Most luminous galaxies discovered

Astronomers have observed the most luminous galaxies ever seen in the universe -- objects so bright that descriptors such as “ultra” and “hyper-luminous” don't even come close. According to lead author Kevin Harrington from University of Massachusetts Amherst, they are calling them “outrageously luminous” because there is no scientific term to apply.

The team used the 50-meter diameter Large Millimeter Telescope (LMT) - the most sensitive instrument in the world for studying star formation located on the summit of Sierra Negra, a 15,000-foot extinct volcano in the central state of Puebla, a companion peak to Mexico's highest mountain. They estimate that the newly observed galaxies they identified are about 10 billion years old and were formed only about four billion years after the Big Bang. “Discovering them will help astronomers understand more about the early universe.Their extreme brightness arises from a phenomenon called gravitational lensing that magnifies light passing near massive objects, as predicted by Einstein's general relativity. As a result, from Earth they look about 10 times brighter than they really are 

SOURCE :- The Hans India 

Astrophysicists catch two supernovae at the moment of explosion

An international team of astrophysicists led by Peter Garnavich, professor of astrophysics at the University of Notre Dame, has caught two supernovae in the act of exploding.

Using the Kepler Space Telescope, the team spent three years observing 50 trillion stars for the chance to watch as supersonic shockwaves reached their surfaces after explosions deep in the core. For the first time, a "shock breakout" in an exploding supergiant star was discovered at visible wavelengths.

Stars 10 to 20 times the mass of our sun often puff up to supergiants before ending their lives as supernovae. These stars are so large that Earth's orbit would easily fit inside such a star. When these massive stars run out of fuel in their center, their core collapses down to a neutron star and a supersonic shockwave is sent out to blow up the entire star.

When the shockwave reaches the surface of the star, a bright flash of light, called a "shock breakout," is predicted.

"The flash from a breakout should last about an hour, so you have to be very lucky or continuously stare at millions of stars just to catch one flash," said Garnavich.

In 2011, two of these massive red supergiants exploded while in Kepler's view. The first, KSN 2011a, is nearly 300 times the size of our sun and a mere 700 million light years from Earth. The second, KSN 2011d, is roughly 500 times the size of our sun and some 1.2 billion light years away.

Supernovae like these -- known as Type II -- begin when the internal furnace of a star runs out of nuclear fuel causing its core to collapse as gravity takes over.

Understanding the physics of these explosions allows scientists to better understand how the seeds of chemical complexity and life itself have been scattered in space and time in the Milky Way galaxy.

The Kepler Space Telescope is famous for its discoveries of extra-solar planets, some that may have the right conditions to harbor life. But Kepler can also look at galaxies beyond the Milky Way. A team of astrophysicists from Notre Dame, Maryland, Berkeley and Australia have formed the "Kepler ExtraGalactic Survey," or KEGS, specifically to apply the power of Kepler to study galaxies and supernovae.

Astronomers report most 'outrageously' luminous galaxies ever observed

Astronomers at the University of Massachusetts Amherst report that they have observed the most luminous galaxies ever seen in the Universe, objects so bright that established descriptors such as "ultra-" and "hyper-luminous" used to describe previously brightest known galaxies don't even come close. Lead author and undergraduate Kevin Harrington says, "We've taken to calling them 'outrageously luminous' among ourselves, because there is no scientific term to apply."


Details appear in the current early online edition of Monthly Notices of the Royal Astronomical Society.

Harrington is a senior undergraduate in astronomy professor Min Yun's group, which uses the 50-meter diameter Large Millimeter Telescope (LMT), the largest, most sensitive single-aperture instrument in the world for studying star formation. It is operated jointly by UMass Amherst and Mexico's Instituto Nacional de Astrofísica, Óptica y Electrónica and is located on the summit of Sierra Negra, a 15,000-foot extinct volcano in the central state of Puebla, a companion peak to Mexico's highest mountain.

Yun, Harrington and colleagues also used the latest generation of satellite telescope and a cosmology experiment on the NASA/ESA collaboration Planck satellite that detects the glow of the Big Bang and microwave background for this work. They estimate that the newly observed galaxies they identified are about 10 billion years old and were formed only about 4 billion years after the Big Bang.

Harrington explains that in categorizing luminous sources, astronomers call an infrared galaxy "ultra-luminous" when it has a rating of about 1 trillion solar luminosities, and that rises to about 10 trillion solar luminosities at the "hyper-luminous" level. Beyond that, for the 100 trillion solar luminosities range of the new objects, "we don't even have a name," he says.

