeared into BH forever, this violates a presumed precept of quantum mechanics. This catastrophe is caused by synchronizing the quantum mechanics and general theory of relativity is called ‘The Blackhole information loss paradox’.
Despite the fact that anything could not emanate from black holes, in numerous hypothetical approach like quantum field hypothesis in bent space-time presumes that few radiations like Hawking Radiation could be possible. The spectrum is identical to a black body spectrum, whose temperature is inversely proportional to its mass. This is near about the order of billionths of a Kelvin of a black hole, which is practically impossible for detection.
Stephen Hawking’s Contribution to BH
Stephen Hawking coined the concept in 1971 that the existing black holes are in lesser mass than the stellar mass. This idea took us to a new level that micro black holes or more precisely quantum mechanical black holes may exist. The quantum mechanical effects perform a vital role in this kind of tiny black holes. The probability of the creation of such quantum primitive black holes, in the immensely dense environment in the primordial universe after the Big Bang through a consecutive phase transition, was nearly quite possible. This may be possible to observe this kind of black holes for cosmologists by detecting the particles, that are
anticipated to exhale by Hawking Radiation.
Calculating the minimum mass of a Theoretical Black Hole
Representing a very simple mathematical calculation, no complications, have a look! To calculate the mass of mass of a black hole using nuclear physics few assumptions needs to be taken.
- Assuming, Escape velocity of a particle in Blackhole > c (speed of light)
- Assuming that the mass-….. | 0.831875 | 4.144268 |
|In 2011, two astrophysicists theorized in the International Journal of Astrobiology that spacefaring civilizations might be engaged in Targeted Asteroid Mining operations between Mars and Jupiter/CREDIT: NASA|
|By Billy Cox
Don’t know about you, but I’m loving those mystery lights on Ceres as NASA’s surveillance probe, Dawn, bears down on the biggest chunk of real estate in the asteroid belt. And not because of the prospects for discovering alien activity – they’re remote, at best – but because of the opportunity to witness, again, the ritual disconnect that characterizes institutional science whenever The Great Taboo legitimately insinuates itself into a news cycle.
Let’s go back a few years when, after half a century of logging zilch in the Great ET Radio Signal Experiment, SETI pioneer Jill Tarter proposed a new name for their endeavors, the Search for Extraterrestrial Technology (SETT). This was a tacit grudging concession that maybe radio astronomers had been working with a flawed model. In 2011, the International Journal of Astrobiology published a paper by astrophysicists Martin Elvis and Duncan Forgan proposing an even more specific tack, that maybe Earthlings ought to consider scanning the asteroid belt for evidence of ET “macro-engineering projects.” Translation: mining operations. Made sense. After all, they noted, asteroids are repositories for raw material like gold, platinum and silver, the kind of stuff you’d likely need to repair or refuel extended planetary missions.
And, as Forgan would hypothesize two years later in the IJA, ET wouldn’t even have to bend the known laws of physics to reach the rocky debris zone between Jupiter and Mars, no matter which part of the Milky Way he/she/it came from. Upon crunching the numbers, Forgan and a mathematician hypothesized that robotic technologies could have mapped this galaxy well below light speeds, in about 10 million years. On the cosmic scale of time, that’s no big deal.
So here’s what’s going on. In 2007, NASA hurls an unmanned vehicle toward the asteroid belt to look for clues to the formation of our solar system. Destination: “dwarf planets” Vesta and Ceres. Dawn enters a 14-month mapping orbit over Vesta in 2011, then moves on toward the bigger prize. In February, as it closes to within 29,000 miles of Ceres, Dawn’s cameras detect something totally off the charts – lights on the surface. Their luminosity doesn’t appear to be significantly affected by different sun angles. Two months and 25,000 miles closer, their intensity is still unblinking. Planetary scientists are stumped; at the Jet Propulsion Lab’s website, PR flacks do a very savvy thing by letting visitors vote on the most likely suspects: “volcano,” “geyser,” “salt deposit,” “ice,” “rock,” and “other.” Wonder what “other” could be. Hmm. Anyway, we’ll get an even better peek by summer’s end, when Dawn dips to within 900 miles of the surface.
No matter what those lights are all about, this sort of suspense is cool. Talk about a teaching opportunity for schools.
Now let’s review some of NASA’s recent headline-grabbing statements. In 2014, given our ongoing exoplanet transiting searches and the impending exploration of more local worlds like Europa, space agency scientists predicted Earthlings will discover ET life within 20 years. That forecast was reiterated just last week at the Astrobiology Science Conference in Chicago. In fact, NASA Associate Administrator for the Science Mission Directorate (there’s a mouthful) and former astronaut John Grunsfeld suggested that ET civilizations might already have detected us, the same way we’re locating and confirming the existence of deep-space planets. Quote:
“We put atmospheric signatures that guarantee someone with a large telescope 20 light years away could detect us. If there is life out there, intelligent life, they’ll know we’re here.”
Left unsaid, what none in that sheltered crowd wants to contemplate: And if they discover us before we discover them, maybe they’re already a lot closer than we think. But of course, there was no room in Chicago for a discussion of UFOs. That would be a little too declasse, like farting in church. Oh, and just to make sure nobody got terribly excited, coverage of last week’s Windy City pow-wow also included a canned statement from NASA chief scientist Ellen Stefan. In April, during a discussion about Mars, she drew distinctions between the discovery of biological life and some other silly alternative like, well, the 2011 peer-reviewed paper’s “targeted asteroid mining” scenario. “We are not talking about little green men,” she insisted. “We are talking about little microbes.”
Stofan could’ve said “intelligent life.” But she went for the gag line instead. Knowing full well how much everybody loves microbes.
Hey, no one wants to look like an idiot as we approach the biggest discovery of all time, wherever that may be. The solution to the Ceres lights will likely fall far short of little green men. But the language we employ as we draw closer to the inevitability doesn’t inspire much confidence; it suggests we’re deeply conflicted in our enthusiasm for confirming The Other. Or at least the people at the top of NASA appear to be. Fortunately, we can console ourselves with the knowledge that science and politics never mix. | 0.8968 | 3.406559 |
"Today is Einstein in every iPhone ?, says lead author Leo Meyer. "The GPS would not work without the theory of relativity." All tests in the solar system have so far passed the theory of relativity. But near a black hole, gravity is much stronger than in our immediate neighborhood. The researchers now want to find out whether the theory of relativity is valid under these extreme conditions.
The two stars S0-102 and S0-2 do not have round but elliptical orbits. If they reach the point with the shortest distance to the black hole on their orbit, the relativistic effects should become measurable, according to the thesis of the researchers. The star S0-2, which was discovered in 1995 and is 15 times as bright as the S0-102 now found, will reach this point in 2018. "If we observe the two stars over an entire cycle, can we first study fundamental physics near a black hole, " says Ghez. The team uses the powerful Keck telescope in Hawaii. With the adaptive optics method, astronomers can hide disturbing distortions through the Earth's atmosphere.
The fact that the two stars in the closer vicinity of a black hole, so to speak, in the death zone, on stable orbits, is surprising at first glance. But perhaps the dark Star Destroyers are less dangerous than previously thought. This is also shown in a recently published study by researchers led by Jay Strader of Michigan State University. They discovered two black holes near the center of the globular cluster M22. So far, astronomers had assumed that in such star clusters only a single black hole can survive. Because the previous research results had suggested that in many globular star clusters, numerous black holes weighing a few solar masses were born. In the course of time, when they sink into the center of the heap due to their mass, they inevitably get in each other's way, it has been said so far. In the end, only one black hole could be left? all others would either be thrown into space or melt together. display
"We searched for a black hole in the middle of the pile, but instead found two at a distance from the center, " says co-author James Miller-Jones of Curtin University in Australia. That means that theory and simulations need to be refined.
Perhaps even more black holes are hidden in the star cluster. Since they are only visible when they are devouring matter, could be stuck to the 100 more copies in the globular cluster, which belongs to the Milky Way. If globular clusters contain such large amounts of black holes, collisions between them could occur much more frequently than previously thought. Astronomers suspect that these gigantic events release gravitational waves? but according to them, detectors on earth have so far searched in vain.Leo Meyer (University of California, Los Angeles) et al .: Science, Vol. 338, p. 84 Jay Strader (Michigan State University) et al .: Nature, Vol. 490, p. 71, doi: 10.1038 / nature11490 © science.de - Ute Kehse | 0.879937 | 3.988275 |
The context at the end of 1965 is in the race to the Moon. The U.S. Ranger robotic reconnaissance program has just ended and its successor Surveyor is preparing. The Soviet equivalent Luna continues at a frantic pace despite the failures. In the technology preparation programs, Gemini is in full swing, while after the almost miraculous success of the Voshkod missions, the Zond and Soyuz programs are falling behind. In this rather unfavourable position, the Soviets decided to restart the efforts. OKB 1, which managed both manned missions and lunar and planetary exploration, was accumulating failures. To focus on the manned race, Sergei Korolev (boss of OKB 1) decides to get rid of robotic exploration programs shortly before his death.
