Citizen Scientists Reveal a Bubbly Milky Way

The findings make scientists suspect that the Milky Way is a much more active star-forming galaxy than previously thought.

A team of volunteers has pored over observations from NASA’s Spitzer Space Telescope and discovered more than 5,000 “bubbles” in the disk of our Milky Way Galaxy. Hot, young stars blow these bubbles into surrounding gas and dust, indicating areas of new star formation.Upwards of 35,000 “citizen scientists” sifted through the Spitzer infrared data as part of the online Milky Way Project to find these telltale bubbles. The volunteers have turned up 10 times as many bubbles as previous surveys so far.“These findings make us suspect that the Milky Way is a much more active star-forming galaxy than previously thought,” said Eli Bressert from the European Southern Observatory, Germany, and the University of Exeter, England. “The Milky Way’s disk is like champagne with bubbles all over the place,” he said.Computer programs struggle at identifying the cosmic bubbles, but human eyes and minds do an excellent job of noticing the wispy arcs of partially broken rings and the circles-within-circles of overlapping bubbles. The Milky Way Project taps into the “wisdom of crowds” by requiring that at least five users flag a potential bubble before its inclusion in the new catalog. Volunteers mark any candidate bubbles in the infrared Spitzer images with a sophisticated drawing tool before proceeding to scour another image.“The Milky Way Project is an attempt to take the vast and beautiful data from Spitzer and make extracting the information a fun, online, public endeavor,” said Robert Simpson from Oxford University, England.The data come from the Spitzer Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and Multiband Imaging Photometer for Spitzer Galactic (MIPSGAL) surveys. These datasets cover a narrow, wide strip of the sky measuring 130° wide and just 2° tall. From a stargazer’s perspective, a 2° strip is about the width of your index finger held at arm’s length, and your arms opened to the sky span about 130°. The surveys peer through the Milky Way’s disk and right into our galaxy’s heart.

The bubbles tagged by the volunteers vary in size and shape, both with distance and due to local gas cloud variations. The results will help astronomers better identify star formation across the galaxy. One topic under investigation is triggered star formation in which the bubble-blowing birth of massive stars compresses nearby gas that then collapses to create further fresh stars.

“The Milky Way Project has shown that nearly a third of the bubbles are part of hierarchies where smaller bubbles are found on or near the rims of larger bubbles,” said Matthew Povich from Penn State, University Park. “This suggests new generations of star formation are being spawned by the expanding bubbles.”

Variations in the distribution pattern of the bubbles intriguingly hint at structure in the Milky Way. For example, a rise in the number of bubbles around a gap at one end of the survey could correlate with a spiral arm. Perhaps the biggest surprise is a drop-off in the bubble census on either side of the galactic center. “We would expect star formation to be peaking in the galactic center because that’s where most of the dense gas is,” said Bressert. “This project is bringing us way more questions than answers.”

In addition, the Milky Way Project users have pinpointed many other phenomena, such as star clusters and dark nebulae, as well as gaseous “green knots” and “fuzzy red objects.” Meanwhile, the work with the bubbles continues, with each drawing helping to refine and improve the catalog.

For those interested in counting bubbles and contributing to the Milky Way Project, visit its website.

To learn of other citizen science-based efforts, check out the Zooniverse.

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IEWY Home » Science/Environment

NASA’s Chandra Finds Largest Galaxy Cluster in Early Universe

An exceptional galaxy cluster, the largest seen in the distant universe, has been found using NASA’s Chandra X-ray Observatory and the National Science Foundation-funded Atacama Cosmology Telescope (ACT) in Chile.

Officially known as ACT-CL J0102-4915, the galaxy cluster has been nicknamed “El Gordo” (“the big one” or “the fat one” in Spanish) by the researchers who discovered it. The name, in a nod to the Chilean connection, describes just one of the remarkable qualities of the cluster, which is located more than 7 billion light years from Earth. This large distance means it is being observed at a young age.

“This cluster is the most massive, the hottest, and gives off the most X-rays of any known cluster at this distance or beyond,” said Felipe Menanteau of Rutgers University in New Brunswick, N.J., who led the study.

Galaxy clusters, the largest objects in the universe that are held together by gravity, form through the merger of smaller groups or sub-clusters of galaxies. Because the formation process depends on the amount of dark matter and dark energy in the universe, clusters can be used to study these mysterious phenomena.

Dark matter is material that can be inferred to exist through its gravitational effects, but does not emit and absorb detectable amounts of light. Dark energy is a hypothetical form of energy that permeates all space and exerts a negative pressure that causes the universe to expand at an ever-increasing rate.

“Gigantic galaxy clusters like this are just what we were aiming to find,” said team member Jack Hughes, also of Rutgers. “We want to see if we can understand how these extreme objects form using the best models of cosmology that are currently available.”

Although a cluster of El Gordo’s size and distance is extremely rare, it is likely that its formation can be understood in terms of the standard Big Bang model of cosmology. In this model, the universe is composed predominantly of dark matter and dark energy, and began with a Big Bang about 13.7 billion years ago.

The team of scientists found El Gordo using ACT thanks to the Sunyaev-Zeldovich effect. In this phenomenon, photons in the cosmic microwave background interact with electrons in the hot gas that pervades these enormous galaxy clusters. The photons acquire energy from this interaction, which distorts the signal from the microwave background in the direction of the clusters. The magnitude of this distortion depends on the density and temperature of the hot electrons and the physical size of the cluster.

X-ray data from Chandra and the European Southern Observatory’s Very Large Telescope, an 8-meter optical observatory in Chile, show El Gordo is, in fact, the site of two galaxy clusters colliding at several million miles per hour. This and other characteristics make El Gordo akin to the well-known object called the Bullet Cluster, which is located almost 4 billion light years closer to Earth.

As with the Bullet Cluster, there is evidence that normal matter, mainly composed of hot, X-ray bright gas, has been wrenched apart from the dark matter in El Gordo. The hot gas in each cluster was slowed down by the collision, but the dark matter was not.

“This is the first time we’ve found a system like the Bullet Cluster at such a large distance,” said Cristobal Sifon of Pontificia Universidad de Catolica de Chile (PUC) in Santiago. “It’s like the expression says: if you want to understand where you’re going, you have to know where you’ve been.”

These results on El Gordo are being announced at the 219th meeting of the American Astronomical Society in Austin, Texas. A paper describing these results has been accepted for publication in The Astrophysical Journal.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

New Evidence for Liquid Water on Europa

Nov. 16, 2011: In a potentially significant finding in the search for life beyond Earth, scientists studying data from NASA's Galileo probe have discovered what appears to be a body of liquid water the volume of the North American Great Lakes locked inside the icy shell of Jupiter’s moon Europa.

The water could represent a potential habitat for life, and many more such lakes might exist throughout the shallow regions of Europa’s shell, say researchers writing in the journal Nature.

