Milky Way's super-efficient particle accelerators caught in the act.

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Image of part of a stellar remnant whose explosion was recorded in 185 A.D. By studying this remnant in detail, a team of astronomers was able to solve the mystery of the Milky Way’s super-efficient particle accelerators. The team shows that the shock wave visible in this area is very efficient at accelerating particles and the energy used in this process matches the number of cosmic rays observed on Earth. North is toward the top right and east to the top left. The image is about six arc minutes across. Credit: ESO/E. Helder & NASA/Chandra.

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Thanks to a unique "ballistic study" that combines data from ESO's Very Large Telescope and NASA's Chandra X-ray Observatory, astronomers have now solved a long-standing mystery of the Milky Way's particle accelerators. They show in a paper published today on Science Express that cosmic rays from our galaxy are very efficiently accelerated in the remnants of exploded stars.

During the Apollo flights astronauts reported seeing odd flashes of light, visible even with their eyes closed. We have since learnt that the cause was cosmic rays — extremely energetic particles from outside the Solar System arriving at the Earth, and constantly bombarding its atmosphere. Once they reach Earth, they still have sufficient energy to cause glitches in electronic components.
Galactic cosmic rays come from sources inside our home galaxy, the Milky Way, and consist mostly of protons moving at close to the speed of light, the "ultimate speed limit" in the Universe. These protons have been accelerated to energies exceeding by far the energies that even CERN's Large Hadron Collider will be able to achieve.
"It has long been thought that the super-accelerators that produce these cosmic rays in the Milky Way are the expanding envelopes created by exploded stars, but our observations reveal the smoking gun that proves it", says Eveline Helder from the Astronomical Institute Utrecht of Utrecht University in the Netherlands, the first author of the new study.
"You could even say that we have now confirmed the calibre of the gun used to accelerate cosmic rays to their tremendous energies", adds collaborator Jacco Vink, also from the Astronomical Institute Utrecht.
For the first time Helder, Vink and colleagues have come up with a measurement that solves the long-standing astronomical quandary of whether or not stellar explosions produce enough accelerated particles to explain the number of cosmic rays that hit the Earth's atmosphere. The team's study indicates that they indeed do and directly tells us how much energy is removed from the shocked gas in the stellar explosion and used to accelerate particles.
"When a star explodes in what we call a supernova a large part of the explosion energy is used for accelerating some particles up to extremely high energies", says Helder. "The energy that is used for particle acceleration is at the expense of heating the gas, which is therefore much colder than theory predicts".

The researchers looked at the remnant of a star that exploded in AD 185, as recorded by Chinese astronomers. The remnant, called RCW 86, is located about 8200 light-years away towards the constellation of Circinus (the Drawing Compass). It is probably the oldest record of the explosion of a star.
Using ESO's Very Large Telescope, the team measured the temperature of the gas right behind the shock wave created by the stellar explosion. They measured the speed of the shock wave as well, using images taken with NASA's X-ray Observatory Chandra three years apart. They found it to be moving at between 10 and 30 million km/h, between 1 and 3 percent the speed of light.
The temperature of the gas turned out to be 30 million degrees Celsius. This is quite hot compared to everyday standards, but much lower than expected, given the measured shock wave's velocity. This should have heated the gas up to at least half a billion degrees.
"The missing energy is what drives the cosmic rays", concludes Vink.
More information: This research was presented in a paper to appear in Science: Measuring the cosmic ray acceleration efficiency of a supernova remnant, by E. A. Helder et al.
Source: ESO (news : web)

Mars Mission Could Ease Earth’s Energy Supply Crisis

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ScienceDaily (June 22, 2009) — Techniques and instrumentation initially developed for ExoMars -- Europe’s next robotic mission to Mars in 2016, but now due to fly on a NASA mission in 2018 -- could also provide the answers to the globally pressing issue of energy supply.

A major study by the Imperial College London, funded by the Science and Technology Facilities Council (STFC), aims to use this new technology as an inexpensive and efficient way to help process unconventional energy resources, potentially having an enormous impact on the UK and global economy.
Professor Mark Sephton from Imperial’s Department of Earth Science and Engineering, said: “The research involves using extraction-helping materials, called surfactants, to liberate organic matter from rock in space to gain a deeper understanding into the biological environment on Mars. We aim to show that the same technique could also be used to recycle the prodigious amounts of water necessary to process tar sand deposits and turn them into conventional petroleum.”
Usable energy resources are essential to the global economy. Conventional crude oil is a staple energy resource and accounts for over 35% of the world’s energy consumption. As the demand for oil exceeds supply, focus has now turned to trying to tap unconventional fossil fuels, such as tar sands. However, these unconventional fossil fuels must be extracted and upgraded to match the characteristics of more conventional oil deposits and make them commercially viable. The extraction process requires substantial amounts of water which is then left contaminated for extended periods of time. In just hours, the new technology can strip this water of its oily contaminants, removing a bottleneck in the refining process.
“Our new technology is an inexpensive approach that can be used to reduce the water demand during treatment of this type of unconventional hydrocarbon deposit,” said Professor Sephton. “Moreover, these extraction helping materials are environmentally harmless to the extent that they are edible. Our research at Imperial College combines first rate scientific investigation with practical engineering design.”
Dr Liz Towns-Andrews, Director of Knowledge Exchange at STFC, which is funding the study through its Knowledge Exchange Follow on Fund award scheme, added, “This is a truly valuable study which will not only reveal more about our neighbour Mars, but could also deliver enormous benefits here on Earth. The new research is a direct solution to our worsening energy supply crisis and is a great example of the seamless interaction of pure and applied science with engineering to solve real world environmental and commercial issues. Professor Sephton’s work is well aligned with the current needs of industry and we believe that this ambitious project could be of great benefit to the UK economy.”
Adapted from materials provided by Science and Technology Facilities Council.

Scientists Bring 'Light' To Moon's Permanently Dark Craters

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ScienceDaily (June 22, 2009) — A new lunar topography map with the highest resolution of the moon's rugged south polar region provides new information on some of our natural satellite's darkest inhabitants - permanently shadowed craters.

The map was created by scientists at NASA's Jet Propulsion Laboratory, Pasadena, Calif., who collected the data using the Deep Space Network's Goldstone Solar System Radar located in California's Mojave Desert. The map will help Lunar Crater Observation and Sensing Satellite (LCROSS) mission planners as they target for an encounter with a permanently dark crater near the lunar South Pole.
"Since the beginning of time, these lunar craters have been invisible to humanity," said Barbara Wilson, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and manager of the study. "Now we can see detailed topography inside these craters down to 40 meters [132 feet] per pixel, with height accuracy of better than 5 meters [16 feet]."
The terrain map of the moon's south pole is online at: http://www.nasa.gov/topics/moonmars/features/moon-20090618.html .
Scientists targeted the moon's south polar region using Goldstone's 70-meter (230-foot) radar dish. The antenna, three-quarters the size of a football field, sent a 500-kilowatt-strong, 90-minute-long radar stream 373,046 kilometers (231,800 miles) to the moon. Signals were reflected back from the rough-hewn lunar terrain and detected by two of Goldstone's 34-meter (112-foot) antennas on Earth. The roundtrip time, from the antenna to the moon and back, was about two-and-a-half seconds.
The scientists compared their data with laser altimeter data recently released by the Japanese Aerospace Exploration Agency's Kaguya mission to position and orient the radar images and maps. The new map provides contiguous topographic detail over a region approximately 500 kilometers (311 miles) by 400 kilometers (249 miles).
Funding for the program was provided by NASA's Exploration Systems Mission Directorate. JPL manages the Goldstone Solar System Radar and the Deep Space Network for NASA. JPL is managed for NASA by the California Institute of Technology in Pasadena.
More information about the Goldstone Solar System Radar and Deep Space Network is at http://deepspace.jpl.nasa.gov/dsn . More information about NASA's exploration program to return humans to the moon is at http://www.nasa.gov/exploration .
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Definitive Evidence For Ancient Lake On Mars

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ScienceDaily (June 18, 2009) — A University of Colorado at Boulder research team has discovered the first definitive evidence of shorelines on Mars, an indication of a deep, ancient lake there and a finding with implications for the discovery of past life on the Red Planet.

