The very first stars in our universe were not the behemoths scientists had once thought, according to new simulations performed at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

Astronomers “grew” stars in their computers, mimicking the conditions of our primordial universe. The simulations took weeks. When the scientists’ concoctions were finally done, they were shocked by the results — the full-grown stars were much smaller than expected.

Until now, it was widely believed that the first stars were the biggest of all, with masses hundreds of times that of our sun. The new research shows they are only tens of times the mass of sun; for example, the simulations produced one star that was as little as 43 solar masses.

“The first stars were definitely massive, but not to the extreme we thought before,” said Takashi Hosokawa, an astronomer at JPL and lead author of the new study, appearing online Friday, Nov. 11 in the journal Science. “Our simulations reveal that the growth of these stars is stunted earlier than expected, resulting in smaller final sizes.”

The early universe consisted of nothing more than thin clouds of hydrogen and helium atoms. A few hundred million years after its birth, the first stars began to ignite. How these first stars formed is still a mystery.

Astronomers know that all stars form out of collapsing clouds of gas. Gravity from a growing “seed” at the center of the cloud attracts more and more matter. For so-called normal stars like our sun, this process is aided by heavier elements such as carbon, which help to keep the gas falling onto the budding star cool enough to collapse. If the cloud gets too hot, the gas expands and escapes.

But, in the early universe, stars hadn’t yet produced heavy elements. The very first stars had to form out of nothing but hydrogen and helium. Scientists had theorized that such stars would require even more mass to form, to compensate for the lack of heavy elements and their cooling power. At first, it was thought the stars might be as big as one thousand times the mass of our sun. Later, the models were refined and the first stars were estimated to be hundreds of solar masses.

“These stars keep getting smaller and smaller over time,” said Takashi. “Now we think they are even less massive, only tens of solar masses.”

The team’s simulations reveal that matter in the vicinity of the forming stars heats up to higher temperatures than previously believed, as high as 50,000 Kelvin (90,000 degrees Fahrenheit), or 8.5 times the surface temperature of the sun. Gas this hot expands and escapes the gravity of the developing star, instead of falling back down onto it. This means the stars stop growing earlier than predicted, reaching smaller final sizes.

“This is definitely going to surprise some folks,” said Harold Yorke, an astronomer at JPL and co-author of the study. “It was standard knowledge until now that the first stars had to be extremely massive.”

The results also answer an enigma regarding the first stellar explosions, called supernovae. When massive stars blow up at the end of their lives, they spew ashes made of heavier elements into space. If the very first stars were the monsters once thought, they should have left a specific pattern of these elements imprinted on the material of the following generation of stars. But, as much as astronomers searched the oldest stars for this signature, they couldn’t find it. The answer, it seems, is that it simply is not there. Because the first stars weren’t as massive as previously thought, they would have blown up in a manner akin to the types of stellar explosions that we see today.

“I am sure there are more surprises in store for us regarding this exciting period of the universe,” said Yorke. “NASA’s upcoming James Webb Space Telescope will be a valuable tool to observe this epoch of early star and galaxy formation.”

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New observations by NASA’s Wide-field Infrared Survey Explorer, or WISE, show there are significantly fewer near-Earth asteroids in the mid-size range than previously thought. The findings also indicate NASA has found more than 90 percent of the largest near-Earth asteroids, meeting a goal agreed to with Congress in 1998.

Astronomers now estimate there are roughly 19,500 — not 35,000 — mid-size near-Earth asteroids. Scientists say this improved understanding of the population may indicate the hazard to Earth could be somewhat less than previously thought. However, the majority of these mid-size asteroids remain to be discovered. More research also is needed to determine if fewer mid-size objects (between 330 and 3,300-feet wide) also mean fewer potentially hazardous asteroids, those that come closest to Earth.

The results come from the most accurate census to date of near-Earth asteroids, the space rocks that orbit within 120 million miles (195 million kilometers) of the sun into Earth’s orbital vicinity. WISE observed infrared light from those in the middle to large-size category. The survey project, called NEOWISE, is the asteroid-hunting portion of the WISE mission. Study results appear in the Astrophysical Journal.

“NEOWISE allowed us to take a look at a more representative slice of the near-Earth asteroid numbers and make better estimates about the whole population,” said Amy Mainzer, lead author of the new study and principal investigator for the NEOWISE project at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It’s like a population census, where you poll a small group of people to draw conclusions about the entire country.”

