Chandra Sees Colliding Galaxies

Image credit: Chandra

The Chandra X-Ray Observatory has found rich deposits of neon, magnesium and silicon in a pair of colliding galaxies called The Antennae, located 30 million light-years away. When these hot clouds eventually cool, they’ll serve as enormous nurseries for newborn stars. Astronomers are interested in this collision because it’s very similar to what will happen when the Milky Way and Andromeda galaxies collide in about 3 billion years.

NASA’s Chandra X-ray Observatory has discovered rich deposits of neon, magnesium, and silicon in a pair of colliding galaxies known as The Antennae. When the clouds in which these elements are present cool, an exceptionally high number of stars with planets should form. These results may foreshadow the fate of the Milky Way and its future collision with the Andromeda Galaxy.

“The amount of enrichment of elements in The Antennae is phenomenal,” said Giuseppina Fabbiano of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. at a press conference at a meeting of the American Astronomical Society in Atlanta, Ga. “This must be due to a very high rate of supernova explosions in these colliding galaxies.” Fabbiano is lead author of a paper on this discovery by a team of U.S. and U.K. scientists that will appear in an upcoming issue of The Astrophysical Journal Letters.

When galaxies collide, direct hits between stars are extremely rare, but collisions between huge gas clouds in the galaxies can trigger a stellar baby boom. The most massive of these stars race through their evolution in a few million years and explode as supernovas. Heavy elements manufactured inside these stars are blown away by the explosions and enrich the surrounding gas for thousands of light years.

“The amount of heavy elements supports earlier studies that indicate there was a very high rate of relatively recent supernovas, 30 times that of the Milky Way,” according to collaborator Andreas Zezas of the CfA.

The supernova violence also heats the gas to millions of degrees Celsius. This makes much of the matter in the clouds invisible to optical telescopes, but it can be observed by an X-ray telescope. Chandra data revealed for the first time regions of varying enrichment in the galaxies ? in one cloud magnesium and silicon are 16 and 24 times as abundant as in the Sun.

“These are the kinds of elements that form the ultimate building blocks for habitable planets,” said Andrew King of the University of Leicester, U.K. and a coauthor of the study. “This process occurs in all galaxies, but it is greatly enhanced by the collision. Usually we only see the new elements in diluted form as they are mixed up with the rest of the interstellar gas.”

CfA coauthor Alessandro Baldi commented that, “This is spectacular confirmation of the idea that the basis of chemistry, of planets, and ultimately of life is assembled inside stars and spread through galaxies by supernova explosions,”

As the enriched gas cools, a new generation of stars will form, and with them new planets. A number of studies indicate that clouds enriched in heavy elements are more likely to form stars with planetary systems, so in the future an unusually high number of planets may form in The Antennae.

“If life arises on a significant fraction of these planets, then in the future the Antennae will be teeming with life,” speculated Francois Schweizer, another coauthor who is from the Carnegie Observatories in Pasadena, Calif. “A vast number of Sun like stars and planetary systems will age in unison for billions of years.”

At a distance of about 60 million light years, The Antennae system is the nearest example of a collision between two large galaxies. The collision, which began a couple of hundred million years ago, has been so violent that gas and stars from the galaxies have been ejected into the two long arcs that give the system its name. The Chandra image shows spectacular loops of 3-million-degree gas spreading out south of the antennae. “These loops may be carrying out some of the elements dispersed by supernovas into intergalactic space,” said Trevor Ponman of Birmingham University, U.K.

The Antennae give a closeup view of the type of collisions that were common in the early universe and likely led to the formation of most of the stars that exist in the universe today. They may also provide a glimpse of the future of our Milky Way Galaxy, which is on a collision course with the Andromeda Galaxy. At the present rate, a crash such as the one now occurring in the Antennae could happen in about 3 billion years. Tremendous gravitational forces will disrupt both galaxies and reform them, probably as a giant elliptical galaxy with hundreds of millions of young Sun like stars, and possibly planetary systems.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., 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.

