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Entries from April 3, 2011 - April 9, 2011


Beyond Hubble! Internet Space Observatory to Open a Movie-like Window on the Universe  

"LSST is truly an Internet telescope, which will put terabytes of data each night into the hands of anyone that wants to explore it. The 8.4-metre LSST telescope and the 3-gigapixel camera are thus a shared resource for all humanity — the ultimate network peripheral device to explore the universe."

Bill Gates -Microsoft co-founder.

The Large Synoptic Survey Telescope, partially funded by $30 million from Microsoft founders Bill gates and Charles Simyoni, the developer of Word and Excel, is projected for ‘first light’ in 2014 in Chile's Atacama Desert -the world's Southern Hemisphere space-observatory mecca. The 8.4-meter telescope will be able to survey the entire visible sky deeply in multiple colors every week with its 3-billion pixel digital camera. The telescope will probe the mysteries of dark matter and dark energy, and it will open a movie-like window on objects that change or move rapidly: exploding supernovae, potentially hazardous near-Earth asteroids and distant Kuiper Belt objects.

‘What a shock it was when Galileo saw in his telescope the phases of Venus, or the moons of Jupiter, the first hints of a dynamic universe,’ Simonyi said. "Today, by building a special telescope-computer complex, we can study this dynamism in unprecedented detail. LSST will produce a database suitable for answering the wide range of pressing questions: What is dark energy? What is dark matter? How did the Milky Way form? What are the properties of small bodies in the solar system? Are there potentially hazardous asteroids that may impact the Earth, causing significant damage? What sort of new phenomena have yet to be discovered? "

The telescope will be constructed on Cerro Pachon, a mountain in northern Chile. Its design of three large mirrors and three refractive lenses in a camera leads to a 10-square-degree field of view with excellent image quality. The telescope’s 3,200-megapixel camera will be the largest digital camera ever constructed.

LSST is designed to be a public facility. The database and resulting cataloges will be made available to the public with no proprietary restrictions. A sophisticated data management system will provide easy access, enabling simple queries from individual users. The public will actively share the adventure of discovery.

The wide-field imaging telescope now known as the LSST was originally designed at the UA by Regents’ Professor of Astronomy Roger Angel. UA astronomer Philip Pinto is responsible for simulating the telescope’s operation to develop new scientific strategies and to ensure that the instrument works as intended. The UA was one of the four founding members of the LSST Corporation in spring 2003.

Source: http://www.dailygalaxy.com/my_weblog/2011/04/beyond-hubble-internet-space-observatory-to-open-a-movie-like-window-on-the-universe-.html


Trillions of Earths Orbiting Red Dwarfs

"There are possibly trillions of Earths orbiting these stars." -Yale University astronomer Pieter van Dokkum.

Van Dokkum also said that the red dwarfs they have discovered are over 10 billion years old, which means they've had enough time for complex life to develop and evolve, summarizing about research recently conducted at Hawaii's Keck Observatory that discovered that the number of stars in the universe is triple what was previously thought. Until recently, red dwarf stars were not detectable in galaxies outside our own nearby cluster because they are relatively small and dim. Thus, researchers were not able to comprise a total number of red dwarfs present in the universe.

However, astronomers are now able to observe nearby elliptical galaxies using powerful telescopes at the Keck Observatory in Hawaii. These instruments were able to detect the faint signatures of red dwarf stars in eight massive ellipticals that lie about 50,000 and 300 million light-years away.

In their observations, the scientists realized that red dwarfs were much more abundant than they had expected.

"No one knew how many of these stars there were," said  van Dokkum, who led the research in this study.

"Different theoretical models predicted a wide range of possibilities, so this answers a longstanding question about just how abundant these stars are."

The results determined that there are about 20 times more red dwarfs in elliptical galaxies than there are in the Milky Way, explained Charlie Conroy of Hardvard-Smithsonian Center for Astrophysics. This also means that these galaxies may contain less dark matter than was previously measured, since more space is filled with the mass of these red dwarfs.

