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Hercules, Leo IV and Ursa Major dwarf galaxies all started forming stars more than 13 billion years ago - and then abruptly stopped shortly after the Big Bang.The extreme age of their stars is similar to Messier 92, the oldest known globular cluster in the Milky Way.
The relics are evidence for a transitional phase in the early Universe that shut down star-making factories in tiny galaxies. This phase seems to coincide with the time when the first stars burned off a fog of cold hydrogen, a process called reionization. In this period, which began in the first billion years after the Big Bang, radiation from the first stars knocked electrons off primeval hydrogen atoms, ionizing the Universe’s cool hydrogen gas. The period of reionization is also the limit for how far telescopes can see: the process is what rendered the Universe’s hydrogen gas transparent to ultraviolet light.
Leo IV is one of more than a dozen ultra-faint dwarf galaxies found lurking around the Milky Way. The wide image, taken by the Sloan Digital Sky Survey, is a view of Leo IV and the surrounding neighborhood. The galaxy resides 500 000 light-years from Earth. The dotted line marks the galaxy’s boundaries, measuring about 1100 light-years wide. The small white box outlines the Hubble Space Telescope’s view. Leo IV has so few stars, roughly several thousand, that astronomers had difficulty identifying it as a galaxy. Astronomers discovered Leo IV in Sloan Digital Sky Survey images by spotting a region where a clump of stars was huddled closer together than stars in areas around it. The dwarf galaxy is composed of Sun-like stars, fainter, red dwarf stars, and some red giant stars brighter than the Sun. Hubble’s close-up view is shown in the inset at right, measuring 483 light-years wide. Astronomers used Hubble to measure the ages of the stars in Leo IV and two other ultra-faint dwarf galaxies. The Hubble image is a composite of exposures taken in January 2012 by the Advanced Camera for Surveys. Credit: NASA, ESA, and T. Brown (STScI)
The same radiation that sparked universal reionization also appears to have squelched star-making activities in dwarf galaxies. The small irregular galaxies were born about 100 million years before reionization began and had just started to churn out stars at that time. Roughly 2000 light-years wide, these galaxies are the lightweight cousins of the more luminous and higher-mass star-making dwarf galaxies near our Milky Way. Unlike their higher-mass relatives, the puny galaxies were not massive enough to shield themselves from the harsh ultraviolet light. What little gas they had was stripped away as the flood of ultraviolet light rushed through them. Their gas supply depleted, the galaxies could not make new stars.
The discovery could help explain the “missing satellite problem” - why computer simulations predict that thousands of dwarf galaxies should be around the Milky Way but only a few dozen have been observed. One possible explanation for the low number discovered to date is that there has been very little, or even no star formation in the smallest of these dwarf galaxies, leaving them virtually invisible.
The movie begins with Hubble’s image of the region in which Leo IV resides, then morphs into a view of the colors of the galaxy’s stars. The stars are next shown on the Hertzsprung-Russell (H–R) diagram, which traces the types and evolution of “main-sequence” stars by showing the relationship between a star’s color, based on its temperature, (horizontal scale) and its intrinsic brightness (vertical scale). Main-sequence stars are in the stable, middle phase of their development. In this diagram, the galaxy’s main-sequence stars are the same mass as our Sun or smaller. The graph then charts how the stellar distribution would look 1 billion years after the galaxy formed. Massive and hot, blue stars fill in the upper part of the main sequence. The animation compresses billions of years into just a few seconds, showing that over time the more massive stars evolve faster. They leave the main sequence to become red giant stars (upper right). Their departure leaves behind the cooler, lower-mass stars that evolve more slowly over many billions of years. Credit: NASA, ESA, T. Brown (STScI)
The Sloan survey recently uncovered more than a dozen of these galaxies in our cosmic neighborhood. These have very few stars — only a few hundred or thousand — but a great deal of dark matter, the underlying scaffolding upon which galaxies are built. Normal dwarf galaxies near the Milky Way contain 10 times more dark matter than the ordinary matter that makes up gas and stars, while in these so-called ultra-faint dwarf galaxies, dark matter outweighs ordinary matter by at least a factor of 100. Astronomers think the rest of the sky should contain dozens more of these ultra-faint dwarf galaxies with few stars, and the evidence for squelched star formation in the smallest of these dwarfs suggests that there may be still thousands more with essentially no stars at all.
“By measuring the star formation histories of the observed dwarfs, Hubble has supported the theoretical explanation for the paucity of such objects, according to which star formation in the smaller clumps would be shut down by reionisation,” said Jason Tumlinson of the Space Telescope Science Institute, a member of the research team.
Published in The Astrophysical Journal Letters. | 0.867543 | 4.039395 |
We should all know by now that Gaia is destined to study the motions and locations of 1 billion stars, but did you know that in order to achieve this goal, the precise location of the spacecraft itself is needed to an extremely high precision?
In addition to the expert tracking methods utilised by ESA’s mission operations team at ESOC, ground- based observatories also provide important data.
Enter GBOT, the Ground Based Orbit Tracking campaign that utilises a network of small-to-medium telescopes aiming at doing just that. In fact, GBOT is committed to deliver one set of data per day, which allows the determination of Gaia’s position good to 20 milli arcseconds.
GBOT’s data on Gaia will be included in the orbit reconstruction performed at ESOC in order to increase the accuracy of this undertaking to a level of 150 m in position and 2.5 mm/s in motion. These tight constraints are needed, to ensure that Gaia’s measurements of the stars and Solar System objects are as accurate as possible.
We – astronomers within the DPAC community – first set up the GBOT project in early 2008 and trialled it on missions already in the same orbital location that Gaia will operate from – L2 – including NASA’s WMAP and ESA’s Planck satellites. This allowed us to test our methods, and also get some clues about the probable magnitude Gaia that will have once in orbit. We assume that it will be around magnitude 18, but that it is still a big unknown.
Since then we have developed a whole infrastructure, developing observing techniques, a dedicated software pipeline, a database, and have recruited observatories to deliver us data. The backbone of the data will be supplied by the 2 m Liverpool telescope located on La Palma, Canary Island, Spain, and the Las Cumbres Optical Global Telescope Network (LCOGT.net), which operates 1 m telescopes in Chile, South Africa, Australia and Texas. We will also have some support from ESO’s VST (the 2.6 m telescope at Paranal, Chile) and additional facilities will also provide data when needed.
In 2012, we started a new fork of GBOT, radio-GBOT, which involves VLBI observations of Gaia. These are much more precise than the optical observations, but because they use more resources, we will use this technique less often and therefore the radio data will be used only to complement the optical measurements.
The coordination of GBOT activities is done from Heidelberg. The data reduction, analysis and storage, will be done at the Observatoire de Paris (with a mirror of the database in Heidelberg). The pipeline software, which has been developed by the GBOT group in Paris imports and harmonises the data obtained from the partner observatories, processes the data and finally outputs the position of Gaia. The data is then delivered to ESA’s mission operation centre in Darmstadt via the science operations centre in Madrid. Likewise, the reconstructed orbit files from ESOC are retrieved by GBOT, converted into data on Gaia’s position, with finder charts, and then supplied to the partner observatories.
Now, shortly before the launch of Gaia, GBOT is ready for action. GBOT’s observations commence about 10 days after launch; any earlier and Gaia is too bright for the instruments of the partner institutes. We hope to obtain motion clips of the spacecraft moving in front of star fields as the satellites journeys towards L2. It will be a challenging task for our small team, but we will do our very best to deliver!
We are looking forward to the next – operational – phase of our project and the new challenges that await.
Good luck Gaia and GBOT!
This blog entry was submitted by Martin Altmann, work-package manager of GBOT at
Zentrum fuer Astronomie at the University of Heidelberg, Germany. Thank you for sharing, Martin! | 0.849896 | 3.625642 |
Rosetta’s MIRO – the Microwave Instrument for the Rosetta Orbiter – has made nearly two billion science measurements at Comet 67P/C-G, and generated over 1.5 million spectra of gases in the comet’s coma. Principal Investigator Mark Hofstadter shares his team’s highlights of the mission, the challenges faced, and a hint of what’s still to come…
Being the first submillimeter instrument to fly in deep space, and having everything work are pretty high on our list of achievements! While we expected to be able to study the nucleus and coma gases with our instrument, and hoped to be able to see the dust particles, it was still a thrill to actually see the instrument doing what we thought it would. This comet puts out a lot of dust, and the dust particles are larger than predicted, so it was easier for MIRO to see the dust than we thought it would be, and we’ve been able to study it in more detail than anticipated.
But, just as for several of the instrument teams, the post-hibernation checkout gave us an initial unpleasant surprise. We were very cautious at first, and turned on one component of MIRO at a time, monitoring things in between to make sure everything was stable and working as expected. Early in the turn-on sequence, and near the end of a tracking pass, at JPL we saw that one of MIRO’s sensors reported that the spectrometer’s temperature shot up by 25 degrees for a few seconds, from about 20 to 45ºC. That could have been the sign of a short circuit temporarily heating things! Everything else looked normal to us, however, and the people in the control centre in Darmstadt said they saw nothing unusual. The original principal investigator of our instrument, Sam Gulkis, had just a few minutes to decide whether or not to command an immediate shut down of MIRO, before we lost radio contact with the spacecraft for several hours. What would you do? Shut down just in case something was short-circuiting to prevent further damage, or keep it on to avoid the risk of something having broken that would prevent us from turning it back on in the future? Sam, in Darmstadt, decided to leave MIRO on while we were out-of-contact. It was after midnight in Darmstadt when this happened, and Sam had been awake for many hours, so he went to sleep for a few hours while those of us at JPL (where it was still daytime) continued investigating. Sam later told us he fell asleep thinking we lost our instrument before even getting to the comet.
At JPL, one person asked the question “Why didn’t the control centre in Darmstadt, who monitor all the instruments, warn us that they saw a temperature spike?” Instead, Darmstadt reported everything looked normal! Strangely, he found that we did not ask Darmstadt to monitor the particular spectrometer temperature that spiked. At the same time, a second person contacted the lead engineer for MIRO and began describing the situation to her. She said that she recalled that one of the temperature sensors we had was unreliable, and even on the ground before launch would sometimes give crazy readings. Things began to make sense! We looked back through our documents, and found that the temperature sensor that spiked was the unreliable one. Because we knew it was unreliable when we launched it in 2004, we told ESOC not to monitor it. But by 2014 we had forgotten the problem, and at JPL we were looking at all our temperature sensors and saw the (false) spike.
When Sam woke up, we were able to tell him that he made the right choice in leaving MIRO turned on, and when Rosetta came back in contact with the Earth, we saw that MIRO was operating normally with all temperatures and currents as expected.
This story highlights one of the challenges of a long duration mission like Rosetta – how do you remember important details about your instrument which was built years ago? Most of the instruments on Rosetta were designed in the mid-1990’s, and started being built around 1997. We launched in 2004, and arrived at the comet in 2014. So now, near the end of 2016, we are using some hardware and software that is almost 20 years old. In many cases, the people who built it have retired. From the start, ESA realized that it was important to try and preserve as much human knowledge as possible in a format that would be easy to look up later. This included video documentation of the people building the instruments explaining anything that they thought could be relevant to the future, as well as typical user manuals and so-called design memos addressing very specific topics. MIRO’s user manual is about 300 pages long, and we are constantly updating it – we’re currently on version 5, and expect at least one more revision after the end of the mission!
We were surprised at how difficult it was for MIRO to detect the gas CO (carbon monoxide) around the comet. CO interacts strongly with radio waves, and we expected it to be seen soon after water was detected. Instead, it was the last molecule we saw of the six MIRO was designed to measure. Water was seen early in the summer of 2014, while it was only near perihelion – in the summer of 2015 – that we saw CO. The ROSINA instrument had measured CO in certain areas around the comet before that, but it was not everywhere. That seems to be why MIRO (and some of the other instruments) had so much trouble detecting CO. Early in the mission we were spending most of our time in the northern hemisphere, while the CO was mostly coming from the southern hemisphere.
One of the most difficult observations we made at the comet was measuring the polarized emission from the surface. Polarization describes how the electric and magnetic fields in a radio wave are oriented. MIRO measures one of the two possible orientations of the radio waves, which is typically sufficient; most of the radio waves given off by the comet are unpolarized (meaning they have random orientations), so the total amount of radio energy emitted by the comet is twice what we measure. But when radio waves encounter an abrupt change – such as when they strike the boundary between the nucleus and space – at a certain angle, one polarization can be preferred over the other. The angle at which that occurs (called the Brewster Angle) can be used to determine some of the electrical properties of the nucleus material. By the way, polarized sunglasses use this principle: sunlight reflected off a roadway or the sea for example, is preferentially polarized in one direction, and the sunglasses block that polarization, reducing the glare. You can test the effects of polarization yourself: next time you are wearing polarized sunglasses compare what you see holding your head normally with what you see tilted 90 degrees to the side (so your ear is almost touching your shoulder); some reflections and some digital displays will look much dimmer with your head tilted one way or another.
MIRO wanted to take advantage of this effect by observing the same spot on the nucleus at about the same time, but with the spacecraft in two different orientations (just like tilting your head). That would allow MIRO to measure both possible polarizations of the radio waves, and any preference for one polarization over the other would let us learn something about the properties of the nucleus we could not figure out any other way. That turned out to be very difficult to do for the following reasons:
– It can take more than an hour to rotate the spacecraft 90 degrees. During that time, the spot we are looking at on the nucleus is moving and the viewing geometry is changing, making it hard to interpret our measurements.
– Because Rosetta is solar powered, we never want to tilt it in such a way as to prevent our solar panels from getting sunlight. That limits when we could try to make this measurement.
– Rotating the spacecraft can interfere with some of the measurements being made by other instruments on the spacecraft.
– Other high priority science investigations could only be done at the times when it was easiest to do our polarization measurements.
In the end, after lots of hard work from the Science Ground Segment folks at ESAC, they determined a handful of times we could make these measurements. They were successfully carried out, but it will take us quite awhile to fully calibrate and measure this small polarization effect.
Surprises and mysteries
Being surprised by what we see at the comet is, of course, one of the most fun things about this mission! MIRO has seen that some properties of the comet’s nucleus (those related to how it warms and cools in response to sunlight) are relatively uniform all over the surface and down to a few centimetres beneath the surface. Many on our team expected these thermal properties to be much more variable. Other aspects of the nucleus, such as its composition, do seem to vary from place to place (such as the amount of CO, which I mentioned earlier). That is something we hoped to see, but were not sure whether or not it would be true. These are clues we are now using to try and figure out where and how comets form, and how they evolve over time.
For me, one of the most surprising measurements was that some comet outbursts seem to have lots of dust but little gas. How can that be, given that we thought the gas is what lifts the dust? When ice in the nucleus sublimates (turns to gas), it expands rapidly into the relatively empty space around the comet. The gas moves at hundreds to over a thousand metres per second. This rapidly moving gas is what is thought to move most of the small dust particles seen lifted off the nucleus. Rosetta has observed many comet outbursts. In some of them, pictures reveal narrow ‘jets’ of small dust particles. Our expectation is that these dust jets are marking spots where gas jets exist. We were surprised to see that some dust jets don’t seem to be associated with any extra gas emission, and similarly, we may have seen instances of gas jets existing without lifting any dust. Another mystery is that the MIRO instrument has seen the situation where a dust jet forms and the coma gases get 40ºC warmer, before the amount of gas increases (the 19 February 2016 outburst is the best studied example of this). What is going on?
The answer seems to be that Rosetta’s close-up view is letting us see the effects of complex interactions among the gas, dust and the surface of the nucleus. We are still analysing the data, but some of the ideas being explored involve landslides on the nucleus that moves the dust (this allows dust emission to increase without any change in gas emission), and warm dust heating the relatively cool coma gases (explaining why the temperature of the gas could change even when the amount of gas did not).
Water, water everywhere…
MIRO observes changes in comet activity over time: this plot shows some comparisons in MIRO’s measurements over the duration of the mission.
More science to come!
After the end of operations this month, we’re looking forward to analysing everything, both because we know we’re going to figure out all kinds of details when we have time to sit back and really think about our datasets, and because the most exciting things are probably going to be serendipitous discoveries! Recently MIRO has been studying how the nucleus properties change with depth in the upper tens-of-centimetres of the surface. Our simple models indicate there are changes, but we want to do more work to convince ourselves the effect is real. We’re also looking at how the presence of dust can influence gases far away from the dust, specifically what happens to the fast-moving gas as it moves through the much slower dust, and how heat emitted from the relatively warm dust might get absorbed by gas far away.
Being part of this large, international team, doing something that is difficult and exciting, is a highlight of working this mission. On a personal note, it always gives me a feeling of pride in humanity to walk into one of our Rosetta science team meetings, and see how the individuals seamlessly transition among conversations internal to an instrument team to those across national or instrument boundaries. Languages and priorities may differ, but it is clear we are all working towards the success of the same mission.
This post is part of a series that looks behind the scenes of the instrument teams to find out what it was really like “living with a comet” for two years.
MIRO stories featured on this blog
Rosetta’s first peek at the comet’s south pole
MIRO maps water in comet’s coma
Comet ‘pouring’ more water into space
Getting to know Rosetta’s comet – Science special edition
MIRO bathes in water vapour | 0.802438 | 3.304279 |
Ancient Worlds Could Be Kept 'Alive' by Gravitational Nudges
For more than three billion years now, Earth’s ability to support life has been a delicate balancing act. Climatic periods of severe cold or hot have brought life to its knees. Glaciers covered the planet in the “snowball Earth” epoch, which ended some 650 million years ago. During the extremeheat of the early Triassic period around 250 million years ago, tropical sea temperatures exceeded 100 degrees Fahrenheit.
But the temperature pendulum has always swung back from these extremes, thanks in large part to the moderating phenomenon of plate tectonics. The sliding movements of Earth’s crust regulate the amount of heat-trapping carbon in our atmosphere by trapping the carbon in the seafloor and releasing it later by way of volcanoes. In this way, the “carbon cycle” has helped stir our planet out of frozen slumbers and has curbed the greenhouse effect.
Yet all good things, as the saying goes, must come to an end. The driver of Earth’s tectonics is heat from our planet’s slowly cooling core and the decay of radioactive elements deep within the planet. In another few billion years, that heat will have largely dissipated and Earth’s geophysical activity will cease. Although life might have already bitten the dust by then, likely thanks to a warming Sun, the end of the moderating carbon cycle will exacerbate conditions for any embattled organisms that might still exist.
A new study considers life’s geophysical collapse on planets outside our solar system. Specifically, the paper looks at exoplanets orbiting red dwarf stars, which are smaller, cooler and less massive than our Sun. These dim red stars host the easiest planets for our telescopes to observe in the “habitable zone,” the orbital band in which surface water neither permanently freezes away nor boils off. Conveniently, a large portion of red dwarfs (and their attendant solar systems) are also older than our Sun. Older stars are less stormy than younger ones, further easing the detection of planets around them.
It stands to reason that among the first habitable zone planets we will get to study will be those around ancient, low-mass stars. But these worlds — aged on the order of 10 billion years — could be geophysically, and therefore, biologically, dead.
“While the habitable zone ensures that the surface and atmosphere of a planet are the right temperature to support life, the planet’s interior could have cooled to the point that geophysical activity has ceased,” said Richard Greenberg, a planetary sciences professor at the University of Arizona in Tucson. “Astrobiologists believe geophysical activity may be essential for life.”
This issue is addressed in a paperto be published in the July 1 issue of the Monthly Notices of the Royal Astronomical Society by Greenberg’s student Christa Van Laerhoven, along with co-authors Richard Greenberg and Rory Barnes of the University of Washington.
Life support for dead planets
The new study considers how other exoplanets in a red dwarf solar system might keep the geophysical fires lit inside of a habitable planet, courtesy of the influence of gravitational tides.
Stars, planets and moons in solar systems all gravitationally influence each other. If a habitable planet were kept in an elliptical orbit around its star, owing to the gravitational tugging of another planet sharing its solar system, the star could warp the habitable planet’s shape. That tidal warping would generate, by friction, enough internal warmth to maintain geophysical activity.
A powerful example of this tidal heating is right here in our solar system with Jupiter and its moon, Io. The orbital relationship of Jupiter and its four biggest moons, including Io, has kept Io in an elliptical orbit around the parent planet. Io gets gravitationally pulled and squeezed as it orbits periodically closer and farther away from Jupiter. All that flexing creates tremendous heat within Io’s rocky structure, forcing the “pizza-faced” moon’s myriad volcanoes to constantly erupt molten material.
Too much flexing and a habitable planet goes volcanically crazy, evaporating all its water. Not enough flexing, on the other hand, and the planet eventually slips into a geophysical coma. The latter would happen if an orbit were too circular. Unlike oval-shaped elliptical orbits, which subject their planets to varying gravitational forces and thus tidal heating, circular orbits translate to a constant gravitational influence, and therefore no tidal heating.
A consequence of tidal heating, however, is that it eventually circularizes the elliptical orbit of another body, whether planet or moon. This normalizing effect follows from the gravitationally flexed body being nudged into an orbital path that reduces the flexing. For habitable planets around low-mass stars, a circularization of the planet’s orbit would happen almost immediately, within a few thousand years of the star and planet forming.
So, for planets to stay habitable around low-mass stars on account of geophysical activity, they need to somehow stay out of circular orbits. The researchers set out to find what kinds of planets, in what outer orbits, could prod the inner, habitable planet into suitable orbital eccentricities, or ellipticalness, for extended periods. (The outer planet, it should be noted, by virtue of being farther away from the star, does not experience as strong a normalizing effect on its orbital shape, so it can stay eccentric without issue.)
Gauging the sort of planetary arrangements that promote habitability will guide astronomers in their hunt for livable exoplanets.
“If another planet’s gravitational effect keeps the habitable-zone planet on a slightly eccentric orbit, that would promote internal tidal heating,” said Greenberg. “Thus, before concluding that such a habitable zone planet is indeed habitable, another planet should be sought out observationally that could promote the requisite internal heat.”
Greenberg and colleagues started with a hypothetical Earthly twin planet,with the same size, mass and susceptibility to tidal heating effects. They placed this planet in their models at a distance of 3.4 percent of the average Sun-Earth distance around a star with a tenth of the Sun’s mass — in other words, smack dab in this dim, cool, red dwarf star’s habitable zone. They also ran simulations of such a world around a real star, the dim crimson sun known as DEN1048.
The researchers then plugged in outer, companion planets of varying masses, distances and shaped orbits. The team looked for what combinations kept the habitable zone planet in a range of internal heating levels that were neither too nor hot nor cold.
Admittedly, the amount of heating needed to keep Earth’s own tectonic engine purring along is not known with much certainty. As a crude basis, though, the researchers went with the current level of heat emanating from Earth’s surface, which is 0.08 watts per square centimeter.
A reasonable lower limit was supplied by the example of geologically moribund Mars. It is reckoned that tectonic activity ceased on the Red Planet when the surface heat level there whittled to about half of Earth’s present value.
A value considered too high: Io’s 2 watts per square centimeter, though life would likely die out due to rampant volcanism well shy of that figure.
Out of the hot, but not into the cold
As the effects of the outer planet’s parameters played out on that of the inner, habitable world in the models, the researchers considered two phases both of these planets’ orbits go through. The first phase takes place shortly after the planets form, while they feel each other out gravitationally. The planets enter vacillating eccentric orbits, where one goes oval while the other circularizes, and then vice versa. The second phase is when the planets settle into stable, long-term eccentricities.
For a habitable planet to keep geophysically active, that first phase has to be short enough such that the planet does not volcanically load its atmosphere with carbon dioxide and end up lethally hot and desiccated.
The second phase, meanwhile, needs to last long enough to keep the planet active for us to get around to observing it. Again, that figure is a ballpark 10 billion years after the planet originally formed around its elderly, low-mass star.
A promising find
Fortunately, for life’s sake, the researchers found that in many outer planet situations, this fast-first-phase, slow-second-phase combination pans out. For instance, a Neptune-sized outer planet a few times farther out from its sun than the inner, rocky planet, and with a relatively minor eccentricity could keep the habitable planet geophysically active.
The outer planet in this scenario needn’t even be biggish like our outer planets of Neptune or Jupiter. An Earth-sized outer planet would suffice in keeping up a desirable eccentricity for the inner planet over time. The researchers modeled an Earth-sized outer planet in a range of eccentricities and distances, from quite close to the habitable, inner world to exceeding half the Earth’s average distance to the Sun, and found that this relatively small world would do the trick.
The findings are, of course, a first approximation. It’s highly unlikely that another potentially habitable exoplanet would have exactly Earth’s mass, size, water content, et cetera, so each discovered example would be its own scenario.
The presence of multiple planets (which seems common based on studies of exo-solar systems so far) would also further complicate matters. The Earth-like planet’s tidal heating could vary over time owing to the convoluted gravitational interactions of its planetary neighbors. Accordingly, surface habitability might change over time, too.
Humanity’s ultimate refuge?
Those nuances aside, the sustained geophysical activity induced in the habitable planet by an outer companion could be very long indeed. In fact, habitable planets around low-mass stars could remain geophysically active for many tens of billions of years. That’s intriguing, because red dwarf stars can live on for trillions of years, unlike our Sun, which will die out after 10 to 12 billion years.
“The presence of the outer planet ensures that the inner planet’s eccentricity does not die away, except over timescales way longer than the 14-billion-year age of the universe — perhaps even trillions of years,” said Greenberg. “Therefore, a planet orbiting in the habitable zone of a star like we modeled — with a tenth of the Sun’s mass, with an outer companion that sustains modest tidal heating — could be the longest-lived surface habitat available in the universe.”
When our planet and even solar system become no longer inhabitable, an interstellar human race might find itself a new, permanent home around a red dwarf star. For that matter, advanced aliens might have already had the same idea. Our various SETI (Search for Extraterrestrial Intelligence) efforts, such as listening for radio transmissions or searching for signs of life in exoplanetary atmospheres, might want to focus on habitable worlds with outer planets around ancient red dwarfs.
The paper authors took a moment to expound on the ramifications of this particular finding in their paper.
“The Earth will become uninhabitable within the next few billion years, and so this type of planet may be the ultimate home for humanity in the very (very) distant future,” the authors wrote. “Similarly, if these planets are the ideal locations for long-term survival, they may already be inhabited by space-faring civilizations and hence may be favorable targets for SETI.” | 0.898467 | 3.790525 |
Mysterious ‘Wave’ of Star-Forming Gas May Be the Largest Structure in the Galaxy
rion’s belt may be more than just a waist of space.
According to new research published today (Jan. 7) in the journal Nature, the girdled constellation may also be a small piece of the single largest structure ever detected in the Milky Way galaxy — a swooping stream of gas and baby stars that astronomers have dubbed “the Radcliffe Wave.”
Spanning about 9,000 light-years (or about 9% of the galaxy’s diameter), the unbroken wave of stars begins near Orion in a trough about 500 light-years below the Milky Way’s disk. The wave swoops upward through the constellations of Taurus and Perseus, then finally crests near the constellation Cepheus, 500 light-years above the galaxy’s middle. The entire undulating structure also stretches about 400 light-years deep, includes some 800 million stars and is dense with active star-forming gas (known in more delightful terms as “stellar nurseries”).
When observed in 3D atop the rest of the Milky Way, this swooping suburb of baby-booming stars appears to be more than just the sum of its parts, study co-author João Alves said in a statement.
“What we’ve observed is the largest coherent gas structure we know of in the galaxy,” said Alves, a professor of astrophysics at the University of Vienna. “The sun lies only 500 light-years from the wave at its closest point. It’s been right in front of our eyes all the time, but we couldn’t see it until now.”
Alves and an international team of colleagues detected the Radcliffe Wave (named for Harvard’s Radcliffe Institute for Advanced Study, where the bulk of the research was conducted) while creating a 3D map of the Milky Way with data gathered largely by the European Space Agency’s Gaia satellite. They noticed the strange, undulating pattern of gas and stars around Orion when looking at an object known as the Gould Belt, which was first detected more than 100 years ago.
For a century, astronomers have thought the Gould Belt was a ring-shaped circle of star-forming gas, with Earth’s sun near its center. However, once the authors of the new study began digging into the Gaia data, they realized this does not seem to be the case. Rather, the Gould Belt appears to be just a piece of the much larger Radcliffe Wave, which does not form a ring around our solar system but swoops toward and away from it in an enormous waveform.
“We don’t know what causes this shape but it could be like a ripple in a pond, as if something extraordinarily massive landed in our galaxy,” Alves said.
Prior studies of the Gould Belt have suggested the same. Perhaps a gigantic blob of dark matter crashed into the young gas cloud millions of years ago, warping the galaxy’s gravity and scattering the nearest stars into the pattern seen today, one 2009 study in the journal Monthly Notices of the Royal Astronomical Societyposited.
“What we do know is that our sun interacts with this structure,” Alves said.
According to the researchers, stellar velocity data suggests that our solar system passed through the Radcliffe Wave some 13 million years ago — and, in about another 13 million years, will cross into it again. | 0.815378 | 3.742139 |
New NASA video bolsters my contention as to what created the Carolina Bays.
In my book Magnetic Reversals and Evolutionary Leaps, I proposed that the Carolina Bays were formed by millions of gigantic explosions in the sky, explosions triggered by a magnetic reversal. (Chapter 13, “Dinosaur Tombstones.”)
The Carolina Bays, a host of huge elliptical depressions gouged into the ground about 12,000 years ago, were formed at about the same time, if not exactly the same time, as the Gothenburg magnetic excursion.
Varying in size from one to several thousand acres, and measuring from 164 feet (50 m) to 6.8 miles (11 km) across, as many as 2½ million of these oval depressions scar the landscape from Florida to New York to Texas.
In Maryland, the bays are called Maryland basins. In Mississippi and Alabama they’re called Grady ponds. In Kansas and Nebraska they’re called Rainwater basins. In Texas they’re called Salinas (because they often contain salty water). The bays, aligned with one another with their long axes pointing generally north, all appear to have formed at the same time, from the same cause.
The bays all have raised rims and frequently intersect other bays. More than 50,000 overlapping bays—some larger than nearby cities (yes, larger than nearby cities!)—have been identified on the U.S. Atlantic coast alone.
Most of the bays are very shallow, 50 feet at most, but usually not more than 20 feet. (That’s if you consider a body of water as deep as a five-story building to be shallow.)
Some of the larger Carolina Bays are (or once were) lakes. However, because most of them were so shallow that they became swamps or marshland, that’s what people thought they were. But in 1930, aerial photography exposed their unusual shapes and orientations.
The image above is of an area measuring about twelve miles by ninemiles (20 km by 15 km) approximately eighteen miles (30 km) southeast of Fayetteville, North Carolina. This one tiny corner of the world contains 20 such oval depressions. (Also see note 1.)
Yet another peculiarity is that the sandy rims are white. This, in spite of the fact that white sand is rare in the Carolinas; it’s usually tan or reddish.
What could have turned the sand white? Very high temperature, usually higher than 1,500 degrees F, could have burned off the reddish iron impurities from the surface of the quartz, says Richard Firestone, co-author of the book Cycle of Cosmic Catastrophes.
But where did that heat originate? And what could possibly gouge more than two million huge holes into the ground, all at the same time?
At first, scientists thought the depressions had been formed by a comet or meteor exploding above the earth. However, almost no meteorites have ever been found in the Carolinas.
A newer theory holds that the Carolina Bays were formed by secondary impacts after a meteor had crashed into the ice somewhere near Michigan. That collision threw millions of chunks of ice – massive chunks of ice – into the sky, which then flew hundreds of miles away from the original point of impact at low angles. That (supposedly) explains the elliptical bays: They were formed by oblique impacts as the airborne ice hurtled back to earth.
Wow! It must take one hellishly big chunk of ice to create a crater bigger than an entire city.
No, I simply cannot buy the flying-ice theory.
One reason I don’t buy into the flying-ice theory is that there would have been no ice there to begin with.
Look at the dates: The last major ice age commenced about 23,000 years ago coincident with the Mono Lake magnetic excursion. The ice sheets then grew for about 5,000 years, reaching their full extent about 18,000 years ago. They should have been long gone from the Michigan area by 12,000 years ago when the Carolina Bays were formed.
Instead, I think the Carolina Bays were formed by millions of gigantic explosions in the sky; carpet bombed by the gods.
This video from NASA helps reinforce that view.
Entitled “Earth’s Magnetosphere,” the video describes our magnetosphere as a giant bubble of magnetism that envelopes our planet and protects it from the sun, including protecting if from the sun’s ultraviolet radiation. “It’s clear that this magnetic bubble was key to helping earth develop into a habitable planet,” the video asserts.
The magnetosphere is a permeable shield, the video tells us. The solar wind will periodically connect to the magnetosphere, forcing it to reconfigure. This can create a rift, which allows energy to pour into our formerly safe haven. These rifts open and close many times daily, or even many times hourly. Most of them are small and short-lived. Others are vast and sustained. When the sun’s magnetic field connects to the earth’s in this way, the fireworks start.
The magnetosphere absorbs the incoming energy from the solar wind and “explosively” releases that energy in the form of geomagnetic storms and sub-storms, according to Dr. Eftyhia Zesta, Chief of the Geospace Physics Laboratory at NASA’s Goddard Space Flight Center. Magnetic lines of force converge and reconfigure, resulting in magnetic energy and charged particles flying off at an intense speeds.
Scientists have been trying to learn why this crisscrossing of magnetic field lines – called magnetic reconnection – triggers such “violent” explosions.
Whatever the cause, whether it was a giant chunk of ice flying through the sky, or a violent explosion triggered by the Gothenburg magnetic excursion, I sure wouldn’t want to have been standing at ground zero.
On a more personal note, I was lucky enough to visit a Carolina Bay a couple of years ago near the town of Olanta, South Carolina, in the Woods Bay State Park. (If you look for Olanta on Google maps (satellite view) and then zoom out just slightly, you will see Woods Bay. It is far bigger than the town itself.)
Does it look like a bay? No. It looks like a swamp. In fact, it is a swamp.
There were no park employees on duty on the day I toured the park (actually both my wife and I toured the park), and we wondered if we would see any alligators.
The answer came very quickly, because we soon spied several alligators basking in the sun, soaking up the heat. Perhaps you can spot them in my photos. Since we were the only people in the entire park, and we had no idea how many alligators might be lying in wait, we didn’t stick around too long.
We both made it back safely, so I guess the alligators weren’t all that hungry.
If you go to Google maps (satellite view) and peruse the North Carolina/South Carolina region, you’ll be astounded at how many of these giant paw prints you can find, even today. Literally hundreds of such bays surround Lumberton, North Carolina, alone.
More info on the Carolina Bays:
Info on flying-ice theory:
More aerial photos:
George Howard in Raleigh, North Carolina has done a tremendous amount of research on the Carolina bays. View his website here:
For even more info,
see my book Magnetic Reversals and Evolutionary Leaps. | 0.868194 | 3.374864 |
On September 28, 1969, a fiery meteorite blazed a trail from space, and crashed into regional Victoria. The debris contained an extraordinary surprise; the first organic molecules of extraterrestrial origin.
Located 167 km north of Melbourne, Murchison is a sleepy Victorian country town, nestled alongside the Goulburn River.
Primarily an agricultural centre, the town was founded by settlers from Tasmania in 1840. It expanded during the gold rush in Victoria in the 1850s, where it was a key stopover and supply point for local prospectors.
Otherwise, the town is wholly unremarkable, a highly unlikely spot for a revolutionary scientific discovery.
On September 28, 1969, residents across Victoria were startled when a blazing fireball erupted above them.
Clearly visible in the Sunday afternoon sun, the meteorite streaked across the rural skies. Witnesses reported loud explosions, crackling, smoke and a strange smell, like methylated spirits;
'I saw smoke in the sky, and soon after there was an explosion.
It seemed like an earth tremor. Our next door neighbour was knocked over by it.
It rattled the buildings, and gave us a hell of a shock.'
-Mervyn Hellford, eyewitness
Weighing 100 kilos, the meteorite finally disintegrated above Murchison, showering the surrounding area with approximately 2 000 chunks of space debris.
Curious locals immediately began recovering the fragments, and either keeping them as souvenirs, or turning them in to the local authorities.
Within a few days, samples were sent to Melbourne University for further analysis. John Lovering, then a professor of Geology at the university, received the first samples in a plastic bag:
'I opened it (the bag) up, and suddenly this great organic chemistry smell hit me. It was very very strong.
It looked like a lump of coal. And I knew what it was straight off; a carbonaceous chrondite. One of the most primitive of all of the meteorites.
It was very exciting.'
The preliminary results showed that the Murchison Meteorite was at least 4.5 billion years old, and so was likely older than the earth itself. Professor Lovering's guess that it was a carbonaceous chrondite was proved correct, and so made the find particularly rare.
After the preliminary analysis was completed in Melbourne, rock samples were sent to NASA for a more detailed assessment.
The scientific community was rocked in 1970 when the team at NASA announced the presence of 74 different amino acids in their samples. The majority were exotic molecules not found on earth but, remarkably, 6 were common amino acids known from organic, terrestrial chemistry.
These were the first organic molecules ever discovered on an extraterrestrial body.
And that these molecules were found in a rock older than the Earth, and that they had somehow survived in the vacuum of space for many millions of years, turned theories of life's evolution on their head.
While many aspects of the origins, and development, of life on earth are well known, some parts remain a mystery.
The Darwinian theory of evolution and natural selection has wide acceptance, but there is still debate in the scientific community about what may have started this process off. Did lightning in the earth's primitive atmosphere trigger the first organic chemistry? Did the first molecules develop at super heated vents on the ocean floor? Is there simply some unknown process at play, awaiting discovery?
The earth was formed approximately 4.5 billion years ago, and the earliest signs of life that have been detected - microscopic bacterial fossils - have been dated to 4.2 billions year ago, when the planet would still have been cooling and largely inhospitable.
How then did life take hold so quickly?
The discovery of amino acids in the Murchison Meteorite provided the pathway to a new theory; perhaps the first organic molecules arrived on a meteorite.This interpretation of the Murchison Meteorite was hugely controversial when it was announced, and debate around the amino acid discovery remains fierce to this day.
Another element was added to the debate in 1996.
In 1984, NASA recovered meteorite fragments from Antarctica. Subsequent analysis, and comparison to Martian rock samples, allowed them to determine that the meteorite had originated on Mars.
Dubbed the 'Allan Hills Meteorite', after the mountainous region where it was found, it was determined that the rock was approximately 4 billion years old, and had crashed into earth about 13 000 years ago.
In 1996, NASA announced that the meteorite may contain fossils of microscopic bacteria.
In a paper published in the journal 'Science', research lead David McKay presented several pieces of evidence to suggest the Allan Hill meteorite showed evidence of life.
Chief among these was the presence of microscopic magnetite crystals, a by-product of organic chemistry well known from earth based biology. At the time, these crystals were only known to be formed by bacteria, and so presented a compelling argument that bacterial life had once existed on Mars.
If this were correct, it was easy to extrapolate that a similar meteorite may have arrived on earth billions of years ago, and brought the first traces of life to this planet with it. Were we all, in fact, Martians?
But in subsequent years, many of the conclusions from the 1996 research have been called into question. It was later shown that magnetite crystals can also be formed by the shock wave from intense explosions, of which the early solar system would have been rife.
Nevertheless, the question of whether the Allan Hills meteorite contains Martian fossils remains open, debated by passionate supporters and sceptics.
The findings from the Murchison meteorite also remain significant, and are subject to ongoing discussion. In the decades since the amino acids were first discovered, they have been detected numerous times on off-earth objects, including meteorites, asteroids, and even the surface and tail of Halley's Comet. | 0.837181 | 3.486435 |
Ben Longmier saw his first aurora in Wisconsin when he was 10 years old. "I wasn't prepared for how dynamic and beautiful they were," he says.
He saw the phenomenon again this month in Alaska, but this time he wasn't just looking at it from the ground. He got an up-close look thanks to some high-tech cameras and a weather balloon, capturing the view from inside the aurora.
Longmier is a rocket scientist with Ad Astra, a company that is building a plasma rocket that might eventually help us to explore new planets. "We're developing the next generation of rockets for space travel," Longmier says. "We hope that one day the R&D that we're doing will lead to human transport to Mars." Lately, though, Longmier has been spending his vacation days in Alaska, launching not rockets but rather more than 20 high-altitude weather balloons. The balloons traveled up to about 30 km (18.6 miles), slightly below the aurora borealis, carrying a specially designed payload built by graduate students at Texas A&M.
The payload included GoPros, the small, durable, wearable cameras built to shoot in extreme situations. The GoPro company helped Longmier to customize the cameras for capturing the aurora. They removed the filter that normally cuts out infrared and ultraviolet light, and modified the firmware to take quick 1-second exposures of the aurora. "We were able to get some stunning images of the aurora from the edge of space" Longmier says.
The aurora is caused by the collision of the solar wind (plasma emitted by the sun) with the outer layers of our atmosphere. When the charged particles interact with the oxygen and nitrogen atoms in the upper atmosphere, colors form. Excited oxygen shows up as red at the top of the aurora, but deeper into the atmosphere, where the air molecules are closer together, oxygen releases the familiar green light. Even lower into the atmosphere, at the bottom of particularly active auroras, nitrogen releases a bluish or purple light.
Longmier and colleagues hope that, in addition to creating cool visuals, their project will give them some new insights into the physics of the aurora. For example, the images they collect showing how the aurora behaves could help inform the design of a plasma sensor sensitive enough to measure conductivity in the upper atmosphere, where electrical charges are measured in nanoamps, or 1 billionth of an amp. "Whenever you measure 1 billionth of anything, it's really tricky to do," Longmier says.
The launches were part of a program called Project Aether that Longmier started as a post-doc three years ago, intended to give students a chance to design experiments for near-space environments. For the aurora experiment, the team of Longmier, several graduate and undergraduate students, and high school teachers wanted to try to get HD footage and pictures of the aurora simultaneously from three different perspectives, from the ground, the balloon, and the International Space Station. So Longmier had to time the launches to coincide with when the space station was in the vicinity. "The space station doesn't pass overhead but it does come within 800 miles on the ground track," he says.
But it wasn't easy to get the timing right. "During the first 10 days we were up here we got nothing. The electronics were freezing, the wind was wrong. The sort of saving grace was the students were completely enamored by what they were doing" Longmier says.
Then, on a recent Thursday night, things finally started going in the right direction. The wind was calm, the skies were clear, and the aurora was out in full force. "We got six balloons launched which had the opportunity to get really good results" Longmier says. The team then flew by helicopter into the roadless Alaskan wilderness to recover the equipment (they also used snowshoes, dogsleds, and snowmobiles while recovering other balloons).
Project Aether has launched hundreds of balloons carrying all kinds of scientific experiments, from graduate level to middle school. "We've done middle school experiments where they fly Peeps into space" Longmier says. "It's a nice way to do spacecraft measurements and spacecraft-like design, without building at the million-dollar level."
And most important, he says, it gets students excited about science. Longmier plans to expand Project Aether in the next year, helping educators around the country launch their own weather balloons from regional centers. | 0.811185 | 3.712643 |
The short answer is simple: No, the moon landings were not a
The long answer is a little more complex. We'll need to examine
some of the leading claims that Hoax Believers put forward and
explain why those claims are false or misleading.
1. The flags
"blow in the wind" - This is simply not true and stems from a
misunderstanding of how objects that are familiar to us here on
Earth behave in an unfamiliar environment. The moon has only 1/6th
the gravity of Earth and has no atmosphere. Because of these two
properties items do not behave on the moon the same as they do on
Earth, with regular gravity and an atmosphere.
1a. Lets take gravity first: with the light gravity of
the moon, the fabric of the flag is not pulled nearly as hard
towards the lunar surface as it would the surface of the Earth.
This allows the flag to "wave" around on the moon (from even the
slightest bump) much longer than it would the Earth.
1b. Secondly, the lack atmosphere makes a huge impact on
the motion of the fabric. For comparison, think of a swimming pool.
If you take a flag into a swimming pool and submerge it, then wave
it around, it's not going to flap back and forth. It's going to
move while you are moving your hand, but as soon as you stop moving
the flag will hang limp. This is because the friction of the water
stops the flag from waving. The same principle hold true between
the Earth and the moon. The Earth, with its dense atmosphere, is
the pool. Our air stops the flag from waving around with friction.
On the moon, no such friction exists; the flag is free to wave
around for much longer (after even the slightest bump) than it
would on Earth.
1c. As a side note, one of the common claims of Hoax
Believers is that the flag waves in the "breeze" created in the
wake of a passing astronaut, thereby proving there was atmosphere,
thereby proving it was a hoax. This is, again, false. Another
property of life on the moon is that there is no magnetic field to
mitigate the trillions of charged particles thrown by sun every
second. Those particles create strike the lunar surface, and
everything on the lunar surface, giving those items a small
electric charge. On Earth we call this Static Electricity, and it
is famous for making socks stick to clothing fresh out of the
clothes drier or making balloons rubbed on hair stick to the wall.
In the video of the flag mentioned above, the astronaut passes very
near the still flag. As he passes, the static charge on the flag is
drawn toward the astronaut as he passes, causing the flag to "wave
in his wake".
2. There are no
stars in the pictures - This is true, but not for the reasons
put forth by Hoax Believers. To understand this, you need to know a
little about how cameras work. When the shutter release on a camera
is pressed, the shutter opens for a fraction of a second, allowing
the light-sensitive material behind the shutter to be exposed. The
amount of light that is allowed through is controlled both by how
wide the shutter opens (aperture) and for how long it's open
(shutter speed). The brighter the object being photographed the
less light you want to let through to the film. Too much exposure
will create an unrecognizable photograph; you will simply see a
white blob. This is critical to understand because it is at the
heart of the "missing" stars.
The surface of the moon, in direct sunlight (as it was during
the Apollo missions), is very bright. So bright, in fact, that it
can create shadows on the Earth in the middle of the night from
238,000 miles away. That fact alone means any camera used on the
moon's surface must have the settings as such to no overexpose the
film. But the astronauts weren't just taking pictures of the moon;
they also took pictures of each other. The cameras used by the crew
were set up to take pictures of the lunar surface, other astronauts
in white spacesuits, in a bright white environment, in the middle
of the lunar morning, in direct sunlight. The fact that no stars
showed up in the images is to be expected. Had there been stars
there would have been more evidence of a hoax.
You can test this theory yourself. Tonight, grab your camera and
stand inside your house near the window with all the lights on (you
can even open the window to make sure there is no obstruction
between yourself and the stars). Now position something in front of
the window yet still inside, in direct lamp light. Using your
camera (it doesn't matter if you use the auto settings or change
the settings yourself) take a bunch of pictures of the object in
front of you (remember that object is your focus, you are trying to
get pictures of your vase, not the sky!). Now look at the images
and count the number of stars in your pictures. The sky behind the
well lit object in your house is black without stars, and that was
just using lamplight not direct sunlight.
Incidentally, there are pictures taken of stars by a crew on the
moon. Apollo 16 brought a special UV camera to the lunar surface
for the specific purpose of doing some astronomy. There are
hundreds of pictures of stars, just not in the pictures of the
bright lunar surface.
3. The crew would
have been killed by radiation - This is untrue and stems,
again, from a misunderstanding. The Apollo crew did indeed take a
dose of radiation; it just wasn't enough to kill them in the short
period of time they spent inside the radiation belt. Here are the
3a. The trajectory of the spacecraft was not a straight
line between the earth and the moon. It was arced. They did this in
order to avoid the densest area of radiation in the van Allen
3b. At the speed the capsule was travelling, the crew
spent far less time inside the belts than the amount of time needed
to give them a lethal dose.
3c. There are different types of radiation, wave and
particle. Wave radiation requires the most shielding, sometimes
very thick shielding depending on the wavelength (for example, UV
radiation is wave radiation, but can be blocked by a thin sheet of
plastic like sunglasses, whereas gamma radiation requires several
inches of lead). Particle radiation, in comparison, is much easier
to shield against. Alpha particles can't even penetrate the top
layer of dead skin cells on the human body. Proton and Beta
particles can both be shielded against using a centimeter or so
High Density Polyethylene (HDPE). Plastic.
3d. The Van Allen belts consist primarily of Proton
Particle radiation, which as noted in point 3c above, can be
effectively shielded against using HDPE plastic.
3e. The Command Module was built using materials that
could shield particle radiation
3f. Summary: The mission was planned to go through the
weakest, least dense section of radiation, in the shortest amount
of time, with shielding built into the module. NASA spent a lot of
time and money mitigating the problems presented by the radiation
belts. The money was well spent.
4. The crew was
sometimes lit from the front even when the sun was behind them
proving it was shot in a
studio - The shadow-side of objects often were lit, but not for
the reasons put forth by Hoax Believers. As discussed in bullet
point 1, the moon, and the suit the astronauts wore, was very
bright. In professional photography shoots, the photographer's
assistant uses a reflective fabric screen to cast light on the
model's face when s/he is not directly lit. On the moon, this same
effect is provided, inadvertently, by both the moon's surface and
in some cases by the astronaut taking the picture. The sun's light,
coming from behind the astronaut or item being photographed,
reflects off of the surface between the photographer and the
object, casting light on the shadowed side of the item of
5. All the pictures were perfectly framed, proving the shots
were not from cameras mounted to the chest of the spacesuit -
This is only partially true; many pictures were perfectly framed.
However, anybody claiming all the pictures were perfect has
not looked through the Apollo photo catalog. There are also
pictures one would expect from chest-mounted cameras, such as
pictures taken at odd angles, or pictures of the crew members boot,
or pictures that are simply unrecognizable. Secondly, the pictures
that are perfect weren't created by accident. The crew spent many
hours training to use a chest-mounted camera. They learned how to
position their bodies in order to perfectly capture what they
trying to capture. The training was successful.
6. Astronauts' replies to questions
asked over the radio were immediate. - This is not true and one
of the easiest claims to debunk; all anybody needs to do is listen
to the audio themselves on the Apollo Lunar Surface Journal. Due to
the distance of the moon radio waves take ~1.5 seconds to reach the
lunar crew, and then another ~1.5 seconds to return. The actual
time is slightly less than 3 seconds. The audio of these missions
were recorded back on Earth in Houston, which means the recordings
are made from the Mission Controllers point of view. Here is an
example from the Apollo 11 transcript which shows the delay
affecting Buzz Aldrin:
102:26:55 Aldrin: And, Houston, we got a 500 alarm (code)
early in the program. Went to Descent 1, proceeded on it, and we're
back at Auto again. Over.
102:27:06 Duke: Roger. We saw that, Buzz. Thank you much.
102:27:09 Aldrin: Rog. I say again...(Listens) Okay. That
wasn't an alarm; that was a code. Okay.
Charlie Duke (CapCom for the first Lunar landing) obviously
started speaking before Buzz Aldrin started to repeat himself, but
because of the time delay Buzz didn't hear him until the signal
reached the moon wherein Buzz heard the answer, paused, and
affirmed he had heard. The actual mission transcripts and audio are
full of this type of
overspeak and delay. Don't listen to cherry-picked audio by Hoax
Believers; don't even take my word for it. Go the Apollo Lunar
Surface Journal and listen/read for yourself.
8. Shadows diverge on
the moon proving there were two light sources - This is not
true, well the two light sources part anyway. There are many
examples of this around the web and it was also shown to be a
natural phenomenon by the Mythbusters. Essentially when the ground
is uneven and objects are casting shadows are on different sections
of the uneven ground the shadows do not lie in parallel lines.
Again, you can test this yourself. Find a parking lot or a park (in
daylight where the sun is the only light source) with a sloped
ground that changes between lamp posts. Note the shadows on the
ground. They will not be parallel.
9. The flag shines bright on both sides
as if in a spotlight - Nylon is a thin material. When the sun
is behind the flag in photographs the light is able to go through
the nylon and make the flag visible. This has the appearance of a
glowing flag, or a flag that is lit from both sides when in fact it
is either lit from the front or the sunlight is passing through the
nylon material backlighting the flag.
10. In the 60's and 70's
we didn't have the technology to go to the moon - First we must
remember that NASA was on the cutting edge of technology in the
1950s and 1960s. They had an enormous budget and attracted the top
scientists in the country. At the height of the Apollo project
there were half a million scientists and engineers working on
different aspects of the missions.
In a larger sense, it's easy to lose touch with technology. That
is, it's easy to look back to the past and wonder how we ever got
along without the miracles we enjoy today. We sit at our gigahertz
computers and forget that there was a time when an eight megahertz
computer was pretty cool.
Just because we rely today on one particular technology or
another in order to do some hard thing, doesn't mean it was
impossible to do that thing before our modern technology was
invented. For example, nearly all modern clocks use a real-time
clock integrated circuit. It does all the timekeeping. In the 1970s
we had analog clocks that used synchronous electric motors to
precisely drive mechanical gears. Would it be correct to say that
accurate timekeeping was impossible before that integrated chip? Of
course not. Similarly, old mechanical action clocks used pendulums
and springs to keep surprisingly accurate time.
What's the lesson? Just because we choose to use some particular
technology today to solve a problem doesn't mean that problem was
unsolvable before we had today's technology. Apollo engineers
didn't have high-speed portable computers to make self-contained
guidance systems, so they just built guidance systems differently.
The computer was only one part of the guidance system. When John
Glenn orbited the earth in his Mercury capsule, there were
no computers with him.
Yet his capsule was fully automated.
The moral of the story is that people can be very ingenious
working with limited tools.
11. NASA has said we
can't go to the moon today because the technology does not
exist - This is partially true, but not for the reasons Hoax
Believers claim. At this point it's been over 40 years since the
first moon landing and nearly 40 years since the last Apollo
mission flew. The scientists and engineers that designed and built
the Apollo spacecraft have long since retired or died and the plans
and documentation that were created to build the Apollo have been
destroyed or lost (keep in mind that the spacecraft were built by
aircraft companies; once the missions were over there was no need
to keep the blueprints, for them it was back to business as usual).
The specialized tools and the materials infrastructure that was
built specifically for Apollo were all dismantled at the end of the
program. As such, were NASA asked to build another Apollo capsule
tomorrow they could not do it. This does not mean that NASA
engineers could not build a new spacecraft. They can, and likely
will, but things will be different.
During the Apollo days the entire nation was behind the program.
NASA had a huge budget and some of the best and brightest
scientists and engineers. This is not true today. NASA's budget is
less than 1% of the Department of Defense budget and, with space
travel no longer being the height of technology, the best and
brightest often go elsewhere. All this will make it difficult to
return to the moon, but it in no way proves we didn't go the first
12. A in a photograph taken on the moon
has the letter "C" on it just like prop masters do in Hollywood
-In 2001 Steve Troy of Lunaranomalies.com undertook a lengthy
investigation. After obtaining transparencies from different
sources connected with NASA, he failed to see the mark either on
the masters used prior to 1997 or on the new masters. Yet the
photos on official NASA web sites clearly show it. Following up
with the Lunar and Planetary Institute (LPI) in Houston, they
discovered that one of the prints in their collection was the
source of the mark. At some point that print had been scanned and
has since been widely distributed on the Internet. Troy and LPI
officials studied the print under a microscope and discovered that
it was indeed far more likely to be a hair or other fiber on the
photographic paper onto which AS16-107-17446 had been printed. A
secondary mark that appears to be a shadow is clearly visible under
the top portion of the mark.
14. The thrust from the
LM descent engine would have dug a crater under the LM proving the
landing was faked - This is not true, and quite simple. The LM
Descent engine had a throttle control similar to your car. You
wouldn't pull your car into your garage with the gas pedal pressed
to the floor and the Apollo astronauts didn't land with their
engine on full throttle. In order to keep the LM on a slow descent
the amount of thrust coming from the engine had to be nearly equal
to the weight of the spacecraft being tugged on by the moon's
gravity. At the time of the actual touchdown, the LM "weighed"
~2600 pounds. In order the keep from crashing the LM engine only
had to produce ~2600 lbs of thrust. Hardly enough to cause a crater
(keep in mind that, on Earth, helicopters and Harrier jets produce
tens of thousands of pounds of thrust, enough to lift multiple tons
of machinery off the ground. None of them seem to create craters
even in the loosely packed sand of the desert).
15. Finally, some things to keep in mind: the U.S.S.R.
was our enemy during the Apollo era. We were embroiled in the Cold
War, we were each heavily invested in the Space Race to the tune of
billions of dollars, and we each had the world watching us intently
to see who would "win". The U.S.S.R. watched our moon-shot with
intense interest. For them, failure on our part would prove they
were the best/strongest/most advanced nation. They were desperate
for our failure. Had the US faked going to the moon it would have
been incredibly easy to spot by a nation whose scientists and
engineers were every bit as good as their US equivalents. They
tracked the command module to and from the Earth, they listened to
the broadcasts of the crew walking on the surface, they have
examined the samples returned by those astronauts. At every step,
the U.S.S.R., the country most invested in the US's failure, has
congratulated us for a job well done. To think we could have
somehow bought their silence with so much at stake is, quite
There are many, many more theories put forward than those
presented here. Each of them has an answer, each of them can be,
and is, proven to be false. When trying to determine whether or not
something is true, it is important to look at who is saying it.
People that are trying to prove NASA did go to the moon are often
authors trying to sell books. It is important for them to entice
you, to make you want more information; because the more you want
to know the more books they sell. They don't want to just one book,
though, they want to keep writing. They need you to get sucked in
so they can continue to dish out their "discoveries" over the
years, selling more and more books. They have no interest in the
NASA doesn't try to convince you they went to the moon. They're
not interested in trying to prove something because they don't have
to. The people making the extraordinary claim are burdened with
proving it. NASA has provided all the documentation, all the
pictures, all the plans, everything you could want, to research
this yourself. The people writing books don't want you to do the
research; they want you to believe they had already done it. It's
fine to be skeptical of NASA. Question everything they tell you.
Just make sure you question the Hoax proponents as thoroughly. | 0.800508 | 3.044276 |
Written by Paul Litely at Paullitely.com
We are being told daily that carbon dioxide, and in particular, carbon dioxide that is man-made, controls the Earths climate in a direct fashion. However, all of the predictions of rapid dramatic warming in proportion to rising carbon dioxide have not been fulfilled. What we are seeing instead is increasing doses of deepened global cooling in winter, and shortened summers. Simply watch yourself for the mechanism of increasing cloudiness, rain, and snow. It validates the predictions of global cooling being made by more and more climate experts.
This global cooling will be obvious to all by the year 2021, despite continuing increases in atmospheric carbon dioxide . In fact it is the cycles of the ocean currents, the motion of the planets and their effect on the sun, as well as the position of our solar system in our galaxy, the Milky Way, that are the largest, most consistent determinants of earths climate.