Estimated to be more than 3 billion years old, the lake appears to have covered as much as 80 square miles and was up to 1,500 feet deep -- roughly the equivalent of Lake Champlain bordering the United States and Canada, said CU-Boulder Research Associate Gaetano Di Achille, who led the study. The shoreline evidence, found along a broad delta, included a series of alternating ridges and troughs thought to be surviving remnants of beach deposits.
"This is the first unambiguous evidence of shorelines on the surface of Mars," said Di Achille. "The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago."
A paper on the subject by Di Achille, CU-Boulder Assistant Professor Brian Hynek and CU-Boulder Research Associate Mindi Searls, all of the Laboratory for Atmospheric and Space Physics, has been published online in Geophysical Research Letters, a publication of the American Geophysical Union.
Images used for the study were taken by a high-powered camera known as the High Resolution Imaging Science Experiment, or HiRISE. Riding on NASA's Mars Reconnaissance Orbiter, HiRISE can resolve features on the surface down to one meter in size from its orbit 200 miles above Mars.
An analysis of the HiRISE images indicate that water carved a 30-mile-long canyon that opened up into a valley, depositing sediment that formed a large delta. This delta and others surrounding the basin imply the existence of a large, long-lived lake, said Hynek, also an assistant professor in CU-Boulder's geological sciences department. The lake bed is located within a much larger valley known as the Shalbatana Vallis.
"Finding shorelines is a Holy Grail of sorts to us," said Hynek.
In addition, the evidence shows the lake existed during a time when Mars is generally believed to have been cold and dry, which is at odds with current theories proposed by many planetary scientists, he said. "Not only does this research prove there was a long-lived lake system on Mars, but we can see that the lake formed after the warm, wet period is thought to have dissipated."
Planetary scientists think the oldest surfaces on Mars formed during the wet and warm Noachan epoch from about 4.1 billion to 3.7 billion years ago that featured a bombardment of large meteors and extensive flooding. The newly discovered lake is believed to have formed during the Hesperian epoch and postdates the end of the warm and wet period on Mars by 300 million years, according to the study.
The deltas adjacent to the lake are of high interest to planetary scientists because deltas on Earth rapidly bury organic carbon and other biomarkers of life, according to Hynek. Most astrobiologists believe any present indications of life on Mars will be discovered in the form of subterranean microorganisms.
But in the past, lakes on Mars would have provided cozy surface habitats rich in nutrients for such microbes, Hynek said.
The retreat of the lake apparently was rapid enough to prevent the formation of additional, lower shorelines, said Di Achille. The lake probably either evaporated or froze over with the ice slowly turning to water vapor and disappearing during a period of abrupt climate change, according to the study.
Di Achille said the newly discovered pristine lake bed and delta deposits would be would be a prime target for a future landing mission to Mars in search of evidence of past life.
"On Earth, deltas and lakes are excellent collectors and preservers of signs of past life," said Di Achille. "If life ever arose on Mars, deltas may be the key to unlocking Mars' biological past."
Adapted from materials provided by University of Colorado at Boulder.

Rare Radio Supernova In Nearby Galaxy Is Nearest Supernova In Five Years

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ScienceDaily (June 11, 2009) — The chance discovery last month of a rare radio supernova -- an exploding star seen only at radio wavelengths and undetected by optical or X-ray telescopes -- underscores the promise of new, more sensitive radio surveys to find supernovas hidden by gas and dust.

"This supernova is the nearest supernova in five years, yet is completely obscured in optical, ultraviolet and X-rays due to the dense medium of the galaxy," said Geoffrey Bower, assistant professor of astronomy at the University of California, Berkeley, and coauthor of a paper describing the discovery in the June issue of the journal Astronomy & Astrophysics. "This just popped out; in the future, we want to go from discovery of radio supernovas by accident to specifically looking for them."
Sky surveys like the one just launched by the Allen Telescope Array, which will look for bright but short-lived radio bursts from supernovas, will provide better estimates of the rate of star formation in nearby galaxies, Bower said. Radio emissions from supernovas also can help astronomers understand how stars explode and what happens before their cores collapse, since radio emissions are caused when debris from the explosion collides with the stellar wind previously shed by the stars.
Bower's colleagues are Andreas Bunthaler, Karl M. Menten and Christian Henkel of the Max Planck Institute for Radioastronomy in Bonn, Germany; Mark J. Reid of Harvard University's Center for Astrophysics; and Heino Falcke of the University of Nijmegen in the Netherlands.
The radio supernova was discovered on April 8 in M82, a small irregular galaxy located nearly 12 million light years from Earth in the M81 galaxy group, by the Very Large Array, a New Mexico facility operated by the National Radio Astronomy Observatory (NRAO). It was subsequently confirmed by NRAO's Very Long Baseline Array (VLBA), a 10-telescope array whose baseline stretches from Hawaii to the Virgin Islands, providing the sharpest vision of any telescope on Earth.
The Allen Telescope Array, comprising 42 of a planned 350 radio dishes and supported by UC Berkeley and the SETI Institute of Mountain View, Calif., last week began a major survey of the radio sky that should turn up many more such radio supernovas, Bower said. While the VLA and VLBA have very narrow fields of view unsuited to all-sky surveys, the ATA's wide-angle view is ideal for scanning the full sky once a day, which is necessary to find sources that brighten and dim over several days.
"The ATA can detect objects at least 10 times fainter than this radio supernova, which pushes our survey an order of magnitude deeper than other radio surveys with more attention to transient and variable sources. Radio supernovas are a really strong aspect of that survey," he said. "This ( new radio supernova) is the kind of discovery that we would like to make with the Allen Telescope Array."
The ATA will compile an updated catalog of radio sources much as the Sloan Digital Sky Survey updated the older Palomar Observatory Sky Survey of visible and infrared objects. At the same time, it will look for radio signals indicative of intelligent life around other stars.
Not all supernovas produce radio emissions, Bower said. If the star has not sloughed off much of its envelope before collapsing inward to form a neutron star or black hole – a classic Type II supernova – then few radio emissions are produced from gas collisions.
On the other hand, supernovas in very active star-forming regions, like the center of M82, should produce copious radio emissions because of the density of gas and dust in the interstellar medium. That same gas and dust blocks optical, ultraviolet and X-rays, however, making radio surveys one of the few options to find and observe such supernovas.
Bower and his colleagues were studying the motion of M82 with the VLBA, which links the VLA and nine other radio telescopes into a very high resolution instrument, when they noticed a very bright radio source – five times brighter than anything else in the galaxy – in the VLA data. The team looked at earlier observations and found the same source, but almost twice as bright, in data taken May 3, 2008. Data from March 24, 2008, showed an even brighter source – 10 times brighter than in April 2009 – while Oct. 29, 2007, data showed no bright radio source.
Extrapolating backward in time, the research team estimates that the star exploded sometime in January 2008, apparently near the very center of the galaxy. The team rejected alternative explanations for the dimming radio source, such as a flare created by a star falling into a supermassive black hole.
The newly discovered supernova is thus the brightest in radio wavelengths in the past 20 years, Bower said, and is one of only a few dozen radio supernovas observed to date.
The team also looked at the complete data from the VLBA and detected a ring structure indicative of a shock wave plunging through the interstellar medium, bolstering its conclusion that it is a supernova. The ring is about 2,000 astronomical units across, consistent with a year-old supernova. (An astronomical unit 93 million miles, the average distance between Earth and the sun.)
The research was funded through National Science Foundation support of NRAO.
Adapted from materials provided by University of California - Berkeley. Original article written by Robert Sanders.

Baby Stars Finally Found In Jumbled Galactic Center

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ScienceDaily (June 12, 2009) — Astronomers have at last uncovered newborn stars at the frenzied center of our Milky Way galaxy. The discovery was made using the infrared vision of NASA's Spitzer Space Telescope.