Since the number of stars is now known to be more bountiful, the number of planets orbiting red dwarfs is also elevated. This, of course, also raises the number of possible life-harboring planets there might be, van Dokkum added.

As a matter of fact, the recently discovered exoplanet, which astronomers believe is capable of sustaining life, orbits the red dwarf star named Gliese 581.

Red dwarfs have been prime hunting grounds in the search for Earth's Twin. Extrasolar planets were discovered orbiting Gliese 581 in 2005, about the mass of Neptune, or sixteen Earth masses. It orbits just 6 million kilometers (0.04 AU) from its star, and is estimated to have a surface temperature of 150 °C, despite the dimness of the star.

So far, among the 500 plus exo-planets discovered none have shown themselves to be twin Earths. But, in the next two to three years NASA’s Kepler space telescope will provide the statistical bedrock for estimating the number of Earth clones in the galaxy.

But the Kepler planets will be too far away –- hundreds or thousand of light-years -- for any follow-up observations to be able to determine if they are inhabited. All we will have from the Kepler data is planet mass, diameter, orbital period, and parent star type. The Earth clones will forever remain a blip on the exoplanet radar when it comes to determining true habitability.

But enough exoplanet research has been done so far that a cautious prediction can be made that the odds are that the planet will orbit an M (red) dwarf star found in surveys taken within 100 light-years of Earth. Red dwarfs are much more numerous than sun-like stars, which exponentially increases the chances of being life favorable. 

M dwarfs make up at least 70% of the Milky Way's stars. Their masses range from roughly half to one-twentieth the mass of our sun, but what M dwarfs lack in size, they more than make up for in longevity. Astronomers estimate that these stars can burn for 40 billion to 100 billion years, giving any habitable planets plenty of time to evolve life. (The life span of our own sun, a G-class star, is about 10 billion years.) But during at least the first few billion years of their lives, M dwarfs also sport huge magnetic fields that routinely interact with their atmospheres to create coronal mass ejections—enormous outbursts of matter from the star's highly ionized corona—and proton-rich flares.

The planet will be in the habitable, "goldilocks" zone around a red dwarf – the zone where liquid water can remain stable on a planet’s surface. The zone will be closer to the cool red dwarf than the Earth's habitable zone to our Sun.

The profile of a planet in the habitable zone of a red dwarf includes an orbit completed in a mere two weeks, which will provide astronomers with multiple transits to enhance odds of being observed as well as , being more likely to be in an orbit aligned along our Earth-bound line of sight.

Because they are much cooler than our sun, any potentially habitable planet would need to orbit them much closer than Earth does, putting it smack in the danger zone. But a new study indicates that these planets may be unexpectedly shielded from solar activity, keeping life safe.

"Overall, this is excellent news for planet hunters," says Alan Boss, a planetary scientist at the Carnegie Institution for Science in Washington, D.C., who was not involved with the study and who is part of NASA's Kepler mission to search for Earth-like planets. "This further buttresses the case that the first truly habitable world we find will likely by around a nearby M dwarf."

To find out if this solar nightmare would destroy any nearby habitable worlds, researchers led by astrobiologist Antigona Segura of the Universidad Nacional Autónoma de México (UNAM) in Mexico City turned to a computer model. The team simulated how a 1985 flare from AD Leonis (AD Leo), an M dwarf 16 light-years from Earth, would have affected a hypothetical Earth-like planet orbiting 0.16 astronomical units from the star. That's less than half Mercury's distance around the sun.

The simulation indicated that M dwarf stars are not as dangerous as feared. "When UV radiation from the star's upper atmosphere encountered the Earth-like atmosphere of our model planet, the energy resulted in a thicker ozone layer in the planetary atmosphere, providing a natural shield for the planetary surface," says astronomer Lucianne Walkowicz, a Kepler postdoctoral fellow at the University of California, Berkeley. That's because the UV radiation actually split molecules of oxygen to create more ozone than it destroyed. "Throughout most of the flare, the surface of our model Earth-like planet experienced no more radiation than is typical on a sunny day here on Earth," Walkowicz says.