Yun adds, "The galaxies we found were not predicted by theory to exist; they're too big and too bright, so no one really looked for them before." Discovering them will help astronomers understand more about the early Universe. "Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with. Their existence teaches us about the process of collecting matter and of galaxy formation. They suggest that this process is more complex than many people thought."

The newly observed galaxies are not as large as they appear, the researchers point out. Follow-up studies suggest that their extreme brightness arises from a phenomenon called gravitational lensing that magnifies light passing near massive objects, as predicted by Einstein's general relativity. As a result, from Earth they look about 10 times brighter than they really are. Even so, they are impressive, Yun says.

Gravitational lensing of a distant galaxy by another galaxy is quite rare, he adds, so finding as many as eight potential lensed objects as part of this investigation "is another potentially important discovery." Harrington points out that discovering gravitational lensing is already like finding a needle in a haystack, because it requires a precise alignment from viewing on Earth. "On top of that, finding lensed sources this bright is as rare as finding the hole in the needle in the haystack."

They also conducted analyses to show that the galaxies' brightness is most likely due solely to their amazingly high rate of star formation. "The Milky Way produces a few solar masses of stars per year, and these objects look like they forming one star every hour," Yun says. Harrington adds, "We still don't know how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects, and studying these objects might help us to find out."

For this work, the team used data from the most powerful international facilities available today to achieve these discoveries, the Planck Surveyor, the Herschel, and the LMT. As Yun explains, the all-sky coverage of the Planck is the only way to find these rare but exceptional objects, but the much higher resolutions of the Herschel and the LMT are needed to pinpoint their exact locations.

He suggests, "If the Planck says there's an object of interest in Boston, the Herschel and LMT have the precision to say that the object is on which table in a particular bar next to Fenway Park." With this information, another LMT instrument called "Redshift Search Receiver" can be deployed to determine how far away and how old these galaxies are and how much gas they contain to sustain their extreme luminosities.

One other aspect of this project is extraordinary, Yun says. "For an undergrad to do this kind of study is really impressive. In 15 years of teaching, I have seen only a few undergraduates who pushed a project to the point of publishing in a major journal article such as this. Kevin deserves a lot of credit for this work."

For his part, Harrington, who will graduate in May with a double major in astronomy and neuroscience, says he plans to start his doctoral work in September at Germany's Max Planck Institute for Astronomy and the University of Bonn, continuing this research on galaxy evolution.

This work was supported by the National Science Foundation, the UMass Amherst Commonwealth Honors College Research Fellowship and Honors Grants, and The William Bannick Student Travel Grant, without which Harrington's two trips to the remote telescope in Mexico would not have been possible, Yun says.

Source : Science Daily

Caltech Researchers Find Evidence of a Real Ninth Planet

This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side.

Credit: Caltech/R. Hurt (IPAC)

Caltech researchers have found evidence of a giant planet tracing a bizarre, highly elongated orbit in the outer solar system. The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of Earth and orbits about 20 times farther from the sun on average than does Neptune (which orbits the sun at an average distance of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun.

The researchers, Konstantin Batygin and Mike Brown, discovered the planet's existence through mathematical modeling and computer simulations but have not yet observed the object directly.

"This would be a real ninth planet," says Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy. "There have only been two true planets discovered since ancient times, and this would be a third. It's a pretty substantial chunk of our solar system that's still out there to be found, which is pretty exciting."

Brown notes that the putative ninth planet—at 5,000 times the mass of Pluto—is sufficiently large that there should be no debate about whether it is a true planet. Unlike the class of smaller objects now known as dwarf planets, Planet Nine gravitationally dominates its neighborhood of the solar system. In fact, it dominates a region larger than any of the other known planets—a fact that Brown says makes it "the most planet-y of the planets in the whole solar system."

Batygin and Brown describe their work in the current issue of the Astronomical Journal and show how Planet Nine helps explain a number of mysterious features of the field of icy objects and debris beyond Neptune known as the Kuiper Belt.

"Although we were initially quite skeptical that this planet could exist, as we continued to investigate its orbit and what it would mean for the outer solar system, we become increasingly convinced that it is out there," says Batygin, an assistant professor of planetary science. "For the first time in over 150 years, there is solid evidence that the solar system's planetary census is incomplete."