The heart of our spiral galaxy is cluttered with stars, dust and gas, and at its very center, a supermassive black hole. Conditions there are harsh, with fierce stellar winds, powerful shock waves and other factors that make it difficult for stars to form. Astronomers have known that stars can form in this chaotic place, but they're baffled as to how this occurs. Confounding the problem is all the dust standing between us and the center of our galaxy. Until now, nobody had been able to definitively locate any baby stars.
"These stars are like needles in a haystack," said Solange Ramirez, the principal investigator of the research program at NASA's Exoplanet Science Institute at the California Institute of Technology, Pasadena. "There's no way to find them using optical light, because dust gets in the way. We needed Spitzer's infrared instruments to cut through the dust and narrow in on the objects."
The team plans to look for additional baby stars in the future, and ultimately to piece together what types of conditions allow stars to form in such an inhospitable environment as our galaxy's core.
"By studying individual stars in the galactic center, we can better understand how stars are formed in different interstellar environments," said Deokkeun An of the Infrared Processing and Analysis Center at Caltech, lead author of a paper submitted for publication in the Astrophysical Journal. "The Milky Way galaxy is just one of more than hundreds of billions of galaxies in the visible universe. However, our galaxy is so special because we can take a closer look at its individual stellar components." An started working on this program while a graduate student at Ohio State University, Columbus, under the leadership of Ohio State astronomer Kris Sellgren, the co-investigator on the project.
The core of the Milky Way is a mysterious place about 600 light-years across (light would take 600 years to travel from one end to the other). While this is just a fraction of the size of the entire Milky Way, which is about 100,000 light-years across, the core is stuffed with 10 percent of all the gas in the galaxy -- and loads and loads of stars.
Before now, there were only a few clues that stars can form in the galaxy's core. Astronomers had found clusters of massive adolescent stars, in addition to clouds of charged gas -- a sign that new stars are beginning to ignite and ionize surrounding gas. Past attempts had been unsuccessful in finding newborn stars, or as astronomers call them, young stellar objects.
Ramirez and colleagues began their search by scanning large Spitzer mosaics of our galactic center. They narrowed in on more than 100 candidates, but needed more detailed data to confirm the stars' identities. Young stellar objects, when viewed from far away, can look a lot like much older stars. Both types of stars are very dusty, and the dust lying between us and them obscures the view even further.
To sort through the confusion, the astronomers looked at their candidate stars with Spitzer's spectrograph – an instrument that breaks light apart to reveal its rainbow-like array of infrared colors. Molecules around stars leave imprints in their light, which the spectrograph can detect.
The results revealed three stars with clear signs of youth, for example, certain warm, dense gases. These youthful features are found in other places in the galaxy where stars are being formed.
"It is amazing to me that we have found these stars," said Ramirez. "The galactic center is a very interesting place. It has young stars, old stars, black holes, everything. We started mining a catalog of about 1 million sources and managed to find three young stars -- stars that will help reveal the secrets at the core of the Milky Way."
The young stellar objects are all less than about 1 million years old. They are embedded in cocoons of gas and dust, which will eventually flatten to disks that, according to theory, later lump together to form planets.
Other collaborators include Richard Arendt of NASA's Goddard Space Flight Center, Greenbelt, Md.; A. C. Adwin Boogert of NASA's Herschel Science Center, Caltech in Pasadena; Mathias Schultheis of the Besancon Observatory in France; Susan Stolovy of NASA's Spitzer Science Center, Caltech in Pasadena; Angela Cotera of SETI Institute, Mountain View, Calif.; and Thomas Robitaille and Howard Smith of Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Ultracool Stars Take 'Wild Rides' Around, Outside The Milky Way

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ScienceDaily (June 11, 2009) — Astronomers have found that stars of a recently discovered type, dubbed ultracool subdwarfs, take some pretty wild rides as they orbit around the Milky Way, following paths that are very different from those of typical stars. One of them may actually be a visitor that originated in another galaxy.

Adam Burgasser and John Bochanski of MIT presented the findings on June 9 at the American Astronomical Society's semi-annual meeting in Pasadena, Calif. The result clarifies the origins of these peculiar, faint stars, and may provide new details on the types of stars the Milky Way has acquired from other galaxies.
Ultracool subdwarfs were first recognized as a unique class of stars in 2003, and are distinguished by their low temperatures ("ultracool") and low concentrations of elements other than hydrogen and helium ("subdwarf"). They sit at the bottom end of the size range for stars, and some are so small that they are closer to the planet-like objects called brown dwarfs. Only a few dozen ultracool subdwarfs are known today, as they are both very faint — up to 10,000 times fainter than the Sun — and extremely rare.
Burgasser, associate professor of physics at MIT and lead author of the study, was intrigued by the fast motions of ultracool subdwarfs, which zip past the Sun at astonishing speeds. "Most nearby stars travel more or less in tandem with the Sun tracing circular orbits around the center of the Milky Way once every 250 million years," he explains. The ultracool subdwarfs, on the other hand, appear to pass us by at very high speeds, up to 500 km/s, or over a million miles per hour.
"If there are interstellar cops out there, these stars would surely lose their driver's licenses," says Burgasser.
Burgasser's team of astronomers assembled measurements of the positions, distances and motions of roughly two dozen of these rare stars. Robyn Sanderson, co-author and MIT graduate student, then used these measurements to calculate the orbits of the subdwarfs using a numerical code developed to study galaxy collisions. Despite doing similar calculations for other types of low-mass stars, "these orbits were like nothing I'd ever seen before," says Sanderson.
Sanderson's calculations showed an unexpected diversity in the ultracool subdwarf orbits. Some plunge deep into the center of the Milky Way on eccentric, comet‐like tracks; others make slow, swooping loops far beyond the Sun's orbit. Unlike the majority of nearby stars, most of the ultracool subdwarfs spend a great deal of time thousands of light‐years above or below the disk of the Milky Way.
"Someone living on a planet around one of these subdwarfs would have an incredible nighttime view of a beautiful spiral galaxy — our Milky Way — spread across the sky," Burgasser speculates.
Sanderson's orbit calculations confirm that all of the ultracool subdwarfs are part of the Milky Way's halo, a widely dispersed population of stars that likely formed in the Milky Way's distant past. However, one of the subdwarfs, a star named 2MASS 1227‐0447 in the constellation Virgo, has an orbit indicating that it might have a very different lineage, possibly extragalactic.
"Our calculations show that this subdwarf travels up to 200,000 light years away from the center of the Galaxy, almost 10 times farther than the Sun," says Bochanski, a postdoctoral researcher in Burgasser's group at MIT. This is farther than many of the Milky Way's nearest galactic neighbors, suggesting that this particular subdwarf may have originated somewhere else.
"Based on the size of its one billion‐year orbit and direction of motion, we speculate that 2MASS 1227‐0447 might have come from another, smaller galaxy that at some point got too close to the Milky Way and was ripped apart by gravitational forces," explains Bochanksi.
Astronomers have previously identified streams of stars in the Milky Way originating from neighboring galaxies, but all have been distant, massive, red giant stars. The ultracool subdwarf identified by Burgasser and his team is the first nearby, low‐mass star to be found on such a trajectory. "If we can identify what stream this star is associated with, or which dwarf galaxy it came from, we could learn more about the types of stars that have built up the Milky Way's halo over the past 10 billion years," says Burgasser.
The results presented at the meeting are based in part on two studies recently published in the Astrophysical Journal by Burgasser and coauthor Michael Cushing, a postdoctoral researcher at the University of Hawaii's Institute for Astronomy.
Other authors of this paper are Andrew West of MIT; Dagny Looper of the University of Hawaii, Manoa; and Jacqueline Faherty of the American Museum of Natural History, New York, NY.
Adapted from materials provided by Massachusetts Institute of Technology.

The Day The Universe Froze: New Model For Dark Energy

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ScienceDaily (May 11, 2009) — Imagine a time when the entire universe froze. According to a new model for dark energy, that is essentially what happened about 11.5 billion years ago, when the universe was a quarter of the size it is today.

