Time Space Science

Saturnian Moon Shows Evidence Of Ammonia

2009-08-06T08:12:00.001-07:00

Data collected during two close flybys of Saturn's moon Enceladus by NASA's Cassini spacecraft add more fuel to the fire about the Saturnian ice world containing sub-surface liquid water. The data collected by Cassini's Ion and Neutral Mass Spectrometer during Enceladus flybys in July and Oct. 2008, were released in the July 23 issue of the journal Nature.

"When Cassini flew through the plume erupting from Enceladus on October 8 of last year, our spectrometer was able to sniff out many complex chemicals, including organic ones, in the vapor and icy particles," said Hunter Waite, the Cassini Ion and Neutral Mass Spectrometer Lead Scientist from the Southwest Research Institute in San Antonio, Texas. "One of the chemicals definitively identified was ammonia."

On Earth, the presence of ammonia means the potential for sparkling clean floors and counter tops. In space, the presence of ammonia provides strong evidence for the existence of at least some liquid water.

How could ammonia equate to liquid water inside an ice-covered moon in one of the chillier neighborhoods of our solar system? As many a homeowner interested in keeping their abodes spick and span know, ammonia promptly dissolves in water. But what many people do not realize is that ammonia acts as antifreeze, keeping water liquid at lower temperatures than would otherwise be possible. With the presence of ammonia, water can exist in a liquid state to temperatures as low as 176 degrees Kelvin (-143 degrees Fahrenheit).

"Given that temperatures in excess of 180 Kelvin (-136 degrees Fahrenheit) have been measured near the fractures on Enceladus where the jets emanate, we think we have an excellent argument for a liquid water interior," said Waite.

Cassini discovered water vapor and particles spewing from Enceladus in 2005. Since then, scientists have been trying to determine if the plume originates from a liquid source inside the moon or is due to other causes.

"Ammonia is sort of a holy grail for icy volcanism," said William McKinnon, a scientist from Washington University in Saint Louis, Missouri. "This is the first time we've found it for sure on an icy satellite of a giant planet. It is probably everywhere in the Saturn system."

Just how much water is contained within Enceladus' icy interior is still up for debate. So far, Cassini has made five flybys of Enceladus, one of the chief targets for Cassini's extended mission. Two close flybys are scheduled for November of this year, and two more close flybys are scheduled for April and May or 2010. Data collected during these future flybys may help settle the debate.

"Where liquid water and organics exist, is there life?" asked Jonathan Lunine a Cassini scientist from the University of Arizona, Tucson. "Such is the case for Earth; what was found on Enceladus bolsters this moon's promise for containing potential habitable environments."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Cassini orbiter was designed, developed and assembled at JPL. JPL manages the mission for the Science Mission Directorate at NASA Headquarters in Washington.

http://www.jpl.nasa.gov/

Scientists Look Beyond Earth To Understand Auroras

2009-07-21T09:27:00.000-07:00

The eerie beauty of the northern and southern lights has evoked visions of the supernatural for centuries: foxes of fire whisking their tales, the fighting souls of dead warriors or ancestors dancing around a ceremonial fire.

The English poet Sir Walter Scott in 1805 conjured up otherworldly beings when he wrote, "He knew, by the streamers that shot so bright, That spirits were riding the northern light."

But it was a French scientist, not a poet, who named the sight after Roman gods. In 1621, Pierre Cassendi paired Aurora, goddess of dawn, with Boreas, god of the north wind, to christen the northern lights “aurora borealis.” Those centered above the South Pole are called aurora australis for “southern dawn.”

Even today, scientists and forecasters at NOAA’s Space Weather Prediction Center in Boulder, Colo., look beyond the Earth itself for the first step in a chain of events that ultimately paints brilliant hues across the night sky at opposite ends of the planet.

Anatomy of an Aurora

Deep within the Sun, 93 million miles away, roiling plasma rises and bursts through the solar atmosphere, sometimes thrusting highly charged protons and electrons our way. When this so-called solar wind arrives near Earth, it energizes protons and electrons trapped in the planet’s magnetic field.

These charged particles then travel down magnetic field lines, like beads slipping along a string, into Earth’s upper atmosphere near the poles. There the particles in turn excite atoms and molecules of oxygen, nitrogen, and other atmospheric gases. As these atoms relax back down into their normal state, they release the excess energy as visible light, forming an aurora oval loosely centered on the magnetic pole.

During an aurora, vivid arcs, curls, waves and bands of green, red, and sometimes blue dance across the sky for minutes or hours, peaking near midnight — all between 60 and 600 miles above the ground.

Many people think auroras are rare events, but there’s almost always an aurora of some size in the sky near the poles. Seeing one is another matter.

Auroras are most often visible in regions bordering the Arctic Circle: Canada, Alaska, northern Greenland, the Scandinavian coast, and Siberia. In the south, you need to be visiting Antarctica to see an aurora frequently. But the larger the solar storm reaching Earth’s upper atmosphere, the farther the aurora extends from the poles. Residents of New England or southern Chile might see an aurora every few years. If you live in Florida or Italy, you’d be lucky to see an aurora once in your lifetime.

How Space Weather Affects Us

One of the nation’s critical operations centers, NOAA’s Space Weather Prediction Center keeps a close eye on solar activity that precedes an aurora. When a major storm explodes on the sun, followed by a suddenly intensified solar wind heading toward Earth, the center alerts airlines, the military, the communications industry, power companies and the media that a storm is on its way.

Why do NOAA scientists care about this odd “weather” on the sun and in space? NOAA monitors solar storms because they can disrupt satellite functions, power grid operations, GPS signals, high-frequency communications used by airlines and the military, and other space-based technologies that we depend on. Solar radiation could also threaten astronauts’ safety if they happen to be outside the space shuttle as it zooms past.

Visit the Space Weather Prediction Center’s aurora Web site to view the current shape and size of the auroras around the two poles. If the auroras shown there are exceptionally large and you’re in a far northern or far southern latitude, look for those spirits hurtling across the midnight sky!

Tips on Seeing an Aurora

Best time of night: 10:00 p.m. to 2:00 a.m.
Best conditions: clear night with no moon and far from light pollution
Best season: mid-winter
Best phase of the solar cycle: maximum
Best years in the sun’s current cycle: 2012 to 2013
Best position on Earth: far northern or southern latitudes

http://www.noaa.gov/

Galaxies Coming Of Age In Cosmic Blobs

2009-07-01T03:06:00.000-07:00

The "coming of age" of galaxies and black holes has been pinpointed, thanks to new data from NASA's Chandra X-ray Observatory and other telescopes. This discovery helps resolve the true nature of gigantic blobs of gas observed around very young galaxies.

About a decade ago, astronomers discovered immense reservoirs of hydrogen gas -- which they named "blobs" – while conducting surveys of young distant galaxies. The blobs are glowing brightly in optical light, but the source of immense energy required to power this glow and the nature of these objects were unclear.

A long observation from Chandra has identified the source of this energy for the first time. The X-ray data show that a significant source of power within these colossal structures is from growing supermassive black holes partially obscured by dense layers of dust and gas. The fireworks of star formation in galaxies are also seen to play an important role, thanks to Spitzer Space Telescope and ground-based observations.

"For ten years the secrets of the blobs had been buried from view, but now we've uncovered their power source," said James Geach of Durham University in the United Kingdom, who led the study. "Now we can settle some important arguments about what role they played in the original construction of galaxies and black holes."

Galaxies are believed to form when gas flows inwards under the pull of gravity and cools by emitting radiation. This process should stop when the gas is heated by radiation and outflows from galaxies and their black holes. Blobs could be a sign of this first stage, or of the second.

Based on the new data and theoretical arguments, Geach and his colleagues show that heating of gas by growing supermassive black holes and bursts of star formation, rather than cooling of gas, most likely powers the blobs. The implication is that blobs represent a stage when the galaxies and black holes are just starting to switch off their rapid growth because of these heating processes. This is a crucial stage of the evolution of galaxies and black holes - known as "feedback" - and one that astronomers have long been trying to understand.

"We're seeing signs that the galaxies and black holes inside these blobs are coming of age and are now pushing back on the infalling gas to prevent further growth," said coauthor Bret Lehmer, also of Durham. "Massive galaxies must go through a stage like this or they would form too many stars and so end up ridiculously large by the present day."

Chandra and a collection of other telescopes including Spitzer have observed 29 blobs in one large field in the sky dubbed "SSA22." These blobs, which are several hundred thousand light years across, are seen when the Universe is only about two billion years old, or roughly 15% of its current age.

In five of these blobs, the Chandra data revealed the telltale signature of growing supermassive black holes - a point-like source with luminous X-ray emission. These giant black holes are thought to reside at the centers of most galaxies today, including our own. Another three of the blobs in this field show possible evidence for such black holes. Based on further observations, including Spitzer data, the research team was able to determine that several of these galaxies are also dominated by remarkable levels of star formation.

The radiation and powerful outflows from these black holes and bursts of star formation are, according to calculations, powerful enough to light up the hydrogen gas in the blobs they inhabit. In the cases where the signatures of these black holes were not detected, the blobs are generally fainter. The authors show that black holes bright enough to power these blobs would be too dim to be detected given the length of the Chandra observations.

Besides explaining the power source of the blobs, these results help explain their future. Under the heating scenario, the gas in the blobs will not cool down to form stars but will add to the hot gas found between galaxies. SSA22 itself could evolve into a massive galaxy cluster.

"In the beginning the blobs would have fed their galaxies, but what we see now are more like leftovers," said Geach. "This means we'll have to look even further back in time to catch galaxies and black holes in the act of forming from blobs."

These results will appear in the July 10 issue of 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.

http://chandra.harvard.edu/

Life On Other Planets

2009-06-18T03:23:00.000-07:00

A comprehensive review by leading scientists about our solar system which speculates on the possibility of life on other planets has been published.

Solar System Update brings together the work of 19 physicists, astronomers, and climatologists from Europe and the USA in 12 chapters on the sun, the main planets and comets.

The book, co-authored by Dr Philippe Blondel, of the University of Bath, highlights the many recent discoveries and in particular the amount of water, one of the essentials for life, found in the solar system.

Recent studies have revealed ice in craters on Mercury, the closest planet to the sun, and that liquid water may once have existed on the surface of Mars, and may still be there underground.

In addition, liquid water may exist on moons around Jupiter, in particular Europa, Ganymede and Callisto, underneath a surface of ice.

In his chapter The Habitability of Mars: Past and Present, Thomas McCollom, of the Center for Astrobiology at the University of Colorado, USA, says that though the temperatures on Mars, as low as minus 120 Centigrade, mean that water cannot exist on the surface, there may be a "planet-wide liquid aquifer at some depth in its crust." There is also geological evidence that water has flowed on the surface in the past.

"It seems increasingly apparent that habitable environments very likely exist on Mars today, and may have been considerably more diverse and abundant in the past," he writes.

In his chapter The Icy Moons of Jupiter, Richard Greenberg, of the Department of Planetary Sciences at the University of Arizona, USA, says: "There is an unusually strong motivation to continue to pursue studies of the icy satellites."

He says that three large moons of Jupiter "probably have liquid water layers, and one, Europa, almost certainly has an ocean just below the surface. Naturally liquid water raises the possibility of extraterrestrial life."

However, if the surface ice were very thick, this would cut the water below off from oxygen and sunlight which are important for most forms of life on Earth, and so might have prevented life from developing.

Dr Blondel, who works in the University of Bath's Department of Physics, took 18 months to edit the book, with his co-editor Dr John Mason.

"This book sets out how much water and ice there is in the solar system," said Dr Blondel. "This obviously has implications for our search for extra-terrestrial life.

"By understanding better how the climates of planets like Mars and Venus have evolved, we can understand more about climate change on Earth.

"For instance, the very hot and cloudy climate of Venus is likely to have developed after a runaway greenhouse effect, and the more we know about this the more we can understand some of the challenges caused by our climate change on Earth. "

http://www.bath.ac.uk/

Tiny Frozen Microbe May Hold Clues To Extraterrestrial Life

2009-06-18T03:21:00.000-07:00

A novel bacterium -- trapped more than three kilometres under glacial ice in Greenland for over 120,000 years -- may hold clues as to what life forms might exist on other planets.

Dr Jennifer Loveland-Curtze and a team of scientists from Pennsylvania State University report finding the novel microbe, which they have called Herminiimonas glaciei, in the current issue of the International Journal of Systematic and Evolutionary Microbiology. The team showed great patience in coaxing the dormant microbe back to life; first incubating their samples at 2˚C for seven months and then at 5˚C for a further four and a half months, after which colonies of very small purple-brown bacteria were seen.

H. glaciei is small even by bacterial standards – it is 10 to 50 times smaller than E. coli. Its small size probably helped it to survive in the liquid veins among ice crystals and the thin liquid film on their surfaces. Small cell size is considered to be advantageous for more efficient nutrient uptake, protection against predators and occupation of micro-niches and it has been shown that ultramicrobacteria are dominant in many soil and marine environments.

Most life on our planet has always consisted of microorganisms, so it is reasonable to consider that this might be true on other planets as well. Studying microorganisms living under extreme conditions on Earth may provide insight into what sorts of life forms could survive elsewhere in the solar system.

"These extremely cold environments are the best analogues of possible extraterrestrial habitats", said Dr Loveland-Curtze, "The exceptionally low temperatures can preserve cells and nucleic acids for even millions of years. H. glaciei is one of just a handful of officially described ultra-small species and the only one so far from the Greenland ice sheet; studying these bacteria can provide insights into how cells can survive and even grow under extremely harsh conditions, such as temperatures down to -56˚C, little oxygen, low nutrients, high pressure and limited space."

"H. glaciei isn't a pathogen and is not harmful to humans", Dr Loveland-Curtze added, "but it can pass through a 0.2 micron filter, which is the filter pore size commonly used in sterilization of fluids in laboratories and hospitals. If there are other ultra-small bacteria that are pathogens, then they could be present in solutions presumed to be sterile. In a clear solution very tiny cells might grow but not create the density sufficient to make the solution cloudy."

http://www.sgm.ac.uk/

Mars May Still Be A Living Planet

2009-06-18T03:17:00.001-07:00

A team of NASA and university scientists has achieved the first definitive detection of methane in the atmosphere of Mars. This discovery indicates the planet is either biologically or geologically active.

The team found methane in the Martian atmosphere by carefully observing the planet throughout several Mars years with NASA's Infrared Telescope Facility and the W.M. Keck telescope, both at Mauna Kea, Hawaii. The team used spectrometers on the telescopes to spread the light into its component colors, as a prism separates white light into a rainbow. The team detected three spectral features called absorption lines that together are a definitive signature of methane.

"Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas," said Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md. "At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif." Mumma is lead author of a paper describing this research that will appear in Science Express on Thursday.

Methane, four atoms of hydrogen bound to a carbon atom, is the main component of natural gas on Earth. Astrobiologists are interested in these data because organisms release much of Earth's methane as they digest nutrients. However, other purely geological processes, like oxidation of iron, also release methane.

"Right now, we do not have enough information to tell whether biology or geology -- or both -- is producing the methane on Mars," Mumma said. "But it does tell us the planet is still alive, at least in a geologic sense. It is as if Mars is challenging us, saying, 'hey, find out what this means.' "

If microscopic Martian life is producing the methane, it likely resides far below the surface where it is warm enough for liquid water to exist. Liquid water is necessary for all known forms of life, as are energy sources and a supply of carbon.

"On Earth, microorganisms thrive about 1.2 to 1.9 miles beneath the Witwatersrand basin of South Africa, where natural radioactivity splits water molecules into molecular hydrogen and oxygen," Mumma said. "The organisms use the hydrogen for energy. It might be possible for similar organisms to survive for billions of years below the permafrost layer on Mars, where water is liquid, radiation supplies energy, and carbon dioxide provides carbon. Gases, like methane, accumulated in such underground zones might be released into the atmosphere if pores or fissures open during the warm seasons, connecting the deep zones to the atmosphere at crater walls or canyons."

It is possible a geologic process produced the Martian methane, either now or eons ago. On Earth, the conversion of iron oxide into the serpentine group of minerals creates methane, and on Mars this process could proceed using water, carbon dioxide and the planet's internal heat. Although there is no evidence of active volcanism on Mars today, ancient methane trapped in ice cages called clathrates might be released now.

"We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane," said co-author Geronimo Villanueva of the Catholic University of America in Washington. "The plumes were emitted during the warmer seasons, spring and summer, perhaps because ice blocking cracks and fissures vaporized, allowing methane to seep into the Martian air."