WISE scanned the entire celestial sky twice in infrared light between January 2010 and February 2011, continuously snapping pictures of everything from distant galaxies to near-Earth asteroids and comets. NEOWISE observed more than 100 thousand asteroids in the main belt between Mars and Jupiter, in addition to at least 585 near Earth.

WISE captured a more accurate sample of the asteroid population than previous visible-light surveys because its infrared detectors could see both dark and light objects. It is difficult for visible-light telescopes to see the dim amounts of visible-light reflected by dark asteroids. Infrared-sensing telescopes detect an object’s heat, which is dependent on size and not reflective properties.

Though the WISE data reveal only a small decline in the estimated numbers for the largest near-Earth asteroids, which are 3,300 feet (1 kilometer) and larger, they show 93 percent of the estimated population have been found. This fulfills the initial “Spaceguard” goal agreed to with Congress. These large asteroids are about the size of a small mountain and would have global consequences if they were to strike Earth. The new data revise their total numbers from about 1,000 down to 981, of which 911 already have been found. None of them represents a threat to Earth in the next few centuries. It is believed that all near-Earth asteroids approximately 6 miles (10 kilometers) across, as big as the one thought to have wiped out the dinosaurs, have been found.

“The risk of a really large asteroid impacting the Earth before we could find and warn of it has been substantially reduced,” said Tim Spahr, the director of the Minor Planet Center at the Harvard Smithsonian Center for Astrophysics in Cambridge, Mass.

The situation is different for the mid-size asteroids, which could destroy a metropolitan area if they were to impact in the wrong place. The NEOWISE results find a larger decline in the estimated population for these bodies than what was observed for the largest asteroids. So far, the Spaceguard effort has found and is tracking more than 5,200 near-Earth asteroids 330 feet or larger, leaving more than an estimated 15,000 still to discover. In addition, scientists estimate there are more than a million unknown smaller near-Earth asteroids that could cause damage if they were to impact Earth.

“NEOWISE was just the latest asset NASA has used to find Earth’s nearest neighbors,” said Lindley Johnson, program executive for the Near Earth Object Observation Program at NASA Headquarters in Washington. “The results complement ground-based observer efforts over the past 12 years. These observers continue to track these objects and find even more.”

WISE is managed and operated by JPL for NASA’s Science Mission Directorate in Washington. The principal investigator, Edward Wright, is at the University of California, Los Angeles. The WISE science instrument was built by the Space Dynamics Laboratory in Logan, Utah, and the spacecraft was built by Ball Aerospace and Technologies Corp. in Boulder, Colo. Science operations and data processing occur at the Infrared Processing and Analysis Center at the California Institute of Technology.

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Two studies appearing in the Aug. 25 issue of the journal Nature provide new insights into a cosmic accident that has been streaming X-rays toward Earth since late March. NASA’s Swift satellite first alerted astronomers to intense and unusual high-energy flares from the new source in the constellation Draco.

“Incredibly, this source is still producing X-rays and may remain bright enough for Swift to observe into next year,” said David Burrows, professor of astronomy at Penn State University and lead scientist for the mission’s X-Ray Telescope instrument. “It behaves unlike anything we’ve seen before.”

Astronomers soon realized the source, known as Swift J1644+57, was the result of a truly extraordinary event — the awakening of a distant galaxy’s dormant black hole as it shredded and consumed a star. The galaxy is so far away, it took the light from the event approximately 3.9 billion years to reach Earth.

Burrows’ study included NASA scientists. It highlights the X- and gamma-ray observations from Swift and other detectors, including the Japan-led Monitor of All-sky X-ray Image (MAXI) instrument aboard the International Space Station.

The second study was led by Ashley Zauderer, a post-doctoral fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. It examines the unprecedented outburst through observations from numerous ground-based radio observatories, including the National Radio Astronomy Observatory’s Expanded Very Large Array (EVLA) near Socorro, N.M.

Most galaxies, including our own, possess a central supersized black hole weighing millions of times the sun’s mass. According to the new studies, the black hole in the galaxy hosting Swift J1644+57 may be twice the mass of the four-million-solar-mass black hole in the center of the Milky Way galaxy. As a star falls toward a black hole, it is ripped apart by intense tides. The gas is corralled into a disk that swirls around the black hole and becomes rapidly heated to temperatures of millions of degrees.

The innermost gas in the disk spirals toward the black hole, where rapid motion and magnetism create dual, oppositely directed “funnels” through which some particles may escape. Jets driving matter at velocities greater than 90 percent the speed of light form along the black hole’s spin axis. In the case of Swift J1644+57, one of these jets happened to point straight at Earth.