Original Source: Chandra News Release

Stardust Heads for Home

Image credit: NASA/JPL

Now that it’s survived its dangerous journey through the tail of Comet Wild-2, NASA’s Stardust spacecraft is heading for home. On board is its precious cargo of comet fragments that will be returned to Earth in 2006 for analysis by scientists. Even though the spacecraft’s camera was only really designed for navigation, it took 72 photographs which are some of the best images of a comet ever taken. Scientists hope that the cometary particles will help answer questions about the earliest history of our solar system.

Having weathered its out-of-this-world sandblasting by cometary particles hurtling toward it at about six times the speed of a rifle bullet, NASA’s Stardust spacecraft begins its two-year, 1.14 billion kilometer (708 million mile) trek back to its planet of origin.

“On January 2, comet Wild 2 gave up its particles but it did not do so without a fight,” said Stardust Project Manager Tom Duxbury of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Our data indicates we flew through sheets of cometary particles that jostled the spacecraft and that on at least 10 occasions the first layer of our shielding was breeched. Glad we had a couple more layers of the stuff.”

Stardust entered the comet’s coma ? the vast cloud of dust and gas that surrounds a comet’s nucleus – on December 31, 2003. From that point on it kept its defensive shielding between it and what scientists hoped would be the caustic stream of particles it would fly through. And fly through cometary particles Stardust did, but not in the fashion the team envisioned while designing the mission.

“We thought we would see a uniform increase in the number of particles the closer we came to the comet’s nucleus and then a reduction,” said University of Washington scientist Dr. Don Brownlee, Stardust’s Principal Investigator. “Instead, our data indicate we flew through a veritable swarm of particles and then there would be almost nothing and then we would fly through another swarm.”

Stardust scooped up these cometary particles, impacting at 6.1 kilometers per second (3.8 miles per second), for almost instantaneous analysis from onboard instruments and stored other particles for later, in-depth analysis, here on Earth. Along with this cosmic taste testing, the spacecraft also took some remarkable images of comet Wild 2’s five-kilometer wide (3.1- mile wide) nucleus.

“Our navigation camera was designed to assist in navigation, not science,” said Stardust’s imaging team lead Ray Newburn. “But these are the best images ever taken of a comet and there is a remarkable amount of information in those 72 pictures. Not only did we image the jets of material spewing out from the comet, but for the first time in history we can actually see the location of their origin on the surface of the comet.”

At about 11:25 am Pacific Standard Time (2:25pm EST) on Jan. 2, only minutes after its closest approach with the comet, Stardust pointed its high gain antenna at Earth and began transmitting a data stream that took over 30 hours to send but will keep cometary scientists busy for years to come. About six hours later another event took place that goes a long way to literally increasing the scientists task load exponentially.

“Six hours after encounter we retracted the collector grid, with what we are all confident is an abundance of cometary particles, into the spacecraft’s sample return capsule,” added Duxbury. “The next time the sample return capsule is going to be opened is in a clean room at the Johnson Space Center in the days following Earth return in January 2006.”

Scientists expect in-depth terrestrial analysis of the samples will reveal much about comets and the earliest history of the solar system. Chemical and physical information locked within the particles could be the record of the formation of the planets and the materials from which they were made. More information on the Stardust mission is available at

Stardust, a part of NASA’s Discovery Program of low-cost, highly focused science missions, was built by Lockheed Martin Space Systems, Denver, Colo., and is managed by JPL for NASA’s Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology in Pasadena.

Original Source: NASA/JPL News Release

Mars Express Fails to Communicate with Beagle 2

Image credit: ESA

The first opportunity for Mars Express to hear from Beagle 2 has come and gone, and so far, there’s just silence. The spacecraft passed over the anticipated landing area Tuesday, at 1213 UTC (7:13 am EST) and attempted to make contact with the lander. Several more attempts are planned for the coming days, and now that Mars Express has reached its operational orbit, there should be plenty of opportunities to hear from Beagle 2 if it’s still intact on the surface of Mars.

ESA?s Mars Express orbiter made its first attempt to establish contact with the Beagle 2 lander, after the two spacecraft separated on 19 December 2003.

The orbiter made its first pass over the Beagle 2 landing site today at 13:13 CET, but could not pick up any signal from the tiny lander. More attempts to contact Beagle 2 are planned in the days to come.

