Category: Astronomy

Artist illustration of microscopic crystals surrounding a dusty disk. Image credit: NASA/JPL. Click to enlarge.
NASA’s Spitzer Space Telescope has spotted the very beginnings of what might become planets around the puniest of celestial orbs – brown dwarfs, or “failed stars.”

The telescope’s infrared eyes have for the first time detected clumps of microscopic dust grains and tiny crystals orbiting five brown dwarfs. These clumps and crystals are thought to collide and further lump together to eventually make planets. Similar materials are seen in planet-forming regions around stars and in comets, the remnants of our own solar system’s construction.

The findings provide evidence that brown dwarfs, despite being colder and dimmer than stars, undergo the same initial steps of the planet-building process.

“We are learning that the first stages of planet formation are more robust than previously believed,” said Dr. Daniel Apai, an astronomer at the University of Arizona, Tucson, and member of the NASA Astrobiology Institute’s Life and Planets Astrobiology Center. “Spitzer has given us the possibility to study how planets are built in widely different environments.”

The observations also imply that brown dwarfs might be good targets for future planet-hunting missions. Astronomers do not know if life could exist on planets around brown dwarfs.

Brown dwarfs differ from stars largely due to their mass. They lack the mass to ignite internally and shine brightly. However, they are believed to arise like stars, out of thick clouds of gas and dust that collapse under their own weight. And like stars, brown dwarfs develop disks of gas and dust that circle around them. Spitzer has observed many of these disks, which glow at infrared wavelengths.

Apai and his team used Spitzer to collect detailed information on the minerals that make up the dust disks of six young brown dwarfs located 520 light-years away, in the Chamaeleon constellation. The six objects range in mass from about 40 to 70 times that of Jupiter, and they are roughly 1 to 3 million years old.

The astronomers discovered that five of the six disks contain dust particles that have crystallized and are sticking together in what may be the early phases of planet assembling. They found relatively large grains and many small crystals of a mineral called olivine.

“We are seeing processed particles that are linking up and growing in size,” said Dr. Ilaria Pascucci, a co-author also of the University of Arizona. “This is exciting because we weren’t sure if the disks of such cool objects would behave the same way that stellar disks do.”

The team also noticed a flattening of the brown dwarfs’ disks, which is another sign that dust is gathering up into planets.

A paper on these findings appears online today in Science. Authors of the paper also include Drs. Jeroen Bouwman, Thomas Henning and Cornelis P. Dullemond of the Max Planck Institute for Astronomy, Germany; and Dr. Antonella Natta of the Osservatorio Astrofisico di Arcetri, Italy.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spitzer’s infrared spectrograph, which made the observations, was built by Cornell University, Ithaca, N.Y. Its development was led by Dr. Jim Houck of Cornell. The NASA Astrobiology Institute, founded in 1997, is a partnership between NASA, 16 major U.S. teams and six international consortia.

For artist concepts, graphics and more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer/ . For more information about the NASA Astrobiology Institute, visit http://nai.arc.nasa.gov/ . For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/ .

Original Source: NASA/JPL News Release

Spiral Galaxy NGC 2403. Image credit: Subaru. Click to enlarge.
Subaru Telescope, using Suprime-Cam, took the clearest most complete image to date of the spiral galaxy NGC 2403. At a distance of 10 million light years, NGC 2403 is an Sc type galaxy, which has open spiral arms and a small nucleus. It is approximately half the mass of our own galaxy, the Milky Way, and has an abundance of neutral hydrogen gas. In the spiral arms we see active star formation regions in red, clusters of young blue stars called OB associations, and darker regions called dust lanes where light is blocked by gas and dust within the galaxy.

This is not the first time NGC 2403 has been studied. Edwin Hubble used NGC 2403 as evidence that more distant galaxies move more quickly away from us, now called Hubble’s Law. It was also used to develop the Tully-Fisher relation, which states that there is a relation between a galaxy’s rotational speed and its brightness. NGC 2403 has become an important standard galaxy when deciding the distances to other galaxies, as we recognize the vast expanse of space.

Larger galaxies are thought to have developed from the collision and merger of smaller galaxies. Mergers can leave enduring marks on a galaxy’s halo, the most extended and generally spherical component of a galaxy. There is evidence that relatively young stars exist in the halo of NGC 2403, hinting at a recent merger with another galaxy. Astronomers are now studying this image to see if the color and brightness of the stars in the halo of NGC 2403 will reveal conclusive evidence of past mergers.