“The radio emission occurs when the outgoing jet slams into the interstellar environment,” Zauderer explained. “By contrast, the X-rays arise much closer to the black hole, likely near the base of the jet.”

Theoretical studies of tidally disrupted stars suggested they would appear as flares at optical and ultraviolet energies. The brightness and energy of a black hole’s jet is greatly enhanced when viewed head-on. The phenomenon, called relativistic beaming, explains why Swift J1644+57 was seen at X-ray energies and appeared so strikingly luminous.

When first detected March 28, the flares were initially assumed to signal a gamma-ray burst, one of the nearly daily short blasts of high-energy radiation often associated with the death of a massive star and the birth of a black hole in the distant universe. But as the emission continued to brighten and flare, astronomers realized that the most plausible explanation was the tidal disruption of a sun-like star seen as beamed emission.

By March 30, EVLA observations by Zauderer’s team showed a brightening radio source centered on a faint galaxy near Swift’s position for the X-ray flares. These data provided the first conclusive evidence that the galaxy, the radio source and the Swift event were linked.

“Our observations show that the radio-emitting region is still expanding at more than half the speed of light,” said Edo Berger, an associate professor of astrophysics at Harvard and a coauthor of the radio paper. “By tracking this expansion backward in time, we can confirm that the outflow formed at the same time as the Swift X-ray source.”

Swift, launched in November 2004, is managed by NASA’s Goddard Space Flight Center in Greenbelt, Md. It is operated in collaboration with Penn State, the Los Alamos National Laboratory in N.M. and Orbital Sciences Corp., in Dulles, Va., with international collaborators in the U.K., Italy, Germany and Japan. MAXI is operated by the Japan Aerospace Exploration Agency as an external experiment attached to the Kibo module of the space station.

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Scientists using data from NASA’s Wide-field Infrared Survey Explorer (WISE) have discovered the coldest class of star-like bodies, with temperatures as cool as the human body.

Astronomers hunted these dark orbs, termed Y dwarfs, for more than a decade without success. When viewed with a visible-light telescope, they are nearly impossible to see. WISE’s infrared vision allowed the telescope to finally spot the faint glow of six Y dwarfs relatively close to our sun, within a distance of about 40 light-years.

“WISE scanned the entire sky for these and other objects, and was able to spot their feeble light with its highly sensitive infrared vision,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground.”

The Y’s are the coldest members of the brown dwarf family. Brown dwarfs are sometimes referred to as “failed” stars. They are too low in mass to fuse atoms at their cores and thus don’t burn with the fires that keep stars like our sun shining steadily for billions of years. Instead, these objects cool and fade with time, until what little light they do emit is at infrared wavelengths.

Astronomers study brown dwarfs to better understand how stars form, and to understand the atmospheres of planets beyond our solar system. The atmospheres of brown dwarfs are similar to those of gas-giant planets like Jupiter, but they are easier to observe because they are alone in space, away from the blinding light of a parent star.

So far, WISE data have revealed 100 new brown dwarfs. More discoveries are expected as scientists continue to examine the enormous quantity of data from WISE. The telescope performed the most advanced survey of the sky at infrared wavelengths to date, from Jan. 2010 to Feb. 2011, scanning the entire sky about 1.5 times.

Of the 100 brown dwarfs, six are classified as cool Y’s. One of the Y dwarfs, called WISE 1828+2650, is the record holder for the coldest brown dwarf, with an estimated atmospheric temperature cooler than room temperature, or less than about 80 degrees Fahrenheit (25 degrees Celsius).

“The brown dwarfs we were turning up before this discovery were more like the temperature of your oven,” said Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, Calif. “With the discovery of Y dwarfs, we’ve moved out of the kitchen and into the cooler parts of the house.”

Kirkpatrick is lead author of a paper appearing in the Astrophysical Journal Supplement Series, describing the 100 confirmed brown dwarfs. Michael Cushing, a WISE team member at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., is lead author of a paper describing the Y dwarfs in the Astrophysical Journal.

The Y dwarfs are in our sun’s neighborhood, from approximately nine to 40 light-years away. The Y dwarf approximately nine light-years away, WISE 1541-2250, may become the seventh closest star system, bumping Ross 154 back to eighth. By comparison, the star closest to our solar system, Proxima Centauri, is about four light-years away.

