Mars Rover Yielding New Clues While Lodged In Martian Soil

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ScienceDaily (June 28, 2009) — NASA's Mars rover Spirit, lodged in Martian soil that is causing traction trouble, is taking advantage of the situation by learning more about the Red Planet's environmental history.

In April, Spirit entered an area composed of three or more layers of soil with differing pastel hues hiding beneath a darker sand blanket. Scientists dubbed the site "Troy." Spirit's rotating wheels dug themselves more than hub deep at the site. The rover team has spent weeks studying Spirit's situation and preparing a simulation of this Martian driving dilemma to test escape maneuvers using an engineering test rover at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
A rock seen beneath Spirit in images from the camera on the end of the rover's arm may be touching Spirit's belly. Scientists believe it appears to be a loose rock not bearing the rover's weight. While Spirit awaits extraction instructions, the rover is keeping busy examining Troy, which is next to a low plateau called Home Plate, approximately 3.2 kilometers (2 miles) southeast of where Spirit landed in January 2004.
"By serendipity, Troy is one of the most interesting places Spirit has been," said Ray Arvidson of Washington University in St. Louis. Arvidson is deputy principal investigator for the science payloads on Spirit and its twin rover, Opportunity. "We are able here to study each layer, each different color of the interesting soils exposed by the wheels."
One of the rover's wheels tore into the site, exposing colored sandy materials and a miniature cliff of cemented sands. Some disturbed material cascaded down, evidence of the looseness that will be a challenge for getting Spirit out. But at the edge of the disturbed patch, the soil is cohesive enough to hold its shape as a steep cross-section.
Spirit has been using tools on its robotic arm to examine tan, yellow, white and dark-red sandy soil at Troy. Stretched-color images from the panoramic camera show the tints best.
"The layers have basaltic sand, sulfate-rich sand and areas with the addition of silica-rich materials, possibly sorted by wind and cemented by the action of thin films of water. We're still at a stage of multiple working hypotheses," said Arvidson. "This may be evidence of much more recent processes than the formation of Home Plate...or is Home Plate being slowly stripped back by wind, and we happened to stir up a deposit from billions of years ago before the wind got to it?"
Team members from NASA's Johnson Space Center in Houston feel initial readings suggest that iron is mostly present in an oxidized form as ferric sulfate and that some of the differences in tints at Troy observed by the panoramic camera may come from differences in the hydration states of iron sulfates.
While extraction plans for the rover are developed and tested during the coming weeks, the team plans to have Spirit further analyze the soil from different depths. This research benefits from having time and power. In April and May, winds blew away most of the dust that had accumulated on Spirit's solar panels.
"The exceptional amount of power available from cleaning of Spirit's solar arrays by the wind enables full use of all of the rover's science instruments," said Richard Moddis of the Johnson team. "If your rover is going to get bogged down, it's nice to have it be at a location so scientifically interesting."
The rover team has developed a soil mix for testing purposes that has physical properties similar to those of the soil under Spirit at Troy. This soil recipe combines diatomaceous earth, powdered clay and play sand. A crew is shaping a few tons of that mix this week into contours matching Troy's. The test rover will be commanded through various combinations of maneuvers during the next few weeks to validate the safest way to proceed on Mars.
Spirit's right-front wheel has been immobile for more than three years, magnifying the challenge. While acknowledging a possibility that Spirit might not be able to leave Troy, the rover team remains optimistic. Diagnostic tests on Spirit in early June provided encouragement that the left-middle wheel remains useable despite an earlier stall.
"With the improved power situation, we have the time to explore all the possibilities to get Spirit out," said JPL's John Callas, project manager for Spirit and Opportunity. "We are optimistic. The last time Spirit spun its wheels, it was still making progress. The ground testing will help us avoid doing things that could make Spirit's situation worse."
Images and further information about Spirit and Opportunity are available at: http://marsrovers.jpl.nasa.gov and http://www.nasa.gov/rovers .
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

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.

Mystery Of The Missing Sunspots Solved?

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ScienceDaily (June 19, 2009) — The sun is in the pits of a century-class solar minimum, and sunspots have been puzzlingly scarce for more than two years. Now, for the first time, solar physicists might understand why.