According to the team, the plumes were seen over areas that show evidence of ancient ground ice or flowing water. Plumes appeared over the Martian northern hemisphere regions such as east of Arabia Terra, the Nili Fossae region, and the south-east quadrant of Syrtis Major, an ancient volcano about 745 miles across.

One method to test whether life produced this methane is by measuring isotope ratios. Isotopes of an element have slightly different chemical properties, and life prefers to use the lighter isotopes. A chemical called deuterium is a heavier version of hydrogen. Methane and water released on Mars should show distinctive ratios for isotopes of hydrogen and carbon if life was responsible for methane production. It will take future missions, like NASA's Mars Science Laboratory, to discover the origin of the Martian methane.

The research was funded by the Planetary Astronomy Program at NASA Headquarters in Washington and the Astrobiology Institute at NASA's Ames Research Center in Moffett Field, Calif. The University of Hawaii manages NASA's Infrared Telescope Facility.

http://www.nasa.gov/centers/goddard/home/index.html

Definitive Evidence For Ancient Lake On Mars

2009-06-18T03:16:00.001-07:00

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."

http://www.colorado.edu/

Scientists Gear Up For Mercury Mission Flyby Of Venus

2009-06-05T06:19:00.001-07:00

University of Colorado at Boulder researchers will scan Venus during a spacecraft flyby this week using an $8.7 million instrument they designed and built for NASA's MESSENGER Mission, launched in 2004 and speeding toward Mercury.

Built by CU-Boulder's Laboratory for Atmospheric and Space Physics, the instrument will make measurements of the thick clouds and shrouded surface of Venus during the June 5th flyby, said LASP Senior Research Associate William McClintock, a mission co-investigator who led the CU-Boulder instrument development team. Known as the Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, the instrument will compare the atmosphere of Venus with data from other spacecraft that have visited the planet in the past four decades.

"This is our first opportunity for a close flyby of a solar system object with MESSENGER, and we should be able to tell if the atmosphere of Venus has been changing in recent years, " said McClintock. "As importantly, we are using Venus as a test case to learn more about our instrument performance in preparation for the spacecraft's ultimate destination of Mercury."

Carrying seven instruments, MESSENGER will be the first spacecraft ever to orbit Mercury and the first to return data from the hot, rocky planet in more than 30 years. The circuitous, 4.9 billion mile journey to Mercury, which requires more than seven years and 13 loops around the sun, is using the gravity of Venus during its flyby this week to guide it closer to Mercury's orbit.

MESSENGER will make its first flyby of Mercury in January 2008, zipping by it again at a top speed of 141,000 miles per hour in October 2008 before flying by a third time in September 2009 and finally settling into orbit in March 2011. "This is a mission that requires some patience," said Mark Lankton, LASP's program manager for the MASCS instrument. "We are anticipating a brief symphony of action at Venus, and we have a lot of data to take in a hurry."

Dozens of CU-Boulder undergraduate and graduate students will be involved in data analysis from MESSENGER in the coming years, said Lankton.

MASCS's ultraviolet and visible spectrometer will be looking at the cloud composition of Venus. While the surface of Venus is hot enough to melt lead and its atmosphere is filled with noxious carbon dioxide gases and acid rain, Earth and Venus were virtual twins at birth, scientists believe.

The miniaturized MASCS instrument, which took more than three years to develop, weighs less than seven pounds and was built to last, said McClintock. "Many space instruments have a lifetime of only three to four years," he said. "But we knew we had to make this one robust enough to work for more than a decade under harsh conditions."

The MESSENGER spacecraft is about the size of a small economy car and is equipped with a semi-cylindrical thermal shade to protect it from the sun. More than half of the weight of the 1.2-ton spacecraft consists of propellant and helium. "We like to call it the little spacecraft that could," said McClintock.

"This event at Venus will be a very good tune-up for our first flyby of Mercury next January," said LASP Director Daniel Baker, also a co-investigator on the MESSENGER team. "The first encounter with Mercury will be extremely valuable, as it will essentially double the amount of information we now have about the planet."

A space physicist, Baker is interested in the magnetic field of Mercury and its interaction with the solar wind, including "substorms" associated with Mercury's magnetic field that occur in the planet's vicinity. Understanding Mercury's surface, tenuous atmosphere and magnetic field are the keys to understanding the evolution of the inner solar system, he said.

Mercury was visited only once before by a spacecraft, in 1974 and 1975, when NASA's Mariner 10 spacecraft made three flybys and mapped roughly 45 percent of the planet's rocky surface at the time.

MASCS will probe the mineral composition of Mercury's surface, the distribution of gases in its tenuous atmosphere and the workings of a giant, comet-like sodium gas cloud enveloping the planet, said McClintock. The researchers also hope to determine if Mercury ever had volcanoes on its surface and if the permanently shadowed craters at Mercury's poles contain water-ice.

MESSENGER is equipped with a large sunshield and heat-resistant ceramic fabric because Mercury is about two-thirds of the way nearer to the sun than Earth and is bombarded with 10 times the solar radiation. Sandwiched by the sun and Mercury -- which has daytime temperatures of about 800 degrees Fahrenheit -- the spacecraft will "essentially be on a huge rotisserie," said Baker.

Magnesium Detected In MESSENGER Flyby Of Mercury

2009-06-05T06:17:00.000-07:00

Scientists had suspected magnesium would be present, but were surprised at its distribution and abundance, said Senior Research Associate William McClintock of CU-Boulder's Laboratory for Atmospheric and Space Physics. The discovery in the planet's wispy atmosphere, known as its exosphere, is one more clue to the mystery of the creation of the rocky, bizarre planet that resides closest to the sun.

"Detecting magnesium was not too surprising, but seeing it in the amounts and distribution we recorded was unexpected," said McClintock, a MESSENGER co- investigator who led the development of CU-Boulder's Mercury Atmospheric and Surface Composition Spectrometer, or MASCS. "This is an example of the kind of individual discoveries that the MESSENGER team will piece together to give us a new picture of how the planet formed and evolved."

A paper on the subject by McClintock is being published in the May 1 issue of Science. Co-authors on the paper are Ronald Vervack and Noam Izenberg of Johns Hopkins University, E. Todd Bradley of the University of Central Florida, Rosemary Killen, Nelly Mouand and Mathew Burger of the University of Maryland, Ann Sprague of the University of Arizona and Sean Solomon of the Carnegie Institution of Washington, D.C. Solomon is the MESSENGER principal investigator.

The CU-Boulder instrument also measured other elements in the exosphere during the Oct. 6 flyby, including calcium and sodium. "Since calcium and magnesium are chemically similar, we might expect them to have a similar distribution in Mercury's exosphere," McClintock said. "But they don't, and we don't yet understand why."

McClintock said materials escaping from Mercury's surface are accelerated by solar radiation pressure to form a gigantic tail of atoms flowing away from the sun. Their abundances change, however, depending on the season as well as changes in magnetic field orientation and solar wind intensity.

The LASP team suspects that other metallic elements from the surface -- including aluminum, iron and silicon -- also are present in the exosphere. The metals permeated the solar nebula when it was coalescing some 4.5 billion years ago, shaping the planets, said McClintock.

Traveling at 4.2 miles per second, the spacecraft dipped within 124 miles of Mercury Oct. 6 and imaged about 30 percent of the surface never before seen by spacecraft. Launched in August 2004, MESSENGER will make the last of three Mercury passes in September 2009 before finally settling into orbit in 2011. The circuitous, 4.9 billion-mile-journey to Mercury requires more than six years and 15 loops around the sun to guide it closer to Mercury's orbit.

The desk-sized MESSENGER spacecraft is carrying seven instruments -- a camera, a magnetometer, an altimeter and four spectrometers. McClintock led the development of MASCS, which was miniaturized to weigh less than seven pounds for the arduous journey. Data from MASCS obtained during the first flyby in January 2008 provided LASP researchers with evidence that about 10 percent of the sodium atoms ejected from Mercury's hot surface during the daytime were accelerated into a 25,000-mile-long sodium tail trailing the planet, according to McClintock.

MESSENGER took data and images from Mercury for about 90 minutes on Oct. 6, when LASP turned on a detector in MASCS for its first look at Mercury's surface in the far ultraviolet portion of the light spectrum, said McClintock.

LASP Director Daniel Baker, also a co-investigator on the MESSENGER mission, is using data from the mission to study Mercury's magnetic field and its interaction with the solar wind. Mark Lankton is the LASP program manager for the MASCS instrument. Dozens of undergraduates and graduate students will be involved in analyzing data over the next several years as information and images pour back to Earth from MESSENGER.

http://www.colorado.edu/

Mining For Molecules In The Milky Way

2009-06-05T06:12:00.000-07:00

Scientists are using the giant Robert C. Byrd Green Bank Telescope (GBT) to go prospecting in a rich molecular cloud in our Milky Way Galaxy. They seek to discover new, complex molecules in interstellar space that may be precursors to life.

"Clouds like this one are the raw material for new stars and planets. We know that complex chemistry builds prebiotic molecules in such clouds long before the stars and planets are formed. There is a good chance that some of these interstellar molecules may find their way to the surface of young planets such as the early Earth, and provide a head start for the chemistry of life. For the first time, we now have the capability to make a very thorough and methodical search to find all the chemicals in the clouds," said Anthony Remijan, of the National Radio Astronomy Observatory (NRAO).

In the past three years, Remijan and his colleagues have used the GBT to discover ten new interstellar molecules, a feat unequalled in such a short time by any other team or telescope.

The scientists discovered those molecules by looking specifically for them. However, they now are changing their strategy and casting a wide net designed to find whatever molecules are present, without knowing in advance what they'll find. In addition, they are making their data available freely to other scientists, in hopes of speeding the discovery process. The research team presented its plan to the American Astronomical Society's meeting in St. Louis, MO.

As molecules rotate and vibrate, they emit radio waves at specific frequencies. Each molecule has a unique pattern of such frequencies, called spectral lines, that constitutes a "fingerprint" identifying that molecule. Laboratory tests can determine the pattern of spectral lines that identifies a specific molecule.

Most past discoveries came from identifying a molecule's pattern in the laboratory, then searching with a radio telescope for that set of spectral lines in a region of sky. So far, more than 140 different molecules have been found that way in interstellar space.

The new study reverses the process. The astronomers will use the GBT to study a cloud of gas and dust in detail, finding all the spectral lines first, then later trying to match them up to molecular patterns using data-mining software.

The astronomers will make a thorough survey of the interstellar cloud in the wide range of radio frequencies between 300 MHz to 50 GHz. This technique, they said, will allow them to discover molecules that would elude more narrow-range observations.

"This strategy wasn't possible at frequencies between 300 MHz and 50 GHz before the GBT. That telescope's tremendous capabilities enable us to open a whole new era of astrochemistry," said Jan M. Hollis, of NASA's Goddard Space Flight Center.

"Based on earlier studies, there are a number of complex, prebiotic molecules that we think are present in such clouds, but only this wide-net approach with the GBT will capture the evidence we need to discover them," Remijan said.

"Complex organic molecules formed in interstellar space are undoubtedly the fundamental building blocks of astrobiology. The complete inventory of such molecules in this cloud will produce a tremendous advance in our understanding of the physical conditions in that cloud and of the first chemical steps toward life," said Phil Jewell, of the NRAO.

As the survey with the GBT continues, the research team plans to release their data to the scientific community. In addition, they are providing software that will allow other scientists to efficiently "mine" the data for the telltale evidence of new molecules.

"There is a wealth of laboratory data now available about the radio fingerprints of many molecules. Data-mining software will make it possible to efficiently match up the spectral lines seen in the laboratory with ones we observe in the interstellar clouds," said Frank Lovas of the National Institute for Standards and Technology.

The scientists are observing Sagittarius B2(N), a cloud near the center of our Galaxy, some 25,000 light-years from Earth, Numerous molecules have been discovered in that cloud in the past.

http://www.nrao.edu/

Astronomer To Search Space For Precursors Of Life

2009-06-05T06:10:00.000-07:00

Many of the organic molecules that make up life on Earth have also been found in space. A University of Michigan astronomer will use the Herschel Space Observatory to study these chemical compounds in new detail in the warm clouds of gas and dust around young stars.
They hope to gain insights into how organic molecules form in space, and possibly, how life formed on Earth.

"The chemistry of space makes molecules that are the precursors of life. It's possible that the Earth didn't have to make these things on its own, but that they were provided from space," said Ted Bergin, an associate professor in the Department of Astronomy.

Bergin is a co-investigator on the Heterodyne Instrument for the Infrared aboard Herschel and a principal investigator on one of its key observing programs. Herschel, a European Space Agency mission with NASA participation, is scheduled to launch May 6. An orbiting telescope that will unlock new wavelengths on the electromagnetic spectrum, it will allow astronomers to observe at the far-infrared wavelengths where organic molecules and water emit their chemical signatures.

"We'll be studying the full extent of chemistry in space and we hope to learn what types of organics are out there as a function of their distance from a star," Bergin said. "And we want to understand the chemical machinery that led to the formation of these organics."

Meteorites flecked with amino acids, which make proteins, have fallen to Earth from space. In faraway galaxies and stellar nurseries, astronomers have detected complex organic sugar and hydrocarbon molecules that are key components in chlorophyll in plants and RNA. Bergin expects to detect tens if not hundreds of these kinds of compounds---some of which have never been found before outside the Earth.

He is also involved in a Herschel project to look for water molecules in space. Traces of water in warm clouds of gas and dust around young stars could hold clues to how water forms and behaves in space, and how this elixir of life came to be so abundant on Earth. Scientists believe water got to Earth in a similar way as organic molecules.

"Most of the water in the solar system is not where we are, but further out in the solar system," Bergin said. "Most theories suggest that the Earth formed dry and impacts from asteroids or other objects provided the water here."

http://www.umich.edu/

Titan's Surface Organics Surpass Oil Reserves On Earth

2009-06-04T00:29:00.000-07:00

Saturn's orange moon Titan has hundreds of times more liquid hydrocarbons than all the known oil and natural gas reserves on Earth, according to new data from NASA's Cassini spacecraft. The hydrocarbons rain from the sky, collecting in vast deposits that form lakes and dunes.
The new findings from the study led by Ralph Lorenz, Cassini radar team member from the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., are reported in the Jan. 29 issue of the Geophysical Research Letters.

"Titan is just covered in carbon-bearing material -- it's a giant factory of organic chemicals," said Lorenz. "This vast carbon inventory is an important window into the geology and climate history of Titan."

At a balmy minus 179 degrees Celsius (minus 290 degrees Fahrenheit), Titan is a far cry from Earth. Instead of water, liquid hydrocarbons in the form of methane and ethane are present on the moon's surface, and tholins probably make up its dunes. The term "tholins"was coined by Carl Sagan in 1979 to describe the complex organic molecules at the heart of prebiotic chemistry.

Cassini has mapped about 20 percent of Titan's surface with radar. Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earth's oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earth's coal reserves.

Proven reserves of natural gas on Earth total 130 billion tons, enough to provide 300 times the amount of energy the entire United States uses annually for residential heating, cooling and lighting. Dozens of Titan's lakes individually have the equivalent of at least this much energy in the form of methane and ethane.

"This global estimate is based mostly on views of the lakes in the northern polar regions. We have assumed the south might be similar, but we really don't yet know how much liquid is there," said Lorenz. Cassini's radar has observed the south polar region only once, and only two small lakes were visible. Future observations of that area are planned during Cassini's proposed extended mission.

Scientists estimated Titan's lake depth by making some general assumptions based on lakes on Earth. They took the average area and depth of lakes on Earth, taking into account the nearby surroundings, like mountains. On Earth, the lake depth is often 10 times less than the height of nearby terrain.

"We also know that some lakes are more than 10 meters or so deep because they appear literally pitch-black to the radar. If they were shallow we'd see the bottom, and we don't," said Lorenz.

The question of how much liquid is on the surface is an important one because methane is a strong greenhouse gas on Titan as well as on Earth, but there is much more of it on Titan. If all the observed liquid on Titan is methane, it would only last a few million years, because as methane escapes into Titan's atmosphere, it breaks down and escapes into space. If the methane were to run out, Titan could become much colder. Scientists believe that methane might be supplied to the atmosphere by venting from the interior in cryovolcanic eruptions. If so, the amount of methane, and the temperature on Titan, may have fluctuated dramatically in Titan's past.

"We are carbon-based life, and understanding how far along the chain of complexity towards life that chemistry can go in an environment like Titan will be important in understanding the origins of life throughout the universe," added Lorenz.

Cassini's next radar flyby of Titan is on Feb. 22, when the radar instrument will observe the Huygens probe landing site.