The heavy task of restoring the Soviet coat of arms in this area is attributed to the OKB Lavotchine (formerly OKB 301) who has no experience in space. However its director, Babakine, has extensive experience in missile radar guidance systems which involves for advanced electronic components constraints similar to space probes.
The OKB Lavotckine sets aside mars exploration and begins by building test facilities (centrifuge, autoclave) that are then used to upgrade 4MV probes to make V67s (venera for 1967 window). The results are felt from the first window to Venus in June 1967. Even if a probe is still lost due to the failure of the Molnia launcher. The second (venera 4) is launched correctly. It penetrates violently into the atmosphere and then continues a more gentle descent under a parachute. Contact was eventually lost when the temperature reached 262°C and the pressure of 22 bars could not be known whether it was due to the impact with the ground or to overheating.
The Americans do not devote as much effort to this window and prefer to devote its resources to lunar missions. The JPL retrieved the reserve probe from the Mariner 3 and 4 missions to Mars and named it Mariner 5. It adapts it to Venusian missions by increasing its thermal protection and turning over certain elements such as solar panels. The use of an Atlas-Agena launcher prohibits the carrying of an atmospheric probe, but studying the probe’s signals just before and after its passage behind Venus (and thus passing through its atmosphere) makes it possible to estimate a surface temperature of 430°C.
For the next Venusian window in January 1969, the Soviets resumed a double atmospheric mission as in 1967. V69 (venera for 1969) probes have a reduced parachute to penetrate the atmosphere more quickly. For once the two Molnia launchers are working properly and the Venera 5 and 6 probes penetrate deeper and yield under 26 and 40 bar respectively.
1969 is mainly marked by a Martian window in March. The two superpowers decided to take the opportunity to launch probes with new launchers. The OKB Lavotchkine was preparing two 5-ton M69 (mars for 1969 window) probes launched by the Proton rocket (compared to 1 ton for the probes launched by Molnia). They are both lost as a result of a failure of the launcher’s top stage. On the American side, the second stage Centaur is finally ready and is mounted on a first stage Atlas. This allows the Mariner probes to be increased to 450 kg, double what was feasible with Atlas-Agena. The launches of Mariner 6 and 7 were perfect, and after a hectic transit, they flew over the target at the end of July 1969 and were largely overshadowed by the success of Apollo 11.
Martian efforts continued with the window of May 1971 with the arrival of the orbiters. Mariner 8 and a Soviet probe is lost at launch, but Mariner 9 transmits data into orbit for a year and a half. The Soviet orbiters of Mars 2 and 3 do the same for 9 months each. Soviet probes, heavier thanks to Proton, also carry less fortunate landers. The first crashes on Mars and the second manages to land smoothly in the middle of a global dust storm and loses contact before it has even been able to send a complete image.
The Soviets prepared and launched 4 probes during the July 1973 window that provided only 9 days of in-orbit collection data and no successful landings.
Meanwhile, Venus is rather neglected. The Americans do not send any probes and the Russians continue with old probe models and the Molnia launcher. The windows of August 1970 and March 1972 are particularly similar. Each time, two probes are launched, one of which is lost each time during launch. The surviving 1970 probe that became Venera 7 reaches Venus and continues to transmit data to the surface. But communication becomes weak on the surface and for 20 minutes, only the temperature 475°C is transmitted to the Earth. In 1972, Venera 8 followed the same profile, but managed to maintain a stable connection from the surface. This is enough to confirm a temperature of 470°C and a pressure of 90 bars.
The Venusian window of November 1973, is not used by the Soviets. The only probe launched is Mariner 10, the last of the program. Launched by an Atlas-Centaur, it flies over Venus but mainly has the role of performing 3 flybys of Mercury, the last yet unexplored telluric planet. | 0.847368 | 3.211073 |
The Dark Side of the Matter
Written by: Gabrijela Zaharijas
Only a small fraction of the total mass of the Universe is formed by known particles (baryonic matter and neutrinos), while the rest is composed of dark matter – 25 percent of the total energy density of the Universe. This makes dark matter an integral part of the so-called Lambda CDM Cosmological Model, which is what scientists use to describe the nature of the Universe according to its age, rate of expansion, history and contents.
The existence of dark matter was first indicated in the 1930s when Swiss astrophysicist Fritz Zwicky found an anomaly as he was attempting to estimate the mass of large galaxy clusters using velocity measurements of individual galaxies within those clusters. He found the observed velocities were surprisingly high and postulated that the galaxies must be subject to a gravitational field much stronger than the one simply created by the mass of the observed systems and, thus, that the extra mass was the result of some form of unobserved “dark” type of matter. It took many scientists and 40 years to confirm these predictions, when American astrophysicist Vera Rubin provided robust observational evidences of the discrepancy between the predicted and observed rotational motion of stars in galaxies. Consequently, we now know that all galaxies sit at the centres of dark matter “halos,” characterized by a large central density but extending far beyond the visible galaxy’s size.
While this and many more recent observations tell us that dark matter exists, its nature remains one of the greatest mysteries in science.
The dark matter mystery
While the Standard Model of particle physics can explain the known particles and forces in the Universe, it cannot explain the existence of the ever-mysterious dark matter. It turns out that none of the particles that make up the Standard Model can completely satisfy the properties of dark matter as is required by cosmological observations. This gap implies that the Standard Model is incomplete and that the solution to the dark matter puzzle may be the link to other unsolved problems in particle physics, so its study could result in a significant breakthrough in our fundamental understanding of nature.
Long-standing candidates for dark matter particles are the so-called Weakly Interacting Massive Particles or WIMPs. WIMPs appeared as a perfect dark matter candidate: theoretical particles with a mass of 100 -1000 times the mass of a proton (100 GeV – 1 TeV, approximately), which would naturally be produced with the right abundance in the early Universe. WIMPs, however, are far from being the only candidate. The wide range of proposed candidates spans about 40 orders of magnitude in mass: from extremely light but theoretically well-motivated particles like “axions“ over the much heavier “WIMPZillas” to macroscopic objects such as primordial black holes.
Hunting dark matter with CTA and gamma rays
Gravity led to the discovery of dark matter’s existence, and it is still the only force known by which dark matter particles interact. However, if the dark matter particle is to complete the Standard Model of fundamental particles, the hope is that it will also be able to interact with other known particles, which could provide another opportunity for detection.
Over the past few decades, the scientific community joined forces and devised a clear three-pronged strategy to (initially) search for WIMPs: via their production in particle collisions (like in the Large Hadron Collider in Geneva), via their scattering with Standard Model particles in dedicated detectors (called “direct detection” experiments) and through astrophysical observations. The main idea of the latter is that, in regions of the Universe where the dark matter density is high, dark matter particles could self-annihilate or decay, producing Standard Model particles that would reach us in the form of cosmic rays, as well as gamma rays.
Thus, there is no doubt that CTA will act as a powerful dark matter discovery instrument: CTA will detect very high-energy gamma rays, a promising means to search for dark matter as gamma rays travel in straight lines (as opposed to charged cosmic rays) and are easier to capture than neutrinos. In particular, CTA will use its unprecedented sensitivity and energy resolution to capture gamma rays exactly over the energy range that corresponds to the heavier end of the WIMP masses.
A variety of experiments over the past few decades have explored and excluded a significant fraction of the lighter WIMP candidates. However, while current instruments are not sensitive enough to detect some of the best-motivated WIMP models, their signals may be lurking exactly in CTA’s optimal energy range. In particular, in an upcoming CTA Consortium publication, CTA scientists demonstrate that the data from the planned survey of the Galactic Centre, where the density of dark matter is expected to be the highest, together with modern analysis techniques, will enable CTA to explore the “Holy Grail” region of the WIMP scenario in detail for the first time in an unrivaled way (see Figure 1).
Figure 1: Main frame: Artist’s view of the CTA-South array with the view of the Milky Way plane and the Galactic center. Overlaid in violet is a prediction, from computer simulations, for how the dark matter gamma-ray signal might look. Inset: The plot showing the dark matter interaction cross section (y-axis) vs the dark matter particle mass (x-axis). The blue horizontal line marks the region where the WIMP dark matter signal is expected to be. While light WIMPs (left part of the x-axis) are already excluded, the heavier WIMPs will be probed by CTA (CTA sensitivity shown with black lines). Credit: C. Eckner; Rendering: Gabriel Pérez Díaz (IAC), Marc-André Besel (CTAO); Simulations and inset: CTA Consortium.
Beyond WIMPs, another pending publication will look at the major role CTA will also play in exploring currently inaccessible aspects of axion-like particle dark matter models. Moreover, unlike current ground-based gamma-ray instruments, CTA will use three different types of telescopes (the Large-, Medium- and Small-Sized Telescopes) that will expand the energy range from 20 GeV up to 300 TeV. This, along with its better 10 percent energy resolution, will maximize CTA’s opportunities to detect spectral features associated with the interaction of dark matter particles of unexpected sources.
The potential CTA brings to the hunt for dark matter is clear: it will exponentially increase our chances of solving the mystery behind dark matter in the next decade, and it could very well hold the key to unveiling completely unimagined discoveries in the field of fundamental physics. | 0.80151 | 4.234611 |
Artist’s animation of the triple system with the closest black hole
This animation shows the orbits and movements of the objects in the HR 6819 triple system. This system includes an inner binary with one star (orbit indicated in blue) and a newly discovered black hole (orbit indicated in red). As we move away from this inner pair, we see the outer object in the system, another star in a much wider orbit (in blue).