The findings are especially good news, says Segura, because AD Leo is a young star—less than 300 million years old—and as a result is one of the most active M dwarfs known. The star's 1985 flare was 1000 times as energetic as a similar flare on our own sun. So the fact that the model planet's atmosphere survived such a violent event may bode well for planets around similar young M dwarfs, she says.

Young red dwarfs have awesome stellar flares that can erupt without warning and blast out lethal doses of ultraviolet radiation destroying surface life. Ocean life, however, may be safe from the UV just a few feet underwater and still extract enough light for photosynthesis.

In summary, he found that UV radiation actually split molecules of oxygen to create more ozone than it destroyed. The simulation made a thicker ozone layer in the planetary atmosphere such that the surface experienced no more radiation than is typical on a sunny day on Earth. What’s more, as the dwarf settles down to a quiescent existence, there would be very little ultraviolet light and an UV filtering ozone layer would not even be needed.

However, potentially habitable red dwarf planets may keep one hemisphere locked onto their star due to gravitational tidal forces. The resulting slow rotation may give them anaemic magnetic fields that do not block cosmic rays effectively.

The answers may be coming soon via the James Webb Space Telescope, scheduled for launch in 2014, would be used to spectroscopically 'sniff' out the exoplanet's atmosphere for chemistry that might be a by-product of organisms on the surface. If these planets develop a natural UV shield, then the discovery of an inhabited world may be no more than a decade away.

Source: http://www.dailygalaxy.com/my_weblog/2010/12/trillions-of-earths-orbiting-red-dwarfs-presence-in-universe-tripled-by-new-discovery-.html


The Massive Planet of Beta Pictoris

The dense clouds of carbon enveloping a nearby massive star, Beta Pictoris, hint that the star may be aggregating new planets, according to a past study led by Aki Roberage of the NASA Goddard Space Flight Center. Only 12 million years old, the 'baby star' Beta Pictoris is located about 70 light-years away towards the constellation Pictor (the Painter).

Goddard's Marc Kucher said "If carbon-rich worlds are forming in Beta Pictoris, they might be covered with tar and smog, with mountains made of giant diamonds...Life on such a planet is not implausible, but it would certainly be exotic."

In November of 2008, a team of French astronomers using ESO's Very Large Telescope have discovered an object located very close to the star Beta Pictoris, and which apparently lies inside its disc. With a projected distance from the star of only 8 times the Earth-Sun distance, this object is most likely the giant planet suspected from the peculiar shape of the disc and the previously observed infall of comets onto the star. It would then be the first image of a planet that is as close to its host star as Saturn is to the Sun.

Astronomers have long suspected that the young, 12-million-year-old star hosts a massive planet, since it is surrounded by a dusty disc of debris thought to be created by the collision of rocky bodies and infalling comets.

Evidence for such a planet grew stronger in 2006, when astronomers reported finding what appeared to be a second, smaller dusty disc around the star that was tilted slightly with respect to the main disc. It may have formed after a planet between 1 and 20 times the mass of Jupiter was thrown out of the main disc by gravitational interactions with other bodies there.

French astronomers say they may have spotted the suspected planet by reanalysing infrared observations of the star first made in 2003 with the Very Large Telescope in Chile. An adaptive optics system, which uses a shape-shifting mirror to offset turbulence in the atmosphere, was used to take the images.

Earlier observations showed a warp of the disc, a secondary inclined disc and infalling comets onto the star. "These are indirect, but tell-tale signs that strongly suggest the presence of a massive planet lying between 5 and 10 times the mean Earth-Sun distance from its host star," says team leader Anne-Marie Lagrange of Grenoble Observatory in France . "However, probing the very inner region of the disc, so close to the glowing star, is a most challenging task.We were able to achieve this after a precise and drastic selection of the best images recorded during our observations."

The team found a point-like glow around the star that might be a planet weighing about 8 Jupiters. The object appears to lie about as far from its star as Saturn does to the Sun - or about 8 astronomical units (where 1 AU is the Earth-Sun distance), closer to its star than any other extrasolar planet ever imaged.