Beagle 2 was released on 19 December on a course towards the Red Planet by Mars Express, the mothership for the 400 million kilometre interplanetary cruise. Six days later it entered the Martian atmosphere and should have landed on the near-equatorial site of Isidis Planitia.

Since then, attempts to communicate with the lander through NASA?s Mars Odyssey orbiter and radio telescopes on Earth have been unsuccessful.

The Mars Express orbiter successfully entered Mars orbit at about the same time as Beagle 2?s landing. Then, in early January, it made a series of planned manoeuvres to change its equatorial orbit to a polar one, to prepare for its scientific mission and to make contact with Beagle 2.

Unlike Mars Odyssey and the radio telescopes, Mars Express has a communication system that was fully tested to contact Beagle 2, which gives ESA more confidence of picking up the signal in the coming days.

?We have not lost hope yet to contact Beagle 2, but we also know that it has landed on an unforgiving planet,? said David Southwood, ESA?s Director of Science.

?There are still opportunities to make contact with Beagle in the days to come, and we are giving our best efforts. Nevertheless, our spacecraft Mars Express has now reached its operational orbit and is working well; I know the science community is eagerly waiting for its first results.?

Original Source: ESA News Release

Spirit’s First Colour Photo of Mars

Well, here it is, the picture we’ve all been waiting for – the first colour image from the surface of Mars taken by Spirit. I can’t believe the resolution this rover has. I’ve taken a big chunk of the image and processed it to be a 1280 x 1024 wallpaper. To set this image as your desktop wallpaper, click the following link, and then right-click anywhere in the image and select “Set as Wallpaper”.

Click here to download the first colour image of Mars taken by Spirit. (156 KB)

If you want to access the original, high-resolution image from NASA, click here instead. I’ll warn you, though, it’s more than 4 MB… and that’s just the medium resolution version.


Fraser Cain
Universe Today

Biggest Stars Often Have Companions

Image credit: Hubble

New research from the Hubble Space Telescope indicates that the majority of large dying Wolf-Rayat stars have a smaller companion star orbiting nearby. This discovery will help astronomers understand how these unique stars evolve in the Universe, and could provide new a new method to estimate their size. Wolf-Rayat stars start out at least 20 times the mass of the Sun, last only a few million years, and then explode as supernovae. It’s now believed that these stars and their companions transfer mass as they orbit one another.

The majority of massive and brilliant but dying “Wolf-Rayet” stars have company – a smaller companion star orbiting nearby, according to new observations using the Hubble Space Telescope. The result will help astronomers understand how the biggest stars in the Universe evolve. It may also resolve the mystery of impossibly massive stars, and calls into question a certain kind of distance estimate that uses the apparent brightness of starlight.

Wolf-Rayet (WR) stars begin life as cosmic titans, with at least 20 times the mass of the Sun. They live fast and die hard, exploding as supernova and blasting vast amounts of heavy elements into space for use in later generations of stars and planets. “I tell people I study the stars that made a lot of the carbon in their bodies and the gold in their jewelry,” says Dr. Debra Wallace of NASA’s Goddard Space Flight Center, Greenbelt, Md. “Understanding how Wolf-Rayet stars evolve is a critical link in the chain of events that ultimately led to life.” Wallace is lead author of papers on this research to be published in the Astronomical Journal and the Astrophysical Journal.

By the time these stars are near the end of their brief lifetimes, during the “Wolf-Rayet” phase, they are fusing heavy elements in their cores in a frantic bid to prevent collapsing under their own immense mass. This generates intense heat and radiation that drives fierce, 2.2 million to 5.4 million mile-per-hour (3.6 million to 9 million km/hr) stellar winds characteristic of WR stars (Image 1). These winds blow off the outer layers of WR stars, greatly reducing their mass and compressing nearby interstellar clouds, triggering their gravitational collapse and igniting a new generation of stars.

Because cosmic distances are so great, what appears as a single star even when viewed through large telescopes (Image 2) may in fact be two or more stars orbiting each other (Images 3 and 4). In the new research, Wallace and her team used the superior resolving power of the Planetary Camera in the Wide-Field Planetary Camera 2 instrument on board Hubble to identify new potential companion stars for 23 of 61 WR stars in our galaxy. Although the apparent companion stars need to be confirmed with a light-analysis technique called spectroscopy, the team was conservative in declaring nearby stars companions.