The road to the theoretical discovery was not straightforward. In 2014, a former postdoc of Brown's, Chad Trujillo, and his colleague Scott Sheppard published a paper noting that 13 of the most distant objects in the Kuiper Belt are similar with respect to an obscure orbital feature. To explain that similarity, they suggested the possible presence of a small planet. Brown thought the planet solution was unlikely, but his interest was piqued.

He took the problem down the hall to Batygin, and the two started what became a year-and-a-half-long collaboration to investigate the distant objects. As an observer and a theorist, respectively, the researchers approached the work from very different perspectives—Brown as someone who looks at the sky and tries to anchor everything in the context of what can be seen, and Batygin as someone who puts himself within the context of dynamics, considering how things might work from a physics standpoint. Those differences allowed the researchers to challenge each other's ideas and to consider new possibilities. "I would bring in some of these observational aspects; he would come back with arguments from theory, and we would push each other. I don't think the discovery would have happened without that back and forth," says Brown. " It was perhaps the most fun year of working on a problem in the solar system that I've ever had."

Fairly quickly Batygin and Brown realized that the six most distant objects from Trujillo and Sheppard's original collection all follow elliptical orbits that point in the same direction in physical space. That is particularly surprising because the outermost points of their orbits move around the solar system, and they travel at different rates.

"It's almost like having six hands on a clock all moving at different rates, and when you happen to look up, they're all in exactly the same place," says Brown. The odds of having that happen are something like 1 in 100, he says. But on top of that, the orbits of the six objects are also all tilted in the same way—pointing about 30 degrees downward in the same direction relative to the plane of the eight known planets. The probability of that happening is about 0.007 percent. "Basically it shouldn't happen randomly," Brown says. "So we thought something else must be shaping these orbits."

The first possibility they investigated was that perhaps there are enough distant Kuiper Belt objects—some of which have not yet been discovered—to exert the gravity needed to keep that subpopulation clustered together. The researchers quickly ruled this out when it turned out that such a scenario would require the Kuiper Belt to have about 100 times the mass it has today.

That left them with the idea of a planet. Their first instinct was to run simulations involving a planet in a distant orbit that encircled the orbits of the six Kuiper Belt objects, acting like a giant lasso to wrangle them into their alignment. Batygin says that almost works but does not provide the observed eccentricities precisely. "Close, but no cigar," he says.

Then, effectively by accident, Batygin and Brown noticed that if they ran their simulations with a massive planet in an anti-aligned orbit—an orbit in which the planet's closest approach to the sun, or perihelion, is 180 degrees across from the perihelion of all the other objects and known planets—the distant Kuiper Belt objects in the simulation assumed the alignment that is actually observed.

"Your natural response is 'This orbital geometry can't be right. This can't be stable over the long term because, after all, this would cause the planet and these objects to meet and eventually collide,'" says Batygin. But through a mechanism known as mean-motion resonance, the anti-aligned orbit of the ninth planet actually prevents the Kuiper Belt objects from colliding with it and keeps them aligned. As orbiting objects approach each other they exchange energy. So, for example, for every four orbits Planet Nine makes, a distant Kuiper Belt object might complete nine orbits. They never collide. Instead, like a parent maintaining the arc of a child on a swing with periodic pushes, Planet Nine nudges the orbits of distant Kuiper Belt objects such that their configuration with relation to the planet is preserved.

"Still, I was very skeptical," says Batygin. "I had never seen anything like this in celestial mechanics."

But little by little, as the researchers investigated additional features and consequences of the model, they became persuaded. "A good theory should not only explain things that you set out to explain. It should hopefully explain things that you didn't set out to explain and make predictions that are testable," says Batygin.

And indeed Planet Nine's existence helps explain more than just the alignment of the distant Kuiper Belt objects. It also provides an explanation for the mysterious orbits that two of them trace. The first of those objects, dubbed Sedna, was discovered by Brown in 2003. Unlike standard-variety Kuiper Belt objects, which get gravitationally "kicked out" by Neptune and then return back to it, Sedna never gets very close to Neptune. A second object like Sedna, known as 2012 VP113, was announced by Trujillo and Sheppard in 2014. Batygin and Brown found that the presence of Planet Nine in its proposed orbit naturally produces Sedna-like objects by taking a standard Kuiper Belt object and slowly pulling it away into an orbit less connected to Neptune.

A predicted consequence of Planet Nine is that a second set of confined objects should also exist. These objects are forced into positions at right angles to Planet Nine and into orbits that are perpendicular to the plane of the solar system. Five known objects (blue) fit this prediction precisely.
Credit: Caltech/R. Hurt (IPAC) [Diagram was created using WorldWide Telescope.]