"The data opens up some compelling possibilities," said Mary Voytek, director of NASA's Astrobiology Program at agency headquarters in Washington. "However, scientists worldwide will want to take a close look at this analysis and review the data before we can fully appreciate the implication of these results."

A new study of data from the Galileo probe suggest Grate-Lake-sized bodies of water exist in the icy shell of Europa. Credit: Britney Schmidt/Dead Pixel FX/Univ. of Texas at Austin [video]

The Galileo spacecraft, launched by the space shuttle Atlantis in 1989, provided scientists decades of data to analyze before the probe plunged into Jupiter's atmosphere in 2003. One of the most significant discoveries was the inference of a global salt water ocean below the surface of Europa. This ocean is deep enough to cover the whole surface of Europa and contains more liquid water than all of Earth's oceans combined. However, being far from the sun, the ocean surface is completely frozen. Most scientists think this ice crust is tens of miles thick.

"One opinion in the scientific community has been if the ice shell is thick, that's bad for biology. That might mean the surface isn't communicating with the underlying ocean," said Britney Schmidt, lead author of the Nature paper and postdoctoral fellow at the Institute for Geophysics, University of Texas at Austin. "Now, we see evidence that it's a thick ice shell that can mix vigorously and new evidence for giant shallow lakes. That could make Europa and its ocean more habitable."

Thera Macula (false color) is a region of likely active chaos production above a large liquid water lake in the icy shell of Europa. [larger image]

Schmidt and her team focused on Galileo images of two roughly circular, bumpy features on Europa's surface called chaos terrains. Based on similar processes seen on Earth -- on ice shelves and under glaciers overlaying volcanoes -- they developed a four-step model to explain how the features form. The model resolves several conflicting observations. Some seemed to suggest the ice shell is thick. Others suggest it is thin.

The recent analysis suggests chaos features on Europa's surface are formed by mechanisms that involve significant exchange between the icy shell and the underlying lake. This kind of "chaos" may provide a pathway for transferring nutrients and energy between the surface and the vast global ocean already thought to exist below the thick ice shell. Researchers believe this would increase the potential for life there.

"This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth's ice sheets and floating ice shelves,” said Don Blankenship, a co-author and senior research scientist at the Institute for Geophysics, where he leads airborne radar studies of Earth’s ice sheets.

The authors have good reason to believe their model is correct. Still, because the inferred lakes are several miles below the surface, the only true confirmation of their presence would come from a future spacecraft mission designed to probe the ice shell. Such a mission was rated as the second highest priority flagship mission by the National Research Council's recent Planetary Science Decadal Survey and is being studied by NASA.

For more images and a video animation of the findings, visit the University of Texas at Austin. .

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Production Editor: Dr. Tony Phillips | Credit: Science@NASA

Another Antimatter Supernova Discovered

by Nicholos Wethington on January 7, 2010

From UniverseToday.com

Here’s another extremely explosive supernova that can be chalked up to the production of antimatter in the core of the star: Y-155. These types of supernova explosions – which can be ten times brighter than the already spectacular explosion of a Type Ia supernova – have been theorized to exist for over forty years. About a month ago, we reported on the first observations of one of these types of supernovae, and at the American Astronomical Society super-meeting yesterday, Peter Garnavich of the University of Notre Dame presented on the observation of a second.

The star Y-155 was a whopping large star, with a mass of over 200 times that of our Sun. In these types of stars, energetic gamma rays can be created by the intense heat in the core of the star. These gamma rays in turn make pairs of electrons and positrons, or antimatter pairs. Since so much energy goes to the creation of these pairs, the pressure pushing outwards on the star weakens, and gravity swoops in to collapse the star, generating a supernova of enormous proportions.

These types of supernovae have been dubbed “pair-instability” supernovae, and once they explode, there is nothing left: in other types of supernovae, a neutron star or black hole can form out of the remnants of the star, but pair-instability supernovae explode with such force that there is nothing left where the core of the star once existed.

In addition to Supernova 2007bi, which we reported on in Dec of 2009, the Supernova 2006gy is another candidate for this supernova type.

Y-155, which lies in the constellation Cetus, was discovered as part of the Equation of State: SupErNovae trace Cosmic Expansion,”ESSENCE”, search for stellar explosions. During the 6-year search, a team of international astronomers led Christopher Stubbs of Harvard University collaborated to find Type Ia supernovae as a means to measure the expansion of the Universe. These types of supernovae explode with a characteristic luminosity, making them excellent candidates to measure distances in the Universe. The team utilized the National Optical Astronomy Observatory’s (NOAO) 4-m Blanco telescope in Chile.

Y-155 was discovered in November of 2007, during the last weeks of the project, using the Blanco telescope. Once the initial discovery was made, followup observations using the Keck 10-m telescope in Hawaii, the Magellan telescope in Chile, and the MMT telescope in Arizona revealed the redshifting of the light due to the expansion of the Universe to be about 80%, meaning that the star is very far away, and thus very old. Y-155 is estimated to have undergone a supernova approximately 7 billion years ago.

According to Garnavich, the team calculated the star to be generating 100 billion times the energy of the Sun at its peak. To accomplish this, it must have synthesized between 6 and 8 solar masses of nickel 56, which is what gives Type Ia supernovae their brightness. For comparison, the typical Type Ia supernova burns 0.4-0.9 solar masses of nickel 56.

Y-155 has been shown by deep imaging with the Large Binocular Telescope in Arizona to reside in a galaxy that is rather small. Smaller galaxies are usually low in heavier atoms. The gas out of which this and other types of ultra-massive stars form is relatively pristine, composed largely of hydrogen and helium. Supernova 2007bi, the first-observed pair-instability supernova, grew up in a galaxy remarkably like that of Y155.

This means that when astronomers look for other types of pair-instability supernovae, they should find more of them in smaller galaxies that existed near the beginning of the Universe, before other supernovae synthesized heavier elements and spread them around.

Source: Physorg

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Another Asteroid To Give Earth a Close Shave June 27, 2011

by Nancy Atkinson on June 23, 2011 from UniverseToday.com

A newly discovered house-sized asteroid will miss the Earth by less than 17,700 km (11,000 miles) on Monday June 27, 2011. That’s about 23 times closer than the Moon. The size and location of the asteroid, named 2011 MD, should allow observers in certain locations to take a look at the space rock, even with small telescopes.

It’s closest approach will be at 13:26 UTC (9:26 AM EDT) on June 27.

According to Skymania, 2011 MD was found just yesterday, June 22, by LINEAR, a pair of robotic telescopes in New Mexico that scan the skies for Near Earth Asteroids.

As of now, asteroid 2011 MD is estimated to be between 9 to 45 meters (10 to 50 yards) wide. Dr. Emily Baldwin, of Astronomy Now magazine, said there is no danger of the asteroid hitting Earth, and even if it did enter the atmosphere, an asteroid this size would “mostly burn up in a brilliant fireball, possibly scattering a few meteorites.”