"We cannot rule out definitively . . . that the candidate companion could be a foreground or background object," said team member Gael Chauvin. "To eliminate this very small possibility, we will need to make new observations that confirm the nature of the discovery."

Source: http://www.stumbleupon.com/su/28L0iY/www.dailygalaxy.com/my_weblog/2011/04/weekend-feature-image-the-massive-planet-of-beta-pictoris.html


Halos Gone MAD

Distribution of dark matter when the Universe was about 3 billion years old, obtained from a numerical simulation of galaxy formation. The left panel displays the continuous distribution of dark matter particles, showing the typical wispy structure of the cosmic web, with a network of sheets and filaments, while the right panel highlights the dark matter halos representing the most efficient cosmic sites for the formation of star-bursting galaxies with a minimum dark matter halo mass of 300 billion times that of the Sun. Credit: VIRGO Consortium/Alexandre Amblard/ESAOne of the successes of the ΛCDM model of the universe is the ability for models to create structures of with scales and distributions similar to those we view in the universe today. Or, at least that’s what astronomers tell us. While computer simulations can recreate numerical universes in a box, interpreting these mathematical approximations is a challenge in and of itself. To identify the components of the simulated space, astronomers have had to develop tools to search for structure. The results has been nearly 30 independent computer programs since 1974. Each promises to reveal the forming structure in the universe by finding regions in which dark matter halos form. To test these algorithms out, a conference was arranged in Madrid, Spain during the May of 2010 entitled “Haloes going MAD” in which 18 of these codes were put to the test to see how well they stacked up.

Numerical simulations for universes, like the famous Millennium Simulation begin with nothing more than “particles”. While these were undoubtedly small on a cosmological scale, such particles represent blobs of dark matter with millions or billions solar masses. As time is run forwards, they are allowed to interact with one another following rules that coincident with our best understanding of physics and the nature of such matter. This leads to an evolving universe from which astronomers must use the complicated codes to locate the conglomerations of dark matter inside which galaxies would form.

One of the main methods such programs use is to search for small overdensities and then grow a spherical shell around it until the density falls off to a negligible factor. Most will then prune the particles within the volume that are not gravitationally bound to make sure that the detection mechanism didn’t just seize on a brief, transient clustering that will fall apart in time. Other techniques involve searching other phase spaces for particles with similar velocities all nearby (a sign that they have become bound).

To compare how each of the algorithms fared, they were put through two tests. The first, involved a series of intentionally created dark matter halos with embedded sub-halos. Since the particle distribution was intentionally placed, the output from the programs should correctly find the center and size of the halos. The second test was a full fledged universe simulation. In this, the actual distribution wouldn’t be known, but the sheer size would allow different programs to be compared on the same data set to see how similarly they interpreted a common source.

In both tests, all the finders generally performed well. In the first test, there were some discrepancies based on how different programs defined the location of the halos. Some defined it as the peak in density, while others defined it as a center of mass. When searching for sub-halos, ones that used the phase space approach seemed to be able to more reliably detect smaller formations, yet did not always detect which particles in the clump were actually bound. For the full simulation, all algorithms agreed exceptionally well. Due to the nature of the simulation, small scales weren’t well represented so the understanding of how each detect these structures was limited.

The combination of these tests did not favor one particular algorithm or method over any other. It revealed that each generally functions well with regard to one another. The ability for so many independent codes, with independent methods means that the findings are extremely robust. The knowledge they pass on about how our understanding of the universe evolves allows astronomers to make fundamental comparisons to the observable universe in order to test the such models and theories.

The results of this test have been compiled into a paper that is slated for publication in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

Source: http://www.universetoday.com/84698/halos-gone-mad/


40-Year-Old Mystery of Massive Gamma-Ray Burst Solved  

Studies have shown that neutron stars often exist as pairs on the fringes of galaxies, and that they collide frequently, sometimes involving a black hole, also a stellar remnant but one that is much more dense. Neutron stars are often as small as the island of Manhattan with a teaspoon of its material weighing several tons.