But the real kicker for the researchers was the fact that their simulations also predicted that there would be objects in the Kuiper Belt on orbits inclined perpendicularly to the plane of the planets. Batygin kept finding evidence for these in his simulations and took them to Brown. "Suddenly I realized there are objects like that," recalls Brown. In the last three years, observers have identified four objects tracing orbits roughly along one perpendicular line from Neptune and one object along another. "We plotted up the positions of those objects and their orbits, and they matched the simulations exactly," says Brown. "When we found that, my jaw sort of hit the floor."

"When the simulation aligned the distant Kuiper Belt objects and created objects like Sedna, we thought this is kind of awesome—you kill two birds with one stone," says Batygin. "But with the existence of the planet also explaining these perpendicular orbits, not only do you kill two birds, you also take down a bird that you didn't realize was sitting in a nearby tree."

Where did Planet Nine come from and how did it end up in the outer solar system? Scientists have long believed that the early solar system began with four planetary cores that went on to grab all of the gas around them, forming the four gas planets—Jupiter, Saturn, Uranus, and Neptune. Over time, collisions and ejections shaped them and moved them out to their present locations. "But there is no reason that there could not have been five cores, rather than four," says Brown. Planet Nine could represent that fifth core, and if it got too close to Jupiter or Saturn, it could have been ejected into its distant, eccentric orbit.

Batygin and Brown continue to refine their simulations and learn more about the planet's orbit and its influence on the distant solar system. Meanwhile, Brown and other colleagues have begun searching the skies for Planet Nine. Only the planet's rough orbit is known, not the precise location of the planet on that elliptical path. If the planet happens to be close to its perihelion, Brown says, astronomers should be able to spot it in images captured by previous surveys. If it is in the most distant part of its orbit, the world's largest telescopes—such as the twin 10-meter telescopes at the W. M. Keck Observatory and the Subaru Telescope, all on Mauna Kea in Hawaii—will be needed to see it. If, however, Planet Nine is now located anywhere in between, many telescopes have a shot at finding it.

"I would love to find it," says Brown. "But I'd also be perfectly happy if someone else found it. That is why we're publishing this paper. We hope that other people are going to get inspired and start searching."

In terms of understanding more about the solar system's context in the rest of the universe, Batygin says that in a couple of ways, this ninth planet that seems like such an oddball to us would actually make our solar system more similar to the other planetary systems that astronomers are finding around other stars. First, most of the planets around other sunlike stars have no single orbital range—that is, some orbit extremely close to their host stars while others follow exceptionally distant orbits. Second, the most common planets around other stars range between 1 and 10 Earth-masses.

"One of the most startling discoveries about other planetary systems has been that the most common type of planet out there has a mass between that of Earth and that of Neptune," says Batygin. "Until now, we've thought that the solar system was lacking in this most common type of planet. Maybe we're more normal after all."

Brown, well known for the significant role he played in the demotion of Pluto from a planet to a dwarf planet adds, "All those people who are mad that Pluto is no longer a planet can be thrilled to know that there is a real planet out there still to be found," he says. "Now we can go and find this planet and make the solar system have nine planets once again."

The paper is titled "Evidence for a Distant Giant Planet in the Solar System."

Written by Kimm Fesenmaier

Chinese rover analyzes moon rocks: First new ‘ground truth’ in 40 years

The Chinese lunar rover, Yutu, photographed by its lander Chang’e-3, after the lander touched down in Mare Imbrium, a giant impact basin that had been filled by successive lava flows.

Credit: CNsa/CLEP

In 2013, Chang'e-3, an unmanned lunar mission, touched down on the northern part of the Imbrium basin, one of the most prominent of the lava-filled impact basins visible from Earth.

It was a beautiful landing site, said Bradley L. Jolliff, PhD, the Scott Rudolph Professor of Earth and Planetary Sciences at Washington University in St. Louis, who is a participant in an educational collaboration that helped analyze Chang'e-3 mission data. The lander touched down on a smooth flood basalt plain next to a relatively fresh impact crater (now officially named the Zi Wei crater) that had conveniently excavated bedrock from below the regolith for the Yutu rover to study.

Since the Apollo program ended, American lunar exploration has been conducted mainly from orbit. But orbital sensors mostly detect the regolith (the ground-up surface layer of fragmented rock) that blankets the Moon, and the regolith is typically mixed and difficult to interpret.