The team originally believed there were only two objects, the two stars, in the system. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole, the closest ever found to Earth. The black hole is invisible, but it makes its presence known by its gravitational pull, which forces the luminous inner star into an orbit. The objects in this inner pair have roughly the same mass and circular orbits.
The observations, with the FEROS spectrograph on the 2.2-metre telescope at La Silla, showed that the inner visible star orbits the black hole every 40 days, while the second star is at a large distance from this inner pair.Credit:
About the Video
|Release date:||6 May 2020, 14:00|
|Frame rate:||25 fps| | 0.839268 | 3.15349 |
Probably, but we’re unlikely to visit aliens any time soon.
The only known life in the Universe in on Earth.
But just because we haven’t discovered other life doesn’t mean it isn’t there. If you consider the seven characteristics of life, combined with the infinite space around us, there is probably life somewhere else.
As Neil deGrasse Tyson says: “Most astrophysicists accept a high probability of there being life elsewhere in the Universe, if not on other planets or on moons within our own solar system.”
Mars, our nearest celestial neighbour, is the most likely home of living species in the Solar System. Its weather and yearly cycles are closest to our own, although it is currently in an ice age.
In 2008 the NASA probe Phoenix found evidence of the long-suspected lakes of ice under the polar caps of Mars. Where there is ice, there could once have been liquid water, which may have supported life.
Sadly, with the planet experiencing a winter that would have Jon Snow and his Night’s Watch buddies reaching for extra thermals, it has not so far been possible to tell if any organisms exist within the ice.
The European Space Agency Is also looking for signs of life on one of Jupiter’s icy moons.
Other – perhaps more likely – candidates are out there… far further out there.
NASA has found an Earth-size planet orbiting in the “habitable zone” of another star. Unfortunately the catchily named Kepler-186f is about 500 light years away, so our chance of having a pint of beer with the Kelper-186f-ites seems slim for now.
Another planet, Kepler-452b, has been dubbed “Earth 2.0” – but this one is 1,400 light years away.
And this is where the main problem lies.
Instead of fantasising about a “First Contact” scenario in the near future, we need to overcome the issue of travelling the massive distances to other planets. After all, man (if you exclude Tom Cruise) has only set foot and Earth and the Moon so far.
The main problems are highlighted by NASA as “Grand Challenges”, which include finding better ways to power space travel and avoiding debris.
Surviving the conditions out in the big dark yonder is also tricky. The physical and mental effects of space travel include bone and muscle atrophy, sleep deprivation, disease and depression. This explains why in most deep space science fiction films, somebody goes bananas and tries to kill the rest of the crew.
But people are working on it.
NASA’s primary function is “to reach for new heights and reveal the unknown so that what we do and learn will benefit all humankind”. So they’re on the case.
And we’ve got our eyes and ears open for aliens coming to us. Professor Stephen Hawking has started a 10-year project to listen for broadcast signals from a million of the stars closest to Earth.
So while we may not be chin-wagging with ET, Jabba the Hutt and Commander Worf just yet, there are people trying to break the barriers holding us back. | 0.856598 | 3.127466 |
Atmosphere of Jupiter
The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System. It is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide and water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low. The nitrogen, sulfur, and noble gas abundances in Jupiter's atmosphere exceed solar values by a factor of about three.
The atmosphere of Jupiter lacks a clear lower boundary and gradually transitions into the liquid interior of the planet. From lowest to highest, the atmospheric layers are the troposphere, stratosphere, thermosphere and exosphere. Each layer has characteristic temperature gradients. The lowest layer, the troposphere, has a complicated system of clouds and hazes, comprising layers of ammonia, ammonium hydrosulfide and water. The upper ammonia clouds visible at Jupiter's surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful zonal atmospheric flows (winds) known as jets. The bands alternate in color: the dark bands are called belts, while light ones are called zones. Zones, which are colder than belts, correspond to upwellings, while belts mark descending gas. The zones' lighter color is believed to result from ammonia ice; what gives the belts their darker colors is uncertain. The origins of the banded structure and jets are not well understood, though a "shallow model" and a "deep model" exist.
The Jovian atmosphere shows a wide range of active phenomena, including band instabilities, vortices (cyclones and anticyclones), storms and lightning. The vortices reveal themselves as large red, white or brown spots (ovals). The largest two spots are the Great Red Spot (GRS) and Oval BA, which is also red. These two and most of the other large spots are anticyclonic. Smaller anticyclones tend to be white. Vortices are thought to be relatively shallow structures with depths not exceeding several hundred kilometers. Located in the southern hemisphere, the GRS is the largest known vortex in the Solar System. It could engulf two or three Earths and has existed for at least three hundred years. Oval BA, south of GRS, is a red spot a third the size of GRS that formed in 2000 from the merging of three white ovals.
Jupiter has powerful storms, often accompanied by lightning strikes. The storms are a result of moist convection in the atmosphere connected to the evaporation and condensation of water. They are sites of strong upward motion of the air, which leads to the formation of bright and dense clouds. The storms form mainly in belt regions. The lightning strikes on Jupiter are hundreds of times more powerful than those seen on Earth, and are assumed to be associated with the water clouds.
The atmosphere of Jupiter is classified into four layers, by increasing altitude: the troposphere, stratosphere, thermosphere and exosphere. Unlike the Earth's atmosphere, Jupiter's lacks a mesosphere. Jupiter does not have a solid surface, and the lowest atmospheric layer, the troposphere, smoothly transitions into the planet's fluid interior. This is a result of having temperatures and the pressures well above those of the critical points for hydrogen and helium, meaning that there is no sharp boundary between gas and liquid phases. Hydrogen becomes a supercritical fluid at a pressure of around 12 bar.
Since the lower boundary of the atmosphere is ill-defined, the pressure level of 10 bars, at an altitude of about 90 km below 1 bar with a temperature of around 340 K, is commonly treated as the base of the troposphere. In scientific literature, the 1 bar pressure level is usually chosen as a zero point for altitudes—a "surface" of Jupiter. As with Earth, the top atmospheric layer, the exosphere, does not have a well defined upper boundary. The density gradually decreases until it smoothly transitions into the interplanetary medium approximately 5,000 km above the "surface".
The vertical temperature gradients in the Jovian atmosphere are similar to those of the atmosphere of Earth. The temperature of the troposphere decreases with height until it reaches a minimum at the tropopause, which is the boundary between the troposphere and stratosphere. On Jupiter, the tropopause is approximately 50 km above the visible clouds (or 1 bar level), where the pressure and temperature are about 0.1 bar and 110 K. In the stratosphere, the temperatures rise to about 200 K at the transition into the thermosphere, at an altitude and pressure of around 320 km and 1 μbar. In the thermosphere, temperatures continue to rise, eventually reaching 1000 K at about 1000 km, where pressure is about 1 nbar.
Jupiter's troposphere contains a complicated cloud structure. The upper clouds, located in the pressure range 0.6–0.9 bar, are made of ammonia ice. Below these ammonia ice clouds, denser clouds made of ammonium hydrosulfide ((NH4)SH) or ammonium sulfide ((NH4)2S, between 1–2 bar) and water (3–7 bar) are thought to exist. There are no methane clouds as the temperatures are too high for it to condense. The water clouds form the densest layer of clouds and have the strongest influence on the dynamics of the atmosphere. This is a result of the higher condensation heat of water and higher water abundance as compared to the ammonia and hydrogen sulfide (oxygen is a more abundant chemical element than either nitrogen or sulfur). Various tropospheric (at 200–500 mbar) and stratospheric (at 10–100 mbar) haze layers reside above the main cloud layers. The latter are made from condensed heavy polycyclic aromatic hydrocarbons or hydrazine, which are generated in the upper stratosphere (1–100 μbar) from methane under the influence of the solar ultraviolet radiation (UV). The methane abundance relative to molecular hydrogen in the stratosphere is about 10−4, while the abundance ratio of other light hydrocarbons, like ethane and acetylene, to molecular hydrogen is about 10−6.