Original Source: Subaru News Release

Giant mosaic of Andromeda made up of 11,000 images. Image credit: NASA/JPL. Click to enlarge.
NASA’s Spitzer Space Telescope has captured a stunning infrared view of Messier 31, the famous spiral galaxy also known as Andromeda.

Andromeda is the most-studied galaxy outside our own Milky Way, yet Spitzer’s sensitive infrared eyes have detected captivating new features, including bright, aging stars and a spiral arc in the center of the galaxy. The infrared image also reveals an off-centered ring of star formation and a hole in the galaxy’s spiral disk of arms. These asymmetrical features may have been caused by interactions with the several satellite galaxies that surround Andromeda.

“Occasionally small satellite galaxies run straight through bigger galaxies,” said Dr. Karl Gordon of the Steward Observatory, University of Arizona, Tucson, lead investigator of the new observation. “It appears a little galaxy punched a hole through Andromeda’s disk, much like a pebble breaks the surface of a pond.”

The new false-color Andromeda image is available at http://www.spitzer.caltech.edu/spitzer/ .

Approximately 2.5 million light-years away, Andromeda is the closest spiral galaxy and is the only one visible to the naked eye. Unlike our Milky Way galaxy, which we view from the inside, Andromeda is studied from the outside. Astronomers believe that Andromeda and the Milky Way will eventually merge together.

Spitzer detects dust heated by stars in the galaxy. Its multiband imaging photometer’s 24-micron detector recorded approximately 11,000 separate infrared snapshots over 18 hours to create the new comprehensive mosaic. This instrument’s resolution and sensitivity is a vast improvement over previous infrared technologies, enabling scientists to trace the spiral structures within Andromeda to an unprecedented level of detail.

“In contrast to the smooth appearance of Andromeda at optical wavelengths, the Spitzer image reveals a well-defined nuclear bulge and a system of spiral arms,” said Dr. Susan Stolovy, a co-investigator from the Spitzer Science Center at the California Institute of Technology, Pasadena.

The galaxy’s central bulge glows in the light emitted by warm dust from old, giant stars. Just outside the bulge, a system of inner spiral arms can be seen, and outside this, a well-known prominent ring of star formation.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology. The Jet Propulsion Laboratory is a division of Caltech.

Original Source: NASA/JPL News Release

Chandra image of Sgr A*. Image credit: Chandra. Click to enlarge.
NASA’s Chandra X-ray Observatory revealed a new generation of stars spawned by a super-massive black hole at the center of the Milky Way galaxy. This novel mode of star formation may solve several mysteries about these super-massive black holes that reside at the centers of nearly all galaxies.

“Massive black holes are usually known for violence and destruction,” said Sergei Nayakshin of the University of Leicester, United Kingdom. “So it’s remarkable this black hole helped create new stars, not just destroy them.”

Black holes have earned their fearsome reputation because any material, including stars, that falls within their “event horizon” is never seen again. These new results indicate immense disks of gas, orbiting many black holes at a safe distance from the event horizon, can help nurture the formation of new stars. This conclusion comes from new clues that could only be revealed in X-rays. Until the latest Chandra results, researchers have disagreed about the origin of a mysterious group of massive stars discovered by infrared astronomers.

The stars orbit less than a light year from the Milky Way’s central black hole, which is known as Sagittarius A* (Sgr A*). At such close distances to Sgr A*, the standard model for star forming gas clouds predicts they should have been ripped apart by tidal forces from the black hole. Two models, based on previous research, to explain this puzzle have been proposed. In the disk model, the gravity of a dense disk of gas around Sgr A* offsets the tidal forces and allows stars to form.

In the migration model, the stars formed in a cluster far away from the black hole and then migrated in to form the ring of massive stars. The migration scenario predicts about a million low mass, sun-like stars in and around the ring. In the disk model, the number of low mass stars could be much less.

Researchers used Chandra observations to compare the X-ray glow from the region around Sgr A* to the X-ray emission from thousands of young stars in the Orion Nebula star cluster. They found the Sgr A* star cluster contains only about 10,000 low mass stars, thereby ruling out the migration model. Because the galactic center is shrouded in dust and gas, it has not been possible to look for the low-mass stars in optical observations. X-ray data have allowed astronomers to penetrate the veil of gas and dust and look for these low mass stars.