Carbon dioxide does not lead global warming, but instead follows it by hundreds of years, and is such a tiny effect on Earth’s climate as to be insignificant. The repetitive short cycles that describe the earths climate change over hundreds of years have been modeled successfully by Theodore Landscheidt, Carl Smith, And Geoff Sharp. They describe the cycles in relation to the motion of the planets in our Solar system. However, the mechanism was described by other researchers and theorists. Cosmic rays make clouds on Earth, and the Sun protects us from cosmic rays when it is active as shown by sunspots.
The longer cycles of warm periods and long deep Ice ages That correspond to the approximate 25,000 year Mayan calendar can be accounted for by the same indirect solar mechanism that works over hundreds of years. The great Iceages are Caused by the gross exposure we have to cosmic rays from the black hole at the center of our Milky Way Galaxy.. The limited capacity of our Sun to protect us from cloud-forming cosmic rays is overwhelmed as the solar system oscilates out of and through the protective plane of our Milky Way galaxy. Approximately 25,000 years in protection, and 75,000 years out in the open. The Mayans knew the cycles.
The crime of the millennium is that we are being told to prepare for uncomfortable heat, when we are in fact entering a period of deadly cold for at least 50 years, possibly longer, then warming for a while before rolling into another 75,000 year Ice Age at the end of this 25,000 year warm period. The warm period ended with the most recent Mayan calendar..
This essay titled “How in the Universe…” is my original compilation of 10 years of study on earths climate change theories and factual data, with some intuition on how to link it all together in a coherent and consistent “Global” model. This model works going back in Time. Global Warming theory quickly breaks down when applied to the record of Earth’s past Clomate changes. How can it be useful for predicting the future, if it cannot predict the past? It just can’t, and all of its predictions have failed to appear.
The details of my analysis and accumulation of facts are what follows. No matter, if you understand the details or not, what you can expect is more clouds, rain, and snow. It will soon be obvious to all, as these definite motions of our planets and our complete solar system go on repeating themselves, as they have for many millions of years. Watch for it with your own senses. Take note of it. All the while we will be getting dramatically colder as carbon dioxide continues to rise, with no effect, regardless of human contributions.
The worthy “Global warming” campaign objective is to reduce the accumulation of wealth and pollution from fossil fuels. It is being realized to a degree. However the lost opportunity to prepare for deadly cold, and the resulting loss of easy food cultivation, may not be worth it, Hundreds of thousands, perhaps millions of humans will die because our leaders cling to a failed, but politically convenient, and financially profitable theory about Earths climate… “Global Warming” From Carbon Dioxide.
NASA has recently altered its previously published temperature records over the last 100 years to cool the past and warm the present on paper. The evidence is clear and undeniable. NASA did it more than once to hide the reality of global cooling, as happened from 1949 to 1984. There are billions of dollars from annual international fundraisers and individual government programs at stake. Those who benefit will not loosen their grip easily. Will they tell us that Carbon Dioxide is now cooling us to keep it going? Yes, it is even likely.
Meanwhile, a Deadly Cold future goes unprepared for. Watch, but don’t wait to do your own personal preparations. Stockpile food. Stay near the ocean and it’s warming influence, and it’s abundant seafood. Call out our leaders as they deny the reality of cooling vs the predicted warming as Carbon Dioxide continues to rise in the atmosphere.
How in the universe do we connect weather or climate event to Human Caused CO2? Atmospheric Carbon Dioxide has been increasing for the last 7,000 years, while the Earth’s Average Temperature has been Decreasing for the last 3,000 years, according to Ice Cores.
Humans contribute less than 10% of the recent 10% rise in CO2. CO2 is only 1% of the Greenhouse gas concentration in the atmosphere. Water Vapor is 97% of the greenhouse gas in Earth’s Atmosphere and that makes Clouds, rain, and snow with no help from CO2. Vast amounts of heat is absorbed and released as water evaporates, rises, and condenses and freezes. This change in what Water looks like is called “Changing Phases”. It is still H2O as liquid water, a water vapor gas, or solid ice.
Carbon Dioxide (CO2) does not change phases to solid or liquid at Earthly Temperatures and Pressures. It freezes at minus 109 degrees Fahrenheit. It does not become a liquid, but goes directly from ice to a gas. You have seen it as “Dry Ice”. CO2 cannot store an release such vast amounts of heat energy as water does. It therefore cannot dominate as a greenhouse gas when 97% of earth’s greenhouse gas is water vapor. Global Warming Models do not attempt to model Water as liquid or vapor, or ice because it is “too complicated”, and the theorists admit it. It is also too powerful, so it dominates the movement of heat, and upsets Global Warming Theory models.. So, lets just look at water as a vapor, as a greenhouse gas like CO2, and compare the two. How do they act when the sun shines on them?
- Note the area on the graph below labeled “Infrared” this is the Sun’s. radiation that HEATS surfaces that don’t reflect it. Note that CO2 is only connected to a narrow part of the Infrared (heating) spectrum, while Water Vapor connects across most of it. The red part of the graph is the bandwidth of the Sun’s Solar Irradiance (Brightness). The blue part of the graph is the bandwidth of stored invisible heat radiation that goes back upward from the Earth’s surface. That heat originally came from daytime sunshine. The grey parts of the graph are where the various greenhouse gasses absorb and then re-radiate energy. Note the “Hole” in the Water Vapor Grey area just under the Blue. This is the only big part of stored surface heat that is NOT absorbed by water vapor or consumed by evaporation of water to make water vapor. Note that CO2 does nothing to stop that blue heat energy that escapes upward from the Surface of the Earth except for the right 1/4 of that blue peak. This clearly shows that ONLY water vapor is an important greenhouse gas. CO2 is just a tiny one-hump player, and can Never dominate or control the heating of water vapor. This should be enough proof that CO2 is powerless, but there is much much more.
CO2 is such a weak Greenhouse gas that it is insignificant regardless of the amount of Solar Radiation spectrum it interacts with. Water Vapor rules on its own as a greenhouse gas.
Water vapor is vastly more important in moving heat for another reason. Water Vapor changes state to water or ice, and back from water or ice, with huge Quantum (instant) heat absorption and release. Water vapor also condenses into liquid water when it saturates the air at a given temperature. On the other hand, CO2 precipitates directly to a solid, or sublimates directly to a gas, without passing through a liquid state, and does this at MINUS 109 degrees Farenheit under normal atmospheric temperature and pressure ranges. CO2 NEVER changes state to ice near the Earth’s surface because the Earth’s surface or atmosphere Never gets down to Minus 109 Degrees. CO2 therefore cannot move heat energy in the most important way possible.
Water Vapor at lower altitude temperature and pressure changes state into liquid water, making clouds. Clouds are a very high efficiency reflector for Solar infrared (Heating) radiant energy, shading water and land with 90% efficiency. However clouds do let non-heating ultraviolet radiation through, giving you a sunburn on a Cloudy day. Water vapor rises because it is lighter than air. When it rises up into the cold upper air, water vapor condenses into clouds, rain, and snow. When this happens, Clouds radiate huge amounts of heat into space from the condensation of water vapor to water, rain, and ice. Global Surface Temperatures decline with increased Cloudiness because of reflecting shade and the transport of heat by evaporation from the surface to form clouds that radiate heat energy into space.
This plot and graph of observed temperatures vs cloudy days around the world clearly shows that more clouds are associated with colder temperatures.
Here is the recent relationship between Cloud Cover (Green) and Earth’s Surface Temperature (Blue). It makes sense, doesn’t it? More clouds = cooling. We have all felt the effects.
Huge amounts of Solar radiant energy are needed every day to keep this negative feedback from going to cold. Compare the graph of recent Global Cloudiness below with the next graph of recent Global Temperature. Flip it over, and see if it fits the temperature graph better than the graph of CO2. There is No contest as the CO2 line does not follow measured temperatures. Meanwhile, temperatures clearly move directly opposite the cloudiness.
Does the Graph of Cloud Cover explain Global Temperature better than CO2?
Global Temperatures move opposite to Global Cloud Cover. Clouds are condensation from Water Vapor. Clouds release heat into space when they form. Water vapor gets this heat by evaporation, cooling the Earth’s surface. Clouds are 90% efficient at reflecting the sun’s heating radiation into space. CO2 is an orphan. CO2 has no significant role. Water Vapor is not controlled by CO2. Global Water Vapor has stayed almost constant recently, except it has declined at higher altitudes. (See Top line in the graph below) Higher altitudes are where CO2 Global Warming theory said Water Vapor would increase to do more Greenhouse warming because heat from CO2 put it there. That is the most basic Global Warming assumption. It is clearly not happening. Neither is the predicted warming.
It is apparent that the increased Cloud Cover does not dent the amount of Water Vapor in the atmosphere at lower altitudes (Bottom two lines). This makes sense, because the air has to be saturated with 100% humidity for clouds to form. The excess falls out as rain or snow. Humidity cannot get higher than 100%. Any added moisture in the air just drops out as clouds, rain, or snow. Clouds occur almost exclusively at lower altitudes, when the air cools and cannot hold any more water vapor. The excess becomes clouds and rain and ice. In the chart above, the amount of water vapor at lower altitudes (bottom two lines) is almost constant, increasing slowly. The Greenhouse effect of Water Vapor is therefore fairly constant now, on average. The only variable here is the amount of water vapor rising, making clouds, and falling down.
Global Surface temperatures are controlled by the extent of Cloud Cover, since the Sun’s “Irradiance” is very constant, and only varies by less than 1/4%. Clouds form when the sun heats the Earth’s surfaces, including oceans, and the water vapor generated rises to cooler altitudes to make clouds. When Cloud Cover is widespread, the Sun’s Energy is reflected back into space with up to 90% efficiency. When Cloud Cover is sparce, the land and seas can absorb the Sun’s Energy and the Earth warms. Clouds act as “Venetian Blinds” to block or allow the Sun’s Energy through to heat the land and seas. Here is a graph showing that relationship between Solar Energy being sent back into space (Red Line) and the Earth’s Global Temperature (Blue Line). They are opposites. It seems the prime driver of Global Temperatures is clearly Cloud Cover.
When Cloudiness increases, Earth’s temperature decreases. When cloudiness decreases, Earth’s temperature increases. They move oppositely.
There is now strong evidence that the Sun controls Cloud Cover indirectly by controlling the amount of Cosmic Rays that reach the Earth to make clouds.
Here is a graph of that very striking inverse (opposite) relationship of Solar Activity as measured by sunspots (Blue), and historic cosmic rays. (Red).
It has been shown experimentally in Cloud Chambers, that high energy protons and neutrons that ARE Cosmic Rays, will make cloud formation easier. The term for this is Nucleation. Periods of high sunspot. Activity make strong solar winds and magnetic fields that blow away Cosmic rays headed for Earth. So, It appears that the Sunspot cycles contribute strongly to the Earth’s global temperature cycles by this indirect method. More sunspots, less Cosmic Rays and less clouds to block the Sun from warming the Earth’s surfaces. Less Sunspots, and more Cosmic Rays get through to make clouds form easier, making shade and reflecting the Sun’s energy back into space, cooling the Earth’s surfaces. So THAT is how the Sun indirectly, but strongly, controls the Earth’s Global Temperature, not by changing the strength of sunlight. The Global warming models have NO accounting for this indirect control of clouds by the Sun, but simply say the intensity of sunshine (irradiance) is almost constant.
Here is how the sun’s control of clouds works according to one of the discoverers, Professor Henrik Svensmark.
There is other strong evidence that the Sun’s Activity, as evidenced by Sunspots, controls the Earth’s Global Temperature. During two periods in the last 400 years the sun’s activity went down for several 11-year cycles in a row, resulting in periods of deadly cold for the Earth and Humans. The “Maunder Minimum” lasted for about 60 years with almost no sunspots, a time known as the “Little Ice Age”. Another dip in the Sun’s activity occurred about 200 years ago, known as the “Dalton Minimum”. Although not as long or deep, it, too resulted in thousands of people dying of freezing cold or starvation from not being able to grow crops because of very long winters. One year of low solar activity had no summer at all. American Indians recall a year of snow on the ground in Florida.
It works in reverse, too. In recent times, we have had high numbers of Sunspots, and that has resulted in the “Modern Maximum”, where winters are reasonably short and summers long enough to grow food, with some uncomfortably warm periods in the 1890’s and 1930’s, much warmer than today. Note: The hot 1930’s are being denied and covered up by official record keepers (see my blog with detailed graphs). Worldwide Temperature records have been manipulated to lower the temperatures shown in the first half of the 1900s and to raise the temperatures shown since then up to today to make recent times to appear warmer. See detailed graphs in the Paullitely.com Blog entry beginning with HadCRUT.
Here below is a graph of the Solar Activity sunspot cycles going back 400 years. See the notations for the deadly little ice ages and the recent Modern Maximum warm period where we have thrived.
Although we do not have sunspot records back that far, it is important to see that ice cores show the Earth’s surface temperatures were much much warmer than today for years about 1100 to 1300 AD. This was the time of enlightenment and Renaissance, when food was plenty and cold weather did not kill in Europe. see chart below. Of course, humans did not contribute much CO2 back then, so human made CO2 could not have caused it.
See the colored chart below of recent Sunspot measurements. The Last two Sunspot cycles through today are numbered #23 and #24. They have peaks that are lower than the peak before by 30% each time. The current Sunspot peak #24 is delayed, and has a “Double Hump”. This same formation happened at the beginning of the long cold Maunder Minimum with almost no sunspots that lasted for 60 years of very cold temperatures on Earth. There is a strong possibility we are headed there again right now, to a new mini-iceage, as predicted in 1989 by Theodor Landscheidt. If so, we are not looking at a “Globalwarming” future, but instead, an extended “Globalcooling” period that will be deadly, as it was each of the last times the sun got stuck at low sunspot activity.
Look closely at at this graph of the declining Sunspot cycles we are in. This pattern was seen going into the Maunder Minimum, and the next major peak took 60 years to appear, and we froze. We don’t know that will happen, but it is likely the next peak could be lower than this one we are in – Cycle 24.
We are now at the right hand edge of the roller coaster ride, headed for the bottom again. We don’t know if there is a Cycle #25 hump coming, or how big it may be. What we do know is that these low solar activity cycles come around about every 200 years as the Sun’s magnetic poles get “Stuck” in neutral or lock on to each other when trying to switch places. This is happening now, right on time, according to Theodor Landscheidt, and the Sun has not finished flipping poles as of 2016. In 5 years, it could get stuck trying to flip. It surely looks to many, many of us like deadly cold weather is ahead for some time, as in the past mini ice ages. Evidence of Global Cooling is all around us.
Before you dismiss the following facts, read the other posts on this site regarding how ALL claims of Global Warming are based on Temperature Records that have been changed to MAKE warming while the raw measurements show cooling. Polar ice is nearly back to normal in 2016. Antarctic ice is the highest in 35 years. Greenland did not seen a summer in 2015 and has added ice over 85% of its surface. Sidney Australia had its first snow since 1835 in this year, 2015.
The last few years have brought more and more polar ice, Colder and longer Winters, and Record low temperatures, even in the Summer. The Modern Little Ice Age may last for 20 years or it may go on for 60 years as it did in the 1600’s. Each new Solar Cycle from high to low takes 11 years from the last one. We will see continued cooling at least that long from now. The cold caused by lower and lower peaks at Sunspot Cycle #23 and #24 are still unfolding. it can take 11 years for the Earth to change temperature direction and follow the sun This current period of low Solar Activity is called the Landscheidt Grand Minimum, for Theodor Landscheidt, who predicted it back in 1989. He accurately predicted global weather from the Sun’s declining activity and ocean currents. Here is an article on that by Landscheidt himself:
The long ice ages can also be explained. What is worrying some scientists, and me, is what if the amount of Cosmic Rays heading for Earth increase so they are very very intense – too much for the Sun to block? The Sun’s solar winds and magnetic fields can only divert just so much of the incoming cosmic rays. Very intense cosmic ray exposure may overcome the Sun’s protection completely. It appears that this is what happens to make the deep 100,000 Year ice ages that have occurred on Earth. Here is a graph of the history going back 420,000 Years. Note the long deep ice ages, and the short warm peaks. We are right now just a speck on the right side of the red box on a warm peak now, ready to fall back down into a deep ice age, as before.
Here is a magnification of that red box, showing that we are at the end of it. Temperatures have been declining for the last 3000 years. If we fall off that cliff, the little ice ages we are discussing here will be insignificant. Sheer survival of species, including humans, will be at great risk. The cost of simply keeping warm and finding/making food will be staggering, and societies will be shredded. The 125,000 year Mayan Calendar has just reset.
An explanation for the great ice ages seems to be as follows, based on astronomy observations. The solar system “Bobs” up and down through the plane of our Galaxy, the “Milky Way”. Right now, we are in the plane of the disc. Because we cannot see very far through the thick middle layer, we are protected from most of the Cosmic rays coming from the other stars in the Milky Way and the supermassive black hole at its center. Our exposure is blocked by nearby stars and gas clouds. This protection only lasts for about 13,000 years, Then the Solar System moves out to clear space where cosmic rays from most of the Milky Way Galaxy and beyond can reach us unobstructed.
We seem to be moving out of safety and into the dense stream of cosmic rays that are so strong that our Sun cannot block them. As that happens, the Earth will rapidly cloud over and cool, making the next Ice Age. Ice Ages last about 100,000 years. This effect compounds the Sun’s current inactivity. The little ice age we may be entering may just tip over right into the next grand ice age for 100,000 years. As a result, we may see a very, very rapid descent into dense cloud cover and even more intense, deadly cold. The Landsheidt Minimum little ice age we are in now will most likely reach the coldest by 2025, and it could stay there for decades as it did in the Maunder Minimum. OR, the sun may come unstuck from it’s state of no magnetic poles and help us warm up first. Either way, we are already on the way down the roller coaster ramp for a period of significant cooling.
There is a delay of the effect of the sun’s cycles and the Earth’s cooling of approximately one solar cycle. Heating took time. Cooling takes time. Two lower and lower solar cycles have just occurred. We have not seen the full effects of the past two lower solar cycles. We will not see the full effects for another 11 to 20 years. Even a strong recovery of the Sun, after it finishes flipping North and South magnetic poles, may shield us for a while longer, but it seems it will eventually be overpowered by intense cosmic rays.
Here is an artists representation of the “Bobbing” of the Earth and Solar System through the plane of the Milky Way. It takes approximately 25,000 years to pass through the central disk of the Milky Way, then about 100,000 years to return. The 25,000 years corresponds to the length of the Mayan Calendar, that coincidentally just ended, along with the current warm period on Earth. During that passage, the Disk of the Milky Way itself shields us from the most intense cosmic rays, and the Sun can deflect them when the Sun is Active with Sunspots. During the next approximate 100,000 years, the solar system is outside the central disk of the Milky Way, and is exposed to intense Cosmic Rays from the Ultra-Massive Black Hole at the center of the Milky Way, as well as the entire plane of other active radiant objects. During this time, the Sun is not powerful enough to deflect this intense bombardment of Earth, and Earth clouds over into a Major Ice Age until the Solar System returns to the protection of the central Disk of the Milky Way.
There is a video on YouTube that goes with this image. It is accompanied by dire warnings of the social consequences, and correlations with the Mayan Calendar.
Tipping into the next Major Ice Age will not be abrupt because it takes thousands of years. However, tipping into the Landscheidt Mini Ice Age, as we are today, will be very abrupt if the Maunder Minimum is being repeated as Landscheidt, and Carl Smith and Geoff Sharp predicted. The Maunder Minimum descended in a matter of a few decades with a pattern of declining Sunspot activity that is being ecoed today.
It is deadly cold we should be preparing for, not a future of Global Warming and uncomfortable warmth. The evidence will be mounting undeniably in the next few years. The “Maunder Minimum” from 1645 to 1715 was accompanied by wars, starvation, plagues and persecution by extremists who believed our God had been offended, so he made it deadly cold. European Rivers froze over annually, including the Thames in England. Snow stuck to the ground for most of the year. The sun was obscured by clouds for long periods. It is known as “The Dark Ages” because it was dark. We may be WISHING FOR WARMING as happened in the years 1100 to 1300, whose benefit was the ability to grow food further towards the Earth’s Poles. The Earth was as much as two degrees warmer than now. There were Vineyards in England. The street signs remain today celebrating them. Food was abundant, and disease was less prevalent. Wars were infrequent. Live was easier. It is known as the “Medieval Warm Period”, and “The Age of Enlightenment”. Warmth is good. Cold is deadly.
In the meantime, the Atmosphere is getting richer in CO2, and that is plant food. Canadians direct the exhaust from their propane heaters into their greenhouses to increase the CO2 and double plant growth during their short Summers. Ironically, today’s rising CO2 levels have increased forest growth on Earth. More CO2 can make it easier to grow food during the upcoming deadly cold with very short summers. CO2 is not a poison, or we would not put it into our soft drinks and carbonated water and greenhouses.
Official Global Warming model temperatures closely follow the amount of Carbon Dioxide in the atmosphere. It is a straight line for most of the last 1500 years. How does it line up with Earths actual temperatures over the last 1500 years?
Click to enlarge the graph. Blue Is the IPCC model that uses CO2 to graph temperature changes. Since CO2 rose steadily and evenly, of course the model will produce the same steady graph since it assumes CO2 controls Global Temperature. The Red line is the actual temperature changes from ice core sample measurements and recent Satellite measurements. The IPCC Models have ironed out natural temperature changes in favor of showing a nearly straight history with a recent upturn. Why? What do you believe? This is the infamous “Hockey Stick” Global Temperature curve in Blue. in Red, is the actual temperature curve from Ice Core Research, NOT from models. THE IPCC MODELS CANNOT PREDICT THE PAST… SO HOW CAN THEY PREDICT THE FUTURE?
High levels of CO2 have to be very high to be dangerous to humans. Submarines and the International. Space station keep CO2 levels as high as 4,000 parts par million, or 10 times our 400 ppm atmospheric CO2 today. Our breath can be 10 times higher, at 40,000 ppm when we exhale. CO2 is not the Devil. It is a green plant’s best friend along with water and sunlight.
The grand experiment of looking for proof of Global Warming predictions in nature has failed so miserably that the promoters of the story have to alter raw historic records and MAKE warming to keep fundraising and salaries and grants totaling about $1Billion per day worldwide. Aside from encouraging solar and wind power at great expense with government subsidies, We get NOTHING for it. We get inconveniences and more expensive basics.. Food, energy, and shelter, so the poorest suffer the most. Promoters of Global Warming theory refuse to continue to refer to their position as what it is: CO2 Globalwarming. That is their basic claim. They now insist that we are seeing “Climate Change”, with the assumption that humans are causing it. They have abandoned the Warming label, because it is not happening except by their adjustments to raw temperature data, as seen in the next chart below. Supporters of the Global Warming models (NOAA, USHCN) have even adjusted historic PUBLISHED temperature data down in the past and up in recent times to track with the increase in atmospheric Carbon Dioxide.
Soon, we will have to Avoid using the term ClimateChange, because we now need that term for the inescapable little ice age we have entered. We really could use some Globalwarming after all, but I would not not count on it, from what I can see.
Environmentalism is a wonderful thing, and I am an avid environmentalist. That is why I have studied this Global Warming subject for Ten years. Wasteful fundraising to make or stop the weather is not a good thing. It is literally impossible for humans to change the weather, but $1billion per day pays those who say they can. Imagine what we could do to make life better for our fellow humans, animals, plants and our lovely planet with that money. Instead, it is being wasted where it makes no positive difference. Watch for the next United Nations IPCC fundraiser and their outrageous forecasts that have not come true. There has been no global warming for 20 years, and humans did not stop it. It just did not happen as they predicted. Instead of excuses, we need a revised model, or what are they being paid for? Meanwhile, we should at least be using some or most of that money to prepare for what is really coming, and has started… deadly cold. The survival of millions of people will depend upon it. Reality is pressing ahead. | 0.839725 | 3.19293 |
If We Had No Moon
|SMART-1 principal scientist Bernard Foing.
Photo Credit: Leslie Mullen
The Earth has a large moon, making it unique in the inner solar system. Mercury and Venus have no moons, and Mars has only two small asteroid-sized objects orbiting it. In this essay, the father of the SMART-1 lunar mission, Bernard Foing of the European Space Agency, looks at the effect the Moon has had on the Earth, and explores how different our world would be if we had no planetary companion. Would life have evolved differently, or even appeared on Earth without the Moon?
If We Had No Moon
An essay by Bernard Foing
If the time of Earth’s existence was condensed into a 24-hour clock, the moon formation event occurred just 10 minutes after the Earth was born. The Earth formed 4.56 billion years ago, and the Moon formed about 30 million years later. At that time, the Earth was a magma ocean. An impactor about the size of Mars struck the Earth at an oblique angle, and removed some of the magmatic mantle. This mantle was put in orbit around the Earth, together with some of the debris from the impactor itself, and this material eventually formed the Moon.
|Artist’s representation of the moon formation event. Copyright Fahad Sulehria, 2005, www.novacelestia.com|
When the Moon first formed, it was very close to the Earth. It was possibly only 20 to 30 thousands of kilometers away, and it would have looked extremely large in the sky, at least 20 to 10 times bigger. But there were no living creatures on the Earth at that time to witness this beautiful scene.
The tidal effect of a body increases as a cube of the distance, so the effect of the Moon’s tidal forcing on the Earth was extremely high at this time, to the point that the early magma ocean was affected. This provided some additional energy to the heating from radioactive elements present, but after the radiogenic heating decayed, the Moon still was a source of heating that may have had some geological effect, keeping the Earth’s magma hot and perhaps forcing additional convection in the Earth’s mantle.
After the Earth started to cool, the first crust started to float on top of the magma. During this period the Earth was subjected to increased meteor bombardment. The bombardment had been very intense at the beginning of the solar system and then had started to decline, but about 500 million years after the birth of the Earth, or about 2 hours and 40 minutes into our clock of 24 hours, there was a burst of impactors. This lasted for about hundred million years, and we call this “the late heavy bombardment.” Many of the large basins on the Moon are evidence of this late heavy bombardment period. In this way, the Moon is a history book for the inner solar system and the Earth. We have studied these basins with the SMART-1 mission.
|The Moon’s heavily cratered surface is evidence of the many meteorite impacts that occurred in the inner solar system during the late heavy bombardment period.
The Earth was hit more often than the Moon, however, because Earth is larger and has more gravity. This increased gravity also caused the impactors to be accelerated to higher velocities towards the Earth. That must have been a catastrophic time to be here. So many bombardments would have sterilized the planet. If life had appeared before this period, it would have been extinguished unless it found a way to retreat into niches where it could be protected from these global catastrophes.
When some of these impactors hit the Earth, the explosion caused rocks and dirt from Earth to shoot up and away from our planet. Some of that projected material flew all over the solar system, and some of it landed on the Moon. There could be a few hundred kilograms of Earth material per square kilometer of the Moon’s surface, buried under a few meters of lunar soil. It would be interesting to retrieve those rocks and bring back samples of the early Earth. Almost nothing from this time period has survived on the Earth because of tectonic recycling of the crust plates or because of atmospheric weathering. We would try to detect some organics within those rocks, and that could tell us about the history of organic chemistry on Earth. Some of these rocks could even have preserved fossils of life. Such rocks could help us look further back into the fossil record, which now stops at 3.5 billion years ago. This way, we could possibly learn about the emergence of life on Earth.
By exploring the Moon, we also can get clues on how the Earth has evolved. We can study processes on the Moon that have also shaped the Earth, like volcanism and tectonics. Because the Moon is smaller than the Earth, the Moon’s radiogenic heating dissipated much faster. After about one billion years, the interior of the Moon didn’t evolve much, and surface changes mostly were due to impacts. There was a brief period of magmatic activity from the subsurface — a few plumes of magma made their way up to the surface and filled newly formed impact basins with basalt, creating what we call the Maria. This happened up to about 2 billion years ago. Because the Moon offers different conditions than the Earth, we can better understand how physical processes work generally by studying a larger range of parameters than just the Earth’s.
|During its flight, the Galileo spacecraft returned images of the Earth and the Moon. The separate images were combined to generate this view.
The Moon affects the liquid envelope of the Earth, and the oceanic tides in particular. The Moon affects the ocean tides more in some areas than others. For instance, in the channel between the British Isles and the European continent, the tidal range can be 10 meters, compared to what you see in the Pacific, where it is below a meter.
The crust of the Earth is also affected. The Moon’s tidal forcing causes significant heating and dissipation of energy to take place. Part of this energy is heating the Earth, and part of it is dissipated by forcing the Moon to recede from the Earth over time. There are people who propose that the tidal effect of the Moon may have helped trigger the convection on the Earth that led to the multi-plate tectonics. The other planets don’t have the same tectonic cycle. For most of them, the crust is like a lid that doesn’t move much horizontally, and the magma and heat are blocked by this lid on the surface. The Earth instead has rolling convective motion that drags the crust, and then the crust plunges back down into the mantle and gets recycled.
There are some very subtle effects of the Moon in the climate and the oceans. One pattern that has been found recently is related to the Pacific Ocean’s El Niño phenomenon. You have a cold undersea current coming from the Antarctic sea, and that creates the Humboldt stream which keeps the sea around the South American coast near Peru and Chile quite cold. Because of this, there are fewer clouds and less precipitation there. Sometimes this current drifts away from the coast, and then you have much more cloud formation and a period of very bad weather over South America. Satellites have monitored this stream over the Pacific Ocean and they have found some streams which were not known before. They can connect some of these streams with how the Moon’s tidal effect influences the mixing of the deep ocean. There was a French-American mission called TOPEX/Poseidon that accurately measured the altitude of the sea and detected a little stream a few centimeters high. That doesn’t seem like a lot, but over the whole area of the Pacific Ocean it represents a huge amount of water transferred from one place to another.
|Map showing tidal variations across the globe. Red areas represent large variations in water level, purple areas represent zero or very low tidal variation. Click image for larger view.
Image Credit: Legos/CNRS.
If you would take away the Moon suddenly, it would change the global altitude of the ocean. Right now there is a distortion which is elongated around the equator, so if we didn’t have this effect, suddenly a lot of water would be redistributed toward the polar regions.
The Moon has been a stabilizing factor for the axis of rotation of the Earth. If you look at Mars, for instance, that planet has wobbled quite dramatically on its axis over time due to the gravitational influence of all the other planets in the solar system. Because of this obliquity change, the ice that is now at the poles on Mars would sometimes drift to the equator. But the Earth’s moon has helped stabilize our planet so that its axis of rotation stays in the same direction. For this reason, we had much less climatic change than if the Earth had been alone. And this has changed the way life evolved on Earth, allowing for the emergence of more complex multi-cellular organisms compared to a planet where drastic climatic change would allow only small, robust organisms to survive.
The Moon has influenced biology in other ways as well. For species living near the coast, the tide is an important factor. When you look at the shorelines, you can recognize different layers of organisms that have adapted to the salt water conditions based on the ebb and flow of the tide.
The eyesight of many mammals is sensitive to moonlight. The level of adaptation of night vision would be very different without the Moon. Many of these species have evolved in such a way that their night vision could work in even partial lunar illumination, because that’s when they are most active. But they can be more subjected to predators, too, so there is a balance between your ability to see and your ability not to be seen. The Moon has completely changed evolution in that aspect.
|The various phases of the Moon. As the Moon orbits the Earth, the amount of sunlight reflecting off the lunar surface changes its appearance. When the Earth is between the Sun and the Moon, we see a full moon; when the Moon is between the Sun and the Earth, we see a new moon. Click image for larger view.|
Human vision is so sensitive that we are almost able to work by the light of the Milky Way. The full Moon has more light than we need to see at night. For most of our history, we were hunting and fishing or doing agriculture, and we organized our lives by using the Moon. It determined the time for hunting, or the time where we could harvest. That’s why most of our calendars are based on the Moon.
In a recent workshop called “Earth-Moon Relationships,” psychologists discussed the relation between the lunar phases and several aspects of life. There was a very interesting correlation, not with the birth of children, but with the time of conception. Perhaps that is due to some social or sentimental value of the Moon. We tend to forget the impact the Moon has on our lives because we use electric lights, but for most of our history we had to adapt our behavior to the lunar phases.
Finally, the Moon had a key role in the emergence of science, and in our understanding of our place in the universe. We saw the repetition of the phenomena of lunar phases, and we observed solar and lunar eclipses. These were big challenges to our understanding of nature, and a few astronomers were put to death because they weren’t able to predict the eclipses. This challenged us to develop accurate predictions for the motion of the sun and the motion of the Moon.
Studying the Moon helped us determine distances in the solar system and the size of celestial objects. By studying lunar phases, for example, people were able to determine how far the Moon is from the Earth, the size of the Earth, and our distance from the sun. More recently, the Moon was the terrain where the space race took place between two political systems, allowing for great technical and scientific achievements. The Moon has inspired humankind to learn how to travel to space, and to bring life beyond Earth’s cradle. | 0.849507 | 3.520472 |
The evolved Laser Interfermoter Space Antenna (eLISA) is a mission aiming at exploring the Gravitational Universe from space for the first time. It involves scientists from eight European countries ‒ Denmark, France, Germany, Italy, The Netherlands, Spain, Switzerland, and the UK ‒ as well as the support of several US-based ones. “The Gravitational Universe” theme (with eLISA as foreseen implementation) was proposed to the European Space Agency and selected as a science theme for the third large-class mission to be launched in 2034 within the agency’s Cosmic Vision science program.
The eLISA mission consists of a “Mother” and two “Daughter” spacecrafts. These will orbit the Sun in a triangular configuration, as shown the figure. The three satellites will form a precision interferometer, with the two Daughter spacecrafts connected to the Mother one by 1 million km long laser beams. This interferometer will be capable of detecting gravitational waves at frequencies in the range of 0.1 mHz to 1 Hz. Such a frequency interval is not accessible on Earth due to arm length limitations and to noise caused by the terrestrial gravity gradient noise: in this sense, eLISA will complement the efforts of ground-based gravitational-wave detectors.
eLISA is designed with orbits that allow the three satellites to maintain their near-equilateral triangular configuration. Indeed, because of their special orbits, they are seen to rotate about an axis passing through the centre of the triangle and normal to its plane. A passing gravitational wave alters the proper relative distance between the spacecraft, which will be sensed by detectors on each spacecraft. eLISA will coherently measure the frequency, phase, and polarisation of gravitational waves passing through it, allowing scientists to resolve overlapping signals and locating them on the sky. The former will be achieved with sophisticated pattern recognition algorithms capable of digging signals out of noise, by exploiting Einstein’s theory to predict the precise nature of signals emitted by several types of sources. Sky location, instead, will take advantage of eLISA’s annual motion around the Sun: this causes a signal to be Doppler modulated in a way that specifically depends on the sky location of the source. This capability is particularly appealing because eLISA will have an all-sky field of view, that is, it will be sensitive to sources in any direction of the sky.
The low-frequency part of the spectrum of gravitational waves will witness sources in our own Galaxy as well as those in the very distant parts of the Universe. Binaries consisting of ordinary stars as well as white dwarves and other exotic objects, with periods of several mins to a few hours will be visible in LISA. Indeed, there will be so many that only the strongest and nearest of these binaries will stand above the stochastic background created by the numerous others in this band. LISA will also be able to see the coalescences of galaxies occurring anywhere in the universe by detecting the inspiral and coalescence of supermassive black holes believed to lie at the centre of galaxies.
LISA Pathfinder (LPF)
The eLISA mission technology is being tested in space with LISA Pathfinder (LPF). LPF was launched successfully on 3rd December 2015 at 4:04 GMT, onboard Vega VV06, from Europe’s Spaceport, French Guiana. A picture of the liftoff is shown in the picture.
LPF was placed in a low-earth transfer orbit. From there, the satellite used its propulsion module in order to reach the operational orbit around the Lagrange point L1 (22nd January 2015). Here, LPF’s two test-masses will be in a nearly perfect gravitational free-fall. Innovative technological devices will be used to control the masses and measure their relative motion with unprecedented accuracy. The test-masses and their environment will be the quietest place in the solar system.
Because LPF is such an extremely sensitive gradiometer that can measure changes in the external gravity gradient on timescales of 10’s of minutes, it could be used to test the behaviour of gravity in its weak regime. A number of theories of gravity which differ from Einstein’ one were proposed over the years as an alternative to invoking dark matter to explain the observed galactic rotation curves. In the weak regime, these may present a characteristic acceleration scale below which deviations from Newtonian dynamics should be detectable, contrary to the case of General Relativity. At the Earth-Sun saddle point, the Newtonian background drops below this characteristic acceleration scale. Therefore, scientists, including Cardiff University personnel, are studying possible LPF mission extension scenarios to navigate the satellite from L1 to the saddle point and the data analysis techniques required to perform this test of gravity. | 0.879371 | 3.984067 |
The discovery by an undergraduate student of tubes of plasma drifting above Earth has made headlines in the past few days. Many people have asked how the discovery was made and, in particular, how an undergraduate student was able to do it.
The answer is a combination of an amazing new telescope, a very smart student and an unexpected fusion of two areas of science.
Here is how it all happened, from my perspective as the academic who supervised the project at the Sydney Institute for Astronomy.
My research involves studying the variability of stars and galaxies using a new radio telescope, the Murchison Widefield Array (MWA). My colleagues and I were worried about the ionosphere being a problem for this research, because at low frequencies it can distort the radio signals that we receive from outer space.
This makes celestial objects appear to jiggle around, be stretched and squeezed, and change in brightness. I knew this would be a problem for my plan to study how the brightness of stars and galaxies varied, so I wanted to find out how severe the distortion was.
The ionosphere is the part of the Earth’s atmosphere that has been ionised by radiation from the sun. It is made up of a plasma in which the gas molecules have lost one or more electrons. It stretches between 50 to 1,000 kilometres above the Earth’s surface (commercial aeroplanes typically fly at 10 kilometres above the Earth). Importantly, it refracts radio waves, affecting radio communication around the world.
At the beginning of last year I had a final-year undergraduate student, Cleo Loi – who also contributed to this article – looking for a research project, so I gave her the task of investigating how much the ionosphere was affecting astronomical observations with the MWA.
Around that time, a postdoctoral researcher from Curtin University, Natasha Hurley-Walker, was examining MWA data and came across a night that looked rather unusual.
Celestial objects were dancing around wildly, distorting strongly in shape and flickering in brightness. She flagged this night as one that the ionosphere had rendered unusable for our astronomy research.
Cleo then developed a way of visualising the distortions caused by the ionosphere on the images of distant background galaxies. She took the data Natasha had identified and applied her analysis to it.
When she showed me and other researchers the distortion maps she was generating, we were surprised to see huge waves of correlated motion rippling through the image. They looked like spokes radiating from a point outside the image.
Looking for answers
To try to work out what they were, Cleo transformed the coordinates from a celestial reference frame (that astronomers usually use) to an Earth-based reference frame, which is fixed with respect to the atmosphere. This crucial transformation revealed that the bands were hanging almost stationary in the Earth’s sky.
In the process of writing up our research, we emailed Cleo’s preliminary results to collaborators. The MWA collaboration consists of hundreds of radio astronomers and engineers from Australia, New Zealand, the United States, India and Canada. They were quick to respond with a list of suggestions as to what the bands might be.
It is a critical part of science that good scientists respond to unexpected results with scepticism, particularly if they come from an inexperienced student. But the sheer volume of emails was initially quite overwhelming for Cleo. However, she stayed focused on solving the problem.
The suggestions ranged from possible problems with the telescope, the observing set-up, the imaging process and Cleo’s analysis techniques. Hundreds of emails were exchanged over a few months as Cleo tested and ruled out each suggestion.
Once we had run out of things to test we were left with an interesting dataset, an unexplained phenomenon and an increasing suspicion that the strange distortion pattern was a real effect caused by the ionosphere.
As she was preparing her honours thesis, Cleo had a geometrical insight into explaining the radial spoke-like pattern. She realised that a set of parallel lines viewed at an angle would appear to converge due to perspective distortion, like train tracks going into the distance.
However, without much knowledge of geophysics, it was several weeks until she made a second critical link: the layout of the spokes matched the Earth’s magnetic field. These strange tubular structures were tracing the magnetic field lines, which are parallel to one another but at an angle to the ground. The agreement was perfect.
Armed with solid evidence, Cleo and I got in touch with geospace physicists to help us interpret what we were seeing. Suggestions to explain the phenomena included plasma bubbles, travelling ionospheric disturbances and ultra-low-frequency waves.
Finally, Fred Menk from the University of Newcastle suggested they might be “whistler ducts”. These are cylindrical structures aligned to a magnetic field, where the electron content is higher inside than outside. They are thought to guide the propagation of electromagnetic waves called “whistlers” in the same way that optic fibres guide light.
Whistler ducts had never been seen before, but all their properties deduced by scientists over the years matched what we were seeing with the MWA. Except for one thing: we didn’t know how high they were.
Until now, we had only used the MWA to take two-dimensional pictures of the sky. Whistler ducts exist at very high altitudes, and an altitude measurement was necessary if we were to confirm them as a known phenomenon.
Cleo was reluctant to publish the result without an altitude estimate. However, we couldn’t derive that from our data, so we encouraged her to publish the results as they were.
At that point Cleo had a brainwave. She realised that the MWA could be used stereoscopically to achieve 3D vision, like a giant pair of eyes. By splitting the data from the eastern and western receivers of the MWA, she revealed a slight parallax shift in the distortion pattern that let us triangulate the altitude: around 600km above the ground.
We were all astounded that this idea had worked, confirming that these were likely to be whistler ducts.
It has been an exciting year of research. We started out with an astronomy question and found a surprising answer in geospace physics. To the layperson, these might seem like the same field, but to scientists focused deeply within their narrow field of expertise, the gap is wide.
Cleo has shown how a talented but novice researcher can have an advantage over experienced researchers. By approaching the problem without preconceptions she was able to bridge these two disciplines and use a novel technique on a new radio telescope to discover plasma tubes in the sky. | 0.858126 | 3.793379 |
Newly discovered supernova remnants only reveal themselves at the highest gamma-ray energies
Astrophysicists of the University of Tübingen publish new results on the occasion of the 15th anniversary of the Gamma Telescope System in Namibia that is operated by the H.E.S.S. collaboration
The H.E.S.S. telescopes have surveyed the Milky Way for the past 15 years searching for sources of gamma radiation. The H.E.S.S. collaboration includes scientists of the Institute of Astronomy and Astrophysics of the University of Tübingen led by Professor Andrea Santangelo and Dr. Gerd Pühlhofer. They are interested in sources of very high energy gamma radiation in the TeV energy range, i.e. in the range of 1012 electron volts, corresponding to a trillion of the energy of visible light photons. For the first time they have been able to classify celestial objects using only the emission of this kind of radiation: very likely they are supernova remnants, which are celestial objects that emerge after the explosion of massive stars. The results are published in a special edition of the scientific journal Astronomy & Astrophysics, which appears on the occasion of the 15th anniversary of the H.E.S.S. telescopes with the largest set of science results of the project to date.
Over 200 sources of TeV radiation are known to date, both Galactic and Extragalactic. “We can often relate the radiation to known astrophysical objects that have been studied before with conventional telescopes in lower frequency bands, e.g. in optical or radio wavebands”, says Gerd Pühlhofer. “Interestingly, however, with the survey observations along the Galactic plane that have been conducted with the H.E.S.S. telescopes, many new sources have been discovered which are not or not clearly associated with objects in lower frequencies.” And the TeV gamma-ray data alone is usually not sufficient to attribute a source to a particular astrophysical type of object. “Those unidentified sources continue to remain a big puzzle in gamma-ray astronomy.”
But the H.E.S.S. telescopes delivered data that are detailed enough that the scientists could get further. “For the first time, we are now able to classify unidentified TeV sources to be members of a particular object class, using only the TeV data”, says Pühlhofer. “Three particular sources are now classified with high probability as supernova remnants.”
A supernova remnant is a celestial object that forms after the explosion of a massive star at the end of its lifetime. The matter that is expelled in such an explosion leads to shock waves that propagate into the interstellar medium. There, the matter is heated and particles are accelerated to relativistic speeds. The particles interact with light and gas in the neighbourhood of the sources and thus produce very high energy gamma rays. “We have already known since well over a decade that some of the 300 known supernova remnants in our Galaxy shine brightly in TeV gamma-rays”, explains Daniel Gottschall, PhD student in Pühlhofer’s research group. “But all these objects have been known before from observations in other wavebands and have been classified as supernova remnants”, adds Massimo Capasso, also PhD student in the research group.
More research questions
The question remains, states Gerd Pühlhofer, why these supernova remnants have escaped detection so far. “They are as large as the full moon, but totally invisible to the eye or to conventional, e.g. optical, telescopes”, explains the astrophysicist. He considers it possible that in previous sky surveys, because of their position in the Milky Way and because of their large extension, they were indistinguishable from the many other objects or they are partially covered by foreground gas. “A more exciting possibility would be if the new supernova remnants substantially differ from the other known big remnants that have been investigated with the H.E.S.S. telescopes before”, he adds. “They may belong to a special flavour of supernova remnants whose gamma-ray emission is induced by hadrons.”
The community of gamma-ray astronomers is currently preparing the much more sensitive next-generation instrument for TeV gamma-ray astronomy, the Cherenkov Telescope Array CTA. Scheduled to move into regular operations in the 2020’s, it will provide a much more detailed and sensitive image of our Milky Way in gamma-rays.
A search for new supernova remnant shells in the Galactic plane with H.E.S.S.
Corresponding authors: G. Pühlhofer, D. Gottschall, M. Capasso.
H. Abdallah et al. (H.E.S.S. collaboration), Astronomy & Astrophysics, Vol. 612,
A&A special issue:
Press release of the H.E.S.S. collaboration about the special issue:
University of Tübingen
Faculty of Science
Institut für Astronomie und Astrophysik/Kepler Center for Astro and Particle Physics
Dr. Gerd Pühlhofer
Phone +49 7071 29-74982
Prof. Dr. Andrea Santangelo
Phone +49 7071 29-78128
Institute of Astronomy and Astrophysics Tübingen:
H.E.S.S. instrument: www.mpi-hd.mpg.de/HESS/pages/about/
CTA observatory: www.cta-observatory.org
H.E.S.S. II press release of the University of Tübingen:
The H.E.S.S. Telescopes
The collaboration: The High Energy Stereoscopic System (H.E.S.S.) team consists of scientists from Germany, France, the United Kingdom, Namibia, South Africa, Ireland, Armenia, Poland, Australia, Austria, Sweden, and the Netherlands. The University of Tübingen is part of the H.E.S.S. collaboration through the High Energy Astrophysics Section of the Institute for Astronomy and Astrophysics Tübingen (IAAT), financially supported by the Federal Ministry for Education and Research.
The instrument: The results were obtained using the High Energy Stereoscopic System (H.E.S.S.) telescopes in Namibia, in South-West Africa. This system of four 13 m diameter telescopes – a couple of years ago complemented with the huge 28 m H.E.S.S. II telescope – is one of the most sensitive detectors of very high-energy gamma rays. These are absorbed in the atmosphere, where they create a short-lived shower of particles. The H.E.S.S. telescopes detect the faint, short flashes of bluish light which these particles emit (named Cherenkov light, lasting a few billionths of a second), collecting the light with big mirrors which reflect onto extremely sensitive cameras. The H.E.S.S. telescopes have been operating since late 2002. H.E.S.S. has discovered the majority of the known cosmic objects emitting very high-energy gamma rays. A study performed in 2009 listed H.E.S.S. among the top 10 observatories worldwide.
The Earth is constantly bombarded by high energy particles of cosmic origin. Those particles are protons, electrons and atomic nuclei and comprise the so-called “cosmic radiation”. Since more than a century, the origin of the cosmic rays remains one of the most enduring mysteries of science. The problem is: these “cosmic rays” are electrically charged, and are hence strongly deflected by the interstellar magnetic fields that pervade our galaxy. Their path through the cosmos is randomised by these deflections, making it impossible to directly identify the astrophysical sources responsible for their production. Cosmic rays interact with light and gas in the neighbourhood of their sources and thus produce high energy gamma rays. These gamma rays travel in straight lines to Earth, undeflected by magnetic fields. This gamma radiation can therefore be used to identify the sources of the cosmic rays at the sky.
Eberhard Karls Universität Tübingen
Public Relations Department
Dr. Karl Guido Rijkhoek
Phone +49 7071 29-76753
Fax +49 7071 29-5566 | 0.915588 | 3.994245 |
Scientists looked back in time to offer new evidence suggesting that plumes of water vapour shoot out into space from Jupiter’s moon Europa.
In the study, researchers used Galileo spacecraft for observation to simulate the movement of positively charged subatomic particles called protons near the moon. Galileo found fewer protons around Europa, while it was flying by the icy world of Europa in 2000.
Now according to the new research, Huybrighs’ team found that some of these “missing protons” which were not found before as a water plume shooting out from the moon blocked them from the instrument. Galileo used different instruments to conduct magnetic field studies of the moon, and then researchers were able to show a disruption in nearby magnetic fields when the plume shot out to support the theory.
Europa, one of Jupiter’s 79 known moons, was discovered in 1610 by astronomers Galileo Galilei and Simon Marius along with the rest of the planet’s four relatively large “Galilean moons.” Before in 2016, using observations from the Hubble Space Telescope, they’d long suspected, water vapour plumes shoot out from Europa, stemming from the moon’s hypothesized subsurface ocean. Now, in a new study, scientists led by European Space Agency research fellow Hans Huybrighs used 20-year-old data from NASA’s Galileo mission to provide even more evidence for these plumes.
ESA aims to probe to Jupiter Icy Moons Explorer with its highly-anticipated mission. The mission will be launch in 2022 and will start to explore Jupiter and its many moons and capable of taking and studying samples from the plumes shooting out from Europa. | 0.800045 | 3.656852 |
Scientists have speculated that given the sheer number of galaxies in our Universe – modern estimates are as high as 2 trillion – that there must be infinite opportunities for life to emerge. It has also been theorized that galaxies (like stars) have habitable zones, where star systems located too close to the core or too far out in the spiral arms will be exposed to too much radiation for life to emerge.
But are certain types of galaxies more likely to produce intelligent life? Not that long ago, scientists believed that giant elliptical galaxies – which are substantially larger than spiral galaxies (like the Milky Way) – are a far more likely place to find advanced civilizations. But according to new research from the University of Arkansas, these galaxies may not be the cradles of civilization they were previously thought to be.
To put it plainly, elliptical galaxies account for 10 to 15% of all galaxies in our corner of the Universe (the Virgo Supercluster). They are so-named because of their ellipsoid profile and are typically comprised of very old and/or low-mass stars (M-type red dwarfs). Combined with a low rate of star formation, this makes them dim in comparison to spiral galaxies.
The largest galaxies are typically giant ellipticals, which contain upwards of a trillion stars and can measure as much as one million light-years in diameter – 10 times as large as the Milky Way. Based on a threefold set of criteria, a team of researchers prosposed in a 2015 study that these galaxies were the best place to look for evidence of extraterrestrial intelligence (ETI).
First, there is the total number of stars in a galaxy that are capable of hosting planets. Second, there’s the availability of the chemical elements necessary for life, such as carbon, oxygen, and iron – which is more likely where older stars exist. Third, there is the rate of supernova explosions, which release powerful radiation that can inhibit the formation and evolution of complex life on nearby planets.
Using data obtained by the Sloan Digital Sky Survey of more than 150,000 nearby galaxies, the team created a cosmological model to assess the potential habitability of certain types of galaxies. What they determined was that metal-rich elliptical galaxies (but have one-tenth the star formation rate) could potentially host ten thousand times as many habitable planets as the Milky Way.
Because of this, they are statistically much more likely to be “cradles of civilization.” But according to Daniel Whitmire, a retired professor of astrophysics and instructor at the University of Arkansas, the 2015 study and the resulting model contradicts the statistical rule known as the principle of mediocrity (aka. the Copernican Principle).
This principle states that in lieu of evidence to the contrary, an object or some property of an object should be considered typical of its class (rather than atypical). As Whitmer said in a University of Arkansas news statement:
“The 2015 paper had a serious problem with the principle of mediocrity. In other words, why don’t we find ourselves living in a large elliptical galaxy? To me this raised a red flag. Any time you find yourself as an outlier, i.e. atypical, then that is a problem for the principle of mediocrity.”
In accordance with the Copernican Principle, Earth and human civilization should be considered typical of habitable planets and technological civilizations elsewhere in the Universe – i.e. located in a spiral galaxy between the core and the arms. But the 2015 study suggests the opposite, that most habitable planets would be located in a type of galaxy other than our own.
In his own paper, which recently appeared in The Monthly Journal of the Royal Astronomical Society, Whitmire proposes two reasons why large elliptical galaxies may not be such a good bet for ETIs. In one scenario, elliptical galaxies experience massive galactic sterilization events as a result of quasar activity and supernovae that occurred when the galaxies were smaller and more compact.
In the other, the generally-higher metallicity of large elliptical galaxies is likely to result in a disproportionately higher number of gaseous planets in large elliptical galaxies – meaning less rocky (aka. “Earth-like”) planets. As Whitmire said:
“The evolution of elliptical galaxies is totally different than the Milky Way. These galaxies went through an early phase in which there is so much radiation that it would just completely have nuked any habitable planets in the galaxy and subsequently the star formation rate, and thus any new planets, went to essentially zero. There are no new stars forming and all the old stars have been irradiated and sterilized.“
This study is similar to research conducted in recent years that have reconsidered questions relating to planetary habitability. Instead of using present-day Earth as a template, scientists have recommended factoring in how Earth’s environment (and its lifeforms) evolved over time. While Earth has a relatively warm and oxygen/nitrogen-rich atmosphere today, it was a very different place when life first emerged.
You might think this is bad news, but from a SETI standpoint, it’s actually encouraging. While this study casts doubt on giant elliptical galaxies being the best place to look for intelligent life, it means that SETI efforts are best directed at our own galaxy and those like it. And according to data from SDSS, spiral galaxies are much more common, accounting for 77% of galaxies in the known Universe.
Now if we could just find some evidence of that statistically more-likely life, we’d be in business! | 0.860252 | 3.96655 |
Astronomers spotted an interstellar object passing through our solar system last month. It was only the second time scientists have ever detected such an object, and after some intense investigation, the object — now believed to be a comet or comet-like body — was documented and named for the amateur astronomer who first spotted it.
The comet, called 2I/Borisov, was spotted relatively early in its trip through our system, giving scientists plenty of time to observe it. The first round of studies is already returning some interesting findings, including the fact that the object is dumping cyanogen gas (gas that is at least partly made up of cyanide) as it speeds through our home system.
A new paper published in Astrophysical Journal Letters reveals that interesting finding, which was made thanks to data gathered by an international team of scientists using the William Herschel Telescope. But as seemingly frightening as this discovery seems on the surface, there’s very little to worry about for us here on Earth.
“Interstellar objects are samples of materials from other planetary systems, delivered to our doorstep—or at least to our own solar system,” Professor Alan Fitzsimmons, who led the research, told Universe Today. “The physical nature gives us clues as to how other planetary systems evolve, and the types of small bodies that may exist there. Measuring their composition allows us to compare what we find with decades of studies of comets and asteroids orbiting the sun.”
Fitzsimmons says that while this particular comet appears a bit more “gassy” than the kinds of comets we typically see in our system, the fact that it contains cyanide isn’t particularly shocking.
2I/Borisov’s trajectory has already been plotted and it doesn’t seem that the object will come anywhere near Earth, or even pass through Earth’s orbital path around the Sun, so there’s virtually zero chance any of the comet material will find its way to our planet.
Scientists will continue to observe the object as it gradually passes through our system, and the comet should remain visible for many months to come. You can expect to hear a lot more about it as various research efforts get underway. | 0.902905 | 3.681267 |
Cool halo gas caught spinning like galactic disks
A group of astronomers led by Crystal Martin and Stephanie Ho of the University of California, Santa Barbara, has discovered a dizzying cosmic choreography among typical star-forming galaxies; their cool halo gas appears to be in step with the galactic disks, spinning in the same direction.
The researchers used W. M. Keck Observatory to obtain the first-ever direct observational evidence showing that corotating halo gas is not only possible, but common. Their findings suggest that the whirling gas halo will eventually spiral in towards the disk.
"This is a major breakthrough in understanding how galactic disks grow," said Martin, Professor of Physics at UC Santa Barbara and lead author of the study. "Galaxies are surrounded by massive reservoirs of gas that extend far beyond the visible portions of galaxies. Until now, it has remained a mystery how exactly this material is transported to galactic disks where it can fuel the next generation of star formation."
The study is published in today's issue of the Astrophysical Journal and shows the combined results of 50 standard star-forming galaxies taken over a period of several years.
Nearly a decade ago, theoretical models predicted that the angular momentum of the spinning cool halo gas partially offsets the gravitational force pulling it towards the galaxy, thereby slowing down the gas accretion rate and lengthening the period of disk growth.
The team's results confirm this theory, which show that the angular momentum of the halo gas is high enough to slow down the infall rate but not so high as to shut down feeding the galactic disk entirely.
The astronomers first obtained spectra of bright quasars behind star-forming galaxies to detect the invisible halo gas by its absorption-line signature in the quasar spectra. Next, the researchers used Keck Observatory's laser guide star adaptive optics (LGSAO) system and near-infrared camera (NIRC2) on the Keck II telescope, along with Hubble Space Telescope's Wide Field Camera 3 (WFC3), to obtain high-resolution images of the galaxies.
"What sets this work apart from previous studies is that our team also used the quasar as a reference 'star' for Keck's laser guide star AO system," said co-author Ho, a physics graduate student at UC Santa Barbara. "This method removed the blurring caused by the atmosphere and produced the detailed images we needed to resolve the galactic disks and geometrically determine the orientation of the galactic disks in three-dimensional space."
The team then measured the Doppler shifts of the gas clouds using the Low Resolution Imaging Spectrometer (LRIS) at Keck Observatory, as well as obtaining spectra from Apache Point Observatory. This enabled the researchers to determine what direction the gas is spinning and how fast. The data proved that the gas is rotating in the same direction as the galaxy, and the angular momentum of the gas is not stronger than the force of gravity, meaning the gas will spiral into the galactic disk.
"Just as ice skaters build up momentum and spin when they bring their arms inward, the halo gas is likely spinning today because it was once at much larger distances where it was deposited by galactic winds, stripped from satellite galaxies, or directed toward the galaxy by a cosmic filament," said Martin.