At an American Astronomical Society press conference in Boulder, Colorado, researchers announced that a jet stream deep inside the sun is migrating slower than usual through the star's interior, giving rise to the current lack of sunspots.
Rachel Howe and Frank Hill of the National Solar Observatory (NSO) in Tucson, Arizona, used a technique called helioseismology to detect and track the jet stream down to depths of 7,000 km below the surface of the sun. The sun generates new jet streams near its poles every 11 years, they explained. The streams migrate slowly from the poles to the equator and when a jet stream reaches the critical latitude of 22 degrees, new-cycle sunspots begin to appear.
Howe and Hill found that the stream associated with the next solar cycle has moved sluggishly, taking three years to cover a 10 degree range in latitude compared to only two years for the previous solar cycle.
The jet stream is now, finally, reaching the critical latitude, heralding a return of solar activity in the months and years ahead.
"It is exciting to see", says Hill, "that just as this sluggish stream reaches the usual active latitude of 22 degrees, a year late, we finally begin to see new groups of sunspots emerging."
The current solar minimum has been so long and deep, it prompted some scientists to speculate that the sun might enter a long period with no sunspot activity at all, akin to the Maunder Minimum of the 17th century. This new result dispells those concerns. The sun's internal magnetic dynamo is still operating, and the sunspot cycle is not "broken."
Because it flows beneath the surface of the sun, the jet stream is not directly visible. Hill and Howe tracked its hidden motions via helioseismology. Shifting masses inside the sun send pressure waves rippling through the stellar interior. So-called "p modes" (p for pressure) bounce around the interior and cause the sun to ring like an enormous bell. By studying the vibrations of the sun's surface, it is possible to figure out what is happening inside. Similar techniques are used by geologists to map the interior of our planet.
In this case, researchers combined data from GONG and SOHO. GONG, short for "Global Oscillation Network Group," is an NSO-led network of telescopes that measures solar vibrations from various locations around Earth. SOHO, the Solar and Heliospheric Observatory, makes similar measurements from space.
"This is an important discovery," says Dean Pesnell of NASA's Goddard Space Flight Center. "It shows how flows inside the sun are tied to the creation of sunspots and how jet streams can affect the timing of the solar cycle."
There is, however, much more to learn.
"We still don't understand exactly how jet streams trigger sunspot production," says Pesnell. "Nor do we fully understand how the jet streams themselves are generated."
To solve these mysteries, and others, NASA plans to launch the Solar Dynamics Observatory (SDO) later this year. SDO is equipped with sophisticated helioseismology sensors that will allow it to probe the solar interior better than ever before.
"The Helioseismic and Magnetic Imager (HMI) on SDO will improve our understanding of these jet streams and other internal flows by providing full disk images at ever-increasing depths in the sun," says Pesnell.
Continued tracking and study of solar jet streams could help researchers do something unprecedented--accurately predict the unfolding of future solar cycles.
Adapted from materials provided by http://science.nasa.gov/. Original article written by Dr. Tony Phillips.

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.

Lunar Reconnaissance Orbiter: NASA Returns To The Moon With First Lunar Launch In A Decade

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ScienceDaily (June 19, 2009) — NASA's Lunar Reconnaissance Orbiter launched at 5:32 p.m. EDT Thursday aboard an Atlas V rocket from Cape Canaveral Air Force Station in Florida. The satellite will relay more information about the lunar environment than any other previous mission to the moon.