The model, published online May 6 in the journal Physical Review D, was developed by Research Associate Sourish Dutta and Professor of Physics Robert Scherrer at Vanderbilt University, working with Professor of Physics Stephen Hsu and graduate student David Reeb at the University of Oregon.
A cosmological phase transition — similar to freezing — is one of the distinctive aspects of this latest effort to account for dark energy — the mysterious negative force that cosmologists now think makes up more than 70 percent of all the energy and matter in the universe and is pushing the universe apart at an ever-faster rate.
Another feature that distinguishes the new formulation is that it makes a testable prediction regarding the expansion rate of the universe. In addition, the micro-explosions created by the largest particle colliders should excite the dark energy field and these excitations could appear as exotic, never-seen-before sub-atomic particles.
"One of the things that is very unsatisfying about many of the existing explanations for dark energy is that they are difficult to test,” says Scherrer, "We designed a model that can interact with normal matter and so has observable consequences.”
The model associates dark energy with something called vacuum energy. Like a number of existing theories, it proposes that space itself is the source of the repulsive energy that is pushing the universe apart. For many years, scientists thought that the energy of empty space averaged zero. But the discovery of quantum mechanics changed this view. According to quantum theory, empty space is filled with pairs of "virtual” particles that spontaneously pop into and out of existence too quickly to be detected.
This sub-atomic activity is a logical source for dark energy because both are spread uniformly throughout space. This distribution is consistent with evidence that the average density of dark energy has remained constant as the universe has expanded. This characteristic is in direct contrast to ordinary matter and energy, which become increasingly dilute as the universe inflates.
The theory is one of those that attribute dark energy to an entirely new field dubbed quintessence. Quintessence is comparable to other basic fields like gravity and electromagnetism, but has some unique properties. For one thing, it is the same strength throughout the universe. Another important feature is that it acts like an antigravity agent, causing objects to move away from each other instead of pulling them together like gravity.
In its simplest form, the strength of the quintessence field remains constant through time. In this case it plays the role of the cosmological constant, a term that Albert Einstein added to the theory of general relativity to keep the universe from contracting under the force of gravity. When evidence that the universe is expanding came in, Einstein dropped the term since an expanding universe is a solution to the equations of general relativity. Then, in the late 90's, studies of supernovae (spectacular stellar explosions so powerful that they can briefly outshine entire galaxies consisting of millions of stars) indicated that the universe is not just expanding but also that the rate of expansion is speeding up instead of slowing down as scientists had expected.
That threw cosmologists for a loop since they thought gravity was the only long-range force acting between astronomical objects. So they had no idea what could possibly be pushing everything apart. The simplest way to account for this bizarre phenomenon was to bring back Einstein's cosmological constant with its antigravity properties. Unfortunately, this explanation suffers from some severe drawbacks so physicists have been actively searching for other antigravity agents.
These antigravity agents (dubbed "dark energy models” in the technical literature) usually invoke quintessence or even more exotic fields. Because none of these fields have been detected in nature; however, their proponents generally assume that they do not interact significantly with ordinary matter and radiation.
One of the consequences of allowing quintessence to interact with ordinary matter is the likelihood that the field went through a phase transition — froze out — when the universe cooled down to a temperature that it reached 2.2 billion years after the Big Bang. As a result, the energy density of the quintessence field would have remained at a relatively high level until the phase transition when it abruptly dropped to a significantly lower level where it has remained ever since.
This transition would have released a fraction of the dark energy held in the field in the form of dark radiation. According to the model, this dark radiation is much different than light, radio waves, microwaves and other types of ordinary radiation: It is completely undetectable by any instrument known to man. However, nature provides a detection method. According to Einstein's theory of general relativity, gravity is produced by the distribution of energy and momentum. So the changes in net energy and momentum caused by the sudden introduction of dark radiation should have affected the gravitational field of the universe in a way that has slowed its expansion in a characteristic fashion.
In the next 10 years or so, the large astronomical surveys that are just starting up to plot the expansion of the universe by measuring the brightness of the most distant supernovas should be able to detect the slowdown in the expansion rate that the model predicts. At the same time, new particle accelerators, like the Large Hadron Collider nearing operation in Switzerland, can produce energies theoretically large enough to excite the quintessence field and these excitations could appear as new exotic particles, the researchers say.
The research was funded by grants from the U.S. Department of Energy.
Journal reference:
Sourish Dutta, Emmanuel N. Saridakis, and Robert J. Scherrer. Dark energy from a quintessence (phantom) field rolling near a potential minimum (maximum). Physical Review D, 2009; 79 (10): 103005 DOI: 10.1103/PhysRevD.79.103005
Adapted from materials provided by Vanderbilt University. Original article written by David F. Salisbury.

Missing Black Hole Report: Hundreds Found!

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http://www.sciencedaily.com/releases/2007/10/071025150029.htm

ScienceDaily (Oct. 25, 2007) — Astronomers have unmasked hundreds of black holes hiding deep inside dusty galaxies billions of light-years away.

The massive, growing black holes, discovered by NASA's Spitzer and Chandra space telescopes, represent a large fraction of a long-sought missing population. Their discovery implies there were hundreds of millions of additional black holes growing in our young universe, more than doubling the total amount known at that distance.
"Active, supermassive black holes were everywhere in the early universe," said Mark Dickinson of the National Optical Astronomy Observatory in Tucson, Ariz. "We had seen the tip of the iceberg before in our search for these objects. Now, we can see the iceberg itself." Dickinson is a co-author of two new papers appearing in the Nov. 10 issue of the Astrophysical Journal. Emanuele Daddi of the Commissariat a l'Energie Atomique in France led the research.
The findings are also the first direct evidence that most, if not all, massive galaxies in the distant universe spent their youths building monstrous black holes at their cores.
For decades, a large population of active black holes has been considered missing. These highly energetic structures belong to a class of black holes called quasars. A quasar consists of a doughnut-shaped cloud of gas and dust that surrounds and feeds a budding supermassive black hole. As the gas and dust are devoured by the black hole, they heat up and shoot out X-rays. Those X-rays can be detected as a general glow in space, but often the quasars themselves can't be seen directly because dust and gas blocks them from our view.
"We knew from other studies from about 30 years ago that there must be more quasars in the universe, but we didn't know where to find them until now," said Daddi.
Daddi and his team initially set out to study 1,000 dusty, massive galaxies that are busy making stars and were thought to lack quasars. The galaxies are about the same mass as our own spiral Milky Way galaxy, but irregular in shape. At 9 to 11 billion light-years away, they existed at a time when the universe was in its adolescence, between 2.5 and 4.5 billion years old.
When the astronomers peered more closely at the galaxies with Spitzer's infrared eyes, they noticed that about 200 of the galaxies gave off an unusual amount of infrared light. X-ray data from Chandra, and a technique called "stacking," revealed the galaxies were, in fact, hiding plump quasars inside. The scientists now think that the quasars heat the dust in their surrounding doughnut clouds, releasing the excess infrared light.
"We found most of the population of hidden quasars in the early universe," said Daddi. Previously, only the rarest and most energetic of these hidden black holes had been seen at this early epoch.
The newfound quasars are helping answer fundamental questions about how massive galaxies evolve. For instance, astronomers have learned that most massive galaxies steadily build up their stars and black holes simultaneously until they get too big and their black holes suppress star formation.
The observations also suggest that collisions between galaxies might not play as large a role in galaxy evolution as previously believed. "Theorists thought that mergers between galaxies were required to initiate this quasar activity, but we now see that quasars can be active in unharassed galaxies," said co-author David Alexander of Durham University, United Kingdom.
"It's as if we were blindfolded studying the elephant before, and we weren't sure what kind of animal we had," added co-author David Elbaz of the Commissariat a l'Energie Atomique. "Now, we can see the elephant for the first time."
The new observations were made as part of the Great Observatories Origins Deep Survey, the most sensitive survey to date of the distant universe at multiple wavelengths.
Consistent results were recently obtained by Fabrizio Fiore of the Osservatorio Astronomico di Roma, Italy, and his team. Their results will appear in the Jan. 1, 2008, issue of Astrophysical Journal.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Fausto Intilla

www.oloscience.com

Boosting The Accuracy Of Rosetta's Earth Approach

Source:

http://www.sciencedaily.com/releases/2007/10/071019102623.htm

ScienceDaily (Oct. 22, 2007) — On October 18 at 18:06 CEST, the thrusters of ESA’s comet chaser, Rosetta, were fired in a planned, 42-second trajectory correction manoeuvre designed to 'fine tune' the spacecraft's approach to Earth. Rosetta is now approaching Earth for its second planetary swing-by of 2007.