Jupiter's thermosphere is located at pressures lower than 1 μbar and demonstrates such phenomena as airglow, polar aurorae and X-ray emissions. Within it lie layers of increased electron and ion density that form the ionosphere. The high temperatures prevalent in the thermosphere (800–1000 K) have not been fully explained yet; existing models predict a temperature no higher than about 400 K. They may be caused by absorption of high-energy solar radiation (UV or X-ray), by heating from the charged particles precipitating from the Jovian magnetosphere, or by dissipation of upward-propagating gravity waves. The thermosphere and exosphere at the poles and at low latitudes emit X-rays, which were first observed by the Einstein Observatory in 1983. The energetic particles coming from Jupiter's magnetosphere create bright auroral ovals, which encircle the poles. Unlike their terrestrial analogs, which appear only during magnetic storms, aurorae are permanent features of Jupiter's atmosphere. The thermosphere was the first place outside the Earth where the trihydrogen cation (H+
3) was discovered. This ion emits strongly in the mid-infrared part of the spectrum, at wavelengths between 3 and 5 μm; this is the main cooling mechanism of the thermosphere.
|He/H||0.0975||0.807 ± 0.02|
|Ne/H||1.23 × 10−4||0.10 ± 0.01|
|Ar/H||3.62 × 10−6||2.5 ± 0.5|
|Kr/H||1.61 × 10−9||2.7 ± 0.5|
|Xe/H||1.68 × 10−10||2.6 ± 0.5|
|C/H||3.62 × 10−4||2.9 ± 0.5|
|N/H||1.12 × 10−4||3.6 ± 0.5 (8 bar)
3.2 ± 1.4 (9–12 bar)
|O/H||8.51 × 10−4||0.033 ± 0.015 (12 bar)
0.19–0.58 (19 bar)
|P/H||3.73 × 10−7||0.82|
|S/H||1.62 × 10−5||2.5 ± 0.15|
|13C/12C||0.011||0.0108 ± 0.0005|
|15N/14N||<2.8 × 10−3||2.3 ± 0.3 × 10−3
|36Ar/38Ar||5.77 ± 0.08||5.6 ± 0.25|
|20Ne/22Ne||13.81 ± 0.08||13 ± 2|
|3He/4He||1.5 ± 0.3 × 10−4||1.66 ± 0.05 × 10−4|
|D/H||3.0 ± 0.17 × 10−5||2.25 ± 0.35 × 10−5|
The composition of Jupiter's atmosphere is similar to that of the planet as a whole. Jupiter's atmosphere is the most comprehensively understood of those of all the gas giants because it was observed directly by the Galileo atmospheric probe when it entered the Jovian atmosphere on December 7, 1995. Other sources of information about Jupiter's atmospheric composition include the Infrared Space Observatory (ISO), the Galileo and Cassini orbiters, and Earth-based observations.
The two main constituents of the Jovian atmosphere are molecular hydrogen (H
2) and helium. The helium abundance is 0.157 ± 0.004 relative to molecular hydrogen by number of molecules, and its mass fraction is 0.234 ± 0.005, which is slightly lower than the Solar System's primordial value. The reason for this low abundance is not entirely understood, but some of the helium may have condensed into the core of Jupiter. This condensation is likely to be in the form of helium rain: as hydrogen turns into the metallic state at depths of more than 10,000 km, helium separates from it forming droplets which, being denser than the metallic hydrogen, descend towards the core. This can also explain the severe depletion of neon (see Table), an element that easily dissolves in helium droplets and would be transported in them towards the core as well.
The atmosphere contains various simple compounds such as water, methane (CH4), hydrogen sulfide (H2S), ammonia (NH3) and phosphine (PH3). Their abundances in the deep (below 10 bar) troposphere imply that the atmosphere of Jupiter is enriched in the elements carbon, nitrogen, sulfur and possibly oxygen[b] by factor of 2–4 relative to the Sun.[c] The noble gases argon, krypton and xenon also appear in abundance relative to solar levels (see table), while neon is scarcer. Other chemical compounds such as arsine (AsH3) and germane (GeH4) are present only in trace amounts. The upper atmosphere of Jupiter contains small amounts of simple hydrocarbons such as ethane, acetylene, and diacetylene, which form from methane under the influence of the solar ultraviolet radiation and charged particles coming from Jupiter's magnetosphere. The carbon dioxide, carbon monoxide and water present in the upper atmosphere are thought to originate from impacting comets, such as Shoemaker-Levy 9. The water cannot come from the troposphere because the cold tropopause acts like a cold trap, effectively preventing water from rising to the stratosphere (see Vertical structure above).
Earth- and spacecraft-based measurements have led to improved knowledge of the isotopic ratios in Jupiter's atmosphere. As of July 2003, the accepted value for the deuterium abundance is (2.25 ± 0.35) × 10−5, which probably represents the primordial value in the protosolar nebula that gave birth to the Solar System. The ratio of nitrogen isotopes in the Jovian atmosphere, 15N to 14N, is 2.3 × 10−3, a third lower than that in the Earth's atmosphere (3.5 × 10−3). The latter discovery is especially significant since the previous theories of Solar System formation considered the terrestrial value for the ratio of nitrogen isotopes to be primordial.
Zones, belts and jets
The visible surface of Jupiter is divided into several bands parallel to the equator. There are two types of bands: lightly colored zones and relatively dark belts. The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. Above and below the EZ, the North and South Equatorial belts (NEB and SEB) extend to 18°N and 18°S, respectively. Farther from the equator lie the North and South Tropical zones (NtrZ and STrZ). The alternating pattern of belts and zones continues until the polar regions at approximately 50 degrees latitude, where their visible appearance becomes somewhat muted. The basic belt-zone structure probably extends well towards the poles, reaching at least to 80° North or South.
The difference in the appearance between zones and belts is caused by differences in the opacity of the clouds. Ammonia concentration is higher in zones, which leads to the appearance of denser clouds of ammonia ice at higher altitudes, which in turn leads to their lighter color. On the other hand, in belts clouds are thinner and are located at lower altitudes. The upper troposphere is colder in zones and warmer in belts. The exact nature of chemicals that make Jovian zones and bands so colorful is not known, but they may include complicated compounds of sulfur, phosphorus and carbon.
The Jovian bands are bounded by zonal atmospheric flows (winds), called jets. The eastward (prograde) jets are found at the transition from zones to belts (going away from the equator), whereas westward (retrograde) jets mark the transition from belts to zones. Such flow velocity patterns mean that the zonal winds decrease in belts and increase in zones from the equator to the pole. Therefore, wind shear in belts is cyclonic, while in zones it is anticyclonic. The EZ is an exception to this rule, showing a strong eastward (prograde) jet and has a local minimum of the wind speed exactly at the equator. The jet speeds are high on Jupiter, reaching more than 100 m/s. These speeds correspond to ammonia clouds located in the pressure range 0.7–1 bar. The prograde jets are generally more powerful than the retrograde jets. The vertical extent of jets is not known. They decay over two to three scale heights[a] above the clouds, while below the cloud level, winds increase slightly and then remain constant down to at least 22 bar—the maximum operational depth reached by the Galileo Probe.
The origin of Jupiter's banded structure is not completely clear, though it may be similar to that driving the Earth's Hadley cells. The simplest interpretation is that zones are sites of atmospheric upwelling, whereas belts are manifestations of downwelling. When air enriched in ammonia rises in zones, it expands and cools, forming high and dense clouds. In belts, however, the air descends, warming adiabatically as in a convergence zone on Earth, and white ammonia clouds evaporate, revealing lower, darker clouds. The location and width of bands, speed and location of jets on Jupiter are remarkably stable, having changed only slightly between 1980 and 2000. One example of change is a decrease of the speed of the strongest eastward jet located at the boundary between the North Tropical zone and North Temperate belts at 23°N. However bands vary in coloration and intensity over time (see below). These variations were first observed in the early seventeenth century.
The belts and zones that divide Jupiter's atmosphere each have their own names and unique characteristics. They begin below the North and South Polar Regions, which extend from the poles to roughly 40–48° N/S. These bluish-gray regions are usually featureless.
The North North Temperate Region rarely shows more detail than the polar regions, due to limb darkening, foreshortening, and the general diffuseness of features. However, the North-North Temperate Belt (NNTB) is the northernmost distinct belt, though it occasionally disappears. Disturbances tend to be minor and short-lived. The North-North Temperate Zone (NNTZ) is perhaps more prominent, but also generally quiet. Other minor belts and zones in the region are occasionally observed.
The North Temperate Region is part of a latitudinal region easily observable from Earth, and thus has a superb record of observation. It also features the strongest prograde jet stream on the planet—a westerly current that forms the southern boundary of the North Temperate Belt (NTB). The NTB fades roughly once a decade (this was the case during the Voyager encounters), making the North Temperate Zone (NTZ) apparently merge into the North Tropical Zone (NTropZ). Other times, the NTZ is divided by a narrow belt into northern and southern components.
The North Tropical Region is composed of the NTropZ and the North Equatorial Belt (NEB). The NTropZ is generally stable in coloration, changing in tint only in tandem with activity on the NTB's southern jet stream. Like the NTZ, it too is sometimes divided by a narrow band, the NTropB. On rare occasions, the southern NTropZ plays host to "Little Red Spots". As the name suggests, these are northern equivalents of the Great Red Spot. Unlike the GRS, they tend to occur in pairs and are always short-lived, lasting a year on average; one was present during the Pioneer 10 encounter.
The NEB is one of the most active belts on the planet. It is characterized by anticyclonic white ovals and cyclonic "barges" (also known as "brown ovals"), with the former usually forming farther north than the latter; as in the NTropZ, most of these features are relatively short-lived. Like the South Equatorial Belt (SEB), the NEB has sometimes dramatically faded and "revived". The timescale of these changes is about 25 years.