“The portion of Wolf-Rayet stars having visually identified companion stars zoomed from 15 percent before Hubble to 59 percent with our observations, which included a quarter of the known WR stars in our galaxy,” said Wallace. “I wouldn’t be surprised if future observations reveal companions around an even greater percentage of them.”

The presence of a companion star should significantly influence how these stars evolve, according to the team. One of many possible influences is mass transfer. If the stars come close together at some point in their orbits, their gravitational interaction could cause one to transfer gas to the other, significantly altering their masses over time. Since more massive stars use up their fuel much faster than less massive stars, such a mass transfer could significantly change their lifetimes. Other influences include altering orbits, rotation rates, or mass-loss rates through the pull of their gravity, and the impact of stellar winds. “Astronomers assumed Wolf-Rayet stars were single when trying to calculate how they evolve, but we are finding most have company,” said Wallace. “It’s like thinking married life will be the same as life as a bachelor. A companion star has got to change the life of these stars somehow.”

Since what is seen as one star may in fact be two or even more, stupendous mass estimates of more than a hundred times that of the Sun for certain stars may have to be revised downward. “This actually helps clear up an apparent mystery, because astronomers believe there is a limit to how big a star can be,” said Wallace. “The more massive a star, the faster it consumes its fuel and the brighter it shines. Above about 100 solar masses, a star should essentially blow itself apart through its intense radiation.”

The result also makes a common technique for estimating distances to these stars more uncertain. To get a distance estimate to a star, one gets the spectral type of the star, an analysis of the star’s light that reveals its unique characteristics, like a fingerprint. For a given spectral type, one knows the star’s average absolute luminosity (how bright it would be if it were a certain distance – 32.6 light-years – away). By measuring its apparent luminosity (how bright it appears to be at its actual, but unknown, distance), one can then use the relationship between its apparent and absolute luminosity to determine the actual distance. If there are really two (or more) stars there that you don’t see, the WR star will appear to be brighter than it should for its spectral type and real distance, causing the distance to be misestimated.

The team includes Wallace; Dr. Douglas R. Gies of the Department of Physics and Astronomy, Georgia State University, Atlanta, Ga.; Anthony F. J. Moffat, D?partement de Physique, Universit? de Montr?al, Quebec, Canada; and Michael M. Shara, Department of Astrophysics, American Museum of Natural History, New York, N.Y. The research was funded by NASA.

Original Source: NASA News Release

Most Luminous Star Discovered

Image credit: University of Florida

A team of astronomers from the University of Florida have found what could be the brightest star ever seen in the Universe. Located 45,000 light years away across our galaxy, LBV 1806-20 could be 40 million times brighter and 150 times larger than our own Sun. This gigantic and bright star isn’t long for the Universe; however, it’s only a couple of million years old, and will blow up as a supernova in a few million more. This star defies current theories about how large stars should be able to get.

A University of Florida-led team of astronomers may have discovered the brightest star yet observed in the universe, a fiery behemoth that could be as much as much as seven times brighter than the current record holder.

But don?t expect to find the star — which is at least 5 million times brighter than the sun — in the night sky. Dust particles between Earth and the star block out all of its visible light. Whereas the sun is located only 8.3 light minutes from Earth, the bright star is 45,000 light years away, on the other side of the galaxy. It is detectable only with instruments that measure infrared light, which has longer wavelengths that can better penetrate the dust.

In a National Science Foundation-funded study scheduled to be presented today at the American Astronomical Society national conference in Atlanta, the team says the star is at least as bright as the Pistol Star, the current record holder, so named for the pistol-shaped nebula surrounding it. Whereas the Pistol Star is between 5 million and 6 million times as bright as the sun, however, the new contender, LBV 1806-20, could be as much as 40 million times the sun?s brightness.

?We think we?ve found what may be the most massive and most luminous star ever discovered,? said Steve Eikenberry, a UF professor of astronomy and the lead author of a paper on the discovery that was recently submitted to the Astrophysical Journal.