Because Chang'e-3 landed on a comparatively young lava flow, the regolith layer was thin and not mixed with debris from elsewhere. Thus it closely resembled the composition of the underlying volcanic bedrock. This characteristic made the landing site an ideal location to compare in situ analysis with compositional information detected by orbiting satellites.

"We now have 'ground truth' for our remote sensing, a well-characterized sample in a key location," Jolliff said. "We see the same signal from orbit in other places, so we now know that those other places probably have similar basalts."

The basalts at the Chang'e-3 landing site also turned out to be unlike any returned by the Apollo and Luna sample return missions.

"The diversity tells us that the Moon's upper mantle is much less uniform in composition than Earth's," Jolliff said. "And correlating chemistry with age, we can see how the Moon's volcanism changed over time."

Two partnerships were involved in the collection and analysis of this data, published in the journal Nature Communications Dec. 22. Scientists from a number of Chinese institutions involved with the Chang'e-3 mission formed one partnership; the other was a long-standing educational partnership between Shandong University in Weihai, China, and Washington University in St. Louis.

A mineralogical mystery

The Moon, thought to have been created by the collision of a Mars-sized body with the Earth, began as a molten or partially molten body that separated as it cooled into a crust, mantle and core. But the buildup of heat from the decay of radioactive elements in the interior then remelted parts of the mantle, which began to erupt onto the surface some 500 million years after the Moon's formation, pooling in impact craters and basins to form the maria, most of which are on the side of the Moon facing the Earth.

The American Apollo (1969-1972) and Russian Luna (1970-1976) missions sampled basalts from the period of peak volcanism that occurred between 3 and 4 billion years ago. But the Imbrium basin, where Chang'e-3 landed, contains some of the younger flows -- 3 billion years old or slightly less.

The basalts returned by the Apollo and Luna missions had either a high titanium content or low to very low titanium; intermediate values were missing. But measurements made by an alpha-particle X-ray spectrometer and a near-infrared hyperspectral imager aboard the Yutu rover indicated that the basalts at the Chang'e-3 landing site are intermediate in titanium, as well as rich in iron, said Zongcheng Ling, PhD, associate professor in the School of Space Science and Physics at Shandong University in Weihai, and first author of the paper.

Titanium is especially useful in mapping and understanding volcanism on the Moon because it varies so much in concentration, from less than 1 weight percent TiO2 to over 15 percent. This variation reflects significant differences in the mantle source regions that derive from the time when the early magma ocean first solidified.

Minerals crystallize from basaltic magma in a certain order, explained Alian Wang, PhD, research professor in earth and planetary sciences in Arts & Sciences at Washington University. Typically, the first to crystallize are two magnesium- and iron-rich minerals (olivine and pyroxene) that are both a little denser than the magma, and sink down through it, then a mineral (plagioclase feldspar), that is less dense and floats to the surface. This process of separation by crystallization led to the formation of the Moon's mantle and crust as the magma ocean cooled.

The titanium ended up in a mineral called ilmenite (FeTiO3) that typically doesn't crystallize until a very late stage, when perhaps only 5 percent of the original melt remains. When it finally crystallized, the ilmenite-rich material, which is also dense, sank into the mantle, forming areas of Ti enrichment.

"The variable titanium distribution on the lunar surface suggests that the Moon's interior was not homogenized," Jolliff said. "We're still trying to figure out exactly how this happened. Possibly there were big impacts during the magma ocean stage that disrupted the mantle's formation."

Another clue to the Moon's past

The story has another twist that also underscores the importance of checking orbital data against ground truth. The remote sensing data for Chang'e-3's landing site showed that it was rich in olivine as well as titanium.

That doesn't make sense, Wang said, because olivine usually crystallizes early and the titanium-rich ilmenite crystallizes late. Finding a rock that is rich in both is a bit strange.

But Yutu solved this mystery as well. In olivine, silicon is paired with either magnesium or iron but the ratio of those two elements is quite variable in different forms of the mineral. The early-forming olivine would be magnesium rich, while the olivine detected by Yutu has a composition that ranges from intermediate in iron to iron-rich.

"That makes more sense," Jolliff said, "because iron-enriched olivine and ilmenite are more likely to occur together.

"You still have to explain how you get to an olivine-rich and ilmenite-rich rock. One way to do that would be to mix, or hybridize, two different sources," he said.

The scientists infer that late in the magma-ocean crystallization, iron-rich pyroxene and ilmenite, which formed late and at the crust-mantle boundary, might have begun to sink, and early-formed magnesium-rich olivine might have begun to rise. As this occurred, the two minerals might have mixed and hybridized.

