Astronomy blog

July 2, 2009, 10:08 PM CT

New focus on the moon

NASA's Lunar Reconnaissance Orbiter Camera (LROC) has taken and received its first images of the Moon, kicking off the year-long mapping mission of Earth's nearest celestial neighbor. The LROC imaging system, under the watchful eyes of Arizona State University professor Mark Robison, the principal investigator, consists of two Narrow Angle Cameras (NACs) to provide high-resolution black-and-white images, a Wide Angle Camera (WAC) to provide images in seven color bands over a 60-kilometer (37.28-mile) swath, and a Sequence and Compressor System (SCS) supporting data acquisition for both cameras.

NASA reports that the Lunar Reconnaissance Orbiter, which launched June 18, is performing exceptionally well and spacecraft checkout is proceeding smoothly, so smoothly in fact that LROC was given an early, but short (two orbits) opportunity Tuesday evening to measure temperatures and background values while imaging. Since LRO is in a terminator orbit, much of the area photographed was in shadows, which is actually a good situation for performing engineering checks of camera settings, as per Robinson, with ASU's School of Earth and Space Exploration. Much to the delight of the LROC team, a few of the images captured dramatic views of the surface.

"Our first images were taken along the Moon's terminator the dividing line between day and night making us initially unsure of how they would turn out," says Robinson. "Because of the deep shadowing, subtle topography is exaggerated suggesting a craggy and inhospitable surface. In reality, the area is similar to the region where the Apollo 16 astronauts comfortably explored in 1972. Though these images are magnificent in their own right, the main message is that LROC is nearly ready to begin its mission"......... Posted by: Sean      Read more         Source

June 16, 2009, 5:11 AM CT

Meteorite grains divulge Earth's cosmic roots

The interstellar stuff that became incorporated into the planets and life on Earth has younger cosmic roots than theories predict, as per the University of Chicago postdoctoral scholar Philipp Heck and his international team.

of colleagues.

Heck and colleagues examined 22 interstellar grains from the Murchison meteorite for their analysis. Dying sun-like stars flung the Murchison grains into space more than 4.5.

billion years ago, before the birth of the solar system. Researchers know the grains formed outside the solar system.

because of their exotic composition.

"The concentration of neon, produced during cosmic-ray irradiation, allows us to determine the time a grain has spent in interstellar space," Heck said. His team determined that 17 of the grains spent somewhere between three million and 200 million years in interstellar space, far less than the theoretical estimates of approximately 500 million years. Only.

three grains met interstellar duration expectations (two grains yielded no reliable age).

"The knowledge of this lifetime is essential for an improved understanding of interstellar processes, and to better contain the timing of formation processes of the solar system," Heck.

said. A period of intense star formation that preceded the sun's birth may have produced large quantities of dust, thus accounting for the timing discrepancy, as per the......... Posted by: Sean      Read more         Source

June 10, 2009, 9:37 PM CT

Planet-forming disk orbiting twin suns

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

These findings are being presented by UCLA graduate student David Rodriguez in a press conference at the American Astronomical Society meeting in Pasadena, Calif.

"It's a case of seeing is believing," says Joel Kastner of the Rochester (NY) Institute of Technology, the lead scientist on the study. "We had the first evidence for this rotating disk in radio telescope observations of V4046 Sagittarii that we made last summer. But at that point, all we had were molecular spectra, and there are different ways to interpret the spectra. Once we saw the image data from the SMA, there was no doubt that we have a rotating disk here".

Co-author David Wilner of the Harvard-Smithsonian Center for Astrophysics (CfA) adds, "This is good evidence that planets can form around binary stars, which expands the number of places we can look for extrasolar planets. Somewhere in our galaxy, an alien world may enjoy double sunrises and double sunsets"......... Posted by: Sean      Read more         Source

May 22, 2009, 5:23 AM CT

Victoria Crater unveils more of Mars' geologic past

After thoroughly investigating Victoria Crater on Mars for two years, the instruments aboard the Rover Opportunity reveal more evidence of our neighboring red planet's windy, wet and wild past. The overview of the findings compiled in one source is reported in the latest issue of the journal Science (May 22, 2009).

Opportunity's two-year exploration of Victoria Crater a half-mile wide and 250 feet deep yielded a treasury of information about the planet's geologic history and supported prior findings indicating that water once flowed on the planet's surface, as per Steve Squyres, Cornell professor of astronomy and the principal investigator for NASA's Mars Exploration Rover mission. The rover is now heading south toward Endeavor crater, 8.5 miles away.