Eikenberry will discuss his findings in a news conference to be held by the society at 12:30 p.m. today at the Courtland Room in the Hyatt Regency Atlanta, where the conference is being held.

One longstanding problem with gauging the brightness of stars at great distances is that what seems at first to be one amazingly bright star turns out on closer examination to be a cluster of nearby stars. Don Figer, an astronomer at the Baltimore-based Space Telescope Science Institute who led the team that discovered the Pistol Star in 1997, said the high-quality data collected by the UF-led team reduced but did not eliminate this possibility.

?The high-resolution data prove that the object is not simply a cluster of lower mass stars, although it is possible that it is a collection of a few stars in a tight orbit around each other,? Figer said. ?More study will be needed to determine the distance and singularity of the object in order to establish whether the object is truly the most massive star known.?

Astronomers have known about LBV 1806-20 since the 1990s. At that time, it was identified as a ?luminous blue variable star? – a relatively rare, massive and short-lived star. Such stars get their names from their propensity to display light and color variability in the infrared spectrum.

Luminous blue variable stars are extremely large, with LBV 1806-20 probably at least 150 times larger than the sun, Eikenberry said. The stars are also extremely young by stellar time. LBV 1806-20 is estimated at less than 2 million years old. The sun in our solar system, by contrast, is 5 billion years old. Typical stars, such as the sun, live 10 billion years.

LBVs have ?short and troubled lives,? as Eikenberry put it, because ?the more mass you have, the more nuclear fuel you have, the faster you burn it up. They start blowing themselves to bits.?

Eikenberry?s team made several key advances that led to the estimate of the star?s oversized mass and brightness, he said.

One, they sharpened infrared images obtained from the Palomar 200-inch telescope at the California Institute of Technology?s Palomar Observatory using a camera equipped with ?speckle imaging,? a relatively new technology for improving resolution of objects at great distances.

?The shimmering that you see coming off a hot blacktop road in the summer – the upper atmosphere kind of does that with star light,? Eikenberry said. ?Speckle imaging kind of freezes that motion out, and you get much better images.?

Composed of 17 astronomers and graduate students, the team also came up with an accurate estimate for the distance from the Earth to the bright star. Team members further determined its temperature and how much of the star?s infrared light gets absorbed by dust particles as the light makes its way toward Earth. The scientists relied on data collected by the Blanco 4-meter telescope at the National Optical Astronomy Observatory?s Cerro Tololo Inter-American Observatory in Chile.

Each of these variables contributed to the estimate of the star?s remarkable candlepower. ?You correct for dust absorption, then you correct for temperature of the star, you correct for distance of the star – all of those things feed into luminosity,? Eikenberry said.

One of the mysteries about LBV 1806-20 is how it got so big. Current theories of star formation suggest they should be limited to about 120 solar masses, or 120 times as large as the sun, because the heat and pressure from such big stars? cores force matter away from their surfaces. Eikenberry said one possibility is that the big star was formed in a process called shock-induced star formation, which occurs when a supernova blows up and slams the gaseous material in a molecular cloud together into a massive star.

The star?s size is not its only distinguishing characteristic. It is located in a small cluster of highly unusual or extremely rare stars, including a so-called ?soft gamma ray repeater,? a freakishly magnetic neutron star that is one of only four identified in the entire galaxy of 100 billion stars. With a magnetic field hundreds of trillions of times more powerful than Earth?s magnetic field, this type of star gets its name from its periodic bursts of gamma rays. The cluster also apparently includes an infant or newly formed star.

?We?ve got this zoo of freak stars, all crammed together, really nearby, and they?re all part of the same cluster of stars,? Eikenberry said. ?It?s really kind of weird.?

Also buried within the cluster is an extremely young infant star, Eikenberry said. The presence of the infant star, the luminous blue variable and the soft gamma ray repeater are vivid examples of an important emerging fact about stellar evolution: All stars in a single cluster don?t form at the same time, he said. ?We?re seeing what I think is going to become a textbook example of the fact that stars aren?t all born in an instant, even in a small cluster,? he said.

Figer, the Pistol Star discoverer, said the research makes an important contribution to astronomers? understanding of the star formation process.

