Posted on by Fraser Cain

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

Posted on by Fraser Cain

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

Posted on by Fraser Cain

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 http://marsrovers.jpl.nasa.gov and and from Cornell University at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

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.

Posted on by Fraser Cain

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

Posted on by Fraser Cain

Why Does the Early Universe Look So Mature?

Image credit: PPARC

Until now, astronomers haven’t been able to find a lot of data about what happened at an early phase in the evolution of the Universe, when it’s thought that the stars were formed. But new research, performed by astronomers using the Gemini observatory in Chile, has revealed several galaxies 8 to 11 billion years ago which are more fully formed than expected. They thought they would see protogalaxies crashing into each other, but instead they found very mature galaxies. Its possible that black holes were much more common in the early Universe and served as anchors to form galaxies rapidly.

Until now, astronomers have been nearly blind when looking back in time to survey an era when most stars in the Universe were expected to have formed. This critical cosmological blind-spot has been removed by a team, including a UK scientist, using the Frederick C. Gillett Gemini North Telescope, showing that many galaxies in the young Universe are not behaving as expected some 8-11 billion years ago.

The surprise: these galaxies appear to be more fully formed and mature than expected at this early stage in the evolution of the Universe. This finding is similar to a teacher walking into a classroom expecting to greet a room full of unruly teenagers and finding well-groomed young adults.

“Theory tells us that this epoch should be dominated by little galaxies crashing together,” said Dr. Roberto Abraham (University of Toronto) who is a Co-Principal Investigator of the team conducting the observations at Gemini. “We are seeing that a large fraction of the stars in the Universe are already in place when the Universe was quite young, which should not be the case. This glimpse back in time shows pretty clearly that we need to re-think what happened during this early epoch in galactic evolution. The theoreticians will definitely have something to gnaw on!”

The results were announced today at the 203rd meeting of the American Astronomical Society in Atlanta, Georgia. The data will soon be released to the entire astronomical community for further analysis, and four papers are nearing completion for publication in The Astrophysical Journal and The Astronomical Journal.

Dr Isobel Hook, leader of the UK Gemini Support Group, based at Oxford University, is a member of the multinational Gemini Deep Deep Survey (GDDS) team who undertook the investigation. She explains how the technique works, The team used a special technique to capture the faintest galactic light ever dissected into the rainbow of colours called a spectrum. In all, spectra from over 300 galaxies were collected, most of which are within what is called the “Redshift Desert,” a relatively unexplored period of the Universe seen by telescopes looking back to an era when the universe was only 3-6 billion years old.

She adds, These spectra represent the most complete sample ever obtained of galaxies in the Redshift Desert. By obtaining large amounts of data from four widely separated fields, this survey provides the statistical basis for drawing conclusions that have been suspected by past observations done by the Hubble Space Telescope, Keck Observatory, Subaru Telescope and the Very Large Telescope over the past decade.

Studying the faint galaxies at this epoch when the Universe was only 20-40% of its current age presents a daunting challenge to astronomers, even when using the light-gathering capacity of a very large telescope like Gemini North with its 8-metre mirror. All previous galaxy surveys in this realm have focused on galaxies where intense star formation is occurring, which makes it easier to obtain spectra but produces a biased sample. The GDDS was able to select a more representative sample including those galaxies which hold the most starsnormal, dimmer, and more massive galaxiesthat demand special techniques to coax a spectrum from their dim light.

“The Gemini data is the most comprehensive survey ever done covering the bulk of the galaxies that represent conditions in the early Universe. These are the massive galaxies that are actually more difficult to study because of their lack of energetic light from star formation. These highly developed galaxies, whose star-forming youth is in fact long gone, just shouldn’t be there, but are,” said Co-Principal Investigator Dr. Karl Glazebrook (Johns Hopkins University).