A number of of those observations of hematite spheres ("blueberries"), sulfate-rich sandstone and small chunks of rock containing kamacite, troilite and other minerals usually found in meteorites are consistent with Opportunity's findings across Meridiani Planum. "It shows that the processes that we investigated in detail for the first time at Endurance crater [where Opportunity spent six months in 2004] are regional in scale, [indicating that] the kinds of conclusions that we first reached at Endurance apply perhaps across Meridiani," said Squyres......... Posted by: Sean      Read more         Source

May 7, 2009, 10:10 PM CT

Hubble repair mission carrying $70 million instrument

A $70 million instrument designed by the University of Colorado at Boulder to probe the evolution of galaxies, stars and intergalactic matter from its perch on the orbiting Hubble Space Telescope is on schedule for its slated May 11 launch from Kennedy Space Center in Florida aboard NASA's space shuttle Atlantis.

Originally scheduled for launch in 2004, NASA's Hubble Servicing mission has been beset by delays over the years by causes ranging from the Columbia space shuttle accident to mechanical glitches. But CU-Boulder Professor James Green of the Center for Astrophysics and Space Astronomy, principal investigator for $70 million Cosmic Origin Spectrograph, or COS, said from the Kennedy Space Center today things look very good for the launch of Atlantis next Monday at 2:01 p.m. EDT.

""There have been no hiccups this time around and everything is going very smoothly," said Green. We are right on schedule and the team is optimistic about the launch."

The telephone-booth-sized COS, built primarily by CU-Boulder's industrial partner, Ball Aerospace & Technology Corp. of Boulder, should help researchers better understand the "cosmic web" of material believed to permeate the universe, said Green. COS will gather information from ultraviolet light emanating from distant objects, allowing researchers to look back several billion years and reconstruct the physical conditions and evolution of the early universe......... Posted by: Sean      Read more         Source

April 29, 2009, 5:19 AM CT

We Owe It All to Comets

Comets have always fascinated us. A mysterious appearance could symbolize God's displeasure or mean a sure failure in battle, at least for one side. Now Tel Aviv University justifies our fascination - comets might have provided the elements for the emergence of life on our planet.

While investigating the chemical make-up of comets, Prof. Akiva Bar-Nun of the Department of Geophysics and Planetary Sciences at Tel Aviv University found they were the source of missing ingredients needed for life in Earth's ancient primordial soup. "When comets slammed into the Earth through the atmosphere about four billion years ago, they delivered a payload of organic materials to the young Earth, adding materials that combined with Earth's own large reservoir of organics and led to the emergence of life," says Prof. Bar-Nun.

It was the chemical composition of comets, Prof. Bar-Nun believes, that allowed them to kickstart life. He has published his theory widely in scientific journals, including the journal Icarus.



A Pinch of Argon, A Dash of Xenon

Using a one-of-a-kind machine built at Tel Aviv University, scientists were able to simulate comet ice, and observed that comets contain ingredients necessary for providing the basic nutrients of life......... Posted by: Sean      Read more         Source

April 23, 2009, 5:25 AM CT

Fermi Active Galaxies Ready for Their Close-Up

An international team of astronomers has used the world's biggest radio telescope to look deep into the brightest galaxies that NASA's Fermi Gamma-ray Space Telescope can see. The study solidifies the link between an active galaxy's gamma-ray emissions and its powerful radio-emitting jets.

"Now we know for sure that the fastest, most compact, and brightest jets we see with radio telescopes are the ones that are able to kick light up to the highest energies," said Yuri Kovalev, a team member at the Max Planck Institute for Radio Astronomy in Bonn, Gera number of.

The brightest galaxies Fermi sees are active galaxies, which emit oppositely directed jets of particles traveling near the speed of light. Some, called blazars, are particularly bright because one of the jets happens to be directed toward us. Astronomers think that these jets somehow arise as a consequence of matter falling into a massive black hole at the galaxy's center, but the process is not well understood.