The orbiter, known as LRO, separated from the Atlas V rocket carrying it and a companion mission, the Lunar Crater Observation and Sensing Satellite, or LCROSS, and immediately began powering up the components necessary to control the spacecraft. The flight operations team established communication with LRO and commanded the successful deployment of the solar array at 7:40 p.m. The operations team continues to check out the spacecraft subsystems and prepare for the first mid-course correction maneuver. NASA scientists expect to establish communications with LCROSS about four hours after launch, at approximately 9:30 p.m.
"This is a very important day for NASA," said Doug Cooke, associate administrator for NASA's Exploration Systems Mission Directorate in Washington, which designed and developed both the LRO and LCROSS missions. "We look forward to an extraordinary period of discovery at the moon and the information LRO will give us for future exploration missions."
The spacecraft will be placed in low polar orbit about 31 miles, or 50 kilometers, above the moon for a one year primary mission. LRO's instruments will help scientists compile high resolution three-dimensional maps of the lunar surface and also survey it at many spectral wavelengths. The satellite will explore the moon's deepest craters, exploring permanently sunlit and shadowed regions, and provide understanding of the effects of lunar radiation on humans.
"Our job is to perform reconnaissance of the moon's surface using a suite of seven powerful instruments," said Craig Tooley, LRO project manager at NASA's Goddard Space Flight Center in Greenbelt, Md. "NASA will use the data LRO collects to design the vehicles and systems for returning humans to the moon and selecting the landing sites that will be their destinations."
High resolution imagery from LRO's camera will help identify landing sites for future explorers and characterize the moon's topography and composition. The hydrogen concentrations at the moon's poles will be mapped in detail, pinpointing the locations of possible water ice. A miniaturized radar system will image the poles and test communication capabilities.
"During the 60 day commissioning period, we will turn on spacecraft components and science instruments," explained Cathy Peddie, LRO deputy project manager at Goddard. "All instruments will be turned on within two weeks of launch, and we should start seeing the moon in new and greater detail within the next month."
"We learned much about the moon from the Apollo program, but now it is time to return to the moon for intensive study, and we will do just that with LRO," said Richard Vondrak, LRO project scientist at Goddard.
All LRO initial data sets will be deposited in the Planetary Data System, a publicly accessible repository of planetary science information, within six months of launch.
Goddard built and manages LRO. LRO is a NASA mission with international participation from the Institute for Space Research in Moscow. Russia provides the neutron detector aboard the spacecraft.
The LRO mission is providing updates via @LRO_NASA on Twitter. To follow, visit:
http://www.twitter.com/lro_nasa
For more information about the LRO mission, visit:
http://www.nasa.gov/lro
Adapted from materials provided by NASA.

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.

Planet-forming Disk Discovered Orbiting Twin Suns

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ScienceDaily (June 11, 2009) — Astronomers have announced that a sequence of images collected with the Smithsonian's Submillimeter Array (SMA) clearly reveals the presence of a rotating molecular disk orbiting the young binary star system V4046 Sagittarii. The SMA images provide an unusually vivid snapshot of the process of formation of giant planets, comets, and Pluto-like bodies. The results also confirm that such objects may just as easily form around double stars as around single stars like our Sun.

These findings are being presented by UCLA graduate student David Rodriguez in a press conference at the American Astronomical Society meeting in Pasadena, Calif.
"It's a case of seeing is believing," says Joel Kastner of the Rochester (NY) Institute of Technology, the lead scientist on the study. "We had the first evidence for this rotating disk in radio telescope observations of V4046 Sagittarii that we made last summer. But at that point, all we had were molecular spectra, and there are different ways to interpret the spectra. Once we saw the image data from the SMA, there was no doubt that we have a rotating disk here."
Co-author David Wilner of the Harvard-Smithsonian Center for Astrophysics (CfA) adds, "This is strong evidence that planets can form around binary stars, which expands the number of places we can look for extrasolar planets. Somewhere in our galaxy, an alien world may enjoy double sunrises and double sunsets."
Wilner is one of the world's experts on radiointerferometry, the technique used in this study to form images with the SMA's multiple radio antennas. The other contributor to the SMA study of V4046 Sagittarii led by RIT's Kastner and UCLA's Rodriguez is Ben Zuckerman of UCLA.
According to Rodriguez, the images clearly demonstrate that the molecular disk orbiting the V4046 Sagittarii binary system extends from within the approximate radius of Neptune's orbit out to about 10 times that orbit. This region corresponds to the zone where the solar system's giant planets, as well as its Pluto-like Kuiper Belt objects, may have formed.
"We believe that V4046 Sagittarii provides one of the clearest examples yet discovered of a Keplerian, planet-forming disk orbiting a young star system," Wilner says. "This particular system is made that much more remarkable by the fact that it consists of a pair of solar-mass stars that are approximately 12 million years old and are separated by a mere 5 solar diameters."
"This could be the oldest known orbiting protoplanetary molecular disk. It shows that, at least for some stars, formation of Jovian-mass planets may continue well after a few million years, which astronomers have deduced is characteristic of the formation time for most such planets," Zuckerman says.
Findings of this study build on previous work published in the December 2008 issue of Astronomy and Astrophysics in which Kastner and his team first suggested that the case of V4046 Sagittarii illustrates well how planets may form easily around certain types of binary stars.
"We thought the molecular gas around these two stars almost literally represented 'smoking gun' evidence of recent or possibly ongoing 'giant' Jupiter-like planet formation around the binary star system," Kastner says. "The SMA images showing an orbiting disk certainly support that idea."
The evidence for a molecular disk orbiting these twin young suns in the constellation Sagittarius suggested to the scientists that many such binary systems should also host as-yet-undetected planets.
"The most successful technique used so far for the discovery of extrasolar planets - that of measurement of precision radial velocities - is exceedingly difficult for close binary stars such as V4046 Sagittarii. So these radio observations are probing a new region of discovery space for extrasolar planets," says Rodriguez.
"At a distance of only 240 light-years from the solar system, the V4046 Sagittarii binary is at least two times closer to Earth than almost all known planet-forming star systems, which gives us a good shot at imaging any planets that have already formed and are now orbiting the stars," he continues.
Kastner and collaborators had previously used the 30-meter radiotelescope operated by the Institut de Radio Astronomie Millimetrique (IRAM) to study radio molecular spectra emitted from the vicinity of the twin stars. The scientists used these data to identify the raw materials for planet formation around V4046 Sagittarii - carbon monoxide and hydrogen cyanide - in the noxious circumstellar gas cloud.
"In this case the stars are so close together, and the profile of the gas - in terms of the types of molecules that are there - is so much like the types of gaseous disks that we see around single stars, that we now have a direct link between planets forming around single stars and planets forming around double stars," Kastner says.
Adapted from materials provided by Harvard-Smithsonian Center for Astrophysics.