The Equatorial Region (EZ) is one of the most stable regions of the planet, in latitude and in activity. The northern edge of the EZ hosts spectacular plumes that trail southwest from the NEB, which are bounded by dark, warm (in infrared) features known as festoons (hot spots). Though the southern boundary of the EZ is usually quiescent, observations from the late 19th into the early 20th century show that this pattern was then reversed relative to today. The EZ varies considerably in coloration, from pale to an ochre, or even coppery hue; it is occasionally divided by an Equatorial Band (EB). Features in the EZ move roughly 390 km/h relative to the other latitudes.
The South Tropical Region includes the South Equatorial Belt (SEB) and the South Tropical Zone. It is by far the most active region on the planet, as it is home to its strongest retrograde jet stream. The SEB is usually the broadest, darkest belt on Jupiter; it is sometimes split by a zone (the SEBZ), and can fade entirely every 3 to 15 years before reappearing in what is known as an SEB Revival cycle. A period of weeks or months following the belt's disappearance, a white spot forms and erupts dark brownish material which is stretched into a new belt by Jupiter's winds. The belt most recently disappeared in May 2010. Another characteristic of the SEB is a long train of cyclonic disturbances following the Great Red Spot. Like the NTropZ, the STropZ is one of the most prominent zones on the planet; not only does it contain the GRS, but it is occasionally rent by a South Tropical Disturbance (STropD), a division of the zone that can be very long-lived; the most famous one lasted from 1901 to 1939.
The South Temperate Region, or South Temperate Belt (STB), is yet another dark, prominent belt, more so than the NTB; until March 2000, its most famous features were the long-lived white ovals BC, DE, and FA, which have since merged to form Oval BA ("Red Jr."). The ovals were part of South Temperate Zone, but they extended into STB partially blocking it. The STB has occasionally faded, apparently due to complex interactions between the white ovals and the GRS. The appearance of the South Temperate Zone (STZ)—the zone in which the white ovals originated—is highly variable.
There are other features on Jupiter that are either temporary or difficult to observe from Earth. The South South Temperate Region is harder to discern even than the NNTR; its detail is subtle and can only be studied well by large telescopes or spacecraft. Many zones and belts are more transient in nature and are not always visible. These include the Equatorial band (EB), North Equatorial belt zone (NEBZ, a white zone within the belt) and South Equatorial belt zone (SEBZ). Belts are also occasionally split by a sudden disturbance. When a disturbance divides a normally singular belt or zone, an N or an S is added to indicate whether the component is the northern or southern one; e.g., NEB(N) and NEB(S).
Circulation in Jupiter's atmosphere is markedly different from that in the atmosphere of Earth. The interior of Jupiter is fluid and lacks any solid surface. Therefore, convection may occur throughout the planet's outer molecular envelope. As of 2008, a comprehensive theory of the dynamics of the Jovian atmosphere has not been developed. Any such theory needs to explain the following facts: the existence of narrow stable bands and jets that are symmetric relative to Jupiter's equator, the strong prograde jet observed at the equator, the difference between zones and belts, and the origin and persistence of large vortices such as the Great Red Spot.
The theories regarding the dynamics of the Jovian atmosphere can be broadly divided into two classes: shallow and deep. The former hold that the observed circulation is largely confined to a thin outer (weather) layer of the planet, which overlays the stable interior. The latter hypothesis postulates that the observed atmospheric flows are only a surface manifestation of deeply rooted circulation in the outer molecular envelope of Jupiter. As both theories have their own successes and failures, many planetary scientists think that the true theory will include elements of both models.
The first attempts to explain Jovian atmospheric dynamics date back to the 1960s. They were partly based on terrestrial meteorology, which had become well developed by that time. Those shallow models assumed that the jets on Jupiter are driven by small scale turbulence, which is in turn maintained by moist convection in the outer layer of the atmosphere (above the water clouds). The moist convection is a phenomenon related to the condensation and evaporation of water and is one of the major drivers of terrestrial weather. The production of the jets in this model is related to a well-known property of two dimensional turbulence—the so-called inverse cascade, in which small turbulent structures (vortices) merge to form larger ones. The finite size of the planet means that the cascade can not produce structures larger than some characteristic scale, which for Jupiter is called the Rhines scale. Its existence is connected to production of Rossby waves. This process works as follows: when the largest turbulent structures reach a certain size, the energy begins to flow into Rossby waves instead of larger structures, and the inverse cascade stops. Since on the spherical rapidly rotating planet the dispersion relation of the Rossby waves is anisotropic, the Rhines scale in the direction parallel to the equator is larger than in the direction orthogonal to it. The ultimate result of the process described above is production of large scale elongated structures, which are parallel to the equator. The meridional extent of them appears to match the actual width of jets. Therefore, in shallow models vortices actually feed the jets and should disappear by merging into them.
While these weather–layer models can successfully explain the existence of a dozen narrow jets, they have serious problems. A glaring failure of the model is the prograde (super-rotating) equatorial jet: with some rare exceptions shallow models produce a strong retrograde (subrotating) jet, contrary to observations. In addition, the jets tend to be unstable and can disappear over time. Shallow models cannot explain how the observed atmospheric flows on Jupiter violate stability criteria. More elaborated multilayer versions of weather–layer models produce more stable circulation, but many problems persist. Meanwhile, the Galileo Probe found that the winds on Jupiter extend well below the water clouds at 5–7 bar and do not show any evidence of decay down to 22 bar pressure level, which implies that circulation in the Jovian atmosphere may in fact be deep.
The deep model was first proposed by Busse in 1976. His model was based on another well-known feature of fluid mechanics, the Taylor–Proudman theorem. It holds that in any fast-rotating barotropic ideal liquid, the flows are organized in a series of cylinders parallel to the rotational axis. The conditions of the theorem are probably met in the fluid Jovian interior. Therefore, the planet's molecular hydrogen mantle may be divided into cylinders, each cylinder having a circulation independent of the others. Those latitudes where the cylinders' outer and inner boundaries intersect with the visible surface of the planet correspond to the jets; the cylinders themselves are observed as zones and belts.
The deep model easily explains the strong prograde jet observed at the equator of Jupiter; the jets it produces are stable and do not obey the 2D stability criterion. However it has major difficulties; it produces a very small number of broad jets, and realistic simulations of 3D flows are not possible as of 2008, meaning that the simplified models used to justify deep circulation may fail to catch important aspects of the fluid dynamics within Jupiter. One model published in 2004 successfully reproduced the Jovian band-jet structure. It assumed that the molecular hydrogen mantle is thinner than in all other models; occupying only the outer 10% of Jupiter's radius. In standard models of the Jovian interior, the mantle comprises the outer 20–30%. The driving of deep circulation is another problem. The deep flows can be caused both by shallow forces (moist convection, for instance) or by deep planet-wide convection that transports heat out of the Jovian interior. Which of these mechanisms is more important is not clear yet.
As has been known since 1966, Jupiter radiates much more heat than it receives from the Sun. It is estimated that the ratio between the power emitted by the planet and that absorbed from the Sun is 1.67 ± 0.09. The internal heat flux from Jupiter is 5.44 ± 0.43 W/m2, whereas the total emitted power is 335 ± 26 petawatts. The latter value is approximately equal to one billionth of the total power radiated by the Sun. This excess heat is mainly the primordial heat from the early phases of Jupiter's formation, but may result in part from the precipitation of helium into the core.
The internal heat may be important for the dynamics of the Jovian atmosphere. While Jupiter has a small obliquity of about 3°, and its poles receive much less solar radiation than its equator, the tropospheric temperatures do not change appreciably from the equator to poles. One explanation is that Jupiter's convective interior acts like a thermostat, releasing more heat near the poles than in the equatorial region. This leads to a uniform temperature in the troposphere. While heat is transported from the equator to the poles mainly via the atmosphere on Earth, on Jupiter deep convection equilibrates heat. The convection in the Jovian interior is thought to be driven mainly by the internal heat.
The atmosphere of Jupiter is home to hundreds of vortices—circular rotating structures that, as in the Earth's atmosphere, can be divided into two classes: cyclones and anticyclones. Cyclones rotate in the direction similar to the rotation of the planet (counterclockwise in the northern hemisphere and clockwise in the southern); anticyclones rotate in the reverse direction. However, unlike in the terrestrial atmosphere, anticyclones predominate over cyclones on Jupiter—more than 90% of vortices larger than 2000 km in diameter are anticyclones. The lifetime of Jovian vortices varies from several days to hundreds of years, depending on their size. For instance, the average lifetime of an anticyclone between 1000 and 6000 km in diameter is 1–3 years. Vortices have never been observed in the equatorial region of Jupiter (within 10° of latitude), where they are unstable. As on any rapidly rotating planet, Jupiter's anticyclones are high pressure centers, while cyclones are low pressure.
The anticyclones in Jupiter's atmosphere are always confined within zones, where the wind speed increases in direction from the equator to the poles. They are usually bright and appear as white ovals. They can move in longitude, but stay at approximately the same latitude as they are unable to escape from the confining zone. The wind speeds at their periphery are about 100 m/s. Different anticyclones located in one zone tend to merge when they approach each other. However Jupiter has two anticyclones that are somewhat different from all others. They are the Great Red Spot (GRS) and the Oval BA; the latter formed only in 2000. In contrast to white ovals, these structures are red, arguably due to dredging up of red material from the planet's depths. On Jupiter the anticyclones usually form through merges of smaller structures including convective storms (see below), although large ovals can result from the instability of jets. The latter was observed in 1938–1940, when a few white ovals appeared as a result of instability of the southern temperate zone; they later merged to form Oval BA.