To find out updated information on 2011 MD’s ephemeris, physical parameters and more, including an orbit diagram and close-approach data, see this page on JPL’s Solar System Dynamics website.

Tagged as: 2011 MD, Asteroids

NASA UPDATE FROM SPACE.COM

A small asteroid the size of a tour bus will make an extremely close pass by the Earth at about that time, but it poses no threat to the planet.

The asteroid will make its closest approach at 9:26 a.m. EDT (1326 GMT) on June 27 and will pass just over 7,500 miles (12,000 kilometers) above the Earth's surface, NASA officials say. At that particular moment, the asteroid — which scientists have named 2011 MD — will be sailing high off the coast of Antarctica, almost 2,000 miles (3,218 km) south-southwest of South Africa.

NOTE THAT THE 11,000 MILE FIGURE GIVEN ABOVE IS THE DISTANCE TO THE EARTH'S CENTER.

THE 7500 MILES FIGURE ABOVE IS AN ALTITUDE DISTANCE ABOVE THE CLOSEST POINT ON THE EARTH'S SURFACE.

Asteroid 2011 MD was discovered Wednesday (June 22) by LINEAR, a pair of robotic telescopes in New Mexico that scan the skies for near-Earth asteroids. The best estimates suggest that this asteroid is between 29 to 98 feet (9 to 30 meters) wide.

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THE ASTRONOMY PICTURE OF THE DAY FOR 2011 June 14

The Universe Nearby

Credit: 2MASS, T. H. Jarrett, J. Carpenter, & R. Hurt

Explanation: What does the universe nearby look like? This plot shows nearly 50,000 galaxies in the nearby universe detected by the Two Micron All Sky Survey infrared light. (2MASS) in The resulting image is anincredible tapestry of galaxies that provides limits on how the universe formed and evolved. The dark band across the image center is blocked by dust in the plane of our own Milky Way Galaxy. Away from the Galactic plane, however, each dot represents a galaxy, color coded to indicate distance. Bluer dots represent the nearer galaxies in the 2MASS survey, while redder dots indicating the more distant survey galaxies that lie at a redshift near 0.1 . Named structures are annotated around the edges. Many galaxies are gravitationally bound together to form clusters, which themselves are loosely bound into superclusters, which in turn are sometimes seen to align over even larger scale structures.

THE ASTRONOMY PICTURE OF THE DAY FOR 2011 June 5

Another Nearby Supernova in the Whirlpool Galaxy Discovered 2011 May 31st

Credit & Copyright: Stephane Lamotte Bailey, Marc Deldem, & Jean-Luc Dauvergne

Explanation: One of the brightest supernovas in recent years has just been recorded in the nearby Whirlpool galaxy (M51). Surprisingly, a seemingly similar supernova was recorded in M51 during 2005, following yet another one that occurred in 1994. Three supernovas in 17 years is a lot for single galaxy, and reasons for the supernova surge in M51 are being debated. Pictured above are two images of M51 taken with a small telescope: one taken on May 30 that does not show the supernova, and one taken on June 2 which does. The June 2 image is one of the first images reported to contain the supernova. The images are blinked to show the location of the exploded star. Although most supernovas follow classic brightness patterns, the precise brightening and dimming pattern of this or any supernova is hard to predict in advance and can tell astronomers much about what is happening. Currently, the M51 supernova, designated SN 2011dh, is still bright enough to follow with a small telescope. Therefore, sky enthusiasts are encouraged to image the Whirlpool galaxy as often as possible to fill in time gaps left by intermittent observations made by the world's most powerful telescopes. Views of the developing supernova are being uploaded here.

THE ASTRONOMY PICTURE OF THE DAY FOR 2011 June 11

Supernovae in the Whirlpool

Image Credit & Copyright: R Jay Gabany

Explanation: Where do spiral galaxies keep their supernovae? Near their massive star forming regions, of course, and those regions tend to lie along sweeping blue spiral arms. Because massive stars are very short-lived, they don't have a chance to wander far from their birth place. Remarkably, in the last 6 years two Type II supernovae, representing the death explosions of massive stars, have been detected in nearby spiral M51. Along with a third supernova seen in 1994, that amounts to a supernova bonanza for a single galaxy. As demonstrated in these comparison images, SN2005cs, the supernova discovered in 2005, and more recently SN2011dh, the exceptionally bright supernova first recorded just last month, both lie along M51's grand spiral arms. Perhaps the original spiral nebula, M51 is also known as the Whirlpool Galaxy.

THE ASTRONOMY PICTURE OF THE DAY FOR 2011 MAY 23

An Unexpected Flare from the Crab Nebula

Credit: NASA, DOE, Fermi LAT, R. Buehler (SLAC, KIPAC)

Explanation: Why does the Crab Nebula flare? No one is sure. The unusual behavior, discovered over the past few years, seems only to occur in very high energy light -- gamma rays. As recently as one month ago, gamma-ray observations of the Crab Nebula by the Fermi Gamma Ray Space Telescope showed an unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and fading again in only a few days. Now usually the faster the variability, the smaller the region involved. This might indicate that the powerful pulsar at the center of the Crab, a compact neutron star rotating 30 times a second, is somehow involved. Specifically, speculation is centered on the changing magnetic field that surely surrounds the powerful pulsar. Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit the flares, possibly in ways similar to our Sun. The above image shows how the Crab Nebula normally appears in gamma rays, as compared to the Geminga pulsar, and how it then appeared during the recent brightening.

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MISSING SUNSPOTS IN 2008-9 EXPLAINED IN THE 2011 MARCH ISSUE OF NATURE

THE VIDEO BELOW SUMMARIZES THE ARTICLE

FOUND IN: Science & Engineering

Discovery Triples Number of Stars in Universe

Published: December 1, 2010

New Haven, Conn. — Astronomers have discovered that small, dim stars known as red dwarfs are much more prolific than previously thought—so much so that the total number of stars in the universe is likely three times bigger than realized.

Because red dwarfs are relatively small and dim compared to stars like our Sun, astronomers hadn’t been able to detect them in galaxies other than our own Milky Way and its nearest neighbors before now. As such, they did not know how much of the total stellar population of the universe is made up of red dwarfs.

Now astronomers have used powerful instruments on the Keck Observatory in Hawaii to detect the faint signature of red dwarfs in eight massive, relatively nearby galaxies called elliptical galaxies, which are located between about 50 million and 300 million light years away. They discovered that the red dwarfs, which are only between 10 and 20 percent as massive as the Sun, were much more bountiful than expected.

“No one knew how many of these stars there were,” said Pieter van Dokkum, a Yale University astronomer who led the research, which is described in Nature’s Dec.1 Advanced Online Publication. “Different theoretical models predicted a wide range of possibilities, so this answers a longstanding question about just how abundant these stars are.”