The next step for Martin and her team is to measure the rate at which the halo gas is being pulled into the galactic disk. Comparing the inflow rate to the star formation rate will provide a better timeline of the evolution of normal star-forming galaxies, and explain how galactic disks continue to grow over very long timescales that span billions of years. | 0.881199 | 4.050763 |
Pluto's icy heart makes winds blowChristian Fernsby ▼ | February 5, 2020
A 'beating heart' of frozen nitrogen controls Pluto's winds and may give rise to features on its surface, according to a new study.
In space Pluto
Now, new research shows Pluto's renowned nitrogen heart rules its atmospheric circulation. Uncovering how Pluto's atmosphere behaves provides scientists with another place to compare to our own planet. Such findings can pinpoint both similar and distinctive features between Earth and a dwarf planet billions of miles away.
Nitrogen gas an element also found in air on Earth comprises most of Pluto's thin atmosphere, along with small amounts of carbon monoxide and the greenhouse gas methane. Frozen nitrogen also covers part of Pluto's surface in the shape of a heart. During the day, a thin layer of this nitrogen ice warms and turns into vapor. At night, the vapor condenses and once again forms ice. Each sequence is like a heartbeat, pumping nitrogen winds around the dwarf planet.
New research in AGU's Journal of Geophysical Research: Planets suggests this cycle pushes Pluto's atmosphere to circulate in the opposite direction of its spin a unique phenomenon called retro-rotation. As air whips close to the surface, it transports heat, grains of ice and haze particles to create dark wind streaks and plains across the north and northwestern regions.
"This highlights the fact that Pluto's atmosphere and winds even if the density of the atmosphere is very low can impact the surface," said Tanguy Bertrand, an astrophysicist and planetary scientist at NASA's Ames Research Center in California and the study's lead author.
Most of Pluto's nitrogen ice is confined to Tombaugh Regio. Its left "lobe" is a 1,000-kilometer (620-mile) ice sheet located in a 3-kilometer (1.9-mile) deep basin named Sputnik Planitia an area that holds most of the dwarf planet's nitrogen ice because of its low elevation. The heart's right "lobe" is comprised of highlands and nitrogen-rich glaciers that extend into the basin.
"Before New Horizons, everyone thought Pluto was going to be a netball completely flat, almost no diversity," Bertrand said. "But it's completely different. It has a lot of different landscapes and we are trying to understand what's going on there."
Bertrand and his colleagues set out to determine how circulating air which is 100,000 times thinner than that of Earth's might shape features on the surface. The team pulled data from New Horizons' 2015 flyby to depict Pluto's topography and its blankets of nitrogen ice. They then simulated the nitrogen cycle with a weather forecast model and assessed how winds blew across the surface.
The group discovered Pluto's winds above 4 kilometers (2.5 miles) blow to the west the opposite direction from the dwarf planet's eastern spin in a retro-rotation during most of its year. As nitrogen within Tombaugh Regio vaporizes in the north and becomes ice in the south, its movement triggers westward winds, according to the new study. No other place in the solar system has such an atmosphere, except perhaps Neptune's moon Triton.
The researchers also found a strong current of fast-moving, near-surface air along the western boundary of the Sputnik Planitia basin. The airflow is like wind patterns on Earth, such as the Kuroshio along the eastern edge of Asia. Atmospheric nitrogen condensing into ice drives this wind pattern, according to the new findings. Sputnik Planitia's high cliffs trap the cold air inside the basin, where it circulates and becomes stronger as it passes through the western region.
The intense western boundary current's existence excited Candice Hansen-Koharcheck, a planetary scientist with the Planetary Science Institute in Tucson, Arizona who wasn't involved with the new study.
"It's very much the kind of thing that's due to the topography or specifics of the setting," she said. "I'm impressed that Pluto's models have advanced to the point that you can talk about regional weather."
On the broader scale, Hansen-Koharcheck thought the new study was intriguing. "This whole concept of Pluto's beating heart is a wonderful way of thinking about it," she added.
These wind patterns stemming from Pluto's nitrogen heart may explain why it hosts dark plains and wind streaks to the west of Sputnik Planitia. Winds could transport heat which would warm the surface or could erode and darken the ice by transporting and depositing haze particles. If winds on the dwarf planet swirled in a different direction, its landscapes might look completely different.
"Sputnik Planitia may be as important for Pluto's climate as the ocean is for Earth's climate," Bertrand said. "If you remove Sputnik Planitia if you remove the heart of Pluto you won't have the same circulation," he added.
The new findings allow researchers to explore an exotic world's atmosphere and compare what they discover with what they know about Earth. The new study also shines light on an object 6 billion kilometers away from the sun, with a heart that captivated audiences around the globe.
"Pluto has some mystery for everybody," Bertrand said. ■ | 0.83509 | 3.844306 |
The wonders – and mysteries – of Kuiper Belt object 2014 MU69 continue to multiply as NASA’s New Horizons spacecraft beams home new images of its New Year’s Day 2019 flyby target.
This image, taken during the historic Jan. 1 flyby of what’s informally known as Ultima Thule, is the clearest view yet of this remarkable, ancient object in the far reaches of the solar system – and the first small “KBO” ever explored by a spacecraft.
Obtained with the wide-angle Multicolor Visible Imaging Camera (MVIC) component of New Horizons’ Ralph instrument, this image was taken when the KBO was 4,200 miles (6,700 kilometers) from the spacecraft, at 05:26 UT (12:26 a.m. EST) on Jan. 1 – just seven minutes before closest approach. With an original resolution of 440 feet (135 meters) per pixel, the image was stored in the spacecraft’s data memory and transmitted to Earth on Jan. 18-19. Scientists then sharpened the image to enhance fine detail. (This process – known as deconvolution – also amplifies the graininess of the image when viewed at high contrast.)
The oblique lighting of this image reveals new topographic details along the day/night boundary, or terminator, near the top. These details include numerous small pits up to about 0.4 miles (0.7 kilometers) in diameter. The large circular feature, about 4 miles (7 kilometers) across, on the smaller of the two lobes, also appears to be a deep depression. Not clear is whether these pits are impact craters or features resulting from other processes, such as “collapse pits” or the ancient venting of volatile materials.
Both lobes also show many intriguing light and dark patterns of unknown origin, which may reveal clues about how this body was assembled during the formation of the solar system 4.5 billion years ago. One of the most striking of these is the bright “collar” separating the two lobes.
“This new image is starting to reveal differences in the geologic character of the two lobes of Ultima Thule, and is presenting us with new mysteries as well,” said Principal Investigator Alan Stern, of the Southwest Research Institute in Boulder, Colorado. “Over the next month there will be better color and better resolution images that we hope will help unravel the many mysteries of Ultima Thule.”
New Horizons is approximately 4.13 billion miles (6.64 billion kilometers) from Earth, operating normally and speeding away from the Sun (and Ultima Thule) at more than 31,500 miles (50,700 kilometers) per hour. At that distance, a radio signal reaches Earth six hours and nine minutes after leaving the spacecraft.
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute | 0.805071 | 3.643907 |
First Light in astronomy is an old tradition filled with all sorts of interesting history. Some first light examples are not the best, while others are just tremendous. Ours was a little of both with the first exposure of the 0.7m telescope to the nighttime sky. Don’t worry! It all turned out just fine!
The vert first exposure of starlight to the telescope was last week: Conditions were good with a nice clear sky and freezing temperatures. The wind was calm. The telescope had never been focused before and had yet to have a pointing solution…. so it really had no idea where it was looking. We decided to aim it in the general direction of Orion and take the first images. Of course, they were blurry. The scope had never been focused before. At this point we got the CCD imager into automatic mode, making it take an image every second, non-stop so that we could run the focuser until we had the images nice and sharp…. out the focuser went, and the star images got smaller and smaller and smaller, then “kachunk!” The focuser had run out of travel, and the star images were not quite in focus yet! The imager was perhaps a few millimeters away from achieving a perfect focus. The good news was that this was more than enough to engage in the time consuming process of collimating the primary mirror. A few hours later we had aligned optics, but we had to order a small spacer ring to push the CCD imagers little further out.
The bright star Betelgeuse just slightly out of focus. Note the doubled diffraction rings around Betelgeuse. Those should be single spikes. The focuser didn’t have enough travel to bring the camera to the needed distance away from the scope. Time to order a part!
The interesting thing about this telescope’s control software is the building of a pointing model. By taking a series of images all over the sky, the software does an astrometric reduction on each image and measures the slight variations in the telescope’s true pointing versus where it thinks it is pointing. This takes care of all sorts of interesting issues: flexure in the pier, telescope and mount, mirror sag or flop (none here!) and general pointing. After some 20 images, we were able to point to any object in the sky and have it show in the images we took… just like that image of Betelgeuse above.
Once the spacer arrived this past Wednesday, we went out to install it and then wait for darkness to arrive. It was a nice clear and very cold night. The goal was to build a large pointing model and take some images of famous deep sky objects. I also wanted to test out a start-up and shut-down procedure that I had typed up earlier in the week. That evening, we started everything up: the dome was homed and set to track the telescope. The CCD imager was on and cooled to -30ºC. The telescope was on, homed and tracking. Would it reach focus! Absolutely! It was spot-on perfect. We then built a large pointing model with over 100 images. Now the telescope would find and center objects of our choosing, and it would track them for better than five minutes without needing any autoguider corrections. This is quite the telescope!
We chose some of the iconic late winter deep sky objects to share with you for official first light. These are all composites of four filters:
- Luminance: a clear filter
- J-C Rc: which was used as the red channel
- J-C V: which was used as the green channel
- J-C B: which was used as the blue channel.
The V, B, and Rc filters are Johnson-Cousins photometric filters used for photometry, the science of measuring brightnesses, which can lead to our understanding of an object’s surface temperature and size, among other things.
You might want to dim the room lights to see the details. Also, click on the images to see in a larger format. Enjoy!
The Orion Nebula, M-42, a star birth region about 1300 light-years away. This can be seen with binoculars and small telescopes easily. It was almost too bright for our CCD imager!
M-82, the Cigar Galaxy, a starburst galaxy about 12 million light-years distant.
M-81, Bode’s Galaxy, about 12 million light-years away. This resides very close to M-82.
This is the Crab Nebula, M-1 in Taurus. This is a supernova remnant from a star that exploded back in 1054 A.D.
The next phase of this telescope’s use will be to collect scientific data. We have already taken images of U Gem and V Ori to calibrate our photometry and to see if we can produce good data for scientific publication. It has passed with flying colors thus far! | 0.839516 | 3.295586 |
Scientists at the South Pole have detected a collection of warp speed neutrinos from deep space that could help explain the origins of the universe.
The experts' 28 intergalactic subatomic particles were detected by the Cherenkov radiation emitted when they (unusually - most neutrinos go right through the Earth without stopping) hit something within a cubic kilometre of intrumented-up polar ice at the South Pole. They are thought to have originated from outside the Solar System, and likely from outside our galaxy, the Milky Way.
No oxide, just neutrino ... The particle-catching lab in Antarctica
Having identified the particles, the boffins believe that they can gain new insight into the workings of black holes, pulsars and other wonders of space that emit the subatomic particles.
The equipment is able to differentiate between neutrinos from outside the Solar System with those that may have originated from the Sun or the Earth's own atmosphere, which could reveal more about astrophysical phenomena billions of light-years from our home world. The extraterrestrial neutrinos screamed through the void almost at the speed of light before smashing in the Earth's snow.
"Neutrino observations are a unique probe of the universe’s highest-energy phenomena: Neutrinos are able to escape from dense astrophysical environments that photons cannot and are unambiguous tracers of cosmic ray acceleration," wrote the team in their scientific paper.
"As protons and nuclei are accelerated, they interact with gas and background light near the source to produce subatomic particles such as charged pions and kaons, which then decay, emitting neutrinos. We report on results of an all-sky search for these neutrinos at energies above 30 TeV in the cubic kilometer antarctic IceCube observatory between May 2010 and May 2012."
The team, based out of the University of Wisconsin, said that the discovery of subatomic particles in ice has been in the making for more than a quarter century. The Ice Cube itself, deep in the polar ice sheet, is operated from the famous Amundsen-Scott stilt base.
The discovery is only the second such observation of interstellar neutrinos by scientists. In 1987, a wave of particles from a supernova reached Earth and was observed by scientists. Since then, researchers have been looking for another source of the subatomic particles not generated by the Sun nor the Earth's own atmosphere.
"This is the first indication of very high-energy neutrinos coming from outside our solar system, with energies more than one million times those observed in 1987 in connection with a supernova seen in the Large Magellanic Cloud," said University of Wisconisn-Madison professor and IceCube principal investigator Francis Halzen.
"It is gratifying to finally see what we have been looking for. This is the dawn of a new age of astronomy." ®
Sponsored: Webcast: Ransomware has gone nuclear | 0.909163 | 4.080828 |
Astronomers have been fascinated with globular clusters ever since they were first observed in 17th century. These spherical collections of stars are among the oldest known stellar systems in the Universe, dating back to the early Universe when galaxies were just beginning to grow and evolve. Such clusters orbit the centers of most galaxies, with over 150 known to belong to the Milky Way alone.
One of these clusters is known as NGC 3201, a cluster located about 16,300 light years away in the southern constellation of Vela. Using the ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile, a team of astronomers recently studied this cluster and noticed something very interesting. According to the study they released, this cluster appears to have a black hole embedded in it.
The study appeared in the Monthly Notices of the Royal Astronomical Society under the title “A detached stellar-mass black hole candidate in the globular cluster NGC 3201“. The study was led by Benjamin Giesers of the Georg-August-University of Göttingen and included members from Liverpool John Moores University, Queen Mary University of London, the Leiden Observatory, the Institute of Astrophysics and Space Sciences, ETH Zurich, and the Leibniz Institute for Astrophysics Potsdam (AIP).
For the sake of their study, the team relied on the Multi Unit Spectroscopic Explorer (MUSE) instrument on the VLT to observe NGC 3201. This instrument is unique because of the way it allows astronomers to measure the motions of thousands of far away stars simultaneously. In the course of their observations, the team found that one of the cluster’s stars was being flung around at speeds of several hundred kilometers an hour and with a period of 167 days.
As Giesers explained in an ESO press release:
“It was orbiting something that was completely invisible, which had a mass more than four times the Sun — this could only be a black hole! The first one found in a globular cluster by directly observing its gravitational pull.”
This finding was rather unexpected, and constitutes the first time that astronomers have been able to detect an inactive black hole at the heart of a globular cluster – meaning that it is not currently accreting matter or surrounded by a glowing disc of gas. They were also able to estimate the black hole’s mass by measuring the movements of the star around it and thus extrapolating its enormous gravitational pull.
From its observed properties, the team determined that the rapidly-moving star is about 0.8 times the mass of our Sun and the mass of its black hole counterpart to be around 4.36 times the Sun’s mass. This put’s it in the “stellar-mass black hole” category, which are stars that exceeds the maximum mass allowance of a neutron star, but are smaller than supermassive black holes (SMBHs) – which exist at the centers of most galaxies.
This finding is highly significant, and not just because it was the first time that astronomers have observed a stellar-mass black hole in a globular cluster. In addition, it confirms what scientists have been suspecting for a few years now, thanks to recent radio and x-ray studies of globular clusters and the detection of gravity wave signals. Basically, it indicates that black holes are more common in globular clusters than previously thought.
“Until recently, it was assumed that almost all black holes would disappear from globular clusters after a short time and that systems like this should not even exist!” said Giesers. “But clearly this is not the case – our discovery is the first direct detection of the gravitational effects of a stellar-mass black hole in a globular cluster. This finding helps in understanding the formation of globular clusters and the evolution of black holes and binary systems – vital in the context of understanding gravitational wave sources.”
This find was also significant given that the relationship between black holes and globular clusters remains a mysterious, but highly important one. Due to their high masses, compact volumes, and great ages, astronomers believe that clusters have produced a large number of stellar-mass black holes over the course of the Universe’s history. This discovery could therefore tell us much about the formation of globular clusters, black holes, and the origins of gravitational wave events.
And be sure to enjoy this ESO podcast explaining the recent discovery: | 0.891865 | 4.048996 |
All stars are in motion, but some have a little more oomph than others. In recent years astronomers have identified a handful of stars that are moving so fast that they will someday flee the galaxy altogether.
On their way out, these escapees may tell us a thing or two about the nature of dark matter, the mysterious stuff that makes up nearly 85 percent of all matter in the universe. “No one knows what dark matter is,” says astrophysicist Warren Brown of the Smithsonian Astrophysical Observatory. Yet astronomers know it exerts a gravitational pull, which bends the paths of objects traversing the galaxy. Outbound stars thus act as tracers to reveal where dark matter is concentrated, and physicists can use that information to test competing theories of how it behaves.
The catch is that no one is quite sure what paths these stars are on. To use them as dark matter probes, astronomers need to know the stars' full trajectories, starting from the spot where they shot outward with such force. One possibility: the stellar speedsters were ejected by supernova explosions in the galaxy. Or perhaps they drew too close to the supermassive black hole at the Milky Way's center, which flung them out like stones in a slingshot. If that were the case, each star would trace back to a known point. “If they really come from the galactic center, then that's very valuable,” says University of Maryland astrophysicist Michael Boylan-Kolchin.
But how to tell where a star came from? Brown and his colleagues say that it boils down to a star's age, speed and position. Through a careful analysis of the spectrum of light from the newfound star HVS17 (short for hypervelocity star 17), the team determined it was 153 million years old and traveling about one million miles an hour through the outer Milky Way. A supernova-launched star would be much younger, having been ejected from its stellar cohort soon after forming by the detonation of a short-lived neighbor. The star's advanced age, then, argues for an origin near the galactic center, according to a recent study the researchers published in the Astrophysical Journal. New data from the European Gaia satellite should conclusively settle the star's origin and cast a sliver of light on dark matter. | 0.88495 | 3.97797 |
EUI was launched on board Solar Orbiter with an Atlas V 411 from launch complex 41 at Cape Canaveral, on 2020 February 9 23h03 local time (2020 February 10 05:03 CET).
Following the initial commissioning round of its systems and instruments, its first pass by the Sun will take place in June when the spacecraft will be at around half the distance of Earth’s orbit from the Sun.
During the remainder of the cruise phase, which lasts until November 2021, Solar Orbiter will perform two gravity-assist manoeuvres around Venus and one around Earth to alter the spacecraft's trajectory, guiding it towards the innermost regions of the Solar System. and also out of the plane of the Solar System to observe the Sun from progressively higher inclinations. This will result in the spacecraft being able to take the first ever images of the Sun's polar regions, crucial for understanding how the Sun 'works'.
During the cruise phase, Solar Orbiter will acquire in situ data, characterise and calibrate its remote-sensing instruments. The (first) closest solar pass will take place at the end of March 2022 at around a third of Earth’s distance from the Sun.
Having arrived in the near-vicinity of the Sun, the spacecraft will be in an elliptical orbit that initially takes 180 days to complete. This means it will make a close approach of the Sun every six months. During these close approaches, Solar Orbiter will pass within 43 million kilometres of the Sun’s surface, or about 60 solar radii.
Solar Orbiter's nominal science mission is set to last for four years. During this time, the inclination of the orbit is set to reach 17°. This will allow the spacecraft to image regions closer to the poles of the Sun for the first time (the Sun's polar regions are not visible from Earth). During its proposed extended mission phase, Solar Orbiter would lift its inclination even more, to 33°, bringing the polar regions into even more direct view.
Orbit images produced by ROB. | 0.831897 | 3.384727 |
Large Asteroid to Safely Pass Earth on Sept. 1
Asteroid Florence, a large near-Earth asteroid, will pass safely by Earth on Sept. 1, 2017, at a distance of about 4.4 million miles, (7.0 million kilometers, or about 18 Earth-Moon distances). Florence is among the largest near-Earth asteroids that are several miles in size; measurements from NASA’s Spitzer Space Telescope and NEOWISE mission indicate it’s about 2.7 miles (4.4 kilometers) in size.
“While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory in Pasadena, California. “Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began.”
This relatively close encounter provides an opportunity for scientists to study this asteroid up close. Florence is expected to be an excellent target for ground-based radar observations. Radar imaging is planned at NASA’s Goldstone Solar System Radar in California and at the National Science Foundation’s Arecibo Observatory in Puerto Rico. The resulting radar images will show the real size of Florence and also could reveal surface details as small as about 30 feet (10 meters).
Asteroid Florence was discovered by Schelte “Bobby” Bus at Siding Spring Observatory in Australia in March 1981. It is named in honor of Florence Nightingale (1820-1910), the founder of modern nursing. The 2017 encounter is the closest by this asteroid since 1890 and the closest it will ever be until after 2500. Florence will brighten to ninth magnitude in late August and early September, when it will be visible in small telescopes for several nights as it moves through the constellations Piscis Austrinus, Capricornus, Aquarius and Delphinus.
Radar has been used to observe hundreds of asteroids. When these small, natural remnants of the formation of the solar system pass relatively close to Earth, deep space radar is a powerful technique for studying their sizes, shapes, rotation, surface features and roughness, and for more precise determination of their orbital path.
JPL manages and operates NASA’s Deep Space Network, including the Goldstone Solar System Radar, and hosts the Center for Near-Earth Object Studies for NASA’s Near-Earth Object Observations Program, an element of the Planetary Defense Coordination Office within the agency’s Science Mission Directorate.
More information about asteroids and near-Earth objects can be found at:
For more information about NASA’s Planetary Defense Coordination Office, visit:
For asteroid and comet news and updates, follow AsteroidWatch on Twitter:
Jet Propulsion Laboratory, Pasadena, Calif.
(२०७४ भाद्र ३, शनिबार) १३:५५ मा प्रकाशित | 0.857109 | 3.422165 |
NASA has just announced that the Solar Probe Plus spacecraft is now renamed as the Parker Solar Probe in honor of the solar astrophysicist Dr. Eugene Parker. The mission to touch the Sun is the agency's first-ever mission to fly directly into the atmosphere of the star and probe into its brutally hot corona. One of the biggest questions the scientists are hoping to answer is why the Sun's corona or atmosphere much hotter than its surface?
[Image Source: NASA]
Dr. Eugene Parker is a renowned astrophysicist and serves as the S. Chandrasekhar Distinguished Service Professor Emeritus at the University of Chicago where the announcement was made today. He published an article in 1958 in the Astrophysical Journal entitled "Dynamics of the interplanetary gas and magnetic fields", which formed the basis of the then unknown phenomenon known as the solar wind.
— NASA Sun & Space (@NASASun) May 31, 2017
The highly bespoke NASA spacecraft will take an unprecedented plunge within 4 million miles to the Sun's atmosphere, exposing itself to scorching heat and radiation. Historically speaking, the Parker Solar Probe will be the first spacecraft to peek around the Sun at such close proximity that will be able to provide data on solar activity. By being placed in orbit around the sun, the spacecraft is expected to shed some light on decades-old questions about the physics of how stars work. NASA is scheduled to launch the solar probe in the summer of next year with a 20-day window that opens on July 31, 2018.
[Image Source: NASA]
Touching the Sun
Responsible for keeping us Earthlings alive, the Sun's influence stretches over and beyond the orbits of faraway celestial bodies like Neptune and Pluto. The relationship between the Sun and Earth is a critical connection and must, therefore, be fully understood by us. By probing close to the Sun, scientists will be able to study its unstable corona, which produces solar wind, flares, and coronal mass ejections. The giant ball of glowing hot gases also produce millions of tons of highly magnetized material with the potential to erupt from within the Sun at extraordinary speeds of several million miles an hour. So, collecting data from its atmosphere will enable NASA to understand and potentially forecast the space weather.
As the physics of the corona and inner heliosphere links the activity of the Sun with the environment and technological infrastructure of Earth, getting to grips with the science of the star's atmosphere will be highly beneficial for us. Some of the future advantages of understanding the Sun range from a vast field of industries like satellite communication, radiation exposure of aircraft flights, astronaut safety, and even pipeline erosion.
The Parker Solar Probe's mission to touch the Sun will inevitably revolutionize our understanding of the giant, dynamic star. For the spacecraft to successfully conduct its mission, it is protected by a 4.5-inch-thick (11.43 cm) carbon-composite shield. This body shield will give the spacecraft extreme resistant against the Sun's brutal heat and radiation.
[Image Source: NASA]
NASA has revealed that the spacecraft will do 24 orbits around the Sun's corona or atmosphere, which entails a number of hot and cold cycles. This requires the spacecraft to be robust enough to handle the extreme temperature changes and the carbon-composite to be designed exactly for that job. Nicola Fox, the Project Scientist of the Parker Solar Probe from the John Hopkins University Applied Physics Laboratory, describes the purpose of the spacecraft. "Parker Solar Probe is going to answer questions about solar physics that we’ve puzzled over for more than six decades. It’s a spacecraft loaded with technological breakthroughs that will solve many of the largest mysteries about our star, including finding out why the sun’s corona is so much hotter than its surface. And we’re very proud to be able to carry Gene’s name with us on this amazing voyage of discovery".
Because of the significant work of Eugene Parker on forming the basis of how stars interact with the worlds that orbit them, the mission's team are also planting photos of the astrophysicist and his famous research paper inside the spacecraft.
Currently, the solar probe is undergoing tests and the most significant test it will go through soon is the thermal environment simulation that will assess its heat resisting capabilities.
"The solar probe is going to a region of space that has never been explored before", said Parker. "It’s very exciting that we’ll finally get a look. One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are".
To find out more about the mission and the Parker Solar Probe visit NASA's website by clicking on the link below. | 0.840711 | 3.640182 |
A type of landscape on Mercury known as “chaotic terrain” might have released materials stored underground for eons.
Since the Mariner 10 probe approached Mercury in 1974, planetary scientists have been puzzled by a particular patch of land found on the opposite side of a large impact crater known as Caloris Basin. In the images Mariner 10 obtained, this land appeared like a jumbled area of hilly and uneven ground. Scientists dubbed it “chaotic terrain.”
For decades, the main idea for how this chaotic terrain formed had to do with the impact that made the large Caloris Basin. Massive seismic ripples caused by the impact could have resonated on the opposite side of the small world, causing massive quakes.
But a new study suggests a different origin. Alexis Rodriguez (Planetary Science Institute) and colleagues think that the terrain might have been made chaotic more gradually, as volatile elements susceptible to turn into gas that were stored underground evaporated over time. The team found that once enough of these volatiles escaped, the landscape deflated, creating irregular ground with drops of more than one kilometer. Their findings appear online March 16th in Scientific Reports.
“We found that chaotic terrain landscapes look like they had suffered significant relief losses, like you might have a mountain and suddenly half of it is missing,” Rodriguez explained. “But it isn’t like it has sunk into the terrain: it has just disappeared.”
Given that Mercury is a dry, airless world, Rodriguez says, there’s nowhere else for the materials to go — they must have turned to gas and gone away.
A Volatile World
The new work is based on observations made by NASA’s Messenger spacecraft, which orbited Mercury between 2011 and 2015 and mapped its terrain in unprecedented detail. The probe also determined the chemical makeup of the world’s surface, finding many volatile elements such as sulphur, chlorine, and potassium on its surface.
The presence of these elements surprised planetary scientists, who thought that the Sun’s proximity should long ago have stripped away any volatiles that Mercury formed with. Now, the new research suggests that volatile-rich layers could have existed for far longer than expected below the surface.
The researchers find evidence supporting their claim in crater counts and in ejecta rays. Counting the craters present in the chaotic terrain provides a proxy of its age, and the researchers obtain an age of 1.8 billion years — at least 2 billion years younger than the Caloris Basin.
Moreover, ejecta rays from recent craters disappear in some areas of the chaotic terrain, indicating that the ground has been degassing and changing until very recently, Rodriguez explained.
The team also found that chaotic terrain is not limited to the region opposite the Caloris Basin. Areas with similar texture don’t appear to be related to large impacts and are distributed from the poles to the equator. It’s possible that a volatile-rich crust might cover the whole planet.
“It's a fascinating work and I think it will spur quite a lot of research by other people,” said geochemist David Blewett, (Johns Hopkins University's Applied Physics Laboratory), who wasn’t involved in the new study.
So what are in those volatile-rich layers? Rodriguez and his team consider several possibilities, one of which includes water in the mix.
“We aren’t talking about water ice — although it might have been at some point — but water that might be contained within phyllosilicates or maybe hydrated salts (brines),” Rodriguez said. “It doesn’t mean there could be lakes or caves filled with water, it means that water could have been trapped within mineral structures.”
If his team can prove the existence of water on Mercury, even in minerals, it could have implications for our definition of habitability. “Habitability and presence of life are two different things,” he adds. “I don’t think life has appeared in Mercury, but a prebiotic chemistry is much more likely.”
The same principle could apply to exoplanets, specifically small planets orbiting longer-lived stars such as red dwarfs. “Life might have a chance to appear, simply due to the amount of time that those systems could be stable,” Rodriguez says. “It makes it more likely, not definitive, but it surely increases the chances.”
“Yeah, I suppose,” Blewett counters, “but again, you know, Mercury doesn't have an atmosphere. It probably didn't have an atmosphere back at that time. And it seems unlikely that there would have been areas with the water and stability for the type of life as we know it.”
Confirmation of volatile-rich minerals, if there are any, could come from the BepiColombo spacecraft, due to arrive at the innermost planet in 2025 (after a flyby past Earth next week). BepiColombo will carry instruments that can survey Mercury as Messenger couldn’t, and will provide the ultimate test of the new idea. | 0.866874 | 3.836977 |
Our Solar System may be home, but researchers are now discovering that it's not really much like the other kids. According to a survey of 909 planets orbiting 355 stars, our home planetary system is a little on the dishevelled side - and others are a lot more orderly.
A study led by astrophysicist Lauren Weiss of the Université de Montréal has found that, in other solar systems with multiple planets, the planets are much more similar in size to one another, and their orbits are more evenly spaced.
If you look at a diagram of the Solar System, you can see that we're sort of all over the shop. We have planets of all shapes and sizes, and the distances between the orbits around the Sun vary wildly.
Scientists used to think this was probably pretty normal, but as we have learned more about exoplanets - thanks in large part to the planet hunting space observatory Kepler - several old assumptions have been challenged.
Using data from some of the thousands of exoplanets located using Kepler, Weiss and her team used the W. M. Keck Observatory in Mauna Kea, Hawaii to obtain high-resolution spectral data of 1,305 stars hosting 2,025 planets.
Using these data, the team was able to measure the sizes of the planets transiting, or passing in front of, their host stars. As they do so, the light from the star dims slightly, and it is the properties of this dimming that allows the team to calculate the planet-to-star radius ratios for every orbiting body.
For the study, the team focussed on 909 planets divided between 355 multi-planet systems, located mostly between 1,000 and 4,000 light-years from Earth.
And they tended to fall into two patterns, which the researchers were not expecting. Firstly, the planets tended to be around the same size as their neighbours, meaning planet sizes in exoplanet systems are often roughly uniform.
Secondly, the distances between planetary orbits were fairly even.
"The planets in a system tend to be the same size and regularly spaced, like peas in a pod. These patterns would not occur if the planet sizes or spacings were drawn at random," Weiss said.
In other words, if the size of one planet or orbital distance in a system is known, astronomers could make a more accurate prediction about the size or orbital distance of another planet than drawing a random planet out of a hat to construct an artificial planet system.
They also found only a very weak correlation between star mass and planet radius, which means it's probably not stellar mass that enforces planet size.
And, they found, when there is some size variation in a planetary system, the planet closest to the star will be smaller, especially if the planet has a short orbital period - possibly because of photoevaporation.
This finding has implications about how planetary systems form - and gives us some clues as to how our budding Solar System was different.
The most accepted hypothesis currently is that the protoplanetary disc of dust and debris that surrounds a newborn star gradually coalesces and accretes into planetary bodies. If the disc is relatively even, it's reasonable to conclude that even planetary systems, such as those observed by the researchers, can evolve from this disc.
So what happened with the Solar System? The researchers believe Jupiter and Saturn had something to do with it. The two gas giants formed early in the Solar System's history, and there's evidence to suggest that they disrupted its early structure in some way.
So a more uniform planetary system is one that probably has had relatively few disruptions. In order to test this, the team's next project will be to look for Jupiter-sized exoplanets in multi-planet systems, and see if theses systems are consistent with the hypothesis.
The team's research has been published in The Astronomical Journal. | 0.887275 | 3.806584 |
The Voyager 1 has truly gone where no man has gone before – the brave shuttle is now more than 11 billion miles (18 billion kilometers) from the sun, closer and closer to becoming the first man-made object to reach interstellar space.
To me, it’s just baffling that we sent something 18 billion kilometers from the sun – just so you can make an idea, the distance between the Sun and the Earth is approximately 150 million km; and it’s still providing valuable data! A new research using data from the Voyager 1 showed was published in the journal Science today, offering details on the last region the spacecraft will cross before it leaves the heliosphere, or the bubble around our sun, and enters interstellar space.
Currently, Voyager 1 is in a region called the ‘magnetic highway’ – a region of charged particles which exists because our sun’s magnetic field lines are connected to interstellar magnetic field lines.
“This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind’s most distant scout,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “If you looked at the cosmic ray and energetic particle data in isolation, you might think Voyager had reached interstellar space, but the team feels Voyager 1 has not yet gotten there because we are still within the domain of the sun’s magnetic field.”
So when will Voyager actually leave the solar system and reach interstellar space? It’s not really certain – it’s not like there’s a big border around the solar system. Astronomers believe it will take at least a few months, and possibly a couple of years. The Voyager 1 spacecraft was launched by NASA on September 5, 1977. | 0.825572 | 3.19501 |
Hang on for a lesson in solar dynamics – Earth is experiencing a solar sector boundary crossing. Let me explain….
The sun produces wind (currently 410.9 Km/second) that blasts across the cosmos. Just like Earth, our Sun has a magnetic field – known as the interplanetary magnetic field (IMF). Whipped into a spiral rotation, wind driven IMF rotates in one direction. It divides into spiral sections pointing to and away from the sun along the ecliptic plane ( a direct line between Earth and the Sun). The edge of this swirling mass has a surface separating polarities of planetary and solar magnetism called the heliosphere current sheet.
Earth’s magnetic field points north at the magnetopause (the point of contact between our magnetosphere and the IMF). If the IMF happens to point south at contact (scientific term, southward Bz) the two fields link causing partial cancellation of Earth’s magnetic field – in other words, opening a temporary door for solar energy to enter our atmosphere. Welcome solar sector boundary crossing – a phenomenon born of high solar wind and coronal mass ejections (CME’s – aka solar flares).
It takes 3 or 4 days for magnetism to sort itself out – in the meantime, and barring the occasional high frequency radio disruption, wonky GPS and cell phones, peppered with sudden power grid failure events – we’re treated to kick ass auroras.
Ponder Earth’s magnetic field as a shield protecting us from harmful cosmic radiation. Known as “geomagnetic” because it starts at our solid iron outer core, (miles below the surface) and reaches to the outer atmosphere. (creating a magnetosphere, the point in space beyond the ionosphere where charged particles protect us from solar wind and radiation). Without it – our ozone layer would wither, and we would succumb to ultraviolet radiation. In other words, life could not exist.
When strong solar winds impact the magnetosphere, they “distort” our magnetic field creating “openings” – the near side to the sun being “compressed” and far side of the planetary field is bulged outward.
As the charged particles of solar winds and flares hit the Earth’s magnetic field, they travel along the field lines.
Some particles get deflected around the Earth, while others interact with the magnetic field lines, causing currents of charged particles within the magnetic fields to travel toward both poles — this is why there are simultaneous auroras in both hemispheres. (These currents are called Birkeland currents after Kristian Birkeland, the Norwegian physicist who discovered them — see sidebar.)
When an electric charge cuts across a magnetic field it generates an electric current (see How Electricity Works). As these currents descend into the atmosphere along the field lines, they pick up more energy.
When they hit the ionosphere region of the Earth’s upper atmosphere, they collide with ions of oxygen and nitrogen.
The particles impact the oxygen and nitrogen ions and transfer their energy to these ions.
The absorption of energy by oxygen and nitrogen ions causes electrons within them to become “excited” and move from low-energy to high-energy orbitals (see How Atoms Work).
When the excited ions relax, the electrons in the oxygen and nitrogen atoms return to their original orbitals. In the process, they re-radiate the energy in the form of light. This light makes up the aurora, and the different colors come from light radiated from different ions.
Two recent solar events – CME’s (coronal mass ejection) are poised to deliver Aurora magic in regions unaccustomed to their magnificence. Solar wind from the first eruption have arrived, with stronger consequences from the second ejection expected in the next few hours. What this means is Auroras could be visible far below normal latitudes. Some scientists project as far south as Mexico.
If you feel so inclined – go outside, cast your gaze northward, and watch for tell tale green ripples across the sky. Best time to view is between midnight and dawn – obviously clear skies away from city lights are advisable.
Our sun has been busy, purging plasma with the vengeance of Thor. A X-1 flare from sunspot AR1875 on Oct. 28 is the third X-class flare since Oct. 25. This follows three M-class flares since Oct. 20. None of the recent flares are likely to give any direct hits to our magnetic field; instead “glancing blows” are likely to stir up geo-magnetic storms, resulting in spectacular auroras.
For the next 24 hours, Solar Dynamics Observatory predicts a 75% chance of M-class and 30% chance of more X-class flares. My secret wish is for solar hiccups to last long enough for my trip next week to the Canadian prairies; the home of endless, dark, crystal clear skies. A place to take in the majesty of Northern Lights.
Solar activity makes me giddy; I prickle with school girl excitement at the mere mention of an earth directed CME. I knew the sun was getting a little uppity – a visit to http://spaceweather.com/ when I got home from work set my heart a flutter. Our sun has been busy – three flares between Oct. 20 – 22 have apparently merged into one; promising to light up our magnetic field with auroras. Another powerful M-9 class flare hurled earthward yesterday, arrival time as yet unknown.
Courtesy NASA – Solar Dynamics Observatory
Sunspots AR1875 and 1877 are ready to speak their minds – both strutting their stuff – ready to make a statement. Predictions of activity in the next 24 hours may not be earth shattering – 40% chance of M-class and 10% chance of X-class flares – still enough of a magnetic storm for ridiculous northern lights.
Meanwhile, Comet C/2012X1 exploded 450 million Km’s from earth. Of little significance to our little corner of the universe, yet worthy of a look low on the eastern horizon an hour or so before sunrise if you happen to have a telescope.
This is not a warning, hysterical plea to take cover or recruiting post for the tin foil hat club – simply a heads up for Northern hemisphere sky watchers. Sunspot AR1865 sent an M1 class flare our way, it should reach earth’s magnetic field this evening. Not powerful enough to cause a bad day – even though it was earth directed – the magic is expected to unfold in spectacular auroras.
Those who have witnessed Aurora’s spell understand her soul restoring powers. Those who haven’t can only hope that one day she will allow you to witness her dance across the northern sky. If you happen to find yourself in a dark place, away from city lights; gaze upwards tonight – if you’re lucky, Aurora will dance for you.
AR1748 is one pesky sunspot; still beating its chest, and threatening to show us who’s boss. With odds of eruptions now up to 80% for M-class and 60% for X in the next 24 hours – 1748 unleashed another X class flare today – in case the three X flares of 1.7, 2.8, and 3.2 the previous day hadn’t made us stand up and take notice. As AR1748 turns towards earth, today’s X-1 is expected to deliver a little slap – most likely in the form of geo-magnetic disturbances responsible for crazy beautiful auroras. Ar1748 has produced more X-class flares in the last few days than all other sunspots this year combined.
NASA Solar Dynamics Observatory – photo of AR 1748 taken on May 16
I’ve been a space weather nerd for a while and have never seen an 80% chance of M-class and 40% chance of X-class flares in the next 24 hours. Our sun is flexing muscle with the most intense solar activity this year. Sunspot AR 1748 let loose significant X class eruptions of 1.7, 2.8, and 3.2 in the last 24 hours. Take it from me – this is crazy. The good news is none were “earth directed”, no incoming CME (coronal mass ejection) is anticipated for now. The bad news – while researching when 1748 will face earth I stumbled upon a wordpress blog proclaiming it the beginning of the “rapture”. My decision to retreat, despite every fibre in my being screaming “post a comment” – left me shaking, incensed, reaching for a cocktail, and ultimately validated in my AR1748 raised eyebrow. When all is said and done – not only have I never seen such crazy solar activity in a short period of time, I’ve never seen it attributed to the rapture. All the affirmation I need to know I’m not pondering fairy dust. FYI -AR1748 will be earth directed in a few days.
Bookmark this link to spaceweather, start paying attention to solar reports, and send your tin foil hats to those anticipating the “rapture”, just be sure to tuck a little tin foil into that emergency kit at the top of your “to do” list. | 0.80981 | 3.876809 |
Scientists Just Discovered The Largest Batch of Exoplanets In A Single Sitting Thanks To A Technical Error
We're still waiting for NASA's TESS satellite to significantly grow the list of known exoplanets, but that doesn't mean that scientists are twiddling their thumbs until the data rolls in. According to reports, an international team using data from various telescopes including Kepler recently found a large cache of 44 confirmed planets out of a pool of 72 candidates - one of the single biggest hauls in history - and it was thanks in part to a technical problem back in 2013.
According to Motohide Tamura, a professor at the University of Tokyo, something went wrong with Kepler five years ago that turned out to be a happy accident. "Two out of the four control-reaction wheels failed, which meant Kepler couldn't perform its original mission to stare at one specific patch of the sky," Tamura said in a statement. "This led to its contingent mission, 'K2' — our observations came from campaign 10 of this mission. We're lucky Kepler continues to function as well as it does." In a report published in The Astronomical Journal, Tamura and his team provided more details about the find, including approximations of their varying sizes. "It was also gratifying to verify so many small planets," said University of Tokyo graduate student and the study's lead author John Livingston in a statement. "Sixteen were in the same size class as Earth, one in particular turning out to be extremely small — about the size of Venus — which was a nice affirmation as it's close to the limit of what is possible to detect."
Another interesting discovery about the exoplanets is that four of them complete their orbits around their hosts in less than 24 hours, which means that a year passes on their surface in the time that it takes a day to pass here on Earth. Among the 44 are 18 planets that scientists want to pay special attention to because they are believed to be in multi-planet systems. "The investigation of other solar systems can help us understand how planets and even our own solar system formed," said Livingston.
Explore the solar system below... | 0.833689 | 3.074964 |
NASA intern Jennifer Briggs, a physics student at Pepperdine University in California, discovered a new type of aurora in three-year-old footage of the Arctic Sky. Scientists were able to correlate the never-before-seen aurora to a sudden compression in Earth's magnetic field.
During an internship at NASA's Goddard Space Flight Center in Maryland, Briggs came across the aurora in photos from ground-based, all-sky cameras mounted in Svalbard, Norway, near the Arctic Circle.
The newly found type of aurora was short-lived and had a rare spiral that caught her attention. NASA said this made Briggs think of a seashell-- its twisting motions indicated the magnetosphere had a major disturbance. Indeed, data from NASA's Magnetospheric Multiscale mission (MMS) provided the dramatic compression of the magnetosphere.
Researchers were left puzzled as to why this magnetic "crunch" occurred, or why it forced the magnetic field to decrease in size so abruptly. But since there were no solar explosions to push against the magnetic field at that time, researchers believe it may have been triggered by an unprecedented storm in the area where Earth's magnetic field meets particles from the Sun.
"This motion is something that we've never seen before. This eastward and then westward and then spiraling motion is not something that we've ever seen, not something we currently understand," said Briggs.
According to the intern, the edge of the magnetosphere moved toward the planet's surface by 25 000 km (15 534 miles) in less than two minutes when this certain aurora took place-- it was over four times the Earth's radius.
To put it into perspective, it would take a commercial jet around 27 hours to fly that distance.
"You can imagine someone punching Earth’s magnetic field," Briggs described. "There was a massive, but localized compression."
The rapid dash of charged particles during an aurora borealis can cause disruption on electronic communications, GPS, move satellites out of orbit, put astronauts at risk, and even eradicate power grids if the explosion is massive enough.
The aurora's vibrant lights are a product of collisions between electrically-charged particles from the Sun and gases in Earth's atmosphere like nitrogen and oxygen.
Our planet's magnetic field usually deflects these charged particles. However, since the field is weaker at the poles, particles sneak through, resulting in aurora borealis near the North Pole and aurora australis near the South Pole.
Studying auroras enable scientists to observe what's happening in the ionosphere, and even farther out into the magnetosphere.
Featured image credit: Fred Sigernes/Kjell Henriksen Observatory, Longyearbyen, Norway/Joy Ng | 0.836583 | 3.839182 |
When most people think about the search for alien life, the first thing that usually pops into mind is SETI (Search for Extraterrestrial Intelligence). Primarily a search for extraterrestrial radio signals, another more recent facet of SETI is now looking for laser pulses as a conceivable means of communication across interstellar distances. But now, a third option has been presented: looking for sources of artificial light on the surfaces of exoplanets, like the lights of cities on Earth.
According to Avi Loeb at the Harvard-Smithsonian Center for Astrophysics, “Looking for alien cities would be a long shot, but wouldn’t require extra resources. And if we succeed, it would change our perception of our place in the universe.”
Like the other SETI initiatives, it relies on an assumption that an alien civilization would use technologies that are similar to ours or at least recognizable. That assumption itself has been the subject of contentious debate over the years. If an alien society was thousands or millions of years more advanced than us, would any of its technology even be recognizable to us?
That aside, how easy (or not) would it be to spot the signs of artificial lighting on an alien planet light-years away from us? The suggestion is to look at the changes in light from an exoplanet as it orbits its star. Artificial light would increase in brightness on the dark side of a planet as it orbits the star (as the planet goes through its phases, like our Moon or other planets in our own solar system), becoming more visible than any light that is reflected from the day side.
That type of discovery will require the next generation of telescopes, but today’s telescopes could test the idea, being able to find something similar as far out as the Kuiper Belt in our solar system, where Pluto and thousands of other small icy bodies reside. As noted by Edwin Turner at Princeton University, “It’s very unlikely that there are alien cities on the edge of our solar system, but the principle of science is to find a method to check. Before Galileo, it was conventional wisdom that heavier objects fall faster than light objects, but he tested the belief and found they actually fall at the same rate.”
The paper has been submitted to the journal Astrobiology and is available here. | 0.845359 | 3.142542 |
A Canadian-led team of scientists has found the second repeating fast radio burst (FRB) ever recorded. FRBs are short bursts of radio waves coming from far outside our Milky Way galaxy. Scientists believe FRBs emanate from powerful astrophysical phenomena billions of light years away.
The discovery of the extragalactic signal is among the first, eagerly awaited results from the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a revolutionary radio telescope inaugurated in late 2017 by a collaboration of scientists from McGill, the University of British Columbia, University of Toronto, Perimeter Institute for Theoretical Physics, and the National Research Council of Canada.
In a resounding endorsement of the novel telescope’s capabilities, the repeating FRB was one of a total of 13 bursts detected over a period of just three weeks during the summer of 2018, while CHIME was in its pre-commissioning phase and running at only a fraction of its full capacity. Additional bursts from the repeating FRB were detected in following weeks by the telescope, which is located in British Columbia’s Okanagan Valley.
Discovery of second repeating FRB suggests more exist
Of the more than 60 FRBs observed to date, repeating bursts from a single source had been found only once before – a discovery made by the Arecibo radio telescope in Puerto Rico in 2015.
“Until now, there was only one known repeating FRB. Knowing that there is another suggests that there could be more out there. And with more repeaters and more sources available for study, we may be able to understand these cosmic puzzles – where they’re from and what causes them,” said Ingrid Stairs, a member of the CHIME team and an astrophysicist at UBC.
Before CHIME began to gather data, some scientists wondered if the range of radio frequencies the telescope had been designed to detect would be too low to pick up fast radio bursts. Most of the FRBs previously detected had been found at frequencies near 1400 MHz, well above the Canadian telescope’s range of 400 MHz to 800 MHz.
The CHIME team’s results – published January 9 in two papers in Nature and presented the same day at the American Astronomical Society meeting in Seattle – settled these doubts, with the majority of the 13 bursts being recorded well down to the lowest frequencies in CHIME’s range. In some of the 13 cases, the signal at the lower end of the band was so bright that it seems likely other FRBs will be detected at frequencies even lower than CHIME’s minimum of 400 MHz.
FRB sources likely to be in ‘special places’ within galaxies
The majority of the 13 FRBs detected showed signs of “scattering,” a phenomenon that reveals information about the environment surrounding a source of radio waves. The amount of scattering observed by the CHIME team led them to conclude that the sources of FRBs are powerful astrophysical objects more likely to be in locations with special characteristics.
“That could mean in some sort of dense clump like a supernova remnant,” says team member Cherry Ng, an astronomer at the University of Toronto. “Or near the central black hole in a galaxy. But it has to be in some special place to give us all the scattering that we see.”
A new clue to the puzzle
Ever since FRBs were first detected, scientists have been piecing together the signals’ observed characteristics to come up with models that might explain the sources of the mysterious bursts and provide some idea of the environments in which they occur. The detection by CHIME of FRBs at lower frequencies means some of these theories will need to be reconsidered.
“Whatever the source of these radio waves is, it’s interesting to see how wide a range of frequencies it can produce. There are some models where intrinsically the source can’t produce anything below a certain frequency,” says team member Arun Naidu of McGill.
“[We now know] the sources can produce low-frequency radio waves and those low-frequency waves can escape their environment, and are not too scattered to be detected by the time they reach the Earth. That tells us something about the environments and the sources. We haven’t solved the problem, but it’s several more pieces in the puzzle,” says Tom Landecker, a CHIME team member from the National Research Council of Canada.
CHIME is a revolutionary new telescope, designed and built by Canadian astronomers. “CHIME reconstructs the image of the overhead sky by processing the radio signals recorded by thousands of antennas with a large signal processing system,” explains Perimeter Institute’s Kendrick Smith. “CHIME’s signal processing system is the largest of any telescope on Earth, allowing it to search huge regions of the sky simultaneously.”
CHIME is a collaboration of over 50 scientists led by the University of British Columbia, McGill University, University of Toronto, Perimeter Institute, and the National Research Council of Canada (NRC). The $16-million investment for CHIME was provided by the Canada Foundation for Innovation and the governments of British Columbia, Ontario and Quebec, with additional funding from the Dunlap Institute for Astronomy and Astrophysics, the Natural Sciences and Engineering Research Council and the Canadian Institute for Advanced Research. The telescope is located in the mountains of British Columbia’s Okanagan Valley at the NRC’s Dominion Radio Astrophysical Observatory near Penticton. CHIME is an official Square Kilometre Array (SKA) pathfinder facility.
Read the papers
Observations of fast radio bursts at frequencies down to 400 megahertz, CHIME FRB Collaboration, Nature, published online Jan. 9, 2019.
The source of a second repeating fast radio burst, CHIME FRB Collaboration, Nature, published online Jan. 9, 2019.
Watch the video below for a primer on the Chime telescope and fast radio bursts. (Video made last year for CHIME’s inauguration) | 0.828315 | 3.872507 |
At first, the probe checked itself over, taking snapshots of its dusty feet and freshly unfurled solar arrays, ensuring all was present and correct following its 422m-mile journey and high-speed descent on to the northern plains of Mars in the early hours of yesterday.
Then the real work began. The robotic arm flexed and swivelled, bringing the camera up and around to gaze at the alien landscape. Two hours later, Nasa's mission controllers had been sent the first pictures ever to be taken within the arctic circle of the red planet.
The $420m (£212m) Phoenix mission, which settled on Mars at 00.53 BST yesterday, represents a major milestone in Nasa's exploration of the solar system and its search for evidence of life elsewhere. Not since the Viking landers touched down in 1976 has a probe landed softly on the planet, using rocket thrusters to slow its descent. More significantly, Phoenix is expected to become the first spacecraft to touch water on another planet.
At Nasa's Jet Propulsion Laboratory in California last night, the final moments before landing were tense, but at every step the Phoenix probe matched or exceeded expectations. As it hurtled into the atmosphere, engineers foresaw a communications blackout as the searing plasma around the probe's heat shield blocked their radio link. When the moment came, the probe kept in touch all the way down, settling at a near-perfect 0.25-degree angle in the Vastitas Borealis, an ancient plain near the north pole.
"In my dreams, it couldn't have gone as perfectly as it did," said Barry Goldstein, the project manager on the Phoenix mission. "I'm in shock. Never in rehearsal did it go so well."
Yesterday, Nasa engineers began analysing the first of the images, some showing the intriguing polygonal patterns that scar the Martian arctic. One of the probe's mission tasks is to dig beneath the frigid surface to collect water ice and soil, which will be analysed by the probe's onboard laboratory. Mission controllers will be looking for signs of organic compounds in the water that could indicate that the now harsh environment was once hospitable, and even habitable.
"We see the lack of rocks that we expected, we see the polygons that we saw from space, we don't see ice on the surface, but we think we will see it beneath the surface," said Peter Smith, the principal investigator on the mission at Arizona University.
The landing marks the US space agency's first return to Mars since its twin rovers, Spirit and Opportunity, touched down in January of 2004.
"This is the first chance we have had to actually collect and analyse water on the Red Planet," said Keith Mason, head of Britain's Science and Technology Facilities Council.
"If we find water ice below the Martian surface we may also be able to find evidence of past life on the planet."
Over the next eight days, the probe will continue to take measurements of the Martian atmosphere and soil before using its two-metre-long robotic arm to dig down to what lies beneath. Onboard cameras and a weather station will record information about the probe's changing environment as night turns to day and the Martian seasons turn. The mission is expected to last three months, after which the arrival of winter will see light levels fall too low to replenish the Phoenix probe's batteries.
"We're all so relieved that Phoenix has managed to land safely," said Tom Pike, head of the UK Phoenix team at Imperial College London. "The descent and landing phase of the mission is one of the most tricky and hazardous. It's great to have made it down in one piece and now we can get to work uncovering more of the Red Planet's secrets."
The London team developed tiny silicon sheets that will hold dust and soil samples for the probe to examine with high-resolution microscopes.
Another of the probe's tasks is to monitor changes in the polar weather and how it interacts with the land and atmosphere above. In the arctic summer on Mars, scientists believe water vapour is released from ice at the polar caps and into the atmosphere.
David Catling, a scientist on the team from Bristol University, said: "Our priority now is to find out if there is ice below the dirt and whether it got there recently, or it is a frozen remnant from an ancient time when liquid water may have rippled across this part of Mars."
As the name suggests, the 350kg Phoenix probe arose from the embers of previous Mars missions, themselves failed or shelved in 1999 and 2001, but useful for their spare parts, from which the spacecraft was put together. | 0.817599 | 3.423387 |
The Moon and Venus will share the same right ascension, with the Moon passing 0°24' to the south of Venus. The Moon will be 3 days old.
From Fairfield, the pair will be difficult to observe as they will appear no higher than 11° above the horizon. They will become visible around 20:43 (EDT) as the dusk sky fades, 11° above your western horizon. They will then sink towards the horizon, setting 1 hour and 27 minutes after the Sun at 21:49.
The Moon will be at mag -9.9, and Venus at mag -4.5, both in the constellation Leo.
The pair will be close enough to fit within the field of view of a telescope, but will also be visible to the naked eye or through a pair of binoculars.
A graph of the angular separation between the Moon and Venus around the time of closest approach is available here.
The positions of the two objects at the moment of conjunction will be as follows:
|Object||Right Ascension||Declination||Constellation||Magnitude||Angular Size|
The coordinates above are given in J2000.0. The pair will be at an angular separation of 34° from the Sun, which is in Gemini at this time of year.
|The sky on 18 July 2015|
2 days old
All times shown in EDT.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|12 Jul 2015||– Venus at greatest brightness|
|08 Aug 2015||– Venus at aphelion|
|15 Aug 2015||– Venus at inferior solar conjunction|
|20 Sep 2015||– Venus at greatest brightness| | 0.898291 | 3.45968 |
To celebrate NASA’s 60th anniversary this year, the agency partnered with the National Symphony Orchestra to present a concert in Washington entitled “NSO Pops: Space, the Next Frontier.” NASA mission images complemented performances of space-inspired music in the Kennedy Center’s concert hall, including Claude Debussy’s “Clair de Lune” (“Moonlight”), with a video of the Moon created by NASA science visualizer Ernie Wright.
At NASA’s Goddard Space Flight Center in Greenbelt, Maryland, Wright works in the Scientific Visualization Studio, using NASA data to create accurate visuals of celestial bodies. Wright made the lunar imagery accompanying “Clair de Lune” with data from the Lunar Reconnaissance Orbiter (LRO).
This visualization attempts to capture the mood of Claude Debussy’s best-known composition, Clair de Lune, along with visuals of the moon captured by NASA’s Lunar Reconnaissance Orbiter. Credits: NASA/LRO/Ernie Wright
Since its 2009 launch, LRO has harvested data on the Moon’s radiation, chemistry, temperature and topography. The shape of the lunar terrain is measured by LRO’s laser altimeter, LOLA (Lunar Orbiter Laser Altimeter). “The principle behind measuring the topography of the Moon is fairly straightforward,” said Noah Petro, LRO project scientist. “We fire a laser from the spacecraft to the surface of the Moon, and measure the time it takes that pulse to go from spacecraft to surface and back.”
The longer the laser takes to bounce back to LRO, the farther away the lunar surface. Over many years, a topographic map of the entire Moon is built up, creating the most accurate map of a celestial body’s topography ever created. Wright then uses this map and images of the Moon in the same 3D visualization software preferred by animators such as those at Pixar to make digital models. “What Ernie has done is that he drapes the images on top of the topography,” Petro said.
Topography was Wright’s biggest challenge. “The thing about the Moon is that the shadows are everything. If you don’t do that well, you’ve pretty much lost the game — there aren’t vibrant colors like on the Earth or Jupiter or Saturn,” Wright said.
Wright’s video displays breathtaking views of lunar landmarks, beginning with a sunrise dragging shadows across the surface and ending with sunsets lengthening the darkness along the same geography. The music, Wright said, is “melancholy, solitary and contemplative, as if you’re alone, walking through a garden in the moonlight.” The result, with serene music that breathes in time with crisp visuals, is a perspective on our Moon that Debussy could have only dreamed of when he tried to capture the essence of the body that dominates the night sky.
About Ernie Wright
Names of lunar landmarks are lightly penciled on one of Wright’s paper sheet music copies of “Clair de Lune” (or “Clair,” as he refers to it). Wright comes from a musical family, but he swears the gift passed him over. “I can barely read music,” Wright said, laughing. “And it wasn’t until I had listened to ‘Clair’ a few times before I thought, ‘Oh, I can follow that.’”