“Finding brown dwarfs near our sun is like discovering there’s a hidden house on your block that you didn’t know about,” Cushing said. “It’s thrilling to me to know we’ve got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than our closest known star.”

Once the WISE team identified brown dwarf candidates, they turned to NASA’s Spitzer Space Telescope to narrow their list. To definitively confirm them, the WISE team used some of the most powerful telescopes on Earth to split apart the objects’ light and look for telltale molecular signatures of water, methane and possibly ammonia. For the very coldest of the new Y dwarfs, the team used NASA’s Hubble Space Telescope. The Y dwarfs were identified based on a change in these spectral features compared to other brown dwarfs, indicating they have a lower atmospheric temperature.

The ground-based telescopes used in these studies include the NASA Infrared Telescope Facility atop Mauna Kea, Hawaii; Caltech’s Palomar Observatory near San Diego; the W.M. Keck Observatory atop Mauna Kea, Hawaii; and the Magellan Telescopes at Las Campanas Observatory, Chile, among others.

JPL manages WISE for NASA’s Science Mission Directorate. The principal investigator is Edward Wright at UCLA. The WISE satellite was decommissioned in 2011 after completing its sky survey observations. The mission was selected under NASA’s Explorers Program managed by the Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah, and the spacecraft by Ball Aerospace & Technologies Corp., in Boulder, Colo. Science operations and data processing are at the Infrared Processing and Analysis Center at the California Institute of Technology. JPL is a division of the California Institute of Technology in Pasadena.
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In December 2010, a pair of mismatched stars in the southern constellation Crux whisked past each other at a distance closer than Venus orbits the sun. The system possesses a so-far unique blend of a hot and massive star with a compact fast-spinning pulsar. The pair’s closest encounters occur every 3.4 years and each is marked by a sharp increase in gamma rays, the most extreme form of light.

The unique combination of stars, the long wait between close approaches, and periods of intense gamma-ray emission make this system irresistible to astrophysicists. Now, a team using NASA’s Fermi Gamma-ray Space Telescope to observe the 2010 encounter reports that the system displayed fascinating and unanticipated activity.

“Even though we were waiting for this event, it still surprised us,” said Aous Abdo, a Research Assistant Professor at George Mason University in Fairfax, Va., and a leader of the research team.

Few pairings in astronomy are as peculiar as high-mass binaries, where a hot blue-white star many times the sun’s mass and temperature is joined by a compact companion no bigger than Earth — and likely much smaller. Depending on the system, this companion may be a burned-out star known as a white dwarf, a city-sized remnant called a neutron star (also known as a pulsar) or, most exotically, a black hole.

Just four of these “odd couple” binaries were known to produce gamma rays, but in only one of them did astronomers know the nature of the compact object. That binary consists of a pulsar designated PSR B1259-63 and a 10th-magnitude Be-type star known as LS 2883. The pair lies 8,000 light-years away.

The pulsar is a fast-spinning neutron star with a strong magnetic field. This combination powers a lighthouse-like beam of energy, which astronomers can easily locate if the beam happens to sweep toward Earth. The beam from PSR B1259-63 was discovered in 1989 by the Parkes radio telescope in Australia. The neutron star is about the size of Washington, D.C., weighs about twice the sun’s mass, and spins almost 21 times a second.

The pulsar follows an eccentric and steeply inclined orbit around LS 2883, which weighs roughly 24 solar masses and spans about nine times its size. This hot blue star sits embedded in a disk of gas that flows out from its equatorial region.

At closest approach, the pulsar passes less than 63 million miles from its star — so close that it skirts the gas disk around the star’s middle. The pulsar punches through the disk on the inbound leg of its orbit. Then it swings around the star at closest approach and plunges through the disk again on the way out.

“During these disk passages, energetic particles emitted by the pulsar can interact with the disk, and this can lead to processes that accelerate particles and produce radiation at different energies,” said study co-author Simon Johnston of the Australia Telescope National Facility in Epping, New South Wales. “The frustrating thing for astronomers is that the pulsar follows such an eccentric orbit that these events only happen every 3.4 years.”

In anticipation of the Dec. 15, 2010, closest approach, astronomers around the world mounted a multiwavelength campaign to observe the system over a broad energy range, from radio wavelengths to the most energetic gamma rays detectable. The observatories included Fermi and NASA’s Swift spacecraft; the European space telescopes XMM-Newton and INTEGRAL; the Japan-U.S. Suzaku satellite; the Australia Telescope Compact Array; optical and infrared telescopes in Chile and South Africa; and the High Energy Stereoscopic System (H.E.S.S.), a ground-based observatory in Namibia that can detect gamma rays with energies of trillions of electron volts, beyond Fermi’s range. (For comparison, the energy of visible light is between two and three electron volts.)