The process took place automatically since the on-board antenna was pointed away from the ground station during the slew and could not receive radio commands; signals from Rosetta were reacquired at ESA's New Norcia deep-space ground station at 20:39 CEST (18:39 UTC).
The burn took place during one of five preplanned slots which are available to mission controllers based on determination of the spacecraft's actual trajectory by flight dynamics and other experts working on the Mission Control Team at ESA's European Space Operations Centre (ESOC), Darmstadt, Germany.
Optimising orbits and saving fuel
"We have a target trajectory for Earth swing-by and regular orbit determinations allow us to decide when to do a correction manoeuvre. Brief burns now allow us to optimise the orbit and make the swing-by more accurate, saving us a lot of precious fuel later on," said Andrea Accomazzo, Rosetta Spacecraft Operations Manager at ESOC. He confirmed that yesterday's manoeuvre results were as expected.
A second trajectory correction slot, on 1 November, may also be used depending on results of an orbit determination scheduled for 30 October.
The third Earth swing-by - and last of the four - will take place in November 2009.
Significant science: On to Steins
After November's Earth encounter, Rosetta will continue on its journey and next pass Asteroid Steins, providing an excellent opportunity for science investigations. Steins is relatively small, with a diameter of a few kilometres, and Rosetta is predicted to pass by on 5 September 2008 at a distance of just over 1700 km. This encounter will take place at a relatively low speed of about 9 km/sec during Rosetta's first excursion into the asteroid belt.
ESA's Comet Chaser
Rosetta will be ESA's first spacecraft to undertake long-term exploration of a comet at close quarters. The mission consists of a large orbiter, designed to operate for a decade at large distances from the Sun, and a small lander, Philae.
Each of these carries a large suite of scientific experiments designed to complete the most detailed study of a comet ever attempted.
After entering orbit around Comet 67P/Churyumov-Gerasimenko in 2014, the spacecraft will release the lander onto the icy nucleus.
It will then spend the next two years orbiting the comet as it heads toward the Sun. On the way to Comet Churyumov-Gerasimenko, Rosetta has received gravity assists from Earth and Mars, and will fly past two main-belt asteroids – Steins (September 2008) and Lutetia (July 2010).

Adapted from materials provided by European Space Agency.

Fausto Intilla

www.oloscience.com

Heaviest Stellar Black Hole Discovered In Nearby Galaxy

Source:

http://www.sciencedaily.com/releases/2007/10/071017145225.htm

Science Daily — Astronomers have located an exceptionally massive black hole in orbit around a huge companion star. This result has intriguing implications for the evolution and ultimate fate of massive stars.

The black hole is part of a binary system in M33, a nearby galaxy about 3 million light years from Earth. By combining data from NASA's Chandra X-ray Observatory and the Gemini telescope on Mauna Kea, Hawaii, the mass of the black hole, known as M33 X-7, was determined to be 15.7 times that of the Sun. This makes M33 X-7 the most massive stellar black hole known. A stellar black hole is formed from the collapse of the core of a massive star at the end of its life.
"This discovery raises all sorts of questions about how such a big black hole could have been formed," said Jerome Orosz of San Diego State University, lead author of the paper appearing in the October 18th issue of the journal Nature.
M33 X-7 orbits a companion star that eclipses the black hole every three and a half days. The companion star also has an unusually large mass, 70 times that of the Sun. This makes it the most massive companion star in a binary system containing a black hole.
"This is a huge star that is partnered with a huge black hole," said coauthor Jeffrey McClintock of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Eventually, the companion will also go supernova and then we'll have a pair of black holes."
The properties of the M33 X-7 binary system - a massive black hole in a close orbit around a massive companion star - are difficult to explain using conventional models for the evolution of massive stars. The parent star for the black hole must have had a mass greater than the existing companion in order to have formed a black hole before the companion star.
Such a massive star would have had a radius larger than the present separation between the stars, so the stars must have been brought closer while sharing a common outer atmosphere. This process typically results in a large amount of mass being lost from the system, so much that the parent star should not have been able to form a 15.7 solar-mass black hole.
The black hole's progenitor must have shed gas at a rate about 10 times less than predicted by models before it exploded. If even more massive stars also lose very little material, it could explain the incredibly luminous supernova seen recently as SN 2006gy. The progenitor for SN 2006gy is thought to have been about 150 times the mass of the Sun when it exploded.
"Massive stars can be much less extravagant than people think by hanging onto a lot more of their mass toward the end of their lives," said Orosz. "This can have a big effect on the black holes that these stellar time-bombs make."
Coauthor Wolfgang Pietsch was also the lead author of an article in the Astrophysical Journal that used Chandra observations to report that M33 X-7 is the first black hole in a binary system observed to undergo eclipses. The eclipsing nature enables unusually accurate estimates for the mass of the black hole and its companion.
"Because it's eclipsing and because it has such extreme properties, this black hole is an incredible test-bed for studying astrophysics," said Pietsch.
The length of the eclipse seen by Chandra gives information about the size of the companion. The scale of the companion's motion, as inferred from the Gemini observations, gives information about the mass of the black hole and its companion. Other observed properties of the binary were used to constrain the mass estimates.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Gemini is an international partnership managed by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation.
Note: This story has been adapted from material provided by Chandra X-ray Center.

Fausto Intilla

www.oloscience.com

Most Powerful Supernova Ever Discovered: 100 Billion Times Brighter Than The Sun

Source:

http://www.sciencedaily.com/releases/2007/10/071016085212.htm

Science Daily — Astronomer Robert Quimby has done it again. Found the most luminous supernova ever, that is.

Quimby discovered the current record holder, supernova 2006gy, last year as part of his Texas Supernova Search project. Now he announces that a supernova he discovered earlier in the project is actually twice as luminous. Using follow-up studies to pinpoint its distance, supernova 2005ap peaked at more than 100 billion times the brightness of the Sun.
This supernova is a Type II, Quimby said, because it contains hydrogen. Most Type II supernovae are thought to result when the cores of massive stars, those seven to eight times or more heavy than the Sun, collapse under their own weight and trigger an explosion. This particular Type II is 300 times brighter than average, Quimby said, and lies in a dwarf galaxy in the constellation Coma Berenices, well behind the famous Coma cluster of galaxies.
“It’s clearly not the same as 2006gy,” Quimby’s colleague and supernova expert J. Craig Wheeler of The University of Texas at Austin said. “It’s a puzzle.”
Quimby completed his Ph.D. under Wheeler’s supervision at Texas in May, and has just begun a post-doctoral appointment at Caltech. His Texas Supernova Search uses the 18-inch ROTSE-IIIb robotic telescope on McDonald Observatory’s Mount Fowlkes, a tiny neighbor to the giant 10-meter-class Hobby-Eberly Telescope (HET).
Quimby studied 2005ap with HET just a few days after its discovery. The results were intriguing, Quimby said. The supernova’s spectrum hinted at the presence of a highly shifted absorption line of oxygen III (an oxygen atom that has lost two of its electrons). Quimby knew that if the feature was oxygen III, then 2005ap was “possibly very far away and thus very luminous.”
Follow-up observations with the Keck Telescope in Hawaii by Quimby’s colleague Greg Aldering of Lawrence Berkeley National Lab not only confirmed Quimby’s HET detection of oxygen III, but added another, equally shifted element to the spectrum: magnesium.
Together, the studies confirmed 2005ap’s distance of 4.7 billion light-years. (In astronomical terms, this equates to a redshift of z = 0.2832.)
It was this distance measurement, combined with measurements of the supernova’s apparent brightness that allowed the calculation of its intrinsic brightness, or “luminosity,” and uncovered 2005ap as the most powerful supernova yet.
“Before 2006gy, I thought this should not be plausible,” Quimby said. “There I was finding my first supernovae — I was just happy to get anything. It turned out to be the most luminous supernova ever found.”
How is that Quimby has found the brightest supernova yet, twice in a row? “I’ve worked too damn hard for this to be luck,” he said.
Quimby explained, “I’m searching a huge volume of space, comparable to all previous nearby supernova surveys combined.” Also, Quimby will find supernovae that other studies ignore: he doesn’t filter out non-Type Ia supernovae, which is what many studies do that are searching for supernovae for cosmology studies, and he does search dwarf galaxies as well as galaxies with active black holes at their centers, which other studies avoid. Others also avoid supernovae near the cores of galaxies.
In fact, 2006gy was found in the core of a galaxy, and that galaxy has a weakly active central black hole, Wheeler said.
“There’s no question that [his results] have gotten everybody’s attention,” Wheeler said. The University of Michigan-run ROTSE collaboration, whose main mission is the search for gamma-ray bursts, has decided to expand the supernova search to its entire network. Its robotic telescopes in Australia, Turkey, and Namibia will soon join the unit at McDonald Observatory in this search. The Sloan Digital Sky Survey Supernova Search, for which the HET provides confirming spectra, is also reconsidering its search filters in response to these discoveries, Wheeler said.
The result has been accepted for publication in the October 20 edition of The Astrophysical Journal Letters.
The Hobby-Eberly Telescope is a joint project of The University of Texas at Austin, The Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München and Georg-August-Universität Göttingen.
Note: This story has been adapted from material provided by McDonald Observatory.