The team discovered that there are about 20 times more red dwarfs in elliptical galaxies than in the Milky Way, said Charlie Conroy of the Harvard-Smithsonian Center for Astrophysics, who was also involved in the research.

“We usually assume other galaxies look like our own. But this suggests other conditions are possible in other galaxies,” Conroy said. “So this discovery could have a major impact on our understanding of galaxy formation and evolution.”

For instance, Conroy said, galaxies might contain less dark matter—a mysterious substance that has mass but cannot be directly observed—than previous measurements of their masses might have indicated. Instead, the abundant red dwarfs could contribute more mass than realized.

In addition to boosting the total number of stars in the universe, the discovery also increases the number of planets orbiting those stars, which in turn elevates the number of planets that might harbor life, van Dokkum said. In fact, a recently discovered exoplanet that astronomers believe could potentially support life orbits a red dwarf star, called Gliese 581.

“There are possibly trillions of Earths orbiting these stars,” van Dokkum said, adding that the red dwarfs they discovered, which are typically more than 10 billion years old, have been around long enough for complex life to evolve. “It’s one reason why people are interested in this type of star.”

Citation: DOI: 10.1038/nature09578

PRESS CONTACT: Suzanne Taylor Muzzin 203-432-8555

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Discovery of "Arsenic-bug" Expands Definition of Life

Dec. 2, 2010: NASA-supported researchers have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism, which lives in California's Mono Lake, substitutes arsenic for phosphorus in the backbone of its DNA and other cellular components.

A microscopic image of GFAJ-1 grown on arsenic. [larger image]

"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science Mission Directorate at the agency's Headquarters in Washington. "As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."

This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this week's edition of Science Express.

Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new -- building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"

The Mono Lake Research area in central California. [larger image] [more]

The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms' vital biochemical machinery, such as DNA, proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to determine where the arsenic was incorporated.

The team chose to explore Mono Lake because of its unusual chemistry, especially its high salinity, high alkalinity, and high levels of arsenic. This chemistry is in part a result of Mono Lake's isolation from its sources of fresh water for 50 years.

Geomicrobiologist Felisa Wolfe-Simon, collecting lake-bottom sediments in the shallow waters of Mono Lake in California. Credit: ©2010 Henry Bortman [more]

The results of this study will inform ongoing research in many areas, including the study of Earth's evolution, organic chemistry, biogeochemical cycles, disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research.

"The idea of alternative biochemistries for life is common in science fiction," said Carl Pilcher, director of the NASA Astrobiology Institute at the agency's Ames Research Center in Moffett Field, Calif. "Until now a life form using arsenic as a building block was only theoretical, but now we know such life exists in Mono Lake."

The research team included scientists from the U.S. Geological Survey, Arizona State University in Tempe, Ariz., Lawrence Livermore National Laboratory in Livermore, Calif., Duquesne University in Pittsburgh, Penn., and the Stanford Synchroton Radiation Lightsource in Menlo Park, Calif.

NASA's Astrobiology Program in Washington contributed funding for the research through its Exobiology and Evolutionary Biology program and the NASA Astrobiology Institute. NASA's Astrobiology Program supports research into the origin, evolution, distribution, and future of life on Earth.

Editor: Dr. Tony Phillips | Credit: Science@NASA

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Published online 20 October 2010 | Nature | doi:10.1038/news.2010.552

Most Distant Galaxy Ever Found Sheds Light on Infant Cosmos

Object allows astronomers a glimpse of Universe's era of 'reionization'.

Zeeya Merali

Observations of the most distant object yet discovered go a long way in supporting astronomers' models of the early Universe. But the far-flung galaxy, details of which are published in Nature 2010 Oct 20¹, also raises questions about the source of the first light in the cosmos.

Light from the galaxy, named UDFy-38135539, left the object just 600 million years after the Big Bang, giving a snapshot of the cosmos in its infancy. This value smashes the previous record held by a galaxy by 150 million years². The image shows the galaxy as it was when it was around 100 million years old and is just 1-10% of the mass of the Milky Way.

The galaxy is particularly fascinating because, 600 million years after the Big Bang, the Universe was thought to be going through a phase called reionization. However, there has been little direct observational evidence for this, says astronomer Matt Lehnert at the Paris Observatory in France, who led the team involved in the study. According to astronomers' best models, the early Universe burst out of the Big Bang around 13 billion years ago as an ionized fireball. This ball of gas gradually cooled, becoming neutral as protons and neutrons combined to form hydrogen. "Then stars and galaxies began to form, lighting up the Universe, heating up the gas and reionizing it," says Lehnert. "This galaxy allows us to peek at the reionization era."

At the Limit

The first hint of the galaxy's existence came when astronomers scrutinized a near-infrared image taken by the Hubble Space Telescope's Wide Field Camera and saw "a faint blob", says Lehnert³. To confirm its distance, Lehnert and his colleagues searched for a characteristic signature, called the Lyman-α line, that is seen in the spectrum of light emitted by galaxies. The Lyman-α line is produced as electrons move between two energy levels in a hydrogen atom. The wavelength of the light is shifted towards the red end of the spectrum by an amount that is related to the motion and distance of the source from which it is emitted. As this 'redshift' is greater the older the object being observed, it allows astronomers to calculate an object's age. Using the ground-based Very Large Telescope in Paranal, Chile, the team detected the line, and calculated that it had a redshift of 8.55, indicating that the light had travelled around 600 million years to reach Earth.

“They are really pushing the instrumentation to its limit.”

James Dunlop, an astronomer at the University of Edinburgh, UK, who was part of the team that found the galaxy candidate in the Hubble data, says the result is "exciting, if proved correct". But he adds that it is also "slightly controversial" because it is based on the discovery of just one spectral line, making it tough to establish that this is not just an artefact of the measuring process. "They are really pushing the instrumentation to its limit," says Dunlop.

Lehnert emphasizes that the team took pains to rule out the possibility that the line was caused by background contamination from molecules in Earth's atmosphere. "It took months for us to convince ourselves that this is real," he says.

Strong signal

The galaxy seems to confirm astronomers' models of the early Universe, which predict that young galaxies were responsible for reionization around 600 million years after the Big Bang⁴, says Martin Haehnelt, a cosmologist at the University of Cambridge, UK. But he notes that typical galaxies do not produce Lyman-α lines that are as strong as the one seen by Lehnert's group, making the finding puzzling.

Lehnert's team argues that the line may be unusually strong because there are additional, as yet undetected, galaxies surrounding the newly discovered one, giving it a helping hand in reionization. "This could help explain it, but even then, the strength is still surprisingly large," says Haehnelt. "This is a very nice result, but it is important to be cautious about it."

It will be difficult to investigate the galaxy further using ground-based telescopes, as the data will be contaminated by 'noise' from Earth's atmosphere. However, the James Webb Space Telescope, due to launch in 2015, will train its spectrographic instruments on this region, in an effort to delve even further back into the Universe's infancy. It will also help astronomers to unpick the puzzle of the strength of the Lyman-α line, by revealing exactly what kind of galaxies are responsible for reionization, says Dunlop. "This is the sort of galactic archaeology that the next generation of telescopes will be able to do," he adds.