Seas Discovered On Saturn's Moon Titan

2009-06-04T00:27:00.000-07:00

Instruments on NASA's Cassini spacecraft have found evidence for seas, likely filled with liquid methane or ethane, in the high northern latitudes of Saturn's moon Titan. One such feature is larger than any of the Great Lakes of North America and is about the same size as several seas on Earth.

Cassini's radar instrument imaged several very dark features near Titan's north pole. Much larger than similar features seen before on Titan, the largest dark feature measures at least 100,000 square kilometers (39,000 square miles). Since the radar has caught only a portion of each of these features, only their minimum size is known. Titan is the second largest moon in the solar system and is about 50 percent larger than Earth's moon.

"We've long hypothesized about oceans on Titan and now with multiple instruments we have a first indication of seas that dwarf the lakes seen previously," said Dr. Jonathan Lunine, Cassini interdisciplinary scientist at the University of Arizona, Tucson.

While there is no definitive proof yet that these seas contain liquid, their shape, their dark appearance in radar that indicates smoothness, and their other properties point to the presence of liquids. The liquids are probably a combination of methane and ethane, given the conditions on Titan and the abundance of methane and ethane gases and clouds in Titan's atmosphere.

Cassini's visual and infrared mapping spectrometer also captured a view of the region, and the team is working to determine the composition of the material contained within these features to test the hypothesis that they are liquid-filled.

The imaging cameras, which provide a global view of Titan, have imaged a much larger, irregular dark feature. The northern end of their image corresponds to one of the radar-imaged seas. The dark area stretches for more than 1,000 kilometers (620 miles) in the image, down to 55 degrees north latitude. If the entire dark area is liquid-filled, it would be only slightly smaller than Earth's Caspian Sea. The radar data show details at the northern end of the dark feature similar to those seen in earlier radar observations of much smaller, liquid-filled lakes. However, to determine if the entire dark feature is a liquid-filled basin will require investigation through additional radar flyovers later in the mission.

he presence of these seas reinforces current thinking that Titan's surface must be re-supplying methane to its atmosphere, the original motivation almost a quarter century ago for the theoretical speculation of a global ocean on Titan.

Cassini's instruments are peeling back the haze that shrouds Titan, showing high northern latitudes dotted with seas hundreds of miles across, and hundreds of smaller lakes that vary from several to tens of miles.

Due to the new discoveries, team members are re-pointing Cassini's radar instrument during a May flyby so it can pass directly over the dark areas imaged by the cameras.

http://www.nasa.gov/

Saturn's Moon Titan Is Tropical In Nature

2009-06-04T00:26:00.000-07:00

If space travelers ever visit Saturn's largest moon, they will find a tropical world where temperatures plunge to minus 274 degrees Fahrenheit, methane rains from the sky and dunes of ice or tar cover the planet's most arid regions. These conditions reflect a cold mirror image of Earth's tropical climate, according to scientists at the University of Chicago.

"You have all these things that are analogous to Earth. At the same time, it's foreign and unfamiliar," said Ray Pierrehumbert, the Louis Block Professor in Geophysical Sciences at Chicago.

Titan, one of Saturn's 60 moons, is the only moon in the solar system large enough to support an atmosphere. Pierrehumbert and Jonathan Mitchell, who recently completed his Ph.D. in Astronomy & Astrophysics at Chicago, have been comparing observations of Titan collected by the Cassini space probe and the Hubble Space Telescope with their own computer simulations of the moon's atmosphere.

Their study of the dynamics behind Titan's methane clouds have appeared in the Proceedings of the National Academy of Sciences. Their continuing research on Titan's climate focuses on the moon's deserts.

"One of the things that attracts me about Titan is that it has a lot of the same circulation features as Earth, but done with completely different substances that work at different temperatures," Pierrehumbert said. On Earth, for example, water forms liquid and is relatively active as a vapor in the atmosphere. But on Titan, water is a rock.

"It's not more volatile on Titan than sand is on Earth."

Methane-natural gas-assumes an Earthlike role of water on Titan. It exists in enough abundance to condense into rain and form puddles on the surface within the range of temperatures that occur on Titan.

"The ironic thing on Titan is that although it's much colder than Earth, it actually acts like a super-hot Earth rather than a snowball Earth, because at Titan temperatures, methane is more volatile than water vapor is at Earth temperatures," Pierrehumbert said.

Pierrehumbert and Mitchell even go so far as to call Titan's climate tropical, even though it sounds odd for a moon that orbits Saturn more than nine times farther from the sun than Earth. Along with the behavior of methane, Titan's slow rotation rate also contributes to its tropical nature. Earth's tropical weather systems extend only to plus or minus 30 degrees of latitude from the equator. But on Titan, which rotates only once every 16 days, "the tropical weather system extends to the entire planet," Pierrehumbert said.

Titan's tropical nature means that scientists can observe the behavior of its clouds using theories they've relied upon to understand Earth's tropics, Mitchell noted.Titan's atmosphere produces an updraft where surface winds converge. This updraft lifts evaporated methane up to cooler temperatures and lower pressures, where much of it condenses and forms clouds.

"This is a well-known feature on Earth called an ITCZ, the inter-tropical convergence zone," Mitchell said. Earth's oceans help confine the ITCZ to the lowest latitudes. But in some scenarios for oceanless Titan, the ITCZ in Mitchell's computer simulations wanders in latitude almost from one pole to the other. Titan's clouds should also follow the ITCZ.

Titan's orange atmospheric haze complicates efforts to observe the moon's clouds. "This haze shrouds the entire surface," Mitchell said. "It pretty much blocks all visible light from reaching us from the surface or from the lower atmosphere."

Nevertheless, infrared observations via two narrow frequency bands have recently revealed that clouds are currently confined to the moon's southern hemisphere, which is just now emerging from its summer season.

"There should be a very large seasonality in these cloud features," Mitchell said. "Cassini and other instruments might be able to tell us about that in the next seven to 10 years or so, as the seasons progress."

Mitchell and Pierrehumbert's next paper will describe how oscillations in Titan's atmospheric circulation dry out the moon's midsection. Over the course of a year, Mitchell explained, "this oscillation in the atmosphere tends to transport moisture, or evaporated methane, out of the low latitudes and then deposit it at mid and high latitude in the form of rainfall. This is interesting, because recent Cassini observations of the surface suggest that the low latitudes are very dry."

Cassini images show dunes of ice or tar covering these low-latitude regions that correspond to the tropics on Earth. When ultraviolet light from the sun interacts with methane high in Titan's atmosphere, it creates byproducts such as ethane and hydrogen.

These byproducts become linked to chains of hydrocarbon molecules that create Titan's orange haze. When these molecules coalesce into large particles, they settle out as a tar-like rain.

"Titan is like a big petrochemical plant," Pierrehumbert said. "Although this is all happening at a much lower temperature than in a petroleum refinery, the basic processes going on there are very closely allied to what people do when they make fuel."

http://www.uchicago.edu/

Saturn's Moon Titan

2009-06-04T00:24:00.000-07:00

Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion.
Their forecast for Titan's early autumn -- warm and wetter.

Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while fall is approaching.

"Titan's clouds don't move with the seasons exactly as we expected," said Sebastien Rodriguez of the University of Paris Diderot, in collaboration with Cassini visual and infrared mapping spectrometer team members at the University of Nantes, France. "We see lots of clouds during the summer in the southern hemisphere, and this summer weather seems to last into the early fall. It looks like Indian summer on Earth, even if the mechanisms are radically different on Titan from those on Earth. Titan may then experience a warmer and wetter early autumn than forecasted by the models."

On Earth, abnormally warm, dry weather periods in late autumn occur when low-pressure systems are blocked in the winter hemisphere. By contrast, scientists think the sluggishness of temperature changes at the surface and low atmosphere on Titan may be responsible for its unexpected warm and wet, hence cloudy, late summer.

As summer changes to fall at the equinox in August 2009, Titan's clouds are expected to disappear altogether. But, circulation models of Titan's weather and climate predict that clouds at the southern latitudes don't wait for the equinox and should have already faded out since 2005. However, Cassini was still able to see clouds at these places late in 2007, and some of them are particularly active at mid-latitudes and the equator.

Titan is the only moon in our solar system with a substantial atmosphere, and its climate shares Earth-like characteristics. Titan's dense, nitrogen-methane atmosphere responds much more slowly than Earth's atmosphere, as it receives about 100 times less sunlight because it is 10 times farther from the sun. Seasons on Titan last more than seven Earth years.

Scientists will continue to observe the long-term changes during Cassini's extended mission, which runs until the fall of 2010. Cassini is set to fly by Titan on May 6.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona.

http://www.jpl.nasa.gov/

How The Early Universe Got Dusty Remains A Mystery

2009-05-25T04:15:00.001-07:00

Astronomers who think they know how the very early universe came to have so much interstellar dust need to think again, according to new results from the Spitzer Space Telescope.

In the last few years, observers have discovered huge quantities of interstellar dust near the most distant quasars in the very young universe, only 700 million years after the cosmos was born in the Big Bang.

"And that becomes a big question," said Oliver Krause of the University of Arizona Steward Observatory in Tucson and the Max Planck Institute for Astronomy in Heidelberg. "How could all of this dust have formed so quickly?"

Astronomers know two processes that form the dust, Krause said. One, old sun-like stars near death generate dust. Two, infrared space missions have revealed the dust is produced in supernovae explosions.

"The first process takes several billion years," Krause noted. "Supernovae explosions, by contrast, produce dust in much less time, only about 10 million years."

So when astronomers reported detecting submillimeter emission from massive amounts of cold interstellar dust in the supernova remnant Cassiopeia A last year, some considered the mystery solved. Type II supernovae like 'Cas A' likely produced the interstellar dust in the very early universe, they concluded. (Type II supernovae come from massive stars that blow apart in huge explosions after their cores collapse.)

Krause and colleagues from UA's Steward Observatory and the Max Planck institute in Heidelberg have now discovered that the detected submillimeter emission comes not from the Cas A remnant itself but from the molecular cloud complex known to exist along the line of sight between Earth and Cas A. They report the work in the Dec. 2 issue of Nature.

Cas A is the youngest known supernova remnant in our Milky Way. It is about 11,000 light years away, behind the Perseus spiral arm clouds that are roughly 9,800 light years away. Krause suspects that the Perseus clouds explain why late 17th century astronomers didn't report observing the brilliant Cas A outburst around A.D. 1680. Cas A is so close to Earth that the supernova should have been the brightest stellar object in the sky, but dust in the Perseus clouds eclipsed the view.

The Arizona and German team mapped Cas A at 160-micron wavelengths using the ultra-heat-sensitive Multiband Imaging Photometer (MIPS) aboard the Spitzer Space Telescope. These long wavelengths are the most sensitive to cold interstellar dust emission. They then compared the results with maps of interstellar gas previously made with radio telescopes. They found that the dust in these interstellar clouds account for virtually all the emission at 160 microns from the direction of Cas A.

Minus the emission from this dust, there is no evidence for large amounts of cold dust in Cas A, the team concludes.

"Astronomers will have to go on searching for the source of the dust in the early universe," UA Steward Observatory astronomer and Regents' Professor George Rieke said. Rieke is principal investigator for the Spitzer Space Telescope's MIPS instrument and a co-author of the Nature paper.

"Solving this riddle will show astronomers where and how the first stars formed, or perhaps indicate there is some non-stellar process that can produce large amounts of dust," Rieke said. "Either way, (finding the source of the dust) will reveal what went on at the formative stage for stars and galaxies, an epoch that is nearly unobserved in any other way."

Authors of the Nature article, "No cold dust within the supernova remnant Cassiopeia A," are Oliver Krause, Stephan M. Birkmann, George H. Rieke, Dietrich Lemke, Ulrich Klaas, Dean C. Hines and Karl D. Gordon.

Birkmann, Lemke and Klaas are with the Max Planck Institute for Astronomy in Heidelberg. Krause, Rieke, and Gordon are with the University of Arizona Steward Observatory. Hines is with the Space Science Institute in Boulder, Colo.

The Spitzer Space Telescope is managed for NASA by the Jet Propulsion Laboratory in Pasadena, Calif.

Colors Of Quasars Reveal Dusty Universe

2009-05-25T04:14:00.000-07:00

The vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like "dust" particles that dim the light from distant objects and subtly change their colors, according to a team of astronomers from the Sloan Digital Sky Survey (SDSS-II).

"Galaxies contain lots of dust, most of it formed in the outer regions of dying stars," said team leader Brice Ménard of the Canadian Institute for Theoretical Astrophysics. "The surprise is that we are seeing dust hundreds of thousands of light-years outside of the galaxies, in intergalactic space."

To discover this intergalactic dust, the team analyzed the colors of distant quasars whose light passes in the vicinity of foreground galaxies on its way to the Earth.

Dust grains block blue light more effectively than red light, explained astronomer Ryan Scranton of the University of California, Davis, another member of the discovery team. "We see this when the sun sets: light rays pass through a thicker layer of the atmosphere, absorbing more and more blue light, causing the sun to appear reddened. We find similar reddening of quasars from intergalactic dust, and this reddening extends up to ten times beyond the apparent edges of the galaxies themselves."

The team analyzed the colors of about 100,000 distant quasars located behind 20 million galaxies, using images from SDSS-II. "Putting together and analyzing this huge dataset required cutting-edge ideas from computer science and statistics," said team member Gordon Richards of Drexel University. "Averaging over so many objects allowed us to measure an effect that is much too small to see in any individual quasar."

Supernova explosions and "winds" from massive stars drive gas out of some galaxies, Ménard explained, and this gas may carry dust with it. Alternatively, the dust may be pushed directly by starlight.

"Our findings now provide a reference point for theoretical studies," said Ménard.

Intergalactic dust could also affect planned cosmological experiments that use supernovae to investigate the nature of "dark energy," a mysterious cosmic component responsible for the acceleration of the expansion of the universe.

"Just like household dust, cosmic dust can be a nuisance," said Scranton. "Our results imply that most distant supernovae are seen through a bit of haze, which may affect estimates of their distances."

Intergalactic dust doesn't remove the need for dark energy to explain current supernova data, Ménard explained, but it may complicate the interpretation of future high-precision distance measurements. "These experiments are very ambitious in their goals," said Ménard, "and subtle effects matter."

http://www.sdss.org/

Physicists See The Cosmos In A Coffee Cup

2009-05-25T04:12:00.000-07:00

A Duke University professor and his graduate student have discovered a universal principle that unites the curious interplay of light and shadow on the surface of your morning coffee with the way gravity magnifies and distorts light from distant galaxies.

They think scientists will be able to use violations of this principle to map unseen clumps of dark matter in the universe.

Light rays naturally reflect off a curve like the inside surface of a coffee cup in a curving, ivy leaf pattern that comes to a point in the center and is brightest along its edge.

Mathematicians and physicists call that shape a "cusp curve," and they call the bright edge a "caustic," based on an alternative dictionary definition meaning "burning bright," explains Arlie Petters, a Duke professor of mathematics, physics and business administration. "It happens because a lot of light rays can pile up along curves."

Drawn by the mathematically-inclined artist Leonardo da Vinci in the early 16th century, caustics can be seen elsewhere in everyday life, including sunlight reflecting across a swimming pool's surface and choppy wave-light patterns reflecting off a boat hull.

Caustics also show up in gravitational lensing, a phenomenon caused by galaxies so massive that their gravity bends and distorts light from more distant galaxies. "It turns out that their gravity is so powerful that some light rays are also going to pile up along curves," said Petters, a gravitational lensing expert.

"Mother Nature has to be creating these things," Petters said. "It's amazing how what we can see in a coffee cup extends into a mathematical theorem with effects in the cosmos."

From the vantage point of Earth, the entire cosmos looks like a vast interplay of gravity and light that can extend far back into spacetime. "As with any illumination pattern, some areas will be brighter than others," Petters said. "And the brightest parts will be along these caustic curves."

Interpreting data from telescope surveys correctly requires understanding the distortions inherent in lensing, which sometimes warps a more distant point of light into multiple and magnified copies of themselves.

Petters and other researchers have previously found that, if such a light source seems to be juxtaposed within the confines of a caustic arch, two duplicate images will appear to be positioned abnormally close to each other and also seem equally bright. And because these clones are of seemingly equal brightness, subtracting one luminosity from the other results in a difference of zero.

In an article appearing in the March 23 Journal of Mathematical Physics, Petters and graduate student Amir Aazami extended the mathematics of such relatively simple examples to include what Petters called "higher order caustics." In such situations the interplay of light and gravity may extend further into spacetime and undergo various forms of "caustic metamorphosis" in the process.

Aazami was informally testing out a special case of their evolving caustics theorem called an "ellyptic umbilic" by using a technical computing software program called Mathematica when he noticed a pattern.