Astronomers trying to understand this issue might have to put everything on the table. “It is unclear if we need to tweak the existing models or develop a new one in order to understand this finding,” said the survey’s third Co-Principal Investigator, Dr. Patrick McCarthy (Observatories of the Carnegie Institution). “It is quite obvious from the Gemini spectra that these are indeed very mature galaxies, and we are not seeing the effects of obscuring dust. Obviously there are some major aspects about the early lives of galaxies that we just don’t understand. It is even possible that black holes might have been much more ubiquitous than we thought in the early Universe and played a larger role in seeding early galaxy formation.”

What is arguably the dominant galactic evolution theory postulates that the population of galaxies at this early stage should have been dominated by evolutionary building blocks. Aptly called the Hierarchical Model, it predicts that normal to large galaxies, like those studied in this work, would not yet exist and would instead be forming from local beehives of activity where big galaxies grew. The GDDS reveals that this might not be the case.

The spectra from this survey were also used to determine the pollution of the interstellar gas by heavy elements (called “metals”) produced by stars. This is a key indicator of the history of stellar evolution in galaxies. Sandra Savaglio (Johns Hopkins University), who studied this aspect of the research said, “Our interpretation of the Universe is strongly affected by the way we observe it. Because the GDDS observed very weak galaxies, we could detect the interstellar gas even if partly obscured by the presence of dust. Studying the chemical composition of the interstellar gas, we discovered that the galaxies in our survey are more metal-rich than expected.”

Caltech astronomer, Dr. Richard Ellis commented, “The Gemini Deep Deep Survey represents a very significant achievement, both technically and scientifically. The survey has provided a new and valuable census of galaxies during a key period in cosmic history, one that has been difficult to study until now, particularly for the quiescent component of the galaxy population.”

Making observations in the Redshift Desert has frustrated modern astronomers for the last decade. While astronomers have known that plenty of galaxies must exist in the Redshift Desert, it is only a “desert” because we couldn’t get good spectra from many of them. The problem lies in the fact that key spectroscopic features used to study these galaxies have been redshifteddue to the expansion of the Universeinto a part of the optical spectrum that corresponds to a faint, natural, obscuring glow in the Earth’s night time atmosphere.

To overcome this problem, a sophisticated technique called “Nod and Shuffle” was used on the Gemini telescope. “The Nod and Shuffle technique enables us to skim off the faint natural glow of the night sky to reveal the tenuous spectra of galaxies beneath it. These galaxies are over 300 times fainter than this sky glow,” explains Dr. Kathy Roth, an astronomer at Gemini who was also part of the team and obtained much of the data. “It has proven to be an extremely effective way to radically reduce the “noise” or contamination levels that are found in the signal from an electronic light detector.”

Each observation lasted the equivalent of about 30 hours and produced nearly 100 spectra simultaneously. The entire project required over 120 total hours of telescope time. “This is a lot of valuable time on the sky, but when you consider that it has allowed us to help fill in a crucial 20% gap in our understanding of the Universe, it was time well spent,” adds Dr. Glazebrook who developed the use of Nod and Shuffle with Joss Hawthorn for faint galaxy observations while at the Anglo-Australian Observatory a few years ago.

Previous studies in the Redshift Desert have concentrated on galaxies that were not necessarily representative of mainstream systems. For this study, galaxies were carefully selected based upon data from the Las Campanas Infrared Survey in order to assure that strong ultraviolet emitting starburst galaxies were not oversampled. “This study is unique in that we were able to study the red end of the spectrum, and this tells us about the ages of old stars,” says Dr. Abraham. “We undertook incredibly long exposures with Geminiabout ten times as long as typical exposures. This let us look at much fainter galaxies than is usually the case, and let us focus on the bulk of the stars, instead of just the flashy young ones. This makes it a lot easier for us to work out how the galaxies are evolving. We are no longer guessing at it by studying young objects and assuming the old objects were not contributing much to the story of galaxy evolution. It turns out that there are lots of old galaxies out there, but they’re really hard to find.”