• • References

    • 1. Lehnert M. D. et al. Nature 467, 940-942 (2010).

      2. Iye, M. et al. Nature 443, 186-188 (2006).

      3. McLure, R. J. et al. Mon. Not. R. Astron. Soc. 403, 960-983 (2010).

      4. Choudhury, T. R. , Haehnelt, M. G. & Regan, J. Mon. Not. R. Astron. Soc. 394, 960-977 (2009).

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Oldest Material in Solar System Found

Discovery suggests exploding star kick-started our sun.

An artist's conception of a young star system, before its dusty disk has coalesced into rocky bodies.

Image courtesy NASA

Andrew Fazekas

for National Geographic News

Published August 23, 2010

Pea-size minerals inside a meteorite are the oldest known material in the solar system, a new study says.

At 4,568.2 million years old, the minerals push back the birth of the solar system by as much as two million years—and suggests that an exploding star injected key materials into our system as it was being born, researchers say.

(Related: "Saturn's Rings as Old as Solar System, Study Says.")

The 3-pound (1.5-kilogram) parent meteorite, dubbed NWA 2364, was found in 2004 in Morocco and is believed to have originated from the asteroid belt between Mars and Jupiter.

But the tests reveal that telltale mineral lumps inside—called calcium-aluminum inclusions—are from a time before that asteroid belt existed. The minerals may have formed just after part of an interstellar gas and dust cloud, or nebula, had collapsed and formed our sun, as one sun-formation theory goes.

"Soon after the collapse of the solar nebula, matter started to condense as the temperature went down, and these inclusions started forming," said lead study author Audrey Bouvier, a research associate at Arizona State University's Center for Meteorite Studies.

Bouvier and co-author Meenakshi Wadhwa, also of Arizona State, measured ratios of lead isotopes—lighter-or-heavier-than-usual versions of an element—in a single "pristine" inclusion to uncover its birth date, she said.

"This revised age is between 0.3 and 1.9 million years older than previous estimates," she said, "making it the oldest on record."

(Also see "Oldest Rocks on Earth Discovered?")

Supernova Blasted Solar System Into Existence?

Two million years is a drop in the bucket in cosmic time, but it could have major ramifications for how scientists think the solar system was born.

Again, it comes down to isotopes—in this case, iron-60, which forms when massive stars go supernova, exploding at the ends of their lives.

Previous studies by other scientists of iron-60 isotopes in mineral inclusions in meteorites found that the inclusions had formed roughly two million years after what was thought to have been the birth of the solar system.

But because the solar system is now apparently up to two million years older than previously thought, the abundance of iron-60 estimated from the inclusions must be extrapolated back another two million years. Since iron-60 degrades by half every two million years, the revised initial quantity of iron-60 in the solar system is almost double previous estimates.

The only thing that could have put so much iron-60 into the nascent solar system, she added, is a nearby supernova.

If true, the finding supports a theory that a supernova seeded the ancient solar nebula with heavy metals and possibly triggered its collapse nearly 4.57 billion years ago.

(Related: "Supernova's Beginning Blast Seen in 3-D—A First.")

"I think it is important that people understand that this matter now present in our solar system has been brought in by other stars," Bouvier said.

"Massive stars may have exploded nearby but not close enough to destroy it—but instead brought in these key elements for planet formation and life."

For an insider's take on space news, check National Geographic's Breaking Orbit blog >>

The findings on the ancient solar system material were published August 22 in the journal Nature Geoscience.

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From UniverseToday.com for 2010 June 10

Many Famous Comets May be Visitors from Other Solar Systems

Written by Nancy Atkinson

Most comets are thought to have originated great distances away, traveling to the inner solar system from the Oort Cloud. But new computer simulations show that many comets – including some famous ones – came from even farther: they may have been born in other solar systems. Many of the most well known comets, including Hale-Bopp (above), Halley, and, most recently, McNaught, may have formed around other stars and then were gravitationally captured by our Sun when it was still in its birth cluster. This new finding solves the mystery of how the Oort cloud formed and why it is so heavily populated with comets.

Comets are believed to be leftovers from the formation of the solar system. They are observed to come to the solar system from all directions, so astronomers have thought the comet's origin was from the Oort Cloud, a giant sphere surrounding the solar system. Some comets travel over 100,000 AU, in a huge orbit around the sun.

But comets may have formed around other stars in the cluster where the sun was born and been captured gravitationally by our sun.

Dr. Hal Levison from the Southwest Research Insitutue, along with Dr. Martin Duncan from Queen's University, Kingston, Canada, Dr. Ramon Brasser, Observatoire de la Côte d'Azur, France and Dr. David Kaufmann (SwRI) used computer simulations to show that the Sun may have captured small icy bodies from its sibling stars while still in its star-forming nursery cluster.

The researchers investigated what fraction of comets might be able to travel from the outer reaches of one star to the outer reaches of another. The simulations imply that a substantial number of comets can be captured through this mechanism, and that a large number of Oort cloud comets come from other stars. The results may explain why the number of comets in the Oort cloud is larger than models predict.

While the Sun currently has no companion stars, it is believed to have formed in a cluster containing hundreds of closely packed stars that were embedded in a dense cloud of gas. During this time, each star formed a large number of small icy bodies (comets) in a disk from which planets formed. Most of these comets were gravitationally slung out of these prenatal planetary systems by the newly forming giant planets, becoming tiny, free-floating members of the cluster.

The Sun's cluster came to a violent end, however, when its gas was blown out by the hottest young stars. These new models show that the Sun then gravitationally captured a large cloud of comets as the cluster dispersed.

"When it was young, the Sun shared a lot of spit with its siblings, and we can see that stuff today," said Levison.

"The process of capture is surprisingly efficient and leads to the exciting possibility that the cloud contains a potpourri that samples material from a large number of stellar siblings of the Sun," said co-author Duncan.

Evidence for the team's scenario comes from the roughly spherical cloud of comets, known as the Oort cloud, that surrounds the Sun, extending halfway to the nearest star. It has been commonly assumed this cloud formed from the Sun's proto-planetary disk. However, because detailed models show that comets from the solar system produce a much more anemic cloud than observed, another source is required.

"If we assume that the Sun's observed proto-planetary disk can be used to estimate the indigenous population of the Oort cloud, we can conclude that more than 90 percent of the observed Oort cloud comets have an extra-solar origin," Levison said.

"The formation of the Oort cloud has been a mystery for over 60 years and our work likely solves this long-standing problem," said Brasser.

"Capture of the Sun's Oort Cloud from Stars in its Birth Cluster," was published in the June 10 issue of Science Express.