"It kept getting zero over and over again," Aazami said, no matter what scenario he tried the software on. "So I thought, 'it's making a mistake.' And I went back and looked again, and I kept getting zero. And I said, 'this is beginning to make sense!' That was the 'Ah Ha!' moment."

Petters realized his graduate student had found a universal mathematical principle so pervasive that it can impose balance on the most complicated gravitational lensing illusions. For instance, if lensing produces four light source copies of uneven brightnesses, the relative dimness of some is precisely balanced by the relative luminosity of others so they cancel each other out.

"It's miraculous that they cancel out," Petters said. "This relates to very sophisticated mathematics that you would never think could have anything to do with nature."

The Duke researchers said that for the simplest caustics, the theorem has already been corroborated by a few actual gravitational lensing observations. And they expect the higher order caustics to be observed once the Large Synoptic Survey Telescope (LSST), now being assembled in Chile, begins what Petters called "the most massive survey of the sky known" in a few years.

"We feel very confident that these universal invariants will show themselves in the data to come from the LSST," he said.

Another scenario he predicts are exceptions to the rule: "For one of the higher order caustics, if there are two pairs of lensed images that are close to each other but not equally bright, then the theorem is violated," he said.

"The reason would be some substructure in the galaxy," he said, likely dark matter near one of the images that causes it to be demagnified.

Dark matter is a mysterious substance that astronomers cannot directly observe but can "sense" by its gravitational tug on light. By using the LSST in conjunction with their theorem, astronomers "would be able to identify dark matter substructures in complex galactic systems," Petters predicted

The research was supported by the National Science Foundation.

http://www.duke.edu/

Earliest Meteorites Provide New Piece In Planetary Formation Puzzle

2009-05-22T04:38:00.000-07:00

Researchers trying to understand how the planets formed have uncovered a new clue by analysing meteorites that are older than the earth.

The research shows that the process which depleted planets and meteorites of so-called volatile elements such as zinc, lead and sodium, must have been one of the first things to happen in our nebula.

The implication of this clue is that 'volatile depletion' may be an inevitable part of planet formation - a feature not just of our Solar System, but of many other planetary systems too.

The researchers at Imperial College London reached their conclusions after analysing the composition of primitive meteorites, coal-like rocks that are older than the earth and which have barely changed since the Solar System was made up of fine dust and gas.

Their analysis, published today in the Proceedings of the National Academy of Sciences, shows that all the components that make up these rocks are depleted of volatile elements. This means that volatile element depletion must have occurred before the earliest solids had formed.

Dr. Phil Bland, from Imperial's Department of Earth Science and Engineering, who led the research, explains: "Studying meteorites helps us to understand the initial evolution of the early Solar System, its environment, and what the material between stars is made of. Our results answer one of a huge number of questions we have about the processes that converted a nebula of fine dust and gas into planets."

For planetary scientists, the most valuable meteorites are those that are found immediately after falling to earth, and so are only minimally contaminated by the terrestrial environment. The researchers analysed around half of the approximately 45 primitive meteorite falls in existence around the world.

All of the terrestrial planets in the Solar System as far out as Jupiter, including Earth, are depleted of volatile elements. Researchers have long known that this depletion must have been an early process, but it was unknown whether it occurred at the beginning of the formation of the Solar System, or a few million years later.

Dr. Phil Bland is a member of the Impacts and Astromaterials Research Centre (IARC), which combines planetary science researchers from Imperial College London and the Natural History Museum.

http://www3.imperial.ac.uk/media

How Special Is The Solar System?

2009-05-22T04:36:00.000-07:00

On the evidence to date, our solar system could be fundamentally different from the majority of planetary systems around stars because it formed in a different way. If that is the case, Earth-like planets will be very rare. After examining the properties of the 100 or so known extrasolar planetary systems and assessing two ways in which planets could form, Dr Martin Beer and Professor Andrew King of the University of Leicester, Dr Mario Livio of the Space Telescope Science Institute and Dr Jim Pringle of the University of Cambridge flag up the distinct possibility that our solar system is special in a paper to be published in the Monthly Notices of the Royal Astronomical Society.

In our solar system, the orbits of all the major planets are quite close to being circular (apart from Pluto’s, which is a special case), and the four giant planets are a considerable distance from the Sun. The extrasolar planets detected so far - all giants similar in nature to Jupiter – are by comparison much closer to their parent stars, and their orbits are almost all highly elliptical and so very elongated.

‘There are two main explanations for these observations,’ says Martin Beer. ‘The most intriguing is that planets can be formed by more than one mechanism and the assumption astronomers have made until now - that all planets formed in basically the same way - is a mistake.’

In the picture of planet formation developed to explain the solar system, giant planets like Jupiter form around rocky cores (like the Earth), which use their gravity to pull in large quantities of gas from their surroundings in the cool outer reaches of a vast disc of material. The rocky cores closer to the parent star cannot acquire gas because it is too hot there and so remain Earth-like.

The most popular alternative theory is that giant planets can form directly through gravitational collapse. In this scenario, rocky cores - potential Earth-like planets - do not form at all. If this theory applies to all the extrasolar planet systems detected so far, then none of them can be expected to contain an Earth-like planet that is habitable by life of the kind we are familiar with.

However, the team are cautious about jumping to a definite conclusion too soon and warn about the second possible explanation for the apparent disparity between the solar system and the known extrasolar systems. Techniques currently in use are not yet capable of detecting a solar-system look-alike around a distant star, so a selection effect might be distorting the statistics - like a fisherman deciding that all fish are larger than 5 inches because that is the size of the holes in his net.

It will be another 5 years or so before astronomers have the observing power to resolve the question of which explanation is correct. Meanwhile, the current data leave open the possibility that the solar system is indeed different from other planetary systems.

Notes

1. Currently around 100 extrasolar planets are known which have been detected through the wobble of their host stars caused by the motion of the planets themselves.

2. The paper has recently been accepted by the Monthly Notices of the Royal Astronomical Society but no publication date has yet been set.

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http://www.ras.org.uk/

First Planet Under Three Suns Is Discovered

2009-05-22T04:34:00.000-07:00

An extrasolar planet under three suns has been discovered in the constellation Cygnus by a planetary scientist at the California Institute of Technology using the 10-meter Keck I telescope in Hawaii. The planet is slightly larger than Jupiter and, given that it has to contend with the gravitational pull of three bodies, promises to seriously challenge our current understanding of how planets are formed.

In the July 14 issue of Nature, Maciej Konacki, a senior postdoctoral scholar in planetary science at Caltech, reports on the discovery of the Jupiter-class planet orbiting the main star of the close-triple-star system known as HD 188753. The three stars are about 149 light-years from Earth and are about as close to one another as the distance between the sun and Saturn.

In other words, a viewer there would see three bright suns in the sky. In fact, the sun that the planet orbits would be a very large object in the sky indeed, given that the planet's "year" is only three and a half days long. And it would be yellow, because the main star of HD 188753 is very similar to our own sun. The larger of the other two suns would be orange, and the smaller red.

Konacki refers to the new type of planet as "Tatooine planets," because of the similarity to Luke Skywalker's view of his home planet's sky in the first Star Wars movie.

"The environment in which this planet exists is quite spectacular," says Konacki. "With three suns, the sky view must be out of this world-literally and figuratively."

However, Konacki adds that the fact that a planet can even exist in a multiple-star system is amazing in itself. Binary and multiple stars are quite common in the solar neigborhood, and in fact outnumber single stars by some 20 percent.

Researchers have found most of the extrasolar planets discovered so far by using a precision velocity technique that is easier to employ on studies of single stars. Experts generally avoided close-binary and close-multiple stars because the existing planet detection techniques fail for such complicated systems, and also because theories of solar-system formation suggested that planets were very unlikely to form in such environments.

Konacki's breakthrough was made possible by his development of a novel method that allows him to precisely measure velocities of all members of close-binary and close-multiple-star systems. He used the technique for a search for extrasolar planets in such systems with the Keck I telescope. The planet in the HD 188753 system is the first one from this survey.

"If we believe that the same basic processes lead to the formation of planets around single stars and components of multiple stellar systems, then such processes should be equally feasible, regardless of the presence of stellar companions," Konacki says. "Planets from complicated stellar systems will put our theories of planet formation to a strict test."

Scientists in 1995 discovered the first "hot Jupiter"-in other words, an extrasolar gas-giant planet with an orbital period of three to nine days. Today, more than 20 such planets are known to orbit other stars. These planets are believed to form in a disk of gas and condensed matter at or beyond three astronomical units (three times the 93-million-mile distance between the sun and Earth).

A sufficient amount of solid material exists at three astronomical units to produce a core capable of capturing enough gas to form a giant planet. After formation, these planets are believed to migrate inward to their present very close orbits.

If the parent star is orbited by a close stellar companion, then its gravitational pull can significantly truncate a protoplanetary disk around the main star. In the case of HD 188753, the two stellar companions would truncate the disk around the main star to a radius of only 1.3 astronomical units, leaving no space for a planet to form.

"How that planet formed in such a complicated setting is very puzzling. I believe there is yet much to be learned about how giant planets are formed," says Konacki.

The research was funded by NASA

http://www.caltech.edu/

Three New Exo-planets Discovered

2009-05-22T04:32:00.000-07:00

The UK's leading team of planet-hunting astronomers, the Wide Angle Search for Planets (WASP), have announced the discovery of three new planets.

These extra-solar planets were seen to pass in front of, or transit, their host star. Studying such planets outside of our Solar System allows scientists to investigate how planetary systems form. WASP is the first team to detect planets in both the Northern and Southern Hemisphere using this technique.

Exoplanet expert Dr. Pierre Maxted comments “The planets are known as ‘hot-Jupiters’ as they are similar to Jupiter but are so close to their parent star that they orbit it in less than two days. This means that these planets have a surface temperature of nearly 2000°C and so are unlikely to host life. But finding these planets is important as these stars could also host much smaller planets similar to Earth, although detecting these worlds will be much more difficult”.

The planets orbit around stars similar to our Sun that are located at a distance of 850 light-years away from the Earth. Two are in the constellation of Phoenix visible only from the Southern hemisphere, while the third is in the Northern constellation of Lyra. All three stars are too faint to be seen with the naked eye, but are easily detectable with a small telescope.

Dr Coel Hellier, of Keele University, comments "When we see a transit we can deduce the size and mass of the planet and also what it is made of, so we can use these planets to study how solar systems form."

WASP-4 and WASP-5 are the first planets discovered by the WASP project's cameras in South Africa, and were confirmed by a collaboration with Swiss and French astronomers. "These two are now the brightest transiting planets in the Southern hemisphere" said Dr Hellier. WASP-3 is the third planet that the team has found in the North, using the SuperWASP camera sited in the Canary Islands.

Using data produced by SuperWASP’s cameras, which monitor up to 400,000 stars every minute, the new extra-solar planets were discovered as they were seen to pass in front of their host star.

Explaining the discovery, Dr Don Pollacco of Queen’s University, Belfast, Astrophysics Research Centre said: “We take pictures of the sky and measure the brightness of stars. If a planet is going around one of these stars and it happens to pass across the face of that star, our cameras will pick up the light from the star getting a little fainter.

“Discoveries such as these open up a whole new area of astronomy. Such transiting planets are important because they are the only ones that can have their mass and size measured directly. Astronomers can determine what they are made of and armed with this information we can begin to understand how these solar systems were formed.”

The WASP project is the most ambitious project in the world designed to discover large planets. Funding for the project comes from the UK Universities and the Science and Technology Facilities Council.

http://www.keele.ac.uk/

Jupiter-like Planets Could Form Around Twin Suns

2009-05-22T04:30:00.000-07:00

Life on a planet ruled by two suns might be a little complicated. Two sunrises, two sunsets. Twice the radiation field.

In a paper published in the December 2008 issue of Astronomy and Astrophysics, astronomer Joel Kastner and his team suggest that planets may easily form around certain types of twin (or “binary”) star systems. A disk of molecules discovered orbiting a pair of twin young suns in the constellation Sagittarius strongly suggests that many such binary systems also host planets.

“We think the molecular gas orbiting these two stars almost literally represents ‘smoking gun’ evidence of recent or possibly ongoing ‘giant’ (Jupiter-like) planet formation around the binary star system,” says Kastner, professor at Rochester Institute of Technology’s Chester F. Carlson Center for Imaging Science.

Kastner 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 two stars in a binary system called V4046 Sgr, which lies about 210 light-years away from our solar system. (V4046 Sgr is the 4046th brightest variable-brightness star in the constellation Sagittarius.) The scientists found “in large abundance” raw materials for planet formation around the nearby stars, including circumstellar carbon monoxide and hydrogen cyanide, in the noxious molecular gas cloud.

The young stars, approximately 10 million years old, are close in proximity to each other—only 10 solar diameters apart—and orbit each other once every 2.5 days.

“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 it’s a real link between planets forming around single stars and planets forming around double stars,” Kastner says.

Planets that have just formed around young stars like the V4046 Sgr twins might leave leftover gas, a potential clue for astronomers who hunt planets.

Recently, direct imaging of planets orbiting the single stars Fomalhaut and HR 8799 irrefutably confirmed the existence of exosolar planets—those that orbit stars other than our Sun. In the spring, Kastner hopes to use IRAM to look for gas left over from the formation of the planets orbiting HR 8799.

Kastner hopes to compare the molecular profile in the gas remnants surrounding the single star (HR 8799) with the gas composition surrounding the dual star-system (V4046 Sgr).

Not a planet hunter himself, Kastner encourages other scientists to look closely at V4046 Sgr to see if planets are forming around them.

“We really don’t have any idea right now about what kinds of planets form around double stars or even if planets can form around double stars,” Kastner says. “It’s not something that’s established. It’s theoretically possible, but I’m not aware of a single observation yet of a planet orbiting a double star. I hope someone will go looking soon, if they haven’t already, around V4046 Sagittarius.”

http://www.rit.edu/

Birth Of Tiniest Known Solar System

2009-05-22T04:28:00.000-07:00

Scientists using a combination of ground-based and orbiting telescopes have discovered a failed star, less than one-hundredth the mass of the sun, possibly in the process of forming a solar system. It is the smallest known star-like object to harbor what appears to be a planet-forming disk of rocky and gaseous debris, which one day could evolve into tiny planets and create a solar system in miniature.

A team led by Kevin Luhman, assistant professor of astronomy and astrophysics at Penn State, will discuss this finding in the Dec. 10 issue of Astrophysical Journal Letters.

The discovered object, called a brown dwarf, is described as a "failed star" because it is not massive enough to sustain nuclear fusion like our sun. The object is only eight times more massive than Jupiter. The fact that a brown dwarf this small could be in the midst of creating a solar system challenges the very definition of star, planet, moon and solar system.

"Our goal is to determine the smallest 'sun' with evidence for planet formation," said Luhman. "Here we have a sun that is so small it is the size of a planet. The question then becomes, what do we call any little bodies that might be born from this disk: planets or moons?" If this protoplanetary disk does form into planets, the whole system would be a miniaturized version of our solar system -- with the central "sun", the planets and their orbits all roughly 100 times smaller.

Luhman's team detected the brown dwarf, called Cha 110913-773444, with NASA's Spitzer Space Telescope, the Hubble Space Telescope and two telescopes in the Chilean Andes, the Blanco telescope of the Cerro Tololo Inter-American Observatory and the Gemini South telescope, both international collaborations funded in part by the National Science Foundation. Luhman led a similar observation last year that uncovered a 15-Jupiter-mass brown dwarf with a protoplanetary disk.

Brown dwarfs are born like stars, condensing out of thick clouds of gas and dust. But unlike stars, brown dwarfs do not have enough mass -- and therefore do not have enough pressure and temperature in their cores -- to sustain nuclear fusion. They remain relatively cool objects visible in lower-energy wavelengths such as infrared. A protoplanetary disk is a flat disk made up of dust and gas that is thought to clump together to form planets. Our solar system was formed from such a disk about 5 billion years ago. NASA's Spitzer telescope has found dozens of disk-sporting brown dwarfs so far, several of which show the initial stages of the planet-building process. The material in these disks is beginning to stick together into what may be the "seeds" of planets.

With Spitzer, the science team spotted Cha 110913-773444 about 500 light years away in the constellation Chamaeleon. This brown dwarf is young, only about 2 million years old. The team studied properties of the brown dwarf with infrared instruments on the other observatories. The cool, dim protoplanetary disk was detectable only with Spitzer's Infrared Array Camera, which was developed at the Harvard-Smithsonian Center for Astrophysics.