"Given these data, that is our interpretation," Jolliff said.

In any case, it is clear that these newly characterized basalts reveal a more diverse Moon than the one that emerged from studies following the Apollo and Luna missions. Remote sensing suggests that there are even younger and even more diverse basalts on the Moon, waiting for future robotic or human explorers to investigate, Jolliff said.

Article Credits: Science Daily

What's the resolution of the human eye?

Well, the answer is pretty simple; there is indeed a tipping point after which upping the resolution of video doesn’t make any sense. Our eyes are for example not able to detect resolutions above the 4K(about 8.3 megapixel), but what is the resolution of our eyes?

In short it boils down to the fact that in our field of vision we are able to register 576 megapixels, but our eyes will trim this resolution down to 7 megapixels. Our eyes will make the rest of our field of vision hazy, in this manner our brain can handle the information and won’t overload.

From this point of view 4K is the very limit of what we can perceive normally with the naked eye. Although the difference between 4K and 5K or 10K – 14.7 megapixel or 80 megapixel) – may seem impressive but with our ‘limited’ view we are not able to see the difference with the naked eye.

A higher amount of pixels also means the color spectrum is doubled, which results into a more realistic experience

But although we are not able to register the higher amount of megapixels it also entails a real advantage. This benefit is related to the fact that, despite that thousands of retina cells in our eyeballs capture the visual information (similar to a camera lens, it is our brain that eventually creates one coherent experience of what we see. In this manner a higher amount of megapixels will result in a more realistic experience.

This is due to the fact that a larger amount of pixels also results in a higher number of colors that can represent. In other words, the color spectrum on the screen is doubled and is comes much closer to the way we perceive reality.

To learn more about the resolution of the human eye, be sure to check out the video below!

Article Credits : Science Dump

Ultracold Big Bang experiment successfully simulates evolution of early universe

Physicists have reproduced a pattern resembling the cosmic microwave background radiation in a laboratory simulation of the Big Bang, using ultracold cesium atoms in a vacuum chamber at the University of Chicago.

“This is the first time an experiment like this has simulated the evolution of structure in the early universe,” said Cheng Chin, professor in physics. Chin and his associates reported their feat in the Aug. 1 edition of Science Express, and it will appear soon in the print edition of Science.

Chin pursued the project with lead author Chen-Lung Hung, PhD’11, now at the California Institute of Technology, and Victor Gurarie of the University of Colorado, Boulder. Their goal was to harness ultracold atoms for simulations of the Big Bang to better understand how structure evolved in the infant universe.

The cosmic microwave background is the echo of the Big Bang. Extensive measurements of the CMB have come from the orbiting Cosmic Background Explorer in the 1990s, and later by the Wilkinson Microwave Anisotropy Probe and various ground-based observatories, including the UChicago-led South Pole Telescope collaboration. These tools have provided cosmologists with a snapshot of how the universe appeared approximately 380,000 years following the Big Bang, which marked the beginning of our universe.

It turns out that under certain conditions, a cloud of atoms chilled to a billionth of a degree above absolute zero (-459.67 degrees Fahrenheit) in a vacuum chamber displays phenomena similar to those that unfolded following the Big Bang, Hung said.

“At this ultracold temperature, atoms get excited collectively. They act as if they are sound waves in air,” he said. The dense package of matter and radiation that existed in the very early universe generated similar sound-wave excitations, as revealed by COBE, WMAP and the other experiments.

The synchronized generation of sound waves correlates with cosmologists’ speculations about inflation in the early universe. “Inflation set out the initial conditions for the early universe to create similar sound waves in the cosmic fluid formed by matter and radiation,” Hung said.

BIG BANG’S RIPPLING ECHO

The sudden expansion of the universe during its inflationary period created ripples in space-time in the echo of the Big Bang. One can think of the Big Bang, in oversimplified terms, as an explosion that generated sound, Chin said. The sound waves began interfering with each other, creating complicated patterns. “That’s the origin of complexity we see in the universe,” he said.

These excitations are called Sakharov acoustic oscillations, named for Russian physicist Andrei Sakharov, who described the phenomenon in the 1960s. To produce Sakharov oscillations, Chin’s team chilled a flat, smooth cloud of 10,000 or so cesium atoms to a billionth of a degree above absolute zero, creating an exotic state of matter known as a two-dimensional atomic superfluid.