Fausto Intilla

www.oloscience.com

Astronomers Get Their Hands Dirty As They Lift The Veil On Galactic Dust

Source:

http://www.sciencedaily.com/releases/2007/10/071012105824.htm

Science Daily — There is more to a grain of dust than meets the eye, at least for astronomers as they attempt to probe deeper into distant galaxies. Until now dust has been a nuisance because it has obscured galaxies, and the stars within them, by absorbing the radiation they emit. But more recently dust has started to present opportunities because it emits radiation itself as a consequence of being heated up by nearby stars. Aided by new observing instruments and sophisticated computer software, this radiation enables astronomers to reconstruct what lies behind the dust. Furthermore the dust itself plays a vital role in star formation within galaxies.

The stage was set for dramatic advances in the study of galactic dust in a recent workshop funded by the European Science Foundation (ESF) 's Exploratory Workshop. The big breakthrough is the ability to detect the dust at much higher resolution from its infrared radiation, according to Simone Bianchi, co-convenor of the ESF workshop. "It has been possible to do this since the eighties, but the new instruments have a higher sensitivity," said Bianchi.
At the same time new computer models are making it possible to work out the structure of the galaxy lying behind the dust, even though it cannot be observed directly at any wavelength. The key here is that the dust is acting as a relay for radiation emitted by the stars behind it. The dust absorbs high energy radiation from the stars and then heats up as a result. It then re-emits in the infra red waveband, which can now be detected with sensitive new instruments.
Plans were made at the workshop to use the European Space Agency's new infrared space telescope called Herschel, which will be launched in 2008 and be capable of detecting infrared radiation emitted by distant galactic dust. "The new instruments will allow us to detect dust associated with less dense regions of the interstellar medium," said Bianchi.
Astronomers also hope to learn more about the role played by dust in star formation. As Bianchi pointed out, there is a well established connection between the dust and the gas from which stars are formed. But the detailed relationship is unknown, and will require knowledge about the dust itself, in particular its molecular structure and lifecycle.
The ESF workshop focused mainly on spiral galaxies, because these are heavily obscured by dust. Galaxies are split into three categories by their structure, spiral, elliptical, and irregular. There is less dust in elliptical galaxies, while irregular galaxies are more difficult to model because they lack any orderly structure. "Spiral galaxies can be modelled in a more direct way because of their relatively simple geometry," said Bianchi. "However, recent comparison with observations of dust emission has shown that models may need a higher degree of complexity. This can be achieved now with the advances in computational facilities."
The ESF workshop was well timed to help Europe exploit the full potential of the data that will be obtained from the new instruments. It has already brought together the relevant European groups specialising in spiral galaxies and modelling dust, providing the platform for major advances in the field.
The workshop, held in Ghent, Belgium in May 2007, brought together 29 researchers from 10 different countries. Each year, ESF supports approximately 50 Exploratory Workshops across all scientific domains. These small, interactive group sessions are aimed at opening up new directions in research to explore new fields with a potential impact on developments in science.
Note: This story has been adapted from material provided by European Science Foundation.

Fausto Intilla

www.oloscience.com

Dusty Winds Bursting Out Of Black Holes May Have Seeded Planets, Life

Source:

http://www.sciencedaily.com/releases/2007/10/071010125734.htm

Science Daily — The hit song that proclaimed, "All we are is dust in the wind," may have some cosmic truth to it. New findings from NASA's Spitzer Space Telescope suggest that space dust -- the same stuff that makes up living creatures and planets -- was manufactured in large quantities in the winds of black holes that populated our early universe.

The findings are a significant new clue in an unsolved mystery: where did all the dust in the young universe originate?
"We were surprised to find what appears to be freshly made dust entrained in the winds that blow away from supermassive black holes," said Ciska Markwick-Kemper of the University of Manchester, U.K. Markwick-Kemper is lead author of a new paper appearing in an upcoming issue of the Astrophysical Journal Letters. "This could explain where the dust came from that was needed to make the first generations of stars in the early universe."
Space dust is essential to the formation of planets, stars, galaxies and even life as we know it. The dust in our corner of the universe was piped out by dying stars that were once a lot like our sun. But, when the universe was less than a tenth of its present age of 13.7 billion years, sun-like stars hadn't been around long enough to die and make dust. So, what produced the precious substance back when the universe was just a toddler?
Theorists have long-postulated that short-lived, massive exploding stars, or supernovae, might be the source of this mysterious dust, while others have proposed that a type of energetic, growing supermassive black hole, called a quasar, could be a contributing factor. A quasar consists of a supermassive black hole surrounded by a dusty doughnut-shaped cloud that feeds it. Theoretically, dust could form in the outer portion of the winds that slowly blow away from this doughnut cloud.
"Quasars are like the Cookie Monster," said co-author Sarah Gallagher of the University of California at Los Angeles, who is currently a visiting astronomer at the University of Western Ontario, Canada. "They are messy eaters, and they can consume less matter than they spit out in the form of winds."
Nobody has found conclusive proof that either quasar winds or supernovae can create enough dust to explain what is observed in the early universe. Markwick-Kemper and her team decided to test the former theory and investigate a quasar, called PG2112+059, located in the center of a galaxy about 8 billion light-years way. Although this particular quasar is not located in the early universe, because it is closer, it is an easier target for addressing the question of whether quasars can make dust. The team used Spitzer's infrared spectrograph instrument to split apart infrared light from the quasar and look for signs of various minerals.
They found a mix of the ingredients that make up glass, sand, marble and even rubies and sapphires. While the mineral constituting glass was expected, the minerals for sand, marble and rubies were a surprise. Why? These minerals are not typically detected floating around galaxies, suggesting they could have been freshly formed in the winds rushing away from the quasar.
For instance, the ingredient that makes up sand, crystalline silicate, doesn't survive for long free-floating in space. Radiation from stars zaps the minerals back to an amorphous, glass-like state. The presence of crystalline silicate therefore suggests something -- possibly the quasars winds -- is churning out the newly made substance.
Markwick-Kemper and her team say the case of the missing dust is not firmly shut. They hope to study more quasars for further evidence of their dust-making abilities. Also, according to the astronomers, quasars may not be the only source of dust in the early universe. "Supernovae might have been more important for creating dust in some environments, while quasars were more important in others," said Markwick-Kemper. "For now, we are very excited to have identified the different species of dust in a quasar billions of light-years away."
Other authors of this paper include Dean Hines of the Space Science Institute, Boulder, Colo., and Jeroen Bouwman of the Max Planck Institute for Astronomy, Heidelberg, Germany. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA. Spitzer's infrared spectrograph was built by Cornell University, Ithaca, N.Y. Its development was led by Jim Houck of Cornell.
Note: This story has been adapted from material provided by NASA/Spitzer Space Telescope.

Fausto Intilla

www.oloscience.com

Multiwavelength Images Of Distant Universe Now Available On Google Sky

Source:

http://www.sciencedaily.com/releases/2007/10/071003130840.htm

Science Daily — A massive project to map a distant region of the Universe in multiple wavelengths--from x-rays through ultraviolet, visible, infrared, and radio waves--is currently releasing its data to both fellow scientists and the general public. It is the first data release from the AEGIS survey and the first release of multiwavelength data to take advantage of the capabilities of Google Sky, a new feature of Google Earth.