In the past decade, advances in astronomy have led to the detection of small brown dwarfs and massive extra-solar planets, which has brought about a quandary in taxonomy. "There are two camps when it comes to defining planets versus brown dwarfs," said team member Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics. "Some go by size, and others go by how the object formed. For instance, this new object would be called a planet based on its size, but a brown dwarf based on how it formed." If one were to call the object a planet, Fazio said, then Spitzer may have discovered its first "moon-forming" disk. No matter what the final label may be, one thing is clear: The universe produces some strange solar systems very different from our own. Other members of the discovery team are Lucia Adame and Paola D'Alessio of the National Autonomous University of Mexico and Nuria Calvet and Lee Hartmann of the University of Michigan.

The 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile is part of the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) Inc. under a cooperative agreement with the National Science Foundation. The nearby 8-meter Gemini South telescope also is managed by AURA. NASA's Goddard Space Flight Center, Greenbelt, Md., built Spitzer's Infrared Array Camera. The instrument's principal investigator is Giovanni Fazio. The Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena.

http://www.psu.edu/

Fifth Dwarf Planet Named Haumea

2009-05-22T04:26:00.001-07:00

The International Astronomical Union (the IAU) has announced that the object previously known as 2003 EL61 is to be classified as the fifth dwarf planet in the Solar System and named Haumea.

The decision was made after discussions by members of the International Astronomical Union's Committee on Small Body Nomenclature (CSBN) and the IAU Working Group for Planetary System Nomenclature (WGPSN). This now means that the family of dwarf planets in the Solar System is up to five. They are now Ceres, Pluto, Haumea, Eris and Makemake.

The discovery of Haumea was announced in mid-2005, and the object was initially given the provisional designation of 2003 EL61. It is a bizarre object with a shape resembling a plump cigar. Its diameter is approximately the same as that of the dwarf planet Pluto; however, its odd shape means that it is much thinner. It is also known to be spinning very fast, making one rotation in about four hours. Some have suggested that this rapid rotation could be the reason Haumea came to look as it does - the dwarf planet has been drawn out and elongated by its swift spin.

Haumea sits among the trans-Neptunian objects, a vast ring of distant cold and rocky bodies in the outer Solar System. At this moment it is roughly 50 times the Sun-Earth distance from the Sun, but at its closest the elliptical orbit of Haumea brings it 35 times the Sun-Earth distance from our star.

Haumea is the name of the goddess of childbirth and fertility in Hawaiian mythology. The name is particularly apt as the goddess Haumea also represents the element of stone and observations of Haumea hint that, unusually, the dwarf planet is almost entirely composed of rock with a crust of pure ice.

Hawaiian mythology says that the goddess Haumea's children sprang from different parts of her body. The dwarf planet Haumea has a similar history, as it is joined in its orbit by two satellites that are thought to have been created by impacts with it in the past. During these impacts, parts of Haumea's icy surface were blasted off. The debris from these impacts is then thought to have gone onto form the two moons.

After their discovery, in 2005, the moons were also given provisional designations, but have now too been given names by the CSBN and the WGPSN. The first and largest moon is to be called Hi'iaka, after the Hawaiian goddess who is said to have been born from the mouth of Haumea and the patron goddess of the island of Hawai'i. The second moon of Haumea is named Namaka, a water spirit who is said to have been born from Haumea's body.

http://www.iau.org/

Strings Of Shadowy Rings Drape Saturn

2009-05-21T04:56:00.000-07:00

Saturn's ring shadows appear wrapped in a harmonious symphony with the planet in this color view from the Cassini spacecraft.

Saturn and its rings would nearly fill the space between Earth and the Moon. Yet, despite their great breadth, the rings are a few meters thick and, in some places, very translucent. This image shows a view through the C ring, which is closest to Saturn, and through the Cassini division, the 4,800-kilometer-wide gap (2,980-miles) that arcs across the top of the image and separates the optically thick B ring from the A ring. The part of the atmosphere seen through the gap appears darker and more bluish due to scattering at blue wavelengths by the cloud-free upper atmosphere.

The different colors in Saturn's atmosphere are due to particles whose composition is yet to be determined. This image was obtained with the Cassini spacecraft narrow angle camera on July 30, 2004, at a distance of 7.6 million kilometers (4.7 million miles) from Saturn.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

http://www.jpl.nasa.gov/

Newfound Moon May Be Source Of Outer Saturn Ring

2009-05-21T04:54:00.000-07:00

NASA's Cassini spacecraft has found within Saturn's G ring an embedded moonlet that appears as a faint, moving pinprick of light. Scientists believe it is a main source of the G ring and its single ring arc.

Cassini imaging scientists analyzing images acquired over the course of about 600 days found the tiny moonlet, half a kilometer (about a third of a mile) across, embedded within a partial ring, or ring arc, previously found by Cassini in Saturn's tenuous G ring.

"Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. "The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring."

Saturn's rings were named in the order they were discovered. Working outward they are: D, C, B, A, F, G and E. The G ring is one of the outer diffuse rings. Within the faint G ring there is a relatively bright and narrow, 250-kilometer-wide (150-miles) arc of ring material, which extends 150,000 kilometers (90,000 miles), or one-sixth of the way around the ring's circumference. The moonlet moves within this ring arc. Previous Cassini plasma and dust measurements indicated that this partial ring may be produced from relatively large, icy particles embedded within the arc, such as this moonlet.

Scientists imaged the moonlet on Aug. 15, 2008, and then they confirmed its presence by finding it in two earlier images. They have since seen the moonlet on multiple occasions, most recently on Feb. 20, 2009. The moonlet is too small to be resolved by Cassini's cameras, so its size cannot be measured directly. However, Cassini scientists estimated the moonlet's size by comparing its brightness to another small Saturnian moon, Pallene.

Hedman and his collaborators also have found that the moonlet's orbit is being disturbed by the larger, nearby moon Mimas, which is responsible for keeping the ring arc together.

This brings the number of Saturnian ring arcs with embedded moonlets found by Cassini to three. The new moonlet may not be alone in the G ring arc. Previous measurements with other Cassini instruments implied the existence of a population of particles, possibly ranging in size from 1 to 100 meters (about three to several hundred feet) across. "Meteoroid impacts into, and collisions among, these bodies and the moonlet could liberate dust to form the arc," said Hedman.

Carl Murray, a Cassini imaging team member and professor at Queen Mary, University of London, said, "The moon's discovery and the disturbance of its trajectory by the neighboring moon Mimas highlight the close association between moons and rings that we see throughout the Saturn system. Hopefully, we will learn in the future more about how such arcs form and interact with their parent bodies."

Early next year, Cassini's camera will take a closer look at the arc and the moonlet. The Cassini Equinox mission, an extension of the original four-year mission, is expected to continue until fall of 2010.

The finding is being announced March 3 in an International Astronomical Union circular.

http://www.jpl.nasa.gov/

NASA Tests Largest Rocket Parachutes Ever

2009-05-21T04:51:00.000-07:00

NASA and industry engineers successfully completed the first test of the Ares I rocket's three main parachutes Wednesday. The parachutes -- the largest rocket parachutes ever manufactured -- are designed to slow the rapid descent of the rocket's spent first-stage motor, permitting its recovery for use on future flights.

The Ares I, the first rocket in NASA's Constellation Program, is designed to launch explorers aboard the Orion crew capsule on journeys to the International Space Station, the moon and beyond. The three main parachutes measure 150 feet in diameter and weigh 2,000 pounds each. They are a primary element of the rocket's deceleration system, which also includes a pilot parachute and drogue parachute. Deployed in a cluster, the main parachutes open at the same time, providing the drag necessary to slow the descent of the huge solid rocket motor to a soft landing in the ocean.

"The successful main chute cluster test today confirms the development and design changes we have implemented for the Ares I first stage recovery system," said Ron King, Ares I first stage deceleration subsystem manager for the Ares Projects at NASA's Marshall Space Flight Center in Huntsville, Ala. "Thanks to our great, collaborative team, the test went as anticipated, and all of our design objectives were met."

Engineers from Marshall managed the team that conducted this first cluster test at the U.S. Army's Yuma Proving Ground near Yuma, Ariz. This was the eighth in an ongoing series of flight tests supporting development of the Ares I recovery system. Researchers dropped the 41,500-pound load from a U.S. Air Force C-17 aircraft flying at an altitude of 10,000 feet. The parachutes and all test hardware functioned properly and landed safely.

As the test series progresses, engineers will perform three classifications of testing: development, design load and overload. Each level of testing is designed to fully test the performance of the new parachute design with different size payloads under varying conditions. The next test in the cycle -- scheduled for fall 2009 -- will involve the first design limit load test of a single main parachute.

The Ares I recovery system currently under development uses parachutes similar to those used for the four-segment space shuttle boosters, but the parachutes have been redesigned to accommodate the new requirements of the Ares I first stage. The Ares I launch vehicle will have a five-segment solid rocket booster that will fly faster and fall from a higher altitude than the shuttle boosters.

ATK Space Systems near Promontory, Utah, is the prime contractor for the first stage booster. ATK's subcontractor, United Space Alliance of Houston, is responsible for design, development and testing of the parachutes at its facilities at NASA's Kennedy Space Center in Florida.

NASA's Johnson Space Center in Houston manages the Constellation Program. Marshall manages the Ares Projects. The U.S. Army's Yuma Proving Ground provides the test range, support facilities and equipment to NASA for parachute testing.

http://www.nasa.gov/

Captain Kirk's Clone And The Eavesdropper

2009-05-21T04:48:00.000-07:00

Imagine Captain Kirk being beamed back to the Starship Enterprise and two versions of the Star Trek hero arriving in the spacecraft's transporter room.

It happened 40 years ago in an episode of the TV science fiction classic, and now scientists at the University of York and colleagues in Japan have managed something strikingly similar in the laboratory - though no starship commander was involved.

The first experimental demonstration of quantum telecloning has been achieved by scientists at the University of Tokyo, the Japan Science and Technology Agency, and the University of York. The work is reported in the latest issue of Physical Review Letters. Telecloning combines cloning (or copying) with teleportation (i.e., disembodied transport).

The scientists have succeeded in making the first remote copies of beams of laser light, by combining quantum cloning with quantum teleportation into a single experimental step. Telecloning is more efficient than any combination of teleportation and local cloning because it relies on a new form of quantum entanglement - multipartite entanglement.

Professor Sam Braunstein, of the Department of Computer Science at York, said: "Quantum mechanics allows us to do things which we previously thought were impossible. In 1998, I was involved in an experiment in America which was one of the first for quantum teleportation in which we transmitted a beam of light without it crossing the physical medium in between.

"This new experiment is an extension of that work. Whether it will change the world for individuals or is just of use to governments or big companies is hard to say. Any new protocol is like a new-born baby and it has to develop, but we know this one could be used to tap cryptographic channels.

"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."

Telecloning and teleportation may no longer be theories, but we are still a long way from teleporting people.

Professor Braunstein said: "What we know is that it would be incredibly difficult and from the perspective of today's technology, a completely outrageous thing. But in 100 years, who knows?"

http://www.york.ac.uk/

'Star Trek' Warp Speed

2009-05-21T04:46:00.000-07:00

With the new movie ‘Star Trek’ opening in theaters across the nation, one thing movie goers will undoubtedly see is the Starship Enterprise racing across the galaxy at the speed of light. But can traveling at warp speed ever become a reality?

Two Baylor University physicists believe they have an idea that can turn traveling at the speed of light from science fiction to science, and their idea does not break any laws of physics.

Dr. Gerald Cleaver, associate professor of physics at Baylor, and Dr. Richard Obousy, a Baylor post-doctoral student, theorize that by manipulating the space-time dimensions around the spaceship with a massive amount of energy, it would create a “bubble” that could push the ship faster than the speed of light. To create this bubble, the Baylor physicists believe manipulating the 11-dimension would create dark energy. Cleaver said positive dark energy is responsible for speeding up the universe as time moves on, just like it did after the Big Bang, when the universe expanded faster than the speed of light.

“Think of it like a surfer riding a wave,” said Cleaver, who co-authored the paper with Obousy about the new method. “The ship would be pushed by the bubble and the bubble would be traveling faster than the speed of light.”

The method is based on the Alcubierre drive, which proposes expanding the fabric of space behind a ship into a bubble and shrinking space-time in front of the ship. The ship would not actually move, rather the ship would sit in between the expanding and shrinking space-time dimensions. Since space would move around the ship, the theory does not violate Einstein’s Theory of Relativity, which states that it would take an infinite amount of energy to accelerate an object faster than the speed of light.

String theory suggests the universe is made up of multiple dimensions. Height, width and length are three dimensions, and time is the fourth dimension. Scientists believe that there are a total of 10 dimensions, with six other dimensions that we can not yet identify. A new theory, called M-theory, takes string theory one step farther and states that the “strings” actually vibrate in an 11-dimensional space. It is this 11th dimension that the Baylor researchers believe could help propel a ship faster than the speed of light.

The Baylor physicists estimate that the amount of energy needed to influence the extra dimensions is equivalent to the entire mass of Jupiter being converted into energy.

“That is an enormous amount of energy,” Cleaver said. “We are still a very long ways off before we could create something to harness that type of energy.”

http://www.baylor.edu/

Mars Sample Return

2009-05-21T04:44:00.000-07:00

The first robotic mission to return samples to Earth from Mars took a further step toward realisation with the recent publication of a mission design report by the iMARS Working Group. The report defines key elements of the future internationally-funded mission involving the cooperation of ESA, NASA and other national agencies.

iMARS, which stands for the International Mars Architecture for the Return of Samples, is a committee of the International Mars Exploration Working Group made up of scientists, engineers, strategic planners, and managers. The report, which comes after months of deliberation, outlines the scientific and engineering requirements of such an international mission to be undertaken in the timeframe 2020-2022.

The Mars Sample Return mission is an essential step with respect to future exploration goals and the prospect of establishing a future human mission to Mars. Returned samples will increase the knowledge of the properties of Martian soil and contribute significantly to answering questions about the possibility of life on the Red Planet. This mission will improve our understanding of the Mars environment to support planning for the future human exploration.

The iMARS report outlines the mission’s scientific objectives including the types and quantities of samples to be returned from Mars; the different mission elements (launchers, spacecraft, Mars lander, a rover and a Mars ascent vehicle) and ground processing facilities necessary to contain and analyse the received samples in a protected environment. A preliminary timeline for the mission and approximate budget has also been defined.

“Exploration is gaining momentum year by year, as is the experience and knowledge gained by ESA and its international partners in this area” said Bruno Gardini ESA’s Exploration Programme Manager in the Directorate of Human Spaceflight and iMARS study leader. “The information we gain from current Mars missions and from the ISS provide a basis not only for future robotic missions but also a stepping stone for the human exploration missions.”

http://www.esa.int/esaCP/index.html

New Spaceship Force Field Makes Mars Trip Possible

2009-05-21T04:42:00.000-07:00

According to the international space agencies, "space weather" is the single greatest obstacle to deep space travel. Radiation from the sun and cosmic rays pose a deadly threat to astronauts in space. New research shows how knowledge gained from the pursuit of nuclear fusion research may reduce the threat to acceptable levels, making humanity's first mission to Mars a much greater possibility.

The solar energetic particles, although just part of the 'cosmic rays' spectrum, are of greatest concern because they are the most likely to cause deadly radiation damage to the astronauts.

Large numbers of these energetic particles occur intermittently as "storms" with little warning and are already known to pose the greatest threat to man. Nature helps protect the Earth by having a giant "magnetic bubble" around the planet called the magnetosphere.

The Apollo astronauts of the 1960's and 70's who walked upon the Moon are the only humans to have travelled beyond the Earth's natural "force field" – the Earth's magnetosphere. With typical journeys on the Apollo missions lasting only about 8 days, it was possible to miss an encounter with such a storm; a journey to Mars, however, would take about eighteen months, during which time it is almost certain that astronauts would be enveloped by such a "solar storm".

Space craft visiting the Moon or Mars could maintain some of this protection by taking along their very own portable "mini"-magnetosphere. The idea has been around since the 1960's but it was thought impractical because it was believed that only a very large (more than 100km wide) magnetic bubble could possibly work.

Researchers at the Science and Technology Facilities Council's Rutherford Appleton Laboratory, the Universities of York, Strathclyde and IST Lisbon, have undertaken experiments, using know-how from 50 years of research into nuclear fusion, to show that it is possible for astronauts to shield their spacecrafts with a portable magnetosphere - scattering the highly charged, ionised particles of the solar wind and flares away from their space craft.

Computer simulations done by a team in Lisbon with scientists at Rutherford Appleton last year showed that theoretically a very much smaller "magnetic bubble" of only several hundred meters across would be enough to protect a spacecraft.