?The findings are significant because such massive stars are very rare and define the upper limits of the star formation process,? he said. ?The team has made a remarkable contribution to our understanding of the most extreme stars.?

The team carrying out this work also included UF?s Jessica LaVine; Keith Matthews, with the California Institute of Technology; Stephane Corbel, with the Universite de Paris; John-David Smith, with the University of Arizona; John Wilson, with the University of Virginia; Donald Barry, Michael Colonno and James Houck, all with Cornell University; and undergraduate research students Shannon Patel, Malia Jackson, and Dounan Hu of Cornell University; and Megan Garske of Northwestern Nazarene University.

Original Source: University of Florida News Release

Galaxy Shreds as it Collides With a Cluster of Galaxies

Image credit: Chandra

A new image from the Chandra X-Ray Observatory shows a distant galaxy that used to look like our own Milky Way crashing into a cluster of galaxies at 7.5 million kilometers per hour. The force of this collision is so strong that the ambient hydrogen in the galaxy is being stripped away, leaving only the skeletal spiral arms. Without hydrogen, new star formation in the galaxy has come to a stop. Although galaxy collisions have been seen before, this is the most swift and violent one ever seen.

Trailing 200,000-light-year-long streamers of seething gas, a galaxy that was once like our Milky Way is being shredded as it plunges at 4.5 million miles per hour through the heart of a distant cluster of galaxies. In this unusually violent collision with ambient cluster gas, the galaxy is stripped down to its skeletal spiral arms as it is eviscerated of fresh hydrogen for making new stars.

The galaxy’s untimely demise is offering new clues to solving the mystery of what happens to spiral galaxies in a violent universe. Views of the early universe show that spiral galaxies were once much more abundant in rich clusters of galaxies. But they seem to have been vanishing over cosmic time. Where have these “missing bodies” gone?

Astronomers are using a wide range of telescopes and analysis techniques to conduct a “CSI” or Crime Scene Investigator-style look at what is happening to this galaxy inside its cluster’s rough neighborhood. “It’s a clear case of galaxy assault and battery,” says William Keel of the University of Alabama. “This is the first time we have a full suite of results from such disparate techniques showing the crime being committed, and the modus operandi.”

Keel and colleagues are laying out the “forensic evidence” of the galaxy’s late life, in a series of presentations today in Atlanta, Ga., at the 203rd meeting of the American Astronomical Society. Astronomers have assembled the evidence by combining a variety of diagnostic observations from telescopes analyzing the galaxy’s appearance in X-ray, optical, and radio light. Parallel observations at different wavelengths trace how stars, gas, and dust are being tossed around and torn from the fragile galaxy, called C153. Though such “distressed” galaxies have been seen before, this one’s demise is unusually swift and violent. The galaxy belongs to a cluster of galaxies that slammed into another cluster about 100 million years ago. This galaxy took the brunt of the beating as it fell along a trajectory straight through the dense core of the colliding cluster.

“This helps explain the weird X-ray and radio emissions we see,” says Keel. “The galaxy is a laboratory for studying how gas can be stripped away when it flies through the hot cluster gas, shutting down star birth and transforming the galaxy.”

The first suggestion of galactic mayhem in this cluster came in 1994 when the Very Large Array radio telescope near Socorro, N.M., detected an unusual number of radio galaxies in the cluster, called Abell 2125. Radio sources trace both star formation and the feeding of central black holes in galaxy clusters. The radio observations also showed that C153 stood out from the other galaxies as an exceptionally powerful radio source.

Keel’s team began an extensive program of further observations to uncover details about the galaxies. “This was designed to see what the connection could possibly be between events on the 10-million-light-year scale of the cluster merger and what happens deep inside individual galaxies,” says Keel.

X-ray observations from the ROSAT satellite (an acronym for the Roentgen Satellite) demonstrated that the cluster contains vast amounts of 36-million-degree Fahrenheit (20-million-degree Kelvin) gas that envelops the galaxies. The gas is concentrated into two main lumps rather than smoothly distributed across the cluster, as is more commonly the case.