In contrast to anticyclones, the Jovian cyclones tend to be small, dark and irregular structures. Some of the darker and more regular features are known as brown ovals (or badges). However the existence of a few long–lived large cyclones has been suggested. In addition to compact cyclones, Jupiter has several large irregular filamentary patches, which demonstrate cyclonic rotation. One of them is located to the west of the GRS (in its wake region) in the southern equatorial belt. These patches are called cyclonic regions (CR). The cyclones are always located in the belts and tend to merge when they encounter each other, much like anticyclones.
The deep structure of vortices is not completely clear. They are thought to be relatively thin, as any thickness greater than about 500 km will lead to instability. The large anticyclones are known to extend only a few tens of kilometers above the visible clouds. The early hypothesis that the vortices are deep convective plumes (or convective columns) as of 2008 is not shared by the majority of planetary scientists.
Great Red Spot
The Great Red Spot (GRS) is a persistent anticyclonic storm, 22° south of Jupiter's equator; observations from Earth establish a minimum storm lifetime of 350 years. A storm was described as a "permanent spot" by Gian Domenico Cassini after observing the feature in July 1665 with his instrument-maker Eustachio Divini. According to a report by Giovanni Battista Riccioli in 1635, Leander Bandtius, whom Riccioli identified as the Abbot of Dunisburgh who possessed an "extraordinary telescope", observed a large spot that he described as "oval, equaling one seventh of Jupiter's diameter at its longest." According to Riccioli, "these features are seldom able to be seen, and then only by a telescope of exceptional quality and magnification." The Great Spot has been nearly continually observed since the 1870s, however.
The GRS rotates counter-clockwise, with a period of about six Earth days or 14 Jovian days. Its dimensions are 24,000–40,000 km east-to-west and 12,000–14,000 km north-to-south. The spot is large enough to contain two or three planets the size of Earth. At the start of 2004, the Great Red Spot had approximately half the longitudinal extent it had a century ago, when it was 40,000 km in diameter. At the present rate of reduction, it could potentially become circular by 2040, although this is unlikely because of the distortion effect of the neighboring jet streams. It is not known how long the spot will last, or whether the change is a result of normal fluctuations.
According to a study by scientists at the University of California, Berkeley, between 1996 and 2006 the spot lost 15 percent of its diameter along its major axis. Xylar Asay-Davis, who was on the team that conducted the study, noted that the spot is not disappearing because "velocity is a more robust measurement because the clouds associated with the Red Spot are also strongly influenced by numerous other phenomena in the surrounding atmosphere."
Infrared data have long indicated that the Great Red Spot is colder (and thus, higher in altitude) than most of the other clouds on the planet; the cloudtops of the GRS are about 8 km above the surrounding clouds. Furthermore, careful tracking of atmospheric features revealed the spot's counterclockwise circulation as far back as 1966 – observations dramatically confirmed by the first time-lapse movies from the Voyager flybys. The spot is spatially confined by a modest eastward jet stream (prograde) to its south and a very strong westward (retrograde) one to its north. Though winds around the edge of the spot peak at about 120 m/s (432 km/h), currents inside it seem stagnant, with little inflow or outflow. The rotation period of the spot has decreased with time, perhaps as a direct result of its steady reduction in size. In 2010, astronomers imaged the GRS in the far infrared (from 8.5 to 24 μm) with a spatial resolution higher than ever before and found that its central, reddest region is warmer than its surroundings by between 3–4 K. The warm airmass is located in the upper troposphere in the pressure range of 200–500 mbar. This warm central spot slowly counter-rotates and may be caused by a weak subsidence of air in the center of GRS.
The Great Red Spot's latitude has been stable for the duration of good observational records, typically varying by about a degree. Its longitude, however, is subject to constant variation. Because Jupiter's visible features do not rotate uniformly at all latitudes, astronomers have defined three different systems for defining the longitude. System II is used for latitudes of more than 10°, and was originally based on the average rotation rate of the Great Red Spot of 9h 55m 42s. Despite this, the spot has 'lapped' the planet in System II at least 10 times since the early 19th century. Its drift rate has changed dramatically over the years and has been linked to the brightness of the South Equatorial Belt, and the presence or absence of a South Tropical Disturbance.
It is not known exactly what causes the Great Red Spot's reddish color. Theories supported by laboratory experiments suppose that the color may be caused by complex organic molecules, red phosphorus, or yet another sulfur compound. The GRS varies greatly in hue, from almost brick-red to pale salmon, or even white. The higher temperature of the reddest central region is the first evidence that the Spot's color is affected by environmental factors. The spot occasionally disappears from the visible spectrum, becoming evident only through the Red Spot Hollow, which is its niche in the South Equatorial Belt (SEB). The visibility of GRS is apparently coupled to the appearance of the SEB; when the belt is bright white, the spot tends to be dark, and when it is dark, the spot is usually light. The periods when the spot is dark or light occur at irregular intervals; in the 50 years from 1947 to 1997, the spot was darkest in the periods 1961–1966, 1968–1975, 1989–1990, and 1992–1993. In November 2014, an analysis of data from NASA's Cassini mission revealed that the red color is likely a product of simple chemicals being broken apart by solar ultraviolet irradiation in the planet's upper atmosphere.
The Great Red Spot should not be confused with the Great Dark Spot, a feature observed near Jupiter's north pole in 2000 by the Cassini–Huygens spacecraft. A feature in the atmosphere of Neptune was also called the Great Dark Spot. The latter feature, imaged by Voyager 2 in 1989, may have been an atmospheric hole rather than a storm. It was no longer present in 1994, although a similar spot had appeared farther to the north.
Oval BA is a red storm in Jupiter's southern hemisphere similar in form to, though smaller than, the Great Red Spot (it is often affectionately referred to as "Red Spot Jr.", "Red Jr." or "The Little Red Spot"). A feature in the South Temperate Belt, Oval BA was first seen in 2000 after the collision of three small white storms, and has intensified since then.
The formation of the three white oval storms that later merged into Oval BA can be traced to 1939, when the South Temperate Zone was torn by dark features that effectively split the zone into three long sections. Jovian observer Elmer J. Reese labeled the dark sections AB, CD, and EF. The rifts expanded, shrinking the remaining segments of the STZ into the white ovals FA, BC, and DE. Ovals BC and DE merged in 1998, forming Oval BE. Then, in March 2000, BE and FA joined together, forming Oval BA. (see White ovals, below)
Oval BA slowly began to turn red in August 2005. On February 24, 2006, Filipino amateur astronomer Christopher Go discovered the color change, noting that it had reached the same shade as the GRS. As a result, NASA writer Dr. Tony Phillips suggested it be called "Red Spot Jr." or "Red Jr."
In April 2006, a team of astronomers, believing that Oval BA might converge with the GRS that year, observed the storms through the Hubble Space Telescope. The storms pass each other about every two years, but the passings of 2002 and 2004 did not produce anything exciting. Dr. Amy Simon-Miller, of the Goddard Space Flight Center, predicted the storms would have their closest passing on July 4, 2006. On July 20, the two storms were photographed passing each other by the Gemini Observatory without converging.
Why Oval BA turned red is not understood. According to a 2008 study by Dr. Santiago Pérez-Hoyos of the University of the Basque Country, the most likely mechanism is "an upward and inward diffusion of either a colored compound or a coating vapor that may interact later with high energy solar photons at the upper levels of Oval BA." Some believe that small storms (and their corresponding white spots) on Jupiter turn red when the winds become powerful enough to draw certain gases from deeper within the atmosphere which change color when those gases are exposed to sunlight.
Oval BA is getting stronger according to observations made with the Hubble Space Telescope in 2007. The wind speeds have reached 618 km/h; about the same as in the Great Red Spot and far stronger than any of the progenitor storms. As of July 2008, its size is about the diameter of Earth—approximately half the size of the Great Red Spot.
Oval BA should not be confused with another major storm on Jupiter, the South Tropical Little Red Spot (LRS) (nicknamed "the Baby Red Spot" by NASA), which was destroyed by the GRS. The new storm, previously a white spot in Hubble images, turned red in May 2008. The observations were led by Imke de Pater of the University of California, at Berkeley, US. The Baby Red Spot encountered the GRS in late June to early July 2008, and in the course of a collision, the smaller red spot was shredded into pieces. The remnants of the Baby Red Spot first orbited, then were later consumed by the GRS. The last of the remnants with a reddish color to have been identified by astronomers had disappeared by mid-July, and the remaining pieces again collided with the GRS, then finally merged with the bigger storm. The remaining pieces of the Baby Red Spot had completely disappeared by August 2008. During this encounter Oval BA was present nearby, but played no apparent role in destruction of the Baby Red Spot.