To peer into the jets, Kovalev and colleagues used the National Science Foundation's Very Long Baseline Array (VLBA), a set of ten radio telescopes located from Hawaii to St. Croix in the U.S. Virgin Islands and operated by the National Radio Astronomy Observatory. When the signals from these telescopes are combined, the array acts like a single enormous radio dish more than 5,300 miles across. The VLBA can resolve details about a million times smaller than Fermi can and 50 times smaller than any optical telescope......... Posted by: Sean      Read more         Source

April 13, 2009, 2:03 PM CT

Challenge To Galaxy Formation Theories

A team led by an Indiana University astronomer has found a sample of massive galaxies with properties that suggest they may have formed relatively recently. This would run counter to the widely-held belief that massive, luminous galaxies (like our own Milky Way Galaxy) began their formation and evolution shortly after the Big Bang, some 13 billion years ago. Further research into the nature of these objects could open new windows into the study of the origin and early evolution of galaxies.

John Salzer, principal investigator for the study published recently in Astrophysical Journal Letters, said that the 15 galaxies in the sample exhibit luminosities (a measure of their total light output) that indicate that they are massive systems like the Milky Way and other so-called "giant" galaxies. However, these particular galaxies are unusual because they have chemical abundances that suggest very little stellar evolution has taken place within them. Their relatively low abundances of "heavy" elements (elements heavier than helium, called "metals" by astronomers) imply the galaxies are cosmologically young and may have formed recently.

The chemical abundances of the galaxies, combined with some simple assumptions about how stellar evolution and chemical enrichment progress in galaxies in general, suggest that they may only be 3 or 4 billion years old, and therefore formed 9 to 10 billion years after the Big Bang. Most theories of galaxy formation predict that massive, luminous systems like these should have formed much earlier......... Posted by: Sean      Read more         Source

March 31, 2009, 4:10 PM CT

A new X-ray spectroscopic tool

Astronomy & Astrophysics is publishing the first clear detection of signatures long sought in the spectra of X-ray astronomical sources. These signatures, the so-called EXAFS standing for "Extended X-ray Absorption Fine Structure", were observed with an X-ray spectroscopic technique that is common in materials sciences. Up to now, EXAFS studies of astronomical sources have been unsuccessful because of the weak X-ray signals received from celestial objects. Using the Reflection Grating Spectrometer (RGS) onboard the XMM-Newton satellite, Dutch astronomers C.P. de Vries and E. Costantini have obtained high-quality X-ray spectra of Scorpius X-1, one of the brightest X-ray sources in the sky, located about 2800 parsecs from the Earth. For the first time, they have found clear evidence of an EXAFS signature coming from the dust seen toward a celestial source.

EXAFS is a powerful tool for studying the structure of grains in the interstellar medium (ISM). It is based on the phenomenon that X-ray photons can eject electrons from atoms inside solid particles, which in turn can be backscattered onto the emitting atom by atoms in their immediate neighborhood. This causes characteristic sinusoidal absorption features in the X-ray spectrum of a distant source that depend on the structure of the absorbing solid material......... Posted by: Sean      Read more         Source

March 25, 2009, 9:54 PM CT

The Erratic Black Hole

New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow.

Black holes come in a number of sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars".

The newly released study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms.

This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood correlation between the disk and the radio jet seen in GRS 1915......... Posted by: Sean      Read more         Source

March 25, 2009, 9:29 PM CT

Asteroid monitored from outer space to ground impact

Reports by researchers of meteorites striking Earth in the past have resembled police reports of so a number of muggings - the offenders came out of nowhere and then disappeared into the crowd, making it difficult to get more than very basic facts.

Now an international research team has been able to identify an asteroid in space before it entered Earth's atmosphere, enabling computers to determine its area of origin in the solar system as well as predict the arrival time and location on Earth of its shattered surviving parts.

"I would say that this work demonstrates, for the first time, the ability of astronomers to discover and predict the impact of a space object," says Sandia National Laboratories researcher Mark Boslough, a member of the research team.

Perhaps more importantly, the event tested the ability of society to respond very quickly to a predicted impact, says Boslough. "In this case, it was never a threat, so the response was scientific. Had it been deemed a threat - a larger asteroid that would explode over a populated area - an alert could have been issued in time that could potentially save lives by evacuating the danger zone or instructing people to take cover."

The profusion of information in this case also helps meteoriticists learn the orbits of parent bodies that yield various types of meteorites......... Posted by: Sean      Read more         Source

March 16, 2009, 8:26 PM CT

A Curious Pair of Galaxies

Sometimes objects in the sky that appear strange, or different from normal, have a story to tell and prove scientifically very rewarding. This was the idea behind Halton Arp's catalogue of Peculiar Galaxies that appeared in the 1960s. One of the oddballs listed there is Arp 261, which has now been imaged in more detail than ever before using the FORS2 instrument on ESO's Very Large Telescope. The image proves to contain several surprises.