AEGIS--the All-wavelength Extended Groth Strip International Survey--combines the efforts of nearly 100 researchers from around the world observing the same small region of sky in all available wavelengths of the electromagnetic spectrum. The target area, called the Extended Groth Strip, covers an area the width of four full moons that is a hop, skip and jump from the end of the Big Dipper's handle. The AEGIS region has now been surveyed more intensively and with more telescopes than any other region of the sky.
"We are still sorting through this treasure trove to discover the many gems of information it contains," said Sandra Faber, University Professor and chair of astronomy and astrophysics at the University of California, Santa Cruz. Faber worked with Jeffrey Newman of the University of Pittsburgh, Shui Kwok of the W. M. Keck Observatory in Hawaii, UCSC graduate student Genevieve Graves, and many other members of the AEGIS team to coordinate the data release through Google Sky.
"We are looking back to a time when the universe was more than half its current age and when galaxies were forming most of their stars," says Professor Kirpal Nandra, from the Department of Physics and who is leading the project from Imperial College London. He added: "With the X-ray images we are looking at black holes, which are at the centre of galaxies, to try to work out how the growth of black holes is linked to the growth of the galaxy itself."
"It is clear that serving astronomical data through Google Sky is going to revolutionize the way astronomers communicate, both among themselves and with the public," Faber said. "AEGIS is proud and pleased to be the pathfinder dataset for Google Sky's new multiwavelength capabilities."
Color images from four different satellite telescopes, as well as numerous data catalogs, from x-ray to radio wavelengths, giving brightnesses and distances of tens of thousands of galaxies are now available. Google Earth's new Sky feature provides a fast and powerful access tool for astronomical data similar to what the popular Google Earth software has provided for terrestrial data.
"AEGIS images projected onto the celestial sphere show how it would look with infrared, ultraviolet, or x-ray eyes," Faber said. "Some galaxies look brighter at certain wavelengths than others, which carries important information about their composition and the processes occurring within them."
The rapid browsing abilities of Google Sky provide a new way to compare many views of a single galaxy or a set of galaxies instantly. For researchers, it is a powerful tool for exploring AEGIS's massive data sets. The AEGIS collaboration is also making all of its data available on its website, so that researchers can download it directly.
Of the four color images in the first AEGIS data release, the most detailed is a visible-light image stitched together from 63 separate pointings of the Hubble Space Telescope. This image forms the base map in Google Sky. Stretching twice the width of the full Moon, it is the largest unbroken color mosaic ever made with Hubble and contains images of approximately 50,000 faraway galaxies. Light has traveled for more than 10 billion years from the most distant ones, giving us pictures of them as they looked long ago, more than three-quarters of the way back to the Big Bang. The exquisite detail of the Hubble images shows infant and adolescent galaxies as they began to form.
The second image shows the same galaxies through the ultraviolet eyes of NASA's Galaxy Evolution Explorer (GALEX) satellite. Ultraviolet wavelengths are shorter and bluer than those of visible light. Massive, hot young stars that are just forming produce ultraviolet light in abundance. Brightness in the GALEX image therefore provides a measure of the rate at which each galaxy is forming stars. Galaxies that contain relatively few hot, young stars or that are obscured by either their own dust or diffuse gas along our line of sight will appear redder in the GALEX image.
The third view is a mosaic of images taken with the Infrared Array Camera on NASA's Spitzer Space Telescope, the last mission in NASA's Great Observatory series. Near-infrared brightness is closely related to the total number of stars in a galaxy, while the colors of a galaxy as seen through infrared eyes reveal information on both its contents (stars and dust) and its distance from us.
The fourth image was produced with data from NASA's Chandra X-ray Observatory. In the objects seen by Chandra, highly energetic x-ray radiation has been produced when gas is spiralling into a supermassive black hole, like those believed to lie at the center of almost every galaxy. Many of the x-ray-emitting objects lie buried within otherwise normal-looking galaxies. In the x-ray images, the bluest objects are the ones most obscured by gas within their host galaxies.
In the objects seen by Chandra, X-ray radiation has been produced when gas is spiralling into a super massive black hole, like those believed to lie at the centre of almost every galaxy. Many of the X-ray emitting objects lie buried within otherwise normal-looking galaxies. In these X-ray images, the bluest objects are the ones most obscured by gas within their host galaxies, according to researchers at Imperial College in London.
In combination, these images simultaneously measure the sizes and shapes of galaxies, their current rates of star formation, the total number of stars each galaxy has already formed, and the rate at which a black hole at its center is actively accreting matter. All of this information provides separate clues to help scientists understand the evolution of galaxies over the past 10 billion years.
These images from space-based telescopes are tied together by the spectra of nearly 15,000 AEGIS galaxies taken with the Keck II Telescope in Hawaii as part of the DEEP2 Galaxy Redshift Survey, led by Faber and Marc Davis of UC Berkeley. Among other information, these spectra enable astronomers to determine distances to these objects, which is crucial for distinguishing small galaxies in the foreground from giant galaxies that appear faint because they are so far away. Once they have determined the distance to a galaxy, astronomers know how far back in time light left it. The most distant galaxies in the AEGIS survey are seen as they looked only a few billion years after the Big Bang.
With the Sky feature in Google Earth, users can pan and zoom around all of these pictures of the sky to select individual galaxies for closer inspection. By adjusting the transparency of each image, the user can focus on only one of the AEGIS images at a time, or look at a combination (e.g., the GALEX image superimposed on Hubble). Clicking on galaxies in AEGIS catalogs brings up their distances and intrinsic properties. A further mouse click links the user to the Keck spectrum and additional information being used for AEGIS science studies.
This first data release from AEGIS is only the first step. Later releases will feature images taken at far-infrared and radio wavelengths. A master catalog is being prepared that combines information from all of AEGIS's many views of the sky. As future images are prepared, they and the growing data catalogs will all be linked through Google Sky.
The AEGIS web site gives more information about the survey, science results to date, and links to additional images and data that can be downloaded. The many windows on the universe provided by AEGIS have already produced a variety of new results on the evolution of galaxies, and many more new findings from the AEGIS team will appear soon, according to Newman.
"With this public release of both interactive images and the underlying data catalogs, the full astronomical community will now be able to take advantage of this powerful new dataset," he said.
The AEGIS teams that contributed images and data for this release include the Hubble team led by Marc Davis of UC Berkeley; the Chandra team lead by Kirpal Nandra of Imperial College, London; the Spitzer team led by Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics; and the GALEX team led by Chris Martin of the California Institute of Technology. Funding for the AEGIS collaboration was provided by the National Science Foundation and NASA.
Images are available at: http://earth.google.com/gallery/index.html
Note: This story has been adapted from material provided by University of California, Santa Cruz.

Fausto Intilla

www.oloscience.com

Mysterious Energy Burst Stuns Astronomers

Source:

http://www.sciencedaily.com/releases/2007/09/070928101200.htm

Science Daily — In a shock finding, astronomers using CSIRO’s Parkes telescope have detected a huge burst of radio energy from the distant universe that could open up a new field in astrophysics.

The research team, led by Assistant Professor Duncan Lorimer of West Virginia University, reported its discovery in the journal Science Express.
The radio burst appears to have originated at least one-and-a-half billion light-years [500 Mpc] away but was startlingly strong.
“Normally the kind of cosmic activity we’re looking for at this distance would be very faint but this was so bright that it saturated the equipment,” said Professor Matthew Bailes of Swinburne University in Melbourne.
The burst was so bright that at the time it was first recorded it was dismissed as man-made radio interference. It put out a huge amount of power (10exp33 Joules), equivalent to a large (2000MW) power station running for two billion billion years.
“The burst may have been produced by an exotic event such as the collision of two neutron stars or be the last gasp of a black hole as it evaporates completely,” Professor Lorimer said.
The burst lasted just five milliseconds.
It was found by David Narkevik, an undergraduate at the West Virginia University, when he re-analysed data taken with the Parkes telescope six years ago.
Although they’ve found only one burst, the astronomers can estimate how often they occur.
“We’d expect to see a few bursts over the whole sky every day,” said Dr John Reynolds, Officer in Charge at CSIRO’s Parkes Observatory.
“A new telescope being built in Western Australia will be ideal for finding more of these rare, transient events.
”The Australian SKA Pathfinder, which is going to be built by 2012, will have a very wide field of view—be able to see a very large piece of sky—which is exactly what you want for this kind of work,” he said.
Meanwhile, the researchers will comb archived data from the Parkes telescope for more radio bursts.
The discovery of the radio burst is similar to the discovery of gamma-ray bursts in the 1970s, when military satellites revealed flashes of gamma-rays appearing all over the sky. One kind—the so-called long-period bursts—was eventually identified as the explosion (supernova) of a massive star with the associated formation of a black hole.
Note: This story has been adapted from a news release issued by CSIRO Australia.

Fausto Intilla

www.oloscience.com

Baby Booms And Birth Control In Space

Source:

http://www.sciencedaily.com/releases/2007/09/070925092520.htm

Science Daily — Stars in galaxies are a bit similar to people: during the first phase of their existence they grow rapidly, after which a stellar birth control occurs in most galaxies.