Storms and lightning
The storms on Jupiter are similar to thunderstorms on Earth. They reveal themselves via bright clumpy clouds about 1000 km in size, which appear from time to time in the belts' cyclonic regions, especially within the strong westward (retrograde) jets. In contrast to vortices, storms are short-lived phenomena; the strongest of them may exist for several months, while the average lifetime is only 3–4 days. They are believed to be due mainly to moist convection within Jupiter's troposphere. Storms are actually tall convective columns (plumes), which bring the wet air from the depths to the upper part of the troposphere, where it condenses in clouds. A typical vertical extent of Jovian storms is about 100 km; as they extend from a pressure level of about 5–7 bar, where the base of a hypothetical water cloud layer is located, to as high as 0.2–0.5 bar.
Storms on Jupiter are always associated with lightning. The imaging of the night–side hemisphere of Jupiter by Galileo and Cassini spacecraft revealed regular light flashes in Jovian belts and near the locations of the westward jets, particularly at 51°N, 56°S and 14°S latitudes. On Jupiter lightning strikes are on average a few times more powerful than those on Earth. However, they are less frequent; the light power emitted from a given area is similar to that on Earth. A few flashes have been detected in polar regions, making Jupiter the second known planet after Earth to exhibit polar lightning. A Microwave Radiometer (Juno) detected many more in 2018.
Every 15–17 years Jupiter is marked by especially powerful storms. They appear at 23°N latitude, where the strongest eastward jet, that can reach 150 m/s, is located. The last time such an event was observed was in March–June 2007. Two storms appeared in the northern temperate belt 55° apart in longitude. They significantly disturbed the belt. The dark material that was shed by the storms mixed with clouds and changed the belt's color. The storms moved with a speed as high as 170 m/s, slightly faster than the jet itself, hinting at the existence of strong winds deep in the atmosphere.
Other notable features of Jupiter are its cyclones near the northern and southern poles of the planet. These are called circumpolar cyclones (CPCs) and they have been observed by the Juno Spacecraft using JunoCam and JIRAM. The cyclones have only been observed for a relatively short time from perjoves 1-15 which is approximately 795 days or two years. The northern pole has eight cyclones moving around a central cyclone (NPC) while the southern pole only has five cyclones around a central cyclone (SPC), with a gap between the first and second cyclones. The cyclones look like the hurricanes on Earth with trailing spiral arms and a denser center, although there are differences between the centers depending on the individual cyclone. Northern CPCs generally maintain their shape and position compared to the southern CPCs and this could be due to the faster wind speeds that are experienced in the south, where the average wind speed around 80 m/s to 90 m/s. Although there is more movement among the southern CPCs they tend to retain the pentagonal structure relative to the pole. It has also been observed that the angular wind velocity increases as the center is approached and radius becomes smaller, except for one cyclone in the north, which may have rotation in the opposite direction. The difference in the number of cyclones in the north compared to the south is due to the size of the cyclones. The southern CPCs tend to be bigger with radii ranging from 5,600 km to 7,000 km while northern CPCs range from 4,000 km to 4,600 km.
The northern cyclones tend to maintain an octagonal structure with the NPC as a center point. Northern cyclones have less data than southern cyclones because of limited illumination in the north-polar winter, making it difficult for JunoCam to obtain accurate measurements of northern CPC positions at each perijove (53 days), but JIRAM is able to collect enough data to understand the northern CPCs. The limited illumination makes it difficult to see the northern central cyclone, but by making four orbits, the NPC can be partially seen and the octagonal structure of the cyclones can be identified. Limited illumination also makes it difficult to view the motion of the cyclones, but early observations show that the NPC is offset from the pole by about 0.5˚ and the CPCs generally maintained their position around the center. Despite data being harder to obtain, it has been observed that the northern CPCs have a drift rate of about 1˚ to 2.5˚ per perijove to the west. The seventh cyclone in the north (n7) drifts a little more than the others and this is due to an anticyclonic white oval (AWO) that pulls it farther from the NPC, which causes the octagonal shape to be slightly distorted.
Current data shows that the SPC shows a positional variation between 1˚ and 2.5˚ in the latitude and stays between 200˚ to 250˚ longitude and has shown evidence of this recurring approximately every 320 days. The southern cyclones tend to behave similarly to the northern ones and maintain the pentagonal structure around the SPC, but there is some individual movement from some of the CPCs. The southern cyclones don't move around the south pole, but their rotation is more steady around the SPC, which is offset from the pole. Short term observation shows that the southern cyclones move approximately 1.5˚ per perijove, which is small compared to the wind speeds of the cyclones and the turbulent atmosphere of Jupiter. The gap between cyclones one and two provides more movement for those specific CPCs, which also causes the other cyclones that are close to move as well, but cyclone four moves less because it is farthest from the gap. The southern cyclones move clockwise individually, but their movement as a pentagonal structure moves counter-clockwise and drifts more toward the west.
The circumpolar cyclones have different morphologies, especially in the north, where cyclones have a "filled" or "chaotic" structure. The inner part of the “chaotic” cyclones have small-scale cloud streaks and flecks. The “filled” cyclones have a sharply-bound, lobate area that is bright white near the edge with a dark inner portion. There are four “filled” cyclones and four “chaotic” cyclones in the north. The southern cyclones all have an extensive fine-scale spiral structure on their outside but they all differ in size and shape. There is very little observation of the cyclones due to low sun angles and a haze that is typically over the atmosphere but what little has been observed shows the cyclones to be a reddish color.
The normal pattern of bands and zones is sometimes disrupted for periods of time. One particular class of disruption are long-lived darkenings of the South Tropical Zone, normally referred to as "South Tropical Disturbances" (STD). The longest lived STD in recorded history was followed from 1901 until 1939, having been first seen by Percy B. Molesworth on February 28, 1901. It took the form of darkening over part of the normally bright South Tropical zone. Several similar disturbances in the South Tropical Zone have been recorded since then.
One of the most mysterious features in the atmosphere of Jupiter are hot spots. In them, the air is relatively free of clouds and heat can escape from the depths without much absorption. The spots look like bright spots in the infrared images obtained at the wavelength of about 5 μm. They are preferentially located in the belts, although there is a train of prominent hot spots at the northern edge of the Equatorial Zone. The Galileo Probe descended into one of those equatorial spots. Each equatorial spot is associated with a bright cloudy plume located to the west of it and reaching up to 10,000 km in size. Hot spots generally have round shapes, although they do not resemble vortexes.
The origin of hot spots is not clear. They can be either downdrafts, where the descending air is adiabatically heated and dried or, alternatively, they can be a manifestation of planetary scale waves. The latter hypotheses explains the periodical pattern of the equatorial spots.
Early modern astronomers, using small telescopes, recorded the changing appearance of Jupiter's atmosphere. Their descriptive terms—belts and zones, brown spots and red spots, plumes, barges, festoons, and streamers—are still used. Other terms such as vorticity, vertical motion, cloud heights have entered in use later, in the 20th century.
The first observations of the Jovian atmosphere at higher resolution than possible with Earth-based telescopes were taken by the Pioneer 10 and 11 spacecraft. The first truly detailed images of Jupiter's atmosphere were provided by the Voyagers. The two spacecraft were able to image details at a resolution as low as 5 km in size in various spectra, and also able to create "approach movies" of the atmosphere in motion. The Galileo Probe, which suffered an antenna problem, saw less of Jupiter's atmosphere but at a better average resolution and a wider spectral bandwidth.
Today, astronomers have access to a continuous record of Jupiter's atmospheric activity thanks to telescopes such as Hubble Space Telescope. These show that the atmosphere is occasionally wracked by massive disturbances, but that, overall, it is remarkably stable. The vertical motion of Jupiter's atmosphere was largely determined by the identification of trace gases by ground-based telescopes. Spectroscopic studies after the collision of Comet Shoemaker–Levy 9 gave a glimpse of the Jupiter's composition beneath the cloud tops. The presence of diatomic sulfur (S2) and carbon disulfide (CS2) was recorded—the first detection of either in Jupiter, and only the second detection of S2 in any astronomical object— together with other molecules such as ammonia (NH3) and hydrogen sulfide (H2S), while oxygen-bearing molecules such as sulfur dioxide were not detected, to the surprise of astronomers.
The Galileo atmospheric probe, as it plunged into Jupiter, measured the wind, temperature, composition, clouds, and radiation levels down to 22 bar. However, below 1 bar elsewhere on Jupiter there is uncertainty in the quantities.
Great Red Spot studies
The first sighting of the GRS is often credited to Robert Hooke, who described a spot on the planet in May 1664; however, it is likely that Hooke's spot was in the wrong belt altogether (the North Equatorial Belt, versus the current location in the South Equatorial Belt). Much more convincing is Giovanni Cassini's description of a "permanent spot" in the following year. With fluctuations in visibility, Cassini's spot was observed from 1665 to 1713.
A minor mystery concerns a Jovian spot depicted around 1700 on a canvas by Donato Creti, which is exhibited in the Vatican. It is a part of a series of panels in which different (magnified) heavenly bodies serve as backdrops for various Italian scenes, the creation of all of them overseen by the astronomer Eustachio Manfredi for accuracy. Creti's painting is the first known to depict the GRS as red. No Jovian feature was officially described as red before the late 19th century.