This research, coauthored by Nayakshin and Rashid Sunyaev of the Max Plank Institute for Physics in Garching, Germany, will appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.

“In one of the most inhospitable places in our galaxy, stars have prevailed,” Nayakshin said. “It appears star formation is much more tenacious than we previously believed.” “We can say the stars around Sgr A* were not deposited there by some passing star cluster, rather they were born there,” Sunyaev said. “There have been theories that this was possible, but this is the first real evidence. Many scientists are going to be very surprised by these results.”

The research suggests the rules of star formation change when stars form in the disk surrounding a giant black hole. Because this environment is very different from typical star formation regions, there is a change in the proportion of stars that form. For example, there is a much higher percentage of massive stars in the disks around black holes.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. For more information about this research on the Web, visit:

Additional information and images are available at:

http://chandra.harvard.edu and http://chandra.nasa.gov

Original Source: Chandra News Release

Artist illustraton of a black hole consuming a neutron star. Image credit: Dana Berry/NASA. Click to enlarge.
Scientists have solved a 35-year-old mystery of the origin of powerful, split-second flashes of light called short gamma-ray bursts. These flashes, brighter than a billion suns yet lasting only a few milliseconds, have been simply too fast to catch… until now.

If you guessed that a black hole is involved, you are at least half right. Short gamma-ray bursts arise from collisions between a black hole and a neutron star or between two neutron stars. In the first scenario, the black hole gulps down the neutron star and grows bigger. In the second scenario, the two neutron stars create a black hole.

Gamma-ray bursts, the most powerful explosions known, were first detected in the late 1960s. They are random, fleeting, and can occur from any region of the sky. Try finding the location of a camera flash somewhere in a vast sports stadium and you’ll have a sense of the challenge facing gamma-ray burst hunters. Solving this mystery took unprecedented coordination among scientists using a multitude of ground-based telescopes and NASA satellites.

Two years ago scientists discovered that longer bursts, lasting over two seconds, arise from the explosion of very massive stars. About 30 percent of bursts, however, are short and under two seconds.

Four short gamma-ray bursts have been detected since May. Two of these are featured in four papers in the October 6 issue of Nature. One burst from July provides the “smoking gun” evidence to support the collision theory. Another burst goes a step further by providing tantalizing, first-time evidence of a black hole eating a neutron star—first stretching the neutron star into a crescent, swallowing it, and then gulping up crumbs of the broken star in the minutes and hours that followed.

These discoveries might also aid in the direct detection of gravitational waves, never before seen. Such mergers create gravitational waves, or ripples in spacetime. Short gamma-ray bursts could tell scientists when and where to look for the ripples.

“Gamma-ray bursts in general are notoriously difficult to study, but the shortest ones have been next to impossible to pin down,” said Dr. Neil Gehrels of NASA Goddard Space Flight Center in Greenbelt, Md., principal investigator of NASA’s Swift satellite and lead author on one of the Nature reports. “All that has changed. We now have the tools in place to study these events.”

The Swift satellite detected a short burst on May 9, and NASA’s High-Energy Transient Explorer (HETE) detected another on July 9. These are the two bursts featured in Nature. Swift and HETE quickly and autonomously relayed the burst coordinates to scientists and observatories via cell phone, beepers and e-mail.

The May 9 event marked the first time scientists identified an afterglow for a short gamma-ray burst, something commonly seen after long bursts. That discovery was the subject of a May 11 NASA press release. The new results published in Nature represent thorough analyses of these two burst afterglows, which clinch the case for the origin of short bursts.

“We had a hunch that short gamma-ray bursts came from a neutron star crashing into a black hole or another neutron star, but these new detections leave no doubt,” said Dr. Derek Fox of Penn State, lead author on one Nature report detailing a multi-wavelength observation.

Fox’s team discovered the X-ray afterglow of the July 9 burst with NASA’s Chandra X-ray Observatory. A team led by Prof. Jens Hjorth of the University of Copenhagen then identified the optical afterglow using the Danish 1.5-meter telescope at the La Silla Observatory in Chile. Fox’s team then continued its studies of the afterglow with NASA’s Hubble Space Telescope; the du Pont and Swope telescopes at Las Campanas, Chile, funded by the Carnegie Institution; the Subaru telescope on Mauna Kea, Hawaii, operated by the National Astronomical Observatory of Japan; and the Very Large Array, a stretch of 27 radio telescopes near Socorro, N.M., operated by the National Radio Astronomy Observatory.