Then they initiated a quenching process that controlled the strength of the interaction between the atoms of the cloud. They found that by suddenly making the interactions weaker or stronger, they could generate Sakharov oscillations.

The universe simulated in Chin’s laboratory measured no more than 70 microns in diameter, approximately the diameter as a human hair. “It turns out the same kind of physics can happen on vastly different length scales,” Chin explained. “That’s the power of physics.”

The goal is to better understand the cosmic evolution of a baby universe, the one that existed shortly after the Big Bang. It was much smaller then than it is today, having reached a diameter of only a hundred thousand light years by the time it had left the CMB pattern that cosmologists observe on the sky today.

In the end, what matters is not the absolute size of the simulated or the real universes, but their size ratios to the characteristic length scales governing the physics of Sakharov oscillations. “Here, of course, we are pushing this analogy to the extreme,” Chin said.

380,000 YEARS VERSUS 10 MILLISECONDS

“It took the whole universe about 380,000 years to evolve into the CMB spectrum we’re looking at now,” Chin said. But the physicists were able to reproduce much the same pattern in approximately 10 milliseconds in their experiment. “That suggests why the simulation based on cold atoms can be a powerful tool,” Chin said.

None of the Science co-authors are cosmologists, but they consulted several in the process of developing their experiment and interpreting its results. The co-authors especially drew upon the expertise of UChicago’s Wayne Hu, John Carlstrom and Michael Turner, and of Stanford University’s Chao-Lin Kuo.

Hung noted that Sakharov oscillations serve as an excellent tool for probing the properties of cosmic fluid in the early universe. “We are looking at a two-dimensional superfluid, which itself is a very interesting object. We actually plan to use these Sakharov oscillations to study the property of this two-dimensional superfluid at different initial conditions to get more information.”

The research team varied the conditions that prevailed early in the history of the expansion of their simulated universes by quickly changing how strongly their ultracold atoms interacted, generating ripples. “These ripples then propagate and create many fluctuations,” Hung said. He and his co-authors then examined the ringing of those fluctuations.

Today’s CMB maps show a snapshot of how the universe appeared at a moment in time long ago. “From CMB, we don’t really see what happened before that moment, nor do we see what happened after that,” Chin said. But, Hung noted, “In our simulation we can actually monitor the entire evolution of the Sakharov oscillations.”

Chin and Hung are interested in continuing this experimental direction with ultracold atoms, branching into a variety of other types of physics, including the simulation of galaxy formation or even the dynamics of black holes.

“We can potentially use atoms to simulate and better understand many interesting phenomena in nature,” Chin said. “Atoms to us can be anything you want them to be.”-

Source :University of Chicago.

By Science and Universe

Cassini Data: Saturn Moon May Have Rigid Ice Shell

This image of the surface of Saturn's moon Titan was obtained by the European Space Agency's

Huygens Probe on Jan. 14, 2005, after it was delivered to Titan by NASA's Cassini spacecraft.

Image Credit: 

ESA/NASA/JPL/University of Arizona

An analysis of gravity and topography data from the Saturnian moon Titan obtained by NASA's Cassini spacecraft suggests there could be something unexpected about the moon's outer ice shell. The findings, published on Aug. 28 in the journal Nature, suggest that Titan's ice shell could be rigid, and that relatively small topographic features on the surface could be associated with large ice "roots" extending into the underlying ocean.

The study was led by planetary scientists Douglas Hemingway and Francis Nimmo at the University of California, Santa Cruz, who used data from Cassini. The researchers were surprised to find a counterintuitive relationship between gravity and topography.

"Normally, if you fly over a mountain, you expect to see an increase in gravity due to the extra mass of the mountain," said Nimmo, a Cassini participating scientist. "On Titan, when you fly over a mountain, the gravity gets lower. That's a very odd observation."

One potential explanation is that each bump in the topography on the surface of Titan is offset by a deeper "root" that is big enough to overwhelm the gravitational effect of the bump on the surface. The root could act like an iceberg extending below the ice shell into the ocean underneath it. In this model, Cassini would detect less gravity wherever there is a big chunk of ice rather than water because ice is less dense than water.

"It's like a big beach ball under the ice sheet pushing up on it, and the only way to keep it submerged is if the ice sheet is strong," said Hemingway, the paper's lead author and a Cassini team associate. "If large roots under the ice shell are the explanation, this means that Titan's ice shell must have a very thick rigid layer."

If these findings are correct, a thick rigid ice shell makes it very difficult to have ice volcanoes, which some scientists have proposed to explain other features seen on the surface. They also suggest that convection or plate tectonics are not recycling Titan's ice shell, as they do with Earth's geologically active crust.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington.