The present GRS was first seen only after 1830 and well-studied only after a prominent apparition in 1879. A 118-year gap separates the observations made after 1830 from its 17th-century discovery; whether the original spot dissipated and re-formed, whether it faded, or even if the observational record was simply poor are unknown. The older spots had a short observational history and slower motion than that of the modern spot, which make their identity unlikely.
On February 25, 1979, when the Voyager 1 spacecraft was 9.2 million kilometers from Jupiter it transmitted the first detailed image of the Great Red Spot back to Earth. Cloud details as small as 160 km across were visible. The colorful, wavy cloud pattern seen to the west (left) of the GRS is the spot's wake region, where extraordinarily complex and variable cloud motions are observed.
The white ovals that were to become Oval BA formed in 1939. They covered almost 90 degrees of longitude shortly after their formation, but contracted rapidly during their first decade; their length stabilized at 10 degrees or less after 1965. Although they originated as segments of the STZ, they evolved to become completely embedded in the South Temperate Belt, suggesting that they moved north, "digging" a niche into the STB. Indeed, much like the GRS, their circulations were confined by two opposing jet streams on their northern and southern boundaries, with an eastward jet to their north and a retrograde westward one to the south.
The longitudinal movement of the ovals seemed to be influenced by two factors: Jupiter's position in its orbit (they became faster at aphelion), and their proximity to the GRS (they accelerated when within 50 degrees of the Spot). The overall trend of the white oval drift rate was deceleration, with a decrease by half between 1940 and 1990.
During the Voyager fly-bys, the ovals extended roughly 9000 km from east to west, 5000 km from north to south, and rotated every five days (compared to six for the GRS at the time).
- Comet Shoemaker–Levy 9
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- ^ The scale height sh is defined as sh = RT/(Mgj), where R = 8.31 J/mol/K is the gas constant, M ≈ 0.0023 kg/mol is the average molar mass in the Jovian atmosphere, T is temperature and gj ≈ 25 m/s2 is the gravitational acceleration at the surface of Jupiter. As the temperature varies from 110 K in the tropopause up to 1000 K in the thermosphere, the scale height can assume values from 15 to 150 km.
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- Planetary Society blog post (2017-05-09) by Peter Rosén describing assembly of a video of Jupiter's atmospheric activity from 19 December 2014 to 31 March 2015 from amateur astronomer images
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While China has nominally operated a space program for more than 50 years, it's only in the last decade that the country was independently able to put a human in space. In 2003, the China National Space Administration managed to launch a Shenzhou spacecraft, along with a single crew member, out of the Earth's atmosphere. His successful reentry marked the beginning of the era of the "Taikonaut."
In 2011, the CNSA is looking forward--far forward--to the next step in its still-nascent manned space program. China, its leaders would like you to know, is serious about building a space station.
Today, the China Manned Space Engineering Office (CMSEO) started soliciting names for its space station, in an effort to further popularize its renewed efforts and spending on manned space exploration. (Previously it has been referred to as the Tiangong station.) It's a fun idea, sure. But what about the actual plan? What will this station look like? When will it be ready? How will it be resupplied? Here's what we know so far:
The hardware: To a layperson, mockups of China's space station look a great deal like the International Space Station. It's comprised of multiple narrow sections connected at right angles, with protruding rectangular solar panels. This superficial resemblance is easily explained: a space station is built from many different modules, each completed on the ground and launched separately. In these early renderings, you can see a number of discrete units.
To put these numbers in context, the ISS weighs nearly 420 tons and measures in at over 100 meters in length. China's space station, even compared to the much smaller Mir, will be a bit of a runt.
The timeframe: Such estimations are virtually guaranteed to change, but here's the official line: The space station is due to be completed by "around 2020," which is when the ISS is tentatively scheduled to end its mission.
This is a fairly ambitious target, at least when viewed in the context of the leisurely pace at which Western space programs execute projects. But if China is willing to spend enough effort and money on the program, it's not an implausible estimate.
For reference, in-orbit construction of the ISS looks like it will end up taking just about 15 years. The station was announced in 1993, five years before in-orbit construction started. In-orbit construction on this project is scheduled to start within the year.
The extras: The two largest parties in the construction of the ISS both had preexisting technology available not just to build the station, but to maintain it, and to shuttle humans back and forth. On this front, China has a lot of work to do. According to Xinhua:
According to the schedule, a space module Tiangong-1 and the Shenzhou VIII spacecraft will be launched in the latter half of this year in the first unmanned rendezvous and docking mission. Shenzhou IX and Shenzhou X will be launched next year to dock with Tiangong-1. But problems in ensuring long-term missions for astronauts need to be overcome. Wang Zhaoyao, spokesman for the program, said that developing technology needed to guarantee mid-term missions in space (a stay of at least 20 days), and developing cargo supply technology will be among the tasks to be met during the 12th Five-Year Plan (2011-2015) period.
The Chinese space program has succeeded multiple times at sending men to space, but has yet to demonstrate the technology necessary to keep them there for long periods of time. Once fully developed, however, these new shuttles could serve at a catalyst for a broader expansion of China's space ambitions. In particular, they could help fulfill one of the country's stated ambitions: to visit the moon.
Image credit: China Daily
This post was originally published on Smartplanet.com | 0.815035 | 3.00631 |
in astronomy, an inconspicuous southern constellation. Antlia—Latin for “pump”—is visible in the Southern Hemisphere and up to the middle latitudes of the Northern Hemisphere, where it appears low on the southern horizon as a spring constellation. At a 10:00 pm observation of the sky in the Northern Hemisphere, Antlia rises in the southeast in February, culminates low on the horizon in early April, and drops below the horizon in May. In the mid-southern latitudes Antlia is visible more than half the year, dipping below the horizon in July and reemerging in December. Antlia lies west of the bright constellation Centaurus and south of Hydra, and is centered at about 30° S. celestial latitude.
The French astronomer Nicolas-Louis de Lacaille, who created the first complete map of the southern constellations, delineated Antlia in 1756. In that year, Lacaille published a map on which the constellation was identified as Machine Pneumatique, or “Air Pump.” The constellation, as he drew it, resembles a type of pump invented by the French physicist Denis Papin, and many sources say that Lacaille named the constellation to honor Papin’s invention. Others say its name refers to the pump invented by the Irish scientist Robert Boyle. The Latin name Antlia Pneumatica eventually supplanted Machine Pneumatique, and in 1930 the name was formally shortened to Antlia by the International Astronomical Union. The constellations Lacaille delineated are Antlia, Caelum, Circinus, Fornax, Horologium, Mensa, Microscopium, Norma, Octans, Pictor, Pyxis, Reticulum, Sculptor, and Telescopium. Lacaille’s catalog of southern stars, ‘Coelum Australe Stelliferum’, was published posthumously in 1763. Antlia is difficult to identify because it is composed of a sparse and indistinct collection of stars. However, it lies to one side of the Milky Way in a relatively unpopulated area of the sky, which makes it easier to view. Its brightest star, the orange giant Alpha Antliae, has a magnitude of only 4.3. A few degrees to the northeast lies Delta Antliae, a double star whose components are resolvable with a small telescope. It consists of a magnitude 5.6 blue-white star and a magnitude 9.6 companion. Zeta Antliae is a triple star whose components are separable with a small telescope. Antlia also includes at least three galaxies brighter than 13th magnitude. The brightest, NGC 2997, a type Sc (spiral) galaxy, is located about 30 million light-years away from Earth and can be observed due west of Alpha Antliae with a medium-power telescope,
Critically reviewed by James Seevers | 0.817365 | 3.719661 |
Full moon: January 12
January’s full moon is also known as the ‘old moon’ or ‘moon after Yule’. Native Americans call it the Full Wolf Moon, as when it appeared, wolves used to appear outside villages, howling in hunger.
Incidentally, January 12 this year is also the best night to see Venus. Unlike the full moon, we can never see Venus opposite the sun in our sky.
But on January 12, Venus swings out to its greatest angular distance of 47 degrees east of the sun, making the planet easily visible in the evening sky.
Look to the west after sunset to view Venus, which will shine brightly for several hours after dark.
Giant asteroid Vesta: January 17
Vesta is the brightest of all the asteroids, the second biggest after dwarf planet Ceres, and is occasionally visible from Earth.
It will shine brightest on January 17, and can be located most easily by looking for Gemini's twin stars Castor and Pollux.
It is the first asteroid to be visited by a spacecraft. The Dawn mission orbited Vesta in 2011, providing new insights into this rocky world.
New moon: January 28
This is the phase of the moon that is invisible from Earth, when the moon seems to disappear from the night sky.
If you are a keen stargazer, this is the best time of the month to view objects that are usually hard to see, such as galaxies and star clusters, because there is no moonlight to interfere with visibility.
Penumbral lunar eclipse: February 10
This will take place the day before the next full moon (February 11). A penumbral lunar eclipse happens when the Sun, Earth, and Moon align in an almost straight line.
When this happens, the Earth blocks some of the Sun's light from directly reaching the Moon's surface, and covers a part of the Moon with the outer part of its shadow, known as the penumbra.
The rest of the moon receives the same amount of sunlight as usual and is as bright as a full moon.
Because of this, it can be quite hard to tell the difference between a normal full moon and a penumbral eclipse. | 0.801165 | 3.217263 |
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