The multi-wavelength observation of the July 9 burst, called GRB 050709, provided all the pieces of the puzzle to solve the short burst mystery.

“Powerful telescopes detected no supernova as the gamma-ray burst faded, arguing against the explosion of a massive star,” said Dr. George Ricker of MIT, HETE Principal Investigator and co-author of another Nature article. “The July 9 burst was like the dog that didn’t bark.”

Ricker added that the July 9 burst and probably the May 9 burst are located in the outskirts of their host galaxies, where old merging binaries are expected to be. Short gamma-ray bursts are not expected in young, star-forming galaxies. It takes billions of years for two massive stars, coupled in a binary system, to first evolve to the black hole or neutron star phase and then to merge. The transition of a star to a black hole or neutron star involves an explosion (supernova) that can kick the binary system far from its origin and out towards the edge of its host galaxy.

This July 9 burst and a later one on July 24 showed unique signals that point to not just any old merger but, more specifically, a black hole – neutron star merger. Scientists saw spikes of X-ray light after the initial gamma-ray burst. The quick gamma-ray portion is likely a signal of the black hole swallowing most of the neutron star. The X-ray signals, in the minutes to hours that followed, could be crumbs of neutron star material falling into the black hole, a bit like dessert.

And there’s more. Mergers create gravitational waves, ripples in spacetime predicted by Einstein but never detected directly. The July 9 burst was about two billion light years away. A big merger closer to the Earth could be detected by the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO). If Swift detects a nearby short burst, LIGO scientists could go back and check the data with a precise time and location in mind.

“This is good news for LIGO,” said Dr. Albert Lazzarini, of LIGO Laboratory at Caltech. “The connection between short bursts and mergers firms up projected rates for LIGO, and they appear to be at the high end of previous estimates. Also, observations provide tantalizing hints of black hole – neutron star mergers, which have not been detected before. During LIGO’s upcoming yearlong observation we may detect gravitational waves from such an event.”

A black hole – neutron star merger would generate stronger gravitational waves than two merging neutron stars. The question now is how common and how close these mergers are. Swift, launched in November 2004, can provide that answer.

Original Source: NASA News Release

Mysterious dust cloud in various wavelengths. Image credit: CfA. Click to enlarge.
In an exercise that demonstrates the power of a multiwavelength investigation using diverse facilities, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have deciphered the true nature of a mysterious object hiding inside a dark cosmic cloud. They found that the cloud, once thought to be featureless, contains a baby star, or possibly a failed star known as a “brown dwarf,” that is still forming within its dusty cocoon.

Observations indicate that the mystery object has a mass about 25 times that of Jupiter, which would place it squarely in the realm of brown dwarfs. However, its mass may eventually grow large enough to qualify it as a small star. The object also is cool and faint, shining with less than 1/20 the sun’s luminosity.

“This object is the runt of the star formation family,” said CfA astronomer Tyler Bourke.

Establishing the true nature of the object required the unique capabilities of the Submillimeter Array (SMA) in Hawaii. “The SMA spotted what no single-dish telescope could see,” said Bourke.

Using the SMA, scientists detected a weak outflow of material predicted by star formation theories. That outflow – 10 times smaller in mass than any seen before – confirmed both the low-mass nature of the object and its association with the surrounding dark cloud. “The sensitivity and resolution of the Submillimeter Array with its multiple antennas were crucial in detecting the outflow,” said Bourke.

The puzzling object was discovered using a Smithsonian-developed infrared camera on board NASA’s Spitzer Space Telescope. Spitzer studied the dusty cosmic cloud named L1014 as part of the Cores to Disks Legacy program. A core is the densest region of a cloud, massive enough to make a star like the sun.

L1014, located about 600 light-years away in the constellation Cygnus the Swan, initially was classified as a “starless core” because it showed no evidence for star formation. Astronomers were surprised when Spitzer images revealed a faint infrared light source that appeared to be within the core.

Additional data were needed to confirm that the faint object was directly associated with the dark core, rather than being a chance superposition of a more distant, more mundane background object.

Near-infrared observations by the MMT Observatory in Arizona revealed a scattered light nebula surrounding the faint central object in L1014. “Light from the object is bouncing off surrounding dust and toward us,” said CfA astronomer Tracy Huard, who took the MMT images. “Reflection nebulosity like that is a fingerprint of an embedded object.”