Original Source: PPARC News Release

Posted on by Fraser Cain

Mars Express Lowers Its Orbit Again

Image credit: ESA

The European Space Agency’s Mars Express performed another five minute burn of its engine to change its orbit around the Red Planet. The lowest point of its orbit is now 250 km, and the high point is 40,000 km. Two more maneuvers are scheduled which will bring the spacecraft down to its final orbit by January 11. Mars Express will be in position to help search for Beagle 2 very soon. Teams from Beagle 2 and Mars Express are working through various scenarios that could explain why the lander went missing.

Today at 14:13 CET, ESA?s Mars Express spacecraft successfully executed an essential planned manoeuvre to reduce its orbit around the Red Planet.

A five-minute burn of its main engine brought Mars Express from an orbit apocentre (highest point) of 190 000 kilometres to 40 000 kilometres with a pericentre (lowest point) of about 250 kilometres.

Mars Express will reach its final operational orbit of about 11 000 kilometres by 300 kilometres towards the end of the month after two more scheduled orbit adjustments (using main engine burns) on the nights of 6/7 and 10/11 January.

Today?s key move enables ESA to pursue its Mars mission as planned. First, scheduled scientific observations can begin mid-January and, second, the search for the Beagle 2 lander will become much more accurate.

Michael McKay, Mars Express Deputy Flight Director in Darmstadt, Germany, said: ?From the second half of January 2004, the orbiter’s instruments will be prepared to scan the atmosphere, the surface and parts of the subsurface structure of Mars with unprecedented precision.

“The High Resolution Stereo Camera, for example, will take high-precision pictures of the planet and will begin a comprehensive 3D cartography of Mars. The MARSIS radar will be able to scan as far as four kilometres below the surface, looking for underground water or ice.

“Also, several spectrometers will try to unveil the mysteries of Martian mineralogy and the atmosphere, as well as influences from the solar wind or seasonal changes.?

On 7 January 2004, at 13:15 CET, the lowest point of the Mars Express flight path will be as close as 315 kilometres to the landing area of the still-silent Beagle 2.

The NASA Mars Odyssey orbiter and several radio telescopes on Earth have been unable to obtain a signal since Christmas, but chances will rise with the approach of the ‘mothership’ to its ‘baby’ Beagle 2.

Mars Express and Beagle 2 are the only end-to-end tested systems, giving ESA more confidence of establishing contact with the lander.

Today, 4 January, ESA specialists are meeting with Beagle 2 staff at ESA?s European Space Operations Centre in Darmstadt to define a strategy for modes of interaction between the ESA orbiter and the lander.

Mars Express has Ultra High Frequency (UHF) receivers ready to communicate with Beagle 2. Mars Express Project Manager Rudolf Schmidt and his ESA colleagues are very much looking forward to 7 January 2004.

Dr Schmidt said: ?At this precise time, our Mars Express orbiter is in both an ideal flight path and an ideal communication configuration, right on top of the Beagle 2 landing area, at about 86 degrees. In this situation, we should be able to discern the slightest beep from the Martian surface.?

Today?s manoeuvre was another step towards the European exploration of Mars, ensuring both orbiter operations as planned and a precise search of the Beagle 2 lander. ESA is looking forward to an exciting Mars exploration in the next months. The latest news will be posted, as always, at: at http://mars.esa.int

Original Source: ESA News Release

Posted on by Fraser Cain

Spirit Gets Ready to Explore

Image credit: NASA/JPL

With Spirit safely on the surface of Mars, engineers at NASA are starting to get a sense of the environment around it. So far, it looks like the rover couldn’t have landed in a better spot. The platform holding the rover is only tilted a few degrees, and there are no large rocks blocking the ramps. The terrain has lots of rocks to examine, but they’re well spaced out, which should let Spirit travel at a fairly high speed across the ground. Spirit will remain on the landing platform for another nine days or so before it ventures out onto search the area for evidence of past water.

NASA’s Spirit Rover is starting to examine its new surroundings, revealing a vast flatland well suited to the robot’s unprecedented mobility and scientific toolkit.