This bolstered the suspicion that two galaxy clusters are actually colliding. In the mid-to-late 1990s astronomers turned the Mayall 4-meter telescope and the WIYN 3.5-meter telescope at the Kitt Peak National Observatory on the cluster to analyze the starlight via spectroscopy. They found many star-forming systems and even active galactic black holes fueled by the collision. The disintegrating galaxy C153 stood out dramatically when the KPNO telescopes were used to photomap the cluster in color.

Astronomers then trained NASA’s Hubble Space Telescope (HST) onto C153 and resolved a bizarre shape. They found that the galaxy looks unusually clumpy with many young star clusters and chaotic dust features. Besides the disrupted features in the galaxy’s disk, HST also showed that the light in the tail is mostly attributed to recent star formation, providing a direct link to the stripping of the galaxy as it passed through the cluster core. Gas compressed along the galaxy’s leading edge, like snow before a plow, ignited a firestorm of new star birth. Evidence of recent star formation also comes from the optical spectrum obtained at the 10-meter Gemini North telescope in Hawaii. The spectrum allows the researchers to estimate the time since the most recent burst of star formation.

This conclusion was further bolstered when the Mosaic camera on Kitt Peak’s Mayall telescope found a very long tail of extended gas coming off the galaxy. The tail was apparently generated in part by a hurricane of stellar winds boiling off the new star-birth regions and being blown backwards as the galaxy streaks through the surrounding hot gas of the cluster.

Spectroscopic observations with the Gemini telescope allowed astronomers to age-date the starburst. They find that 90 percent of C153’s blue light is from a population of stars that are 100 million years old. This age corresponds to the time the galaxy should have gone careening through the densest gas in the cluster core.

The Gemini spectroscopic observations show the stars are in a regular pattern of orbital motion around the center, as usual for disk galaxies. However, there are multiple widespread clouds of gas moving independently of the stars. “This is an important clue that something beyond gravitational forces must be at work, since stars and gas respond the same way to purely gravitational forces,” says Keel. “In other words, the galaxy’s gas doesn’t know what the stars are doing.”

NASA’s Chandra X-ray Observatory discovered that the cooler clouds detected with optical telescopes and an associated radio feature are embedded in a much larger multimillion-degree trail of gas. Chandra’s data indicate that this hot gas was probably enriched in heavy elements by the starburst and driven out of the galaxy by its supersonic motion through the much larger cloud of gas that pervades the cluster.

Collectively, these observations offer evidence that the ram pressure of external gas in the cluster is stripping away the galaxy’s own gas. This process has long been hypothesized to account for the forced evolution of cluster galaxies. Its aftermath has been seen in several ways. Some nearby examples, Seyfert’s Sextet and Stefan’s Quintet, are tight clusters that show the aftermath of high-velocity collisions.

The galaxy C153 is destined to lose the last vestiges of its spiral arms and become a bland S0-type galaxy having a central bulge and disk, but no spiral-arm structure. These types of galaxies are common in the dense galaxy clusters seen today. Astronomers plan to make new observations with Gemini again in 2004 to study the dynamics of the gas and stars in the tail.

The science team members are William Keel (University of Alabama), Frazer Owen (National Radio Astronomy Observatory), Michael Ledlow (Gemini Observatory), and Daniel Wang (University of Massachusetts).

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., 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.

Original Source: Chandra News Release

Scientists Plot Spirit’s First Targets

Image credit: NASA/JPL

NASA scientists are chomping at the bit to get Spirit rolling, and they’ve already found what will probably become the rover’s first target: a nearby depression in the ground the scientists have called “Sleepy Hollow”. This shallow bowl could be an impact crater, and provide scientists with a deeper look into the structure of the Martian surface. Spirit’s next task is to extend its front wheels, which are curled up on the platform to give it a smaller size for the journey. Full colour pictures of Mars are expected later today.

“Sleepy Hollow,” a shallow depression in the Mars ground near NASA’s Spirit rover, may become an early destination when the rover drives off its lander platform in a week or so.

That possible crater and other features delighted engineers and scientists examining pictures from the Mars Exploration Rover Spirit’s first look around.