“When you know you have a chance of observing this system only once every few years, you try to arrange for as much coverage as you can,” said Abdo, the principal investigator of the NASA-funded international campaign. “Understanding this system, where we know the nature of the compact object, may help us understand the nature of the compact objects in other, similar systems.”

Despite monitoring of the system with the EGRET telescope aboard NASA’s Compton Gamma-Ray Observatory in the 1990s, gamma-ray emission in the billion-electron-volt (GeV) energy range had never been seen from the binary.

Late last year, as the pulsar headed toward its massive companion, the Large Area Telescope (LAT) aboard Fermi discovered faint gamma-ray emission.

“During the first disk passage, which lasted from mid-November to mid-December, the LAT recorded faint yet detectable emission from the binary. We assumed that the second passage would be similar, but in mid-January 2011, as the pulsar began its second passage through the disk, we started seeing surprising flares that were many times stronger than those we saw before,” Abdo said.

Stranger still, the system’s output at radio and X-ray energies showed nothing unusual as the gamma-ray flares raged.

“The most intense days of the flare were Jan. 20 and 21 and Feb. 2, 2011,” said Abdo. “What really surprised us is that on any of these days, the source was more than 15 times brighter than it was during the entire month-and-a-half-long first passage.”

The study will appear in the July 20 issue of The Astrophysical Journal Letters and is available online.

“One great advantage of the Fermi LAT observations is the continuous monitoring of the source, which gives us the most complete gamma-ray observations of this system,” said Julie McEnery, the Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Astronomers are continuing to analyze their bounty of data and working to understand the surprising flares. And in May 2014, when the pulsar once again approaches its giant companion, they’ll be watching.

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An assorted mix of colorful galaxies is being released today by NASA’s Wide-field Infrared Survey Explorer mission, or WISE. The nine galaxies are a taste of what’s to come. The mission plans to release similar images for the 1,000 largest galaxies that appear in our sky, and possibly more.

“Galaxies come in all sorts of delicious flavors,” said Tom Jarrett, a WISE team member at the Infrared Processing and Analysis Center, California Institute of Technology, in Pasadena, who studies our Milky Way’s neighboring galaxies. “Our first sample shows what WISE is capable of. We can produce spectacular high-resolution images of the largest galaxies.”

The new collage showcases galaxies of varying types — everything from “grand design spirals,” with their elegant cinnamon bun-like swirling arms, to so-called “flocculent” galaxies, which have a more patchy appearance. They are close enough to us that WISE can see details of their structure, for example their sinuous arms and central bulges. Because WISE can study so many types of nearby galaxies, its observations will provide a better understanding of how these complex objects form and evolve.

WISE, which launched into space in Dec. 2009, scanned the whole sky one-and-a-half times in infrared light. It captured images of asteroids in our own solar system, distant galaxies billions of light-years away, and everything in between. The mission’s first batch of data, which does not include all of the galaxies in the new collage, was released to the public in April of this year. The complete WISE catalog will follow a year later, in the spring of 2012.

“We can learn about a galaxy’s stars — where are they forming and how fast?” said Jarrett. “There’s so much diversity in galaxies to explore.”

The new collection of nine galaxies shows off this diversity, with members of different sizes, colors and shapes. Infrared light from the galaxies, which we can’t see with our eyes, has been translated into visible-light colors that we can see. Blue colors show older populations of stars, while yellow indicates dusty areas where stars are forming.

Some of the galaxies are oriented toward us nearly face-on, such as Messier 83, and others are partly angled away from us, for example Messier 81. One galaxy, NGC 5907, is oriented completely edge-on, so that all we can see is its profile. The edge of its main galaxy disk appears pencil-thin, and its halo of surrounding stars is barely visible as a green glow above and below the disk.

The arms of the galaxies come in different shapes too. Messier 51 has arms that look like a spiral lollipop, while the arms of the flocculent galaxy NGC 2403 look choppy, perhaps more like layered frosting. Astronomers think that gravitational interactions with companion galaxies may lead to more well-defined spiral arms. One such companion can be seen near Messier 51 in blue. Some of the galaxies also have spokes, or spurs, that join the arms together, such as those in IC 342.