“Spirit has told us that it is healthy,” Jennifer Trosper of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., said today. Trosper is Spirit mission manager for operations on Mars’ surface. The rover remains perched on its lander platform, and the next nine days or more will be spent preparing for egress, or rolling off, onto the martian surface.

With only two degrees of tilt, with the deck toward the front an average of only about 37 centimeters (15 inches) off the ground, and with apparently no large rocks blocking the way, the lander is in good position for egress. “The egress path we’re working toward is straight ahead,” Trosper said.

The rover’s initial images excited scientists about the prospects of exploring the region after the roll-off.

“My hat is off to the navigation team because they did a fantastic job of getting us right where we wanted to be,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science payload. By correlating images taken by Spirit with earlier images from spacecraft orbiting Mars, the mission team has determined that the rover appears to be in a region marked with numerous swaths where dust devils have removed brighter dust and left darker gravel behind.

“This is our new neighborhood,” Squyres said. “We hit the sweet spot. We wanted someplace where the wind had cleared off the rocks for us. We’ve landed in a place that’s so thick with dust devil tracks that a lot of the dust has been blown away.”

The terrain looks different from any of the sites examined by NASA’s three previous successful landers — the two Vikings in 1976 and Mars Pathfinder in 1997.

“What we’re seeing is a section of surface that is remarkably devoid of big boulders, at least in our immediate vicinity, and that’s good news because big boulders are something we would have trouble driving over,” Squyres said. “We see a rock population that is different from anything we’ve seen elsewhere on Mars, and it comes out very much in our favor.”

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 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: http://marsrovers.jpl.nasa.gov and from Cornell University at: http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Stardust Sweeps Past Comet Wild 2

Image credit: NASA/JPL

The Stardust spacecraft made history today when it passed through the tail of Comet Wild-2, and took some of the best pictures of a comet ever seen. During the flyby, Stardust got within only 230 kilometers of the comet’s nucleus, and captured just a few grams of particles from Wild-2’s tail. The collected particles, which are stored in a sample return capsule, will be brought back to Earth in 2006; it’ll touchdown at a US Air Force testing range in Utah.

Team Stardust, NASA’s first dedicated sample return mission to a comet, passed a huge milestone today by successfully navigating through the particle and gas-laden coma around comet Wild 2 (pronounced “Vilt-2”). During the hazardous traverse, the spacecraft flew within about 230 kilometers (143 miles) of the comet, catching samples of comet particles and scoring detailed pictures of Wild 2’s pockmarked surface.

Closest approach was at about 19:22 Universal Time (11:22 a.m. Pacific Standard Time). The spacecraft’s radio signal was received on Earth 21 minutes and 40 seconds later, at 11:44 a.m. PST.

“Things couldn’t have worked better in a fairy tale,” said Tom Duxbury, Stardust project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

“These images are better than we had hoped for in our wildest dreams,” said Ray Newburn of JPL, a co-investigator for Stardust. “They will help us better understand the mechanisms that drive conditions on comets.”

“These are the best pictures ever taken of a comet,” said Principal Investigator Dr. Don Brownlee of the University of Washington, Seattle. “Although Stardust was designed to be a comet sample return mission, the fantastic details shown in these images greatly exceed our expectations.”

The collected particles, stowed in a sample return capsule onboard Stardust, will be returned to Earth for in-depth analysis. That dramatic event will occur on January 15, 2006, when the capsule makes a soft landing at the U.S. Air Force Utah Test and Training Range. The microscopic particle samples of comet and interstellar dust collected by Stardust will be taken to the planetary material curatorial facility at NASA’s Johnson Space Center, Houston, Texas, for analysis.

Stardust has traveled about 3.22 billion kilometers (2 billion miles) since its launch on February 7, 1999. As it closed the final gap with its cometary quarry, it endured a bombardment of particles surrounding the nucleus of comet Wild 2. To protect Stardust against the blast of expected cometary particles and rocks, the spacecraft rotated so it was flying in the shadow of its “Whipple Shields.” The shields are named for American astronomer Dr. Fred L. Whipple, who, in the 1950s, came up with the idea of shielding spacecraft from high-speed collisions with the bits and pieces ejected from comets. The system includes two bumpers at the front of the spacecraft — which protect Stardust’s solar panels — and another shield protecting the main spacecraft body. Each shield is built around composite panels designed to disperse particles as they impact, augmented by blankets of a ceramic cloth called Nextel that further dissipate and spread particle debris.