Arp 261 lies about 70 million light-years distant in the constellation of Libra, the Scales. Its chaotic and very unusual structure is created by the interaction of two galaxies that are engaged in a slow motion, but highly disruptive close encounter. Eventhough individual stars are very unlikely to collide in such an event, the huge clouds of gas and dust certainly do crash into each other at high speed, leading to the formation of bright new clusters of very hot stars that are clearly seen in the picture. The paths of the existing stars in the galaxies are also dramatically disrupted, creating the faint swirls extending to the upper left and lower right of the image. Both interacting galaxies were probably dwarfs not unlike the Magellanic Clouds orbiting our own galaxy.

The images used to create this picture were not actually taken to study the interacting galaxies at all, but to investigate the properties of the inconspicuous object just to the right of the brightest part of Arp 261 and close to the centre of the image. This is an unusual exploding star, called SN 1995N, that is believed to be the result of the final collapse of a massive star at the end of its life, a so-called core collapse supernova. SN 1995N is unusual because it has faded very slowly - and still shows clearly on this image more than seven years after the explosion took place! It is also one of the few supernovae to have been observed to emit X-rays. It is thought that these unusual characteristics are a result of the exploding star being in a dense region of space so that the material blasted out from the supernova ploughs into it and creates X-rays......... Posted by: Sean      Read more         Source

March 3, 2009, 6:21 AM CT

The lower atmosphere of Pluto revealed

Using ESO's Very Large Telescope, astronomers have gained valuable new insights about the atmosphere of the dwarf planet Pluto. The researchers found unexpectedly large amounts of methane in the atmosphere, and also discovered that the atmosphere is hotter than the surface by about 40 degrees, eventhough it still only reaches a frigid minus 180 degrees Celsius. These properties of Pluto's atmosphere appears to be due to the presence of pure methane patches or of a methane-rich layer covering the dwarf planet's surface.

"With lots of methane in the atmosphere, it becomes clear why Pluto's atmosphere is so warm," says Emmanuel Lellouch, main author of the paper reporting the results.

Pluto, which is about a fifth the size of Earth, is composed primarily of rock and ice. As it is about 40 times further from the Sun than the Earth on average, it is a very cold world with a surface temperature of about minus 220 degrees Celsius!.

It has been known since the 1980s that Pluto also has a tenuous atmosphere [1], which consists of a thin envelope of mostly nitrogen, with traces of methane and probably carbon monoxide. As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground. In periods when it is closer to the Sun - as it is now - the temperature of Pluto's solid surface increases, causing the ice to sublimate into gas......... Posted by: Sean      Read more         Source

February 25, 2009, 5:30 AM CT

Observing first moments of universe

During the next decade, a delicate measurement of primordial light could reveal convincing evidence for the popular cosmic inflation theory, which proposes that a random, microscopic density fluctuation in the fabric of space and time gave birth to the universe in a hot big bang approximately 13.7 billion years ago.

Among the cosmologists searching for these weak signals will be John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of Chicago. Carlstrom operates the South Pole Telescope (SPT) with a team of researchers from nine institutions in their search for evidence about the origins and evolution of the universe.

Now on their agenda is putting cosmic inflation theory to its most stringent observational test so far. The test: detecting extremely weak gravity waves, which Einstein's theory of general relativity predicts that cosmic inflation should produce.

"If you detect gravity waves, it tells you a whole lot about inflation for our universe," Carlstrom said. It also would rule out various competing ideas for the origin of the universe. "There are fewer than there used to be, but they don't predict that you have such an extreme, hot big bang, this quantum fluctuation, to start with," he said. Nor would they produce gravity waves at detectable levels......... Posted by: Sean      Read more         Source

February 16, 2009, 10:00 PM CT

The first moments of universe

During the next decade, a delicate measurement of primordial light could reveal convincing evidence for the popular cosmic inflation theory, which proposes that a random, microscopic density fluctuation in the fabric of space and time gave birth to the universe in a hot big bang approximately 13.7 billion years ago.

Among the cosmologists searching for these weak signals will be John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of Chicago. Carlstrom operates the South Pole Telescope (SPT) with a team of researchers from nine institutions in their search for evidence about the origins and evolution of the universe.

Now on their agenda is putting cosmic inflation theory to its most stringent observational test so far. The test: detecting extremely weak gravity waves, which Einstein's theory of general relativity predicts that cosmic inflation should produce.