JPL manages and operates the Wide-field Infrared Survey Explorer for NASA’s Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA’s Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

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A new supercomputer simulation shows the collision of two neutron stars can naturally produce the magnetic structures thought to power the high-speed particle jets associated with short gamma-ray bursts (GRBs). The study provides the most detailed glimpse of the forces driving some of the universe’s most energetic explosions.

The state-of-the-art simulation ran for nearly seven weeks on the Damiana computer cluster at the Albert Einstein Institute (AEI) in Potsdam, Germany. It traces events that unfold over 35 milliseconds — about three times faster than the blink of an eye.

GRBs are among the brightest events known, emitting as much energy in a few seconds as our entire galaxy does in a year. Most of this emission comes in the form of gamma rays, the highest-energy form of light.

“For the first time, we’ve managed to run the simulation well past the merger and the formation of the black hole,” said Chryssa Kouveliotou, a co-author of the study at NASA’s Marshall Space Flight Center in Huntsville, Ala. “This is by far the longest simulation of this process, and only on sufficiently long timescales does the magnetic field grow and reorganize itself from a chaotic structure into something resembling a jet.”

GRBs longer than two seconds are the most common type and are widely thought to be triggered by the collapse of a massive star into a black hole. As matter falls toward the black hole, some of it forms jets in the opposite direction that move near the speed of light. These jets bore through the collapsing star along its rotational axis and produce a blast of gamma rays after they emerge. Understanding short GRBs, which fade quickly, proved more elusive. Astronomers had difficulty obtaining precise positions for follow-up studies.

That began to change in 2004, when NASA’s Swift satellite began rapidly locating bursts and alerting astronomers where to look.

“For more than two decades, the leading model of short GRBs was the merger of two neutron stars,” said co-author Bruno Giacomazzo at the University of Maryland and NASA’s Goddard Space Flight Center in Greenbelt, Md. “Only now can we show that the merger of neutron stars actually produces an ultrastrong magnetic field structured like the jets needed for a GRB.”

A neutron star is the compressed core left behind when a star weighing less than about 30 times the sun’s mass explodes as a supernova. Its matter reaches densities that cannot be reproduced on Earth — a single spoonful outweighs the Himalayan Mountains.

The simulation began with a pair of magnetized neutron stars orbiting just 11 miles apart. Each star packed 1.5 times the mass of the sun into a sphere just 17 miles across and generated a magnetic field about a trillion times stronger than the sun’s.

In 15 milliseconds, the two neutron stars crashed, merged and transformed into a rapidly spinning black hole weighing 2.9 suns. The edge of the black hole, known as its event horizon, spanned less than six miles. A swirling chaos of superdense matter with temperatures exceeding 18 billion degrees Fahrenheit surrounded the newborn black hole. The merger amplified the strength of the combined magnetic field, but it also scrambled it into disarray.

Over the next 11 milliseconds, gas swirling close to the speed of light continued to amplify the magnetic field, which ultimately became a thousand times stronger than the neutron stars’ original fields. At the same time, the field became more organized and gradually formed a pair of outwardly directed funnels along the black hole’s rotational axis.

This is exactly the configuration needed to power the jets of ultrafast particles that produce a short gamma-ray burst. Neither of the magnetic funnels was filled with high-speed matter when the simulation ended, but earlier studies have shown that jet formation can occur under these conditions.

“By solving Einstein’s relativity equations as never before and letting nature take its course, we’ve lifted the veil on short GRBs and revealed what could be their central engine,” said Luciano Rezzolla, the study’s lead author at AEI. “This is a long-awaited result. Now it appears that neutron star mergers inevitably produce aligned jet-like structures in an ultrastrong magnetic field.”

The study is available online and will appear in the May 1 edition of The Astrophysical Journal Letters.

The authors note the ultimate proof of the merger model will have to await the detection of gravitational waves — ripples in the fabric of space-time predicted by relativity. Merging neutron stars are expected to be prominent sources, so the researchers also computed what the model’s gravitational-wave signal would look like. Observatories around the world are searching for gravitational waves, so far without success because the signals are so faint.

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X-ray observations made by the Suzaku observatory provide the clearest picture to date of the size, mass and chemical content of a nearby cluster of galaxies. The study also provides the first direct evidence that million-degree gas clouds are tightly gathered in the cluster’s outskirts.

Suzaku is sponsored by the Japan Aerospace Exploration Agency (JAXA) with contributions from NASA and participation by the international scientific community. The findings will appear in the March 25 issue of the journal Science.

Galaxy clusters are millions of light-years across, and most of their normal matter comes in the form of hot X-ray-emitting gas that fills the space between the galaxies.