Search For ET Just Got Easier: Effective Way To Search Atmospheres Of Planets For Signs Of Life

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ScienceDaily (June 12, 2009) — Astronomers using the Science and Technology Facilities Council's (STFC) William Herschel Telescope (WHT) on La Palma have confirmed an effective way to search the atmospheres of planets for signs of life, vastly improving our chances of finding alien life outside our solar system.

The team from the Instituto de Astrofisica de Canarias (IAC) used the WHT and the Nordic Optical Telescope (NOT) to gather information about the chemical composition of the Earth's atmosphere from sunlight that has passed through it. The research is published June11 in Nature.
When a planet passes in front of its parent star, part of the starlight passes through the planet's atmosphere and contains information about the constituents of the atmosphere, providing vital information about the planet itself. This is called a transmission spectrum and even though astronomers can't use exactly the same method to look at the Earth's atmosphere, they were able to gain a spectrum of our planet by observing light reflected from the Moon towards the Earth during a lunar eclipse. This is the first time the transmission spectrum of the Earth has been measured.
The spectrum not only contained signs of life but these signs were unmistakably strong. It also contained unexpected molecular bands and the signature of the earth ionosphere.
Enric Palle, lead author of the paper, from the Instituto de Astrofisica de Canarias, said, "Now we know what the transmission spectrum of a inhabited planet looks like, we have a much better idea of how to find and recognize Earth like planets outside our solar system where life may be thriving. The information in this spectrum shows us that this is a very effective way to gather information about the biological processes that may be taking place on a planet."
Pilar Montañes-Rodriguez, from the Instituto de Astrofisica de Canarias, added, "Many discoveries of Earth-size planets are expected in the next decades and some will orbit in the habitable zone of their parent stars. Obtaining their atmospheric properties will be highly challenging; the greatest reward will happen when one of those planets shows a spectrum like that of our Earth."
The past two decades have witnessed the discovery of hundreds of exoplanets (planets beyond our solar system). Ambitious missions, ground and space based, are already being planned for the next decades, and the discovery of Earth-like planets is only a matter of time. Once these planets are found, techniques like transmission spectra will be invaluable to their further exploration.
Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council (STFC), said, "This new transmission spectrum is good news for future upcoming ground and space based missions dedicated to the search for life in the Universe. The UK is committed to cutting edge science and UK owned facilities like the WHT are helping to make many groundbreaking discoveries and expand our knowledge of the Universe. Not only do these results improve our knowledge of our own planet but we now have an effective way to search for life on the increasing number of exoplanets being found by astronomers."
The results on the WHT were achieved using LIRIS, a very efficient near-IR imager/spectrograph built and developed at IAC. LIRIS became a common-user instrument at the WHT as a result of the agreement signed by IAC to become a partner at ING in 2003.
Journal reference:
Enric Pallé, María Rosa Zapatero Osorio, Rafael Barrena, Pilar Montañés-Rodríguez & Eduardo L. Martín. Earth's transmission spectrum from lunar eclipse observations. Nature, 2009; 459 (7248): 814 DOI: 10.1038/nature08050
Adapted from materials provided by Science and Technology Facilities Council.