“Reality has surpassed fantasy. We’re like kids in a candy store,” said Art Thompson, rover tactical activity lead at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We can hardly wait until we get off the lander and start doing fun stuff on the surface.”

A clean bill of health from a checkout of all three science instruments on Spirit’s robotic arm fortified scientists’ anticipation of beginning to use those tools after the rover gets its six wheels onto the ground.

Also, Spirit succeeded Sunday in finding the Sun with its panoramic camera and calculating how to point its main antenna toward Earth by knowing the Sun’s position.

“Just as the ancient mariners used sextants for ‘shooting the Sun,’ as they called it, we were successfully able to shoot the Sun with our panorama camera, then use that information to point the antenna,” said JPL’s Matt Wallace, mission manger.

Within sight of Spirit are several wide, shallow bowls that may be impact craters, said Dr. Steve Squyres of Cornell University, Ithaca, New York, principal investigator for the spacecraft’s science payload. “It’s clear that while we have a generally flat surface, it is pockmarked with these things.

The mission’s scientists, who are getting little rest as they examine the pictures from Spirit, chose the name “Sleepy Hollow” for one of these circular depressions. This one is about 9 meters (30 feet) across and about 12 meters (40 feet) north of the lander, Squyres said.

“It’s a hole in the ground,” he said. “It’s a window into the interior of Mars.”

One of the next steps in preparing Spirit for rolling onto the soil is to extend the front wheels, which are tucked in for fitting inside a tight space during the flight from Earth.

Spirit arrived at Mars Jan. 3 (EST and PST; Jan. 4 Universal Time) after a seven month journey. Its task is to spend the next three months exploring for clues in rocks and soil about whether the past environment at this part of Mars was ever watery and possibly suitable to sustain life.

Spirit’s twin Mars Exploration Rover, Opportunity, will reach its landing site on the opposite side of Mars on Jan. 25 (EST and Universal Time; Jan. 24 PST) to begin a similar examination of a site on the opposite side of the planet from Gusev Crater.

JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington. Additional information about the project is available from JPL at and and from Cornell University at

Original Source: NASA/JPL News Release

Station is Losing Air

Space officials from NASA and the Russian Space Agency have come together to try and figure out why the International Space Station is steadily losing air. They say it’s nothing serious, but so far the station has lost about 1% of its air pressure; it’s still a very safe environment for the astronauts. The astronauts now have to search the station, checking all the valves and gauges to try and determine what could be causing the leak – since the station is so large, it could take a long time. It’s believed that the leak could have started as early as December 22, 2003.

Mars Express Gets Set to Locate Beagle 2

Image credit: ESA

On January 7 and for the following three days, Mars Express will attempt to communicate with the missing Beagle 2 lander. Now that it’s modified its orbit, Mars Express will pass directly over the region that Beagle 2 was thought to have landed. Previous attempts to reach the lander have been unsuccessful; however, Mars Express and Beagle 2 have been extensively tested to communicate with one another. The first attempt will happen on January 7 at 1215 UTC (7:15 pm EST January 6). The European Space Agency will announce their results a few hours later.

As of Wednesday 7 January 2004, and for the following three days, ESA?s Mars Express orbiter will be as little as 315 kilometres above the landing area of the still-silent Beagle 2.

Since Christmas attempts to communicate with the tiny lander through NASA?s Mars Odyssey orbiter and radio telescopes on Earth have been unsuccessful. However, Mars Express and Beagle 2 are the only systems tested end-to-end, giving ESA more confidence of establishing contact with the lander in the coming days.

The Ultra High Frequency (UHF) receivers on Mars Express are ready to communicate with Beagle 2. On 7 January, at precisely 13:15 CET, ESA?s Mars Express orbiter will be in both an ideal flight path and an ideal communication configuration, right over the Beagle 2 landing area, at about 86 degrees, allowing ground controllers at ESA?s European Space Operations Centre (ESOC) in Darmstadt, Germany, to catch the slightest beep from the Martian surface.

The results of this first search attempt will be announced at a press briefing at ESA/ESOC by David Southwood, Director of Science, Rudolf Schmidt, Mars Express Project Manager, and Michael McKay, Deputy Flight Director, starting at 16:00 CET.

Original Source: ESA News Release