The apparent size of the nebulosity indicated that the light source likely was located within L1014 and not in a more distant cloud. MMT data also gave investigators the orientation in space, or tilt, of the object within L1014. Astronomers then turned to the SMA for final confirmation.

“The Spitzer observations gave us hints to the nature of the object inside L1014. The MMT strengthened the association between the infrared source and the starless core. The Submillimeter Array clinched the case and revealed this object’s true identity,” said Bourke.

By studying faint, young objects like the one still forming within L1014, astronomers hope to learn more about the early stages of star formation.

“The most elusive part of star formation is the moment of birth,” said CfA astronomer Phil Myers. “In order to answer how it happens, you need examples of very young systems. This system is only about 10,000 to 100,000 years old – a baby as far as stars or brown dwarfs go.”

The combined capabilities of Spitzer, the SMA and the MMT were essential for finding and examining this object. Those facilities undoubtedly will prove useful in studying similar very dim, very young objects – objects so young that they are still growing. “They’re so young and faint that we can’t tell how much mass they will accumulate,” Myers added. “There’s no prenatal test for these objects. We’re not sure exactly what we’ll get in the end!”

A paper by Tyler L. Bourke et al. covering the SMA observations will be published in an upcoming issue of The Astrophysical Journal Letters and is available online at http://arxiv.org/abs/astro-ph/0509865.

A second paper by Tracy L. Huard et al. covering the MMT observations will be published in The Astrophysical Journal and is available online at http://arxiv.org/abs/astro-ph/0509302.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Artist illustration of the 10th planet and its moon. Image credit: Caltech. Click to enlarge.
The newly discovered 10th planet, 2003 UB313, is looking more and more like one of the solar system’s major players. It has the heft of a real planet (latest estimates put it at about 20 percent larger than Pluto), a catchy code name (Xena, after the TV warrior princess), and a Guinness Book-ish record of its own (at about 97 astronomical units-or 9 billion miles from the sun-it is the solar system’s farthest detected object). And, astronomers from the California Institute of Technology and their colleagues have now discovered, it has a moon.

The moon, 100 times fainter than Xena and orbiting the planet once every couple of weeks, was spotted on September 10, 2005, with the 10-meter Keck II telescope at the W.M. Keck Observatory in Hawaii by Michael E. Brown, professor of planetary astronomy, and his colleagues at Caltech, the Keck Observatory, Yale University, and the Gemini Observatory in Hawaii. The research was partly funded by NASA. A paper about the discovery was submitted on October 3 to Astrophysical Journal Letters.

“Since the day we discovered Xena, the big question has been whether or not it has a moon,” says Brown. “Having a moon is just inherently cool-and it is something that most self-respecting planets have, so it is good to see that this one does too.”

Brown estimates that the moon, nicknamed “Gabrielle”-after the fictional Xena’s fictional sidekick-is at least one-tenth of the size of Xena, which is thought to be about 2700 km in diameter (Pluto is 2274 km), and may be around 250 km across.

To know Gabrielle’s size more precisely, the researchers need to know the moon’s composition, which has not yet been determined. Most objects in the Kuiper Belt, the massive swath of miniplanets that stretches from beyond Neptune out into the distant fringes of the solar system, are about half rock and half water ice. Since a half-rock, half-ice surface reflects a fairly predictable amount of sunlight, a general estimate of the size of an object with that composition can be made. Very icy objects, however, reflect a lot more light, and so will appear brighter-and thus bigger-than similarly sized rocky objects.

Further observations of the moon with NASA’s Hubble Space Telescope, planned for November and December, will allow Brown and his colleagues to pin down Gabrielle’s exact orbit around Xena. With that data, they will be able to calculate Xena’s mass, using a formula first devised some 300 years ago by Isaac Newton.

“A combination of the distance of the moon from the planet and the speed it goes around the planet tells you very precisely what the mass of the planet is,” explains Brown. “If the planet is very massive, the moon will go around very fast; if it is less massive, the moon will travel more slowly. It is the only way we could ever measure the mass of Xena-because it has a moon.”

The researchers discovered Gabrielle using Keck II’s recently commissioned Laser Guide Star Adaptive Optics system. Adaptive optics is a technique that removes the blurring of atmospheric turbulence, creating images as sharp as would be obtained from space-based telescopes. The new laser guide star system allows researchers to create an artificial “star” by bouncing a laser beam off a layer of the atmosphere about 75 miles above the ground. Bright stars located near the object of interest are used as the reference point for the adaptive optics corrections. Since no bright stars are naturally found near Xena, adaptive optics imaging would have been impossible without the laser system.