"If you detect gravity waves, it tells you a whole lot about inflation for our universe," Carlstrom said. It also would rule out various competing ideas for the origin of the universe. "There are fewer than there used to be, but they don't predict that you have such an extreme, hot big bang, this quantum fluctuation, to start with," he said. Nor would they produce gravity waves at detectable levels......... Posted by: Sean      Read more         Source

January 26, 2009, 11:42 PM CT

Astronauts on International Space Station

Astronauts spending months in space lose significant bone strength, making them increasingly at risk for fractures during the later part of life.

UC Irvine and UC San Francisco led a study evaluating 13 astronauts who spent four to six months on the International Space Station and observed that, on average, astronauts' hipbone strength decreased 14 percent. Three astronauts experienced losses of 20 percent to 30 percent, rates comparable to those seen in older women with osteoporosis.

These results alarmed scientists because they revealed a greater rate of bone deterioration than previously measured using less powerful technologies.

"If preventive measures are not taken, some of our astronauts appears to be at increased risk for age-related fractures decades after their missions," said study leader Joyce Keyak, UCI orthopedic surgery and biomedical engineering professor.

For as long as there have been astronauts, scientists have studied why the microgravitational environment of space makes bones more fragile. While prior studies looked at bone mineral density, this study is the first to specifically evaluate bone strength.

Keyak and her colleagues used a novel computer program she developed over the past 20 years to identify hipbone fracture risk in people with osteoporosis. The study team used this program to analyze structurally the hipbone Computerized axial tomography scans of one female and 12 male International Space Center crewmembers......... Posted by: Sean      Read more         Source

January 15, 2009, 6:34 PM CT

Solving an old astronomy mystery

Researchers may have solved one of the most longstanding astrophysical mysteries of all times: How massive stars - up to 120 times the mass of our sun - form without blowing away the clouds of gas and dust that feed their growth.

New research by Lawrence Livermore National Laboratory, University of California, Santa Cruz and UC Berkeley has shown how a massive star can grow despite outward-flowing radiation pressure that exceeds the gravitational force pulling material inward. The study appears in the Jan. 15 online edition of Science Express.

Using 3-D radiation hydrodynamics simulations, the group, which includes Livermore's Richard Klein, who also is an adjunct professor at UC Berkeley, and his LLNL postdoc Andrew Cunningham, unexpectedly discovered that these massive stars also tend to occur in binary or multiple star systems.

"Originally, we were just exploring the physics of massive star formation," Klein said. "As we were looking at the physics, we observed that gravitational instabilities cause companion stars to form around massive stars".

Massive stars produce so much light that the radiation pressure they exert on the gas and dust around them is stronger than their gravitational attraction, a circumstance that has long been expected to prevent them from growing by accretion (the growth of a massive object by gravitationally attracting more matter)......... Posted by: Sean      Read more         Source

January 15, 2009, 6:30 PM CT

Mars is not a dead planet

A team of NASA and university researchers 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 main 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......... Posted by: Sean      Read more         Source

January 8, 2009, 9:55 PM CT

Looking through Galileo's eyes

In 1609, exactly four centuries ago, Galileo revolutionised humankind's understanding of our position in the Universe when he used a telescope for the first time to study the heavens, which saw him sketching radical new views of the moon and discovering the satellites orbiting Jupiter.

In synch with the International Year of Astronomy (IYA), which marks the 400th anniversary of Galileo's discoveries, a group of astronomers and curators from the Arcetri Observatory and the Institute and Museum of the History of Science, both in Florence, Italy, are recreating the kind of telescope and conditions that led to Galileo's world-changing observations, reports January's Physics World

Astronomers will be using the recreated apparatus to catalogue all the objects recorded in Galileo's 'Sidereus Nuncius' (or, in English, "Starry Messenger"), the treatise that Galileo published in 1610 which included a number of of his early observations.

The team has already observed the Moon and Saturn and are now recording images of Jupiter's moons and the phases of Venus, both of which provided crucial evidence to confirm the heliocentric hypothesis and prove that the Earth is not the centre of the Universe.

To recreate the apparatus, the team undertook a painstaking investigation of the nature of the lens of a telescope given to Galileo's patron, the Grand Duke of Tuscany, Cosimo II, in 1610. That work involved measuring the shape and refractive index of the lens, and using X-ray fluorescence to determine the condition of the glass. The group now plans to put the images seen by the telescope online. Sadly, the team has not been able to build a replica of the telescope actually used by Galileo to make the observations reported in Sidereus Nuncius as only one lens of that instrument survives......... Posted by: Sean      Read more         Source

January 8, 2009, 9:11 PM CT

How Martian winds make rocks walk

Rocks on Mars are on the move, rolling into the wind and forming organized patterns, as per new research.