“Understanding the content of normal matter in galaxy clusters is a key element for using these objects to study the evolution of the universe,” explained Adam Mantz, a co-author of the paper at NASA’s Goddard Space Flight Center in Greenbelt, Md.

Clusters provide independent checks on cosmological values established by other means, such as galaxy surveys, exploding stars and the cosmic microwave background, which is the remnant glow of the Big Bang. The cluster data and the other values didn’t agree.

NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) explored the cosmic microwave background and established that baryons — what physicists call normal matter — make up only about 4.6 percent of the universe. Yet previous studies showed that galaxy clusters seemed to hold even fewer baryons than this amount.

Suzaku images of faint gas at the fringes of a nearby galaxy cluster have allowed astronomers to resolve this discrepancy for the first time.

The satellite’s ideal target for this study was the Perseus Galaxy Cluster, which is located about 250 million light-years away and named for the constellation in which it resides. It is the brightest extended X-ray source beyond our own galaxy, and also the brightest and closest cluster in which Suzaku has attempted to map outlying gas.

“Before Suzaku, our knowledge of the properties of this gas was limited to the innermost parts of clusters, where the X-ray emission is brightest, but this left a huge volume essentially unexplored,” said Aurora Simionescu, the study’s lead researcher at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University.

In late 2009, Suzaku’s X-ray telescopes repeatedly observed the cluster by progressively imaging areas farther east and northwest of the center. Each set of images probed sky regions two degrees across — equivalent to four times the apparent width of the full moon or about 9 million light-years at the cluster’s distance. Staring at the cluster for about three days, the satellite mapped X-rays with energies hundreds of times greater than that of visible light.

From the data, researchers measured the density and temperature of the faint X-ray gas, which let them infer many other important quantities. One is the so-called virial radius, which essentially marks the edge of the cluster. Based on this measurement, the cluster is 11.6 million light-years across and contains more than 660 trillion times the mass of the sun. That’s nearly a thousand times the mass of our Milky Way galaxy.

The researchers also determined the ratio of the cluster’s gas mass to its total mass, including dark matter — the mysterious substance that makes up about 23 percent of the universe, according to WMAP. By virtue of their enormous size, galaxy clusters should contain a representative sample of cosmic matter, with normal-to-dark-matter ratios similar to WMAP’s. Yet the outer parts of the Perseus cluster seemed to contain too many baryons, the opposite of earlier studies, but still in conflict with WMAP.

To solve the problem, researchers had to understand the distribution of hot gas in the cluster, the researchers say. In the central regions, the gas is repeatedly whipped up and smoothed out by passing galaxies. But computer simulations show that fresh infalling gas at the cluster edge tends to form irregular clumps.

Not accounting for the clumping overestimates the density of the gas. This is what led to the apparent disagreement with the fraction of normal matter found in the cosmic microwave background.

“The distribution of these clumps and the fact that they are not immediately destroyed as they enter the cluster are important clues in understanding the physical processes that take place in these previously unexplored regions,” said Steve Allen at KIPAC, the principal investigator of the Suzaku observations.

Goddard supplied Suzaku’s X-ray telescopes and data-processing software, and it continues to operate a facility that supports U.S. astronomers who use the spacecraft.

Suzaku ( Japanese for “red bird of the south”) is the fifth Japanese X-ray astronomy satellite. It was launched as Astro-E2 on July 10, 2005, and renamed in orbit. The observatory was developed at JAXA’s Institute of Space and Astronautical Science in collaboration with NASA and other Japanese and U.S. institutions.

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Stars at all stages of development, from dusty little tots to young adults, are on display in a new image from NASA’s Spitzer Space Telescope.

This cosmic community is called the North American nebula. In visible light, the region resembles the North American continent, with the most striking resemblance being the Gulf of Mexico. But in Spitzer’s infrared view, the continent disappears. Instead, a swirling landscape of dust and young stars comes into view.

“One of the things that makes me so excited about this image is how different it is from the visible image, and how much more we can see in the infrared than in the visible,” said Luisa Rebull of NASA’s Spitzer Science Center at the California Institute of Technology, Pasadena, Calif. Rebull is lead author of a paper about the observations, accepted for publication in the Astrophysical Journal Supplement Series. “The Spitzer image reveals a wealth of detail about the dust and the young stars here.”