Now this has been confirmed in the laboratory in the UK using apparatus originally built to work on fusion. By recreating in miniature a tiny piece of the Solar Wind, scientists working in the laboratory were able to confirm that a small "hole" in the Solar Wind is all that would be needed to keep the astronauts safe on their journey to our nearest neighbours.

Dr. Ruth Bamford, one of the lead researchers at the Rutherford Appleton Laboratory, said, "These initial experiments have shown promise and that it may be possible to shield astronauts from deadly space weather."

http://www.iop.org/

Shields For The Starship Enterprise: A Reality?

2009-05-21T04:40:00.000-07:00

In the last year space agencies in the United States, Europe, China, Japan and India have announced their intention to resume human exploration of the Solar system, beginning with the Moon and perhaps ultimately moving on to Mars. But travel beyond the immediate vicinity of the Earth carries significant risks for astronauts, not the least of which is the exposure to sometimes high levels of radiation. Now a team of scientists at the Rutherford Appleton Laboratory are set to construct an experimental magnetic shield that would protect explorers in their journeys between the planets. Dr Ruth Bamford presented this idea at the Royal Astronomical Society National Astronomy Meeting in Preston.

Cosmic rays and radiation from the Sun itself can cause acute radiation sickness in astronauts and even death. Between 1968 and 1973, the Apollo astronauts going to the moon were only in space for about 10 days at a time and were simply lucky not to have been in space during a major eruption on the sun that would have flooded their spacecraft with deadly radiation. In retrospect Neil Armstrong’s ‘one small step for Man’ would have looked very different if it had.

On the International Space Station there is a special thick-walled room to which the astronauts have had to retreat during times of increased solar radiation. However on longer missions the astronauts cannot live within shielded rooms, since such shielding would add significantly to the mass of the spacecraft, making them much more expensive and difficult to launch. It is also now known that the ‘drip-drip’ of even lower levels of radiation can be as dangerous as acute bursts from the sun.

On the surface of the Earth we are protected from radiation by the thick layers of the atmosphere. And the terrestrial magnetic field extends far into space, acting as a natural ‘force field’ to further protect our planet and deflecting the worst of the energetic particles from the Sun by creating a ‘plasma barrier’.

Now scientists at the Rutherford Appleton Laboratory in Oxfordshire plan to mimic nature. They will build a miniature magnetosphere in a laboratory to see if a deflector shield can be used to protect humans living on space craft and in bases on the Moon or Mars.

In order to work, an artificial mini-magnetosphere on a space craft will need to utilise many cutting edge technologies, such as superconductors and the magnetic confinement techniques used in nuclear fusion.

Thus science is following science fiction once again. The writers of Star Trek realised that any space craft containing humans would need protection from the hazardous effects of cosmic radiation. They envisioned a ‘deflector shield’ spreading out from the Starship Enterprise that the radiation would bounce off. These experiments will help to establish whether this idea could one day become a practical reality.

http://www.ras.org.uk/

More 'Star Trek' Than 'Snuggie'

2009-05-21T04:38:00.000-07:00

Alien creatures are the least of NASA's worries when it comes to moon travel. There are several potential threats to future missions - with space radiation at the top of the list. Now, a group of students at North Carolina State University has developed a "blanket" of sorts that covers lunar outposts - the astronauts' living quarters - to provide astronauts protection against radiation while also generating and storing power.
Astronauts who previously traveled to the moon had little protection against radiation, but were only exposed to it for a short amount of time. NASA's plans to return astronauts to the moon by 2020 - and to potentially keep them there for several months at a time - could be stymied by space radiation.

The surface of the moon is exposed to cosmic rays and solar flares - making radiation hard to stop with shielding. When these rays hit matter, they produce a dangerous spray of secondary particles which, when penetrating human flesh, can damage DNA, boosting the risk of cancer and other maladies.

Groups all over the globe are trying to determine ways to combat space radiation - including Michael Sieber, Ryan Boyle and Anne Tomasevich, all recent graduates of the textile engineering program at NC State. Their design of a lunar radiation shield with the ability to protect its inhabitants from radiation was reviewed by a panel of industry experts and chosen as one of 10 undergraduate abstract finalists in the Revolutionary Aerospace Systems Concepts Academic Linkage (RASC-AL) competition.

Sponsored by NASA and the National Institute of Aerospace, the RASC-AL competition challenges university students to think about what sorts of conditions astronauts will face when returning to the moon, then design projects that might become part of actual lunar exploration.

"We had many factors to consider in developing this outpost cover - not just being able to protect against radiation," Sieber says. "The product needed to be as lightweight as possible to feasibly fit on the transportation module, and have the ability to be easily erected by a minimum number of astronauts for immediate use once landing on the moon."

"These obstacles are where our knowledge of textile properties will give us an advantage," adds Dr. Warren Jasper, professor of textile engineering and advisor for the project. "This is a competition aimed at aerospace engineering students, but we understand the properties associated with different textile materials, and that gives us unique insight on how to troubleshoot some of these issues."

The "lunar texshield" is made from a lightweight polymer material that has a layer of radiation shielding that deflects or absorbs the radiation so astronauts are only exposed to a safe amount. The outermost surface of the shield includes a layer of solar cells to generate electricity, backed up by layers of radiation-absorbing materials. The advantages of the materials used in the design include flexibility, large surface area, ease of transportation, ease of construction and the ability to have multiple layers of independent functional fabrics.

The students will present their lunar texshield at the 2009 RASC-AL Forum held June 1-3 in Cocoa Beach, Fla. The project will be judged by a steering committee made up of experts from NASA, industry and universities.

"We aren't even sure what the prize is for being named first place - but that wasn't what was important to us," Sieber says. "We used what we've learned throughout our college careers and were able to apply that logic to provide a solution a real-world problem. That is what is cool to us."

http://www.ncsu.edu/

Youthful Supernovae Explained?

2009-05-20T10:23:00.000-07:00

A team of astronomers, led by Dr. Bo Wang from the Yunnan Observatory of the Chinese Academy of Sciences, has developed a new model which explains the formation of the most youthful type Ia supernovae. In a paper published in Monthly Notices of the Royal Astronomical Society, the researchers show how the transfer of material from a ‘helium star’ to a compact white dwarf companion causes these cataclysmic events to take place early on in the life of the galaxy they formed in.

Most type Ia supernovae are believed to occur when a white dwarf (the superdense remnant that is the end state of stars like the Sun) draws matter from a companion star orbiting close by. When the white dwarf mass exceeds the so-called Chandrasekhar limit of 1.4 times the mass of the Sun, it eventually collapses and within a few seconds undergoes a runaway nuclear fusion reaction, exploding and releasing a vast amount of energy as a type Ia supernova. Due to their high and remarkably consistent luminosities, astronomers use these events as ‘distance indicators’ to measure the distances to other galaxies and constrain our ideas about the Universe.

Scientists have confirmed more and more type Ia supernovae, and found that about half of them explode less than 100 million years after their host galaxy’s main star formation period. But previous models for these systems did not predict that they could be this young so Dr. Wang and his team set out to solve this mystery.

Employing a stellar evolution computer code, they performed calculations for about 2600 binary systems consisting of a white dwarf and a helium star, a hot blue star which has a spectrum dominated by emission from helium. They found that if the gravitational field of the white dwarf pulls material from a helium star and increases its mass beyond the Chandrasekhar limit, it will explode as a type Ia supernova within 100 million years of its formation.

The team now plans to model the properties of the companion helium stars at the moment of the supernova explosions, which could be verified by future observations from the Large sky Area Multi-Object fiber Spectral Telescope (LAMOST).

Team member Prof. Dr. Zhanwen Han comments, “Type Ia supernovae are a key tool to determine the scale of the Universe so we need to be sure of their properties. Our work shows that they can take place early on in the life of the galaxy they reside in.”

http://www.ras.org.uk/

FUSE Observations Strengthen White Dwarf Theory

2009-05-20T10:21:00.000-07:00

Observations of the white dwarf star, Sirius B, made with NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) satellite give astronomers firm new evidence that mathematical models widely used to predict white dwarf star mass and radius are correct.

Jay B. Holberg of the University of Arizona Lunar and Planetary Laboratory is presenting the result today at the American Astronomical Society in San Diego.

The FUSE result is important because Sirius B is one of the few stars that astronomers have to test their ideas on the relationship between mass and radius for white dwarf stars. White dwarf stars are small but astonishingly dense stars. Sirius B is the size of the Earth and as massive as the sun.

Theory that describes how white dwarf stars can exist emerged in the early 1930s, when Subramanyan Chandrasekhar – or Chandra, as he was known – calculated the limit to a white dwarf's mass by applying Einstein's theory of special relativity. It was one of the first applications of quantum mechanics to large physical systems in the sky.

No white dwarf star could be more than 1.4 times as massive as the sun or it will collapse, Chandra predicted.

"Chandra was the first person to lay out the essential details of how white dwarfs sustain themselves, and it is very, very different from the sun or any other stars," Holberg said.

Unlike most white dwarfs, Sirius B is part of a binary system, and astronomers can determine the mass of stars in a binary system.

"Having a binary system – when two stars orbit one another - is virtually the only way you can fundamentally measure the mass of a star," Holberg said. "You observe their orbits, get the period, know how far away they are, and you can find the sum of the two star masses. If you can time the orbits and know how far apart the stars are, you can determine the individual star masses. That's the most accurate way, the acceptable way to determine star masses.

"But this star has always been devilishly difficult to observe," Holberg said. The primary star in the system, Sirius A, is 8 light years from Earth and has twice the mass of the sun. It is the brightest star in the night sky, visible below Orion. Sirius B is 10,000 times dimmer than Sirius A. Astronomers can’t even see the white dwarf companion when it comes closest to the primary star during its 50-year, very elongated orbit around Sirius A.

For the post several years, Holberg and colleagues have observed Sirius B with the Voyager and Extreme Ultraviolet Explorer spacecrafts. They have refined the star's temperature and gravity - gravity being the gravitational field at the surface of the star - to refine estimates of its mass and radius.

"The methods we're using are spectroscopic. They infer the mass from synthetic models that we produce from measurements of temperature and gravity, the only two parameters of matter for a white dwarf."

Holberg and his colleagues published the best determination of Sirius B's mass-radius relationship in 1998, but that was "still far from definitive," Holberg said. "That is, the uncertainties are so large, that while these studies define the basic relationship, they don’t tell you lots of details we need to know about these stars."

The FUSE observations gave Holberg and his colleagues better spectral data on Sirius B's gravitational field and temperature needed to calculate mass. "And this is a very clean spectrum. We rolled the FUSE spacecraft to keep Sirius A from contaminating the spectrum, and we succeeded very well.

"The mathematical model very well predicts our results on the gravitational field, temperature and brightness of this white dwarf star," Holberg said. "That helps us determine the radius of the star. What we really want to do is determine mass and radius to within one percent. By verifying the Chandrasekhar limit, you put a great deal of astrophysics on much firmer footing," he added.

"Astronomy has reached the level where you can make very definitive comparisons between the models and the observations. And it looks like we are going to come out to what we expected," Holberg said.

http://www.arizona.edu/

Undercover Stars Among Exoplanet Candidates

2009-05-20T10:20:00.000-07:00

An international team of astronomers have accurately determined the radius and mass of the smallest core-burning star known until now.
The observations were performed in March 2004 with the FLAMES multi-fibre spectrograph on the 8.2-m VLT Kueyen telescope at the ESO Paranal Observatory (Chile). They are part of a large programme aimed at measuring accurate radial velocities for sixty stars for which a temporary brightness "dip" has been detected during the OGLE survey.

The astronomers find that the dip seen in the light curve of the star known as OGLE-TR-122 is caused by a very small stellar companion, eclipsing this solar-like star once every 7.3 days.

This companion is 96 times heavier than planet Jupiter but only 16% larger. It is the first time that direct observations demonstrate that stars less massive than 1/10th of the solar mass are of nearly the same size as giant planets. This fact will obviously have to be taken into account during the current search for transiting exoplanets.

In addition, the observations with the Very Large Telescope have led to the discovery of seven new eclipsing binaries, that harbour stars with masses below one-third the mass of the Sun, a real bonanza for the astronomers

http://www.eso.org/public/

Local Star's Cool Companion

2009-05-20T10:17:00.001-07:00

An international team, led by astronomers at the University of Hertfordshire in the UK, have discovered one of the coolest sub-stellar bodies ever found outside our own solar system, orbiting the red dwarf star Wolf 940, some 40 light years from Earth. Dr Ben Burningham of the University of Hertfordshire will present this discovery on Monday 20th April at the European Week of Astronomy and Space Science conference.
"Although it has a temperature of 300 degrees Celsius, almost hot enough to melt lead, temperature is relative when you study this sort of thing, and this object is cool by stellar standards. In fact this is the first time we've been able to study an object as cool as this in such detail", says Dr Burningham, "the fact that it is orbiting a star makes it extra special".

The object is thought to have formed like a star, but has ended up looking more like Jupiter. It is roughly the same size, despite being between 20 and 30 times as heavy, and when the infrared spectral "fingerprints" of the two objects are compared, their resemblance is striking.

The new object orbits its star at about 440 times the distance at which the Earth orbits the sun. At such a wide distance, it takes about 18,000 years to complete a single orbit.

Too small to be stars, so-called "brown dwarfs" have masses lower than stars but larger than gas giant planets like Jupiter. Due to their low temperature these objects are very faint in visible light, and are detected by their glow at infrared wavelengths.

Modelling the atmospheres of cool brown dwarfs is a complex task, but it is key to understanding what we see when we look at planets that orbit other stars. Models of emitted light from such objects, which are dominated by absorption due to water and methane gas, are sensitive to assumptions about their age and chemical make-up.

In most cases astronomers don't initially know much about the age and composition of brown dwarfs and this can make it hard to tell where the models are right, and where they are going wrong.

"What's so exciting in this case, is that we can use what we know about the primary star to find out about the properties of the brown dwarf, and that makes it an extremely useful find", explains Dr Burningham, "you can think of it as a Rosetta Stone for decrypting what the light from such cool objects is telling us".

The object has been named Wolf 940B, after the red dwarf star that it orbits, which was first catalogued by the pioneering German astronomer Max Wolf ninety years ago.

"Red dwarfs are the most populous stars in the Galaxy, and systems like this may be more common than we know" says Dr David Pinfield of the University of Hertfordshire, "As the generation of ongoing large scale surveys continues, we may discover a pack of Wolf-940B-like objects in our solar back yard."

Wolf 940B was initially discovered as part of a major infrared sky survey - the UKIRT Infrared Deep Sky Survey (UKIDSS) which is being carried out using the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea in Hawaii.

The object was found as part of a wider effort to find the coolest and least luminous bodies in our local Galactic neighbourhood, but it was then found to be a companion to the nearby red dwarf Wolf 940 through its common motion across the sky. The data used to confirm the discovery were obtained using telescopes in Chile, the Canary Islands and Hawaii.

Its temperature was then confirmed using data from the Gemini-North telescope on Mauna Kea. The team's findings will soon be published in the Monthly Notices of the Royal Astronomical Society.

Following its discovery with ground based telescopes, Wolf 940B, has since been observed by the NASA's Spitzer Space Telescope, and the findings from those observations will be published later this year.

"This object is going to continue to provide insights into the processes of cool brown dwarf, and warm planetary atmospheres for some time to come", says Dr Sandy Leggett, of the Gemini Observatory, "finding it was just the first step".

http://www.ras.org.uk/

The Sun's New Exotic Neighbor

2009-05-20T10:15:00.000-07:00

Using the European Southern Observatory's Very Large Telescope in Chile, an international team of researchers discovered a brown dwarf belonging to the 24th closest stellar system to the Sun. Brown dwarfs are intermediate objects that are neither stars nor planets. This object is the third closest brown dwarf to the Earth yet discovered, and one of the coolest, having a temperature of about 750 degrees Centigrade. It orbits a very small star at about 4.5 times the mean distance between the Earth and the Sun. Its mass is estimated to be somewhere between 9 and 65 times the mass of Jupiter.

At a time when astronomers are peering into the most distant Universe, looking at objects as far as 13 billion light-years away, one may think that our close neighbourhood would be very well known. Not so. Astronomers still find new star-like objects in our immediate vicinity. Using ESO's VLT, they just discovered a brown dwarf companion to the red star SCR 1845-6357, the 36th closest star to the Sun.

"This newly found brown dwarf is a valuable object because its distance is well known, allowing us to determine with precision its intrinsic brightness", said team member Markus Kasper (ESO). "Moreover, from its orbital motion, we should be able in a few years to estimate its mass. These properties are vital for understanding the nature of brown dwarfs."