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THE ASTRONOMY PICTURE OF THE DAY FOR 2009 April 28

GRB 090423: The Farthest Explosion Yet Measured

Credit: Gemini Observatory / NSF / AURA, D. Fox & A. Cucchiara (Penn State U.), and E. Berger (Harvard Univ.)

Explanation: An explosion so powerful it was seen clear across the visible universe was recorded in gamma-radiation last week by NASA's orbiting Swift Observatory. Farther than any known galaxy, quasar, or optical supernova, the gamma-ray burst recorded last week was clocked at redshift 8.2, making it the farthest explosion of any type yet detected. Occurring only 630 million years after the Big Bang, GRB 090423 detonated so early that astronomers had no direct evidence that anything explodable even existed back then. The faint infrared afterglow of GRB 090423 was recovered by large ground telescopes within minutes of being discovered. The afterglow is circled in the above picture taken by the large Gemini North Telescope in Hawaii, USA. An exciting possibility is that this gamma-ray burst occurred in one of the very first generation of stars and announced the birth of an early black hole. Surely, GRB 090423 provides unique data from a relatively unexplored epoch in our universe and a distant beacon from which the intervening universe can be studied.

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FROM NASA ----------> THIS PLANET SMELLS FUNNY

Sept. 13, 2010: Giant planet GJ 436b in the Constellation Leo is missing something.

Would you Believe Swamp Gas?

To the surprise of astronomers who have been studying the Neptune-sized planet using NASA's Spitzer Space Telescope, GJ 436b has very little methane (CH₄).

"Methane should be abundant on a planet of this temperature and size, but we found 7000 times less methane than what the models predict," says Kevin Stevenson of the University of Central Florida (UCF). Stevenson was lead author of a paper reporting the result in the April 22, 2010, issue of Nature.

An artist's concept of GJ 436b peeking out from behind its parent star, an M-dwarf much cooler than the sun. [larger image]

The methane deficit is surprising because in our own solar system all gas giants are methane-rich. Hydrogen and carbon are abundant in the atmospheres of Jupiter, Saturn, Uranus and Neptune. These atoms naturally get together to form the simplest hydrocarbon, CH₄.

The example of our local gas giants shaped expectations when Stevenson and colleagues pointed Spitzer in the direction of GJ 436b, only 33 light-years away. Finding methane was a foregone conclusion. But when the researchers analyzed the planet's spectrum, they found little of it. Instead, the atmosphere was rich in carbon monoxide.

"Actually, it blew our minds," says principal investigator and co-author Joseph Harrington, also of UCF.

Where did all the methane go? One possibility: it's being broken apart. "UV radiation from the planet's star could be converting the methane into polymers like ethylene," says Harrington. "If you put plastic wrap out in the sun, the UV radiation breaks down the carbon bonds in the plastic, causing it to deteriorate as the long carbon chains break. We propose a similar process on GJ 436b, but there hydrogen atoms split off from methane and let the remnants stick together to make ethylene (C₂H₄)."

A stick-figure diagram of methane. [more]

Also, they speculate, strong vertical winds in the planet's atmosphere might be sweeping up material from deep hot layers where carbon monoxide is abundant. CO thus replaces CH₄.

Or it could be something else entirely.

"This planet's atmosphere could have some sort of alien chemistry going on," says Harrington. "We just don't know yet."

Giant planets aren't the only worlds with methane. CH₄ is fairly common on Earth, too. Methane forms in the stomachs of cows and goats. It also bubbles up from the bottom of swamps, a byproduct of organic matter decaying in deep mud. On gas giants, methane is just common chemistry, but on our planet, it is a sign of life.

For this reason, researchers have long planned to look for methane in the atmospheres of distant Earth-sized planets. NASA's Kepler mission is expected to discover many Earth-sized planets over the next few years, so the scientists will have plenty of promising targets to pursue. Methane floating alongside oxygen could be compelling evidence of biological activity.

But what if planetary atmospheres don't always follow the rules of our own Solar System? GJ 436b certainty doesn't. Investigators might have to go back to the drawing board and re-figure their chemistry.

"GJ 436b is telling us something important," says Harrington: "We’re not in Kansas anymore."

Authors: Dr. Tony Phillips, Dauna Coulter | Credit: Science@NASA

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LIGHTEST EXOPLANET DISCOVERED --

Gliese 581 e (pronounced /ˈɡliːzə/) is the fourth extrasolar planet found around Gliese 581, an M3V red dwarf star approximately 20 light-years away from Earth in the constellation of Libra. At a minimum of 1.9 Earth masses, it is the smallest extrasolar planet discovered around a normal star, and the closest in mass to Earth, though at an orbital distance of just 0.03 AU from its parent star it is well out of the habitable zone, and is unlikely to possess an atmosphere due to its high temperature, small size, and strong radiation from the star.^[1][2][3][4]

Discovery

The planet was discovered by the team of Michel Mayor of the Observatory of Geneva in Switzerland using the HARPS instrument on the European Southern Observatory 3.6 meter telescope in La Silla, Chile. The discovery was announced on 21 April 2009. Mayor's team employed the radial velocity technique, in which the orbit size and mass of a planet are determined based on the small perturbations it induces in its parent star's orbit via gravity.^[1]

References

• 1. ^ ^{a b c d e f g} Mayor et al. (2009). "The HARPS search for southern extra-solar planets,XVIII. An Earth-mass planet in the GJ 581 planetary system". Astronomy and Astrophysics. http://obswww.unige.ch/~udry/Gl581_preprint.pdf.

  2. ^ Rincon, Paul; Amos, Jonathan (2009-04-21). "Lightest exoplanet is discovered". BBC. http://news.bbc.co.uk/1/hi/sci/tech/8008683.stm. Retrieved on 2009-04-21.

  3. ^ Overbye, Dennis (April 21, 2009). "Astronomers Find Planet Closer to Size of Earth". New York Times. http://www.nytimes.com/2009/04/22/science/22planet.html.

  4. ^ "Most Earthlike Planet Yet Found May Have Liquid Oceans". National Geographic. 2009-04-21. http://news.nationalgeographic.com/news/2009/04/090421-most-earthlike-planet.html. Retrieved on 2009-04-22.

See also

• • PSR B1257+12 A — a much smaller pulsar planet

External links

• Lightest exoplanet yet discovered European Southern Observatory press release - STORY BELOW

• Scientists discover a nearly Earth-sized planet

EUROPEAN SOUTHERN OBSERVATORY (ESO) 15/09 - Science Release

21 April 2009

For Immediate Release

Lightest exoplanet yet Discovered

Well-known exoplanet researcher Michel Mayor today announced the discovery of the lightest exoplanet found so far. The planet, “e”, in the famous system Gliese 581, is only about twice the mass of our Earth. The team also refined the orbit of the planet Gliese 581 d, first discovered in 2007, placing it well within the habitable zone, where liquid water oceans could exist. These amazing discoveries are the outcome of more than four years of observations using the most successful low-mass-exoplanet hunter in the world, the HARPS spectrograph attached to the 3.6-metre ESO telescope at La Silla, Chile.