“Everything occurred pretty much to the minute,” said Duxbury. “And with our cometary encounter complete, we invite everybody to tune in about one million, 71 thousand minutes from now when Stardust returns to Earth, bringing with it the first comet samples in the history of space exploration.”

Scientists believe 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 cometary 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 http://stardust.jpl.nasa.gov .

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

Posted on by Fraser Cain

Success! Spirit Lands Safely on Mars

Image credit: NASA/JPL

NASA controllers confirmed that the Spirit rover successfully landed on Mars today. The spacecraft passed through the atmosphere, deployed its parachute, fired its retrorockets, and then bounced along the Martian surface protected by airbags – its landing time was January 4 at 0435 UTC (11:35 pm EST January 3). Pictures from the Martian surface are expected soon. Spirit will spend at least 90 days traveling around the surface of Mars, searching for evidence of past water with several scientific instruments. The next rover, Opportunity, is expected to land on January 24.

A traveling robotic geologist from NASA has landed on Mars and returned stunning images of the area around its landing site in Gusev Crater.

Mars Exploration Rover Spirit successfully sent a radio signal after the spacecraft had bounced and rolled for several minutes following its initial impact at 11:35 p.m. EST (8:35 p.m. Pacific Standard Time) on January 3.

“This is a big night for NASA,” said NASA Administrator Sean O’Keefe. “We’re back. I am very, very proud of this team, and we’re on Mars.”

Members of the mission’s flight team at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., cheered and clapped when they learned that NASA’s Deep Space Network had received a post-landing signal from Spirit. The cheering resumed about three hours later when the rover transmitted its first images to Earth, relaying them through NASA’s Mars Odyssey orbiter.

“We’ve got many steps to go before this mission is over, but we’ve retired a lot of risk with this landing,” said JPL’s Pete Theisinger, project manager for the Mars Exploration Rover Project.

Deputy project manager for the rovers, JPL’s Richard Cook, said, “We’re certainly looking forward to Opportunity landing three weeks from now.” Opportunity is Spirit’s twin rover, headed for the opposite side of Mars.

Dr. Charles Elachi, JPL director, said, “To achieve this mission, we have assembled the best team of young women and men this country can put together. Essential work was done by other NASA centers and by our industrial and academic partners.

Spirit stopped rolling with its base petal down, though that favorable position could change as airbags deflate, said JPL’s Rob Manning, development manager for the rover’s descent through Mars’ atmosphere and landing on the surface.

NASA chose Spirit’s landing site, within Gusev Crater, based on evidence from Mars orbiters that this crater may have held a lake long ago. A long, deep valley, apparently carved by ancient flows of water, leads into Gusev. The crater itself is basin the size of Connecticut created by an asteroid or comet impact early in Mars’ history. Spirit’s 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 suitable to sustain life.

Spirit traveled 487 million kilometers (302.6 million) miles to reach Mars after its launch from Cape Canaveral Air Force Station, Fla., on June 10, 2003. Its twin, Mars Exploration Rover Opportunity, was launched July 7, 2003, and is on course for a landing on the opposite side of Mars on Jan. 25 (Universal Time and EST; 9:05 p.m. on Jan. 24, PST).

The flight team expects to spend more than a week directing Spirit through a series of steps in unfolding, standing up and other preparations necessary before the rover rolls off of its lander platform to get its wheels onto the ground. Meanwhile, Spirit’s cameras and a mineral-identifying infrared instrument will begin examining the surrounding terrain. That information will help engineers and scientists decide which direction to send the rover first.

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:

http://marsrovers.jpl.nasa.gov , www.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release