To discover this brown dwarf, the team used the high-contrast adaptive optics NACO Simultaneous Differential Imager (SDI) on ESO's Very Large Telescope, an instrument specifically developed to search for extrasolar planets. The SDI camera enhances the ability of the VLT and its adaptive optics system to detect faint companions that would normally be lost in the glare of the primary star. In particular, the SDI camera provides additional, often very useful spectral information which can be used to determine a rough temperature for the object without follow-up observations.

Located 12.7 light-years away from us, the newly found object is nevertheless not the closest brown dwarf. This honour goes indeed to the two brown dwarfs surrounding the star Epsilon Indi, located 11.8 light years away.

However, this newly discovered brown dwarf is unique in many aspects. "Besides being extremely close to Earth, this object is a T dwarf - a very cool brown dwarf - and the only such object found as a companion to a low-mass star," said Beth Biller, a graduate student at the University of Arizona and lead author of the paper reporting the discovery. "It is also likely the brightest known object of its temperature because it is so close."

The discovery of this brown dwarf hints that, at least close to the Sun, cool brown dwarfs prefer to be part of a couple with a star or another brown dwarf, rather than wandering alone in the cosmic emptiness. Indeed, of the seven cool brown dwarfs that reside within 20 light years of the Sun, five have a companion.

"This has wide-ranging implications for theories of brown dwarf formation, which, until now, tend to favour the production of single brown dwarfs," said team member Laird Close (University of Arizona).

http://www.eso.org/public/

Astronomers Discover Youngest And Lowest Mass Dwarfs In Solar Neighborhood

2009-05-20T10:12:00.000-07:00

Astronomers have found three brown dwarfs with estimated masses of less than 10 times that of Jupiter, making them among the youngest and lowest mass sub-stellar objects detected in the solar neighbourhood to date.

The observations were made by a team of astronomers working at the Laboratoire d'Astrophysique de l'Observatoire de Grenoble (LAOG), France, using the Canada-France-Hawaii Telescope (CFHT). Andrew Burgess will be presenting the discovery at the European Week of Astronomy and Space Science at the University of Hertfordshire, Hatfield, on Wednesday 22nd April.

The dwarfs were found in a star forming region named IC 348, which lies almost 1000 light years from the Solar System towards the constellation of Perseus. This cluster is approximately 3 million years old – extremely young compared to our 4.5 billion year old Sun – which makes it a good location in order to search for the lowest mass brown dwarfs. The dwarfs are isolated in space, which means that they are not orbiting a star, although they are gravitationally bound to IC 348. Their atmospheres all show evidence of methane absorption which was used to select and identify these young objects.

"There has been some controversy about identifying young, low mass brown dwarfs in this region. An object of a similar mass was discovered in 2002, but some groups have argued that it is an older, cooler brown dwarf in the foreground coinciding with the line of sight. The fact that we have detected three candidate low-mass dwarfs towards IC 348 supports the finding that these really are very young objects," said Burgess.

The team set out to find a population of these brown dwarfs in order to help theoreticians develop more accurate models for the distribution of mass in a newly-formed population, from high mass stars to brown dwarfs, which is needed to test current star formation theories. The discovery of the dwarfs in IC 348 has allowed them to set new limits on the lowest mass objects.

"Finding three candidate low-mass dwarfs towards IC 348 backs up predictions for how many low-mass objects develop in a new population of stars. Brown dwarfs cool with age and current models estimate that their surfaces are approximately 900-1000 degrees Kelvin (about 600-700 degrees Celsius). That’s extremely cool for objects that have just formed, which implies that they have the lowest masses of any of this type of object that we’ve seen to date," said Burgess.

http://www.ras.org.uk/

Boring Star May Mean Livelier Planet, Astronomer Says

2009-05-19T00:17:00.000-07:00

Boring” light from red dwarf star Gliese 581 means better odds for extraterrestrial life in that planetary system, according to University of British Columbia astronomer Jaymie Matthews.

Approximately 20.5 light years from the Earth, Gliese 581 made the headlines in April 2007 when European scientists discovered a planet, named Gliese 581c. Dubbed “SuperEarth,” the planet orbits Gliese 581 and could have water -- and thus able to support life.

“The Gliese 581 system is the first to be found -- beyond our own Earth -- that might have a liveable planet,” said Matthews.

Using Canada Space Agency’s suitcase-sized space telescope, the Microvariability and Oscillations of STars (MOST), Matthews put Gliese 581 on a six-week scientific stakeout following the April discovery. He will present his findings today at the Canadian Astronomical Society’s annual meeting in Kingston, Ontario.

Matthews and his team searched for the subtle dips in the light from the star when the planet’s orbit carried it directly between the star and the Earth, resulting in a “mini-eclipse” every 13 days. The depth of the dips would help researchers determine the size of the planet Gliese 581c, while the behaviour of the starlight at other times would help astronomers gauge the suitability of Gliese 581 as a “home star,” a star able to sustain life on planets around it.

“Gliese 581 seems remarkably stable over the six weeks it was monitored by MOST,” said Matthews. “The brightness of the star changed by only a few tenths of a percent over that time. This level of stability means that it provides a stable source of light -- hence heat -- to the surface of planet Gliese 581c.

“The climate there should not be a wild rollercoaster ride that would make it difficult for life to get a foothold,” said Matthews. “It also suggests the star is quite old, and settled in its ways, and that the planets around it have probably been around for billions of years.”

It took approximately 3.5 billion years for life on Earth to reach the level of complexity that we call human, said Matthews. “So if Gliese 581 has been around for at least that long, it’s more encouraging for the prospects of complex life on any planet around it.”

With space missions like MOST, the French satellite COROT, which joined MOST in orbit late last December, and the American Kepler mission due for launch in November 2008, Matthews predicts that other ‘Earthy’ worlds will come to light in the coming months and years.

“Some of them will have orbits that produce planetary alignments,” said Matthews. “Not the kind that excites somebody reading a horoscope but the kind that’s exciting for astronomers because they will allow us to test our models of alien worlds -- worlds that might be homes to neighbours in our Galactic city, the Milky Way.”

MOST is a Canadian Space Agency mission, jointly operated by Dynacon Inc., the University of Toronto Institute for Aerospace Studies and the University of British Columbia, with the assistance of the University of Vienna.

http://www.astro.ubc.ca/MOST/

Lightest Exoplanet Yet Discovered

2009-05-19T00:15:00.000-07:00

Exoplanet researchers have discovered 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.

“The holy grail of current exoplanet research is the detection of a rocky, Earth-like planet in the ‘habitable zone’ — a region around the host star with the right conditions for water to be liquid on a planet’s surface,” says Michel Mayor from the Geneva Observatory, who led the European team to this stunning breakthrough.

Planet Gliese 581 e orbits its host star – located only 20.5 light-years away in the constellation Libra (“the Scales”) — in just 3.15 days. “With only 1.9 Earth-masses, it is the least massive exoplanet ever detected and is, very likely, a rocky planet”, says co-author Xavier Bonfils from Grenoble Observatory.

Being so close to its host star, the planet is not in the habitable zone. But another planet in this system appears to be. From previous observations — also obtained with the HARPS spectrograph at ESO’s La Silla Observatory and announced two years ago — this star was known to harbour a system with a Neptune-sized planet and two super-Earths. With the discovery of Gliese 581 e, the planetary system now has four known planets, with masses of about 1.9 (planet e), 16 (planet b), 5 (planet c), and 7 Earth-masses (planet d). The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days.

“Gliese 581 d is probably too massive to be made only of rocky material, but we can speculate that it is an icy planet that has migrated closer to the star,” says team member Stephane Udry. The new observations have revealed that this planet is in the habitable zone, where liquid water could exist. “‘d’ could even be covered by a large and deep ocean — it is the first serious 'water world' candidate,” continued Udry.

The gentle pull of an exoplanet as it orbits the host star introduces a tiny wobble in the star’s motion — only about 7 km/hour, corresponding to brisk walking speed — that can just be detected on Earth with today’s most sophisticated technology. Low-mass red dwarf stars such as Gliese 581 are potentially fruitful hunting grounds for low-mass exoplanets in the habitable zone. Such cool stars are relatively faint and their habitable zones lie close in, where the gravitational tug of any orbiting planet found there would be stronger, making the telltale wobble more pronounced. Even so, detecting these tiny signals is still a challenge, and the discovery of Gliese 581 e and the refinement of Gliese 581 d’s orbit were only possible due to HARPS’s unique precision and stability.

“It is amazing to see how far we have come since we discovered the first exoplanet around a normal star in 1995 — the one around 51 Pegasi,” says Mayor. “The mass of Gliese 581 e is 80 times less than that of 51 Pegasi b. This is tremendous progress in just 14 years.”

The astronomers are confident that they can still do better. “With similar observing conditions an Earth-like planet located in the middle of the habitable zone of a red dwarf star could be detectable,” says Bonfils. “The hunt continues.”

http://www.eso.org/public/

First Detailed Pictures Of Asteroid Reveal Bizarre System

2009-05-19T00:12:00.000-07:00

The first detailed images of a binary asteroid system reveal a bizarre world where the highest points on the surface are actually the lowest, and the two asteroids dance in each other's gravitational pull.

A binary asteroid is a system where two asteroids orbit around one another, like a mini Earth-moon system, said Daniel Scheeres, University of Michigan associate professor of aerospace engineering. The new results are scheduled to appear Oct. 12 in the journal Science in a pair of papers by Scheeres and Dr. Steven Ostro of the NASA/Caltech Jet Propulsion Laboratory.

The radar images of asteroid KW4 (the official full designation is 66391 1999 KW4) were obtained in May 2001, when the asteroid passed 4.8 million kilometers from Earth. Previously, KW4 was classified as a potentially hazardous asteroid (PHA) because of the proximity of the asteroid's orbit to Earth's orbit. The new observations show that there is no chance of KW4 hitting Earth within at least the next 1,000 years, Scheeres said.

"The KW4 results have profound consequences for ideas about mitigation of the asteroid collision hazard," Scheeres said.

The observations show that the larger object is spinning in its orbit so fast that it has been flattened into a kind of flying saucer shape, said Scheeres. Because of this, the mountainous region along the center of the asteroid actually forms the lowest part on the asteroid. In fact the asteroid is spinning so fast that the equatorial ridge is very close to lifting off the surface and spinning into space, he said.

Another interesting finding is that the two bodies in the asteroid system are orbiting so closely that they are caught in each other's gravitational pull.

"They are so close together that when one rotates it affects the other's movements," Scheeres said.

Based on the observations, the KW4 binary asteroid appears to have formed either from tidal disruption during a close pass by the Earth or from sunlight shining on it, so that it spins so fast that it eventually broke into two pieces. The odd shapes of asteroids cause them to sometimes spin faster and faster when illuminated by the sun, acting a bit like a solar sail, Scheeres said. This is called the YORP effect.

The recent findings also confirm that the asteroids are only floating piles of rubble held together by gravity and not a solid mass.

http://www.umich.edu/

How To Destroy An Asteroid: Blowing Up Killer Space Rocks Without Dangerous Debris

2009-05-19T00:10:00.000-07:00

In the hit 1998 movie Armageddon, Bruce Willis and Ben Affleck blew up an asteroid to save the world. While the film was science fiction, the chances of an asteroid hitting the Earth one day are very real ― and blowing up an asteroid in real life, says a Tel Aviv University researcher, will be more complicated than in the movies.
Astrophysicists agree that the best method for avoiding a catastrophic collision would be to change the path of the asteroid heading toward our planet. “For that to work, we need to be able to predict what would happen if we attempt an explosion,” says Tel Aviv University doctoral student David Polishook, who is studying asteroids with his supervisor Dr. Noah Brosch at the Department of Geophysics and Planetary Sciences.

Polishook and Brosch are among the few scientists in the world researching the structure and composition of asteroids a critical first step in learning how to destroy them before they reach the Earth’s atmosphere. Their research could prevent catastrophe: blowing up an asteroid may create many equally dangerous smaller asteroids of about 100 meters each in diameter ― twice the size of the asteroid that created the famous Arizona crater.

Looking on the Bright Sides

“The information we are investigating can have a tremendous impact on future plans to alter the course of asteroids on a collision course with Earth,” says Polishook. “Science needs to know whether asteroids are solid pieces of rock or piles of gravel, what forces are holding them together, and how they will break apart if bombed.”

By observing the waxing and waning brightness of far-away asteroids, Polishook is able to examine the shape, spin period and surface composition of these flying rocks. “This is a good way of evaluating what asteroids are made of,” says Polishook, who takes measurements on an almost daily basis at Tel Aviv University's Wise Observatory.

As part of their observations, the researchers used the fact that small asteroids change their rotation rate, accelerating or slowing down during short periods, as often as every 100,000 years. Compared to the age of the solar system 4.5 billion years that is an extremely fast change, says Polishook.

The most recent results of their research were presented at the 2008 meeting of Asteroids, Comets and Meteors, sponsored by the Johns Hopkins University Applied Physics Laboratory in Baltimore.

Size Matters

An asteroid’s rotation and acceleration are influenced by sunlight the “YORP Effect.” If the YORP effect causes an asteroid to rotate faster than one revolution in 2.2 hours, it will break apart.

To understand how the YORP Effect works on asteroids, Tel Aviv University researchers examined several variables relating to these asteroids, including size and location. They concluded that size is the most important factor in determining how an asteroid’s rotation rate accelerates according to the YORP Effect.

“We think this adds an important clue to how asteroids will behave should a space agency need to knock one off-course to prevent a collision with earth,” Polishook notes.

http://www.aftau.org/site/PageServer?pagename=home_page

Solar Wind Tans Young Asteroids

2009-05-19T00:08:00.000-07:00

A new study published in Nature this week reveals that asteroid surfaces age and redden much faster than previously thought — in less than a million years, the blink of an eye for an asteroid. This study has finally confirmed that the solar wind is the most likely cause of very rapid space weathering in asteroids.
This fundamental result will help astronomers relate the appearance of an asteroid to its actual history and identify any after effects of a catastrophic impact with another asteroid.

“Asteroids seem to get a ‘sun tan’ very quickly,” says lead author Pierre Vernazza. “But not, as for people, from an overdose of the Sun’s ultraviolet radiation, but from the effects of its powerful wind.”

It has long been known that asteroid surfaces alter in appearance with time — the observed asteroids are much redder than the interior of meteorites found on Earth [1] — but the actual processes of this “space weathering” and the timescales involved were controversial.

Thanks to observations of different families of asteroids [2] using ESO’s New Technology Telescope at La Silla and the Very Large Telescope at Paranal, as well as telescopes in Spain and Hawaii, Vernazza’s team have now solved the puzzle.

When two asteroids collide, they create a family of fragments with “fresh” surfaces. The astronomers found that these newly exposed surfaces are quickly altered and change colour in less than a million years — a very short time compared to the age of the Solar System.

“The charged, fast moving particles in the solar wind damage the asteroid’s surface at an amazing rate [3]”, says Vernazza. Unlike human skin, which is damaged and aged by repeated overexposure to sunlight, it is, perhaps rather surprisingly, the first moments of exposure (on the timescale considered) — the first million years — that causes most of the aging in asteroids.

By studying different families of asteroids, the team has also shown that an asteroid’s surface composition is an important factor in how red its surface can become. After the first million years, the surface “tans” much more slowly. At that stage, the colour depends more on composition than on age. Moreover, the observations reveal that collisions cannot be the main mechanism behind the high proportion of “fresh” surfaces seen among near-Earth asteroids. Instead, these “fresh-looking” surfaces may be the results of planetary encounters, where the tug of a planet has “shaken” the asteroid, exposing unaltered material.

Thanks to these results, astronomers will now be able to understand better how the surface of an asteroid — which often is the only thing we can observe — reflects its history.

Notes

[1] Meteorites are small fragments of asteroids that fall on Earth. While a meteorite enters the Earth's atmosphere its surface can melt and be partially charred by the intense heat. Nevertheless, the meteorite interior remains unaffected, and can be studied in a laboratory, providing a wealth of information on the nature and composition of asteroids.

[2] An asteroid family is a group of asteroids that are on similar orbits around the Sun. The members of a given family are believed to be the fragments of a larger asteroid that was destroyed during a collision.

[3] The surface of an asteroid is affected by the highly energetic particles forming the solar wind. These particles partially destroy the molecules and crystals on the surface, re-arranging them in other combinations. Over time, these changes give formation of a thin crust or irradiated material with distinct colours and properties.

http://www.nature.com/nature/journal/v458/n7241/full/nature07956.html

New Way To Weigh Giant Black Holes

2009-05-18T01:20:00.000-07:00

How do you weigh the biggest black holes in the universe? One answer now comes from a completely new and independent technique that astronomers have developed using data from NASA's Chandra X-ray Observatory.