Wright’s job exists at the confluence of hard data and natural beauty. His formal background is in computer science, and he has his own backyard telescope. “I look at stuff, I read Sky & Telescope magazine,” he said.
For the past 10 years at Goddard, however, knowledge of astronomy and planetary and Earth sciences has become crucial for Wright. Communication with scientists is an integral part of the work being done by those in the Scientific Visualization Studio at Goddard.
“We have to speak to the scientists credibly and understand what they’re saying,” Wright said. “We need to reach up to their level of understanding and pull down what we need to convey to other people.”
Wright specializes in utilizing data from NASA missions, such as LRO, and representing them visually. Much of the work he does lies in organization of the data so that it can be understood by the 3D animation software he uses.
Wade Sisler, executive producer in Goddard’s Office of Communications, came to Wright with the proposal that visuals accompany the music for “Clair de Lune.” “Ernie’s work was legendary at NASA,” Sisler said. Wright had also crafted lunar visualizations for what would be Goddard’s viral “Tour of the Moon in 4K” video, so Sisler said that asking Wright to help “just seemed natural.” The video became “a moving Ansel Adams portrait. The richness of the tones and the dynamic range in the scenes made it so beautiful and so different,” Sisler said.
Wright’s work is not limited to pleasing visual displays. Ten years ago, one of Wright’s first projects at NASA involved the search for lunar water. LRO’s sister mission, the Lunar Crater Observation and Sensing Satellite (LCROSS), was a spacecraft designed to collide with the Moon. The impact had to be visible through Earth-based telescopes: astronomers would analyze the emitted light to look for the presence of water. Wright was called upon to help the observatories by visualizing potential impact sites, especially in shadowed regions where water ice could be found.
“They were making this decision as they were flying to the Moon,” Wright said. “They were relying a lot on LRO’s preliminary data to guide them to the best location. I was able to use that data to render the shadows at their candidate sites, and that played a role in their decision.”
Wright’s work, used for both artistry and research, is vital to improve our understanding of the Moon. There is an inescapable contrast between his cutting-edge methodology and the primordial nature of the 4.5 billion-year-old celestial body pictured. The Moon inspires tributes by those such as Claude Debussy and Ernie Wright, which in turn spark the imagination of those their works reach. | 0.836657 | 3.021477 |
When NASA thrusters are mentioned, most people imagine something like the breathtaking launch of the Saturn V rocket that sent astronauts to the Moon. Its five enormous F-1 engines generated more power than 85 Hoover Dams, and liftoff shook tiles off the ceiling of the observation room three miles away. But the agency that is currently topping that feat with its coming Space Launch System, planned to be the most powerful rocket ever built, is also now demonstrating the most delicate thrusters ever flown, so gentle they max out at a thrust equal to the weight of a fine grain of sand.
When engineer John Ziemer joined NASA’s Jet Propulsion Laboratory in 2000, one of his first projects was to survey possible thruster technology for a disturbance reduction system (DRS) that was to be NASA’s contribution to the European Space Agency’s (ESA) Laser Interferometer Space Antenna, or LISA, Pathfinder mission. The mission is to demonstrate technology that could one day enable measurements of gravitational waves in space.
“This could be a whole new way to look at the universe,” Ziemer says. “You could see supermassive black holes coalescing at the center of galaxies or look back to the early universe.”
The existence of gravity waves is predicted by the theory of relativity, but they’ve never been measured, mainly because they’re barely perceptible—so slight, in fact, that the job of the DRS is to counteract outside influences as negligible as the force of photons from the sun striking the craft’s shell. Given LISA’s surface area, this would be about equivalent to the push of a mosquito landing, Ziemer explains. “A gravity wave would be swamped by that disturbance.”
The DRS would also have to be unusually long-lived. Normally, thrusters are used only occasionally and briefly to put a spacecraft in place or change trajectory. But because the DRS must allow the craft to perfectly follow the test mass floating at its center, it has to be running whenever testing is being performed. Accordingly, the mission requires thrusters with a life of up to 3,000 hours.
NASA’s contribution to LISA Pathfinder was funded as Space Technology 7 (ST7) under the Agency’s New Millennium Program, which works to put the latest technology to the test in space.
During the buildup to the project, Busek, a company specializing in spacecraft propulsion and located in Natick, Massachusetts, was working on developing thrusters for use on nanosatellites under a Small Business Innovation Research (SBIR) contract it had won from Glenn Research Center two years earlier. As ST7 got underway and Ziemer became the project’s cognizant engineer for thrusters, Busek was one of two companies selected to compete for the contract to supply the subtlest thrusters ever flown: a technology called electrospray.
“There really isn’t anything that can compete with electrospray, in terms of thrust efficiency,” says Nate Demmons, director of Busek’s Electrospray Group. It works by applying an electrostatic field to the surface of an ionized, conductive liquid such as a molten salt, he explains. The charge distorts the surface into what’s known as a Taylor cone. At a certain voltage threshold, the electrostatic field overcomes the liquid’s surface tension, and a fine spray is ejected from the tip of the cone. These tiny droplets are then electrostatically accelerated to increase the thruster’s power.
Having a negligible vapor pressure, Demmons explains, ionic liquids don’t evaporate in the vacuum of space, as most fluids would. It was the discovery of these liquids in the 1990s, which have the right surface tension, viscosity, and conductivity, that led to a “Renaissance in electrospray,” he says.
The force of the spray, however, still is not easy to control, Ziemer says, noting the ESA worked for about a decade to master electrospray for the LISA project before ultimately switching to a precision cold-gas thruster system to meet budget and schedule constraints.
Busek refined its control of the thrusters’ delicate touch by developing a piezoelectric valve that manages the propellant flow rate. The behavior of such a thruster is difficult to observe or characterize, as the droplets it produces may be smaller than a wavelength of visible light, making them literally invisible. “Regardless, if you can control the voltage and current very closely, you can control the thrust,” says Ziemer, adding that the energy output can then be predicted down to the number of atoms that will be accelerated.
“Busek showed that, with the extra valve, they could not only meet the long-life requirement but also meet the thrust requirements,” he continues.
Busek was selected to supply two clusters of four thrusters each for the ST7-DRS project, which the company delivered in 2008. The craft was finally launched in 2015, marking the first time electrospray thrusters were flown in space.
“In 2008, we did not stop our research,” Demmons says. “LISA was mission-specific work, but electrosprays have other benefits we wanted to take advantage of.”
The thrusters the company had developed under the contract were capable of thrusts of up to just 30 micronewtons—about equivalent to the weight of the aforementioned mosquito. Busek has since scaled up the technology and returned to the original intent of its work with Glenn—providing propulsion for nanosatellites, such as the increasingly popular CubeSats. These inexpensive little satellites are now used by Government agencies, companies, universities, and hobbyists for purposes like Earth imaging or carrying out experiments in space. There are, however, virtually no options for on-board propulsion that meet the tight volume constraints of these tiny spacecraft, leaving them unable to change orbit or control how quickly their orbits decay.
Busek has successfully produced 100-micronewton and 1-millinewton electrospray thrusters for use on CubeSats, as it works its way up to a 20-millinewton booster that would be required to alter a small satellite’s orbit. This is about the force generated by other electronic propulsion systems at their lowest power.
More traditional ion thrusters operate at about 50 to 60 percent efficiency, meaning only a little more than half the power used to run them is converted to thrust, due to the energy spent generating, containing, and managing the ionized plasma that propels them. Meanwhile, the electrospray system Busek built for the LISA Pathfinder operates at about 70 percent efficiency.
There are also other applications for aspects of the technology. For example, Busek has sold the carbon nanotube electrostatic field emitters it designed for the electrospray thrusters to universities for uses such as electron microscopy. The firm is actively exploring applications within the semi-conductor manufacturing field as well.
The company is most interested in opportunities to get its CubeSat electrospray thrusters into space. Although no units have yet flown, a government or commercial client willing to take on some risk could partner with Busek to make it happen.
There are several other options for satellite manufacturers, however. Busek has developed and now offers several thrusters, including Hall effect thrusters, micro- pulsed plasma thrusters, radio-frequency ion thrusters, and green monopropellant thrusters—most of which were developed with at least some NASA funding.
“Busek is an expert satellite propulsion house with a stable of technology options,” says Vlad Hruby, president of Busek. “After a lot of development work, a number of our thrusters are on the cusp of commercialization, whereas others have already been proven in space.”
None, however, enable the extreme micro-precision Busek developed during the LISA Pathfinder mission—a mission expected to open up a new way to observe the universe, from unveiling mysteries in the planet’s crust and ocean currents to spotting events billions of light- years away. | 0.842825 | 3.651568 |
Another day, another video!
This time I am posting a video of the binary L5 Trojan Asteroid (617) Patroclus-Menoetius. In collaboration, with the team at the California Academy of Sciences, we have created a model of this interesting binary asteroid system which shares its orbit with Jupiter.
In 2001, a group of astronomer discovered that the L5 Trojan asteroid (617) Patroclus is in fact made of two components. In 2006, using Laser Guide Star Adaptive Optics System at W.M. Keck Observatory, we showed that those two components orbit around the center of mass of the system in ~4 days at 680 km describing a circular orbit. We named the second component Menoetius, the argonaut father of Patroclus in the greek mythology.
From the estimate of the size (derived from various techniques including Spitzer observations of mutual events taken in 2010 and stellar occultation on October 2013), we found out that the components are less dense than icy water, with a grain density very close to satellites of giant planets (like Amalthea, moon of Jupiter).
Because Patroclus has a different color and density than (624) Hektor, we speculated that it could be a captured Jupiter-Saturn asteroid which ended up in the gravitational well of the Sun-Jupiter system during the migration of the giant planets 3.7 Billion years ago. Its binary nature could be the result of tidal disruption when primitive asteroid had a close encounter with Jupiter before the capture.
Ultimately, we will need to send a spacecraft there to really understand this system. NASA has pre-selected the LUCY new discovery mission which could flyby this binary Trojan asteroid in 2033. | 0.843585 | 3.353564 |
A new study by Chinese and Australian astronomers has developed the world’s first accurate three-dimensional picture of the Milky Way’s warped appearance, showing that the galaxy’s disc is not flat but warped and twisted far away from the center.
The study was published online in the journal Nature Astronomy on Tuesday.
Many people believed the galaxy would look like a flat disc of stars that orbit around its central region, but researchers of the study found that the galaxy’s far outer regions are warped and twisted, forming a three-dimensional structure.
Chen Xiaodian, lead author of the study and a researcher at the National Astronomical Observatories of Chinese Academy of Sciences, said that accurate distances from the Sun to parts of the Milky Way’s outer disc were key to knowing what that disc actually looked like.
Researchers established a robust Galactic disc model based on 1,339 variable stars which are four to 20 times larger than the Sun, and up to 100,000 times more luminous. These stars providing high distance accuracy were used as primary distance indicators to develop an intuitive and accurate three-dimensional picture of the galaxy.
From the 3D distribution map, researchers found that the new derived stellar disc is warped in a progressively twisted spiral pattern, with an S-shape.
Further study validated that the stellar warp morphology is in excellent agreement with that of the galaxy’s warp.
“This new finding may help us to know the shape of the Milky Way, and provide a key clue to understanding how galaxies such as the Milky Way form and evolve,” said Deng Licai, co-author of the study. | 0.814138 | 3.360747 |
The Perseid meteor shower is one of the biggest spectacles of the year and even if you’re not into astronomy you have probably heard something about it. However, once I started digging in a little further the story got a little more interesting…
Quick facts about the Perseids Meteor Shower:
- Comet of Origin: 109P/Swift-Tuttle
- Meteor Shower period: July 17 to August 24th
- Meteor shower Peaks: Aug. 12-13
- Peak Activity Meteor Count: Up to 100 meteors per hour
- Look North / North-East late at night (after 10 p.m EST)
- Comet Swift-Tuttle has the mass of about 7 cars
- Comet takes 133 years to orbit the sun
- Travelling roughly at 58 km/s or 36 mi/s
- Will make closest approach in the year 2126 and 4479
- If it impacted Earth it would be 27 times more powerful than the asteroid that took out the dinosaurs
So without further adieu let’s talk about what Perseid meteor shower is, where it originated from, and the extensive history behind it.
Where Did Perseid Meteor Shower Come From?
A common question that gets asked all the time. Nonetheless, a good question. The Perseid Meteor shower is actually debris and pieces falling off comet Swift-Tuttle passing by at 58 km/s or 36 mi/s. I find that unbelievable in its own right as we get this beautiful display of meteorites burning up in the mesosphere, which is only 80 km or 49 miles above our fragile heads.
Even still where did this comet come from? Well, comets are what we call “dirty snowballs.” They are comprised mostly of gas, ice, and rock. Comet Swift-Tuttle is actually a periodic comet that takes 133 years to orbit the Sun. It has an orbital resonance of 1:11 with Jupiter. In plain English, that means the time it takes Jupiter to orbit our Sun 11 times (12 Earth years per orbit) comet Swift-Tuttle will have orbited the Sun just once.
The Great Discovery of Comet Swift-Tuttle
In 1862 the comet was discovered by Lewis Swift on July 16 and then a few days later by Horace Parnell Tuttle on July 19th. Astronomers believe there was a connection between this comet and the meteor showers that happened every August. It was later confirmed in 1992 when a Japanese astronomer spotted this comet with his 6-inch binoculars as the comet passed 177 million km or about 100 million miles away from Earth.
The intriguing part to me is how bright the comet look at various times in history. The apparent magnitude of the comet, or how bright it looks in the sky relative to other objects, in 69 B.C.E was 0.1 mag. To give you a frame of reference if you look at Vega in the night sky it is considered a magnitude of 0.03. Basically, the comet was as bright as an airplane in the sky and very easy to see with the naked eye.
In the year 2126, the comet will make its next closest approach and have an apparent magnitude of 0.7.
The Potential Threat of Comet Swift-Tuttle
For a moment in time, the Swift-Tutle was regarded as a highly possible threat to the Earth. This was something I never knew about personally but creates quite the context of the Perseid Meteor shower.
Swift-tutle is the largest Solar System object that makes repeated closes approaches to Earth. Not only that, but that orbit is drawing nearer and nearer to the Earth-Moon system. It’s usually okay when we can predict the orbits with precise measurement. However, the commotion started when it was sighted in 1992, and it was off by 17 days (July 11th vs. July 26th). When you look at the predictions and how far they are in astronomical units (AU), you can see how much closer swift-tutle is getting to Earth.
The good news is that it doesn’t look that bad after all.
- August 5th, 2126 will pass by 0.153 AU (22,900,000 km; 14,200,000 mi)
- August 24th, 2261 will pass by 0.147 AU (22,000,000 km; 13,700,000 mi) or 900,000 km closer.
By the way, if this comet hit Earth it would be at least 27 times harder than the asteroid that took out the dinosaurs. Check out the image below. It would be about 27x bigger than this impact!
Nevertheless, we’re not quite in the clear. 2000 years later in 4479, the comet will pass within 0.03 AU of Earth or about 4 million km or 2.4 million miles. There always be a little worry in the back of your head knowing we’ve been off predictions once before. It’s almost a 0% chance of hitting Earth in 4479 but of course, but 2000 years is a long time for trajectories to change as well as refining the predictions.
Even though Perseid Meteor shower is one of the most spectacular events of the year, it’s also a reminder to ask “hey, how’s that space program going?”
Sources used for this article:
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Sources/First red source in Canis Major
The first red source in Canis Major is unknown.
This is a lesson in map reading, coordinate matching, and researching. It is also a research project in the history of red astronomy looking for the first astronomical red source discovered in the constellation of Canis Major.
Nearly all the background you need to participate and learn by doing you've probably already been introduced to at a secondary level.
Some of the material and information is at the college or university level, and as you progress in finding red sources, you'll run into concepts and experimental tests that are actual research.
To succeed in finding a red source in Canis Major is the first step.
Next, you'll need to determine the time stamp of its discovery and compare it with any that have already been found. Over the history of red astronomy a number of sources have been found, many as point sources in the night sky. These points are located on the celestial sphere using coordinate systems. Familiarity with these coordinate systems is not a prerequisite. Here the challenge is geometrical, astrophysical, and historical.
A control group for this experiment may be a red source observed by ancient hominins in their version of the constellation Canis Major.
"Most of the sources are resolved in [Hubble Space Telescope] HST F814W imaging so they are certainly galaxies and not M stars."
The "earliest known astronomy anywhere in the world [is] that of the Australian Aborigines, whose culture has existed for some 40,000 years".
"The Aranda tribes of Central Australia, for example, distinguish red stars from white, blue and yellow stars."
Around 150 AD, the Hellenistic astronomer Claudius Ptolemy described Sirius as reddish, along with five other stars, Betelgeuse, Antares, Aldebaran, Arcturus and Pollux, all of which are clearly of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker, who prepared a paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credence to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas Jefferson Jackson See resurrected discussion on red Sirius with the publication of several papers in 1892, and a final summary in 1926. He cited not only Ptolemy but also the poet Aratus, the orator Cicero, and general Germanicus as colouring the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus' poem Phaenomena. [Seneca the Younger] Seneca, too, had described Sirius as being of a deeper red colour than Mars. However, not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius described it as "sea-blue", as did the 4th century Avienus. It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue.
In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th century Lombardic manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours. The Latin text taught readers how to determine the times of nighttime prayers from positions of the stars, and Sirius is described within as rubeola — "reddish". The authors proposed this was further evidence Sirius B had been a red giant at the time.
To introduce yourself to some aspects of the challenge may I suggest reading the highlighted links mentioned above, and if you're curious, those listed under the section "See also" below.
The Wikipedia article about the constellation Canis Major contains a high school level description. The figure at right shows the sky map of Canis Major. Around the edges of the map are coordinates related to longitude and latitude, but with the Earth rotating on its axis every 24 hours the celestial coordinates must remain fixed. How has this been accomplished?
Also, in the Wikipedia article is a list of stars in Canis Major. What's the difference between a star and an astronomical red source?
From the Wikipedia article on the Zodiac, is Canis Major a zodiacal constellation?
Canis Major is one of the 88 modern constellations, and was included in the 2nd-century astronomer Ptolemy's 48 constellations. Canis Major is a constellation in the southern hemisphere's summer (or northern hemisphere's winter) sky. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'CMa'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 4 sides. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 06h 12.5m and 07h 27.5m, while the declination coordinates are between -11.03° and −33.25°. Covering 380 square degrees, it ranks 43rd of the 88 constellations in size.
Star classification by colorEdit
|Conventional color||Apparent color||Mass
(solar masses, Mʘ)
(solar radii, Rʘ)
|Fraction of all|
main sequence stars
|O||≥ 33,000 K||blue||blue||≥ 16||≥ 6.6||≥ 30,000||Weak||~0.00003%|
|B||10,000–33,000 K||blue to blue white||blue white||2.1–16||1.8–6.6||25–30,000||Medium||0.13%|
|A||7,500–10,000 K||white||white to blue white||1.4–2.1||1.4–1.8||5–25||Strong||0.6%|
|F||6,000–7,500 K||yellowish white||white||1.04–1.4||1.15–1.4||1.5–5||Medium||3%|
|G||5,200–6,000 K||yellow||yellowish white||0.8–1.04||0.96–1.15||0.6–1.5||Weak||7.6%|
|K||3,700–5,200 K||orange||yellow orange||0.45–0.8||0.7–0.96||0.08–0.6||Very weak||12.1%|
|M||≤ 3,700 K||red||orange red||≤ 0.45||≤ 0.7||≤ 0.08||Very weak||76.45%.|
Testing a sourceEdit
There are many web sites that may have a red source listed for the constellation Canis Major.
A. Constellation article
Under "Notable features" in the Wikipedia article on the constellation Canis Major is the list of stars in Canis Major. Click on this link. In the table of this Wikipedia article is α CMa. To the right are coordinates:
- [Right ascension] (RA): 05h 45m 08.9173s and
- [Declination] (Dec): -16° 42' 58.017".
Find these coordinates on the Canis Major map at the right. Is alpha Canis Major really inside the boundaries of the constellation?
To evaluate the star as a red source, skip ahead to the section "Red source".
B. Wikipedia search
Another way to look for red sources in the constellation is to perform a search on Wikipedia. Try ""Canis Major" red" without the outside quotes. This yields 61 possible astronomical red source candidates.
To evaluate a red source, skip ahead to section "Red source".
Another way to find possible red sources in Canis Major is to use search queries on SIMBAD.
Click on the SIMBAD link under "External links" below, then click on "Criteria query" or "by criteria".
In the tan box, type in "region(05 45 08.9173 -16 42 58.017, 10m)", without the quotes. This tells the SIMBAD computer you are interested in a circular region of the celestial sphere centered on the coordinates for alpha Canis Majoris, with a radius of 10 arcminutes (m).
Notice on the page over at the right from the tan colored box: "Return". The default is "object count". Click on "submit query". In a few moments a result something like "Number of objects: 9" should appear. Click "Back" to see the tan box again.
To see if you have found at least one object, change "Return" to "display" by clicking on the circle to its left, then "submit query".
SIMBAD should display a list of objects. Read through the resource red astronomy for clues that may indicate whether a particular spectral type (Sp type) is a red source. If none of the objects listed seems to be described as a red source, try going "Back" and increasing the arcminutes from "10m" to "20m", and repeat until a red source is found.
Once you believe you have discovered a red source, proceed to the section "Red source".
There are several ways to evaluate a red source for the constellation Canis Major.
Stellar classification places the range of effective surface temperatures for the class K stars as 3,700 - 5,200 K.
* Not a standard star.
|K2V||Epsilon Eridani||74%||34%||5,084 ± 5.9||4,867|
|K5V||61 Cygni A||67%||15%||4,526 ± 66||4,367|
|K7V||61 Cygni B||60%||8.5%||4,077 ± 59||4,033|
Some of the effective temperatures for the K standard stars are fairly recent.
The Planckian radiator peak wavelength for any effective surface temperature in K may be found using your handheld calculator with the formula:
Depending on the internal software, ask it to print or display y. Iteratively enter different temperatures (e.g. 6060 in the equation) and wavelengths (e.g. 495 nm as 0.0000495 in the equation) to see how close to zero you are.
For the temperature, wavelength pair (6060 K,495 nm), the value is -3.419065E-03. This is close in the third digit.
The spectral type K stars have their peak wavelength in the red band from approximately K3V through K9V. Why would they appear orange to us?
The temperature, wavelength pair (3800 K,690 nm) gives an equation of
- y=(1.48833/(0.0000690*3800))*exp(1.48833/(0.0000690*3800))/(exp(1.48833/(0.0000690*3800))-1)-5, with a value of 0.695831, which is not as close, and suggests an error in the first digit.
When the temperature is higher than the minimum for a specific wavelength, the value of the equation is negative. When the wavelength is shorter than the minimum for a specific temperature, the value of the equation is positive.
As the Planckian radiator peak wavelength is in the infrared instead of the red, why are these M-class main sequence stars called red dwarfs rather than infrared dwarfs?
Click on the link to the Wikipedia article. After you've enjoyed reading about the source, use the 'find' command of your browser to see if this Wikipedia page mentions anything about "red" or "red rays". Does the article mention whether or not the source is a red source?
What is the current time stamp for the Wikipedia article on the source? [Hint]: look for something like "This page was last modified on 12 January 2012 at 06:47." very near the bottom of the page. For now this is an adequate time stamp.
From reading the Wikipedia article on the source, if you believe the text demonstrates that the source is not a red source in Canis Major edit the "Non-red source in Canis Major" section near the bottom of the page with an entry similar to "# Alpha Canis Majoris 12 January 2012 at 06:47 Wikipedia article "Alpha Canis Majoris".", without the outer quotes, and finish the entry with four "~"s without the quotes after the period. The date included with your designation or username is a time stamp for the entry. The last portion of the entry is the source of your information.
On the other hand, if there are one or more sentences in the article that you believe demonstrates that the source is a red source in Canis Major edit the section below "Red source in Canis Major" with a similar entry.
Go to the section entitle, "Challenging an entry".
To check any source (even one from Wikipedia) on SIMBAD, click of the "External link" to the "SIMBAD Astronomical Database".
At the lower right side of the SIMBAD Astronomical Database page is a "Basic search" box. There are several ways to try your target:
- source name: without the quotes or
- source coordinates: without the quotes, for example, "05 45 08.9173 -16 42 58.017".
If you are looking at a SIMBAD generated table which lists possible targets, click on one.
On its SIMBAD page move over to the right side until you see an Aladin visual photograph of the object. Is it a red source?
Even if the source does not look red, look down the left hand side of the page for "Spectral type:". From your reading of red astronomy, do you believe the source is a red source, or not? Noting that SIMBAD does, or does not consider the source to be a red source is important, so skip down to the "SIMBAD time stamp" section.
If you have already found a red source (or a table of them) using SIMBAD, click on the blue link identifier for the first.
SIMBAD time stampEdit
Peruse the SIMBAD page for a time stamp or date of last revision. [Hint: it may look something like "2012.01.09CET20:10:02" and be in the upper right.]
If the entry at SIMBAD convinces you that the source is not a red source, edit the "Non-red source in Canis Major" section near the bottom of this page and type in an entry similar to "# Source Name 2012.01.09CET20:10:02 SIMBAD article "SIMBAD source name".", without the first set of quotes, followed by four ~s.
If your SIMBAD analysis convinces you that you have found a red source in Canis Major (did you check the coordinates vs. the map of Canis Major?), make an entry something like the ones in the section "Red source in Canis Major".
Challenging an entryEdit
Any entry in either the section "Red source in Canis Major" or "Non-red source in Canis Major" can be challenged. The time stamp may be challenged to see if there is an earlier one. The source may be challenged by an earlier source.
Is Wikipedia a 'primary source', or does the Wikipedia article cite a source?
Even though Wikipedia has an article on the source, is it a good place to stop in testing whether the source has been detected as an astronomical red source?
If the Wikipedia article cites a primary source, skip down to the section on "Primary sources".
Is SIMBAD a 'primary source'?
SIMBAD is an astronomical database provided by the Centre de Données astronomiques de Strasbourg. It is an authoritative source, but they do occasionally make a mistake.
If you find a red source within the constellation on SIMBAD, the next step is to find the earliest time stamp of discovery.
Primary sources may be searched for possible additional information perhaps not yet evaluated by SIMBAD or not presented in a Wikipedia article about a source.
Wikipedia test sourceEdit
For a Wikipedia article that cites a primary source, scroll down to the reference and open the reference. Read through the article looking for where the source mentioned in the Wikipedia article occurs. Some primary source authors may use source designations that are not mentioned in the Wikipedia article. To look for other designations, click on the link to SIMBAD in the "External links" on this page, enter the source name from the Wikipedia article, and see if other names are mentioned in the article.
When none of the names are mentioned, click on the link for "Google Advanced Search" in the list of "External links", enter the source name or designation(s) such as "Gliese 866", with "red" to see if the source has a reference indicating it is a red source. And, look for the earliest one. Compose an entry using the primary source.
SIMBAD test sourceEdit
Further down the SIMBAD page is a list of "Identifiers". Click on the blue bold portion.
On the page that appears, there should be a primary source listed after Ref:. Click on the blue link with the oldest year. This yields an earlier time stamp and entry citation like the current one in the section "Red source in Canis Major". If you find another source or an earlier time stamp, compose a similar entry and edit the section. Additional information to add into the reference can be found by clicking on "ADS services" from the SIMBAD page.
Changing an entryEdit
From your analysis of the source so far, is it a red source?
If you have found an earlier time stamp for the source than the one listed in the section below "Non-red source in Canis Major" and the answer to the above question is "no", you can edit the section with your result. Or, you can leave the entries as is and try another star or object.
If you have found an earlier time stamp for the source than the one listed in the section below "Red source in Canis Major", edit the section with your result. Or, if you found another red source with a comparable or earlier time stamp, edit the section with your result.
Red sources in Canis MajorEdit
Non-red sources in Canis MajorEdit
Around 150 AD, the Greek astronomer of the Roman period Claudius Ptolemy described Sirius as reddish.
- The first red source in Canis Major was probably observed around 42,000 b2k.
- Michael C. Liu, Arjun Dey, James R. Graham, Charles C. Steidel and Kurt Adelberger (1999). Andrew J. Bunker and Wil J. M. van Breugel (ed.). Extremely Red Galaxies in the Field of QSO 1213-0017: A Galaxy Concentration at z = 1.31, In: The Hy-Redshift Universe: Galaxy Formation and Evolution at High Redshift. 193. Berkeley, California USA: American Society of Physics. pp. 344–7. Bibcode:1999ASPC..193..344L. ISBN 1-58381-019-6. Retrieved 2013-07-30.CS1 maint: multiple names: authors list (link)
- R Haynes (June 27, 1996). Raymond Haynes, Roslynn Haynes, David Malin & Richard McGee (ed.). Explorers of the southern sky: a history of Australian astronomy. The Pitt Building, Trumpington Stree, Cambridge CB2 1RP, England UK: Cambridge University Press. p. 527. ISBN 0521365759. Retrieved 2013-08-02.CS1 maint: multiple names: editors list (link) CS1 maint: location (link)
- J.B. Holberg (2007). Sirius: Brightest Diamond in the Night Sky. Chichester, UK: Praxis Publishing. ISBN 0-387-48941-X.
- R. C. Ceragioli (1995). "The Debate Concerning 'Red' Sirius". Journal for the History of Astronomy 26 (3): 187–226.
- Whittet, D. C. B. (1999). "A physical interpretation of the 'red Sirius' anomaly". Monthly Notices of the Royal Astronomical Society 310 (2): 355–359. doi:10.1046/j.1365-8711.1999.02975.x.
- 江晓原 (1992). "中国古籍中天狼星颜色之记载" (in Chinese). Ť文学报 33 (4).
- Jiang, Xiao-Yuan (April 1993). "The colour of Sirius as recorded in ancient Chinese texts". Chinese Astronomy and Astrophysics 17 (2): 223–8. doi:10.1016/0275-1062(93)90073-X.
- Schlosser, W.; Bergmann, W. (November 1985). "An early-medieval account on the red colour of Sirius and its astrophysical implications". Nature 318 (318): 45–6. doi:10.1038/318045a0.
- Russell, Henry Norris (1922). "The New International Symbols for the Constellations". Popular Astronomy 30: 469–71.
- "Canis Major, Constellation Boundary". The Constellations (International Astronomical Union). http://www.iau.org/public/constellations/#cma. Retrieved 15 November 2012.
- Tables VII, VIII, Empirical bolometric corrections for the main-sequence, G. M. H. J. Habets and J. R. W. Heinze, Astronomy and Astrophysics Supplement Series 46 (November 1981), pp. 193–237, bibcode=1981A&AS...46..193H. Luminosities are derived from Mbol figures, using Mbol(ʘ)=4.75.
- The Guinness book of astronomy facts & feats, Patrick Moore, 1992, 0-900424-76-1
- The Colour of Stars. Australia Telescope Outreach and Education. 2004-12-21. Retrieved 2007-09-26. — Explains the reason for the difference in color perception.
- What color are the stars?, Mitchell Charity. Accessed online March 19, 2008.
- Glenn LeDrew (February 2001). "The Real Starry Sky". Journal of the Royal Astronomical Society of Canada 95 (1 (whole No. 686, February 2001), pp. 32–33. Note: Table 2 has an error and so this article will use 824 as the assumed correct total of main-sequence stars). http://adsabs.harvard.edu/abs/2001JRASC..95...32L.
- S. Catalano, K. Biazzo, A. Frasca and E. Marilli (November 2002). "Measuring starspot temperature from line depth ratios". Astronomy & Astrophysics 394 (3): 1009-21. doi:10.1051/0004-6361:20021223. http://www.aanda.org/articles/aa/full/2002/42/aa2543/node1.html. Retrieved 2012-08-15.
- Lisa Kaltenegger, Wesley A. Traub (June 2009). "Transits of Earth-like Planets". The Astrophysical Journal 698 (1): 519-527. doi:10.1088/0004-637X/698/1/519.
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Developed to help scientists learn more about the complex nature of celestial objects in the universe, astronomical surveys have been cataloguing the night sky since the beginning of the 20th century. The intermediate Palomar Transient Factory (iPTF)—led by the California Institute of Technology (Caltech)—started searching the skies for certain types of stars and related phenomena in February.
Since its inception, iPTF has been extremely successful in the early discovery and rapid follow-up studies of transients—astronomical objects whose brightness changes over timescales ranging from hours to days—and two recent papers by iPTF astronomers describe first-time detections: one, the progenitor of a rare type of supernova in a nearby galaxy; the other, the afterglow of a gamma-ray burst in July.
The iPTF builds on the legacy of the Caltech-led Palomar Transient Factory (PTF), designed in 2008 to systematically chart the transient sky by using a robotic observing system mounted on the 48-inch Samuel Oschin Telescope on Palomar Mountain near San Diego, California. This state-of-the-art, robotic telescope scans the sky rapidly over a thousand square degrees each night to search for transients.
Supernovae—massive exploding stars at the end of their life span—make up one important type of transient. Since PTF’s commissioning four years ago, its scorecard stands at over 2,000 spectroscopically classified supernovae. The unique feature of iPTF is brand-new technology that is geared toward fully automated, rapid response and follow-up within hours of discovery of a new supernova.
The first paper, “Discovery, Progenitor and Early Evolution of a Stripped Envelope Supernova iPTF13bvn,” appears in the September 20 issue of Astrophysical Journal Letters and describes the detection of a so-called Type Ib supernova. Type Ib supernovae are rare explosions where the progenitor star lacks an outer layer of hydrogen, the most abundant element in the universe, hence the “stripped envelope” moniker. It has proven difficult to pin down which kinds of stars give rise to Type Ib supernovae. One of the most promising ideas, says graduate student and lead author Yi Cao, is that they originate from Wolf-Rayet stars. These objects are 10 times more massive and thousands of times brighter than the sun and have lost their hydrogen envelope by means of very strong stellar winds. Until recently, no solid evidence existed to support this theory. Cao and colleagues believe that a young supernova that they discovered, iPTF13bvn, occurred at a location formerly occupied by a likely Wolf-Rayet star.
Supernova iPTF13bvn was spotted on June 16, less than a day after the onset of its explosion. With the aid of the adaptive optics system used by the 10-meter Keck telescopes in Hawaii—which reduces the blurring effects of Earth’s atmosphere—the team obtained a high-resolution image of this supernova to determine its precise position. Then they compared the Keck image to a series of pictures of the same galaxy (NGC 5806) taken by the Hubble Space Telescope in 2005, and found one starlike source spatially coincident to the supernova. Its intrinsic brightness, color, and size—as well as its mass-loss history, inferred from supernova radio emissions—were characteristic of a Wolf-Rayet star.
“All evidence is consistent with the theoretical expectation that the progenitor of this Type Ib supernova is a Wolf-Rayet star,” says Cao. “Our next step is to check for the disappearance of this progenitor star after the supernova fades away. We expect that it will have been destroyed in the supernova explosion.”
Though Wolf-Rayet progenitors have long been predicted for Type Ib supernova, the new work represents the first time researchers have been able to fill the gap between theory and observation, according to study coauthor and Caltech alumna Mansi Kasliwal (PhD ’11). “This is a big step in our understanding of the evolution of massive stars and their relation to supernovae,” she says.
The second paper, “Discovery and Redshift of an Optical Afterglow in 71 degrees squared: iPTF13bxl and GRB 130702A,” appears in the October 20 issue of Astrophysical Journal Letters. Lead author Leo Singer, a Caltech grad student, describes finding and characterizing the afterglow of a long gamma-ray burst (GRB) as being similar to digging a needle out of a haystack.
Long GRBs, which are the brightest known electromagnetic events in the universe, are also connected with the deaths of rapidly spinning, massive stars. Although such GRBs initially are detected by their high-energy radiation—GRB 130702A, for example, was first located by NASA’s Fermi Gamma-ray Space Telescope—an X-ray or visible-light afterglow must also be found to narrow down a GRB’s position enough so that its location can be pinpointed to one particular galaxy and to determine if it is associated with a supernova.
After Fermi’s initial detection of GRB 130702A, iPTF was able to narrow down the GRB’s location by scanning an area of the sky over 360 times larger than the face of the moon and sifting through hundreds of images using sophisticated machine-learning software; it also revealed the visible-light counterpart of the burst, designated iPTF13bxl. This is the first time that a GRB’s position has been determined precisely using optical telescopes alone.
After making the initial correlation between the GRB and the afterglow, Singer and colleagues corroborated their results and gained additional information using a host of other instruments, including optical, X-ray, and radio telescopes. In addition, ground-based telescopes around the world monitored the afterglow for days as it faded away, and recorded the emergence of a supernova five days later.
According to Singer, GRB130702A / iPTF13bxl turned out to be special in many ways.
“First, by measuring its redshift, we learned that it was pretty nearby as far as GRBs go,” he says. “It was pretty wimpy compared to most GRBs, liberating only about a thousandth as much energy as the most energetic ones. But we did see it eventually turn into a supernova. Typically we only detect supernovae in connection with nearby, subluminous GRBs, so we can’t be certain that cosmologically distant GRBs are caused by the same kinds of explosions.”
“The first results from iPTF bode well for the discovery of many more supernovae in their infancy and many more afterglows from the Fermi satellite”, says Shrinivas Kulkarni, the John D. and Catherine T. MacArthur Professor of Astronomy and Planetary Science at Caltech and principal investigator for both the PTF and iPTF.
The iPTF project is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin, Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University System of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Universe in Japan. | 0.864129 | 4.066641 |
Dr. Edwin C. Krupp has spent more than 40 years researching how ancient cultures worshipped and studied the parade of celestial lights—the movement of the sun, moon, planets, and stars—to make sense of seasonal cycles on Earth. An “archaeoastronomer,” who studies the early history of astronomy, Krupp has written five books and visited more than 1,900 historic and prehistoric sites associated with the sky.
From the ancient Egyptians, who built monuments aligned with the annual rising of the bright star Sirius, to the New World’s Incas, who constructed temples positioned to track the sun, people have been guided by the heavens, telling stories about the sky that not only brought a sense of order to their lives but ultimately led to the development of modern astronomy, Krupp notes.
Since 1974, Krupp has been director of the Griffith Observatory in Los Angeles. In 2004, he oversaw the $93 million renovation of the iconic structure. Today, the 75-year-old observatory features two public telescopes, each mounted inside a copper-clad dome.
Despite the modern tools of astronomy, people still see portents in the sky. In 1982, the solar system’s planets grouped together loosely on one side of the sun, which some doomsday prognosticators claimed would trigger a catastrophic phenomenon known as the Jupiter Effect. Griffith Observatory took the lead in reassuring the public that the Jupiter Effect would not trigger a great California earthquake, as some soothsayers had predicted.
Always animated and ready with a story, Krupp spoke to Nautilus from his Observatory office.
How did astronomy develop?
We are pattern-seeking creatures who use patterns to anticipate the future, understand the past, and tell stories about ourselves to make sense of the world. I think it’s fair to say that the deep origins of astronomy are in that recognition of those patterns in the sky that are locked to the Earth. Many traditional cultures were acutely aware of the seasonal comings and goings of food and other resources and they linked those critical changes to the appearance and disappearance of certain stars or groupings of stars. When do the rivers flood? When do the salmon run? When do the bison rut? Those are the things that mattered, and people saw the connections between them and the sky.
Why is storytelling so important in the development of astronomy?
It’s a tool for survival. The Egyptians told tales of the battles that the sun might be enduring as it moves across the sky. Of course the sun isn’t going through battles; it’s the Earth rotating on its axis as it moves in orbit around the sun that causes the apparent, relative movement of the sun. But even if you tell the wrong story, it may persist for thousand of years if it brings order to the behavior of the world around you.
What’s the connection between astronomy and math?
The path between math and science can be traced all the way back to Mesopotamia. I don’t think that’s very far back, actually, only about 4,000 to 5,000 years. In terms of human experience on the planet, that’s not very much. But math has a power for people that is far more expansive than simply what’s happening in the sky and how things overhead work.
Because math was a way to order the universe?
Certainly it was. But if you’re looking for the roots of mathematics, it has to begin with, “I’ve got sheep, how many?” “I’ve got a family. Is anyone missing?” So counting, numeration, and manipulation of numbers have got to be very archaic skills. We have lots of economic records from ancient Mesopotamia, and it would be easy to argue that the real power of mathematics in ancient Mesopotamia was business.
How did ancient cultures perceive light from the heavens?
Because sources of light are indicative of power, celestial objects were assigned a divine character. They become gods whose behavior bears watching because they are either a power source that affects things on Earth or they signal what’s taking place on Earth.
It was a real time of threat for the weak and young and infirm. If the sun doesn’t turn back and do what it does every year, the cosmos is in trouble.
Was there a type of celestial light that was most important to people in the Stone Age?
We don’t have enough evidence to say it was the stars first or the moon or sun. But certainly the stars were one of the most fundamental and simple things. It can be anything from a single star to the distinctive Pleiades cluster, or maybe a grouping like the Southern Cross. They were using the stars not to map the sky but as landmarks for the seasonal march of time. A particular star appears in the morning sky when the caterpillars are behaving a certain way or when the fish are active: They contrive a picture of the world that links the behavior of the sky, particularly the stars, to things that matter on Earth. This may well be the first way in which people linked the sky to the earth and its resources.
What role did the sun play in ancient cultures?
People were making elementary observations of the sun—variations in its height during the course of the day, its location at its highest point, and changes where it rises and it sets. Even nomadic people had this connection with the sun. Narratives were created and modeled on what the sun was doing. In California, the Chumash Indians had the notion that everything was at risk when you hit winter. It was a real time of threat for the weak and young and infirm. The notion develops that if the sun doesn’t turn back and do what it does every year, the cosmos is in trouble. Every year there was a sense of cosmological crisis at winter solstice. People knew the sun was headed south, they knew how far it would normally go. So they would undertake ritual activity to influence the outcome of what seemed to be going on in the cosmos and translate it into stories and activities that made very specific sense to them in their culture.
And the role of the moon?
The moon is a more complicated creature in the sky, but it does do some things that are very obvious and simple and useful. It races through the sky compared to the others, and as it does so it changes dramatically. People get this picture of the moon going through its monthly transformation and equate that with the female fertility cycle because the lengths of time are about the same. They also count the number of full moons, because the passage of time through the seasons is what’s important. People weren’t even that interested in how many days there are in a year. It was, where are we in the progress of the stars, where are we in the progress of the sun, how many moons have gone by?
Studying the Inca tradition, you said you had a remarkable revelation about the Pleiades constellation. Can you tell us about it?
The Pleiades were among the luminous gods depicted inside a temple at the heart of the Incan empire. The alignment of the temple was on the rising direction of the Pleiades. To archaeoastronomers, this seems very puzzling. We’re used to lining up stuff on the sun. So what’s going on? The answer for a long time has been, well, the Pleiades were an important seasonal signal. People talk about how many of the stars they see, how bright they appear to be, whether they are sharp, whether they are fuzzy. They make prognostications about their strategies for the coming year. It’s an item of discussion and consensus that leads to a community decision that is a life and death matter.
But here’s the interesting thing. There’s a very good anthropological study that examines what the Incas were learning from the Pleiades. It turns out what they were observing each year was the varying climatic conditions produced by the presence or absence of an El Niño, which creates high altitude cirrus clouds. These cirrus clouds are fundamentally invisible, but they do alter the appearance of things like stars in the sky, and the Pleiades are a very subtle thing to observe. Satellite data have demonstrated that the Incas were correctly observing what El Niño is doing from year to year! They’re making appropriate decisions based on average temperatures and rainfall! The fact the Pleiades were prominent to the Incas at the time of the conquest suggests they have been doing this for at least 500 years. They are still doing it in villages in Peru.
Did astronomy have a role beyond agriculture?
Yes, early studies of the sky provided stability and structure to social and political organizations. A perfect example of this is the emperor in ancient China, who was regarded as the primary intermediary between Earth and the divine force in heaven. The emperor is sacred, and that stabilized and protected the way that the Chinese culture allowed itself to be governed.
He performed alchemy, he was an astronomer who got royal support. His extraordinary achievements epitomized pre-telescopic astronomy.
Who are the founders of astronomy?
If we’re talking about ancient Greek and Mediterranean astronomy, Ptolemy epitomized that whole initiative in the second century. He consolidated the astronomical knowledge of his time, developed new and detailed methods of geometric calculation of celestial objects, and refined methods of pinpointing and predicting the position of the sun, moon, and planets. Another key character is the Greek astronomer Hipparchus from the second century B.C. He created a brightness scale for the stars, something we now take for granted. He systematically identified the location and brightness of stars just as they were beginning to be used to map the sky rather than just representing seasonal landmarks. We also credit Hipparchus as the first to recognize the phenomenon of prerecession, which is the wobbling of the Earth on its axis every 26,000 years. It may not seem very significant and it doesn’t affect everyday life. But back in antiquity when people knew that the sky seemed to turn daily, and there were objects that moved at other rates, and yet here was one more subtle movement of the sky. It was an extraordinary discovery.
In your book, Echoes of the Ancient Skies, you write that “our Greek ancestors invented scientific cosmology and by grappling with space, time, and the heavenly spheres they set us on the course that has lifted us off the Earth and carried us to worlds beyond our own.” So the Greeks’ knowledge was handed down to cultures centuries later?
Yes. The mechanism by which this occurred is at least partially understood thanks to the incredibly important Islamic transmission. You have these astonishing texts on astronomy in the Islamic world that wind up getting carried along the Silk Road and then into Spain, where you have a political climate that welcomes scientific and mathematical inspiration. Following the Islamic traditions, the astronomer Ulugh Beg in 1420 built an observatory in Samarkand [Uzbekistan]. One of the most important instruments at his observatory was a large arch, used to calculate midday. He used a meridian arc, among other instruments, to make the first star atlas, catalogue, and charts since Ptolemy.
When did the goals of astronomy begin to change?
Throughout the Middle Ages in Europe, the focus was on perfecting the calendar. You needed to know where you were in the year, and so you would put out a calendar that was based on the seasonal behavior of the sun and the cycles of the moon. The date of Easter was a profound driver in that the church operated as a main template for important dates of the year. Another driver is the Age of Exploration, which emerged in the 14th and 15th centuries. Once people were navigating great distances at sea, there was a greater urgency for a reliable instrument to orient you and provide your location. That problem didn’t get solved until the development of the mechanical clock, long after the beginning of the Age of Exploration. But all through that time people were trying. With the invention of the telescope in 1609, Galileo discovered the moons of Jupiter. People started wondering if they could use some of the new discoveries about the sky to keep track of the time.
Does one person stand out from the rest in carrying astronomy into the modern age?
It’s got to be Tycho Brahe [1546-1601], who became a scientist of all trades. He performed alchemy, he was an astronomer who got royal support—he was given an entire island where he built not one, but two observatories. His extraordinary achievements epitomized pre-telescopic astronomy. His observations shattered the preconceived notions about the character of the heavens. He discovered a “new star”—a supernova—in the sky when no new stars should be seen. He showed that comets were above Earth’s atmosphere, where bodies were thought to be immutable. These discoveries genuinely altered the perception of the nature of the cosmos. Then Kepler inherited, or rather, purloined, all these observations from Tycho and from those, Kepler managed to see that uniform circular motion of the planets, first promulgated by Ptolemy and the ancients Greeks, is not really what the game is.
What lessons can we learn from ancient astronomy?
The examination of antiquity creates a sense of how we got here and the values that enriched people’s lives and can enrich our own. If people are charmed by the sunrise, notice the phases of the moon, or have a chance to see the Northern Lights, those things enrich their emotional sensibility about themselves and the world. That to me is like art and music—the things we do to be grateful for the richness of being alive.
Ron Cowen is a freelance science writer in Silver Spring, Md., who specializes in astronomy and physics. | 0.81695 | 3.319464 |
10 Out-Of-This-World Facts About Jupiter’s Moon Europa
Jupiter’s moon Europa is a cold, icy, and bright oddity in our solar system. Europa, roughly the size of Earth’s own Moon, is the smallest of Jupiter’s four Galilean moons, which can easily be seen with even the smallest of telescopes here on Earth. It is the second-closest of the Galilean moons to Jupiter after Io, which means it is bombarded with immense radiation from its massive parent planet. Europa is estimated to be 4.5 billion years old and is about 780 million kilometers (485 million mi) from the Sun. Europa orbits Jupiter every three and a half days at an average distance of about 671,000 kilometers (417,000 mi) and is tidally locked, meaning the same side of the moon always faces the gas giant. Europa is 3,100 kilometers (1,900 mi) in diameter, larger than Pluto, making it the 15th-largest body in the solar system.
Since Europa is rich with water ice, many scientists propose that it could host life, despite being incredibly cold. Also interesting is that Europa has a magnetic field, which means that something underneath its surface is conductive. Europa has long been an object of scientific curiosity for researchers on Earth. The Voyager and Galileo spacecrafts each sent back detailed images of the moon’s strange surface, and future NASA missions to study Europa are planned. In this list, we review ten amazing facts regarding this weird and out-of-this-world moon!
10 Europa And Earth’s History
Using a very low-powered telescope during the 17th century, Galileo likely had trouble distinguishing between the four moons he spotted as faint points of light near Jupiter. However, while Galileo’s discovery of four new heavenly bodies is, in itself, amazing, given the era and the early technology he was using, his findings were to have a profound influence on European history for centuries to come. The discovery of Europa, along with the other three Galilean moons, proved that our Earth was not the center of the universe, thus proving that everything in the night sky did not, in fact, orbit our planet.
9 Europa’s Name
In Greek mythology, Europa is the name of a young woman who was the daughter of a king. Europa was one of Zeus’s lovers and was made the queen of the island of Crete by Zeus. Europa, in true mythological fashion, was abducted by Zeus, who took the form of a white bull. After adorning the bull with flowers, Europa rode it to the island of Crete, where Zeus—the counterpart to the Roman god Jupiter—revealed his true form and seduced Europa with his power.
For centuries, the idea of giving mythological names to the Galiean moons was unpopular. (Europa has also been referred to as “Jupiter II.”) By the 20th century, however, scientists were calling the moons Europa, Io, Ganymede, and Callisto.
8 Cracks And Mounds
Europa’s icy surface is generally smooth, indicating that water from beneath the frigid moon’s surface seeps upward and freezes. However, there are craggy dark and bright streaks as well as a handful of craters on the surface. Pwyll, the largest crater on Europa, is one of the most obvious features on the Jovian moon. It was first observed by NASA’s Voyager probe. Pwyll is estimated to be around 18 million years old and is 25 kilometers (16 mi) across!
Other features, called lineae, are Europa’s most brilliant characteristics. Thousands of dark, streaking lineae, or “lines,” cross each other throughout Europa’s entire surface. These “lines” are deep cracks in the ice. Scientific research has shown that the icy crust on both sides of the lineae are spreading away from each other. Amazingly, some of the larger of Europa’s lineae have been shown to be 20 kilometers (12 mi) across. Scientists hypothesize that the lineae are produced by waves of eruptions of warmer ice as Europa’s crust spreads, opens, and exposes the warmer layers of ice below. The cause of the warmer bulges of ice below is thought to come from the immense radiation emitted by Jupiter itself.
Other weird features of Europa’s surface include circular freckles referred to as lenticulae. These freckles are dome-like features, whereas others are pit-like, giving images from NASA spacescraft a mottled and rough landscape. The tops of these lenticulae are similar in texture to the surfaces below them, perhaps suggesting that the dome-like features were pushed up somehow. One hypothesis about the freckled landscape argues that these lenticulae were also formed by warm ice rising up through the colder ice of the outer crust, similar to magma rising below Earth’s surface. Yet another strange feature of Europa is its very high reflectivity. Its icy surface makes it one of the most reflective, or shiny, objects in the solar system!
7 A Lot Of Ice
Like Earth, Europa is thought to have an iron core with a rocky mantle above and a layer of salty water. However, as mentioned, above that water, a massive layer of ice sits on the moon’s surface, giving Europa its high reflectivity. Amazingly, scientists hypothesize that Europa’s surface layer of ice could be as old as 180 million years. That is some old ice!
Aiding scientists here on Earth are the images received from NASA’s Galileo spacecraft, which provided data suggesting that Europa’s icy surface layer can be up to 100 kilometers (62 mi) thick. The Galileo spacecraft made numerous flybys of Europa and also revealed strange landscapes of large pits connected to domes. What these landscapes suggest is that on Europa, the miles-thick ice surface seems to be turning over in large areas. Some scientists think the icy surface is convecting in part from heat from Europa’s much warmer core.
6 Chaos Regions
The Galileo spacecraft also discovered strange broken slabs of polygonal ice sheets that were often covered in a reddish material. Scientists chose to call these areas “chaos terrain,” as it is still being debated as to why these landscapes resemble huge puzzle pieces.
As if these kinds of icy landscapes were not strange and inhospitable enough, in 2011, scientists studying Galileo images suggested that these types of chaos terrain areas were places where the surface collapsed into subsurface lakes, some of which hold more water than the volume of North America’s Great Lakes only a couple of miles below the icy surface!
5 It’s Pretty Cold
While some people might vacation on Europe’s warm, breezy, and comfortable Mediterranean coast, Jupiter’s moon Europa offers a slightly colder alternative. Europa’s bleak and icy landscape might look scary, but its temperatures are beyond frigid.
4 Subsurface Ocean
On Europa, the incredible radiation as well as the tidal forces of Jupiter’s gravity aid in heating the moon’s interior. This heating melts the ice and is believed to have produced an incredible subsurface salty ocean. This ocean theory stems from the belief that the existence of “floating” continent-sized ice sheets could not happen without some kind of viscous material below it. Therefore, the ocean acts as lubrication for the movement and constant crashing at glacier speeds of the massive surface ice layers.
Astonishingly, some scientists estimate that the total volume of water in Europa’s subsurface oceans to be around three quadrillion cubic kilometers (720 trillion mi3). That’s more than twice the volume of Earth’s oceans. On average, the subsurface Europa oceans are estimated to be around 100 kilometers (60 mi) deep!
3 Ice Geysers
In 2018, NASA scientists announced the presence of ice geysers on Europa’s surface. This discovery came after analyses of images taken of the surface in 1997 by the Galileo spacecraft, which showed plumes of vented water vapor above Europa’s surface. The geysers gush warmer water from the subsurface ocean below.
Europa is not the only moon in our solar system where ice geysers exist. One of Saturn’s moons, Enceladus, has also been shown to have large-scale ice geysers. When Galileo photographed Europa’s ice geysers, it accidentally caught glimpse of them as it passed 200 kilometers (124 mi) above the surface and through a plume.
2 You Wouldn’t Last Long
Like the other Galilean moons orbiting Jupiter, Europa receives an intense dose of radiation from its parent planet. Solar radiation combined with energetic particles from Jupiter’s powerful magnetic field deliver a deadly dose of radiation to the moon’s surface of about 5,400 millisieverts (mSv) per day.
To give some comparison, an ordinary medical CT scan produces only six to 20 millisieverts. Suffice to say, you wouldn’t want to be on the surface of Europa without some serious protection.
1 Focus For Life
In the search for life in our solar system, Europa is among the most exciting places. The presence of vast water oceans beneath Europa’s frozen surface has scientists believing in the possibility of life below. It is thought that at the bottom of Europa’s icy depths, warm geothermal vents exist, from which warm water bubbles upward. These thermal vents would be a possible location for life to evolve, just like how many odd types of deep sea creatures reside at the bottom of Earth’s oceans.
It is thought that Europa produces ten times more oxygen than hydrogen in its oceans, which is similar to Earth. Therefore, chemical reactions from hydrothermal vents and the abundance of oxygen in the water makes Europa one of the top candidates for finding life in our solar system!
Read about more amazing natural satellites on 10 Facts About Moons That Just Might Blow Your Mind and 10 Moons Humans Could Colonize. | 0.861992 | 3.300529 |
Scientists get first look inside comet from outside our solar system
Posted April 20, 2020 11:01 a.m. EDT
CNN — When interstellar comet 2I/Borisov entered our solar system last year, this time capsule from another place in the universe opened and revealed information about its origin, according to new research.
Since it was first observed in 2019, the comet has been streaming across our solar system and the heat of our sun has caused it to shed gas. Within that gas and the melting bits of the comet is information, some of which could be millions or even billions of years old.
In December, astronomers ensured that telescopes in space and on the ground were oriented to observe the comet's closest approach to Earth. It passed within 190 million miles of Earth, shedding more gas and dust evaporating through its cometary tail.
This close (for a comet) pass was observed by the Atacama Large Millimeter/submillimeter Array of telescopes in Chile, known as ALMA.
"This is the first time we've ever looked inside a comet from outside our solar system," said Martin Cordiner, astrochemist at NASA's Goddard Space Flight Center in Maryland and an author of one of two studies on the comet that published Monday.
"And it is dramatically different from most other comets we've seen before," he said in a statement.
Astronomers could identify the gas streaming from the comet, which contained an unusually high amount of carbon monoxide -- more than has been identified in a comet within two times the distance from the Earth to the sun, according to the study published in the journal Nature Astronomy. This suggests that the comet may have formed under different circumstances than those in our own solar system.
A second study about the nature of the carbon monoxide also published Monday in Nature Astronomy.
The amount of carbon monoxide is thought to be between nine and 26 times greater than the average comet in our solar system.
The also detected hydrogen cyanide, which was expected and the amount was similar to that found our solar system's comets.
"The comet must have formed from material very rich in [carbon monoxide] ice, which is only present at the lowest temperatures found in space, below -420 degrees Fahrenheit (-250 degrees Celsius)," said Stefanie Milam, study co-author and planetary scientist at NASA's Goddard Space Flight Center in Maryland, in a statement.
Carbon monoxide is common in comets, but the amount appears to vary.
Astronomers believe this variation might be due to the particular region where the comet was formed, or how often a comet is brought closer to a star due to its orbit. This closer approach causes it to melt and shed elements that evaporate easily.
"If the gases we observed reflect the composition of 2I/Borisov's birthplace, then it shows that it may have formed in a different way than our own solar system comets, in an extremely cold, outer region of a distant planetary system," said Cordiner. This region can be compared to the cold region of icy bodies beyond Neptune, called the Kuiper Belt.
Comets can uniquely preserve information about how they were formed because most of the time, they're far away from stars and cold enough that they remain unchanged.
For now, astronomers don't know what kind of star the comet orbited before being kicked out of its solar system and sent into ours. Astronomers suspect the eviction occurred when the comet interacted with the gravity of its host star or a giant planet in the system.
It's been traveling on its own, for millions or billions of years, and then entered our solar system and was spotted in August 2019.
So where did it come from?