The new finding counters the prior explanation of the evenly spaced arrangement of small rocks on Mars. That explanation suggested the rocks were picked up and carried downwind by extreme high-speed winds thought to occur on Mars in the past.

Images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about 5 to 7 centimeters apart on the intercrater plains between Lahontan Crater and the Columbia Hills.

Eventhough Mars is a windy planet, it would be difficult for the wind to carry the small rocks, which range in size from a quarter to a softball, said Jon D. Pelletier, associate professor of geosciences at The University of Arizona in Tucson.

Pelletier and colleagues suggest that wind blows sand away from the front of the rock, creating a pit, and then deposits that sand behind the rock, creating a hill.

The rock then rolls forward into the pit, moving into the wind, he said.

As long as the wind continues to blow, the process is repeated and the rocks move forward.

This explanation does not require extreme winds, Pelletier said.

"You get this happening five, 10, 20 times then you start to really move these things around," he said. "They can move a number of times their diameter"......... Posted by: Sean      Read more         Source

January 7, 2009, 11:50 PM CT

Asteroids with Earth-like Crust

Two rare meteorites found in Antarctica two years ago are from a previously unknown, ancient asteroid with an outer layer or crust similar in composition to the crust of Earth's continents, reports a research team primarily composed of geochemists from the University of Maryland.

Reported in the January 8 issue of the journal Nature, this is the first ever finding of material from an asteroid with a crust like Earth's. The discovery also represents the oldest example of rock with this composition ever found.

These meteorites point "to previously unrecognized diversity" of materials formed early in the history of the Solar System, write authors James Day, Richard Ash, Jeremy Bellucci, William McDonough and Richard Walker of the University of Maryland; Yang Liu and Lawrence Taylor of the University of Tennessee and Douglas Rumble III of the Carnegie Institution for Science.

Prof. James Day looking at a portion of the meteorite in the University of Maryland's isotope geochemistry lab. In the background is a mass spectrometer used to analyze the meteorite samples.

"What is most unusual about these rocks is that they have compositions similar to Earth's andesite continental crust -- what the rock beneath our feet is made of," said first author Day, who is a research scientist in Maryland's department of geology. "No meteorites like this have ever been seen before"......... Posted by: Sean      Read more         Source

January 6, 2009, 9:09 PM CT

Black Holes Lead Galaxy Growth

Astronomers may have solved a cosmic chicken-and-egg problem -- the question of which formed first in the early Universe -- galaxies or the supermassive black holes seen at their cores.

"It looks like the black holes came first. The evidence is piling up," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO). Carilli outlined the conclusions from recent research done by an international team studying conditions in the first billion years of the Universe's history in a lecture presented to the American Astronomical Society's meeting in Long Beach, California.

Earlier studies of galaxies and their central black holes in the nearby Universe revealed an intriguing linkage between the masses of the black holes and of the central "bulges" of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to a number of billions of times the mass of our Sun, the black hole's mass is about one one-thousandth of the mass of the surrounding galactic bulge.

"This constant ratio indicates that the black hole and the bulge affect each others' growth in some sort of interactive relationship," said Dominik Riechers, of Caltech. "The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process"......... Posted by: Sean      Read more         Source

January 6, 2009, 8:49 PM CT

From The Static To The Dynamic

Two new efforts have taken a famous supernova remnant from the static to the dynamic. A new movie of data from NASA's Chandra X-ray Observatory shows changes in time never seen before in this type of object. A separate team will also release a dramatic three-dimensional visualization of the same remnant.

Nearly ten years ago, Chandra's "First Light" image of Cassiopeia A (Cas A) revealed previously unseen structures and detail. Now, after eight years of observation, researchers have been able to construct a movie that tracks the remnant's expansion and changes over time.

"With Chandra, we have watched Cas A over a relatively small amount of its life, but so far the show has been amazing," said Daniel Patnaude of the Smithsonian Astrophysical Observatory in Cambridge, Mass. "And, we can use this to learn more about the aftermath of the star's explosion".

........ Posted by: Sean      Read more         Source




Older Blog Entries   1   2   3   4   5   6   7   8   9   10   11   12   13   14   15   16   17   18   19   20   21   22   23   24   25   26   27   28   29   30   31  

---