Comet C/2007 N3 (Lulin), also known as Comet Lulin, is a non-periodic comet. It was discovered by Ye Quanzhi and Lin Chi-Sheng from Lulin Observatory.^[1][2][5] It will peak in brightness for observers on Earth on February 24, 2009, between magnitude +4^[2] and magnitude +6^[5]. The comet will also pass near Saturn on February 23, will also appear to pass near and near Regulus in Leo on February 26 and 27, 2009.^[5][2] On May 12, 2009, it will then appear to pass near Comet Cardinal.^[6] It currently appears at magnitude +8.2, in the constellation Scorpius.^[7]

COMET LULIN's PATH BELOW FROM DISCOVERY TO END OF FEB 2009

COMET LULIN's PATH BELOW FROM MID-FEB 2009 TO MARCH 2010

COMET LULIN's BRIGHTNESS FOR DATA TO VERTICAL PINK LINE FOLLOWED

BY PREDICTION OF BRIGHTNESS PEAK NEAR 4 th MAG BY LATE FEB 2009

References

1. ^ ^{a b c} Kronk, Gary W.. "C/2007 N3 (Lulin)". cometography.com. Retrieved on 2009-01-02.

2. ^ ^{a b c d e} Yoshida, Seiichi (December 31, 2008). "C/2007 N3 ( Lulin )" (in English). aerith.net. Retrieved on 2009-01-02.

3. ^ ^{a b c d e f} "JPL Small-Body Data (C/2007 N3)". JPL NASA. Retrieved on 2009-01-02.

4. ^ Yeomans, Donald K.. "Horizon Online Ephemeris System". California Institute of Technology, Jet Propulsion Laboratory. Retrieved on 2009-01-02.

5. ^ ^{a b c} Dyer, Alan (2009). "Venus Kicks Off the Year of Astronomy (pg. 24-27)". in Dickinson, Terence. SkyNews: The Canadian Magazine on Astronomy & Stargazing. XIV, Issue 5 (January/February 2009 ed.). Yarker, Ontario: SkyNews Inc. pp. 38.

6. ^ Dyer, Alan (2009). "The Top 10 Celestial Sights of 2009 (pg. 14)". in Dickinson, Terence. SkyNews: The Canadian Magazine of Astronomy & Stargazing. XIV, Issue 5 (January/February 2009 ed.). Yarker, Ontario: SkyNews Inc. pp. 38.

7. ^ Peat, Chris. "Comet C/2007 N3 Lulin". Heavens-Above GmbH. Heavens-Above.com. Retrieved on 2009-01-07.

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Solar Wind Rips Up Martian Atmosphere

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Nov. 21, 2008: Researchers have found new evidence that the atmosphere of Mars is being stripped away by solar wind. It's not a gently continuous erosion, but rather a ripping process in which chunks of Martian air detach themselves from the planet and tumble into deep space. This surprising mechanism could help solve a longstanding mystery about the Red Planet.

"It helps explain why Mars has so little air," says David Brain of UC Berkeley, who presented the findings at the 2008 Huntsville Plasma Workshop on October 27th.

Billions of years ago, Mars had a lot more air than it does today. (Note: Martian "air" is primarily carbon dioxide, not the nitrogen-oxygen mix we breathe on Earth.) Ancient martian lake-beds and river channels tell the tale of a planet covered by abundant water and wrapped in an atmosphere thick enough to prevent that water from evaporating into space. Some researchers believe the atmosphere of Mars was once as thick as Earth's. Today, however, all those lakes and rivers are dry and the atmospheric pressure on Mars is only 1% that of Earth at sea-level. A cup of water placed almost anywhere on the Martian surface would quickly and violently boil away—a result of the super-low air pressure.

Above, right: An artist's concept of ancient Mars with abundant air and water. [Larger Image)

So where did the air go? Researchers entertain several possibilities: An asteroid hitting Mars long ago might have blown away a portion of the planet's atmosphere in a single violent upheaval. Or the loss might have been slow and gradual, the result of billions of years of relentless "sand-blasting" by solar wind particles. Or both mechanisms could be at work.

Brain has uncovered a new possibility--a daily ripping process intermediate between the great cataclysm and slow erosion models. The evidence comes from NASA's now-retired Mars Global Surveyor (MGS) spacecraft.

In 1998, MGS discovered that Mars has a very strange magnetic field. Instead of a global bubble, like Earth's, the Martian field is in the form of magnetic umbrellas that sprout out of the ground and reach beyond the top of Mars' atmosphere. These umbrellas number in the dozens and they cover about 40% of the planet’s surface, mainly in the southern hemisphere.

For years, researchers thought the umbrellas protected the Martian atmosphere, shielding pockets of air beneath them from erosion by the solar wind. Surprisingly, Brain finds that the opposite can be true as well: "The umbrellas are where coherent chunks of air are torn away."

Above: Solar wind blowing against Mars tears atmosphere-filled plasmoids from the tops of magnetic umbrellas. Credit: Graphic artist Steve Bartlett. [Larger image]

Addressing his colleagues at the Workshop, he described how he made the discovery just a few months ago:

Brain was scrolling through archival data from Global Surveyor's particles and fields sensors. "We have measurements from 25,000 orbits," he says. During one of those orbits, MGS passed through the top of a magnetic umbrella. Brain noticed that the umbrella's magnetic field had linked up with the magnetic field in the solar wind. Physicists call this "magnetic reconnection." What happened next is not 100% certain, but Global Surveyor's readings are consistent with the following scenario: "The joined fields wrapped themselves around a packet of gas at the top of the Martian atmosphere, forming a magnetic capsule a thousand kilometers wide with ionized air trapped inside," says Brain. "Solar wind pressure caused the capsule to 'pinch off' and it blew away, taking its cargo of air with it." Brain has since found a dozen more examples. The magnetic capsules or "plasmoids" tend to blow over the south pole of Mars, mainly because most of the umbrellas are located in Mars' southern hemisphere.

Above: Dave Brain of UC Berkeley presented this slide at the 2008 Huntsville Plasma Workshop to explain in cartoon fashion how plasmoids carry air away from Mars. [Larger image]

Brain isn't ready to declare the mystery solved. "We're still not sure how often the plasmoids form or how much gas each one contains." The problem is, Mars Global Surveyor wasn't designed to study the phenomenon. The spacecraft was only equipped to sense electrons, not the heavier ions which would make up the bulk of any trapped gas. "Ions and electrons don't always behave the same way," he cautions. Also, MGS sampled the umbrellas at fixed altitudes and at the same local time each day. "We need to sample many altitudes and times of day to truly understand these dynamic events."

In short, he told the audience, "we need more data."