The comets in our solar system are leftovers from the material that makes planets, which was found in a protoplanetary disk around our sun.
The ALMA group of telescopes can observe disks around younger versions of stars similar to our sun.
These protoplanetary disks contain gas and dust where planets pull together and form -- and leftover pieces of this gas, dust and ice form comets. So it's possible that the star this comet orbited was a younger version of our sun.
And the melting elements from the comet tell us what could be found in a protoplanetary disk around a star in another solar system.
"ALMA has been instrumental in transforming our understanding of the nature of cometary material in our own solar system -- and now with this unique object coming from our next door neighbors," said Anthony Remijan, study co-author and at the National Radio Astronomy Observatory in Charlottesville, Virginia, in a statement.
"It is only because of ALMA's unprecedented sensitivity at submillimeter wavelengths that we are able to characterize the gas coming out of such unique objects."
This is only the second interstellar object to cross into our solar system after 'Oumuamua was spotted in 2017. Astronomers didn't have long to observe it, and it was classified as an interstellar asteroid.
But 2I/Borisov is with us for longer. And its signature cometary tail gave it away as an interstellar comet.
The comet won't remain in our solar system, despite the gravity of our sun, because it's zipping along at 100,000 miles per hour. By June 2020, the comet will be well past Jupiter and on its way back to interstellar space.
"2I/Borisov gave us the first glimpse into the chemistry that shaped another planetary system," said Milam.
"But only when we can compare the object to other interstellar comets, will we learn whether 2I/Borisov is a special case, or if every interstellar object has unusually high levels of CO (carbon monoxide)." | 0.893467 | 3.715439 |
An exploding star has suddenly appeared in the night sky, dazzling astronomers who haven't seen a new supernova so close to our solar system in more than 20 years.
In just the last few days, a the supernova emerged as a bright light in Messier 82 - also known as the Cigar Galaxy - about 12 million light-years away in the constellation Ursa Major, or the Great Bear. The supernova, which one astronomer described as a potential "Holy Grail" for scientists, was first discovered by students at the University College London.
Positioned between the Big Dipper and the Little Dipper, the new supernova should be easy for skywatchers in the Northern Hemisphere to spot through a telescope. It may even brighten enough to be visible through a small pair of binoculars, said astronomer Brad Tucker, of the Australian National University and the University of California at Berkeley. Beyond creating a skywatching spectacle, the cosmic event may also afford astronomers a rare opportunity to study an object that might help them understand dark energy.
Read the whole article here. | 0.858123 | 3.087862 |
Astrophysicist predicts detached, eclipsing white dwarfs to merge into exotic star
A University of Oklahoma astrophysicist, Mukremin Kilic, and his team have discovered two detached, eclipsing double white dwarf binaries with orbital periods of 40 and 46 minutes, respectively. White dwarfs are the remnants of Sun-like stars, many of which are found in pairs, or binaries. However, only a handful of white dwarf binaries are known with orbital periods less than one hour in the Milky Way—a galaxy made up of two hundred billion stars—and most have been discovered by Kilic and his colleagues.
"Short-period white dwarf binaries are interesting because they generate gravitational waves. One of the new discoveries emits so much gravitational waves that it is a new verification source for the upcoming Laser Interferometer Space Antenna—a gravitational wave satellite," Kilic said.
Kilic, an astrophysics professor in the Homer L. Dodge Department of Physics and Astronomy, with OU graduate students Alekzander Kosakowski and A. Gianninas, and collaborator Warren R. Brown, Smithsonian Astrophysical Observatory, discovered the two white dwarf binaries using the MMT 6.5-meter telescope, a joint facility of the Smithsonian Institution and the University of Arizona. Observations at the Apache Point Observatory 3.5-meter telescope revealed that one of the binaries is eclipsing, only the seventh known eclipsing white dwarf binary.
In the future, Kilic and his team will watch in real time as the stars eclipse to measure how they are getting closer and closer—a sign they will likely merge. What occurs when the white dwarfs make contact continues to be a mystery at this point. One possibility is an explosion—a phenomenon known as a supernova. Kilic predicts these two stars will come together and create an "exotic star," known as R Coronae Borealis. These stars are often identified for their spectacular declines in brightness at irregular intervals. There are only about 65 R Coronae Borealis stars known in our galaxy.
"The existence of double white dwarfs that merge in 20 to 35 million years is remarkable," Brown said. "It implies that many more such systems must have formed and merged over the age of the Milky Way." | 0.90834 | 3.840675 |
Saturn’s icy moon Enceladus is of great interest to scientists due to its subsurface ocean, making it a prime target for those searching for life elsewhere. New research led by Carnegie’s Doug Hemingway reveals the physics governing the fissures through which oceanwater erupts from the moon’s icy surface, giving its south pole an unusual “tiger stripe” appearance.
“First seen by the Cassini mission to Saturn, these stripes are like nothing else known in our Solar System,” lead author Hemingway explained. “They are parallel and evenly spaced, about 130 kilometers long and 35 kilometers apart. What makes them especially interesting is that they are continually erupting with water ice, even as we speak. No other icy planets or moons have anything quite like them.”
Working with Max Rudolph of the University of California, Davis and Michael Manga of UC Berkeley, Hemingway used models to investigate the physical forces acting on Enceladus that allow the tiger stripe fissures to form and remain in place. Their findings are published by Nature Astronomy.
The team was particularly interested in understanding why the stripes are present only on the moon’s south pole but were also keen to figure out why the cracks are so evenly spaced.
The answer to the first question turns out to be a bit of a coin toss. The researchers revealed that the fissures that make up Enceladus’ tiger stripes could have formed on either pole, the south just happened to split open first.
Enceladus experiences internal heating due to the eccentricity of its orbit. It is sometimes a little closer to Saturn and sometimes a littler farther, which causes the moon to be slightly deformed – stretched and relaxed – as it responds to the giant planet’s gravity. It is this process that keeps the moon from freezing completely solid.
Key to the formation of the fissures is the fact that the moon’s poles experience the greatest effects of this gravitationally induced deformation, so the ice sheet is thinnest over them. During periods of gradual cooling on Enceladus, some of the moon’s subsurface ocean will freeze. Because water expands as it freezes, as the icy crust thickens from below, the pressure in the underlying ocean increases until the ice shell eventually splits open, creating a fissure. Because of their comparatively thin ice, the poles are the most susceptible to cracks.
The researchers believe the fissure named after the city of Baghdad was the first to form. (The stripes are named after places referred to in the stories of One Thousand and One Nights, which are also called Arabian Nights.) However, it didn’t just freeze back up again. It stayed open, allowing ocean water to spew from its crevasse that, in turn, caused three more parallel cracks to form.
“Our model explains the regular spacing of the cracks,” Rudolph said.
The additional splits formed from the weight of ice and snow building up along the edges of the Baghdad fissure as jets of water from the subsurface ocean froze and fell back down. This weight added a new form of pressure on the ice sheet.
“That caused the ice sheet to flex just enough to set off a parallel crack about 35 kilometers away,” Rudolph added.
That the fissures stay open and erupting is also due to the tidal effects of Saturn’s gravity. The moon’s deformation acts to keep the wound from healing–repeatedly widening and narrowing the cracks and flushing water in and out of them–preventing the ice from closing up again.
For a larger moon, its own gravity would be stronger and prevent the additional fractures from opening all the way. So, these stripes could only have formed on Enceladus.
“Since it is thanks to these fissures that we have been able to sample and study Enceladus’ subsurface ocean, which is beloved by astrobiologists, we thought it was important to understand the forces that formed and sustained them,” Hemingway said. “Our modeling of the physical effects experienced by the moon’s icy shell points to a potentially unique sequence of events and processes that could allow for these distinctive stripes to exist.” | 0.889981 | 3.916056 |
For the first time, astronomers have witnessed the birth of a colossal cluster of galaxies. Their observations reveal at least 14 galaxies packed into an area only four times the diameter of the Milky Way’s galactic disk. Computer simulations of the galaxies predict that over time the cluster will assemble into one of the most massive structures in the modern universe, the astronomers report in the April 26 issue of Nature.
Galaxies within the cluster are churning out stars at an incredible pace, ranging from 50 to 1,000 times the Milky Way’s star formation rate. These rates are higher than can be explained for solitary galaxies, suggesting that the galaxies are influencing one another and are actively assembling into a cluster.
“More so than any other candidate discovered to date, this seems like we’re catching a cluster in the process of being assembled,” says study co-author Chris Hayward, an associate research scientist at the Center for Computational Astrophysics at the Flatiron Institute in New York City. “This is the missing link in our understanding of how clusters form.”
Galaxy clusters are the largest structures held together by gravity in the present-day universe and contain hundreds or even thousands of galaxies. Clusters grow over time as gravity draws in more material. This newborn galaxy cluster, or protocluster, is around 12.4 billion light-years away from Earth. That distance means that the protocluster appears today as it existed 1.4 billion years after the Big Bang.
How the assembly of galaxies got so big so fast “is a bit of a mystery,” says study co-author Scott Chapman, the Killam Professor in astrophysics at Dalhousie University in Halifax, Canada. “It wasn’t built up gradually over billions of years, as you might expect.”
Chapman, Hayward, Tim Miller of Yale University, and collaborators spotted the protocluster during a follow-up to a survey conducted using the South Pole Telescope in Antarctica. That undertaking inspected around 6 percent of the sky, but with relatively coarse resolution. In those observations, the protocluster was the brightest light source not magnified by the effect of a massive object’s gravity, which bends light like a lens. While bright, the source just looked like a fuzzy blob composed of at least three galaxies. An additional study by the Atacama Large Millimeter/submillimeter Array in Chile provided clarity and a surprise.
“It just hit you in the face because all of a sudden there are all these galaxies there,” Chapman says. “We went from three to 14 in one fell swoop. It instantly became obvious this was a very interesting, massive structure forming and not just a flash in the pan.”
In total, the protocluster contains around 10 trillion suns’ worth of mass. All that material in such a confined space means that the galaxies will probably merge over time, rather than drift apart. A numerical simulation developed by Hayward, Chapman and colleagues projected how the protocluster would grow over the next billion years. Over that time span, the 14 galaxies will merge into one giant elliptical galaxy surrounded by a halo of galaxies, stars and dust. The researchers estimate that in the modern-day universe, the cluster will contain roughly 1,000 trillion suns’ worth of mass. That’s comparable to the mass of the Coma cluster of galaxies that lies a few hundred million light-years from Earth.
The surprisingly high star formation rates within the galaxies provide further evidence that the galaxies are forming a cluster, says Hayward. The observed surge of star formation during the protocluster’s assembly fits with the composition of modern galaxy clusters, which contain an abundance of old stars of around the same age. “There’s some special aspect of this environment that’s causing the galaxies to form stars much more rapidly than individual galaxies that aren’t in this special place,” says Hayward. One possible explanation is that the gravitational tug of neighboring galaxies compresses gas within a galaxy, triggering star formation.
The protocluster is a precursor to the larger and more mature galaxy clusters seen in the modern universe, making the protocluster an excellent test bed for learning more about how present-day clusters formed and evolved. Modern clusters, for instance, brim with superheated gas that can reach temperatures of more than 1 million degrees. Scientists aren’t sure how that gas got there, though. The high rate of star formation in the newly discovered protocluster may provide a clue: A deluge of newborn stars in a forming cluster may spew hot gas into the voids between the galaxies. That expelled gas is not dense enough to form stars and instead lingers throughout the cluster.
Further exploration of protoclusters will provide additional insight, Chapman says. The group has already identified two more protoclusters from the South Pole Telescope survey, though they are not as spectacular, he says. “As we flush out the details of those, we’ll see just how similar they are to this structure.” | 0.837454 | 3.975275 |
A generation ago, the number of planets known in the universe was just nine: the nine of our solar system (then including Pluto). Scientists were almost certain there were more, but that was just a logical supposition made after they realized that stars were suns like our sun, not dots of light painted on a celestial sphere. No one could confirm they actually existed.
Technology has been solving that problem, but another big question remains: Could any of those planets sustain life? N. Jeremy Kasdin ’85, a professor of mechanical and aerospace engineering and vice dean of Princeton’s school of engineering, thinks that it could be possible to answer that question, too, within a decade or so.
“The universe is teeming with planets,” Kasdin said in Vancouver in March 2014 as he began his talk at the annual TED conference, perhaps the world’s hippest gathering on topics of technology, entertainment, and design (hence the acronym). Astronomers believe that every star in the galaxy has a planet, he explained — and up to one-fifth could have an Earth-like planet that might be able to sustain life.
Then he laid out a grandiose game plan: “to build a space telescope that will be able to image an Earth about another star and figure out whether it can harbor life.” In his six-and-a-half-minute talk, since viewed more than a million times on the Web, Kasdin described a simple idea suggested more than half a century ago by Lyman Spitzer *38, the late Princeton astrophysicist who came up with the notion of putting telescopes in space.
Just as the moon blots out the sun during a solar eclipse, Kasdin said, a large screen placed far in front of a space telescope could block the light coming from a distant star, enabling the telescope to spot much dimmer planets in orbit around that star.
“That’s not science fiction,” said Kasdin, who has been developing the technology to build just such a screen — he calls it a starshade — in collaboration with NASA’s Jet Propulsion Laboratory.
“I think this is the coolest possible science,” he concluded in his TED talk. “That’s why I got into doing this — because I think that will change the world.”
The study of planets beyond our solar system — what astronomers call extrasolar planets or exoplanets — has become one of the hottest research areas in astronomy, including at Princeton. The configuration of planets around other stars often looks very different from our solar system, which is “beginning to look odd,” says Adam Burrows, a theoretical astrophysicist at Princeton.
Some giant exoplanets, much larger than Jupiter, are broiled to thousands of degrees as they orbit their parent stars at a fraction of the distance at which Mercury circles the sun. Others are “super-Earths” — rocky planets that are several times more massive than the one we live on.
The discoveries have spurred questions, mostly unanswered. How many stars have planets? What determines whether a star has planets? What does a typical planetary system look like? How common is a place like Earth? Is there life on any of the planets, and could we tell?
Since the middle of the 19th century, astronomers have been searching for hints of unseen planets subtly changing the behavior of their parent stars. Claims of discovery came and went, discredited.
In 1992, the first two exoplanets at last were discovered and confirmed. But these orbited a pulsar — the charred remains of an exploded star. The fact that new planets could form in the aftermath of a cataclysmic explosion was a surprise, but nonetheless, the planets were largely curiosities because the chances of life arising there were considered minuscule.
At the time, Burrows was developing models to explain brown dwarfs, which are thought of as failed stars, not quite large enough to ignite. In 1995, Swiss astronomers Michel Mayor and Didier Queloz contacted him about observations they had made of a star named 51 Pegasi, 51 light-years away.
Mayor and Queloz saw clockwork fluctuations in the frequency of light from the star, which could be explained by the gravitational pull of a planet circling it. But it seemed to be an exceptionally strange planet. It was big, at least half the mass of Jupiter, yet almost hugging its parent star, orbiting at a distance that was less than one-seventh the distance at which Mercury orbits the sun. If a planet were causing the fluctuations, it was a planet that zipped around its star in just four days, versus the 365 days it takes for Earth — or the 4,332 days required for Jupiter — to complete a trip around the sun. Mayor and Queloz wanted to know if it was plausible for a planet that big to exist so close to the star.
Burrows calculated. It seemed strange, but there was no reason in physics that would make it impossible. “That emboldened the team to reveal their result,” he says. On Nov. 23, 1995, the scientific journal Nature published the discovery: the first planet found around a sunlike star outside of the solar system.
Many astronomers took a long time to believe that the weird planet really was a planet at all. Some critics suggested that perhaps 51 Pegasi was a variable star — a star whose brightness changes — and the variations in frequency arose from something going on in the star itself. “That still took a few people a few months or half a year to get their heads around it,” Burrows says. When they did, he says, “this subject started to explode.” The search for other exoplanets was on. More than 1,800 have been identified so far.
Over the first decade of the exoplanet era, the technique of radial velocity — looking for wiggles in the frequency of starlight — was the primary method of discovery. That told astronomers the distance of the planet from the star and a minimum mass, but not much else.
Others came up with different ideas. Princeton astrophysics professor Bohdan Paczynski — who initially was searching not for exoplanets but for dark matter, the unknown material that is believed to make up 85 percent of the universe — developed a technique called microlensing. When a massive object passes between Earth and a distant star, the object in the middle acts like a magnifying glass, its gravity bending and brightening the light of the distant star. It turns out that if the intervening object is a star with a planet, the planet also can be detected because its gravity bends the light but in a slightly different direction. Think of it as a small imperfection in a lens, a distortion.
The unavoidable shortcoming of this technique is that no one ever will see a microlensed planet twice, which means that follow-up observations are out of the question. Still, microlensing has revealed at least 34 exoplanets, including one of the smallest, 20,000 light-years away and about 5.5 times the mass of Earth. Researchers showed Paczynski that data before he died of cancer in April 2007.
Another, more straightforward, method is to stare at a large number of stars and look for repeated dips in brightness. The dips could be a planet passing in front, partially blocking the starlight. That is how NASA’s $600 million Kepler space telescope turned up nearly 1,000 planets after continuously observing 150,000 stars for four years. It’s also what Princeton astrophysics professor Gaspar Bakos is doing on a much smaller, cheaper scale from the ground, with a network of telescopes known as HATNet.
Bakos originally was not interested in planets, but in variable stars that pulsed in brightness or color. Sometimes the internal machinations of the star drove the changes. Sometimes a variable star turned out to be two stars orbiting each other. Such variable stars were discovered centuries ago, and thousands already had been catalogued. But Bakos figured that inexpensive telescopes could discover far more, leading to new insights.
In 1999, while still a college undergraduate in Hungary, Bakos teamed up with engineers he met through an astronomy club to build a prototype of the HAT telescope, short for Hungarian-made Automated Telescope. It consisted of a secondhand Nikon telephoto lens paired with a large image sensor. That prototype was tested at an observatory in Budapest and later at the Steward Observatory in Arizona.
The one prototype burgeoned into HATNet, six fully robotic telescopes installed at the Whipple Observatory in Arizona and Mauna Kea in Hawaii. The telescopes determine, without guidance from humans, what and when to observe, based on the weather and pre-programmed priorities.
Bakos realized that with the telescopes’ ability to spot minuscule changes in brightness, he could pivot his research to search for exoplanets. So far, HATNet has found 55 of them, including oddities like a planet that is larger than Jupiter but has just half Jupiter’s mass — a puffy planet with the unbelievably low density of cork. Another is a superheavy Jupiter — the same size yet nine times as massive.
More recently, Bakos set up HATSouth, a network of somewhat larger telescopes in the Southern Hemisphere: in South Africa, Australia, and South America. The three locations, barring clouds or malfunction, keep continuous watch on the southern night sky.
Bakos travels to repair and upgrade his telescopes. The rest of the time, he monitors events on the computer screen in his Princeton office, zipping through time-lapse movies of observations of the night before. Cameras also record the unusual, like a mule scratching its back against the dome of one of the telescopes.
“It’s a highly productive network, and it was done on a shoestring budget,” he says.
The technology of exoplanet discovery has progressed so far so quickly that it soon could be readily within the reach of amateurs and digital cameras. It would require a fancy single-lens reflex camera with a powerful telephoto lens, but still equipment anyone could buy — not just a big observatory or a multi-million-dollar NASA mission. Within a few years, Bakos says, the sensors in such cameras will be sensitive enough to discern the dimming of passing planets.
The next goal, as Kasdin explains, is to move beyond the indirect detection of planets to photographing the exoplanets themselves. Astronomers want a picture of Earth 2.0.
Once they have a picture, new avenues of research become possible. Scientists could start identifying molecules floating in the atmospheres of these Earth twins, maybe even finding the chemical fingerprints of faraway life.
Already, ground-based telescopes have taken some snapshots of exoplanets, but only big ones at a considerable distance from their stars. Kasdin’s group is constructing an instrument to be installed on the Suburu telescope in Hawaii that will study the chemical makeup of large exoplanets.
For years, NASA’s astrophysics roadmap included an ambitious, pricey mission called Terrestrial Planet Finder — an immense space telescope that could photograph smaller Earth-like planets. NASA considered two potential designs, but the idea was postponed repeatedly and scrapped in 2011.
The challenges are immense. A small planet light-years away is extremely dim. More challenging, the dim dot of light from that planet is washed out in the glare of a blindingly bright star right next to it.
Enter Kasdin’s starshade.
Because light acts like waves, the optimal shape for blocking out the light is not a circle. Some of the light bends, like water flowing around a rock. That’s part of the reason it does not become dark as night during a solar eclipse — about a thousandth of the sun’s light still makes it to the ground. To spot Earth-size planets, Kasdin says, the starshade would have to block all but one 10-billionth of the star’s light.
Kasdin and his collaborators have demonstrated that a shade shaped like the petals of a sunflower can work. The light bends less as it passes the petal shapes, and the light that does pass around the shade in effect cancels itself out, producing a darker shadow.
A prototype of a single full-size petal — 6 meters (19.7 feet) tall — was built at NASA’s Jet Propulsion Laboratory in California; a complete model with a full complement of 30 petals would be the size of half a football field. To fit inside a rocket, the starshade would have to be folded up like an umbrella, another technological challenge.
Two summers ago, four undergraduate interns from Princeton and MIT, working at the Jet Propulsion Laboratory, built four smaller petals that verified that the petals repeatedly and precisely, within a fraction of a millimeter, could unfurl to the desired shape. Kasdin says he has obtained space in the basement of Frick Chemistry Lab to build an even smaller prototype of a starshade with all its petals. Scaled down to account for the 31,000 miles of space between the telescope and the starshade, the prototype will be only 2 inches wide — allowing Kasdin to determine how dark the shadow will be.
The next likely opportunity for a space-based mission to photograph exoplanets is a Hubble-class telescope that originally was built to be a spy satellite but then was donated by the National Reconnaissance Office to NASA to be used for science. The telescope has the unwieldy name of Wide-Field Infrared Survey Telescope-Astrophysics Focused Telescope Assets and a long acronym: WFIRST-AFTA. “I think WFIRST will be the next big step on this,” says Princeton’s astrophysics department chair, Professor David Spergel ’82, who also is the co-chairman of WFIRST’s science-definition team. He hopes that NASA will give the green light to launch the mission sometime in the first half of the next decade.
The primary mission of the telescope would be to study the mysterious dark energy that appears to be accelerating the expansion of the universe. But a second objective would be to find planets through microlensing events, and a third would be to photograph planets around nearby stars — not with a starshade (though Kasdin hopes a starshade still could be incorporated), but with a technique known as a coronagraph.
Kasdin is involved with that effort, too. Unlike a starshade that would fly thousands of miles away, a coronagraph is part of the telescope’s optics, somewhat like a black spot drawn on your glasses to block out some of the light. Kasdin heads one of two teams coming up with proposals for the coronagraph design. Like a starshade, the optimal shape is not a circle, but a more intricate design. It is not quite as effective as a starshade, Kasdin says. Still, the coronagraph should allow WFIRST to get photographs of planets similar to Saturn and Uranus. WFIRST also should be able to study small gas planets known as mini-Neptunes.
Then, with photographs, astronomers can start looking at specific colors of light that are absorbed by the planets’ atmospheres, which might explain what is in the planets’ air. Even observing an Earth-size planet is possible, though Kasdin is not optimistic about that. “If you got really lucky, and everything performed right and there happened to be an Earth around a nearby star that’s bright, it could see it,” he says. “More likely not.”
Meanwhile, NASA has financed the drawing up of preliminary plans for two missions devoted to the search for exoplanets — one of them, using a starshade. But scientists think that the project — or any starshade-equipped telescope capable of photographing Earth twins — is likely to wait for the round of grand projects expected to be deployed in the late 2020s or early 2030s.
Even with the hundreds of exoplanets already discovered, astronomers have only a partial picture. They know there are many planets they cannot yet see, and understand that they sometimes draw unwarranted conclusions from sparse and noisy data. “Planets are more complicated than stars,” Burrows says.
For example, if aliens a few tens of light-years away were looking at our solar system with our technology, they would not detect eight planets but probably just two — Jupiter and Saturn. The inner rocky planets likely would be too small; Uranus and Neptune would be too far out and moving too slowly to show up in the data.
But eventually, better tools will be developed, and scientists will collect enough data for stronger conclusions. “In the next decade or two,” Burrows says, “we’re going to start making it a real science.”
Kenneth Chang ’87 is a science reporter for The New York Times. | 0.891049 | 3.652753 |
Astronauts face myriad dangers in space, and at least one is perfectly familiar to the earthbound: cancer. The risk is so escalated that it stands firmly in the way of deep-space exploration. A European Union-funded research group is working to fix that.
The European Space Radiation Superconducting Shield project, comprising scientists from seven European research organizations, is developing a force field.
Technically, it's a superconducting magnetic shield. Scientists want to surround a spacecraft with a magnetic field something like the magnetosphere that surrounds Earth, which helps protect the planet from the cosmic rays that bombard astronauts in space.
Cosmic rays, the ones that gave the Fantastic Four their superpowers, are highly energized, charged subatomic particles. They include solar energetic particles expelled by solar flares and galactic cosmic rays produced by events like supernovas. Galactic cosmic rays are the most problematic in the radiation context. Speaking to Wired in 2014, Dr. Francis Cucinotta, a health physics professor with the University of Nevada, Las Vegas, said among radiation types, galactic cosmic radiation creates especially aggressive tumors.
Spacecraft currently have shielding, but it's the passive type, according to Dr. Amalia Ballarino, a project scientist from consortium member CERN, the European Organization for Nuclear Research.
"Spacecraft are built with specific materials that mitigate the effect of radiation," writes Ballarino in an email. However, passive shielding isn't effective against the most damaging radiation sources. Galactic cosmic rays, which originate beyond our solar system, move so fast these shields can't stop them.
The Space Radiation Superconducting Shield, or SR2S, is an active-shielding approach. It would use superconducting magnets to generate a magnetic field 3,000 times stronger than the one protecting Earth. Magnetic fields alter the paths of charged particles. SR2S would create a 30-foot (10-meter), cosmic-ray-deflecting force field around a spacecraft.
"The magnet system must be light and stable," says Ballarino. "Different magnets and coil configurations have been studied." Scientists developed a specific conductor for the application, titanium-clad MgB2. The resulting magnetic shield wouldn't block everything, but it would reduce an astronaut's radiation dose to what Ballarino calls "acceptable levels," making deep-space travel ethically possible.
Closer to Home
The success of active shielding also has broader implications. NASA limits astronauts to a 3-percent increase in their risk of dying from cancer. Once they've absorbed enough cosmic radiation to meet that limit, they can't go back to space (on NASA's dime, at least). Ineffective shielding dramatically shrinks the pool of candidates who qualify for certain mission types.
It also promotes a gender bias in candidacy. Women have a lower radiation threshold than men due to the unique risks associated with breast, uterine and ovarian cancers. This means women meet the 3-percent mark faster than their male colleagues. Women are automatically out of the running for up to half of all missions due to anatomy.
The SR2S project expects to demonstrate the viability of the superconducting magnetic shield by the end of 2015, says Ballarino, which is when the project ends. If successful, project literature estimates real-world implementation within 20 years. | 0.842932 | 3.445076 |
The NASA MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft, which is currently in orbit around Mars, has been taking monthly measurements of the speed and direction of the winds in the upper atmosphere of Mars between about 140 to 240 km above the surface. The observed wind speeds and directions change with time and location, and sometimes fluctuate quickly. These measurements are compared to simulations from a computer model of the Mars atmosphere called M-GITM (Mars Global Ionosphere-Thermosphere Model), developed at U. of Michigan. This is the first comparison between direct measurements of the winds in the upper atmosphere of Mars and simulated winds and is important because it can help to inform us what physical processes are acting on the observed winds. Some wind measurements have similar wind speeds or directions to those predicted by the M-GITM model, but sometimes, there are large differences between the simulated and measured winds. The disagreements between wind observations and model simulations suggest that processes other than normal solar forcing may become relatively more important during these observations and alter the expected circulation pattern. Since the global circulation plays a role in the structure, variability, and evolution of the atmosphere, understanding the processes that drive the winds in the upper atmosphere of Mars provides key context for understanding how the atmosphere behaves as a whole system.
A basic version of the M-GITM code can be found on Github as follows:
and About 30 Neutral Gas and Ion Mass Spectrometer (NGIMS) wind campaigns (of 5 to 10 orbits each) have been conducted by the MAVEN team (Benna et al., 2019). Five of these campaigns are selected for detailed study (Roeten et al. 2019). The Mars conditions for these five campaigns have been used to launch corresponding M-GITM code simulations, yielding 3-D neutral wind fields for comparison to these NGIMS wind observations. The M-GITM datacubes used to extract the zonal and meridional neutral winds, along the trajectory of each orbit path between 140 and 240 km, are provided in this Deep Blue Data archive. README files are provided for each datacube, detailing the contents of each file. A general README file is also provided that summarizes the inputs and outputs of the M-GITM code simulations for this study.
Roeten, K. J., Bougher, S. W., Benna, M., Mahaffy, P. R., Lee, Y., Pawlowski, D., et al. (2019). MAVEN/NGIMS thermospheric neutral wind observations: Interpretation using the M‐GITM general circulation model. Journal of Geophysical Research: Planets, 124, 3283– 3303. https://doi.org/10.1029/2019JE005957 | 0.82678 | 4.016414 |
Asteroid diversion: Could projectile impacts be the answer?
The Earth’s surface contains many craters and scars left behind by asteroid impacts – although many of these are covered by water. In the billions of years since our planet’s formation, these asteroids have been on the offensive. But for the first time ever, humankind has taken the battle to the asteroids.
On April 5th, Japan’s Hayabusa2 spacecraft launched a 2.5-kg copper projectile at a speed of 2 km per second into the asteroid Ryugu. The objective was to form a crater in order to uncover subsurface material that will be brought back to Earth for analysis.
“We are expecting it to form a distinctive crater,” says Patrick Michel, CNRS Director of Research of France’s Côte d’Azur Observatory as well as co-investigator and interdisciplinary scientist on the Japanese mission. “But we don’t know for sure yet, because Hayabusa2 was moved around to the other side of Ryugu, for maximum safety.”
The low gravity on the asteroid leads the scientists to believe that most of the material dispersed by the impact would have gone out into space – but it’s also possible that lower-velocity debris might have gone into orbit around the asteroid and could pose a danger to the spacecraft.
“So the plan is to wait until this Thursday, 25 April, to go back and image the crater,” explains Michel. “We expect that very small fragments will meanwhile have their orbits disrupted by solar radiation pressure – the slow but persistent push of sunlight itself. In the meantime we’ve also been downloading images from a camera called DCAM3 that accompanied the SCI payload to see if it caught a glimpse of the crater and the early ejecta evolution.”
Simulations have projected that the crater will be about 2m in diameter, and should appear darker than the surrounding surface.
“For us this is an exciting first data point to compare with simulations,” says Michel. “But we have a much larger impact to look forward to in future, as part of the forthcoming double-spacecraft Asteroid Impact & Deflection Assessment (AIDA) mission.”
This ESA-backed Hera mission is planned for late 2022, and has the objective of creating an impact significant enough to divert the orbit of the 160 meter in diameter “Didymoon” asteroid.
“The actual relation between projectile size, speed and crater size in low gravity environments is still poorly understood,” Michel explains. “Having both SCI and Hera data on crater sizes in two different impact speed regimes will offer crucial insights. These scaling laws are also crucial on a practical basis, because they underpin how our calculations estimating the efficiency of asteroid deflection are made, taking into account the properties of the asteroid material as well as the impact velocity involved.”
The culmination of these two experiments could lead to a better understanding of asteroid deflection techniques – a potentially useful tool should a major asteroid ever be on a collision course with Earth. With this goal in mind, it would be an understatement to say that the entirety of our planet should be rooting for their success. | 0.810239 | 3.816201 |
Until 500 years ago most people other than a few far-sighted philosophical scientists imagined the sun, the planets and the stars all revolved around a stationary earth. After all, the same heavenly track made by the sun during the day is the planetary passageway at night. Eventually, the earth was shown by Nicolaus Copernicus to spin on its axis and revolve around the sun. Yet, the apparent orbit of the sun around the earth, the Ecliptic, is the principal model used by astronomers even now to plot the sun’s displacement in the sky. The Ecliptic Plane, Figure 2, is the two-dimensional slice defined by this imaginary solar orbit around the earth. The area shown represents approximately 50 quadrillion square miles. As with earth’s actual orbit of the sun, the Ecliptic is not quite circular. It is an ellipse whose major axis is the red line. Aphelion is furthest separation. Perihelion is nearest approach. The radius is 150 million kilometers ±1.7%. The sun revolves counter-clockwise in this view. The beauty of visualizing with the Ecliptic is that Equinox solar positions are at precise right angles to Solstice solar positions. And the Cross Quarter moments exactly bisect these, forming perfect 90° angles with neighboring CQ’s. Only at Equinox moment is the sun on the earth’s Celestial Equatorial Plane, another two-dimensional slice extending into space, defined by the earth’s Equator. The Ecliptic Plane intersects this Equatorial Plane along the blue line in Figure 2, with their angle of intersection matching the 23°26′ polar tilt. By astronomical convention the 0° point on the Ecliptic is occupied by the sun at Vernal Equinox.
According to Johannes Kepler’s Second Law, any line between the earth and the sun sweeps out equal areas in equal time. Even in a slightly elliptical circuit, orbital velocity accelerates from Aphelion to Perihelionand decelerates from Perihelion to Aphelion. Thus, the sweep intervals along each 45° arc must be unequal due to unequal areas within each pie slice, offset as they are to the apparent orbit’s major axis stretching from the bulge near 102° to the flats near 282°. Table 1 displays the approximate time intervals in recent years along the eight 45° arcs.
“Solstices, equinoxes and seasonal midways called cross quarters were vital to ancient people for regulating their calendars and knowing when to plant, when to harvest, when to stay, when to move. From the earth on the ecliptic plane, the sun appears to cycle each year past the same, twinkling stars of the Zodiac. Equinoxes and solstices are separated by precise 90 degree angles according to astronomical convention. The cross quarters exactly bisect these and served as Celtic boundaries for each of the four seasons. The Celts named the cross quarters Beltaine, Lughnasad, Samain and Imbolc. Displayed below these names are the modern calendar dates that match them astronomically.”
1.3 MB ©MMV TransVision
Figure 3. Animation of changing sunrise locations up to 5 days before and after Equinoxes and Solstices in Northern Hemisphere
(for Northern Hemisphere sunsets, flip all labels horizontally; for Southern Hemisphere sunrises,
swap Equinox labels and swap Solstice labels; for Southern Hemisphere sunsets, reverse North and South labels only)
Figure 3 diagrams the offset of sunrise and sunset positions at the horizon — approximately equal to one solar diameter each day — near the Equinoxes, the greatest day-to-day movement at any time of the year. Ancient skywatchers almost certainly were aware of this. Near the Solstices sunrise and sunset positions at the horizon are approaching and receding from their annual extremes, reversing direction at some point within a virtual standstill of about a week’s duration. Solstices occur when the sun appears directly overhead at either of its most extreme latitudes — 23°26’N or 23°26’S — of the year. At Solstice the semi-annual northbound or southbound apparent journey of the sun turns around. It is practically impossible to determine exactly when a Solstice occurs based only on shadowplays cast by the rising or setting sun within the standstill week. With an intuitive grasp of the sun’s movement along the Ecliptic, and given a choice, ancient timekeepers would have found that memorializing either Equinox in stone, versus construction of a Solstice alignment, left posterity a superior tool to accurately clock the year.
Seasonal Cusps as Pagan and Religious Holidays
In common parlance Equinoxes are when day and night are equal in length and the sun rises due east and sets due west, assuming unobstructed and flat horizons. At the precise moment of Equinox, the sun crosses the earth’s Celestial Equatorial Plane. Religions likely discovered that by acknowledging and even honoring ancient and mythic sun ceremonies, non-believers could more readily be brought into the fold. Clerics termed the Vernal Equinox Eostar and the Autumnal Equinox Mabon to salute, perhaps even to sanctify, these special days of pagan worship. Likewise, the Church named Summer Solstice Litha and the Winter Solstice Yule. Here is a hint if you have ever wondered why Christmas and Easter have uncanny calendric correspondencies to the Winter Solstice and the Vernal Equinox. The supernova that may have been the Star of Bethlehem is not fixed historically on any specific date. Before Jesus was born, the Winter Solstice carried powerful mythic weight.
Watch our 3 minute video podcast on the Winter Solstice’s connection to Yule at the Store
The Vernal Equinox, around Easter, holds special magic, ushering in the return of warmth, and with it, the renewal of plant and animal life. Coincidentally, Christianity marks this time as the anniversary of the Resurrection.
Old Celtic calendars observed Cross Quarters, approximately midway between each pair of adjacent Equinox and Solstice days. Unlike modern calendars that define the start of a season on a Solstice or Equinox, the Celts perceived Solstices and Equinoxes as events occuring mid-season, with the seasons actually beginning and ending on the Cross Quarters.
Thus, Imbolc was the beginning of Spring. Imbolc corresponds more or less to Groundhog Day in the USA, February 2, when tradition has it that if a sleepy groundhog creeping out of its burrow at dawn sees its shadow, there are 6 more weeks of winter. (If not, we surmise, only 42 days remain.) Solmonath and Candlemas were Church-approved substitute names for Imbolc, which is spelled Imbolg by some pagans. Druids prefer Oimeaig, pronounced IM-mol’g.
Beltaine was the start of Summer, just a few days beyond May Day on the modern calendar. Fertility is at its peak as bees pollinate the flowers. Seedlings are poking through the cool soil, seeking the warmth and energy of the sun. Early Christians preferred the name Whitsuntide instead of Beltaine. The pronunciation of this cross quarter is BEE-awl-ten-ah
Lughnasad was the beginning of Autumn, when crops thrive in the hot sun. Lughnasad was observed as a pre-harvest festival day and time for strength and endurance competitions among young men. Variations on this CQ name include Lughnasadh, Lughnasada and Lugnasadh. It is pronounced LOO-na-sah regardless of the spelling. The religious equivalent is Lammas or Lammos.
The Celtic Winter began with Samhain. It ends one planting cycle and begins another. Seeds for the next year were often planted at this time. Samhain comes about a week after Hallowe’en, the eve of All Saints Day when, some folks believe, all departed souls of the preceding year are finally freed from earthly ties. Indeed, the Christian name Hallowmas was swapped for the pagan term, sometimes spelled as Savain. Regardless of the spelling, this CQ day is pronounced SOW-an or SOW-in.
Listen to our 3 minute podcast on Samhain and the Celtic New Year at the Store
Perhaps the Celtic perception of the seasonal calendar harmonizes best with nature. Should Summer’s arrival really mark a time of year when daytime just gets shorter and shorter? Is it logical for days to only lengthen throughout Winter? It seems to contradict our perception of what these seasons are, or is it just a mid-Summer’s night dream of mine? The Celts believed major transitional days — Solstices and Equinoxes — should be enveloped by the time of year they signify, not stand for mere boundary markers! Celtic calendar keepers favored the Cross Quarters as bookends for every season under the sun. | 0.910922 | 3.978145 |
Our solar system includes eight planets, which are divided into the inner planets that are closer to the sun and the outer planets that much, much farther away. In order of distance from the sun, the inner planets are Mercury, Venus, Earth and Mars. The Asteroid Belt (where thousands of asteroids orbit the sun) lies between Mars and Jupiter, making the outer planets, Jupiter, Saturn, Uranus and Neptune, even farther away from the sun, with larger orbits than the inner planets.
You Are What You're Made Of
According to the Beacon Learning Center, because the four inner planets are solid, composed of rock and metals, they are also called “rocky” or “terrestrial” planets. Far away not only in distance but in type of matter, the four outer planets are made up of gases and are generally denser toward the center. These outer planets are called “gas giants” and are sometimes referred to as “Jovian,” which means “like Jupiter,” the largest planet in our solar system.
Solid as a Rock
The four terrestrial planets contain similar rocks and metals. Their cores differ somewhat in state (molten, partially molten or solid), but iron is a major component in all four. These planets are small relative to the gas giants, their closely packed elements making for rocky planets with high densities. As rocky planets, their surfaces are solid.
All the terrestrial planets have landforms suggesting past or present volcanic activity. On Earth, of course, volcanic activity continues. Additionally, all four rocky planets show evidence of impact in the form of craters, although on Earth, water and winds have eroded much of the evidence, except in areas of minimal or no rainfall.
Size Isn't Everything
In contrast to the rocky planets, the larger, outer planets are primarily composed of gases, and have deep atmospheres. Due to the density of the rocky planets, their diameters are all less than 8,000 miles, as compared to the smallest of the gas giants, Neptune, which is 30,000 miles in diameter, according to NASA. Unlike the rocky planets, the gas giants are not similar in size to one another.
The rocky planets rotate on their axes slowly compared to the gas giants. The inner planets all take a 24-hour day or longer to fully rotate on their axes. Earth takes the least time at one day, and Venus takes the longest -- eight months -- to make one full rotation. In contrast, the speedy gas giants all complete their “daily” rotations in under 17 Earth hours, according to The Nine Planets.org.
Satellites and Rings
None of the inner planets have rings, while all of the outer planets have quite a few (rings are made up of small particles, possibly ice, that circle the outer planets). Inner planets have a paucity of moons, with Mars claiming two and Earth just one. Mercury and Venus have none. Each of the outer planets, on the other hand, has multiple satellites.
- Digital Vision./Digital Vision/Getty Images | 0.864125 | 3.789967 |
Supernovae are exploding stars that emit a large amount of energy in space. The optical light is so intense that one can to see tham at great distances that allow to probe cosmological models of the Universe. There are two main types of supernovae: types Ia and type II. Only supernovae Type Ia are used toconstrain cosmological models. Improved knowledge on supernovae is important.
The TAROT telescope at La Silla (Chile), led by astronomers of IRAP, has discovered a supernova during the night of 23 to 24 June 2012 in the galaxy ESO 139-G28 located 256 million light years away. The Las Campanas Observatory astronomers Chile have pointed the supernova and have obtained a spectrum with the Magellan telescope 6m50. They found that the supernova is of type Ia.
This result was recorded by the Astronomical Union International who gave the identification SN 2012db to this supernova.
The TAROT telescope is normally intended to observe the optical emission from star explosions (gamma ray-bursts) but it is also used for various other astrophysical studies. It was built in 2006 by a team of astronomers from IRAP. A second copy is installed in France. | 0.886344 | 3.271224 |
Astronomers have discovered a galaxy that formed just 400 million years after the Big Bang explosion — the most distant galaxy found to date.
- Galaxy GN-z11 is 13.4 billion light years from Earth
- Finding sets new cosmic distance record
- Galaxy formed when the universe was only 3 per cent of its present age
Located a record 13.4 billion light years from Earth in the direction of the constellation Ursa Major, the galaxy, named GN-z11, was first spotted two years ago in a Hubble Space Telescope deep-sky visible light survey.
At the time, astronomers knew they were seeing something very far away, possibly as distant as 13.2 billion light-years from Earth.
Follow-up observations with an instrument on Hubble that splits light into its component wavelengths revealed that GN-z11 was farther away than initially believed, setting back the galaxy-formation clock by another 200 million years.
Being able to use Hubble to peg the galaxy's distance was a surprise, said astronomers who will publish their research in next week's issue of The Astrophysical Journal.
"We've taken a major step back in time, beyond what we'd ever expected to be able to do with Hubble," Yale University astronomer Pascal Oesch said in a statement.
The key to the discovery was precisely measuring the shift of the galaxy's light into longer, redder wavelengths, which directly corresponds to how far the photons had travelled before reaching Hubble's eye.
The phenomenon is similar to the sound of a train whistle shifting pitch as it recedes into the distance.
Though small by modern galaxy standards, GN-z11 is huge considering it formed at a time when the universe was only 3 per cent of its present age, said astronomer Garth Illingworth with the University of California, Santa Cruz.
"We're seeing this galaxy in its infancy," Mr Illingworth said.
"It's amazing that a galaxy so massive existed only 200 million to 300 million years after the very first stars started to form."
GN-z11 contains about 1 billion times the mass of the sun.
The galaxy is about 25 times smaller than the Milky Way, though it is pumping out new stars 20 times faster than the present Milky Way.
Astronomers said they expected the new distance record to stand until Hubble's successor, the James Webb Space Telescope, is launched in 2018. | 0.818918 | 3.705416 |
For a complete list, including later questions not listed below, click here.
You may also link from here to a listing of questions arranged by topic.
(2) What accelerates the solar wind?
396B Posssibility of Asteroid Hitting Earth (2)
If you have a relevant question of your own, you can send it to
Before you do, though, please read the instructions
28. Where does space begin?I have a question about how far up do you have to go to get out of the earth's atmosphere to be in space. I would like this answer in the form of miles. I would gratly appreciate any information on this.
ReplyThe ocean has a well-defined top surface, where water ends and the atmosphere begins. The atmosphere doesn't: it gets more and more rarefied, and where space begins is open to interpretation.
Near the ground the atmospheric density drops to 1/2 every 5 kilometers (8 kilometers = 5 miles, very nearly), so at 10 km where jets fly, density is down to 1/4. This continues more or less up to 100 km (the halving distance varies a bit, with temperature), where collisions between molecules become relatively rare. Higher up the oxygen and nitrogen each decrease at its own rate.
The space shuttle flies at 300-400 kilometers, but even there enough air remains to seriously limit orbital lifetime. Also, enough of that air is ionized--electrons ripped off molecules by the Sun's extreme ultra violet, leaving behind positive "ions"--to reflect radio signals. Satellites orbit at 600-1000 km and up, and that, too, is where the first signs of the radiation belt can be observed, particularly off the Atlantic coast of Brazil, where the magnetic field is relatively weak.
Somewhere between here and there, you enter "space. "
29. Gravity at the Earth's Center(Two questions with the same answer)
(1) My students had a couple of questions that I thought were interesting.
I told them I'd ask ya'll.
Thank you for any light that you can shed.
ReplyDear Teacher (and this also answers the student of Newton):
Yours is an old question, first tackled by Newton, as the "Hollow Earth Paradox." If the Earth where a hollow sphere (inner and outer surfaces spherical) and someone dug a hole that reached the hollow interior, and then stepped into it--what would that person experience?
Newton's answer--there would be no gravity inside the hollow. Any object thrown into it--say, a stone--would continue in a straight line with constant velocity (ignoring air resistance).
Newton's argument was roughly as follows. Take an object at a point in space anywhere in the cavity and draw from it a double cone (like a teepee, extending to both sides). Each side of it will cut part of the sphere, and the gravity of the two parts will tend to pull the object in opposite directions (make a drawing and you will see).
Newton showed that the pulls of both part cancel each other: one part may be closer, but then it will also be smaller. Since all directions can be covered by a collection of such cones, the total force is zero. Today we get this result much more quickly by the theory of the potential, but that takes three-dimensional calculus, which Newton did not have.
Now: Imagine you are somehow in the middle of the solid Earth--by some magic, not crushed by the rocks, suffocated or incinerated. In your mind you can divide all matter on earth into two parts: a smaller sphere containing everything that is CLOSER than you to the Earth's center, and a hollow sphere containing everything that is MORE DISTANT.
By Newton, the hollow sphere exerts no pull, while the interior sphere, like the Earth, pulls as if all its mass were concentrated in the middle (that's another thing easily shown from potential theory). If you are halfway to the center, and the density everywhere is the same (actually, matter gets compressed towards the middle) then only 1/8 of the Earth mass is pulling you, but at half the distance, the pull is 4 times stronger ("inverse squares law"), so the final result is 1/2 of the gravity on the surface. At 1/N times the radius, the pull of gravity is just 1/N the pull at the surface.
As you get deeper and deeper, the inside sphere gets smaller and its pull is weaker, so gravity too weakens. At the center, it is zero. At 3 meters from the center, it is the pull of a 3-meter sphere of rock, experienced on its surface--the pull of a tiny asteroid.
Please note--that is just the pull of gravity on YOU. The rocks above you are also all pulled down, all the way to the surface of the Earth, and their weight is likely to crush you before you get very far. There may perhaps exist a cave a mile deep, but if so, none is much deeper, because there is too much weight piled on top.
30(a) Radiation hazard in space--1I am working at the University of Arkansas School of Architecture along with members of the Habitability team at NASA for the manned Mars mission. It has been explained to me that radiation will be a big issue in the design of a Mars habitat. I was wondering how feasible it would be to use nuclear power to produce a eletromagnetic field around the habitat to reduce or deflect the radiation. Is it possible to create a magnetic field strong enough to provide radiation protection? And if so, how much energy would it require?
ReplyDear Jim I have not calculated the field needed, but it is probably very strong, too expensive to set up, too much mass and energy are needed, and a strong magnetic field would affect instruments.
The cheap and simple way is to build a shelter--especially since the dangerous events are the ones of solar outbursts, which are rare and last a day at most. You can calculate the shielding, but 20-50 cm rock should do a pretty good job (remember gravity is weaker, too, they will weigh less than on Earth).
Have you read Ben Bova's "Mars"? It's fanciful science fiction, but his physics seems OK. The Mars astronauts are hit by a solar outburst halfway to Mars and wait it out, huddled in a special shielded area of their spaceship.
30(b) Radiation hazard in space--2I was browsing through some message boards and came across a very interesting discussion about the favorite 'We Never Landed On the Moon' conspiracy theories. A major player in this discussion is of course the plausibility of astronauts, film, and equipment surviving the radiation of the inner and outer Van Allen belts during the Apollo series.
Is it possible for humans to survive a trip through these belts with the shielding that was available on the Apollos?
What are the lethal exposure periods for humans in the areas of the strongest radiation? And does the moon itself provide some shielding from cosmic and other solar radiations?
I do not know exactly how much radiation a person would suffer going (twice, in and out) through the radiation belt, but it is tolerable. A dangerous dose is 200 rad and up, and I once calculated that going through the inner belt, the solar cells of a satellite shielded by 1 mm of glass get about 25 rad. People can be shielded much better-- even huddling together has some value. About 500 rad is lethal, and the outer belt particles are less penetrating.
Cosmic radiation is relatively weak, and the moon provides little shielding.
The REAL danger is from eruptions on the Sun, which can flood interplanetary space with protons and ions that are quite energetic and penetrating. I believe Ben Bova had such an event in his book named (I think) "Mars", telling how astronauts on the way to Mars are hit by such an eruption and hide in a sheltered area aboard the spacecraft. This sort of risk is reduced around the minimum of the sunspot cycle, but it is never absent. In Earth orbit (e.g. on the space station) the Earth's magnetic field deflects such particles, at least from regions near the equator, where the space station is to be located.
30(c) Radiation hazard in space--3(Excerpt from question)
The other night, I was watching a program about the Apollo missions and how they might be a hoax staged by NASA. Many interesting points were raised and by apparently learned men. The point concerning me most was a claim that the craft used to travel to the moon, and the LEM that took them to its surface, would not have provided enough protection from the high levels of radiation in the VanAllen Belt and cosmic radiation traveling through the solar system. The man postulated it would take roughly three feet of lead to shield against such radiation. Can you tell me what material protection the crew members of the Apollo missions had or what measures were taken to protect them?
Excerpt from replyDear John
That program on TV created a flurry of inquiries--I think yours is 5th. ... The cosmic radiation in space might indeed take 3 feet of lead to reduce it significantly--which is about as much protection as the atmosphere gives us.
(By the way, a widespread misconception of the public is that lead makes a better shield than other materials. It does for x-rays, which is why dentists and doctors use lead aprons, etc. However, for high- energy particles of space, all substances are more or less equivalent, for the same amount of grams per square cm.)Keep in mind, though , cosmic radiation is a very weak source--it carries about as much energy as starlight. So the number of rads one gets from it is not high.
31. "Danger, falling satellites"?Hi
I am a writer, so my knowledge is always far behind the "truths" I write. But I was reading your article "Orbits", on the web, while researching a story I am writing, and liked the voice of your writing. So I thought I might ask you some questions. I hope you have the time.
I have searched extensively (without much luck) for information on the issues of reentry. I understand a layman's idea of how you get something into orbit and get it to stay there. I have also read about the demise of the Compton Observatory. Yet when I read about reentry, the issues of angle and speed are not clear.
If for instance a craft were out there going at 17500 mph and I just slowed it down to 60 mph--what would happen? Or if I just stopped it? Would it come crashing down like a lump and burn up along the way. Why does the shuttle enter the atmosphere at such speed and not just pop in with a large parachute? Perhaps it could use rockets to slow the gravity pull while it descends to an altitude where a parachute or simple gliding could be initiated without all that heat.
My problem in my story is that I need for a smallish satellite or vehicle (whatever) to be able to be descending into the atmosphere from orbit (in or out of control), fairly slowly (>400mph or thereabouts-- preferably, much less) between 60000 feet and the ground. Do I have a prayer - other than a Hollywood solution?
ReplyRe-entry from space is discussed in the middle of "Spaceflight" at http://www.phy6.org/stargaze/Spaccrft.htm
"If for instance a craft were out there going at 17500 mph and I just slowed it down to 60 mph--what would happen? Or if I just stopped it?"
You can't do so, no more than you can with your car: if it is going at 60 mph you cannot just slow it down to 10 mph, or to a stop, unless you apply the brakes. If you do that, the brake pads rub against the drums or disks and convert the energy of the car into heat.
The speed of an orbiting object is enormous, and it too must be dissipated as heat: re-entering at a shallow angle lengthens the time spent in re-entry, so the heat is generated more gradually and can be radiated away without the spacecraft getting too hot. A small satellite can survive it, if suitably protected or if lucky enough: in the 1960s, USAF airplanes retrieved film packages from spy satellites, ejected in well-protected (but relatively small) capsules. When such satellites reach the denser atmosphere, they slow down--perhaps to 150 mph or less. The film capsules would then deploy a parachute, and as they floated down, a twin-boom transport airplane, with rear door open, would trail a line with a hook, snag them and pull them in. If they were to hit the ground (in principle--actually, rerieval was usually above water) they would of course get banged up somewhat, but their instruments etc. could perhaps survive.
Further message (shortened)My story (a screenplay) which is more a people story than a James Bond, envolves a collision between a malfunctioning runaway satellite and a Boeing 767.
Reply (shortened)A film capsule of (say) 10 or 20 kg would be less likely to demolish a 747 in full flight. Still, I would not like to be aboard that plane! It is not the 150 mph (or whatever) of the capsule, but the 600 mph of the airplane, which makes the collision so dangerous. If it hit the main body of the airplane, or a wing, results could be grim. If it hit a jet engine, it would probably demolish it. The satellite itself or the capsule would have a parachute deploy to slow it to much less than 150 mph.
The nearest thing I can recall is an airliner flying over Damascus, Syria, during one of the tense periods between Syria and Israel. The Syrians fired a missile at it, and by some miracle it stuck in a wing and did not explode. The airplane landed safely, but it was a close call.
32. The Lagrangian L3 pointHello
I went through the site at: http://www.phy6.org/Education/wlagran.html and was just wondering if there is any information on L3? As I read the article I may have missed its mention. If not could you tell me if there is any information you could point me towards?
Thanks Very Kindly
The Lagrangian point L3 is not mentioned because it is only of theoretical interest and has no practical application. If only Earth and Sun existed, L3 would be on the Earth-Sun line, but on the opposite side of the Sun. At that distance, a satellite at exactly 1 AU (Astronomical Unit = Sun-Earth distance) would experience a bit more gravity than the Earth, being pulled not just by the Sun but also by the Earth. Its orbital period would therefore be a tiny bit less than a year. L3 is at a slightly larger distance, where the greater distance from the Sun reduces the Sun's pull just enough to make the satellite's orbital period exactly one year, so that it would keep a fixed position relative to the Earth.
Practically, the feeble pull of the Earth at this distance is negligible compared to other effects, such as the attraction of Jupiter. Besides, it would be hard to communicate to such a spacecraft, since it would be permanently behind the Sun!
Look also at "From Stargazers to Starships", home page at http://www.phy6.org/stargaze/Sintro.htm. Sections 34 there calculate the Lagrangian points.
33. Distance to the Horizon on an AsteroidHi,
The reason I stumbled across your page is that I work on astronomical, science fiction and fantasy art and illustration and was looking for a formula that would allow me to calculate the distance to the horizon of any body once one knows the radius of that body. I've been working up a piece illustrating a scene taking place on Ceres and it would be nice to have the horizon more or less where it ought to be.
Any suggestions where I might find such a tool?
ReplyFor the distance to the horizon, look up the formula in "From Stargazers to Starships", sect. 8a (where it is derived). It depends on your elevation, of course. All you need is replace the radius R of Earth by that of Ceres, assumed to be spherical.
There is a great story by Arthur Clarke, "Hide and Seek," in which a man in a spacesuit successfully evades a spaceship on a moon of Mars, where the horizon is quite close. Have you read it?
34. Overtaking Planets
Hi - I am looking for the way of calculating orbits of two planets passing each other.
The two passed each other in 1982. What would be the calculation for determining when the two will pass each other again, in layman terms?
Trying to answer this for a grade school student - trying to assist.
Your example does not sound too practical--it's like asking when does Jupiter overtake Neptune, even at the closest approach they are still very far apart. So let me reformulate
Its frequency is 1/1.8822 = 0.5313 rev/year
At some time (say, today) Earth passes closest to Mars. When will it happen again?
Draw the two orbits, one inside the other. Then assume you put the whole set-up on a turntable, rotating with a frequency –1, that is that is, 1 revolution per year but in the opposite sense. Forces in the rotating frame would be quite different, but we ignore that--the motions alone are what counts here.
Frequencies add up, rotation periods don't. The orbital frequency of Earth in the rotating frame is 1 – 1 = 0 revolutions/year, that is, it does not move. That of Mars is 0.5313 – 1 = –0.4687 rev per hear, in the opposite direction, which make sense--the Earth moves faster, Mars viewed from it moves backwards. Its period T' will be, in the frame where the Earth sits still
That's you answer. You can use 12 and 30 years, if you wish, the same way.
35. Falling Towards the SunIn doing research on a recently retired Pelton Wheel, I found your article on the Pelton Wheel and its implications for NASA's Solar Probe. Not being a physicist, I want to verify that I'm interpreting one section of the article correctly:
"...the most economical way of achieving that mission...may well be sending the spacecraft towards Jupiter....It would then make a tight loop around the planet, overtaking it in such a way that practically all its orbital velocity around the Sun is lost, and then fall toward the Sun. "
"Falling toward the sun"...I'm having difficulty visualizing this. Is it similar to the slingshot effect used to get Apollo 13 home? Would that be a grossly incorrect description? If so, could you offer a short, simple lay person description? I'm writing for a power industry internal newsletter and cannot get overly technical.