“With Laser Guide Star Adaptive Optics, observers not only get more resolution, but the light from distant objects is concentrated over a much smaller area of the sky, making faint detections possible,” says Marcos van Dam, adaptive optics scientist at the W.M. Keck Observatory, and second author on the new paper.

The new system also allowed Brown and his colleagues to observe a small moon in January around 2003 EL61, code-named “Santa,” another large new Kuiper Belt object. No moon was spotted around 2005 FY9-or “Easterbunny”-the third of the three big Kuiper Belt objects recently discovered by Brown and his colleagues using the 48-inch Samuel Oschin Telescope at Palomar Observatory. But the presence of moons around three of the Kuiper Belt’s four largest objects-Xena, Santa, and Pluto-challenges conventional ideas about how worlds in this region of the solar system acquire satellites.

Previously, researchers believed that Kuiper Belt objects obtained moons through a process called gravitational capture, in which two formerly separate objects moved too close to one another and become entrapped in each other’s gravitational embrace. This was thought to be true of the Kuiper Belt’s small denizens-but not, however, of Pluto. Pluto’s massive, closely orbiting moon, Charon, broke off the planet billions of years ago, after it was smashed by another Kuiper Belt object. Xena’s and Santa’s moons appear best explained by a similar origin.

“Pluto once seemed a unique oddball at the fringe of the solar system,” Brown says. “But we now see that Xena, Pluto, and the others are part of a diverse family of large objects with similar characteristics, histories, and even moons, which together will teach us much more about the solar system than any single oddball ever would.”

Original Source: Caltech News Release

Spiral Galaxy NGC 1350. Image credit: ESO. Click to enlarge.
Eighty-five million years ago on small planet Earth, dinosaurs ruled, ignorant of their soon-to-come demise in the great Jurassic extinction, while mammals were still small and shy creatures. The southern Andes of Bolivia, Chile, and Argentina were not yet formed and South America was still an island continent.

Eighty-five million years ago, our Sun and its solar system was 60,000 light years away from where it now stands [1].

Eighty-five million years ago, in another corner of the Universe, light left the beautiful spiral galaxy NGC 1350, for a journey across the universe. Part of this light was recorded at the beginning of the year 2000 AD by ESO’s Very Large Telescope, located on the 2,600m high Cerro Paranal in the Chilean Andes on planet Earth.

Astronomers classify NGC 1350 as an Sa(r) type galaxy, meaning it is a spiral with large central regions. In fact, NGC 1350 lies at the border between the broken-ring spiral type and a grand design spiral with two major outer arms. It is about 130,000 light-years across and, hence, is slightly larger than our Milky Way.

The rather faint and graceful outer arms originate at the inner main ring and can be traced for almost half a circle when they each meet the opposite arm, giving the impression of completing a second outer ring, the “eye”. The arms are given a blue tint as a result of the presence of very young and massive stars. The amount of dust, seen as small fragmented dust spirals in the central part of the galaxy and producing a fine tapestry that bear resemblance with blood vessels in the eye, is also a signature of the formation of stars.

The outer parts of the galaxy are so tenuous that many background galaxies can be seen shining through them, providing the observers with an awesome sense of depth. It is indeed quite remarkable to see that with a total exposure time of only 16 minutes, the VLT lets us admire such an incredible collection of island universes wandering about in the sky. ESO PR Photo 31b/05 is a mosaic of some of the most prominent galaxies found in the images. Some of these may reside as far as several billion light-years away, i.e. the light from these galaxies was emitted when the Sun and the Earth had not yet formed.

NGC 1350 is located in the rather inconspicuous southern Fornax (The Furnace) constellation [2]. Recessing from us at a speed of 1860 km/s [3], it is eighty-five million light-years away. It is thus most probably not a member of the Fornax cluster of galaxies, the most notable entity in the constellation, that lies about 65 million light-years away and contains the much more famous barred spiral NGC 1365. On the sky, NGC 1350 stands on the outskirts of the Fornax cluster as can be seen on this image taken with the 1m-Schmidt telescope at La Silla.