Rebull and her team have identified more than 2,000 new, candidate young stars in the region. There were only about 200 known before. Because young stars grow up surrounded by blankets of dust, they are hidden in visible-light images. Spitzer’s infrared detectors pick up the glow of the dusty, buried stars.

A star is born inside a collapsing ball of gas and dust. As the material collapses inward, it flattens out into a disk that spins around together with the forming star like a spinning top. Jets of gas shoot perpendicularly away from the disk, above and below it. As the star ages, planets are thought to form out of the disk — material clumps together, ultimately growing into mature planets. Eventually, most of the dust dissipates, aside from a tenuous ring similar to the one in our solar system, referred to as Zodiacal dust.

The new Spitzer image reveals all the stages of a star’s young life, from the early years when it is swaddled in dust to early adulthood, when it has become a young parent to a family of developing planets. Sprightly “toddler” stars with jets can also be identified in Spitzer’s view.

“This is a really busy area to image, with stars everywhere, from the North American complex itself, as well as in front of and behind the region,” said Rebull. “We refer to the stars that are not associated with the region as contamination. With Spitzer, we can easily sort this contamination out and clearly distinguish between the young stars in the complex and the older ones that are unrelated.”

The North American nebula still has a mystery surrounding it, involving its power source. Nobody has been able to identify the group of massive stars that is thought to be dominating the nebula. The Spitzer image, like images from other telescopes, hints that the missing stars are lurking behind the Gulf of Mexico portion of the nebula. This is evident from the illumination pattern of the nebula, especially when viewed with the detector on Spitzer that picks up 24-micron infrared light. That light appears to be coming from behind the Gulf of Mexico’s dark tangle of clouds, in the same way that sunlight creeps out from behind a rain cloud.

The nebula’s distance from Earth is also a mystery. Current estimates put it at about 1,800 light-years from Earth. Spitzer will refine this number by finding more stellar members of the North American complex.

The Spitzer observations were made before it ran out of the liquid coolant needed to chill its longer-wavelength instruments. Currently, Spitzer’s two shortest-wavelength channels (3.6 and 4.5 microns) are still working. The composite image shows light from both the infrared array camera and multiband imaging processor. Infrared light with a wavelength of 3.6 microns is color-coded blue; 8.0-micron light is green; and 24-micron light is red.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

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Engineers at Orbital Sciences Corporation in Dulles, Va., have successfully replaced a faulty component that could have had serious consequences for the Glory satellite, NASA’s next climate-monitoring mission. In June, Glory engineers noticed a problem with one of the solar array drive assemblies, or SADAs, that appeared initially like it would take five or six months to repair.

However, nimble responses from two engineering companies contracted by the Glory team — New York City-based Honeybee Robotics and California-based Moog Chatsworth — have resolved the problem in little more than two months instead.

“Both Moog and Honeybee really stepped up when we needed it most. They put a lot of personnel and extra effort into this to get us back up and running,” said Glory’s Deputy Observatory Manager Michael Bruckner. “To fix the problem, we used a new component called a twist capsule. The part hadn’t been flight-qualified, but we managed to design, build, and qualify it all in about two months. This is an unbelievable accomplishment.”

Glory is now scheduled to launch from Vandenberg Air Force base in California aboard a Taurus XL launch vehicle no earlier than Feb. 23, 2011.

Two instruments aboard Glory — the Aerosol Po¬larimetery Sensor (APS) and the Total Irradiance Monitor (TIM) — will supply scientists with information about criti¬cal components of Earth’s climate system. The APS, a polarimeter mounted on the underside of the Glory spacecraft and fac¬ing downward, will collect data on airborne particles called aerosols. Aerosols can affect the climate by warming or cooling the atmosphere depending on their type, as well as modifying the behavior of clouds.

The TIM, located on the opposite side of the space¬craft, will face toward the sun and measure the intensity of incoming solar radiation at the top of the atmosphere. It will help maintain a thirty-plus year satellite record of the sun’s irradiance, which can change subtly over time due to changes in the sun’s magnetic field.

Glory will take its place among a series of Earth-observing satellites, dubbed the Afternoon Constellation or A-Train, that orbit the planet in a cluster at the same altitude and inclination. The close proximity of satellites on the A-Train allows researchers to easily compare data from complementary science instruments flying on adjacent satellites.

Orbital Sciences Corporation is responsible for Glory integration and testing, the Taurus XL launch vehicle, and spacecraft operations. The Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado provided and will operate the TIM instrument. Raytheon provided the APS instrument, which will be operated by NASA’s Goddard Institute for Space Studies (GISS) in New York City.

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