"A little knowledge is a dangerous thing. " I would guess that you reached my Pelton wheel site using a search engine, and did not note it was unit #35a--the last unit, in fact--of a big educational site about spaceflight, astronomy and physics. You can reach the home page from the "back to index" button on the bottom, and after you do that, go to the preceding unit #35 where gravity-assist orbital maneuvers are discussed. Even though the spacecraft and moving planet (or moving moon) never touch, the result is similar to an elastic collision. Just as Sammy Sosa's home runs are a combined product of the speed imparted by the pitcher and that of the bat, so it was for Voyager 2 and Jupiter, for instance.
It works both ways: head-on collisions gain energy, overtaking ones give it up. Usually in space we want an extra boost, but in a turbine we want the water to lose as much as possible, because by the conservation of energy, what is lost from the water jet is gained by the water wheel. To hit the Sun with a spacecraft, it's not enough to escape the Earth's gravity: do that and you are still circling the Sun, like the Earth, with the same velocity, 30 km/sec. To give up as much is just as hard as gaining an equal amount--which is more than what is needed to escape the solar system altogether.
I am not sure change of velocity was a consideration with Apollo 13, as much as hitting the Earth edge on, so that the spacecraft would be braked by the high atmosphere. Hit any lower and it would hit the Earth (and burn up before doing so), hit any higher and you miss the Earth, go out to space, and long before you are back for another try you have run out of oxygen.
36. The Polar Bear
Could you please assist me with an estimation of the energy absorbed from the sun at the arctic (polar) regions? I would also like to know, if possible, the amount of energy (in Joules or calories) that a polar bear needs for a day. Thanks in anticipation.
The polar bear is unawareHilaire Belloc
Your request is one of the strangest I have ever received--do my correspondents feel that NASA knows everything? What is this information intended for?
About the polar bear: I will make a wild guess, 60,000 calories/day. But I really do not know. However a book exists which probably contains the answer, "The Fats of Life" by Caroline Pond. I saw its review in the "New Scientist" supplement of 6 May 1999, the review talks about the bear's metabolism but does not count calories.
The amount of sunlight at the pole depends on season. At the pole, in midwinter it is of course zero, in midsummer (clear sky) I would guess about 0.3-0.4 Kw/sec sq. meter, of which I suspect most is reflected by the ice.
37. Are the Sun's Rays Parallel?David--thanks for your article. Can you tell me: Are the suns rays parallel ?
What a question! Some are, most are not--but the answer depends on what you plan to do with the information.
The Sun covers about half a degree of the sky. So rays that come from opposite edges of the Sun have directions which differ by half a degree and are not parallel.
Rays which reach your left and right eye from a distant star, on the other hand, are very close to parallel--they may meet somewhere at the star, at the same point (and then they converge) or separated points (and then they probably diverge), but the eye and even the the telescope cannot resolve such details.
Rays from the same point on the Sun are pretty much like those from a star. But again, "same point" is hard to pin down--even sunspots may be thousands of kilometers wide.
ResponseThanks yet again. The question echoed what I remember being taught at school. Dont ask in which discipline. I can remember only the statement.
The reason I needed confirmation or refutation is simple. My hubbie has been observing the shadow cast by the sun on our south facing balcony railing at a specific time of day. One of his statements showed that he felt the sun's rays radiate ! I disagreed both with his conclusions and his statement.
You're a star for answering so clearly and quickly and leaving both of us room to be right. Is psychology your second area of specialization ?
38. More thrust in reverse than going forward?(shortened) Sir,
I was struck by the visual similarity between a Pelton bucket and the split "clamshell" type of thrust reverser on jet aircraft. By an impulse analysis I estimate that the rearward thrust is about 157% of the forward. Is this about right?
I did not understand all you wrote, but please remember the zeroth law of thermodynamics, "there ain't such a thing as a free lunch. "
I don't believe a clamshell thrust reverser can generate more thrust forwards than backwards! There is a fine question of energy, which goes as the square of the velocity--but thrust is momentum transferred, and shooting a mass m with velocity v forward or backwards gives momentum + mv or - mv. In a Pelton wheel, the buckets move relative to the jet, but in a jet-engine clamshell they don't--so they can deflect, but not add any energy.
39. The varying distance between Earth and SunHi
Sorry to be taking up your time, you are without a doubt very busy with answering many questions, but I am a 7th grader in View Ridge doing a report on "distance from the earth to the sun at 1 day from all 12 months." After searching for 3 hours I could not find this data and I thought maybe you could direct me on how and where to find this data or maybe you could send the data to me if it is easily accessible to you. Well thanks for your time and reading this message.
I am not at all sure what your teacher is asking, or why--or what you are supposed to learn from it all. The mean distance of Earth from the Sun is the astronomical unit (AU), equal according to my handbook to 149,599,000 kilometers.
From the nautical almanac; the Sun's distance on day N of the year in AU is
A formula exists for finding N based on the way astronomers count days, but I suspect counting from January 1 is OK, because then R is smallest around January 3, which is indeed well known. Being in 7th grade, do you know what a cosine is? If not, look up in the mathematical section of "Stargazers".
40. Mission to MarsI am a professor in a large university and teach interdisciplinary general education courses. After reading this month's Scientific American [March 2000], I have been thinking about alternative scenarios for Mars missions.
The question is:
Suppose the total mass of the mission payload is Mp, and the total mass of the launch vehicle plus propellant is Mt. How does Mt scale with respect to Mp? If
REPLYDear Richardt I suspect that a=1 after all. If you want to send twice the payload, you need a rocket twice as large. There exist no economies of scale.
There does exist a certain flexibility in K, however. You do have to escape the Earth's gravity, at least to a circular parking orbit, and this sets a lower limit to K--it depends on your fuel, and the staging of the rocket, but it is going to be around 20 or more, usually more.
To fly from there to Mars, all sorts of tricks can be employed--ion engines, solar sails, etc.--and the duration of the trip is also a variable. Finally, the spaceship is to stop at Mars, not fly past it, and that requires either extra thrust or some delicate aerobraking. I think the article goes into all this, but the bottom line is--it isn't easy, and would take both ingenuity and luck to be pulled off successfully.
41. Kepler's calculationI've been searching for a book that would show me how to re-enact what Kepler did, with Brahe's data. That is, I want to use my 4 inch telescope and my accurate clock to record data that I can use to show that the data fits an ellipse. Where can I find instructions on how to collect the data and where can I find the equations Kepler used to show that the data fit?
I found your web page course "From Stargazers to Starships" and thought you might know what I am looking for specifically.
Thank you for any suggestions.
Tycho Brahe had no telescope, you know, but he built some very accurate quadrants--instruments resembling giant protractors, with sights to line up with stars. With these he tracked the positions of stars very accurately, taking into account factors such as refraction of light in the atmosphere. Kepler's laws were essentially based on the observations of Mars alone. A 4-inch telescope can be aimed much more accurately (the eye has a resolution around a minute of arc, at most), but this does not help much in precise tracking, unless you can determine with equal precision the direction in which it is pointing. That probably needs a strong foundation and accurate and strong mounting.
That, however, need not be not your problem. You can always "fake your data" and take positions of Mars from the ephemeris table of the astronomical (or nautical?) almanac. Amateur astronomers in your area will have it, also university libraries--you might even find it on the web, I have not looked.
The question is, however, what then? To check the position of Mars in the sky, you need track both Earth and Mars. I don't know if motion of the Earth in a circle around the Sun (the idea of Copernicus) is good enough, but you can try it for a start. In fact, try the same for Mars, too, using the proper orbital period for each: you will get retrograde motion, though positions will not agree exactly.
To check the uneven motion of Mars is harder. You must draw its ellipse (not accurately--only the calculation needs to be accurate) and mark on it a large number of points, say 36. Using the equation of the ellipse (and you will also need the eccentricity of that ellipse-something Kepler had to find out the hard way), calculate for each point its distance from the Sun (a computer will help). Also calculate the area covered by each 10-degree pie slice, approximating each slice by a triangle, and then from the law of areas you get the time needed to cover that angle, in some arbitrary units. Those units can be found by noting that all the times must add up to one orbital period. Of course, you must also know in which direction apogee is, the greatest distance from the Sun.
If you now mark 72 positions of the Earth on its orbital circle over 2 years (about one Mars year), each will have its date. For the same date, you can estimate the position of Mars from your 36 points, each of which also has a date, and get the direction to Mars. Oh well--you may need 3-dimensional geometry, because the positions in the Almanac are probably not in ecliptic coordinates (Mars and Earth both move near the plane of the ecliptic) but in declination and right ascension. You can see it will be a big job.
I do not know how Kepler's calculated all this (it took him years). The position of Mars in the sky (as you can see above) involves BOTH Kepler's first and second laws. My GUESS (just a guess, I may be wrong) is that he assumed the Earth moved in a circle, and that Mars moved in a circle too (he knew the periods of both from long-term observations). He then assumed (like Copernicus) that both moved at constant rates around those circles, and found (as you might--see above) that the positions did not fit. He then MAY have assumed that the position of the Sun was some distance from the center of the circle of Mars, and found in that case that the law of areas could explain most irregularities. FINALLY, he had to give some logical reason for the displacement of the Sun from the center of the orbit, and the most elegant idea he could find was that the orbit was an ellipse and the Sun was at one focus.
I vaguely recall that the book "The Sleepwalkers" by Arthur Koestler describes those years in Kepler's life, and maybe you will find some clues there. Be warned, though--that is a work of literature by a writer not familiar with math. Maybe you can then write me what you found.
42. The Appearance (Phase) of the MoonWhat did the moon look like in Richmond, VA from February 28 to March 8, 2001? For example: full moon, crescent, etc.
First of all--the moon looks pretty much the same from anywhere on Earth, at least its light-shadow phase-Richmond or Los Angeles, there is no big difference. The direction in which the light-dark division points may differ, because while the moon seen from Australia and here is pretty much the same, the "up" direction in which our heads point is not.
To find the phases of the moon, you might consult an almanac. Or else, you might look up the Jewish date, listed on a number of sites. The Jewish calendar (actually taken from ancient Babylon) has every month beginning with the new moon--the time the moon passes the sun in its trip around the sky (and is not seen). A day or so later it is a very thin crescent setting just after the sun does. In the days that follow that crescent gets wider and wider, and the Moon sets about an hour later every night.
About a week after new moon you get a half moon, after that it is "gibbous" and in mid month, around the 14th on the Jewish calendar, you get a full moon rising just when the sun sets. To see the moon during the last week of the Jewish month you must be up pretty late, and you will see a half moon or crescent moon in the east lit up from below, from where the sun will rise some hours later.
On the Jewish Calendar, February 28 is Adar 5, giving a crescent Moon; March 8 is Adar 13, with the moon nearly full. The month of Adar has 29 days. Be warned that you may be a day off--the Jewish calendar sometimes adds a day to make sure certain holidays fall on a proper day of the week. For abolute accuracy, use an almanac.
Hoping this answers all your questions
Dr. David P. Stern
Goddard Space Flight Center
Go to main list of questions (by topic) | 0.890919 | 3.577035 |
A team of astronomers made an important discovery with the Hubble Space Telescope, detecting helium in the atmosphere of exoplanet WASP-107b. This marks the first time researchers have found signs of the element in a planet beyond our solar system, and could also mean that scientists can study the composition of the air in exoplanets without having to wait for another space telescope to be launched for such a purpose.
According to a news release published by the European Space Agency, the multinational team made the discovery with Hubble’s Wide Field Camera 3, using the instrument to detect helium in WASP-107b’s atmosphere. The researchers consider this finding important, as helium ranks behind hydrogen as the universe’s second-most common element, and had never been confirmed to exist on exoplanets.
WASP-107b is located about 200 light-years away from Earth in the constellation Virgo, and is described as a “super-Neptune” exoplanet, one that has a similar diameter to Jupiter, but only one-eighth of the planet’s mass. Space.com observed that this makes it one of the lowest-density planets known to astronomers. The exoplanet also takes only 5.7 days to orbit its host star, and its atmosphere is definitely not conducive to life as we know it, with temperatures of 932 degrees Fahrenheit, or 500 degrees Celsius.
In an email to Space.com, University of Exeter researcher and study lead author Jessica Spake explained that her team used new methodologies to study the radiation-heavy upper reaches of an exoplanet’s atmosphere. The team’s findings were published Wednesday in the journal Nature.
“Hopefully, we’ll be able to study many more upper planetary atmospheres this way,” Spake added.
Both Space.com and the ESA press release explained the methodologies Spake and her colleagues utilized, which included studying the infrared spectrum of WASP-107b’s atmosphere. Prior to the new study, analyses of exoplanet atmospheres involved ultraviolet light, which is mostly blocked out by Earth’s atmosphere. That’s not the case with infrared radiation, which can be detected by ground-based telescopes, as it passes through Earth’s atmosphere, including its air and clouds. Furthermore, Spake noted that ultraviolet analysis only works with nearby exoplanets, but not more distant ones like WASP-107b.
“The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmospheres in a wider range of planets.”
Hubble has been used to detect helium in the atmosphere for 1st time ever on a world outside of our solar system! Exoplanet WASP-107b is 1 of the lowest density planets known. While it is about the same size as Jupiter, it has only 12% of Jupiter’s mass: https://t.co/9ngmXQdfeW pic.twitter.com/S8BPXdMHUr— Hubble (@NASAHubble) May 2, 2018
Aside from the Hubble Space Telescope, astronomers might have another valuable resource available in the next few years for analyzing the atmosphere of exoplanets like WASP-107b. According to Spake, there’s a good chance that NASA’s James Webb Space Telescope, which is now expected to launch in May 2020, will be able to make these detections. Additionally, there are several ground-based telescopes, including Hawaii’s Keck Telescope and the European Southern Observatory’s Very Large Telescopes, that might be capable of consistent observations of exoplanet atmospheres. | 0.878491 | 3.855158 |
On Pluto And Charon, Evidence For A Kinder, Gentler Kuiper Belt
A belt of ice and rock beyond Neptune could retain traces of our solar system's formative years, but most of its objects are too distant, and too small, to observe from Earth.
Now, a novel approach uses data from the New Horizons spacecraft to fill in the blanks.
The study appears in the journal "Science."
Like spymasters inferring troop actions from satellite photos, astronomers have used images of craters on Pluto and its moon Charon to estimate activity in the Kuiper Belt, of which they are a part.
Different models of how the belt formed predict either energetic smashing — which would blast away more small objects, like space shrapnel — or a more pristine, peaceful dance governed by milder interactions.
Either answer would offer essential insights into the formation and history of our solar system. Such information could also inform our understanding of planetary formation around distant stars.
After accounting for geological processes that might have resurfaced the dwarf planet and its moon, the scientists found a relative lack of small craters (measuring less than around 8 miles, or 13 kilometers). This, in turn, suggests a lack of small Kuiper belt objects.
"The surprising result was that there aren't that many small craters on Charon. There's a real deficit of little guys, and that translates to a deficit of little objects in the Kuiper Belt," said co-author Will Grundy of Lowell Observatory, who also serves on the New Horizons team.
That suggests fewer collisions, which could explain why delicate arrangements such as binary systems survive in the belt.
New Horizons flew by Pluto and its five moons — Charon, Nix, Hydra, Kerberos and Styx — on July 14, 2015. Last month, it surveyed the most distant object ever explored: the peanut-like Kuiper Belt body 2014 MU69, informally nicknamed Ultima Thule. | 0.862428 | 3.784828 |
There are always lots of things happening in astronomy. Here are some anticipated highlights for 2013.
In the Sky
On 28 April 2013 the planet Saturn will be at opposition – the closest approach that the ringed planet makes to us during the mutual orbits of earth and Saturn. Will be the best time during the year to look at Saturn with a telescope. There’s also a partial (“penumbral”) lunar eclipse on the 18th of October, which might be visible in Ontario.
Nice meteor showers show up every year, assuming that the weather cooperates. Here are some of the more prominent ones:
- Just after New Year, on January 3-4, the Quadrantids Meteor Shower is at its peak. A dark location after midnight is recommended; find the constellation Bootes to find the expected radiant point.
- In August, the Perseids Meteor Shower presents its peak on the 12th and the 13th. This is always a favourite meteor shower, with as many as 60 meteors per hour showing up.
- November has the Leonids Meteor Shower, peaking on the 17th and 18th. This shower looks like it’s originating in the constellation Leo, and will be best viewed after midnight.
- In December, weather permitting, the Geminids Meteor Shower has its peak December 13-14. Best viewing will be after midnight, in the east.
Perhaps the most anticipated sights in 2013 are two comets expected to make interesting – and possibly spectacular – shows. Comet 2014 L4 (PanSTARRS) is currently being watched by astronomers in the southern hemisphere, but by March it should reach its greatest brightness and be visible up here in the north (http://cometography.com/lcomets/2011l4.html). 2014 L4 (PanSTARRS) is predicted to peak at a magnitude near -0.5 between 8-12 March 2013 (like a very bright star). Like the vast majority of comets, it will come no where near to the earth, never getting any closer than 0.3 AU – a third of the distance from the earth to the sun. By late May it should be very high in the night sky in the north – perhaps 5 degrees from Polaris – but will be much fainter too.
Also eagerly anticipated is Comet C/2012 S1 (ISON), (http://cometography.com/lcomets/2012s1.html). It was discovered this past September and might (emphasis might) be one of the greatest comets of recent memory. It will dip very close to the sun – about 0.1 AU or one tenth of the way from the earth to the sun – and may reach its maximum brightness on 28 November 2013. While very hard to predict, the size and orbit of the comet has some astronomers predicting a magnitude (brightness) of -13 for this beast. That’s brighter than the full moon! It may also have a very long tail. As comets are best described as irregular, big dirty snowballs, just how they behave when the sun starts to heat them up and generate their tails and other features is impossible to predict with precision. I’ll post updates (as will everyone interested in the sky, I’m sure!) as they become available.
(source of 17th C. illustration: http://ksj.mit.edu/tracker/2012/10/kehouflop-redux-out-near-saturn-monster).
On the Ground
This year the Hamilton Amateur Astronomers is hosting ASTROCATS 2013: The Canadian Astronomy Telescope Show, May 25th & 26th at the Sheridan College Athletics Centre, Oakville, Ontario. Unfortunately yours truly can’t attend, but it should be a great show, with a lot of vendors representing the best in astronomy gear (come to think of it, it’s likely a GOOD THING I can’t go. The national debt couldn’t take the strain): http://astrocats.ca/.
SkyFest is the annual three-day event put on by the North York Astronomical Association. August 8-11, 2013, held at River Place Park, RR 3, Ayton, Ontario (northwest of Mount Forest). It’s Canada’s biggest star party: http://www.nyaa.ca/index.php?page=/sf13/sf.home13. | 0.909993 | 3.344668 |
Bakersfield Night Sky – October 7, 2017
By Nick Strobel
One of the challenges in writing this column is choosing which astronomy news to write about from the many cool astronomy news stories arriving in my inbox every week. Unfortunately, you’re stuck with my preferences. For this column my preferences for Mars and black holes come to the fore.
In a news release from last week was an early analysis of the effect of the powerful solar eruption on September 11 on Mars as seen by the MAVEN orbiter and the Curiosity rover on the surface. The blast from the sun reached Mars about two days later and created a global aurora more than 25 times brighter in the ultraviolet than any seen before. An aurora on Mars covers the entire planet instead of being concentrated near the magnetic poles like on Earth because Mars doesn’t have a strong magnetic field. Due to its smaller size, Mars’s metal core cooled more quickly than Earth’s. As Mars’s core solidified, the global magnetic field disappeared. The loss of that protective magnetic force field left its atmosphere prey to the solar wind and solar eruptions and its atmosphere was whittled away over millions of years.
The Curiosity rover has an instrument that measured the radiation levels on its seven-month journey to Mars and has been steadily monitoring the radiation environment on the surface of Mars for the past five years. The blast from the sun produced radiation levels on the surface more than double any previously measured and those high readings lasted more than two days. Our thick atmosphere and substantial magnetic field protect us from all that nasty radiation but human Mars explorers are going to have to keep close tabs on the outbursts from the sun. They will have two types of weather forecasts to read about at breakfast: martian weather and space weather.
In another news release about Mars last week was about the possibility of more ice near the Martian equator than originally thought. New data processing techniques on old data from the Mars Odyssey spacecraft still orbiting Mars have increased the spatial resolution by a factor of two. That means it made the old observations twice as sharp.
The new analysis shows that there are concentrations of water ice closer to the equator where conditions would be less harsh for human Mars explorers than higher latitudes. The more water we find on Mars, the less water we have to bring from Earth for human exploration. Besides using the water for our biological needs, the water can be broken apart to produce the oxygen we need to breathe and the hydrogen can be used as fuel.
Now for two black holes news stories. The first black holes story is about a possible way to create the supermassive black holes (ones that are millions to billions of times more massive than stars) we see at the centers of most galaxies. One major mystery in the field of supermassive black hole research is how to form the very big ones we see in galaxies when the universe was very young.
The two possible ways to make supermassive black holes each have their shortcomings. The first way involves multiple mergers of ever larger black holes. However, when you run through the calculations of how many mergers it would take to build up a supermassive black hole in the short time periods we see, the rate is unreasonably high.
Another proposed method for making supermassive black holes involves the direct collapse of huge gas clouds into huge black holes “seeds”. The problem with that method is how to avoid the collapsing gas cloud fragmenting to form stars. A new set of computer simulations shows that supersonic flows when the universe was still a hot plasma soup in the first few hundred thousand years after the Big Bang could do the trick. The dark matter would have clumped more than the ordinary matter in that early universe to form the seeds of big black holes. The ordinary matter would have flowed into those dark matter clumps instead of forming stars. The search is on to see if we can find proof of these black hole seeds.
The second black hole story is about the detection of gravitational waves from the merger of two large black holes of mass 31 and 25 times the sun into a single black hole 53 times the mass of the sun. The math is correct because three solar masses were radiated away in the form of spacetime ripples. Although gravitational waves have been detected before, this detection was the first one by THREE detectors and the first one by the Virgo detector in Europe. The earlier detections were made by the two LIGO detectors in the U.S.
Having three detectors enabled us to more accurately determine the location of the merger to ten times better than the previous observations. The black holes involved in all of the gravitational wave detections so far are several times heavier than ordinary stellar mass black holes.
In two weeks will be the showing of the popular “Black Holes” show at the William M Thomas Planetarium on October 19. Toward the end of that show we see what it would look like inside the supermassive black hole at the center of our home galaxy. Tickets are available from the BC Ticket Office and online from Vallitix.
What's up in the evening and early pre-dawn morning are shown in the star charts below. At 9 p.m. the waning gibbous moon will be just beginning to rise in the east. By that time, Saturn may be getting lost in the muck of our dirty air close to the horizon (see the first chart below). It and the brighter part of Sagittarius called the "Teapot" will be lost in the glare of Bakersfield's light pollution. The Summer Triangle will be high overhead. Early risers will be able to see Venus and Mars low in the east just before sunrise (see the second chart below).
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com | 0.878042 | 3.208656 |
Image: Courtesy of ELIZABETH TURTLE/University of Arizona
Just how thick the layer of ice covering the surface of Jupiter's moon Europa is lies at the center of an ongoing scientific debate. Current theory holds that the icy layer covers a huge liquid ocean, so its thickness holds import for possible Europan oceanic explorations in the future. But estimates of the ice breadth have ranged from merely one or two kilometers to upwards of 30. Now new research, published in the current issue of Science, provides support for an intermediate thickness of at least three to four kilometers.
To investigate the thickness of the ice layer, Elizabeth Turtle and Elisabetta Peirazzo of the University of Arizona's Lunar and Planetary Laboratory exploited impact craters on Europa's surface. The scientists modeled the impact of comets into a layer of ice overlying liquid water and compared the results to six actual Europan craters imaged by Galileo and Voyager that exhibit central peaks (see image). As Turtle explains, because "central peaks are deep material that's been uplifted, that means these impacts could not have penetrated through Europan ice to water. Water would not have been able to form and maintain a central peak." The authors thus conclude that the ice shell must have been greater than three to four kilometers deep. They stress, however, that their observation can only be interpreted as a lower limit. | 0.855283 | 3.65529 |
- When the sun enters its red giant stage in about six billion years, scientists say it will cause a chain reaction of exploding asteroids in the asteroid belt.
- These small rocky bodies will explode thanks to the YORP effect, a phenomenon in which the sun's radiation causes rapid changes to the rotation of asteroids.
- After the sun expands into its red giant stage, it will shrink into a white dwarf.
Between five and six billion years from now, astronomers say the sun will expand into an even bigger fireball, swallowing almost half the solar system. This rapid expansion into its red giant stage is likely to send asteroids in the asteroid belt between Mars and Jupiter tumbling.
You can thank the YORP effect. Stars emit infrared radiation into space, which carries momentum in addition to heat and can change the orbit—a phenomenon called the Yarkovsky effect—as well as the rotation and orientation of nearby small bodies such as asteroids. The YORP effect, named for the four scientists who contributed to its discovery—Yarkovsky, O’Keefe, Radzievskii, and Paddack—was directly observed in 2007, when scientists noticed the asteroid 54509’s YORP rotation changed.
Asteroids that absorb this momentum-packed sunlight eventually re-radiate it back out into space as heat, which creates small amounts of thrust, thus inching the rocky bodies from their original path or causing them to spin faster and faster. Because most asteroids are "rubble piles"—loosely packed blobs of dust, rock and ice—many won't be able to withstand the forces of this increased rotation and will shatter, flinging rocky debris far out into the solar system.
Stars undergo several important stages before they eventually die. Our sun, a yellow dwarf, is currently in the main sequence stage of its life. Right now, the heat the sun radiates doesn’t have much of an influence on the rocky bodies in the asteroid. But that could change when our sun begins to expand out into the solar system.
“When a typical star reaches the giant branch stage, its luminosity reaches a maximum of between 1,000 and 10,000 times the luminosity of our sun.” astrophysicist Dimitri Veras, of the University of Warwick in England, said in a statement. “The YORP effect in these systems is very violent and acts quickly, on the order of a million years.” Veras leads a team of researchers who published this research last year in the Monthly Notices of the Royal Astronomical Society.
After the branch stage, our shiny neighbor will eventually shrink back down into a super-hot, super-dense, Earth-sized white dwarf. The rocky debris created in this violent event will begin to form a disc around the star, and then eventually get sucked in.
By then, the damage will have already been done. “Not only will our own asteroid belt be destroyed,” Veras said, “but it will be done quickly and violently. And due solely to the light from our sun.” | 0.848679 | 3.972103 |
Global extinction and geological events have previously been linked with galactic events such as spiral arm crossings and galactic plane oscillation. The expectation that these are repeating predictable events has led to studies of periodicity in a wide set of biological, geological and climatic phenomena. Using data on carbon isotope excursions, large igneous provinces and impact craters, we identify three time zones of high geological activity which relate to the timings of the passage of the Solar System through the spiral arms. These zones are shown to include a significantly large proportion of high extinction periods. The mass extinction events at the ends of the Ordovician, Permian and Cretaceous occur in the first zone, which contains the predicted midpoints of the spiral arms. The start of the Cambrian, end of the Devonian and end of the Triassic occur in the second zone. The pattern of extinction timing in relation to spiral arm structure is supported by the positions of the superchrons and the predicted speed of the spiral arms. The passage times through an arm are simple multiples of published results on impact and fossil record periodicity and galactic plane half-periods. The total estimated passage time through four arms is 703.8 Myr. The repetition of extinction events at the same points in different spiral arm crossings suggests a common underlying galactic cause of mass extinctions, mediated through galactic effects on geological, solar and extra-solar processes. The two largest impact craters (Sudbury and Vredefort), predicted to have occurred during the early part of the first zone, extend the possible pattern to more than 2000 million years ago. | 0.813286 | 3.104658 |
These images show evidence from NASA's Chandra X-ray Observatory that the black hole in the galaxy Messier 87 (M87) is blasting particles out at over 99% the speed of light, as described in our latest press release. While astronomers have observed features in the M87 jet blasting away from its black hole this quickly at radio and optical wavelengths for many years, this provides the strongest evidence yet that actual particles are travelling this fast. Astronomers required the sharp X-ray vision from Chandra in order to make these precise measurements.
Using NASA's Chandra X-ray Observatory, astronomers have seen that the famous giant black hole in Messier 87 is propelling particles at speeds greater than 99% of the speed of light.
The Event Horizon Telescope Collaboration released the first image of a black hole with observations of the massive, dark object at the center of Messier 87, or M87, last April. This black hole has a mass of about 6.5 billion times that of the Sun and is located about 55 million light-years from Earth. The black hole has been called M87* by astronomers and has recently been given the Hawaiian name of "Powehi."
For years, astronomers have observed radiation from a jet of high energy particles - powered by the black hole - blasting out of the center of M87. They have studied the jet in radio, optical, and X-ray light, including with Chandra. And now by using Chandra observations, researchers have seen that sections of the jet are moving at nearly the speed of light.
"This is the first time such extreme speeds by a black hole's jet have been recorded using X-ray data," said Ralph Kraft of the Center of Astrophysics | Harvard and Smithsonian (CfA) in Cambridge, Mass., who presented the study at the American Astronomical Society meeting in Honolulu, Hawaii. "We needed the sharp X-ray vision of Chandra to make these measurements."
When matter gets close enough to a black hole, it enters into a swirling pattern called an accretion disk. Some material from the inner part of the accretion disk falls onto the black hole and some of it is redirected away from the black hole in the form of narrow beams, or jets, of material along magnetic field lines. Because this infall process is irregular, the jets are made of clumps or knots that can sometimes be identified with Chandra and other telescopes
The researchers used Chandra observations from 2012 and 2017 to track the motion of two X-ray knots located within the jet about 900 and 2,500 light-years away from the black hole. The X-ray data show motion with apparent speeds of 6.3 times the speed of light for the X-ray knot closer to the black hole and 2.4 times the speed of light for the other.
"One of the unbreakable laws of physics is that nothing can move faster than the speed of light," said co-author Brad Snios, also of the CfA. "We haven't broken physics, but we have found an example of an amazing phenomenon called superluminal motion."
Superluminal motion occurs when objects are traveling close to the speed of light along a direction that is close to our line of sight. The jet travels almost as quickly towards us as the light it generates, giving the illusion that the jet's motion is much more rapid than the speed of light. In the case of M87*, the jet is pointing close to our direction, resulting in these exotic apparent speeds.
Astronomers have previously seen such motion in M87*'s jet at radio and optical wavelengths, but they have not been able to definitively show that matter in the jet is moving at very close to the speed of light. For example, the moving features could be a wave or a shock, similar to a sonic boom from a supersonic plane, rather than tracing the motions of matter.
This latest result shows the ability of X-rays to act as an accurate cosmic speed gun. The team observed that the feature moving with an apparent speed of 6.3 times the speed of light also faded by over 70% between 2012 and 2017. This fading was likely caused by particles' loss of energy due to the radiation produced as they spiral around a magnetic field. For this to occur the team must be seeing X-rays from the same particles at both times, and not a moving wave.
"Our work gives the strongest evidence yet that particles in M87*'s jet are actually traveling at close to the cosmic speed limit," said Snios.
The Chandra data are an excellent complement to the EHT data. The size of the ring around the black hole seen with the Event Horizon Telescope is about a hundred million times smaller than the size of the jet seen with Chandra.
Another difference is that the EHT observed M87 over six days in April 2017, giving a recent snapshot of the black hole. The Chandra observations investigate ejected material within the jet that was launched from the black hole hundreds and thousands of years earlier.
"It's like the Event Horizon Telescope is giving a close-up view of a rocket launcher," said the CfA's Paul Nulsen, another co-author of the study, "and Chandra is showing us the rockets in flight." | 0.858638 | 4.012315 |
This imposing constellation of the zodiac lies between Aries and Gemini. It represents the bull into which the Greek god Zeus transformed himself to abduct Princess Europa of Phoenicia. Zeus then swam to Crete with the princess on his back. The constellation represents the front half of the bull's body - the part visible above the Mediterranean waves. It contains two major star clusters, the Pleiades and Hyades. In mythology, the Pleiades were the seven daughters of Atlas and Pleione, and the cluster is also known as the Seven Sisters; the Hyades were the daughters of Atlas and Aethra. In the sky, the Hyades cluster marks the bull's face, while the red giant star Aldebaran forms the creature's bloodshot eye. The tips of the bull's horns are marked by Beta and Zeta Tauri, magnitudes 1.7 and 3.0. The Sun passes through Taurus from May 14th to June 21st..
Points of Interest
Alpha Tauri (Aldebaran)
A red giant star that varies irregularly in brightness between magnitudes 0.75 and 0.95. Although it appears to be a member of the Hyades cluster, it is actually much close to us, being 65 light-years away.
M1 (The Crab Nebula)
The remains of a supernova that was seen from Earth in AD 1054. Under excellent conditions it can be found with binoculars or a mall telescope, but a moderate aperture is needed to see it well. It is elliptical in shape, appearing midway in size between the disk of a planet and the full Moon. It lies about 6,500 light-years away.
A wide double star in the Hyades cluster. Observers with good eyesight can divide the two stars with the naked eye. Theta-1 is a yellow giant, magnitude 3.8; Theta-2 is a white giant of magnitude 3.4, the brightest member of the Hyades.
An eclipsing binary star of the same type as Algol. It ranges between magnitudes 3.4 and 3.9 in a cycle lasting under 4 days. | 0.823677 | 3.030703 |
NEAR Shoemaker was the first spacecraft to orbit around an asteroid, the first to land on an asteroid and the first solar powered spacecraft to travel beyond the orbit of Planet Mars. NEAR Shoemaker was the first of NASA’s “faster, better, cheaper” series of Discovery spacecraft. NEAR stands for Near Earth Asteroid Rendezvous.
Johns Hopkins Applied Physics Laboratory built and managed the NEAR mission. The NEAR Shoemaker spacecraft was originally known as NEAR (Near Earth Asteroid Rendezvous) and was renamed by NASA on March 14, 2000 in honour of geologist Gene Shoemaker. The Near mission was roughly five years from launch (February 17, 1996) until the end of the extended mission on the surface of Eros (February 28, 2001).
The aim of the NEAR mission was to:
1. Determine the physical and geological properties of a near-Earth asteroid. Eros was the target asteroid.
- To further our knowledge on the nature and origin of the many asteroids, meteorites and comets close to Earth’s orbit.
- Further our understanding of how and under what conditions the planets formed and evolved.
Near Shoemaker achieved all of its science goals during the year in orbit and conducted the first long-term close-up study of an asteroid. An additional bonus was despite being designed as an orbiter, it achieved the unbelievable by landing on asteroid Eros. Future human explorers might visit Eros and perhaps in the distant future space tourists will visit it.
NEAR Shoemaker was about the size of a car. It resembled an eight-sided box made of aluminium honeycomb panels, each 1.7 metres square, to which four gallium arsenide solar arrays were attached to provide electrical power. At launch, NEAR weighted 805kg (1.1775 lb), of which 325 (717 lb) was propellant. The scientific payload was much lighter, weighing just 56kg (124 lb).
The spacecraft’s extensive scientific payload comprised: a Mutli-Spectral Imager, a Near-Infrared Spectrometer, an X-Ray/Gamma-Ray Spectrometer, a Laser Rangefinder, a Magnetometer and a Radio Science Experiment.
Information sent back by NEAR included some 160,000 images that covered the entire surface of Eros, and 11 million laser ranging measurements to provide topographical information.
* Johns Hopkins Applied Physics Laboratory designed and built NEAR Shoemaker in 26 months and shipped it to Kennedy Space Center in Florida a month ahead of schedule. It built it in just 26 months at a cost of $223 million – less than expected, Johns Hopkins returned $3million to NASA.
* NEAR Shoemaker was launched by a Boeing Delta 2 rocket from Cape Canaveral in Florida on February 17, 1996. NEAR mission was designed to swing the spacecraft around Earth for a gravity boost which allowed use of the smaller, more economical Delta rocket. A direct trip from Earth to Eros would have taken about a year.
* The five year space trek covered some 3.2 billion km (2 billion miles) and included an Earth swing-by, a flyby of the main-belt asteroid Mathilde and two encounters with Eros.
* NEAR Shoemaker was supposed to reach Eros two years and 327 days after launch. Its entry into orbit around Eros was delayed by a year and 23 days after a failed orbit insertion attempt on December 20, 1998.
* NEAR Shoemaker entered orbit around Eros on February 14, 2000 on Valentine’s Day date. It orbited Eros 230 times from various distances.
* Near Shoemaker landed on Eros on February 12, 2001. It transmitted 69 close-up images of the surface during its four and a half hours descent. It landed on Eros at a gentle 6.4km/hr (4 mph). The landing site of NEAR Shoemaker was at the edge of a saddle-shaped feature on the surface of Eros, known as Himeros.
* After two mission extensions and two weeks of operating on Eros, the NEAR Shoemaker mission end on February 28, 2001 when communications shut down.
Eros is one of the largest near-Earth asteroids, with a mass thousands of times greater than similar asteroids. Eros asteroid is named after the Greek god of love. Eros was the 433rd asteroid to have its orbit calculated. Eros has far fewer craters with diameters below 100 metres (330ft) than was expected from studies of the Moon, Mercury and Mars.
Eros is potato shaped and is 33 kilometres (21 miles) in length and 13 kilometres (8) miles wide. The gravity on Eros is very weak. A person weighing 90kg (200 lb) on Earth would weigh around 50 grams on Eros, and a cork popped from a champagne bottle would have no difficulty in entering orbit around the asteroid.
The temperature on Eros is estimated to vary between 100 degrees Celsius during the day and 150 degrees below zero during the night.
Did you know?
– Near Shoemaker was the first NASA planetary mission to be built and controlled by a non-NASA space center. Radio signals from NEAR Shoemaker took around 15 minutes to travel to Earth during the landing.
– Gene Shoemaker was a geologist and one of the founders of the fields of planetary science and is best known for co-discovering the Comet Shoemaker-Levy 9 with his wife Carolyn Shoemaker and David Levy. He helped to pioneer the field of astrogeology by founding the Astrogeology Research Program of the United States Geological Survey in 1961. He died in a car accident in 1997 while on an annual study of impact craters in the Australian outback. Shoemaker once said he would like to take a geologist’s hammer to Eros.
– Asteroids that come within 121 million miles (195 million kilometres) of the sun are known as near-Earth asteroids. Theory holds that most of these objects broke away from the main asteroid belt between Mars and Jupiter. Aside from the moon they’re our closest neighbours in the solar system.
– NASA used the Deep Space Network with its three antenna stations located in Goldstone (California), Canberra (Australia) and Madrid (Spain) for communications.
Related Space Books
Near Shoemaker Links:
- Near Earth Asteroid Rendezvous Mission: Nasa. Picture Source
- NASA Disovery Program:
- NEAR Information:
- NEAR Shoemaker spacecraft to land on asteroid Eros: Picture Source from ESA.
Any comments or suggestions, then click on Contact Info. | 0.849022 | 3.668887 |
Thanks to data from the Voyager 2 scientists have just discovered that the atmosphere of Uranus is literally leaking gas out into space.
Buried inside data gathered by NASA’s iconic Voyager 2 spacecraft during its historic 1986 encounter with the icy planet was the presence of a plasmoid – a pocket of atmospheric material escaping away from Uranus through the planet’s magnetic field.
Based on these data, NASA suggests that the plasmoid itself was about 127,000 miles long and twice as wide.
But Uranus is not the only planet where the atmosphere leaks out into space. Planetary atmospheres all over the solar system are leaking into space.
Hydrogen springs from Venus to join the solar wind, the continuous stream of particles escaping the Sun. Jupiter and Saturn eject globs of their electrically-charged air.
Even Earth is losing about 90 tonnes of atmospheric material a day. But don’t worry, we have around 5,140 trillion tonnes left.
You Might Like This: The Atmospheres of the Solar System
While these effects are pretty tiny on human timescales, in astronomical terms atmospheric escape can fundamentally alter a planet’s fate. Look at Mars for example.
Mars used to be a wet planet with a thick atmosphere. But during its 4 billion years of leakage to space, the red planet turned into a dusty barren wasteland.
The magnetic field of a planet drives atmospheric escape, which can both help and hamper the process.
The magnetic field can act as a protector for a planet, fending off the atmosphere-stripping blasts of the solar wind. But they can also create opportunities for escape.
However, Uranus’ situation is particularly complicated because the planet rotates on its side with the magnetic poles angled 59 degrees away from the geographic poles. So its magnetic field is a straight-up mess.
The Voyager data used for this analysis is over two decades old. Ideally, scientists would piece together more observations of Uranus’ magnetic field, enough to better understand how this phenomenon has shaped the planet over time. But that will require another probe to visit the strange world.
The research has been published in Geophysical Research Letters. | 0.855496 | 3.642949 |
By the way, Whatsisname's diagram explicitly answers your question, look which axis the jets follow.
I wanted to make sure that the areas of radio emission always coincide with the jets, but thanks for the explanation. I can understand why Vladimir hasn't been able to implement astrophysical jets in SE yet, because there are certainly a lot of issues to work out, like how to model the distortion in the accretion disc when the jets are off-axis, and ensuring that the magnetic axes of known pulsars are oriented so that their jets can point toward Earth.
A followup on this discussion about pulsar jets that I started last year: When observing a pulsar from Earth, can we determine what the angle between the rotation axis and magnetic axis is?
Source of the post When observing a pulsar from Earth, can we determine what the angle between the rotation axis and magnetic axis is?
A late answer, but the answer is yes, this can in fact be done! The method is outlined in section 2 of the paper On the Evolution of Pulsar Beams by Tauris and Manchester (1998), where the angle between the rotation axis and magnetic axis is labelled α:
The details are fairly complicated, but the basic idea is straightforward. To determine the angle, we're fitting a model of the pulsar's sweeping beams of emission to the signal we observe. What we need are measurements of the period of the signal, the width of the pulse (how wide is the segment of the beam that crosses us), and its polarization. The polarization reveals information about the magnetic fields the radiation passed through -- that is, what part of the pulsar beam are we seeing? Combining that with the period and pulse width reveal how far that beam is from the spin axis.
This isn't foolproof and it may not work with all pulsars. Some pulsars "glitch" which can throw off everything. The results may also depend on model assumptions, sometimes by 20-30 degrees. That being said, it has been accurate enough to reveal a lot of interesting information about pulsar evolution. For example, for the first few thousand years the magnetic axis tends to migrate away from the spin axis until they are nearly orthogonal! Then for the next millions of years a magnetic braking effect slows the pulsar's spin rate and also brings the magnetic axis back towards the spin axis, until they are closely aligned. The pulsar's beam also becomes narrower. Pulsar magnetic alignment and the pulsewidth–age relation.
Is there a list of pulsars with known values of α and ζ? The ramifications for Space Engine would require neutron stars to have values of NorthLat, NorthLon, SouthLat and SouthLon like auroras on planets do, and to generate those values randomly if they're not known. Given the RA and Dec of a pulsar, defining the rotation axis with a quarternion and determining latitude and longitude coordinates for the magnetic poles such that one jet will sweep across Earth would be an interesting math problem, but it's beyond my ability.
Source of the post We on the forum have talked about this many times, and I always have to remind people that known physics DOES NOT FORBID FTL. Hell, things in our universe are traveling faster the light right 'now' beyond the Cosmic Event Horizon (it's important to note that this is from our perspective. It's all relative).
A big difference though: nobody directly measures such FTL motion of galaxies in the universe, or objects passing below a black hole's horizon, or other such instances where we might say velocities are faster than c. There are no actual causality issues with those motions. But with an Alcubierre drive, someone would measure that FTL motion, and it is trivial to construct a causal paradox with it. Just imagine someone making a round trip FTL journey. Then we're back to the grandfather paradox of special relativity. In my view this is a pretty powerful reason for concluding the Alcubierre style of warp drive is not possible, even aside from the exotic energy requirements. (We could alternatively say the exotic energy requirements are a symptom of this being a nonphysical solution of general relativity's equations).
It could only be possible if we could resolve the paradox in some other way (like MWT or Deutsch's model.)
So I have a roleplay character, that has the following addictions. I believe that her body would build up an immunity to these addictions, or would it lead to a premature death? Would this addiction get rid of her sense of smell and effect her nervous system? I believe it would, but I'm curious to see other people's thoughts on what would happen to someone that has these addictions over a long term basis, and potential cures if harm does occur.
She enjoys the smell of Propane, Gasoline, Kerosene, Paint Thinner, Oil, Diesel, and has a massive addiction to the consumption of Diethyl Ether and Polyethylene glycol, aswell as various other fluids that are polyetheric and organic in nature.
What does a sea that is blue on earth look like on a planet under a white / blue sun?
My guess, blue. I’m not sure if it reflects or refracts blue light but either way, its not absorbing it, and the sun is white, so that’s answered. Under a blue sun, probably more blue than on earth. BUT, if there was photosynthesizing organisms like cyano bacteria, algae, plankton, or some alien equivalent, then it could vary. With a blue sun, depending on the sensitivity of the organisms, they might want that blue light, so the seas might look black or dark orange-ish, but if the blue light is too intense, they might be blue. White/Blue would be in between. Someone might want to cross check me though.
Is there such thing as a stable orbit, or do the laws of physics forbid this? As in, any two body system should lose energy to gravitational radiation right? Even if one of the bodies were anomalous, like a space craft stabilizing an orbit, since over infinite time, it would need infinite energy to stabilize an orbit. Or is there a geometry of spacetime that allows for 0 gravitational radiation in a system, or one that reabsorbs that loss and is then net 0, like a universe with looped ends or something?
Source of the post Is there such thing as a stable orbit, or do the laws of physics forbid this? As in, any two body system should lose energy to gravitational radiation right?
Yep, you're completely right. All orbital motion generates gravitational waves, which while for most situations is a really, really small effect, would nevertheless cause all objects to spiral together given enough time... assuming proton decay, cosmic expansion, or a Big Rip doesn't get in the way first.
You raise a fascinating question though with introducing a curvature to the space. If the universe is positively curved then the gravitational waves could eventually come back together at the "opposite side" or antipode of the universe, just like how all lines of longitude radiating out from the North pole eventually converge at the South pole on the Earth. And then they'll converge once again back where they started, at the system that was radiating them.
Could those waves somehow actually pump orbital energy back into that system, cancelling out their decay? Well, we'd need to calculate the propagation of those gravitational waves through the positively curved 3D space, while that space is presumably expanding or contracting (unless we perfectly balance it with dark energy?), and then how the re-converging waves then affect those two orbiting bodies much later.
As I contemplate the notion of doing such a calculation to see if it could work that way, the following meme comes to mind,
► Show Spoiler
and I conclude the answer is "it probably doesn't work that way".
(Actually I am quite sure it could not work that way, because as time goes on the rate of energy radiated by the decaying orbits will increase, and so even if the system could perfectly re-absorb that energy (totally dubious) after it has traveled across the whole universe, by the time those waves come back they won't offset the current decay rate.)
Slightly aside, if we consider quantum mechanical systems like electrons orbiting protons in atoms, then those orbits are stable against gravitational decay. In fact they are also stable against electromagnetic decay. A classical calculation would suggest that because an electron orbiting a nucleus is constantly accelerating, and accelerating charges radiate, the electron should very rapidly lose orbital energy and crash into the nucleus. All atoms should collapse in a tiny fraction of a second!
This doesn't happen because the electron isn't really "orbiting". Its energy is quantized (thus the different, discrete energy levels in the atom), and the electron can only jump between those levels by absorbing or emitting a specific wavelength of photon.
However, there's another phenomenon that prevents the electron "orbit" in an atom from being stable indefinitely, anyway: quantum tunneling.
What is the structure of the interstellar medium on a galactic scale? In maps I've seen, the interstellar medium typically forms a shell around the sun a few hundred lightyears away. (The maps tend to be inconsistent, I guess the exact shape is still being figured out?) What is the structure beyond our local bubble? Is the entire galactic disc swiss cheese'd with bubbles and holes? Does it get thicker in the spiral arms, or disappear in between the arms?
Source of the post What is the structure of the interstellar medium on a galactic scale? In maps I've seen, the interstellar medium typically forms a shell around the sun a few hundred lightyears away.
This is a fascinating and very complicated topic. I wanted to create a separate topic in the forum since last year, called "Atlas of the Solar Neighbourhood", where we can do the detailed insight this thing merits. I will launch it given enought time (and study). For now let me adress at least the concern of the maps been inconsistent. Making good visualizations and maps of what essentially is just a gas is very difficult. Even if you know the actual shape and density distribution of it you have to realize that a few things make it very hard to visualize. There are several issues related to this:
1) When we represent a 3D structure in a 2D map we lose a lot of information. We can tackle this by making different 2D maps from different perspectives. For example one that uses the Solar to Galactic Center line as the x-axis and the Solar - North Galactic Pole line as the y-axis (perpendicular to the galactic disc), the so called UW plane (to note the vertical structure of the galactic disc), another that uses the same x-axis but lies on the galactic plane, with the y-axis pointing in the same direction as the Sun moves, the so called UV plane (to better visualize the disc structure around us), and many other possible projections of the actual 3D structure. We can also make an equirectangular projection of what we see from Earth radially. But as I say, translating 3D objets to 2D representations (or any lowering in dimensions) always comes to a cost in the amount of information.
A very simple example is this object that can be projected linearly into a circle, a square or a triangle (all very different shapes with very different qualitative descriptions) depending only on your choice of perspective. The Interstellar Medium is shaped in a very intricate way so you have to choose what information is the one you want to prioritize in your representation. Looking for the Gould Belt for example (a ring of blue stars that surrounds the Solar System with 1500 ly in radius and that is almost parallel to the galactic plane) from the UW plane perspective you would only see a line and all the visual information about the ring shape is lost by squishing. On the other hand, the UV plane perspective gives the ring information but since you squish everything vertically in the galactic disc you no longer have a reference as to how inclined is this plane with respect to the disc. These decisions make interstellar structure maps often complicated to interpret. In fact there are features that no shadow-casted perspective allows for a good visualization into a 2D map! For this reason data scientists have invented PCA and other dimensionality reduction algorithms that transform a 3D system into a 2D map in such a complicated way as to allow the specified feature to be clearly separated from the mess but with the downside that axes are no longer equally measured nor perpendicularly oriented between themselves and can even be distorted in non-linear ways to reach that goal (which makes the intuition about the actual 3D distribution of the entire ensamble go insane even if now you can clearly see some specific part of it). You might have encountered these representations in scientific articles. They are no inconsistent, they are only different perspectives depending on the focus of the research. The actual 3D distribution is actually fairly modeled.
2) There is no solid surface but a solid volume so we have to make slices. Since the gas is a volumetric object it is not enought to represent it as a solid blob with opaque exterior. Sometimes you want to get some insight on what is inside of it. So to do that you need to make a cut and dissect the object. By doing so you lose information about the enclosure but gain information about the internal structure. We all realize how missleading a slice of a human body is to understand what a person looks like from any conceivable angle but how usefull is to make these kind of representations to help visualize the shape of different organs and how they are connected. The same goes for the interstellar medium, there are artistic representations that show the view from the outside but several shells and clouds overlap and you lose the details of the ensamble, and there are representations that show things as you would see them if you made a cut somewhere.
For example, this is a representation of the 815 ly around the sun as viewed from the UV plane perspective (top-down view from above the galactic disc). But is just a specific slice of it, the UV plane that crosses the Sun. Here you can see a more or less consistent region of low density medium (the Local Chimney) surrounded by denser walls (and huge gaps called tunnels). This is not a closed irregular cavity but is opened from above and below the galactic disk. You can see that from the UW perspective and sliced so that the sun is contained in the plane:
I'm not going to explain in detail here but the chimney is the result of several overlaping cavities generated by supernovas a few million years ago in this region of the disc (the sun is unrelated but we have been traveling inside this structure for some ten million years now and we are currently just in the middle). These, more or less spherical, cavities have been compressed by the pressure of the gas in the disc, squished until they have poped into the less pressurized region above and below the disk, creating this cilindrical lower-density medium. If we didn't sliced the first representation we would have seen gas everytwhere since the chimney has it's axis inclined with respect to the perpendicular of the galactic disc and thus there are parts of the upper exit that would obstruct the view of the inner part of the chimney and the same goes for the lower exit. A good perspective would be the view from a certain angle so you can peer through the chimney to the other side, but since it has an hourglass shape (the chimney gets thinner in the middle and opens at the exits) you would always miss information about the walls of the opening of the other side. So you really need to make a cut in the structure and visualize it with slices. The UV cut made to contain the Solar System might not even be very helpfull for other purposes. Another UV plane sliced at another hight (paralell to the first UV plane) might be much more interesting. Maybe we have lost a tunnel in intergalatic medium connecting the chimney in the side to other structures nearby just because the tunnel was higher up in the chimney and we decided to make the cut at solar hight. These are one of the many problems in trying to represent these features. Just so you have an actual example of this, here they've made many different slices, all aligned y-axis to the North Galactic pole and rotated 15º degrees each (all the slices centered on the solar system). You can see how the apparent shape of the local chimney changes as we move around.
There is no inconsistency in the mappings is just a matter of perspective and good slicing. Different but complementary visualizations that yield different information about the real structure.
3) We are talking about a gas not any volumetric object. Gradients are tricky. What is the wall of the local chimney? This might seem a simple question but since we are dealing with gases and they tend to be distributed in continuous gradients of density the way we establish the boundary comes to a decision that can make for very different visual representations. If we take density as the feature to be taken into account then before visually representing the structure we need to mark an equal-density surface (a threshold to signal the transition between the lower densities under consideration and the higher ones).
Just so you see the extreme differences caused by different iso-density surfaces selection take a look at this. Here they've added countour lines to the interior of the local chimney as seen in the UW plane cointaining the Solar System. The countour lines are nothing else than the result of slicing the iso-density surfaces.
As you can see the lower density region is not only smaller but completely different in shape as other boundaries marking higher densities. Adding more countour lines helps to grasp the density gradient of the gas, but can be a mess to have it in a detailed map. So maps have also to choose the threshold to which they determine the boundaries of different structures in the interstellar medium. That is another reason for apparent discrepancy in visual representations.
Look at this depiction of the local chimney
Again, we are not getting information of what is inside and how it's structured. So a solution is to create 3D renders on which the equal-density surfaces are many and semitransparent so you can see the others. This is what they did in this animation of the entire solar neighbourhood:
As you can see it is still very difficult to extract a meaninful description of what you see in here. Also video and 3D rederings are not a good for printed articles.
4) Fail to explain the structures involved and confusion. Scientists not always explain these structures in a orderly, schematic and clear way when it comes to communicating to the public. The thing is that the stellar neighbourhood cosmography is almost like a Matryoshka doll. The solar system is embeded inside the Local Interstellar Cloud (LIC) which is interacting with another gaseous medium called the G-cloud (which contains the alpha centauri system and other nearby stars in that direction). Both the LIC and G-cloud are less than 10 pc in size, and both reside inside the Local Bubble which is around 300 pc in size, but the Local Bubble is just an undifferentiated part of what is now known as the Local Chimney which is in the 800 pc regime. All of this is part of a region called the Orion Spur, which is a branch of the Orion spiral arm of the Milky way. Inside the Local Bubble we know of around 15 clouds (like the LIC and G-cloud). They deform and interact one with the other and are subjected to stellar wind forces from our closest neighbours. These clouds have filamentary structures at the scale of parsecs due to the magnetic field of the galaxy shaping them, in a similar way as the iron filings behave when exposed to a bar magnet, following the magnetic field lines.
The Local Bubble at another scale is also not alone. Connected to it by interstellar tunnels in the gas there is the Loop I bubble and other structures of hundreths of parsec in size.
They are not filamentary like the much smaller interstellar clouds inside the bubbles, they are shaped like spherical and cilindrical cavities (results of supernova shells overlapping toghether). It is indeed like cheese in the sense that there are lots of tunnels connecting these "voids" traversing the more dense walls of the galactic interstellar medium.
Besides all of this, many do not fully realize the fact that these clouds and bubbles are essentially vacuum. The thing is that clouds like the LIC are 0.3 atoms per cm3 dense, that the bubble is floats inside (the Local Bubble) is empty in comparison with just 0.05 atoms per cm3 and that these bubbles are pressed against by the interstellar medium of the rest of the galaxy which is almost as ethereal as the clouds inside the bubbles with just 0.5 atoms per cm3. But 0.3, 0.05 and 0.5 atoms/cm3 is essentially the same as a vacuum. In fact all of them have lower densities than the vast majority of vacuum chambers on Earth (and still they are clouds, and material mediums that interact). When viewed from the scale of a galactic sized creature these are indeed dense gasses with clear differences, from our perspective it is just a huge void filled with stars.
Another source of confusion is the fact that scientists consider different things clouds and bubbles in relation to their surrounding material. For example, if the LIC was located outside the Local Bubble in the interstellar medium of the galaxy then it wouldn't be considered a cloud but a void (or a small bubble), since it is less dense than it's surroundings. But since it is inside a less dense bubble which is encapsulated in a more dense medium we talk about is as a cloud. So this relative designation yields a lot of confusion when talking about other structures. Remeber, it's all relative to its inmediate surroundings.
If you want to read about this I can reccomend some easy to follow explanations from the very basics. Also there are awesome maps made to explain this architecture in detail and not only to point some specific feature while obscuring others as research papers tend to do.
For the 100 pc to 600 pc surroundings of the Solar System:
Source of the post If you had an Earth around a hotter star and it's in the habitable zone, will the star be the same (similar apparent brightness in the sky as the sun or not?
Similar, but not exactly the same. In fact, if the star is either much hotter or colder than our Sun, then from the habitable zone its apparent magnitude will be slightly dimmer!
To keep Earth's temperature the same, the amount of solar radiation hitting it must be the same. We would measure the same number of watts per square meter in sunlight at the top of the atmosphere. But if the star is hotter, then its spectrum will peak at shorter (bluer) wavelengths:
And here's the key: our eyes are not equally sensitive to all colors of light, even across the visible spectrum:
Our eyes see color via 3 types of cones, each of which is sensitive to different but overlapping parts of the visible spectrum.. Their combined response makes our eyes most sensitive to green light, and the sensitivity drops off rapidly towards red or violet. This isn't obvious in everyday experience, but can be witnessed dramatically by shining lasers of different colors but equal intensity. A 5mW green laser appears much brighter than a 5mW red or violet laser. Yet they give off the same amount of light.