More information on Cassini can be found at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Source : NASA
By Science and Universe

LADEE Fully Stacked on Minotaur V

The LADEE spacecraft in the nose-cone at the top of the full Minotaur V launch vehicle stack. LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.
Image Credit: NASA Wallops / Terry Zaperach

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is now in the nose-cone at the top of the full Minotaur V launch vehicle stack at the Wallops Flight Facility in Virginia, awaiting a launch at 11:27 p.m. EDT on Sept. 6, 2013. 

Engineers at NASA's Wallops Flight Facility in Virginia prepare to encapsulate the LADEE spacecraft into the fairing of the Minotaur V launch vehicle nose-cone.
Image Credit: NASA Wallops / Terry Zaperach

Engineers at NASA's Wallops Flight Facility in Virginia encapsulate NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft into the fairing of the Minotaur V launch vehicle nose-cone.
Image Credit: NASA Wallops / Terry Zaperach.

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft sits in the nose-cone at the top of the full Minotaur V launch vehicle stack.
Image Credit:
NASA Ames / Zion Young

LADEE is a robotic mission that will orbit the moon to gather detailed information about the lunar atmosphere, conditions near the surface and environmental influences on lunar dust. A thorough understanding of these characteristics will address long-standing unknowns, and help scientists understand other planetary bodies as well.

LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.

The probe will launch on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corp. of Dulles, Va., from NASA's Wallops Flight Facility. 

Source : NASA

By Science and Universe

Lunar Atmosphere and Dust Environment Explorer

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In an attempt to answer prevailing questions about our moon, NASA is making final preparations to launch a probe at 11:27 p.m. EDT Friday, Sept. 6, 2013, from NASA's Wallops Flight Facility on Wallops Island, Va.

The small car-sized Lunar Atmosphere and Dust Environment Explorer (LADEE) is a robotic mission that will orbit the moon to gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.

In this photo, engineers as NASA's Wallops Flight Facility in Virginia encapsule the LADEE spacecraft into the fairing of the Minotaur V launch vehicle nose-cone. LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.

Image credit: NASA Wallops / Terry Zaperach

By Science and Universe

THE RE-ENTRY TEST IXV

Europe's newest spacecraft, the IXV, or Intermediate eXperimental Vehicle, has moved a step closer to its planned launch in 2014.

The craft completed a pre-launch test off the coast of Sardinia, which involved it being dropped into the Mediterranean from a height of 3,000 metres.

For the most part the vehicle performed perfectly during the test, with parachutes deploying as expected. However, just after splashdown a problem arose, as the inflatable devices which should add support to the buoyant IXV once it is in the water had failed to inflate.

It was a dramatic and initially confusing result, but after some head-scratching the engineers involved in the test began to understand what had happened. They believed that the balloons had not inflated because the setting for the sensors that detect the impact with the water was too high. So, splashdown was quite simply a little too gentle.

IXV Programme Manager for ESA, Giorgio Tumino explained: "There has been a lot of discussion around this, because we have to differentiate the shock induced by the impact with the water from the shock that could be induced by wind gusts to the parachute, because these are very similar levels in terms of shock and we have to differentiate those levels. We had set these thresholds quite high, and while my impression, my visual impression of what happened was that the landing was very soft because the parachute is really working fine, so probably the impact loads were much lower than what we expected."

Roberto Angelini from Thales Alenia Space was happy with the test overall: "We demonstrated what we wanted to demonstrate; free fall condition initially, you see the parachute compartment where we had the extraction of the parachute system. The slings of the parachute that are covered by a thermal protection system to sustain the heat of the re-entry, we wanted to test how this thing was going to be broken. And you see here the flotation devices that are activated right after the splashdown itself. Now, if there is something we will have to fix coming out from the post review board etc we will implement it in the flight hardware."

A post-flight review confirmed Tumino's theory. The impact loads during splashdown were lower than expected - the computers recorded an impact deceleration of 29.1 m/s2, and the threshold for the flotation of the balloons was set at 30 m/s2

A lot is riding on the IXV prototype, as it represents a new chapter in space flight technology for the European Space Agency.

The idea is to have an affordable, small spacecraft that can enter near-Earth orbit and then land in a targeted zone. This test was just one step in that development. In 2014 the IXV will be launched into space on board a Vega rocket and then re-enter the atmosphere, splashing down in the Pacific Ocean.