Original Source: ESO News Release

A distant supernova that exploded 41,000 years ago may have led to the extinction of the mammoth, according to research conducted by nuclear scientist Richard Firestone of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

Firestone, who collaborated with Arizona geologist Allen West on this study, unveiled this theory Sept. 24 at the 2nd International Conference “The World of Elephants” in Hot Springs, SD. Their theory joins the list of possible culprits responsible for the demise of mammoths, which last roamed North America roughly 13,000 years ago. Scientists have long eyed climate change, disease, or intensive hunting by humans as likely suspects.

Now, a supernova may join the lineup. Firestone and West believe that debris from a supernova explosion coalesced into low-density, comet-like objects that wreaked havoc on the solar system long ago. One such comet may have hit North America 13,000 years ago, unleashing a cataclysmic event that killed off the vast majority of mammoths and many other large North American mammals. They found evidence of this impact layer at several archaeological sites throughout North America where Clovis hunting artifacts and human-butchered mammoths have been unearthed. It has long been established that human activity ceased at these sites about 13,000 years ago, which is roughly the same time that mammoths disappeared.

They also found evidence of the supernova explosion’s initial shockwave: 34,000-year-old mammoth tusks that are peppered with tiny impact craters apparently produced by iron-rich grains traveling at an estimated 10,000 kilometers per second. These grains may have been emitted from a supernova that exploded roughly 7,000 years earlier and about 250 light years from Earth.

“Our research indicates that a 10-kilometer-wide comet, which may have been composed from the remnants of a supernova explosion, could have hit North America 13,000 years ago,” says Firestone. “This event was preceded by an intense blast of iron-rich grains that impacted the planet roughly 34,000 years ago.”

In support of the comet impact, Firestone and West found magnetic metal spherules in the sediment of nine 13,000-year-old Clovis sites in Michigan, Canada, Arizona, New Mexico and the Carolinas. Low-density carbon spherules, charcoal, and excess radioactivity were also found at these sites.

“Armed with only a magnet and a Geiger counter, we found the magnetic particles in the well-dated Clovis layer all over North America where no one had looked before,” says Firestone.

Analysis of the magnetic particles by Prompt Gamma Activation Analysis at the Budapest Reactor and by Neutron Activation Analysis at Canada’s Becquerel Laboratories revealed that they are rich in titanium, iron, manganese, vanadium, rare earth elements, thorium, and uranium. This composition is very similar to lunar igneous rocks, called KREEP, which were discovered on the moon by the Apollo astronauts, and have also been found in lunar meteorites that fell to Earth in the Middle East an estimated 10,000 years ago.

“This suggests that the Earth, moon, and the entire solar system were bombarded by similar materials, which we believe were the remnants of the supernova explosion 41,000 years ago,” says Firestone.

In addition, Berkeley Lab’s Al Smith used the Lab’s Low-Background Counting Facility to detect the radioactive isotope potassium-40 in several Clovis arrowhead fragments. Researchers at Becquerel Laboratories also found that some Clovis layer sediment samples are significantly enriched with this isotope.

“The potassium-40 in the Clovis layer is much more abundant than potassium-40 in the solar system. This isotope is formed in considerable excess in an exploding supernova, and has mostly decayed since the Earth was formed,” says Firestone. “We therefore believe that whatever hit the Earth 13,000 years ago originated from a recently exploded supernova.”

Firestone and West also uncovered evidence of an even earlier event that blasted parts of the Earth with iron-rich grains. Three mammoth tusks found in Alaska and Siberia, which were carbon-dated to be about 34,000 years old, are pitted with slightly radioactive, iron-rich impact sites caused by high-velocity grains. Because tusks are composed of dentine, which is a very hard material, these craters aren’t easily formed. In fact, tests with shotgun pellets traveling 1,000 kilometers per hour produced no penetration in the tusks. Much higher energies are needed: x-ray analysis determined that the impact depths are consistent with grains traveling at speeds approaching 10,000 kilometers per second.

“This speed is the known rate of expansion of young supernova remnants,” says Firestone.

The supernova’s one-two punch to the Earth is further corroborated by radiocarbon measurements. The timeline of physical evidence discovered at Clovis sites and in the mammoth tusks mirrors radiocarbon peaks found in Icelandic marine sediment samples that are 41,000, 34,000, and 13,000 years old. Firestone contends that these peaks, which represent radiocarbon spikes that are 150 percent, 175 percent, and 40 percent above modern levels, respectively, can only be caused by a cosmic ray-producing event such as a supernova.