But just how big of a difference will this effect make for the appearance of our Sun, if its temperature were different but we move the Earth so that it stays in the habitable zone? Using the process outlined here for calculating the apparent magnitude of a star using the sensitivity curves of a V filter (which most closely resembles our own eyesight), I find the following apparent visual magnitudes for stars of different temperatures from their habitable zones and plot them. All are computed from a distance where the flux of sunlight is kept the same as what we get here on Earth (about 1368W/m2). Our own Sun's temperature and apparent magnitude is marked with a + for reference.
Our Sun is near the minimum of the curve, or the brightest apparent magnitude. Coincidence? A little bit, but also a product of evolution. Our vision evolved to be sensitive to a window of wavelengths that the Earth's atmosphere transmits, which is also where the Sun's spectrum peaks.
But the true minimum is a little further to the right, at higher temperatures of about 6700 Kelvin, corresponding to F-type stars. This is where we consider the star's color to be "white" instead of "yellow" like our Sun, and we would get a slightly stronger response from our eyes. At 6700K the star would appear brighter from its habitable zone by about 0.05 magnitudes (too small a difference to be noticeable by any stretch of imagination). For even higher temperatures, the star appears dimmer, because larger fractions of its light are made up of blue, violet, and even ultraviolet light that we are less sensitive to.
Hot B-class stars with temperatures over 25,000K would appear 2 magnitudes dimmer from a distance that would feel comfortable (ignoring being fried by UV radiation). On the other end, cool M-class stars with temperatures under 3000K would also appear more than 2 magnitudes dimmer, with most of their warmth coming through infrared.
I see. That's very interesting! Quite useful for worldbuilding purposes as I feared that planets around hotter stars in habitable zones would also be brighter, and thus an unpleasant place to live. Even the hottest stars, maybe 0 type stars would still have the same apparent brightness as our sun but appear as a pinprick of light in the sky. That'd be very interesting to see.
If we had an Earth around a hotter sun in a habitable, say an F, A, or O star, would we get sunburn easier? Would it be as pleasant or not so much as our Earth? | 0.917252 | 3.805693 |
Elusive Mercury is second evening star alongside Venus
Orion is striding proudly across the meridian as darkness falls, but, even before the twilight dims, we have our best chances this year to spot Mercury low down in the west and close to the more familiar brilliant planet Venus.
Both evening stars lie within the same field-of-view in binoculars for much of March, so the fainter Mercury should be relatively easy to locate using Venus as a guide. Provided, of course, that we have an unobstructed horizon. Mercury never strays far from the Sun’s glare, making it the most elusive of the naked-eye planets – indeed, it is claimed that many astronomers, including Copernicus, never saw it.
Blazing at magnitude -3.9, Venus hovers only 9° above Edinburgh’s western horizon at sunset on the 1st and sets 64 minutes later. Mercury, one tenth as bright at magnitude -1.3, lies 2.0° (four Moon-breadths) below and to its right and may be glimpsed through binoculars as the twilight fades. Mercury stands 1.1° to the right of Venus on the 3rd and soon becomes a naked eye object as both planets stand higher from night to night, becoming visible until later in the darkening sky.
By the 15th, Mercury lies 4° above-right of Venus and at its maximum angle of 18° from the Sun, although it has more than halved in brightness to magnitude 0.2. The slender young Moon sits 5° below-left of Venus on the 18th and 11° above-left of the planetary pairing on the 19th. Earthshine, “the old Moon in the new Moon’s arms”, should be a striking sight over the following few evenings.
On the 22nd, the 30% illuminated Moon creeps through the V-shaped Hyades star cluster and hides (occults) Taurus’ leading star Aldebaran between 23:31 and 00:14 as they sink low into Edinburgh’s west-north-western sky.
Falling back towards the Sun, Mercury fades sharply to magnitude 1.4 by the 22nd when it passes 5° right of Venus and becomes lost from view during the following week. At the month’s end, Venus stands 15° high at sunset and sets two hours later.
The Sun climbs 12° northwards in March to cross the sky’s equator at the vernal equinox at 16:15 on the 20th, which is five days before we set our clocks forward at the start of British Summer Time. Sunrise/sunset times for Edinburgh change from 07:04/17:47 GMT on the 1st to 06:46/19:49 BST (05:46/18:49 GMT) on the 31st. The Moon is full on the 2nd, at last quarter on the 9th, new on the 17th, at first quarter on the 24th and full again on the 31st.
Orion is sinking to our western horizon at our star map times while the Plough, the asterism formed by the brighter stars of Ursa Major, is soaring high in the east towards the zenith. To the south of Ursa Major, and just reaching our meridian, is Leo which is said to represent the Nemean lion strangled by Hercules (aka Heracles) in the first of his twelve labours. Leo appears to be facing west and squatting in a similar pose to that of the lions at the foot of Nelson’s Column in Trafalgar Square.
Leo’s Sickle, the reversed question mark that curls above Leo’s brightest star Regulus, outlines its head and mane and contains the famous double star Algieba whose two component stars, both much larger than our Sun, take more than 500 years to orbit each other and may be seen through a small telescope. Regulus, itself, is occulted as they sink towards Edinburgh’s western horizon at 06:02 on the morning of the 1st.
Jupiter, easily our brightest morning object, rises at Edinburgh’s east-south-eastern horizon at 00:47 GMT on the 1st and at 23:41 BST (22:41 GMT) on the 31st, climbing to pass around 17° high in the south some four hours later. Brightening from magnitude -2.2 to -2.4, it is slow moving in Libra, being stationary on the 9th when its motion reverses from easterly to westerly. Jupiter is obvious below the Moon on the 7th when a telescope shows the Jovian disk to be 40 arcseconds wide.
If we look below and to the left of Jupiter in the south before dawn, the three objects that catch our attention are the red supergiant star Antares in Scorpius and, further from Jupiter, the planets Mars and Saturn.
Mars lies in southern Ophiuchus, between Antares and Saturn, and is heading eastwards into Sagittarius and towards a conjunction with Saturn in early April. The angle between the two planets falls from 17° to only 1.5° this month as Mars brightens from magnitude 0.8 to 0.3 and its distance falls from 210 million to 166 million km. Mars’ disk swells from 6.7 to 8.4 arcseconds, becoming large enough for surface detail to be visible through decent telescopes. Sadly, Mars (like Saturn) is so far south and so low in Scotland’s sky that the “seeing” is unlikely to be crisp and sharp.
Incidentally, on the morning of the 19th Mars passes between two of the southern sky’s showpiece objects, being a Moon’s breadth below the Trifid Nebula and twice this distance above the Lagoon Nebula. Both glowing clouds of hydrogen, dust and young stars appear as hazy patches through binoculars but are stunning in photographs.
Saturn, creeping eastwards just above the Teapot of Sagittarius, improves from magnitude 0.6 to 0.5 and has a 16 arcseconds disk set within its superb rings which span 37 arcseconds at midmonth and have their northern face tipped towards us at 26°. The waning Moon lies above-left of Mars on the 10th and close to Saturn on the 11th.
Diary for 2018 March
Times are GMT until March 25, BST thereafter.
1st 06h Moon occults Regulus (disappears at 06:02 for Edinburgh)
2nd 01h Full moon
4th 14h Neptune in conjunction with Sun
5th 18h Mercury 1.4° N of Venus
7th 07h Moon 4° N of Jupiter
9th 10h Jupiter stationary (motion against stars reverses from E to W)
9th 11h Last quarter
10th 01h Moon 4° N of Mars
11th 02h Moon 2.2° N of Saturn
15th 15h Mercury furthest E of Sun (18°)
17th 13h New moon
18th 01h Mercury 4° N of Venus
18th 18h Moon 8° S of Mercury
18th 19h Moon 4° S of Venus
20th 16:15 Vernal equinox
23rd 00h Moon occults Aldebaran (23:31 to 00:14 for Edinburgh)
24th 16h First quarter
25th 01h Start of British Summer Time
27th 02h Moon 1.8° S of star cluster Praesepe in Cancer
31st 14h Full moon | 0.892916 | 3.644073 |
We have in these pages chronicled the feats of great explores of previous eras. Yet our own era has witnessed what is perhaps the greatest, most awe-inspiring feat of exploration in the history of the man on earth: the Voyager program that explored the outer solar system. This was to be an exploration much different in kind from the great expeditions of old. There were no pack mules, native guides, or recalcitrant companions; but there were the same incredible risks of environment and circumstance that have accompanied exploration from the time the Phoenicians first circumnavigated Africa. The Voyager probes were man’s first tentative steps to walk beyond the confines of his own planet. Perhaps when the long perspective is finally taken by our remote descendants, the Voyager program will rank among the most the most significant event in the history of our species.
The idea of exploring the outer solar system had long enchanted astronomers. But it was not until a unique event happened that this dream became a feasible reality. In the early 1970s, astronomers realized that the orbits of the outer planets (Jupiter, Saturn, Uranus, and Neptune) would coincide in a favorable alignment. This event happened, we are told, only once every 176 years. It would be possible for a fast-moving spacecraft to take advantage of this alignment and see in a relatively short time what it might otherwise take decades to see. In addition, a spacecraft would be able take advantage of the gravitational fields of these planets to “sling-shot” itself from one to the other at high velocities.
NASA knew that the program would be an expensive one, and that resistance to it would be strong. President Nixon authorized the program on the condition that it only explore two of the outer planets; the scientists, however, shrewdly decided to plan for seeing all of them. They correctly understood that once the first images of these planets came back, there would be support for extending the program further. Indeed, to what better use could a NASA budget be put? So planning began. There would be two probes: Voyager 1 and Voyager 2. Each probe weighted about 780 kg. and was powered by a decaying plutonium isotope. Through normal system degradation, they would lose about 0.8% of their power per year.
Voyager 2 was launched first, on August 20, 1977. Its mission was to fly past the immense outer planets Jupiter, Saturn, Uranus, and Neptune. Voyager 1 was launched soon after, but it was tasked with exploring Saturn and its large moon Titan. Two probes were needed because one would not be able to provide the kind of “grand tour” that the scientists were looking for. And so the great epic began.
It is difficult for us to appreciate the immense scale of space. The average person can relate to waves, storms, jungles, fevers, and starvation brought about by expired provisions. But space is totally different. It was not designed for man. It is terrifying: dark, empty, silent, and indifferent. Distances are vast; objects are strange, huge, and intimidating; and the hazards are partly known, and partly unknown. The scientists who designed and carried out the Voyager missions showed a degree of patience and heroism that was every bit the equal of the Iberian monarchs of Spain and Portugal who patiently funded and supported the explorations of the great 15th century navigators.
Voyager 2 first encountered Jupiter in the summer of 1979. Images of Jupiter are familiar to us today, but we must remember that no one had ever seen what the planet really looked like. It is easy for us today to laugh at Pliny the Elder’s repetition of myths and fables of foreign lands in his Historia Naturalis; yet we forget that we were (and in some ways still are) just as ignorant of our own solar system. We were limited by our inadequate earth-bound telescopes, which could show us little more than hazy clouds. The first images sent back from this huge gas-ball were thus greeted with amazement and shock. Active volcanoes were even discovered on the moon Io, the first time vulcanism had been observed anywhere beyond Earth. If only Galileo and Huygens could have lived to see these photos.
Explorations of Jupiter’s moons followed; then Saturn was reached in 1981. There was a moment of panic at NASA’s mission control right after the Saturn fly-by, when the probe’s cameras froze in place. But engineers got it working again by gently rotating it back and forth, just as one might free a car spinning its wheels in snow. The probe came closest to Uranus in January 1986. This planet seemed to many to be a let-down; all that could be seen was a turquoise-blue ball. But the planet did have its own surprises: it possessed a weird rotation with a corkscrew-like magnetic field, and even had its own rings. Even stranger was Uranus’s moon Miranda, which had a bizarre surface that looked like it had been gouged with gigantic set of fingers.
Neptune was reached in 1989, and the data relayed proved to be just as fascinating as everything that had come before it. Once Neptune had been explored, the focus of the probes shifted to penetrating the so-called “heliosphere”; that is, the boundary between our solar system and interstellar space. No objects in human history have traveled longer or faster than the Voyager probes. Long after our race will have either expired or left Earth, these lumps of metal will be floating in interstellar space for tens of millions of years, perhaps longer, or perhaps to be picked up by some curious extraterrestrial civilization during this time. In anticipation of this sublime expectation, the scientists who designed the Voyager probes outfitted it with a “golden record” meant to be an affidavit, so to speak, in testimony of our race and our civilization. The record contained greetings in dozens of languages and some basic information about Earth. In the literal sense of the word, it was perhaps one of the most optimistic acts ever taken.
Voyager 1 left the heliosphere in 2012; Voyager 2 is expected to enter interstellar space in 2019 or 2020. Carl Sagan was involved with the Voyager program. His unique genius was his ability to convey the awe and wonder of these fantastic scientific achievements to the general public in a way that tied them to history and philosophy. It was typical of Sagan’s visionary ability to think of doing things no one else would think of doing. As the probes were leaving the solar system, everyone thought that the time for photography had ended. Not Sagan. He petitioned strongly for mission control to turn the probe’s cameras around to look back on Earth. This turned out to be surprisingly difficult to do, as no one could see the point.
But Sagan wanted to make a sublime point about man and the universe. When the photo was actually taken, it showed the Earth as a minuscule blue dot set against a field of eternity. No other image could quite convey the awesome preciousness of our planet and of life on Earth, when set against the immensity of the eternal void. At a television conference, Sagan said these words:
Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar”, every “supreme leader”, every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam…
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light.
When I first read these words, I found them very much evocative of Cicero’s Dream of Scipio (an essay I translated in my book Stoic Paradoxes). In the Dream, Cicero imagines a scene of astral projection, where the characters in the essay are suspended in space, looking down on the Earth:
When I had looked on all of this, shocked, and had finished processing everything, I said, “What is this sweet sound that is filling my ears?” “That is,” he said, “the sound produced by the acceleration and motion of these celestial spheres, separated in unequal intervals, but occupying distinct, measured proportions, and making high and low sounds with a varying and equal unity. They cannot undertake such motions in silence. And nature makes things such that heavy tones come from one extreme, and high tones come from the other…
Then Africanus said, “I see that you are still looking at the home and place of origin of mankind. If it appears to be small, as it is, then just look at the heavenly bodies, and disregard the petty affairs of man. What fame can you achieve from the words of men, or what desired glory? You can see that the earth is really only inhabited in a few sparse and narrow spots; and between the places where people live are vast empty regions, so that no real communication is possible between these groups. They are located in places sometimes oblique, sometimes transverse, and sometimes adverse to you: from this fact you can certainly expect no glory…
“All of that land, which is occupied by you, is narrow from pole to pole, and broad from east to west. Can you see that it actually is only a small island surrounded by that body of water which you call on Earth the Atlantic, or the Great Expanse, or the Ocean? Despite its name, can you see that it is tiny? From these same settled and known lands, which you can see from here, can your name (or anyone else’s name) ever spill over beyond the Caucasus Mountains, or swim the immense Ganges River? Who in the eastern regions of the rising sun, or in the farthest regions of the north or south, will ever hear the sound of your name? Taking away these regions for the moment, it is clear that your mortal glory wants to spread over a pathetically narrow area. Will those who talk about us now, continue to talk about us in the future?
“Even if the descendants of future generations might want to hand down to posterity the plaudits of each one of us which they heard from their elders, nevertheless, because of the floods and fires of the earth, which always come from time to time, we can hardly expect a glory that is long-lasting, much less one that is eternal. Why does it matter when those who were born after you may talk about you, when you gained nothing from those who lived before you?…” [Stoic Paradoxes, p. 94-97]
Who would have thought that a two thousand-year old treatise of Cicero would be so prescient, and so relevant, to today’s seekers of truth? Sagan’s ability to convey the awe and wonder of the universe and our place in it is one of the things that make his seminal television series Cosmos still very much worth watching today. I watched this series as a boy growing up, and I would have to credit Sagan as a tremendous influence on my own outlook and pedagogical style. I loved how he blended history, philosophy, and modern science in a way that fired the imagination of the reader or viewer. He was a man of true vision and learning.
The Voyager probes are still functioning, and still moving farther and farther away from their planet of origin. Their mission was an unqualified success, a success that exceeded the wildest hopes and expectations of their original planners in the early 1970s. It was not just a fantastic achievement in exploration and science: it was a defining moment in human biology. Who, upon learning of the scope of the Voyager program’s achievements, can fail to be overcome with awe?
Read more about the “Dream of Scipio” in my Stoic Paradoxes. | 0.843965 | 3.095771 |
Though close to home, the space immediately around Earth is full of hidden secrets and invisible processes. In a new discovery reported in the journal Nature, scientists working with NASA’s Magnetospheric Multiscale spacecraft — MMS — have uncovered a new type of magnetic event in our near-Earth environment by using an innovative technique to squeeze extra information out of the data.
Magnetic reconnection is one of the most important processes in the space — filled with charged particles known as plasma — around Earth. This fundamental process dissipates magnetic energy and propels charged particles, both of which contribute to a dynamic space weather system that scientists want to better understand, and even someday predict, as we do terrestrial weather. Reconnection occurs when crossed magnetic field lines snap, explosively flinging away nearby particles at high speeds. The new discovery found reconnection where it has never been seen before — in turbulent plasma.
In a new discovery reported in the journal Nature, scientists working with NASA’s Magnetospheric Multiscale spacecraft — MMS — uncovered a new type of magnetic event in our near-Earth environment. Credits: NASA’s Goddard Space Flight Center/Joy Ng
“In the plasma universe, there are two important phenomena: magnetic reconnection and turbulence,” said Tai Phan, a senior fellow at the University of California, Berkeley, and lead author on the paper. “This discovery bridges these two processes.”
Magnetic reconnection has been observed innumerable times in the magnetosphere — the magnetic environment around Earth — but usually under calm conditions. The new event occurred in a region called the magnetosheath, just outside the outer boundary of the magnetosphere, where the solar wind is extremely turbulent. Previously, scientists didn’t know if reconnection even could occur there, as the plasma is highly chaotic in that region. MMS found it does, but on scales much smaller than previous spacecraft could probe.
In a turbulent magnetic environment, magnetic field lines become scrambled. As the field lines cross, intense electric currents (shown here as bright regions) form and eventually trigger magnetic reconnection (indicated by a flash), which is an explosive event that releases magnetic energy accumulated in the current layers and ejects high-speed bi-directional jets of electrons. NASA’s Magnetospheric Multiscale mission witnessed this process in action as it flew through the electron jets the turbulent boundary just at the edge of Earth’s magnetic environment. Credits: NASA’s Goddard Space Flight Center’s Conceptual Image Lab/Lisa Poje; Simulations by: Colby Haggerty (University of Chicago), Ashley Michini (University of Pennsylvania), Tulasi Parashar (University of Delaware)
MMS uses four identical spacecraft flying in a pyramid formation to study magnetic reconnection around Earth in three dimensions. Because the spacecraft fly incredibly close together — at an average separation of just four-and-a-half miles, they hold the record for closest separation of any multi-spacecraft formation — they are able to observe phenomena no one has seen before. Furthermore, MMS’s instruments are designed to capture data at speeds a hundred times faster than previous missions.
Even though the instruments aboard MMS are incredibly fast, they are still too slow to capture turbulent reconnection in action, which requires observing narrow layers of fast moving particles hurled by the recoiling field lines. Compared to standard reconnection, in which broad jets of ions stream out from the site of reconnection, turbulent reconnection ejects narrow jets of electrons only a couple miles wide.
“The smoking gun evidence is to measure oppositely directed electron jets at the same time, and the four MMS spacecraft were lucky to corner the reconnection site and detect both jets”, said Jonathan Eastwood, a lecturer at Imperial College, London, and a co-author of the paper.
Crucially, MMS scientists were able to leverage the design of one instrument, the Fast Plasma Investigation, to create a technique to interpolate the data — essentially allowing them to read between the lines and gather extra data points — in order to resolve the jets.
“The key event of the paper happens in only 45 milliseconds. This would be one data point with the basic data,” said Amy Rager, a graduate student at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the scientist who developed the technique. “But instead we can get six to seven data points in that region with this method, allowing us to understand what is happening.”
Earth is surrounded by a protective magnetic environment — the magnetosphere — shown here in blue, which deflects a supersonic stream of charged particles from the Sun, known as the solar wind. As the particles flow around Earth’s magnetosphere, it forms a highly turbulent boundary layer called the magnetosheath, shown in yellow. Scientists, like those involved with NASA’s Magnetospheric Multiscale mission, are studying this turbulent region to help us learn more about our dynamic space environment. Credits: NASA’s Goddard Space Flight Center/Mary Pat Hrybyk-Keith; NASA Goddard’s Conceptual Image Lab/Josh Masters
With the new method, the MMS scientists are hopeful they can comb back through existing datasets to find more of these events, and potentially other unexpected discoveries as well.
Magnetic reconnection occurs throughout the universe, so that when we learn about it around our planet — where it’s easiest for Earthlings to examine it — we can apply that information to other processes farther away. The finding of reconnection in turbulence has implications, for example, for studies on the Sun. It may help scientists understand the role magnetic reconnection plays in heating the inexplicably hot solar corona — the Sun’s outer atmosphere — and accelerating the supersonic solar wind. NASA’s upcoming Parker Solar Probe mission launches directly to the Sun in the summer of 2018 to investigate exactly those questions — and that research is all the better armed the more we understand about magnetic reconnection near home.
Publication: T. D. Phan, et al., “Electron magnetic reconnection without ion coupling in Earth’s turbulent magnetosheath,” Nature, volume 557, pages202–206 (2018) doi:10.1038/s41586-018-0091-5 | 0.842114 | 4.009447 |
Physics: Not everything is where it seems to be
Scientists at TU Wien, the University of Innsbruck and the ÖAW have for the first time demonstrated a wave effect that can lead to measurement errors in the optical position estimation of objects. The work now published in Nature Physics could have consequences for optical microscopy and optical astronomy, but could also play a role in position measurements using sound, radar, or gravitational waves.
With modern optical imaging techniques, the position of objects can be measured with a precision that reaches a few nanometers. These techniques are used in the laboratory, for example, to determine the position of atoms in quantum experiments. „We want to know the position of our quantum bits very precisely so that we can manipulate and measure them with laser beams,“ explains Gabriel Araneda from the Department of Experimental Physics at the University of Innsbruck. A collaborative work between physicists at TU Wien, Vienna, led by Arno Rauschenbeutel (now an Alexander von Humboldt Professor at Humboldt-Universität zu Berlin), and researchers at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information, led by Rainer Blatt, has now demonstrated that a systematic error can occur when determining the position of particles that emit elliptically polarized light. “The elliptical polarization causes the wavefronts of the light to have a spiral shape and to hit the imaging optics at a slight angle. This leads to the impression that the source of the light is somewhat off its actual position,” explains Yves Colombe from Rainer Blatt’s team. This could be relevant, for example, in biomedical research, where luminous proteins or nanoparticles are used as markers to determine biological structures. The effect that has now been proven would possibly lead to a distorted image of the actual structures.
Any kind of waves could show this behavior
More than 80 years ago, the physicist Charles G. Darwin, grandson of the British natural scientist Charles Darwin, predicted this effect. Since that time, several theoretical studies have substantiated his prediction. Now, it has been possible for the first time to clearly prove the wave effect in experiments, and this twice: At the University of Innsbruck, physicists determined, through single photon emission, the position of a single barium atom trapped in an ion trap. Physicists at Atominstitut of TU Wien (Vienna) determined the position of a small gold sphere, about 100 nanometers in size, by analyzing its scattered light. In both cases, there was a difference between the observed and the actual position of the particle. “The deviation is on the order of the wavelength of the light and it can add up to a considerable measurement error in many applications,“ says Stefan Walser from Arno Rauschenbeutel’s team. „Super-resolution light microscopy, for example, has already penetrated far into the nanometer range, whereas this effect can lead to errors of several 100 nanometers.” The scientists believe it is very likely that this fundamental systematic error will also play a role in these applications, but this has yet to be proven in separate studies. The researchers also assume that this effect will not only be observed with light sources, but that radar or sonar measurements, for example, could also be affected. The effect could even play a role in future applications for the position estimation of astronomical objects using their gravitational waves emission.
The work has been published in Nature Physics and was financially supported by the Austrian Science Fund FWF, the European Union and the Tyrolean Federation of Industry.
Department of Experimental Physics
University of Innsbruck
phone: +43 512 507 52472
phone: +43 1 58801 141723
Wavelength-scale errors in optical localization due to spin-orbit coupling of light. G. Araneda, S. Walser, Y. Colombe, D. B. Higginbottom, J. Volz, R. Blatt, and A. Rauschenbeutel. Nature Physics 2018 DOI: https://doi.org/10.1038/s41567-018-0301-y | 0.858154 | 3.502901 |
As if a time capsule were treated, the Murchison meteorite, which fell 50 years ago in Australia, had this presolar powder integrated
The official scientific journal of the National Academy of Sciences of the United States, known by its acronym PNAS, has released what is the oldest material on Earth. It is stellar dust that formed between 5,000 and 7,000 billion years ago, even before the Sun formed 4.6 billion years ago. This matter has been found in a meteorite that fell in Australia fifty years ago. The study, entitled “Life span of interstellar dust by exposure to cosmic rays ages of presolar silicon carbide,” has explained that “presolar grains are the oldest dataible solid samples available and that provide an invaluable insight into our preschool chronology. galaxy”.
Having found this material with such antiquity is a historical achievement since presolar grains are difficult to find. It is estimated that they are only present in 5% of meteorites that fall to Earth. Once found, the method, in order to age the oldest material in the known system, has been to determine the age through the study of the neon (Ne) isotopes produced by the galactic cosmic rays. This age distribution It has also confirmed the hypothesis that these grains originate from stars that initially formed 7 billion years ago and that produced dust 5,000 billion years ago. That there are grains with such ages supposes, among other things, that this stellar dust managed to evade destruction in supernova shock waves.
The Murchison meteorite, where this matter has been found and whose fragments fell on the Murchison town, Victoria, in Australia on September 28, 1969, has acted as a kind of time capsule, and the presolar grains analyzed in the study had remained integrated and unchanged in it. These grains were isolated for analysis by creating a kind of paste that, by dissolving in acid, dissolved, leaving only the solar grains. Through this method the scientists managed to separate the star dust from the meteorite and know their age and the type of star to which they belonged. This research has revealed, in addition to the oldest material on Earth, that there are stellar powders between 4,600 and 4,900 million years that were formed in a period of improved star formation in which more stars were formed than usual.
Thus, thanks to the stellar dust found, it has been revealed that 7,000 billion years ago, almost 300 billion years before the formation of the Sun, stars were formed that subsequently expelled material, thanks to which today we can talk about stellar dust more old, known moment, of our system. As stated by the research team that conducted the study, this It can provide unique information about the interstellar dust cycle and star formation events in the Galaxy before the sun is born. | 0.863595 | 3.742838 |
Through the use of GRACES – a fiber optic coupling of Gemini-N and CFHT –a star was detected that is moving at an extremely high velocity and will in fact escape our galaxy. It is theorized to be the result of a failed supernova explosion.
An international team of astronomers led by Stephane Vennes at the Astronomical Institute in the Czech Republic have identified a white dwarf moving faster than the escape velocity of the Milky Way. This high velocity star is thought to be shrapnel thrown away millions of years ago from the site of an ancient, peculiar Type Ia supernova explosion. The team used telescopes located in Arizona, the Canary Islands and Maunakea’s GRACES, a high resolution spectrograph that combines the large aperture of the Gemini North telescope with Espadons, the high resolution spectropolarimeter at CFHT, via a 250m optical fiber link.
Type Ia supernovae play an important role important in our understanding of the Universe. They act as standard candles, astronomical objects for which astronomers have a decent estimate of their intrinsic brightness or luminosity. Astronomers can estimate the true total luminosity of a Type Ia supernovae and use that information to determine the distance. Despite astronomers’ understanding of the luminosity and distance relationship for Type Ia supernovae, very little is known about the explosions themselves. Astronomers build models aimed at a deeper understanding of the engine powering these explosions.
One of these models suggest that at the heart of a Type Ia supernova is a compact star known as a white dwarf. If the white dwarf has a close companion star, over time the gravity of the white dwarf may attract gas from the other star. This continuous feeding compresses the white dwarf to such a high density and temperature that the white dwarf is engulfed in a thermonuclear explosion. It is thought that nothing survives this kind of explosion. However, a new class of models called “subluminous type 1a supernova also known as a Type Iax” can leave a partially burnt remnant that is instantly ejected at high velocity.
“Such a cataclysmic binary star has never been caught feeding and getting just ready for the explosion,” commented Stephane Vennes, leading author of the Science article. “All we ever witness is the aftermath of the explosion, that is the bright flash in the distant Universe that even outshines the galaxy hosting that event. But now, with the discovery of a surviving remnant of the white dwarf itself, we have direct clues to the nature of the most important actor involved in these events.”
The team studied the white dwarf star LP40-365 for two-years with telescopes located in Arizona, the Canary Islands, and Hawaii. The new star was first identified with the National Science Foundation’s (NSF) Mayall four-meter telescope at Kitt Peak National Observatory in Arizona. “We selected this object for observation with the spectrograph at the four-meter telescope because of its large apparent motion across the celestial sphere. Thousands of objects like this one are known, but the sky was partly cloudy on that night and we had to go for the brightest star available which turned out to be LP40-365,” said team member Adela Kawka, underpinning the importance of serendipity in astronomy. “We alerted team members J.R. Thorstensen and E. Alper at Dartmouth College, and P. Nemeth at the Karl Remeis Observatory for urgent follow-up observations.”
A final, crowning data set was obtained with the help of team member Viktor Khalack at the Université de Moncton using a unique instrument, GRACES on Maunakea. GRACES is a collaboration between the Canada-France-Hawaii Telescope and the NSF Gemini Observatory. When GRACES is in use, CFHT’s spectropolarimeter Espadons receives light fed by an optical fiber hooked to its neighbor on the summit, the eight-meter Gemini North telescope. “GRACES provides astronomers the best of both worlds, the light collecting power of the Gemini observatory combined with a state of the art instrument like Espadons. The combination packs a powerful punch and creates opportunities for discoveries like this one” says Nadine Manset, the GRACES instrument scientist at CFHT.
After collecting the data, the team used state of the art computer codes for analysis. The analysis proved the compact nature of the star and its exotic chemical composition. “The extreme peculiarity of the atmosphere required a lengthy and complex model atmosphere analysis which crunched several weeks of computing time. But the results proved very exciting. Such a peculiar atmosphere devoid of hydrogen and helium is rare indeed,” commented team member Peter Nemeth. The analysis also revealed an extraordinary Galactic trajectory. “The extremely high velocity of this star puts it on a path out of the Milky Way with no return ever,” said team member Lilia Ferrario.
Supernova models and simulations did entertain the possibility of observing surviving stellar remnants in the aftermath of a supernova explosion. The unique object LP40-365 is the first observational evidence for surviving bound remnants of failed supernovae and therefore it is an invaluable object to improve our understanding of these cosmological standard candles.
Many more of these objects are lurking in the Milky Way and awaiting discovery. The recent ESA/Gaia mission may well help us discover many more of these objects and help us understand how a little white dwarf star can survive supernova explosions. | 0.889304 | 4.016537 |
The University of Chicago’s Nicolas Dauphas has developed a new way to calculate the age of the Milky Way that is free of the unvalidated assumptions that have plagued previous methods. Dauphas’ method, which he reports in the June 29 issue of the journal Nature, can now be used to tackle other mysteries of the cosmos that have remained unsolved for decades.
“Age determinations are crucial to a fundamental understanding of the universe,” said Thomas Rauscher, an assistant professor of physics and astronomy at the University of Basel in Switzerland. “The wide range of implications is what makes Nicolas’ work so exciting and important.”
Dauphas, an Assistant Professor in Geophysical Sciences, operates the Origins Laboratory at the University of Chicago. His wide-ranging interests include the origins of Earth’s atmosphere, the oldest rocks that may contain evidence for life on Earth and what meteorites reveal about the formation of the solar system.
In his latest work, Dauphas has honed the accuracy of the cosmic clock by comparing the decay of two long-lived radioactive elements, uranium-238 and thorium-232. According to Dauphas’ new method, the age of the Milky Way is approximately 14.5 billion years, plus or minus more than 2 billion years.
That age generally agrees with the estimate of 12.2 billion years-nearly as old as the universe itself-as determined by previously existing methods. Dauphas’ finding verifies what was already suspected, despite the drawbacks of existing methods: “After the big bang, it did not take much time for large structures to form, including our Milky Way galaxy,” he said.
The age of 12 billion years for the galaxy relied on the characteristics of two different sets of stars, globular clusters and white dwarfs. But this estimate depends on assumptions about stellar evolution and nuclear physics that scientists have yet to substantiate to their complete satisfaction.
Globular clusters are clusters of stars that exist on the outskirts of a galaxy. The processes of stellar evolution suggested that most of the stars in globular clusters are nearly as old as the galaxy itself. When the big bang occurred 13.7 billion years ago, the only elements in the universe were hydrogen, helium and a small quantity of lithium. The Milky Way’s globular clusters have to be nearly that old because they contain mostly hydrogen and helium. Younger stars contain heavier elements that were recycled from the remains of older stars, which initially forged these heavier elements in their cores via nuclear fusion.
White dwarf stars, meanwhile, are stars that have used up their fuel and have advanced to the last stage of their lives. “The white dwarf has no source of energy, so it just cools down. If you look at its temperature and you know how fast it cools, then you can approximate the age of the galaxy, because some of these white dwarfs are about as old as the galaxy,” Dauphas said.
A more direct way to calculate the age of stars and the Milky Way depends on the accuracy of the uranium/thorium clock. Scientists can telescopically detect the optical “fingerprints” of the chemical elements. Using this capability, they have measured the uranium/thorium ratio in a single old star that resides in the halo of the Milky Way.
They already knew how fast uranium and thorium decay with time. If they also know the ratio of uranium and thorium when the star was formed-the production ratio-then calculating the star’s age becomes a problem with a straightforward solution. Unfortunately, “this production ratio is very poorly known,” Dauphas said.
Dauphas solved the problem by combining the data from the uranium/thorium observations in the halo star with measurements of the uranium/thorium ratio that other scientists had made in meteorites. “If you measure a meteorite, you ultimately have the composition of the material that formed the sun 4.5 billion years ago,” he said. And this material included debris from many generations of other stars, now long dead, that still contains information about their own uranium/thorium composition.
“We have very good instruments in the laboratory that allow us to measure this ratio with very, very good precision,” Dauphas said.
Following the change in amount of two sufficiently long-lived radioactive elements is a sensitive way of measuring the time since they were formed, Rauscher said. “The problem is to set the timer correctly, to know the initial amounts of uranium and thorium. By clever combination of abundances in stars and meteorites, Nicolas provides the important starting value for the uranium/thorium clock,” he said.
Scientists can now use that clock to determine the age of a variety of interstellar objects and particles, including cosmic rays, Rauscher said. These subatomic scraps of matter continually bombard the Earth from all directions. Where they come from has baffled scientists for almost a century.
Dauphas’ work may also lead to a better understanding of how stars produce gold, uranium and other heavy elements that play an important role in everyday life, Rauscher said.
From University of Chicago | 0.846872 | 3.967798 |
More than five years ago there was an event that reminded us of a comparison of comets and cats. The media proclaimed comet ISON “the comet of the century.” Experts predicted that it would outshine the full moon. Some said that it would be visible in daylight. Astronomy magazine predicted that it could “become the brightest comet ever seen by anyone now alive.” Excitement was in the air as people waited to see this remarkable comet in the fall of 2013. What happened to it?
Comets have been described as dirty snowballs in space. They consist of water ice, other frozen gasses, and rocks orbiting through the solar system. When they pass near the Sun, the solar radiation vaporizes the solids, and the vapor reflects the sunlight creating a visible ball called a coma. The solar wind causes the appearance of a tail pointing away from the Sun.
The comet that brought such excitement was named ISON after the International Scientific Optical Network based in Russia that initially discovered it. Because its perihelion (closest passage to the Sun) was going to be only 1.8 million kilometers in November of 2013, astronomers expected it to be a rare and “dazzling” sight. However, as the comet came close to the Sun, it disintegrated. What was left instead of being “fifteen times brighter than the full moon” was almost, or entirely, invisible to the naked eye. Star-gazers were disappointed.
Famed comet hunter David Levy made the statement: “Comets are like cats. They have tails, and they do precisely what they want.” Yes, comets and cats are unpredictable. However, one thing we know is that the design of our solar system makes it unlikely that one will collide with Earth. What the Sun doesn’t stop, the “comet sweeper” giant outer planets will—especially Jupiter which captured one of the comets that David Levy discovered. Although Levy said that comets do what they want, it might be more accurate to say that comets do what God wants.
–Roland Earnst ©2019 | 0.86195 | 3.167196 |
Discovering exoplanets with gravitational waves
In a recent paper in Nature Astronomy, researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam and from the French Alternative Energies and Atomic Energy Commission (CEA) in Saclay, Paris suggest how the planned space-based gravitational-wave observatory LISA can detect exoplanets orbiting white dwarf binaries everywhere in the Milky Way and in the nearby Magellanic Clouds. This new method will overcome certain limitations of current electromagnetic detection techniques and might allow LISA to detect planets down to 50 Earth masses.
In the past two decades, the knowledge of exoplanets has grown significantly, and more than 4000 planets orbiting a large variety of stars have been discovered. Up to now, the techniques used to find and characterize these systems are based on electromagnetic radiation and are limited to the solar neighborhood and some parts of the galaxy.
In a recent paper published in Nature Astronomy, Dr. Nicola Tamanini, researcher at the AEI in Potsdam and his colleague Dr. Camilla Danielski, researcher at the CEA/Saclay (Paris) show how these limitations may be overcome by gravitational-wave astronomy. “We propose a method which uses gravitational waves to find exoplanets that orbit binary white dwarf stars,” says Nicola Tamanini. White dwarfs are very old and small remnants of stars once similar to the sun. “LISA will measure gravitational waves from thousands of white dwarf binaries. When a planet is orbiting such a pair of white dwarfs, the observed gravitational-wave pattern will look different compared to the one of a binary without a planet. This characteristic change in the gravitational waveforms will enable us to discover exoplanets.”
The new method exploits the Doppler shift modulation of the gravitational-wave signal caused by the gravitational attraction of the planet on the white dwarf binary. This technique is the gravitational-wave analogue of the radial velocity method, a well-known technique used to find exoplanets with standard electromagnetic telescopes. The advantage, however, of gravitational waves is that they are not affected by stellar activity, which can hamper electromagnetic discoveries.
In their paper, Tamanini and Danielski show that the upcoming ESA mission LISA (Laser Interferometer Space Antenna), scheduled for launch in 2034, can detect Jupiter-mass exoplanets around white dwarf binaries everywhere in the galaxy, overcoming the limitations in distance of electromagnetic telescopes. Furthermore, they point out that LISA will have the potential to detect those exoplanets also in nearby galaxies, possibly leading to the discovery of the first extragalactic bound exoplanet.
“LISA is going to target an exoplanet population yet completely unprobed,” explains Tamanini. “From a theoretical perspective nothing prevents the presence of exoplanets around compact binary white dwarfs.” If these systems exist and are found by LISA, scientists will obtain new data to further develop planetary evolution theory. They will better understand the conditions under which a planet can survive the stellar red-giant phase(s) and will also test the existence of a second generation of planets, i.e., planets that form after the red-giant phase. On the other hand, if LISA does not detect exoplanets orbiting white dwarf binaries, the scientists will be able to set constraints on the final stage of planetary evolution in the Milky Way.
Source:More information: Nicola Tamanini et al. The gravitational-wave detection of exoplanets orbiting white dwarf binaries using LISA, Nature Astronomy(2019). DOI: 10.1038/s41550-019-0807-y | 0.866066 | 3.987 |
Nature Vol. 187 No. 4740. September 3, 1960.
In a contribution(1a) to the Institution of Electrical Engineers Convention on Thermonuclear Processes, of which a somewhat fuller account was published later in Nature(1b), I suggested that the electrical discharge theory of solar flares and the associated magnetic storms and aurorae led to the surprising result that the temperature of these discharges must reach values of the order of 100,000,000° K. some where between the Sun and the Earth's orbit. In another account(1c) of this work, I suggested that this need not come as too great a surprise, as temperatures of the order of 1,000,000°K. had been obtained some years earlier in electrical discharges in the laboratory (I. V. Kurchatov, Moacow, 1956), and for long have been known to exist in the solar corona.
Furthermore, a similar increase in temperature is observed when long electrical discharges are propagated down the corresponding, but lesser, density gradients in some stellar atmospheres -- those of the combination spectra stars, such as Z Andromedae and AX Persei, for example. In these, the temperature is initially that leading to the ionization of the metals, hydrogen and helium, that is, probably of the order of 5,000° or 10,000°K. However, by the time the discharge reaches the outer regions of these stellar atmospheres, after periods of the order of 100-200 days, the discharge temperature reaches values of the order of 1,000,000°K. as lines of Fe X and Fe XIV appear in the star's spettra.
Though there was thus some additional theoretical support for the surprising conclusions to which the theory led when applied to these solar phenomena, it is satisfactory to learn that satellite observations made by the U.S. Navy scientists have confirmed(2) that these high temperatures do exist in the disturbances associated with solar flares. As I emphasized many years ago(1d), it is difficult to see how these high temperatures can be built up by any other mechanism, than that of an electrical discharge.
Similar temperatures are reached in galactic electric discharges, and can be measured, as I have suggested, by the proposed 'cosmic gas-velocity thermometer'(1e), of which the basic conception is that these high gas velocities observed in stars and galaxies are always the result of electrical discharges, the velocities of these jets being linked closely with their temperatures(1f), in contradistinction to the assumptions often made in other accounts of these solar jets(3). The only limit to the discharge temperature will be the onset of thermonuclear processes(1g).
On the electrical discharge theory of galactic evolution(1d,g) the main difference between the gas which ultimately forms Population I stars, and that which originally formed Population II stars, is that the former has been subjected to 'thermonuclear temperatures' of the order of 400,000,000°K. for a period of the order of 10-100 million years, during the formation of the spiral arms. It may be, therefore, that it is this difference which has led to the difference in the proportions of the heavier elements observed in these two stellar populations. It is not easy to visualize all the physical characteristics of electrical discharges on such a scale as that envisaged, but at present the value of n, the number of atoms per cm3 of the galactic atmosphere, required to effect the observed chemical change in the time available, appears to be too high. However, it would be interesting to have comments on this suggested explanation of this difference between the two stellar populations.
C. E. R. Bruce
Electrical Research Association; Leatherhead, Surrey. | 0.864686 | 3.884737 |
How you can see 5 planets, no telescope required
Get ready to spot Mercury, Venus, Jupiter, Saturn and Mars — and grab binoculars if you can
The night sky is just bursting with planets.
It's the perfect time of the year to do some planet hunting. If you have sharp eyes, you will be able to spot five in the same night.
The fun starts just after sunset.
Mercury can be a challenging target. Because it's so close to the sun, it's often lost in its glare. Also, because the tiny planet is only visible near the sun, it can only be seen after sunset or before sunrise. It can easily get lost in the murk that often occurs along the horizon.
On July 15, Mercury sets just more than an hour after the sun, so you have some time to find it. Here's the best part: you'll have a crescent moon to use as a guide.
First, try to get somewhere high. If you're in a city, you're not going to have much luck finding it. Try going to a park with a hill and an unobstructed view of the western horizon.
The moon will be only be roughly 10 per cent illuminated, forming a beautifully thin crescent in the west next to Venus.
From there, Mercury is about 15 degrees lower and to the right. You can use your fingers to measure the distance.
You can continue to view Mercury for the following week, but as it gets closer to the sun, it will be much harder to see.
(You can find the rise and set times for the planets in your town or city using the site timeanddate.com.)
If you're using binoculars, remember to never, ever point them directly at the sun.
You can't miss Venus. You've likely already noticed the planet in the western sky just after sunset.
Venus is so bright, oftentimes it's mistaken for a plane or even a UFO. When it's visible, the planet is the brightest object in the night sky.
Like Mercury, its orbit is closer to the sun than Earth (these are referred to as the "inferior" planets), so Venus is visible before and after sunrise, depending on where it is in its orbit. That's why you may have heard the planet referred to as either an "evening star" or "morning star."
On July 15, the crescent moon and Venus make a gorgeous pair in the western sky. With the moon only roughly 10 per cent illuminated, it's easy to spot the "evening star" just two degrees to the left of it. Actually, if you want to give yourself a challenge, on this day, try finding Venus before the sun sets, using the moon as a guide. You can always try and use binoculars, too, but half the fun is finding it with the naked eye.
For the next few months, you can find Venus in the sky after sunset, though it will be lower on the horizon as the days go on. By October, it will disappear for a couple of months. It will emerge again as a "morning star" in the new year.
The king of our solar system has been dominant in the sky since April.
Now you can find Jupiter, which is usually second-brightest to Venus, high in the southwest after sunset.
On the night of the 15th, if you have a chance, look at Jupiter with a pair of binoculars; 7x50s would be best, but you can try with whatever you have.
Don't expect to see details, but you can see four of the planet's largest moons: Callisto, Ganymede, Io and Europa.
Moving inward, Callisto will be the farthest out of the four Galilean moons, to the "west" or left of the planet, followed by Ganymede. Then Io and Europa follow, much closer to Jupiter (you may not be able to spot Europa as it will be quite close to Jupiter).
Go outside the next day and look again. You will see the moons have moved position. On the 16th, Callisto and Io are on the left of the planet, with Ganymede and Europa to the right.
Saturn, the ringed beauty, also joins Jupiter in the southern sky. After sunset, look to the south and you'll notice a "star" that is somewhat dimmer than Jupiter. That's Saturn.
The planet is positioned in the south right above the "teapot" of the constellation Sagittarius.
If you happen to look at it through binoculars, it won't be the planet that wows you, but the multitude of stars. That's because Saturn lies in one of the richest parts of our night sky — the thickest part of the Milky Way.
Well, Mars is the big star this month (so to speak) and will continue to be so into August. It is the closest and brightest it's been since August 2003. Earlier this month it even outshone Jupiter (but not by a lot).
But there's a global dust storm going on at Mars, and it's not quite clear how it will affect its brightness.
You can find the Red Planet blazing a brilliant red in the southeastern sky. It will rise just after 10 p.m. ET in the east. It will continue to get higher in the sky, as it rises earlier. Go and take a look: it is roughly five times brighter than normal.
If you're ever looking at the sky wondering what exactly it is you're seeing, there are great apps for both Androids and iPhones to help, including Sky Safari, Sky View, Star Walk and Stellarium (fee). They allow you to point your phone at the sky and identify objects. Tap and you can learn more about the object.
And here's an added bonus to your planet viewing: the annual Perseid meteor shower is set to peak on Aug. 13, with only five per cent of the moon illuminated. With the planets, it should be quite a show. Mark your calendars! | 0.904099 | 3.303159 |
Gravity pulls everything together, right? We grow up learning and understanding this basic scientific rule.
But if that’s so, why is the expansion of the universe speeding up instead of slowing down?
“It’s like throwing your car keys in the air and having them accelerate upwards and disappear from sight,” said David Weinberg, Ph.D., chair of the Department of Astronomy at The Ohio State University. Weinberg is hoping that NASA’s Wide Field Infrared Survey Telescope (WFIRST) will play a central role in resolving this puzzle after it launches in the mid-2020s.
“The most distant objects in the universe are accelerating away from us,” Weinberg said. “This is a very surprising phenomenon, and we want to understand why it’s happening. It’s the biggest mystery in cosmology today.”
For the past five years, Weinberg – whose own research has been buoyed by the Ohio Supercomputer Center for the past 15 years – has been on NASA’s Science Definition Team for the preliminary study of WFIRST along with Ohio State colleagues Scott Gaudi and Chris Hirata. After that preliminary study, NASA announced in February it would move forward with the WFIRST mission.
“It’s definitely been exciting to be a part of,” Weinberg said. “To finally have an official start is great for all the people who have been working on this mission.”
The new space telescope is moving into construction just as the James Webb Space Telescope (JWST), which has a much larger mirror but observes only a tiny patch of sky at a given time, approaches its launch in 2018.
“’Wide field’ means that WFIRST sees a lot of the sky at one time, and this is where it’s different in important ways from the Hubble Space Telescope, or from JWST,” Weinberg said. “WFIRST images the sky in infrared light and measures spectra of galaxies and stars, and it can do that 200 times faster than Hubble can.”
WFIRST has three defining goals: understanding the origin of accelerating cosmic expansion, making a census of planets around other stars through gravitational microlensing, and directly imaging giant planets around the closest stars. Hirata and Weinberg are most closely involved with the first study. “We are hoping to crack the problem by measuring expansion and clustering much better than anyone has done before, with an accuracy of about 0.1 percent,” Weinberg said.
Gaudi is the principal investigator of the planetary microlensing program, which will monitor an area of sky near the center of the Galaxy in a series of 2-month campaigns, totaling more than a year. This approach to planet hunting was pioneered in the 1990s by Gaudi’s thesis advisor, Ohio State astronomer Andrew Gould.
When two stars align almost perfectly, the gravity of the foreground star focuses the light of the background star like a magnifying glass in front of a candle flame. A planet orbiting the foreground star disturbs the magnification, allowing detection of the planet and an approximate measurement of its mass.
"Microlensing is currently the most sensitive method for finding planets in orbits from their parent stars that are further than that of the Earth," Gaudi was quoted as saying in an Ohio State University article, “but it relies on extremely rare alignments, so after many years of ground-based searches we still have only a few dozen detected planets.”
WFIRST will combine a wide, clear view from space with ultra-sensitivity to infrared light, giving it the unprecedented ability to detect thousands of microlensing planets.
Along with Ohio State’s strong connection to the project, the Ohio Supercomputer Center helped lay some groundwork and could be instrumental in the future.
The OSU research team has pursued many projects with OSC. Hirata has used OSC systems housing the Center of Cosmology and Astro Particle Physics condo. Gould – a longtime user – currently has a personal project titled Finding Planets by Intensive Modeling of Gravitational Microlensing Events. Weinberg has used OSC services for 15 years and has two personal projects: Pinpointing the Physics of a Key Dark Energy Probe and Connecting Mergers of Supermassive Black Holes and Their Formation During Hierarchical Galaxy Assembly.
Weinberg said OSC has assisted in a strong but indirect way with the WFIRST project. He said his own scientific work is mostly about understanding the formation of galaxies and the large-scale structure of the universe.
“A lot of this work has been doing supercomputer simulations of formation of galaxies and of large-scale structures in which we start with small fluctuations we expect to be present in the early universe and use computers to calculate the effects of gravity,” he said. “This is a very computation-heavy field and it’s aimed at making predictions for the kinds of things WFIRST will measure.”
Weinberg’s students Ben Wibking and Andres Salcedo are carrying out calculations at OSC to make highly precise predictions of gravitational lensing by galaxies and clusters of galaxies, and of the clustering of galaxies themselves.
“Right now we’re doing this with our eyes on the ground-based Dark Energy Survey,” Weinberg said, “but the same framework should be applicable to WFIRST. Over the next five years, we’re going to be using OSC computers to help us develop the tools that we’re going to use to analyze WFIRST data when it arrives, and to define how the telescope needs to work in order to produce the science that we want.”
Written by Ross Bishoff | 0.897116 | 3.792878 |
A Southwest Research Institute scientist modeled the atmosphere of Mars to help determine that salty pockets of water present on the Red Planet are likely not habitable by extant Earth life forms. A team that also included scientists from Universities Space Research Association (USRA) and the University of Arkansas helped allay planetary protection concerns about contaminating potential Martian ecosystems.
The results are described in "Distribution and Habitability of (Meta)stable Brines on Present-Day Mars," published in Nature Astronomy.
Due to Mars' low temperatures and extremely dry conditions, a droplet of liquid water on its surface would instantly freeze, boil, or evaporate, unless the droplet had dissolved salts in it. This brine would have a lower freezing temperature and would evaporate more slowly than pure liquid water. Salts are found across Mars, so brines could form there.
"Our team looked at specific regions on Mars — areas where liquid water temperature and accessibility limits could possibly allow known terrestrial organisms to replicate — to understand if they could be habitable," says Alejandro Soto, a Southwest Research Institute senior research scientist and co-author of the study. "We used Martian climate information from both atmospheric models and spacecraft measurements. We developed a model to predict where, when, and for how long brines are stable on the surface and shallow subsurface of Mars."
Mars' hyper-arid conditions require lower temperatures to reach high relative humidities and tolerable water activities, which are measures of how easily the water content may be utilized for hydration. The maximum brine temperature expected is -55 F — at the boundary of the theoretical low temperature limit for life.
"Even extreme life on Earth has its limits, and we found that brine formation from some salts can lead to liquid water over 40% of the Martian surface but only seasonally, during 2% of the Martian year," Soto says. "This would preclude life as we know it."
While pure liquid water is unstable on the Martian surface, models showed that stable brines can form and persist from the equator to high latitudes on the surface of Mars for a few percent of the year for up to six consecutive hours, a broader range than previously thought. However, the temperatures are well below the lowest temperatures to support life.
"These new results reduce some of the risk of exploring the Red Planet while also contributing to future work on the potential for habitable conditions on Mars," Soto says.
Co-authors of the Nature Astronomy study are Edgard G. Rivera-Valentín, with the Lunar and Planetary Institute, Universities Space Research Association, Vincent F. Chevrier, with the Arkansas Center for Space and Planetary Sciences, University of Arkansas, and Germán Martínez, with the Lunar and Planetary Institute, and the Department of Climate and Space Sciences and Engineering, University of Michigan. The SwRI portion of this research was funded by NASA under the Habitable Worlds program through a grant led by USRA.
No entries found | 0.883915 | 3.961217 |
Gibbous ♒ Aquarius
Moon phase on 20 September 2018 Thursday is Waxing Gibbous, 10 days young Moon is in Aquarius.Share this page: twitter facebook linkedin
Previous main lunar phase is the First Quarter before 3 days on 16 September 2018 at 23:15.
Moon rises in the afternoon and sets after midnight to early morning. It is visible to the southeast in early evening and it is up for most of the night.
Moon is passing about ∠6° of ♒ Aquarius tropical zodiac sector.
Lunar disc appears visually 7.8% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1911".
Next Full Moon is the Harvest Moon of September 2018 after 4 days on 25 September 2018 at 02:53.
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 10 days young. Earth's natural satellite is moving from the first to the middle part of current synodic month. This is lunation 231 of Meeus index or 1184 from Brown series.
Length of current 231 lunation is 29 days, 9 hours and 45 minutes. It is 2 hours and 30 minutes shorter than next lunation 232 length.
Length of current synodic month is 2 hours and 59 minutes shorter than the mean length of synodic month, but it is still 3 hours and 10 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠28°. At beginning of next synodic month true anomaly will be ∠49.6°. 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°).
Moon is reaching point of apogee on this date at 00:54, this is 11 days after last perigee on 8 September 2018 at 01:21 in ♌ Leo. Lunar orbit is starting to get closer, while the Moon is moving inward the Earth for 15 days ahead, until it will get to the point of next perigee on 5 October 2018 at 22:29 in ♌ Leo.
This apogee Moon is 404 875 km (251 578 mi) away from Earth. It is 533 km farther than the mean apogee distance, but it is still 1 834 km closer than the farthest apogee of 21st century.
Moon is in descending node in ♒ Aquarius at 09:30 on this date, it crosses the ecliptic from North to South. Moon will follow the southern part of its orbit for the next 13 days to meet ascending node on 4 October 2018 at 03:10 in ♌ Leo.
13 days after beginning of current draconic month in ♋ Cancer, the Moon is moving from the middle to the last part of it.
2 days after previous South standstill on 18 September 2018 at 09:35 in ♑ Capricorn, when Moon has reached southern declination of ∠-20.909°. Next 12 days the lunar orbit moves northward to face North declination of ∠21.037° in the next northern standstill on 2 October 2018 at 13:03 in ♋ Cancer.
After 4 days on 25 September 2018 at 02:53 in ♈ Aries, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.048784 |
Mars Science Laboratory, launched three days ago on the morning of Saturday, November 26, is currently on its way to the Red Planet – a journey that will take nearly nine months. When it arrives the first week of August 2012, MSL will begin investigating the soil and atmosphere within Gale Crater, searching for the faintest hints of past life. And unlike the previous rovers which ran on solar energy, MSL will be nuclear-powered, generating its energy through the decay of nearly 8 pounds of plutonium-238. This will potentially keep the next-generation rover running for years… but what will fuel future exploration missions now that NASA may no longer be able to fund the production of plutonium?
Pu-238 is a non-weapons-grade isotope of the radioactive element, used by NASA for over 50 years to fuel exploration spacecraft. Voyagers, Galileo, Cassini… all had radioisotope thermoelectric generators (RTGs) that generated power via Pu-238. But the substance has not been in production in the US since the late 1980s; all Pu-238 has since been produced in Russia. But now there’s only enough left for one or two more missions and the 2012 budget plan does not yet allot funding for the Department of Energy to continue production.
Where will future fuel come from? How will NASA power its next lineup of robotic explorers? (And why aren’t more people concerned about this?)
When leaving our fair planet, mass is everything. Space being a harsh place, you must bring nearly everything you need, including fuel, with you. And yes, more fuel means more mass, means more fuel, means… well, you get the idea. One way around this is to use available solar energy for power generation, but this only works well in the inner solar system. Take a look at the solar panels on the Juno spacecraft bound for Jupiter next month… those things have to be huge in order to take advantage of the relatively feeble solar wattage available to it… this is all because of our friend the inverse square law which governs all things electromagnetic, light included.
To operate in the environs of deep space, you need a dependable power source. To compound problems, any prospective surface operations on the Moon or Mars must be able to utilize energy for long periods of sun-less operation; a lunar outpost would face nights that are about two Earth weeks long, for example. To this end, NASA has historically used Radioisotope Thermal Generators (RTGs) as an electric “power plant” for long term space missions. These provide a lightweight, long-term source of fuel, generating from 20-300 watts of electricity. Most are about the size of a small person, and the first prototypes flew on the Transit-4A & 5BN1/2 spacecraft in the early 60’s. The Pioneer, Voyager, New Horizons, Galileo and Cassini spacecraft all sport Pu238 powered RTGs. The Viking 1 and 2 spacecraft also had RTGs, as did the long term Apollo Lunar Surface Experiments Package (ALSEP) experiments that Apollo astronauts placed on the Moon. An ambitious sample return mission to the planet Pluto was even proposed in 2003 that would have utilized a small nuclear engine.