Brain is pinning his hopes on a new NASA mission named MAVEN. Short for "Mars Atmosphere and Volatile Evolution," MAVEN is an upper atmosphere orbiter currently approved for launch to Mars in 2013. The probe is specifically designed to study atmospheric erosion. MAVEN will be able to detect electrons, ions and neutral atoms; it will be able to measure both magnetic and electric fields; it will travel around Mars in an elliptical orbit, piercing magnetic umbrellas at different altitudes, angles, and times of day; and it will explore regions both near and far from the umbrellas, giving researchers the complete picture they need.

If magnetized chunks of air are truly being torn free, MAVEN will see it happening and measure the atmospheric loss rate. "Personally, I think this mechanism is important," says Brain, "but MAVEN may yet prove me wrong."

Meanwhile, the Mystery of the Missing Martian Air is shaping up to be a ripping good yarn.

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Discovered:

Cosmic Rays from a Mysterious Nearby Object

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Nov. 19, 2008: An international team of researchers has discovered a puzzling surplus of high-energy electrons bombarding Earth from space. The source of these cosmic rays is unknown, but it must be close to the solar system and it could be made of dark matter. Their results are being reported in the Nov. 20th issue of the journal Nature.

"This is a big discovery," says co-author John Wefel of Louisiana State University. "It's the first time we've seen a discrete source of accelerated cosmic rays standing out from the general galactic background."

Right: An artist's concept of cosmic rays hitting Earth's upper atmosphere. Credit: Simon Swordy, University of Chicago. [Larger image]

Galactic cosmic rays are subatomic particles accelerated to almost light speed by distant supernova explosions and other violent events. They swarm through the Milky Way, forming a haze of high energy particles that enter the solar system from all directions. Cosmic rays consist mostly of protons and heavier atomic nuclei with a dash of electrons and photons spicing the mix.

To study the most powerful and interesting cosmic rays, Wefel and colleagues have spent the last eight years flying a series of balloons through the stratosphere over Antarctica. Each time the payload was a NASA-funded cosmic ray detector named ATIC, short for Advanced Thin Ionization Calorimeter. The team expected ATIC to tally the usual mix of particles, mainly protons and ions, but the calorimeter found something extra: an abundance of high-energy electrons.

Wefel likens it to driving down a freeway among family sedans, mini-vans and trucks—when suddenly a bunch of Lamborghinis bursts through the normal traffic. "You don't expect to see so many race cars on the road—or so many high-energy electrons in the mix of cosmic rays." During five weeks of ballooning in 2000 and 2003, ATIC counted 70 excess electrons in the energy range 300-800 GeV. ("Excess" means over and above the usual number expected from the galactic background.) Seventy electrons may not sound like a great number, but like seventy Lamborghinis on the freeway, it's a significant surplus.

Above: ATIC high-energy electron counts. The triangular curve fitted to the data comes from a model of dark-matter annihilation featuring a Kaluza-Klein particle of mass near 620 GeV (620 Billion Electron Volts). Details may be found in the Nov. 20, 2008, edition of Nature: "An excess of cosmic ray electrons at energies of 300-800 Gev," by J. Chang et al. [Larger image]

"The source of these exotic electrons must be relatively close to the solar system—no more than a kiloparsec away," says co-author Jim Adams of the NASA Marshall Space Flight Center.

Why must the source be nearby? Adams explains: "High-energy electrons lose energy rapidly as they fly through the galaxy. They give up energy in two main ways: (1) when they collide with lower-energy photons, a process called inverse Compton scattering, and (2) when they radiate away some of their energy by spiraling through the galaxy's magnetic field." By the time an electron has traveled a whole kiloparsec, it isn't so 'high energy' any more.

High-energy electrons are therefore local. Some members of the research team believe the source could be less than a few hundred parsecs away. For comparison, the disk of the spiral Milky Way galaxy is about thirty thousand parsecs wide. (One parsec equals 3.263 light years.)

"Unfortunately," says Wefel, "we can't pinpoint the source in the sky." Although ATIC does measure the direction of incoming particles, it's difficult to translate those arrival angles into celestial coordinates. For one thing, the detector was in the basket of a balloon bobbing around the South Pole in a turbulent vortex of high-altitude winds; that makes pointing tricky. Moreover, the incoming electrons have had their directions scrambled to some degree by galactic magnetic fields. "The best ATIC could hope to do is measure a general anisotropy—one side of the sky versus the other."

Right: The ATIC cosmic ray detector ascends to the stratosphere tethered to a high-altitude research balloon. More launch images: #1, #2, #3.

This uncertainty gives free rein to the imagination. The least exotic possibilities include, e.g., a nearby pulsar, a 'microquasar' or a stellar-mass black hole—all are capable of accelerating electrons to these energies. It is possible that such a source lurks undetected not far away. NASA's recently-launched Fermi Gamma-ray Space Telescope is only just beginning to survey the sky with sufficient sensitivity to reveal some of these objects.

An even more tantalizing possibility is dark matter.

There is a class of physical theories called "Kaluza-Klein theories" which seek to reconcile gravity with other fundamental forces by positing extra dimensions. In addition to the familiar 3D of human experience, there could be as many as eight more dimensions woven into the space around us. A popular yet unproven explanation for dark matter is that dark matter particles inhabit the extra dimensions. We feel their presence via the force of gravity, but do not sense them in any other way.

How does this produce excess cosmic rays? Kaluza-Klein particles have the curious property (one of many) that they are their own anti-particle. When two collide, they annihilate one another, producing a spray of high-energy photons and electrons. The electrons are not lost in hidden dimensions, however, they materialize in the 3-dimensions of the real world where ATIC can detect them as "cosmic rays."

"Our data could be explained by a cloud or clump of dark matter in the neighborhood of the solar system," says Wefel. "In particular, there is a hypothesized Kaluza-Klein particle with a mass near 620 GeV which, when annihilated, should produce electrons with the same spectrum of energies we observed."

Testing this possibility is nontrivial because dark matter is so, well, dark. But it may be possible to find the cloud by looking for other annihilation products, such as gamma-rays. Again, the Fermi Space Telescope may have the best chance of pinpointing the source.

"Whatever it is," says Adams, "it's going to be amazing."

For more information about this research, see "An excess of cosmic ray electrons at energies of 300-800 Gev," by J. Chang et al. in the Nov. 20, 2008, issue of Nature.

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Credits: The Advanced Thin Ionization Calorimeter is an international collaboration of researchers from Louisiana State University, University of Maryland, Marshall Space Flight Center, Purple Mountain Observatory in China, Moscow State University in Russia and Max-Planck Institute for Solar System Research in Germany. ATIC is supported in the United States by NASA and flights are conducted under the auspices of the Balloon Program Office at Wallops Flight Facility by the staff of the Columbia Scientific Balloon Facility. Antarctic logistics are provided by the National Science Foundation and its contractor Raytheon Polar Services Corporation.

NASA's Future: US Space Exploration Policy