A German supercomputer cluster at the Albert Einstein Institute in Germany models events that unfold in just 35 milliseconds -- three times faster than the blink of an eye, has finally solved the Gamma-ray burst mystery by showing that colliding neutron stars can produce magnetic structures which are responsible for the cosmic event, says a NASA study.

Gamma-ray bursts are among the most energetic cosmic events known, emitting as much energy in a few seconds as our entire galaxy does in a year, most of it in the form of Gamma rays, the highest energy form of light.

"For the first time, we''ve managed to run the simulation well past the merger and the formation of the black hole," said the study''s co-author Chryssa Kouveliotou at the US space agency''s Marshall Space Flight Center in Huntsville. "This is by far the longest simulation of this process, and only on sufficiently long timescales does the magnetic field grow and reorganize itself from a chaotic structure into something resembling a jet," she added.

GRBs lasting longer than two seconds are widely thought to be triggered by the collapse of a massive star into a black hole. As matter falls toward black hole, some of it forms jets in the opposite direction that move near the speed of light and produce a blast of Gamma rays as they emerge.

"For more than two decades, the leading model of short GRBs was the merger of two neutron stars. Only now can we show the merger of neutron stars actually produces an ultrastrong magnetic field structured like jets needed for a GRB," Bruno Giacomazzo at NASA''s Goddard Space Flight Center said.

Several GRBs are recorded every day, coming from all directions. Most originate in the very distant universe. A GRB burst closer than 10 light years could trigger a mass extinction on Earth.

Gamma rays are the most intense form of radiation, more powerful than X-rays. The afterglow of a single burst, measured in X-rays, radio waves and other wavelengths, can be billions of times brighter than the entire galaxy in which it originates. Long-duration GRBs typically last about 20 seconds, released when the core of a young and very massive star collapses in a supernova event.

"Gamma-ray bursts in general are notoriously difficult to study, but the shortest ones have been next to impossible to pin down," said Neil Gehrels of NASA Goddard Space Flight Center. "All that has changed. We now have the tools in place to study these events."

Back in 2005, Astronomers observed two short-duration bursts that took place on the outskirts of a faraway galaxy, a location where old stellar remnants like neutron stars are known to reside,
in unprecedented detail and determined the likely scenario in which two dense objects collide and coalesce. The discovery involved more than 30 researchers at 16 institutions and a host of telescopes on the ground and in space. 

"The observed characteristics of the short gamma-ray bursts are all consistent with models of the merger of two neutron stars, or of a neutron star with a black hole," said Piro, of the Instituto Astrofisica Spaziale in Rome.

The first burst was detected May 9, 2005 by NASA's Swift satellite. Scientists believed that morning that they were seeing, live, the merger of two neutron stars into a single black hole.

Another burst on July 9, 2005 was noted by the HETE-2 satellite, an international project run by NASA. It lasted just a tenth of a second, but was the first event for which an accurate distance is known. An afterglow of optical light from the same location was spotted by other telescopes, representing the first visible light ever associated with a short-duration burst.

At a billion light-years away, it was about 10 times closer than nearly all other recorded GRBs. Calculations also show, however, that it was about 1,000 times less energetic than the others. Too weak, in fact, to have come from a single exploding massive star, helping astronomers determine that it likely involved a merger of two old stars, as theory predicts. For every event astronomers spot, 30 other mergers go undetected.

"The mystery of short gamma-ray bursts is largely solved," said Don Lamb, a University of Chicago researcher and co-author of one of four papers describing the observations.

Albert Einstein predicted that when neutron stars collide, a shock of gravitational waves should be released. An observatory called LIGO is ramping up in an effort to detect these waves.

"It's possible now that the first gravitational wave source that LIGO observes will also be a gamma-ray burst source," said Kevin Hurley of the University of California at Berkeley. "Now that would be a spectacular discovery."

Source: http://www.stumbleupon.com/su/2eSjYi/www.dailygalaxy.com/my_weblog/2011/04/newsflash-massive-gamma-ray-burst-mystery-solved.html