David goes on to mention the undeniable dangers of plutonium…
Plutonium is nasty stuff. It is a strong alpha-emitter and a highly toxic metal. If inhaled, it exposes lung tissue to a very high local radiation dose with the attending risk of cancer. If ingested, some forms of plutonium accumulate in our bones where it can damage the body’s blood-forming mechanism and wreck havoc with DNA. NASA had historically pegged a chance of a launch failure of the New Horizons spacecraft at 350-to-1 against, which even then wouldn’t necessarily rupture the RTG and release the contained 11 kilograms of plutonium dioxide into the environment. Sampling conducted around the South Pacific resting place of the aforementioned Apollo 13 LM re-entry of the ascent stage of the Lunar Module, for example, suggests that the reentry of the RTG did NOT rupture the container, as no plutonium contamination has ever been found.
Yet the dangers of nuclear power often overshadow its relative safety and unmistakable benefit:
The black swan events such as Three Mile Island, Chernobyl and Fukushima have served to demonize all things nuclear, much like the view that 19thcentury citizens had of electricity. Never mind that coal-fired plants put many times the equivalent of radioactive contamination into the atmosphere in the form of lead210, polonium214, thorium and radon gases, every day. Safety detectors at nuclear plants are often triggered during temperature inversions due to nearby coal plant emissions… radiation was part of our environment even before the Cold War and is here to stay. To quote Carl Sagan, “Space travel is one of the best uses of nuclear weapons that I can think of…”
Yet here we are, with a definite end in sight to the supply of nuclear “weapons” needed to power space travel…
Currently, NASA faces a dilemma that will put a severe damper on outer solar system exploration in the coming decade. As mentioned, current plutonium reserves stand at about enough for the Mars Science Laboratory Curiosity, which will contain 4.8kilograms of plutonium dioxide, and one last large & and perhaps one small outer solar system mission. MSL utilizes a new generation MMRTG (the “MM” stands for Multi-Mission) designed by Boeing that will produce 125 watts for up to 14 years. But the production of new plutonium would be difficult. Restart of the plutonium supply-line would be a lengthy process, and take perhaps a decade. Other nuclear based alternatives do indeed exist, but not without a penalty either in low thermal activity, volatility, expense in production, or short half life.
The implications of this factor may be grim for both manned and unmanned space travel to the outer solar system. Juxtaposed against at what the recent 2011 Decadal Survey for Planetary Exploration proposes, we’ll be lucky to see many of those ambitious “Battlestar Galactica” –style outer solar system missions come to pass.
Landers, blimps and submersibles on Europa, Titan, and Enceladus will all operate well out of the Sun’s domain and will need said nuclear power plants to get the job done… contrast this with the European Space Agency’s Huygens probe, which landed on Titan after being released from NASA’s Cassini spacecraft in 2004, which operated for scant hours on battery power before succumbing to the -179.5 C° temps that represent a nice balmy day on the Saturnian moon.
So, what’s a space-faring civilization to do? Certainly, the “not going into space” option is not one we want on the table, and warp or Faster-Than-Light drives a la every bad science fiction flick are nowhere in the immediate future. In [my] highly opinionated view, NASA has the following options:
Exploit other RTG sources at penalty. As mentioned previously, other nuclear sources in the form of Plutonium, Thorium, and Curium isotopes do exist and could be conceivably incorporated into RTGs; all, however, have problems. Some have unfavorable half-lives; others release too little energy or hazardous penetrating gamma-rays. Plutonium238 has high energy output throughout an appreciable life span, and its alpha particle emissions can be easily contained.
Design innovative new technologies. Solar cell technology has come a long way in recent years, making perhaps exploration out to the orbit of Jupiter is do-able with enough collection area. The plucky Spirit and Opportunity Mars rovers(which did contain Curium isotopes in their spectrometers!) made do well past their respective warranty dates using solar cells, and NASA’s Dawn spacecraft currently orbiting the asteroid Vesta sports an innovative ion-drive technology.
Push to restart plutonium production. Again, it is not that likely or even feasible that this will come to pass in today’s financially strapped post-Cold War environment. Other countries, such as India and China are looking to “go nuclear” to break their dependence on oil, but it would take some time for any trickle-down plutonium to reach the launch pad. Also, power reactors are not good producers of Pu238. The dedicated production of Pu238 requires either high neutron flux reactors or specialized “fast” reactors specifically designed for the production of trans-uranium isotopes…
Based on the realities of nuclear materials production the levels of funding for Pu238 production restart are frighteningly small. NASA must rely on the DOE for the infrastructure and knowledge necessary and solutions to the problem must fit the realities within both agencies.
And that’s the grim reality of a brave new plutonium-free world that faces NASA; perhaps the solution will come as a combination of some or all of the above. The next decade will be fraught with crisis and opportunity… plutonium gives us a kind of Promethean bargain with its use; we can either build weapons and kill ourselves with it, or we can inherit the stars.
Thanks to David Dickinson for the use of his excellent article; be sure to read the full version on his Astro Guyz site here (and follow David on Twitter @astroguyz.) Also check out this article by Emily Lakdawalla of The Planetary Society on how the RTG unit for Curiosity was made.
“There are some people who legitimately feel like this is simply not a priority, that there’s not enough money and it’s not their problem. But I think if you try to step back and look at the forest and not just the individual trees, this is one of the things that has helped drive us to become a technological powerhouse. What we’ve done with robotic space exploration is something that people not just in the U.S., but around the world, can look up to.”
– Ralph McNutt, planetary scientist at Johns Hopkins University’s Applied Physics Laboratory (APL)
( Top image credit © 2011 Theodore Gray periodictable.com; used with permission.) | 0.879181 | 3.15937 |
A new radio telescope in South Africa has just been switched on for the first time, and the inaugural image taken by it is jaw-droppingly spectacular.
The telescope is called MeerKAT, and it consists of 64 radio dishes, each 13.5 meters across. That’s not a very large aperture, to be honest — there are far larger radio dishes — but these are spread out over a large area and are designed to work together. When their powers are combined they can reproduce the resolution of a far, far larger telescope.
The first target chosen was a solid choice: the center of our galaxy, where there is a lot to see.
A lot. Look:
Holy yikes. So yeah, this’ll take some explaining.
The size of the image is about 1° x 2°, or very roughly the amount of sky covered by the last phalange of your pinky held at arm’s length. For a telescope, that’s a big chunk of sky. And looking toward the center of the Milky Way is like looking downtown from the suburbs; it’s a happening place.
First, we’re seeing radio waves here. This is a form of light like the kind we see, but with much longer wavelengths. It’s emitted by all kinds of cosmic objects, including gas, dust, stars, and so on. Almost everything you see in this image is gas, but the reason the different sources emit radio waves differ.
For example, the circular structures on the left are caused by violently expanding gas blasted out from exploding stars. This supernova debris slams into the gas around it, exciting it, and causing it to glow. In some of them you can see some asymmetry, where the edge is brighter in certain spots than others. In general, this is because there’s more ambient gas in that direction, and as it piles up it emits more light.
The intensely bright spot to the right of center is the very core of our Milky Way, where a supermassive black hole sits. Surrounding this black hole is a lot of gas, dust, and stars, and these are quite bright in radio waves.
To the left of that is another bright streak of light; this is actually several parallel arched filaments of gas that may be associated with a dense cluster of stars called the Arches Cluster. To the left of that are two bright blobs (called SGR B2 on the left and SGR B1 on the right); these are molecular clouds, dense clots of cold gas and dust busily forming stars.
Which brings us to the weirdest part of this image: all those bright, narrow threads lying everywhere across the shot. Many of these were discovered in the 1980s, and thought to be dust that was aligned with the Milky Way’s magnetic field — much as iron filings align themselves along a bar magnet’s field. But then in the early 2000s better images were taken and it was shown they didn’t all align with the galaxy’s magnetic field. Instead, they seem to align with regions of vigorous star formation, where dense knots of gas are churning out baby stars. These stellar nurseries have magnetic fields themselves, and these may be what are focusing those threads. Mind you, they’re huge; the filaments are up to 100 light years long, a thousand trillion kilometers! Yet for that, they are only a few light years wide, so they are indeed very narrow.
I’m very impressed by MeerKAT’s ability to resolve these filaments! The galactic center is pretty chaotic and messy, and difficult to study. On top of that, all that gas and dust absorbs light at visible wavelengths (the kind of light we see), so we have to rely on other wavelengths to understand what’s going on, and telescopes don’t always have the best resolution at those parts of the electromagnetic spectrum. MeerKAT is changing that.
And this is just the start. MeerKAT is just a precursor to a proposed much larger array of radio dishes called the Square Kilometer Array, or SKA, which is planned to have thousands of such dishes! The “square kilometer” part doesn’t refer to how spread out it is, but the actual physical area of the combined dishes; it will be spread out over thousands of square kilometers of South Africa and Australia. It promises a huge leap forward in radio astronomy, with much higher resolution and ability to see faint sources than any other telescope. MeerKAT, as amazing as it is, will be incorporated into SKA and be just one part of a vastly larger system.
Scheduled construction for SKA begins next year, with Phase I observations planned for 2022. However, the future of the project seems a bit iffy. There are budgetary issues, and it’s unclear how much of the array will get built, when, and what it will actually be. I’ll be keeping my eye on this and I’ll write an update when I know more. | 0.897399 | 3.852013 |
REXUS 3 Experiment overview
Project ARCHIMEDES is a joint effort of the Mars Society Germany, the University of the German Federal Armed Forces in Munich, the University of Stuttgart and others with the goal to built a spacecraft capable of probing the atmosphere of planet Mars from its thin outermost layers down to the surface. This goal will be achieved by deploying a spherical super-pressure - type balloon prior to atmospheric entry.
The flight on a sounding rocket can close an important gap between previous parabolic flight and orbit, namely by putting the system in space just long enough for the balloon package to be ejected and to start expanding under the pressure of its own protective gas filling. The experiment starts when the payload section of the rocket enters 0-g. It should be mounted at a free end of the payload section, preferably at the opposite end of the recovery system. After entry into the 0-g phase the separation mechanism is triggered, and in a safe distance the deployment mechanism. Cameras that are left in the payload section record the separation and deployment, and can be recovered with the other payload.
Combined mass: Approx. 30kg incl. batteries and structure.
The T-Rex project at the Institute of Astronautics started in April 2005 as a part of the practical course “Space Technology”. The task was to develop and construct an experiment that can be placed on the Rexus-Rocket. Soon it was clear that the main focus of the experiment existed in finding accelerometers, which are really cheap but still able to survive in space. Three main requirements where found:
• Measure accelerations as best as possible
• Use low cost elements
• Assure a safe operation
Several acceleration sensor principles have been considered and led to the selection of capacitive accelerometers. In the end, accelerometer choice was mainly based on low cost and thus, summing all up, T-Rex now fly with 3 x 3 Freescale accelerometers. The chosen products are:
• Freescale MMA3201D 2 channels +/- 40g
• Freescale MMA1250D 1 channel +/- 5g
• Freescale MMA6233Q 2 channels +/- 10g
As within these chosen sensors are no three-dimensional units, measuring all three axes will be achieved through appropriate set-up on the circuit boards. Three independent circuit boards will be used, each carrying three different sensors and a complete set of data processing units. The sampling rate is 2 kHz per channel. The data is stored in solid flash devices and will be partially transmitted over downlink for redundancy.
The goal of this experiment is to test the sensors and in particular the optics during supersonic flight and measure the interconnected heating of the hardware. The Camera Hardware is capable of storing the temperature of the rocket casing. This information is added to the picture data. Because of unpredictable changing illumination ratios during the flight, the camera is recording pictures with cyclical changing exposure times. The picture data will be ordered by different brightness values after the flight and processed for colour matching. Maybe equalization will be also applied. After this process the data will be assembled to an animation.
The experiment is operated by the University of Berlin.
TUPEX is an experimental platform to design and test components especially used in pico satellites. The experiment is operated by the Technical University of Berlin.
The objective is to test the functionality of solar cells, several commercial sensors and a self-developed sun sensor for attitude determination in respect to the sun.
TUPEX consists of a main box and two solar boards. The main box includes a measurement value logging unit and several sensors (3 gyros, 2 two-axis accelerometers, 1 three-axis magnetometer, 5 temperature sensors). The solar boards include a triple junction GaAs solar cell, a sun sensor and a temperature sensor.
During flight all acquired values are stored on flash memory and transmitted to ground station via rocket communication link simultaneously.
IAP Particle detector
The instrument package for the REXUS-sounding rocket campaign at the ESRANGE in April 2006 provided by the Leibniz Institute of Atmospheric Physics at the University of Rostock consists of a total of 4 instruments: The two simple particle detectors are flat electrode surfaces mounted flash with the rocket payload skin. Strong NeFeBo-magnets (field strength ~0.4 T) are embedded into the electrode structure to prevent electrons and ions from contributing to the measured signal.
The two fixed biased Langmuir sondes have a similar geometry, however, instead of using magnets in order to shield the electrodes from the ambient plasma, the electrode surfaces are biased at +4.5 V (-4.5V) in order to measure electrons (positive ions).
Hard Disc Drive, Rexus Rocket of Rymdgymnasiet
Upper secondary space school, Kiruna
The purpose of the experiment is to analyze how a micro hard drive in a modern MP3-player is affected by the environment in space. Is it possible for a hard drive to function after it has been exposed to high acceleration, low gravity and no air pressure?
The micro hard drive MP3-player Iriver H10, sponsored by Iriver Nordic and encouraged by the Swedish tech magazine M3.
The player can maybe expose electromagnetic fields but it will be reduced by the protective box, the box shields frequencies from 5 Hz up to 1800 MHz.
The player will be examined prior to launch that it functions correctly. An error check will be done on the hard drive using the error check tool in Windows for hard drives. Hard drive info will also be obtained from another application not yet decided, probably Partition Magic.
During the flight the built in FM radio will provide static noise to be recorded on the hard disc.
The examinations after the trip to space will be first of all controlling if the player starts and can play the recorded noise. After that an error check will be performed in Windows followed by a more detailed scan by a proper application, probably Partition Magic. In any case if the player starts or does not start, I will through eventual sponsorship agreements try to send the player to computer laboratories or technical universities for further technically advanced examinations, if needed.
The MEMS experiment, built by a Norwegian team.
The use of MEMS (Micro Electro Mechanical System) is one step forward towards the miniaturization of electronic systems used in space. Angular rate sensors and accelerometers based on different MEMS technologies are today available from several companies. We will focus on sensors from SensoNor, Analog Devices and MEMSIC which are all using different sensing technologies. These sensing technologies are based on vibrating silicon structure (gyro), capacitive comb structure (accelerometer) and natural heat convection (accelerometer) respectively.
MEMSIC accelerometers do not depend on moving mechanical parts. The principle of operation of the accelerometers is based on heat transfer by natural convection, and they measure internal changes in heat transfer caused by acceleration. This new technology provides shock survival up to 50.000g and eliminates stiction and particle failures that commonly exist in all traditional capacitive sensors.
The SensoNor SAR10 angular rate gyro is a silicon bulk micromachined capacitive device, consisting of a vibrating silicon structure sensor element and an ASIC integrated in a SOIC package. The principal of operation of the sensor is based on the detection of Coriolis force. Excellent gyroscopic scale factor, offset and vibration sensitivity is achieved due to anti phase operation.
The Analog Devices accelerometers are a well proven capacitive technology and are frequently used nowadays.
To achieve the most accurate measurements possible, these sensors will be placed at different angles and positions inside the payload. Several of the sensors will be running in parallel during the flight so a direct comparison of the different sensor outputs should be easily achievable. A number of microcontrollers will collect all the information from the sensors and direct it to the encoder unit.
The primary objective of the experiment is to investigate our sensors behavior in the harsh environment of the interior of a sounding rocket. The goal is to determine if they are good enough to be considered for future space applications. Different sensors are set up to measure the spin and coning of the rocket, acceleration in the longitudinal direction and the vibration subjected to the circuit box. If the experiment proves successful, these sensors can make up a measurement system witch can be used to evaluate the behavior of the rocket during its flight | 0.808439 | 3.064975 |
Aryabhata (476–550 CE) was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy. His most famous works are the Aryabhatiya (499 CE, when he was 23 years old) and the Arya-siddhanta.
He studied at the University of Nalanda. One of his major work was Aryabhatiya written in 499 AD. The book dealt with many topics like astronomy, spherical trigonometry, arithmetic, algebra and plane trigonometry. He jotted his inventions in mathematics and astronomy in verse form. The book was translated into Latin in the 13th century. Through the translated Latin version of the Aryabhattiya, the European mathematicians learned how to calculate the areas of triangles, volumes of spheres as well as how to find out the square and cube root.
In the field of astronomy, Aryabhatta was the pioneer to infer that the Earth is spherical and it rotates on its own axis which results in day and night. He even concluded that the moon is dark and shines because of the light of sun. He gave a logical explanation to the theory of solar and lunar eclipses. He declared that eclipses are caused due to the shadows casted by the Earth and the moon. Aryabhatta proposed the geocentric model of the solar system which states that the Earth is in the center of the universe and also laid the foundation for the concept of Gravitation. His propounded methods of astronomical calculations in his Aryabhatta-Siddhatha which was used to make the the Panchanga (Hindu calendar). What Copernicus and Galileo propounded was suggested by Aryabhatta nearly 1500 years ago.
Aryabhatta’s contribution in mathematics is unparalleled. He suggested formula to calculate the areas of a triangle and a circle, which were correct. The Gupta ruler, Buddhagupta, appointed him the Head of the University for his exceptional work. Aryabhatta gave the irrational value of pi. He deduced ? = 62832/20000 = 3.1416 claiming, that it was an approximation. He was the first mathematician to give the ‘table of the sines’, which is in the form of a single rhyming stanza, where each syllable stands for increments at intervals of 225 minutes of arc or 3 degrees 45′. Alphabetic code has been used by him to define a set of increments. If we use Aryabhatta’s table and calculate the value of sin(30) (corresponding to hasjha) which is 1719/3438 = 0.5; the value is correct. His alphabetic code is commonly known as the Aryabhata cipher. | 0.824002 | 3.099679 |
Image credit: ESO
On March 29, 2003 NASA’s High Energy Transient Explorer detected a bright burst of gamma rays, and shortly after telescopes from around the world focused in on the object; now called GRB 030329 and measured to be 2.6 billion light-years away. By measuring the afterglow of the explosion, astronomers realized that it matches the spectrum of a hypernova – explosions of extremely large stars, at least 25 times larger than our own Sun. By matching the spectra, astronomers have compelling evidence that there is some connection between gamma ray bursts and the explosions of very large stars.
A very bright burst of gamma-rays was observed on March 29, 2003 by NASA’s High Energy Transient Explorer (HETE-II), in a sky region within the constellation Leo.
Within 90 min, a new, very bright light source (the “optical afterglow”) was detected in the same direction by means of a 40-inch telescope at the Siding Spring Observatory (Australia) and also in Japan. The gamma-ray burst was designated GRB 030329, according to the date.
And within 24 hours, a first, very detailed spectrum of this new object was obtained by the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile). It allowed to determine the distance as about 2,650 million light-years (redshift 0.1685).
Continued observations with the FORS1 and FORS2 multi-mode instruments on the VLT during the following month allowed an international team of astronomers to document in unprecedented detail the changes in the spectrum of the optical afterglow of this gamma-ray burst. Their detailed report appears in the June 19 issue of the research journal “Nature”.
The spectra show the gradual and clear emergence of a supernova spectrum of the most energetic class known, a “hypernova”. This is caused by the explosion of a very heavy star – presumably over 25 times heavier than the Sun. The measured expansion velocity (in excess of 30,000 km/sec) and the total energy released were exceptionally high, even within the elect hypernova class.
From a comparison with more nearby hypernovae, the astronomers are able to fix with good accuracy the moment of the stellar explosion. It turns out to be within an interval of plus/minus two days of the gamma-ray burst. This unique conclusion provides compelling evidence that the two events are directly connected.
These observations therefore indicate a common physical process behind the hypernova explosion and the associated emission of strong gamma-ray radiation. The team concludes that it is likely to be due to the nearly instantaneous, non-symmetrical collapse of the inner region of a highly developed star (known as the “collapsar” model).
The March 29 gamma-ray burst will pass into the annals of astrophysics as a rare “type-defining event”, providing conclusive evidence of a direct link between cosmological gamma-ray bursts and explosions of very massive stars.
What are Gamma-Ray Bursts?
One of the currently most active fields of astrophysics is the study of the dramatic events known as “gamma-ray bursts (GRBs)”. They were first detected in the late 1960’s by sensitive instruments on-board orbiting military satellites, launched for the surveillance and detection of nuclear tests. Originating, not on the Earth, but far out in space, these short flashes of energetic gamma-rays last from less than a second to several minutes.
Despite major observational efforts, it is only within the last six years that it has become possible to pinpoint with some accuracy the sites of some of these events. With the invaluable help of comparatively accurate positional observations of the associated X-ray emission by various X-ray satellite observatories since early 1997, astronomers have until now identified about fifty short-lived sources of optical light associated with GRBs (the “optical afterglows”).
Most GRBs have been found to be situated at extremely large (“cosmological”) distances. This implies that the energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00.
During the past years circumstantial evidence has mounted that GRBs signal the collapse of massive stars. This was originally based on the probable association of one unusual gamma-ray burst with a supernova (“SN 1998bw”, also discovered with ESO telescopes, cf. ESO PR 15/98). More clues have surfaced since, including the association of GRBs with regions of massive star-formation in distant galaxies, tantalizing evidence of supernova-like light-curve “bumps” in the optical afterglows of some earlier bursts, and spectral signatures from freshly synthesized elements, observed by X-ray observatories.
VLT observations of GRB 030329
On March 29, 2003 (at exactly 11:37:14.67 hrs UT) NASA’s High Energy Transient Explorer (HETE-II) detected a very bright gamma-ray burst. Following identification of the “optical afterglow” by a 40-inch telescope at the Siding Spring Observatory (Australia), the redshift of the burst was determined as 0.1685 by means of a high-dispersion spectrum obtained with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile).
The corresponding distance is about 2,650 million light-years. This is the nearest normal GRB ever detected, therefore providing the long-awaited opportunity to test the many hypotheses and models which have been proposed since the discovery of the first GRBs in the late 1960’s.
With this specific aim, the ESO-lead team of astronomers now turned to two other powerful instruments at the ESO Very Large Telescope (VLT), the multi-mode FORS1 and FORS2 camera/spectrographs. Over a period of one month, until May 1, 2003, spectra of the fading object were obtained at regular rate, securing a unique set of observational data that documents the physical changes in the remote object in unsurpassed detail.
The hypernova connection
Based on a careful study of these spectra, the astronomers are now presenting their interpretation of the GRB 030329 event in a research paper appearing in the international journal “Nature” on Thursday, June 19. Under the prosaic title “A very energetic supernova associated with the gamma-ray burst of 29 March 2003”, no less than 27 authors from 17 research institutes, headed by Danish astronomer Jens Hjorth conclude that there is now irrefutable evidence of a direct connection between the GRB and the “hypernova” explosion of a very massive, highly evolved star.
This is based on the gradual “emergence” with time of a supernova-type spectrum, revealing the extremely violent explosion of a star. With velocities well in excess of 30,000 km/sec (i.e., over 10% of the velocity of light), the ejected material is moving at record speed, testifying to the enormous power of the explosion.
Hypernovae are rare events and they are probably caused by explosion of stars of the so-called “Wolf-Rayet” type . These WR-stars were originally formed with a mass above 25 solar masses and consisted mostly of hydrogen. Now in their WR-phase, having stripped themselves of their outer layers, they consist almost purely of helium, oxygen and heavier elements produced by intense nuclear burning during the preceding phase of their short life.
“We have been waiting for this one for a long, long time”, says Jens Hjorth, “this GRB really gave us the missing information. From these very detailed spectra, we can now confirm that this burst and probably other long gamma-ray bursts are created through the core collapse of massive stars. Most of the other leading theories are now unlikely.”
A “type-defining event”
His colleague, ESO-astronomer Palle M?ller, is equally content: “What really got us at first was the fact that we clearly detected the supernova signatures already in the first FORS-spectrum taken only four days after the GRB was first observed – we did not expect that at all. As we were getting more and more data, we realised that the spectral evolution was almost completely identical to that of the hypernova seen in 1998. The similarity of the two then allowed us to establish a very precise timing of the present supernova event”.
The astronomers determined that the hypernova explosion (designated SN 2003dh ) documented in the VLT spectra and the GRB-event observed by HETE-II must have occurred at very nearly the same time. Subject to further refinement, there is at most a difference of 2 days, and there is therefore no doubt whatsoever, that the two are causally connected.
“Supernova 1998bw whetted our appetite, but it took 5 more years before we could confidently say, we found the smoking gun that nailed the association between GRBs and SNe” adds Chryssa Kouveliotou of NASA. “GRB 030329 may well turn out to be some kind of ‘missing link’ for GRBs.”
In conclusion, GRB 030329 was a rare “type-defining” event that will be recorded as a watershed in high-energy astrophysics.
What really happened on March 29 (or 2,650 million years ago)?
Here is the complete story about GRB 030329, as the astronomers now read it.
Thousands of years prior to this explosion, a very massive star, running out of hydrogen fuel, let loose much of its outer envelope, transforming itself into a bluish Wolf-Rayet star . The remains of the star contained about 10 solar masses worth of helium, oxygen and heavier elements.
In the years before the explosion, the Wolf-Rayet star rapidly depleted its remaining fuel. At some moment, this suddenly triggered the hypernova/gamma-ray burst event. The core collapsed, without the outer part of the star knowing. A black hole formed inside, surrounded by a disk of accreting matter. Within a few seconds, a jet of matter was launched away from that black hole.
The jet passed through the outer shell of the star and, in conjunction with vigorous winds of newly formed radioactive nickel-56 blowing off the disk inside, shattered the star. This shattering, the hypernova, shines brightly because of the presence of nickel. Meanwhile, the jet plowed into material in the vicinity of the star, and created the gamma-ray burst which was recorded some 2,650 million years later by the astronomers on Earth. The detailed mechanism for the production of gamma rays is still a matter of debate but it is either linked to interactions between the jet and matter previously ejected from the star, or to internal collisions inside the jet itself.
This scenario represents the “collapsar” model, introduced by American astronomer Stan Woosley (University of California, Santa Cruz) in 1993 and a member of the current team, and best explains the observations of GRB 030329.
“This does not mean that the gamma-ray burst mystery is now solved”, says Woosley. “We are confident now that long bursts involve a core collapse and a hypernova, likely creating a black hole. We have convinced most skeptics. We cannot reach any conclusion yet, however, on what causes the short gamma-ray bursts, those under two seconds long.”
Original Source: ESO News Release | 0.89942 | 4.001744 |
Image: Astronomy Picture of the Day: The Center of Centaurus A
Displaying image 356 of 363 images in Astronomy.
Multiverses: 700 The Center of Centaurus A
Credit: E.J. Schreier (AUI) et al., Hubble, NASA; Inset: NOAO
Astronomy Picture of the Day - 2010 November 7
Explanation: A fantastic jumble of young blue star clusters, gigantic glowing gas clouds, and imposing dark dust lanes surrounds the central region of the active galaxy Centaurus A. This mosaic of Hubble Space Telescope images taken in blue, green, and red light has been processed to present a natural color picture of this cosmic maelstrom. Infrared images from the Hubble have also shown that hidden at the center of this activity are what seem to be disks of matter spiraling into a black hole with a billion times the mass of the Sun! Centaurus A itself is apparently the result of a collision of two galaxies and the left over debris is steadily being consumed by the black hole. Astronomers believe that such black hole central engines generate the radio, X-ray, and gamma-ray energy radiated by Centaurus A and other active galaxies. But for an active galaxy Centaurus A is close, a mere 10 million light-years away, and is a relatively convenient laboratory for exploring these powerful sources of energy.
9 years ago. | 0.862141 | 3.104622 |
This image, the M31 Deep Field, may not look like much. It doesn’t have the bold colors and dynamic composition of many Hubble images. Yet it’s one of my favorite images because of what we can see if we look a little harder. In fact it shows nothing less than the entire sweep of the cosmos from our “back yard” to the incomprehensibly vast depths of space.
The image is a composite of numerous long exposures with Hubble, staring at a patch of sky near the magnificent Andromeda Galaxy, a.k.a. Messier 31 (M31 for short). Sound familiar? Hubble has produced many “Deep Fields” starting in 1995, taking long exposures of small patches of the sky. Most of these fields were intentionally pointed away from anything relatively bright or nearby in order to explore the farthest reaches of space. In this case, Hubble was pointed toward one of our nearest neighboring galaxies, a near twin of our own Milky Way, to study the population of faint stars in its outer regions.
Wide-field ground-based images of M31 like the one above, made with a wide-field telescope at the great Palomar Observatory, mostly show the huge, bright disk of stars, gas, dust, etc., tilted to our line of sight. In addition there are a couple of small satellite galaxies accompanying M31. This is very much like what our Milky Way Galaxy would look like if we could fly far away and look back toward home. What this image doesn’t show well is the large, spherical “halo” of fainter stars that surrounds the galaxy and stretches to very great distances. Studying the stars in this halo was the reason for Hubble’s observations. The small green box shows the tiny size of the much more detailed Hubble image.
Unlike many of Hubble’s color images, this one was made using only two filters rather than the usual three, sampling the V and I bands. This was just what was needed for the science analysis to measure brightnesses and colors of the many stars in the field. A glance at the two images separately shows little difference. It is possible to construct a color composite from just two images, but the range of colors is not as varied as with three component images. When we apply color, composite the images together, and make some adjustments to brightness and contrast, the color pops out nicely.
Let’s zoom in on a few smaller pieces of the image.
1. 2. 3.
The first few details show lots of stars with a range of brightness and colors and a smattering of galaxies of different types. In this case, the brightest stars are in our Galaxy, maybe a few thousand light-years away. The fainter stars scattered through the images are in M31, 2.5 million light-years away. And the galaxies, which are all roughly the same physical size as the Andromeda Galaxy, appear much smaller because they are vastly farther away: tens of millions, hundreds of millions, or even billions of light-years away, a mind-boggling range of distances in just one tiny piece of sky!
Other details from the image show galaxies of very different types, in this case a nicely formed spiral seen face-on, much like our Galaxy and Andromeda, but also very different ones, like the small, bluish dwarf that shows very little organized form and no obvious gas, dust or anything else other than stars.
Most amazing to me though is the final detail. It shows a star cluster just at the bottom edge of the Hubble image. This is a particular kind of object called a globular cluster, a large grouping of maybe hundreds of thousands of stars that formed together a long time ago and are still bound together by their mutual gravity. It looks for all the world like images of globular clusters in our own Galaxy that we’ve seen for many years. But this cluster is 2.5 million light-years away in the Andromeda Galaxy, about 100 times the distance to most similar objects in our Galaxy. Yet we clearly see individual stars thanks to the dramatic improvement in resolution provided by the Hubble Space Telescope.
The deep image focusing on the halo of M31 is visually subtle but conceptually mind-boggling, showing the vast sweep of the universe in a single view.
For more information about this and other Hubble images, visit HubbleSite. | 0.816847 | 3.810881 |
How fast does the Earth's core rotate currently, and what would happen if its speed of rotation were to increase dramatically?
Earth's core currently rotates at about the same rate as the rest of the planet, 360 degrees every 24 hours. There is a hypothesis that it may rotate very slightly faster, an extra 0.3 to 0.5 degree every year, but this is unproven, either way.
If Alien Space Bats somehow made it spin a lot faster, things would get exciting. It would change shape from a slightly flattened sphere into a somewhat more flattened sphere. It would also start to transfer angular momentum to the rest of Earth, because of friction between the liquid outer core and the inner layers of the mantle, and the same friction would start to convert the energy of the faster rotation into heat.
All of this means earthquakes and volcanoes. The change of shape and the transfer of angular momentum would be noticeable first, up here on the surface, first in earthquakes, and them probably in volcanoes triggered by the 'quakes.
How powerful are the 'quakes? That depends on how much the core has been sped up. Doing that hard enough will tear the planet apart, doing it rather less would just melt the whole thing, and doing it more gently would just wreck everything we've built and cause an apocalypse. It's fortunate that there's no obvious way of doing this, and that it's going to be far easier for the ASBs to just nuke us, or hit us with extinction-level asteroids.
Increasing the rotation of the core of the earth will increase the magnetic field around the earth which might have further ramifications. This increase will occur because of the existence of electric charge in the liquid core which will rotate at higher speed thus producing high electric current and magnetic field.
If the Earth's core were to speed up then the liquid outer core would heat up. As you have mentioned only the core is spinning faster not the whole Earth. This could result in massive friction from the outer core and the mantle. This means more heat and more volcanoes. In the short term it would ruin everything, however in the long term faster Earth's core means protection from the sun. Eventually however the core would slow down as all the rotational energy is converted into thermal energy/heat. However during the time the Earth's core does rotate we would get stronger. This could be good and bad. Magnetic field protects from solar radiation, but around the Earth there is a layer of radiation around the Earth called the Van Allen's belt. So if the Earth's magnetic field got any stronger going to space would still be a bad idea even in the Earth's magnetic field as the Van Allen's belt would accumulate more charged particles which could affect electronics in space.
All of this is the positive side of things and considering that the core did not speed up very fast very quickly. If Earth's core sped up very fast it would quickly melt the mantle and the crust. It would probably make Earth the hottest planet now. Not because of the greenhouse effect(Molten surface means more carbon dioxide means more greenhouse effect) but because the whole surface is molten and hot, from the heat of the Earth's core.
You might look into the Dinosaurs on the moon hypothesis. It roughly goes like this:
- In the beginning or our solar system, the sun ignites, the remaining accretion disk gets hot.
- Big hunks of accretion are drawn into fast spinning molten metal spheres.
- The sphere cools to make a crust. Life evolves. The world has no oceans and is a huge hunk of swamp with low gravity on the surface from the rapid spin. Go dinosaurs!
- Internal friction causes the Earth crust to spin a bit faster than the interior. An instability occurs and slowly magnifies. A large blister forms lifting some portions of the crust high on pockets on magma.
- The system is unstable. A cataclysmic break in the crust causes the ripping of large sections of the crust as the high rotational blisters rip off. Serious mass departs from the earth, taking huge swaths of crust. The remaining crust spins slower. Water accumulates into the low sections. The earth develops a tilt. Some life survives, but its not the big swampy paradise any more. The big blister looks suspiciously like a meteor strike.
- The ejecta exits the atmosphere but is captured by the planetary pull. We call it the moon. With enough exploration, we will eventually find dinosaur bones on the moon.
The theory, while ridiculous, has a surprising number of correlations with reality: fluid simulations; timing; composition; rotational velocity; etc.
So changing the rotation speed of the core might make things unhappy on the surface. It should take a while. | 0.825426 | 3.175341 |
Title: The Milky Way has no thick disk
Author: Jo Bovy, Hans Walter-Rix, David Hogg
Lead Author’s Institution: Institute for Advanced Study
It is written in The Standard Lore of Astronomy – a leather-bound book professors keep under their desks – that stars in the disks of spiral galaxies have a bimodal distribution of scale heights. Let’s back up a bit and explain exactly what I mean by that. To a decent level of approximation, most of the stars in disk galaxies are contained within a 2D sheet of stars. The stars orbit within a plane defined by the angular momentum vector of the galaxy. However, that’s not the whole story. Disk stars also have a component of their orbits in the vertical direction. Taken as a whole, the population of disk stars exhibit a distribution of vertical heights, characterized by a scale height, h. For a population of disk stars with a single scale height, the probability of finding a star at a given height z above the disk is proportional to exp(-z/h). Thus, the statement I made earlier, that stars in disk galaxies are characterized by a bimodal distribution of scale heights, implies that disk galaxies are really composed of two different kinds of disks: a thick disk and a thin disk. Disk stars at large heights (and thus likely members of the thick disk) are generally observed to be old and metal-poor. Stars in the thin disk, like the sun, are generally younger and have a metallicity comparable to the sun. Today we will be discussing a paper that comes to the conclusion that the notion of a thick disk and a thin disk is actually a poor approximation to the true distribution of disk stars. The authors of this paper propose that stars in the disk have a smooth and featureless distribution of scale heights.
This conclusion is based on data from the G-dwarf sample in the SEGUE survey. SEGUE – the Sloan Extension for Galactic Understanding and Exploration – uses the Sloan telescope (of SDSS fame) to obtain spectra of stars in the disk and halo of the Milky Way. From these spectra, one can infer the spectral type, iron metallicity, and abundances of other common elements. In particular, it is very instructive to look at the iron metallicity relative to the sun, [Fe/H], and the α-element abundance relative to iron [α/Fe]. Alpha elements like C, N, O, and Ca, are produced in triple-alpha reactions in the cores of red giant stars. The iron abundance gives an observer information about the age of the star, since older stars were born in an epoch when a large fraction of the heavy elements in the universe had yet to be synthesized. The α element abundance hints at the star formation history of a stellar population, since α elements are produced in large quantities relative to iron by core-collapse Type-II supernovae, which only occur in young stellar populations, but are produced at much lower levels relative to iron in Type-Ia supernovae, which do not occur until a stellar population is old enough for a significant population of white dwarfs to emerge.
In a previous work, Jo Bovy and collaborators binned stars in ([Fe/H],[α/H]) space and found that stars within each bin are well characterized by a single scale height. This observation is interesting, since presumably all of the stars that formed with a particular abundance pattern did so at roughly the same period in galactic history. This is also a very useful observation, since it allows one to infer how much stellar mass is in stars with a particular scale height. In principle one knows from stellar population synthesis models how much total stellar mass is associated with a number count of G type dwarfs and one can correct for the selection bias and limited volume of the SEGUE survey, which probably missed many G dwarfs in the survey volume. Of course, the devil is in the details, and modeling uncertainties imply that any error in the completeness correction and stellar population synthesis modeling could significantly change the authors’ results.
Ignoring that caveat, the final result is striking. The authors calculate the surface density of stars in the disk of the milky way at the solar circle Σ(R0), as a function of scale height, h. This result is plotted as a black solid line above. The individual data points are the average mass surface densities and scale heights for each subsample in ([Fe/H],[α,Fe]) space and are colored by the α-abundance relative to iron. Stars that are α-enhanced tend to have large scale heights, while stars with α-abundance consistent with solar ([α,Fe] ~ 0) tend to have relatively small scale heights. If one looks only at α-abundance, there do appear to be two populations. However, closer inspection, and weighting stellar counts to infer the stellar mass distribution, reveals that stars have a smooth distribution of scale heights. Most of the mass is in stars small scale heights, traditionally associated with the thin disk. A smaller portion of the mass is in stars with large scale heights, traditionally associated with the thick disk. However, there is also a population of stars with intermediate scale heights, with no clear break in the mass distribution at any scale. Thus, assuming the modeling uncertainties have been correctly accounted for, there is no thick or thin disk, only a single, more complicated disk composed of stars with a range of scale heights. | 0.843288 | 3.968492 |
Scientists have detected a cosmic explosion in a far-off galaxy cluster that has left a hole the size of 15 Milky Ways in its wake.
In findings published in The Astrophysical Journal, researchers have reported on an enormous release of energy from a supermassive black hole some 390 million light years away from Earth. While black holes are better known for pulling in huge amounts of matter, they’re also known to expel it. And, with the Ophiuchus galaxy cluster it would appear that this is exactly what has happened.
The Ophiucus cluster has been a subject of curiosity for researchers for many years, who have noticed a curious edge on the aggregation of thousands of individual galaxies for some time now. However, Simona Giacintucci of the Naval Research Laboratory in Washington, DC described a new observation of this anomaly, which is now being seen as a massive explosion, leaving behind a hole that could fit 15 of our own Milky Way galaxies inside it.
“In some ways, this blast is similar to how the eruption of Mount St Helens (volcano) in 1980 ripped off the top of the mountain,” she said.
“A key difference is that you could fit 15 Milky Way galaxies in a row into the crater this eruption punched into the cluster’s hot gas,”
Co-author, Maxim Markevitch, of Nasa’s Goddard Space Flight Center in Greenbelt, Maryland commented on further observations that there were bubbles of radio emissions emerging on the curved edge of the hole. He said that these radio emissions are evidence of something huge.
“This is the clincher that tells us an eruption of unprecedented size occurred here,” he said.
The first observations were made through Nasa’s Chandra X-ray Observatory in 2016, while later combining data with ESA’s XMM-Newton space observatory and radio data from the Murchison Widefield Array (MWA) in Australia and the Giant Metrewave Radio Telescope (GMRT) in India. The combination of the projects have provided compelling evidence of a major event that could provide insights into the origins of the universe. Scientists believe the explosion may have occurred due to a spike of gas supplied to the black hole, perhaps after an entire galaxy was swallowed from the centre of the cluster.
This event is thought to have occurred several hundred million years ago and the black hole shows no signs of dramatic activity at present. | 0.848558 | 3.756761 |
The Field of Streams. Image credit: Vasily Belokurov/SDSS-II. Click to enlarge
The Milky Way is continuing to consume entire galaxies, and the evidence is right there in the night sky. After analyzing data from the Sloan Digital Sky Survey, astronomers have found many streams of stars – all that remains from these gobbled up galaxies. As a satellite galaxy merges with the Milky Way, it’s slowly torn apart as it sinks into the galactic halo. Streams of stars are unraveled like a ball of yarn, and these continue to orbit the Milky Way, distinct from the orbital movements of the rest of the stars in our galaxy.
A new map of stars in the Milky Way Galaxy, constructed with data from the Sloan Digital Sky Survey (SDSS-II), reveals a night sky criss-crossed with streams of stars, left behind by satellite galaxies and star clusters spiraling to their deaths.
Analyzing five years of data spanning nearly one-quarter of the sky, Cambridge University (UK) researchers Vasily Belokurov and Daniel Zucker created a dramatic new image of the outer Milky Way, using stellar colors eliminating the redder, nearby stars that would otherwise swamp the view of background structures. They found so many trails of stars in their high contrast image that they named the area the “Field of Streams.”
Satellite galaxies orbiting the Milky Way are literally ripped apart by the tidal forces of our galaxy. As these satellites sink in gravitational quicksand, their stars are torn from them in giant streams that trace their orbital paths — just like meteor streams lie along the paths of defunct comets in the Solar system.
Dominating the Field of Streams image is the enormous, arching stream of the Sagittarius dwarf galaxy. The Sagittarius dwarf was discovered more than a decade ago and other researchers have previously mapped its long tidal stream in other regions of the sky.
But the new SDSS-II data had a remarkable surprise in store.
“The stream appears forked,” said Belokurov. “We are seeing different wraps superimposed on the sky, as the stream goes around the galaxy two or three times.”
Because of the multiple wraps, the observations provide strong new constraints on the dark matter halo of the Milky Way, according to Mike Fellhauer of Cambridge University. “The leading theories of dark matter predict that the Galaxy’s halo should be flattened, like a rugby football. But our simulations only match the forked Sagittarius stream if the inner halo is round, like a soccer ball.”
In addition to the Sagittarius arches, the Field shows faint trails of stars torn from globular clusters, and other rings, trails, and lumps that appear to be the remains of disrupted dwarf galaxies. “There are more streams here than in a river delta,” commented Zucker.
Prominent among these is the Monoceros stream, discovered previously by SDSS-II scientists Heidi Jo Newberg of Rensselaer Polytechnic Institute and Brian Yanny of the Fermi National Accelerator Laboratory. The multiple rings of stars are all that remain from a dwarf satellite that was absorbed by the Milky Way long ago.
Crossing the Field is an enigmatic, new stream of stars extending over 70 degrees on the sky, whose original source remains unknown.
“Some of these ‘murdered’ galaxies have been named,” explained SDSS-II team member Wyn Evans of Cambridge, “but this galactic corpse hasn’t been identified yet. We’re looking for it right now.”
These new discoveries add weight to a picture in which galaxies like the Milky Way are built up from the merging and accretion of smaller galaxies.
“We’ve known about merging for some time,” said Yanny, “but the Field of Streams gives us a striking demonstration of multiple merger events going on the Milky Way galaxy right now. This is happening all over the Universe, as big galaxies grow by tearing up smaller ones into streams.”
These streams also provide new tests of the nature of dark matter itself, according to theorist James Bullock of University of California at Irvine; Bullock was not part of the SDSS team.
“The fact that we can see a ‘Field of Streams’ like this suggests that dark matter particles are very ‘cold’, or slow moving. If the dark matter was made up of ‘warm,’ fast moving particles, we wouldn’t expect these thin streams to hang around long enough for us to find them.”
Original Source: RAS News Release | 0.845378 | 3.947029 |
They say variety is the spice of life, and now new discoveries from Johns Hopkins researchers suggest that a certain elemental ‘variety’—sulfur—is indeed a ‘spice’ that can perhaps point to signs of life.
These findings from the researchers’ lab simulations reveal that sulfur can significantly impact observations of far-flung planets beyond the solar system; the results have implications for the use of sulfur as a sign for extraterrestrial life, as well as affect how researchers should interpret data about planetary atmospheres.
A report of the findings was published today in Nature Astronomy.
“We found that just a small presence of sulfur in the atmosphere, less than 2%, can have major impacts on what, and how many, haze particles are formed,” says Chao He, an assistant research scientist in the Department of Earth and Planetary Sciences at The Johns Hopkins University and the study’s first author.
“This entirely changes what scientists should look for and expect when they examine atmospheres on planets beyond our solar system.”
While scientists already know that sulfur gases influence the photochemistry of many planets within the solar system such as Earth, Venus and Jupiter, not much is known about sulfur’s role in the atmospheres of planets beyond the solar system, or exoplanets.
Due to its role as an essential element for life on Earth—emitted from plants and bacteria, and found in several amino acids and enzymes—scientists propose to use sulfur products to search for life beyond Earth. Understanding whether sulfur exists and how it affects these atmospheres can help scientists determine whether sulfur gases could be used as a source for life to originate, says He.
Researchers have performed few studies simulating planetary atmospheres with sulfur in the lab due to its high reactivity and difficulty to clean up once an experiment is done, says He. In fact, sulfur is so reactive that it would have even reacted with the experimental setup itself, so the research team had to upgrade their equipment to properly tolerate sulfur. To He’s knowledge, only three other studies that simulated sulfur chemistry in the lab exist, and those were to understand its role in Earth’s atmosphere; this is the first lab-run simulation to study sulfur in exoplanet atmospheres.
Chao and colleagues performed two sets of experiments using carbon dioxide, carbon monoxide, nitrogen, hydrogen, water and helium as a guide for their initial gas mixtures. One experiment included 1.6% sulfur in the mix and the other did not. The research team performed the simulation experiments in a specially designed Planetary HAZE (PHAZER) chamber in the lab of Sarah Hörst, assistant professor of Earth and Planetary Sciences and second author on the paper.
Once in the chamber, the team exposed the gas mixtures to one of two energy sources:
plasma from an alternating current glow discharge or light from an ultraviolet lamp. Plasma, an energy source stronger than UV light, can simulate electrical activities like lightning and/or energetic particles, and UV light is the main driver of chemical reactions in planetary atmospheres such as those on Earth, Saturn and Pluto.
After analyzing for solid particles and gas products formed, He and colleagues found that the mixture with sulfur had three times more haze particles, or solid particles suspended in gas.
Chao’s team found that most of these particles were organic sulfur products rather than sulfuric acid or octasulfur, which researchers previously believed would make up the majority of sulfur particles on exoplanets.
“This new information means that if you’re trying to observe an exoplanet’s atmosphere and analyze its spectra, when you previously expected to see other products, you should now expect to see these organic sulfur products instead. Or, at least, you should know that it wouldn’t be unusual for them to be there. This would change researchers’ explanation and interpretation of spectra they see,” says He.
Similarly, the findings should direct researchers to expect more haze particles if they are observing exoplanet atmospheres with sulfur, as just a small bit of sulfur increases haze production rate by three. Again, this would change how researchers interpret their findings and could be critical for future observation of exoplanets.
The last major implication of his findings, He says, is they push for heightened awareness that many sulfur products can be produced in the lab, in the absence of life, so scientists should be caution and rule out photochemically-produced sulfur before suggesting sulfur’s presence as a sign for life.
Other authors on this paper include Patricia McGuiggan and Sarah E. Moran of The Johns Hopkins University; Xinting Yu of University of California Santa Cruz, Nikole K. Lewis of Cornell University; Julianne I. Moses of The Space Science Institute; Mark S. Marley of the NASA Ames Research Center; Eliza M.-R. Kempton of the University of Maryland, College Park; Caroline V. Morley of the University of Texas at Austin, and; Véronique Vuitton of the Institut de Planétologie et d’Astrophysique de Grenoble. | 0.874713 | 3.87551 |
Dynamic Measurement of the ALMA Project Antenna Settings
SETIS - ALMA Project - France
The Atacama Large Millimeter Array (ALMA) is a project which consists of building an interferometric network of 66 mobile radiotelescopes located in Chile on a plateau of the Atacama desert at an altitude of 5100 m. Detailed and sustained measurements have revealed that the sky above the Atacama desert presents unique conditions of transparency and stability. ALMA will enable studying stars, galaxies and other 2 3 objects in the universe by collecting the „light“ they emit with millimetric and sub-millimetric waves. ALMA will be a unique instrument in the sense where it will enable producing detailed images, both in continuum and ray spectrum, of galaxies in formation, stars, planets, and interstellar clouds containing the chemical composites necessary for life to develop. Its approximate budget of one billion Euros is distributed between Europe (by means of the ESO), the United States (by means of NRAO) and Japan (by means of the NAOJ). These are some of ALMA‘s main research topics: -
The study of the young universe by means of observing distant galaxies - The study of star formation by means of observing molecular clouds (such as Orion for example)
- The study of planet formation
- The quest for exoplanets by astrometry
The study of the solar system based on the study of dust and the atmospheres of different planets such as Mars and Venus (the latter topic will enable having a better idea of their atmospheric dynamic or detecting the existence of water for example) Each antenna is a parabolic dish 12 m in diameter, 22 m in height, which weighs 115 tonnes and can resist a temperature varying between -20°C and +20°C.
Different Supporting Projects
The company SETIS has been entrusted with different supporting projects within the scope of the European part of the project that includes the manufacture of 25 antennae by the AEM consortium (Thalès, EIE and MT-Mechatronics). During the initial manufacture phase of antenna prototypes, the challenge was both the carbon assembly of the cabin in addition to the antenna itself, on the test site in New Mexico. The assembly project by measuring the different aspects of the antenna carbon structures consisted of measuring carbon domes for mechanical joining to the panel that serves as an antenna. No less than 2560 mechanical interfaces have to be set! SETIS‘ mission was to look for the most adapted measurement solutions and their implementation (methodology, recommendation, support...) to optimise the enormous amount of work to perform.
The manufacture of the back-up structure in Italy with drawing up of monitoring and assembly procedures on site was the second industrial phase of the project. SETIS therefore appointed a person on site in Chile to be responsible for implementing the first few antennas and training the operators.
The full range of Leica Geosystems industrial measurement instruments was implemented by SETIS during all the manufacture phases of the first antenna:
- The civil engineer receiving the antenna: size monitoring to verify its specifications compliance with a Leica Absolute Tracker AT901 at +/- 25µ, exterior, under tent, in a volume of 4500 x 4500 x 300 mm. The metallic structure during manufacture of an antenna (in Spain) and during its integration on site: size monitoring to verify its specifications compliance and deformation monitoring in Chile with a Leica Absolute Tracker AT901 at +/- 100 µ, in a provisional „container“ in a volume of 4500 x 4000 x 8000 mm
- The carbon fibre cabin during its integration in Chile: monitoring of deformation and alignment verification with a Leica Absolute Tracker AT901 at +/- 100 µ, in a provisional „container“, in a volume of 4500 x 4000 x 9000 mm
- The reflector structure (Back Up Structure) during its assembly in Chile: monitoring of deformation and alignment verification with a Leica Absolute Tracker AT901 at +/- 100 µ, in an air-conditioned building and in a volume of 12000 x 12000 x 4500 mm
- Setting the panel supports of the reflector: more than 600 “adjusters” (feet supporting the panels) were set to +/- 0.10 mm with Leica LTD640, in an air-conditioned building and a volume of 12000 x 12000 x 2000 mm.
After automation by a range of software measurements, these measurements will be taken almost autonomously by the Chilean teams of mechanics and assembly workers with no knowledge in metrology. A total of 120 reflector panels were set with Leica LTD640 at +/- 0.05 mm. The final surface area of the parabolic dish presented RMS=30 µm by monitoring 600 points.
The final surface area of the reflector was monitored at +/- 25 µm with a Leica Absolute Tracker AT901 and performed outside, with no protection and at night to avoid sun rays, in a volume of 12000 x 12000 x 2000 mm.
SETIS also verified the antenna’s kinematics, that is, its horizontal rotation movement in addition to its relative geometry. A Leica Nivel230 enabled monitoring the verticality (integrating the oscillation of the rotation axis) with a tolerance of 15Arcsec. The antenna’s geometric characteristics, that is, the orthogonality of the azimut axis (principal axis) compared to the elevation axis (horizontal axis) were measured dynamically with a laser tracker at 1.8 ArcSec.
Finally, SETIS performed deformation tests of carbon fibre structures with measurement uncertainties of approximately 10 µm over a distance of 3 m for 24 hours and then for 12 hours with measurement results at 3 µm over a distance of 4 m. Between the prototype and industrialisation, the Grenoble-based company has contributed to the evolution of measurement methods to enable a mass production of antennae.
Gaël Archambeau, ALMA project manager for SETIS, concluded “The Leica Geosystems tools have enabled dynamic measurement of the settings whilst at the same time offering the precision demanded by the client. Laser trackers are reliable under all atmospheric conditions and SETIS guarantees obtaining exact measurements, even when these approach micron precision. We have been able to rise up to this challenge thanks to a close and longlasting collaboration with the Hexagon Metrology team. | 0.809673 | 3.13877 |
The first-ever interstellar probe may cruise through space like a boat through the ocean, propelled by super-focused light beamed onto a sail the size of Texas.
Solar sailing is perhaps humanity's best bet for reaching star systems beyond our own in the foreseeable future, some scientists say, though they caution that the first robotic interstellar flight is not exactly around the corner.
"I think it's 300 to 500 years [away], personally," said Les Johnson, deputy manager of the Advanced Concepts Office at NASA's Marshall Space Flight Center in Huntsville, Ala. "I think before we ever really undertake sending something to another star, we will probably have to be masters of our own solar system."
The vastness of space
Humanity will need to employ new propulsion technology if it hopes to launch spacecraft to other stars, because the distances involved are just too huge for traditional chemical rockets to handle. [Gallery: Visions of Interstellar Flight]
For example, the closest star system to our own is the three-star Alpha Centauri, which lies 4.3 light-years away, or more than 25 trillion miles (40 trillion kilometers). It would take a traditionally powered spacecraft about 40,000 years to reach Alpha Centauri if it blasted off today, scientists say.
Engineers are currently researching a number of different alternative-propulsion technologies, including space-bending "warp drives" and engines that harness the power of matter-antimatter reactions. But Johnson thinks the most attractive options at the moment are nuclear fusion drives and gigantic solar sails.
A fusion-powered probe is a long way off, since researchers are still trying to figure out how to build fusion reactors here on Earth that produce more energy than they take in.
"Not only do we have to solve that problem, but we've got to get a lot more out than we put in, and we've got to miniaturize it all dramatically so you can even consider launching it on a spacecraft," Johnson told SPACE.com.
Solar sailing has its own mix of promise and problems, which researchers are still trying to work through.
A light breeze
Solar sails take advantage of the curious fact that light particles, called photons, have momentum even though they possess no rest mass.
When photons hit the sail's reflective surface, they impart their momentum to the sail and the spacecraft, providing a slight push. The effect builds up over time, potentially accelerating a sail-equipped probe to tremendous speeds without the need for propellant. [Photos: Solar Sail Evolution for Space Travel]
The technology has already been tested in space, with Japan's Ikaros probe deploying a 46-foot-wide (14 meters) sail in June 2010 and NASA launching an even smaller craft called NanoSail-D five months later.
These demonstrators may be first steps toward an interstellar mission, but they're halting and tiny ones. A solar sail would have to be far bigger to capture enough photons to reach another star system within a reasonable time frame — a few centuries, say.
"The physics tells us it's going to be the size of Texas," Johnson said.
The sail material would also need to be much thinner than a human hair, posing serious manufacturing, handling and deployment challenges, he added.
Beaming energy from afar
A spacecraft on an interstellar journey would ideally deploy its enormous sail relatively close to the sun — perhaps near the orbit of Mercury — to get the biggest photon push possible at the outset, Johnson said.
That push will drop off as the probe gets farther and farther from the sun, of course. So humanity will have to pick up the slack if the vehicle is to make good time, shining a space-based laser on the sail as it recedes into the dark depths.
But that's easier said than done, to put it mildly.
"You'd have to point [the laser] more accurately than we can point anything today to keep it focused on the sail," Johnson said. "And you'd have to put a lot of energy into it, so that the beam doesn't spread out and lose all that energy. The estimates I've seen are that you'd have lasers that have a power output basically comparable to the whole of humanity today."
The energy beam could be pretty much any type of electromagnetic radiation, including microwaves, said Richard Obousy, president of Icarus Interstellar, a nonprofit group devoted to pursuing interstellar spaceflight.
"You can actually reach reasonable fractions of the speed of light, a few percent of the speed of light," Obousy told SPACE.com.
The challenges posed by insterstellar flight may seem insurmountable to us now. But Johnson is hopeful that humanity will overcome them someday, after we've expanded our footprint to cover a broad swath of the solar system.
Once we've become an interplanetary species that has mastered the ability to get raw materials and energy from space, then it'll be natural to turn our gaze to other stars, Johnson said.
"We're going to run into the problem of the limitations of the solar system eventually," he said. "So the next step will be, there's a whole galaxy out there. It's too big a step for us to take now, but I would like to think that several generations in the future, that'll just be the next logical step."
Obousy agrees that tapping the vast resources of the solar system will be a key step toward mastering interstellar flight. But he's more optimistic than Johnson about the timeline, saying that humanity has a good shot at launching its first interstellar mission by the end of the century.
"I think a lot of people tend to overestimate what we can accomplish in the short term, in the next five to 10 years," Obousy said. "But they also vastly underestimate what we can accomplish in the long term, decades or a century from now." | 0.8582 | 3.734703 |
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