By measuring a peak in the temperature of hot gas in the center of the giant elliptical galaxy NGC 4649, scientists have determined the mass of the galaxy's supermassive black hole. The method, applied for the first time, gives results that are consistent with a traditional technique.

Astronomers have been seeking out different, independent ways of precisely weighing the largest supermassive black holes, that is, those that are billions of times more massive than the Sun. Until now, methods based on observations of the motions of stars or of gas in a disk near such large black holes had been used.

"This is tremendously important work since black holes can be elusive, and there are only a couple of ways to weigh them accurately," said Philip Humphrey of the University of California at Irvine, who led the study. "It's reassuring that two very different ways to measure the mass of a big black hole give such similar answers."

NGC 4649 is now one of only a handful of galaxies for which the mass of a supermassive black hole has been measured with two different methods. In addition, this new X-ray technique confirms that the supermassive black hole in NGC 4649 is one of the largest in the local universe with a mass about 3.4 billion times that of the Sun, about a thousand times bigger than the black hole at the center of our galaxy.

The new technique takes advantage of the gravitational influence the black hole has on the hot gas near the center of the galaxy. As gas slowly settles towards the black hole, it gets compressed and heated. This causes a peak in the temperature of the gas right near the center of the galaxy. The more massive the black hole, the bigger the temperature peak detected by Chandra.

This effect was predicted by two of the co-authors -- Fabrizio Brighenti from the University of Bologna, Italy, and William Mathews from the University of California at Santa Cruz -- almost 10 years ago, but this is the first time it has been seen and used.

"It was wonderful to finally see convincing evidence of the effects of the huge black hole that we expected," said Brighenti. "We were thrilled that our new technique worked just as well as the more traditional approach for weighing the black hole."

The black hole in NGC 4649 is in a state where it does not appear to be rapidly pulling in material towards its event horizon, nor generating copious amounts of light as it grows. So, the presence and mass of the central black hole has to be studied more indirectly by tracking its effects on stars and gas surrounding it. This technique is well suited to black holes in this condition.

"Monster black holes like this one power spectacular light shows in the distant, early universe, but not in the local universe," said Humphrey. "So, we can't wait to apply our new method to other nearby galaxies harboring such inconspicuous black holes."

These results will appear in an upcoming issue of The Astrophysical Journal. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Most Powerful Eruption In The Universe Discovered

2009-05-18T01:18:00.000-07:00

Astronomers have found the most powerful eruption in the universe using NASA's Chandra X-ray Observatory. A super massive black hole generated this eruption by growing at a remarkable rate. This discovery shows the enormous appetite of large black holes, and the profound impact they have on their surroundings.
The huge eruption was seen in a Chandra image of the hot, X-ray emitting gas of a galaxy cluster called MS 0735.6+7421. Two vast cavities extend away from the super massive black hole in the cluster's central galaxy. The eruption, which has lasted for more than 100 million years, has generated energy equivalent to hundreds of millions of gamma-ray bursts.

This event was caused by gravitational energy release, as enormous amounts of matter fell toward a black hole. Most of the matter was swallowed, but some of it was violently ejected before being captured by the black hole. "I was stunned to find that a mass of about 300 million suns was swallowed," said Brian McNamara of Ohio University in Athens. "This is as large as another super massive black hole." He is lead author of the study about the discovery, which is in the January 6, 2005, issue of Nature.

Astronomers are not sure where such large amounts of matter came from. One theory is gas from the host galaxy catastrophically cooled and was swallowed by the black hole. The energy released shows the black hole in MS 0735 has grown dramatically during this eruption. Previous studies suggest other large black holes have grown very little in the recent past, and that only smaller black holes are still growing quickly.

"This new result is as surprising as it is exciting," said co-author Paul Nulsen of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. "This black hole is feasting, when it should be fasting."

Radio emission within the cavities shows jets from the black hole erupted to create the cavities. Gas is being pushed away from the black hole at supersonic speeds over a distance of about a million light-years. The mass of the displaced gas equals about a trillion suns, more than the mass of all the stars in the Milky Way.

The rapid growth of super massive black holes is usually detected by observing very bright radiation from the centers of galaxies in the optical and X-ray wavebands, or luminous radio jets. In MS 0735 no bright central radiation is found, and the radio jets are faint. The true nature of MS 0735 is only revealed through X-ray observations of the hot cluster gas.

"Until now we had no idea this black hole was gorging itself," said co-author Michael Wise of the Massachusetts Institute of Technology, Cambridge, Mass. "The discovery of this eruption shows X-ray telescopes are necessary to understand some of the most violent events in the universe."

The astronomers estimated how much energy was needed to create the cavities by calculating the density, temperature and pressure of the hot gas. By making a standard assumption that 10 percent of the gravitational energy goes into launching the jets, they estimated how much material the black hole swallowed.

Besides generating the cavities, some of the energy from this eruption should keep the hot gas around the black hole from cooling, and some of it may also generate large-scale magnetic fields in the galaxy cluster. Chandra observers have discovered other cavities in galaxy clusters, but this one is easily the largest and the most powerful.

NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Space Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images from Chandra are available on the Web at:

Chandra Discovers Light Echo From The Milky Way's Black Hole

2009-05-18T01:16:00.000-07:00

Like cold case investigators, astronomers have used NASA's Chandra X-ray Observatory to uncover evidence of a powerful outburst from the giant black hole at the Milky Way's center.
A light echo was produced when X-ray light generated by gas falling into the Milky Way's supermassive black hole, known as Sagittarius A* (pronounced "A-star"), was reflected off gas clouds near the black hole. While the primary X-rays from the outburst would have reached Earth about 50 years ago, the reflected X-rays took a longer path and arrived in time to be recorded by Chandra.

"This dramatic event happened before we had satellites in space that could detect it," said Michael Muno of the California Institute of Technology in Pasadena. "So, it's remarkable that we can use Chandra to dig into the past and see this monster black hole's capacity for destruction."

Previously, scientists have used Chandra to directly detect smaller and more recent outbursts from the black hole. This latest outburst revealed by the X-ray echo was about 1,000 times brighter and lasted well over 1,000 times longer than any of the recent outbursts observed by Chandra.

Theory predicts that an outburst from Sagittarius A* would cause X-ray emission from the clouds to vary in both intensity and shape. Muno and his team found these changes for the first time, thus ruling out other interpretations. The latest results corroborate other independent, but indirect, evidence for light echoes generated by the black hole in the more distant past.

Scientists have long known that Sagittarius A*, with a mass of about 3 million suns, lurked at the center for Milky Way. However, the black hole is incredibly faint at all wavelengths, especially in X-rays.

"This faintness implies that stars and gas rarely get close enough to the black hole to be in any danger," said co-author Frederick K. Baganoff of the Massachusetts Institute of Technology in Cambridge. "The huge appetite is there, but it's not being satisfied."

During the outburst, the area close to the black hole would have been about 100,000 times brighter than it is currently. If such an outburst had occurred more recently, it likely would have been detected by an X-ray instrument, or would have produced similar features in other nearby clouds.

"Our data show it has been 50 years or so since the black hole had its last decent meal," said Muno. "This is nothing like the feasting that black holes in other galaxies sometimes enjoy, but it gives unique knowledge about the feeding habits of our closest supermassive black hole."

The details of how Sagittarius A* feeds remain unclear. For example, one possibility is that the black hole grows by pulling in matter from the winds of nearby young stars. Also, if there is a disk of material swirling around Sagittarius A*, it might be unstable in such a way that material migrates toward the black hole's edge in clumps, emitting X-rays before disappearing from the universe forever. The theoretical work is still being developed.

Studying this light echo is also important because it illuminates and probes the poorly understood molecular clouds near the center of the galaxy. In particular, it gives information about the dense cores of these clouds where new stars may be forming.

Variability in the X-ray emission between three Chandra observations in 2002, 2004 and 2005 argues against an alternate source for the light echo, which is that it came from a neutron star or black hole pulling matter away from a binary companion. This explanation is not favored because the data show the outburst would have been unusually long and bright for such a binary.

These results were presented at the American Astronomical Society meeting in Seattle, Wash., and will appear in an upcoming issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass.

Adapted from materials provided by Chandra X-ray Center.

Scientists Find Black Hole's 'Point Of No Return'

2009-05-18T01:13:00.000-07:00

Scientists have found new evidence that black holes are performing the disappearing acts for which they are known.
A team from MIT and Harvard has found that a certain type of X-ray explosion common on neutron stars is never seen around their black hole cousins, as if the gas that fuels these explosions has vanished into a void.

This is strong evidence, the team said, for the existence of a theoretical border around a black hole called an event horizon, a point from beyond which nothing, not even light, can escape.

Ron Remillard of the Kavli Institute for Astrophysics and Space Research at MIT led the analysis and is discussing his team's result Jan. 9 at a press conference at the 207th meeting of the American Astronomical Society in Washington, D.C. His colleagues are Dacheng Lin of MIT and Randall Cooper and Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge.

The scientists studied a complete sample of transient X-ray sources detected with NASA's Rossi X-ray Timing Explorer during the last nine years. They detected 135 X-ray bursts from the 13 sources believed to be neutron stars, but none from the 18 suspected black holes.

Gas released by a nearby star can accumulate on the hard surface of a neutron star, and it will eventually erupt in a thermonuclear explosion. The more massive compact objects in this study suspected of being black holes appeared to have no surface. Gas falling toward the black hole seems to disappear.

"Event horizons are invisible by definition, so it seems impossible to prove their existence," said Remillard. "Yet by looking at dense objects that pull in gas, we can infer whether that gas crashes and accumulates onto a hard surface or just quietly vanishes. For the group of suspected black holes we studied, there is a complete absence of surface explosions called X-ray bursts."

A black hole forms when a very massive star runs out of fuel. Without energy to support its mass, the star implodes. If the star is more than 25 times more massive than our sun, the core will collapse to a point of infinite density with no surface. Within a boundary of about 50 miles from the black hole center, gravity is so strong that not even light can escape its pull. This boundary is the theoretical event horizon.

Stars of about 10 to 25 solar masses will collapse into compact spheres about 10 miles across, called neutron stars. These objects have a hard surface and no event horizon.

Black holes and their neutron star cousins are sometimes located in binary systems, orbiting a relatively normal star companion. Gas from these stars, lured by strong gravity, can flow toward the compact object periodically. This process, called accretion, releases large amounts of energy, predominantly in the form of X-rays.

Gas can accumulate on a neutron star surface, and when conditions are ripe, the gas will ignite in a thermonuclear explosion that is visible as a one-minute event called a Type I X-ray burst. The suspected black holes -- that is, the more massive types of compact objects in this study -- behave as if they have no surface and are located behind event horizons.

The idea of using the absence of X-ray bursts to confirm the presence of event horizons in black holes was proposed in 2002 by Harvard's Narayan and Jeremy Heyl of the University of British Columbia in Vancouver.

The Rossi Explorer, launched on Dec. 30, 1995, is operated by NASA Goddard Space Flight Center in Greenbelt, Md.

Big Black Holes Cook Flambeed Stellar Pancakes

2009-05-18T01:11:00.000-07:00

According to two astrophysicists from Paris Observatory, the fate of stars that venture too close to massive black holes could be even more violent than previously believed. Not only are they crushed by the black hole’s huge gravity, but the process can also trigger a nuclear explosion that tears the star apart from within. In addition, shock waves in the pancake star carry a brief and very high peak of temperature outwards, that could give rise to a new type of X-ray or gamma-ray bursts.
Scientists have long understood that massive black holes lurking in galactic nuclei and weighing millions of Suns can disrupt stars that come too close. Due to intense tidal forces, the black hole’s gravity pulls harder on the nearest part of the star, an imbalance that pulls the star apart over a period of hours, once it gets inside the so-called “tidal radius”.

Now, Matthieu Brassart and Jean-Pierre Luminet of the Observatoire de Paris-Meudon, France, say the strain of these tidal forces can also trigger a nuclear explosion powerful enough to destroy the star from within. They carried out computer simulations of the final moments of such an unfortunate star’s life, as it penetrates deeply into the tidal field of a massive black hole.

When the star gets close enough the black hole (without falling into), the tidal forces flatten it into a pancake shape. Previous studies already performed by Luminet and collaborators twenty years ago had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart. But other studies had suggested that the picture would be complicated by shock waves generated during the flattening process, and that no nuclear explosion should occur.

The new simulations investigate the effects of shock waves in detail, and find that even when their effects are included, the conditions favour a nuclear explosion which will completely destroy the star, and which will be powerful enough to hurl much of the star’s matter out of the black hole’s reach.

Stellar fireworks

The tidal disruption of stars by black holes may already have been observed by X-ray telescopes such as GALEX, XMM and Chandra, although at a much later stage : several months after the event that rips the star apart, its matter starts swirling into the hole, heats up and releases ultraviolet light and X-rays. However, if pancake stars really do explode, then they could in principle allow these events to be detected at a much earlier stage. Future observatories, such as the Large Synoptic Survey Telescope (LSST), which will detect large numbers of supernovae, could turn up some explosions of this type.

But this might be not the only hazard facing the doomed star. Brassart and Luminet calculated that the shock waves inside the stellar pancake carry a brief (< 0.1 s) but very high (above 10^9 K) peak of temperature outwards from the centre to the surface of the star. This last result is very promising since it could give rise to a new type of X-ray or gamma-ray burst, making it possible to see the disruption of the star immediately if it gets hot enough.

The rate of such "flambeed pancake stars" is estimated to about 0.00001 event per galaxy. Since almost every galaxy – including our own Milky Way – harbors a massive black hole in its centre, and since the universe is transparent to hard X and gamma radiation, several events of this kind per year should be detectable within the full observable universe.

Conclusion

The planned high-energy, all-sky surveys are the best suited to detect more flares of this type because of their large sky coverage. By providing a quick localization of flambeed stellar pancakes, followed by the detection of the corresponding afterglows in the optical, infrared, and radio bands, these missions could bring as much to the understanding of stellar disruptions by black holes as the Beppo-Sax and Swift telescopes did for the comprehension of gamma-ray bursts.

Journal reference: Shock Waves in Tidally Compressed Stars by Massive Black Holes,

Understanding Stellar Explosions Is Less Straightforward Than Previously Thought

2009-05-18T01:09:00.001-07:00

Stellar explosions called novæ are caused by nuclear reactions between the star's atoms. In order to better understand such violent phenomena, astrophysicists study the radiation emitted by certain types of atom, and in particular the fluorine-18 produced by these reactions. Now, researchers at GANIL ,in collaboration with teams from the UK, Belgium, Romania and France, have determined that fluorine-18 appears to be less abundant than expected.This discovery therefore reduces the chances of observing the radiation emitted by this atom. It implies new constraints for the observation and understanding of novæ.

Observed since ancient times, novæ are stellar explosions which occur in our galaxy around 20 times a year. Today, physicists think that they take place in stellar binary systems, which are made up of two stars, a red giant and a small, hot companion called a white dwarf. "Matter is torn off the red giant and falls onto the surface of the white dwarf," explains François de Oliveira Santos, a physicist working at GANIL. "This stellar matter accumulates on the surface of the white dwarf, leading to an increase in its temperature and density. A number of nuclear reactions, transforming one or more atomic nuclei into other particles, then take place: stable atomic nuclei (carbon, oxygen, etc) in the star are transformed into radioactive nuclei, such as fluorine-18." It is by observing the radiation emitted by these particles that researchers hope to better understand the physical processes taking place during novæ.

Fluorine-18 is a radioactive atom whose unstable nucleus is deficient in neutrons compared to its stable form, fluorine-19. When it disintegrates, fluorine-18 emits specific electromagnetic radiation that astrophysicists study in order to get a better understanding of what goes on inside novæ. "The amount of radiation emitted during the explosion depends on the amount of fluorine-18 present," de Oliveira Santos explains. In order to show this, researchers have tried to identify all the nuclear reactions that lead to the creation and destruction of fluorine-18. Since these reactions depend on the structure of the nuclei, they have been studied with the use of particle accelerators.

An experiment carried out at Louvain-la-Neuve University in Belgium, as part of an international collaboration, has led scientists to revise downwards their estimate of the amount of fluorine-18 present in novae. The conclusion is that nuclear reactions involving fluorine-18 in these explosions lead to its destruction to a greater degree than had previously been estimated. "Our result is in agreement with recent theoretical work," de Oliveira Santos points out. "We obtained this result thanks to a new experimental technique that uses beams of accelerated radioactve nuclei." It leads to new constraints for the observation and understanding of stellar explosions.