“The 150 percent increase of radiocarbon found in 41,000-year-old marine sediment is consistent with a supernova exploding 250 light years away, when compared to observations of a radiocarbon increase in tree rings from the time of the nearby historical supernova SN 1006,” says Firestone.

Firestone adds that it would take 7,000 years for the supernova’s iron-rich grains to travel 250 light years to the Earth, which corresponds to the time of the next marine sediment radiocarbon spike and the dating of the 34,000-year-old mammoth tusks. The most recent sediment spike corresponds with the end of the Clovis era and the comet-like bombardment.

“It’s surprising that it works out so well,” says Firestone.

Original Source: Berkeley Labs News Release

13 distant galaxies found in a sample of sky. Image credit: ESO. Click to enlarge.
It is one of the major goals of observational cosmology to trace the way galaxies formed and evolved and to compare it to predictions from theoretical models. It is therefore essential to know as precisely as possible how many galaxies were present in the Universe at different epochs.

This is easier to say than to do. Indeed, if counting galaxies from deep astronomical images is relatively straightforward, measuring their distance – hence, the epoch in the history of the universe where we see it [1] – is much more difficult. This requires taking a spectrum of the galaxy and measuring its redshift [2].

However, for the faintest galaxies – that are most likely the farthest and hence the oldest – this requires a lot of observing time on the largest of the telescopes. Until now, astronomers had thus to first carefully select the candidate high-redshift galaxies, in order to minimise the time spent on measuring the distance. But it seems that astronomers were too careful in doing so, and hence had a wrong picture of the population of galaxies.

It would be better to “simply” observe in a given patch of the sky all galaxies brighter than a given limit. But looking at one object at a time would make such a study impossible.

To take up the challenge, a team of French and Italian astronomers [3] used the largest possible telescope with a highly specialised, very sensitive instrument that is able to observe a very large number of (faint) objects in the remote universe simultaneously.

The astronomers made use of the VIsible Multi-Object Spectrograph (VIMOS) on Melipal, one of the 8.2-m telescopes of ESO’s Very Large Telescope Array. VIMOS can observe the spectra of about 1,000 galaxies in one exposure, from which redshifts, hence distances, can be measured. The possibility to observe two galaxies at once would be equivalent to using two VLT Unit Telescopes simultaneously. VIMOS thus effectively multiplies the efficiency of the VLT hundreds of times.

This makes it possible to complete in a few hours observations that would have taken months only a few years ago. With capabilities up to ten times more productive than competing instruments, VIMOS offers the possibility for the first time to conduct an unbiased census of the distant Universe.

Using the high efficiency of the VIMOS instrument, the team of astronomers embarked in the VIMOS VLT Deep Survey (VVDS) whose aim is to measure in some selected patch of the sky the redshift of all galaxies brighter than magnitude 24 in the red, that is, galaxies that are up to 16 million fainter than what the unaided eye can see.

In a total sample of about 8,000 galaxies selected only on the basis of their observed brightness in red light, almost 1,000 bright and vigorously star forming galaxies were discovered at an epoch 1,500 to 4,500 million years after the Big Bang (redshift between 1.4 and 5).

“To our surprise”, says Olivier Le F?vre, from the Laboratoire d’Astrophysique de Marseille (France) and co-leader of the VVDS project, “this is two to six times higher than had been found by previous works. These galaxies had been missed because previous surveys had selected objects in a much more restrictive manner than we did. And they did so to accommodate the much lower efficiency of the previous generation of instruments.”

While observations and models have consistently indicated that the Universe had not yet formed many stars in the first billion years of cosmic time, the discovery made by the scientists calls for a significant change in this picture.

Combining the spectra of all the galaxies in a given redshift range (i.e. belonging to the same epoch), the astronomers could estimate the amount of star formed in these galaxies. They find that the galaxies in the young Universe transform into stars between 10 and 100 times the mass of our Sun in a year.

“This discovery implies that galaxies formed many more stars early in the life of the Universe than had previously been thought”, explains Gianpaolo Vettolani, the other co-leader of the VVDS project, working at INAF-IRA in Bologna (Italy). “These observations will demand a profound reassessment of our theories of the formation and evolution of galaxies in a changing Universe.”

It now remains for astronomers to explain how one can create such a large population of galaxies, producing more stars than previously assumed, at a time when the Universe was about 10-20% of its current age.

Original Source: ESO News Release