New observations from Dutch astronomer Mariska Kriek with the Gemini Telescope on Hawaii and the Very Large Telescope (VLT) in Chile, have shown that a part of the heavy galaxies already stopped forming stars when the universe was still a toddler, about 3 billion years old. Astronomers suspect that black holes exert an influence on this halt in births.
Heavy galaxies are a boring phenomenon in the modern universe. They have an elliptical or a round form, the stars are evenly distributed over the galaxies and no more new stars are formed.
The large quantities of stars, about 10 billion, and the current, low birth rate point to the fact that star formation must have been much higher in the past. When were these stars formed and why did the star formation subsequently stop?
Black holes as a birth control measure
The finite speed of light makes it possible to study the universe when it was much younger than now. With the help of spectrographs, such as the Gemini Near-InfraRed Spectrograph and SINFONI on the VLT, Mariska Kriek and her colleagues studied 36 heavy galaxies in the early universe.
These galaxies are so far away that the light from them has taken 11 billion years to reach us. Interestingly the researchers found no signs of star formation for a large proportion of the galaxies observed. This new discovery contributes to the growing mass of evidence that the formation of new stars in heavy galaxies is strongly inhibited after an explosive baby boom.
This 'halt in births' is possibly due to the influence of the enormous black holes in the middle of the galaxies. The large amount of material attracted by these black holes generates enormous quantities of energy that subsequently heats up the gas in the galaxy.
As a result of this heating the gas is no longer able to form new stars. The researchers did indeed discover a black hole in a number of the galaxies they investigated. These were mainly the galaxies where the star formation was inhibited less than 1 billion years ago. These results support the idea that black holes limit the birth of new stars.
Note: This story has been adapted from a news release issued by Netherlands Organization for Scientific Research.

Fausto Intilla

www.oloscience.com

Some Black Holes May Not Be Black, But Rather 'Naked Singularities'

Source:

http://www.sciencedaily.com/releases/2007/09/070924151118.htm

Science Daily — Researchers from Duke University and the University of Cambridge think there is a way to determine whether some black holes are not actually black.

Finding such an unmasked form of what physicists term a singularity "would shock the foundation of general relativity," said Arlie Petters, a Duke professor of mathematics and physics who worked with Marcus Werner, Cambridge graduate student in astrophysics, on a report posted online Monday, Sept. 24, for the research journal Physical Review D.
"It would show that nature has surprises even weirder than black holes," Petters added.
Albert Einstein originally theorized that stars bigger than the sun can collapse and compress into singularities, entities so confining and massively dense that the laws of physics break down inside them.
Astronomers have since found indirect evidence for these entities, which are popularly known as black holes because of the "cosmic censorship conjecture." This conjecture is that "realistic" singularities -- meaning those that can be formed in nature -- must always hide within a barrier known as an "event horizon" from which light can never escape. That makes them appear perpetually black to the rest of the universe.
But cosmic censorship is "an open conjecture that is very difficult to prove, and very difficult to disprove," said Petters.
And, despite the general support for the universality of black holes, Kip Thorne and John Preskill, two experts in the cosmology of relativity at the California Institute of Technology, have suggested for more than a decade that naked singularities could exist in certain instances. Now Petters and Werner have devised a way to test for their presence.
Astronomers cannot say for sure whether all black holes are actually black, having never fully penetrated the obscuring outward matter surrounding such objects, Petters said. As their main evidence, scientists can only point to effects that the massive gravitational pull of certain unseen entities exert on surrounding matter. Those effects include emissions of highly energetic radiation, or the extreme orbits of nearby stars.
Petters is an expert in "gravitational lensing," another effect of relativity that permits massive sources of gravity to split light from background astronomical features into multiple images.
In earlier reports in the November, 2005 and February, 2006 issues of Physical Review D, he and Charles Keeton of Rutgers University suggested a way to use gravitational lensing to show whether cosmic censorship can ever be violated.
However, that evaluation was limited to non-spinning singularities that are considered only theoretically possible. The suspected singularities astronomers have found in space so far all appear to be rapidly spinning, sometimes at more than 1,000 times a second.
So Petters and Werner teamed up to see if they could generalize such an application of gravitational lensing to all realistic spinning singularities. Their surprising result was yes, Petters said.
In work supported by the National Science Foundation in the United States and the Science and Technology Facilities Council in the United Kingdom, the pair employed a finding that a black hole could be shed of its event horizon and become a naked singularity if its angular momentum -- an effect of its spin -- is greater than its mass.
That would translate into a spin of a few thousand rotations a second in the case of a black hole weighing about 10 times more than our Sun, said Werner.
In the event that the required conditions were met, Petters' and Werner's calculations show that a naked singularity's massive gravitation would split the light of background stars or galaxies in telltale ways that are potentially detectable by astronomers using existing or soon-to-be instruments.
Those possible ways are outlined by six different equations in their study that connect a singularity's spin to the separations, angular alignments and brightness of the two split images.
"If you ask me whether I believe that naked singularities exist, I will tell you that I'm sitting on the fence," said Petters. "In a sense, I hope they are not there. I would prefer to have covered-up black holes. But I'm still open-minded enough to entertain the 'otherwise' possibility."
Note: This story has been adapted from a news release issued by Duke University.

Fausto Intilla

www.oloscience.com

Early Star Formation In The Universe Illuminated

Source:

http://www.sciencedaily.com/releases/2007/09/070913140318.htm

Science Daily — A groundbreaking study has provided new insight into the way the first stars were formed at the start of the Universe, some 13 billion years ago.

Cosmologists from Durham University, publishing their results in the journal, Science, suggest that the formation of the first stars depends crucially on the nature of 'dark matter', the strange material that makes up most of the mass in the universe.
The discovery takes scientists a step further to determining the nature of dark matter, which remains a mystery since it was first discovered more than 70 years ago. It also suggests that some of the very first stars that ever formed can still be found in the Milky Way galaxy today.
Early structure formation in the Universe involves interaction between elusive particles known as 'dark matter'. Even though little is known about their nature, evidence for the presence of dark matter is overwhelming, from observations of galaxies, to clusters of galaxies, to the Universe as a whole.
After the Big Bang, the universe was mostly 'smooth', with just small ripples in the matter density. These ripples grew larger due to the gravitational forces acting on the dark matter particles contained in them. Eventually, gas was pulled into the forming structures, leading to the formation of the very first stars, about 100 million years after the Big Bang.
For their research, the team from Durham University's Institute for Computational Cosmology carried out sophisticated computer simulations of the formation of these early stars with accepted scientific models of so-called 'cold' as well as 'warm' dark matter.
The computer model found that for slow moving 'cold dark matter' particles, the first stars formed in isolation, with just a single, larger mass star forming per developing spherical dark matter concentration.
In contrast, for faster-moving 'warm dark matter', a large number of stars of differing sizes formed at the same time in a big burst of star formation. The bursts occurred in long and thin filaments.
One of the researchers, Dr Liang Gao, who receives funding from the UK's Science and Technologies Facilities Council, said: "These filaments would have been around 9000 light years long, which is about a quarter of the size of the Milky Way galaxy today. The very luminous star burst would have lit-up the dark universe in spectacular fashion."
Stars forming in the cold dark matter are massive. The larger a star is, the shorter its life span, so these larger mass stars would not have survived until today. However the warm dark matter model predicts the formation of low mass stars as well as larger ones and the scientists say the low mass stars would survive until today.
The research paves the way for observational studies which could bring scientists closer to finding out more about the nature of dark matter. Co-researcher, Dr Tom Theuns, said: "A key question that astronomers often ask is 'where are the descendants of the first stars today"' The answer is that, if the dark matter is warm, some of these primordial stars should be lurking around our galaxy."
The Durham University scientists also give new insights into the way that black holes could be formed. Most galaxies harbour in their centres monster black holes, some with masses more than a billion times the mass of the sun.
The team hypothesises that collisions between stars in the dense filament in the warm dark matter scenario lead to the formation of the seeds for such black holes.
Dr Theuns added: "Our results raise the exciting prospect of learning about the nature of dark matter from studying the oldest stars. Another tell-tale sign could be the gigantic black holes that live in centres of galaxies like the Milky Way. They could have formed during the collapse of the first filaments in a universe dominated by warm dark matter."
Note: This story has been adapted from a news release issued by Durham University.

Fausto Intilla

www.oloscience.com