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terça-feira, 5 de fevereiro de 2008
Opening up the infrared sky
Image catches Pickering's Triangle
A new double-wide image of the piece of Cygnus Loop was released.
Provided by NOAO
 This image of Pickering's Triangle was taken with the National Science Foundation's Mayall 4-meter telescope at Kitt Peak National Observatory. T.A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF [View Larger Image] A new wide-field image of Pickering's Triangle is being released today in Austin, Texas, at the 211th meeting of the American Astronomical Society. The image was taken with the National Science Foundation's Mayall 4-meter telescope at Kitt Peak National Observatory. Pickering's Triangle is part of the Cygnus Loop supernova remnant, which includes the famous Veil Nebula. It is located about 1,500 light-years from Earth, in the constellation Cygnus, the Swan. Astronomers estimate that the supernova explosion that produced the nebula occurred between 5,000 to 10,000 years ago; the entire shell stretches more than six full Moons in width across the sky. This new image was obtained September 2007 by Travis Rector and Heidi Schweiker by combining two full pointings of the 64-megapixel NOAO Mosaic-1 imager, mounted on the historic Mayall telescope. |
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Piercing the Veil
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Stars in the Middle of Nowhere
Stars form in galaxies, right? Usually, but apparently not always. Astronomers have found several young star clusters that don't belong to any particular galaxy. "They're in the middle of nowhere," says Duilia de Mello (Catholic University of America and NASA/Goddard Space Flight Center), who described her team's discovery at this week's meeting of the American Astronomical Society in Austin, Texas.
The clusters announced their presence in ultraviolet images of the Messier 81 galaxy group made with NASA's Galaxy Evolution Explorer (GALEX). Located in Ursa Major near the bowl of the Big Dipper, the group includes the stately spiral M81 and cigar-shaped M82, an irregular galaxy undergoing a burst of star formation. 
GALEX found a motley assortment of unidentified "blue blobs" scattered through intergalactic space near the galaxies.
M81, M82, and another galaxy known as NGC 3077 are known to be participating in a three-way cosmic ballet. Radio maps show the trio enmeshed in a vast swirl of hydrogen gas torn from the galaxies during close encounters between them. The blue blobs seen by GALEX appear coincident with a gaseous arc called Arp's Loop.
As it turns out, this region had been viewed by the Hubble Space Telescope's ultrahigh-resolution Advanced Camera for Surveys. Upon pulling the image from the Hubble archive, de Mello and her colleagues were astonished to see the blobs resolved into clusters of stars. The gas in Arp's Loop was thought much too rarefied to condense into stars.
Judging from their brightnesses and colors, the clusters appear quite young, with stars ranging in age from 10 million to 200 million years. Not coincidentally, M81 and M82 had their last close interaction 200 million years ago, and Arp's Loop is thought to have been drawn out of the galaxies during the mashup. De Mello proposes that turbulence from the encounter created some knots of gas dense enough to trigger star formation, leading to the free-floating clusters we see there now.
An ultraviolet view of galaxies M81 and M82 in Ursa Major, from the GALEX spacecraft, reveals numerous "blue blobs" in the space around them. Close-ups from the Hubble Space Telescope resolve these clumps into myriad stars. These appear to have formed in the wake of a collision between M81 and M82 about 200 million years ago.
NASA / ESA / D. de Mello
The clusters announced their presence in ultraviolet images of the Messier 81 galaxy group made with NASA's Galaxy Evolution Explorer (GALEX). Located in Ursa Major near the bowl of the Big Dipper, the group includes the stately spiral M81 and cigar-shaped M82, an irregular galaxy undergoing a burst of star formation.
This map shows radio emissions from hydrogen gas in and around the galaxies M81 (the large spiral), M82 (top), and NGC 3077 (lower left). The three systems are locked in a gravitational embrace, as evidenced by the tidal arcs of gas torn out of the galaxies during their interactions.
NRAO / AUI
M81, M82, and another galaxy known as NGC 3077 are known to be participating in a three-way cosmic ballet. Radio maps show the trio enmeshed in a vast swirl of hydrogen gas torn from the galaxies during close encounters between them. The blue blobs seen by GALEX appear coincident with a gaseous arc called Arp's Loop.
As it turns out, this region had been viewed by the Hubble Space Telescope's ultrahigh-resolution Advanced Camera for Surveys. Upon pulling the image from the Hubble archive, de Mello and her colleagues were astonished to see the blobs resolved into clusters of stars. The gas in Arp's Loop was thought much too rarefied to condense into stars.
Judging from their brightnesses and colors, the clusters appear quite young, with stars ranging in age from 10 million to 200 million years. Not coincidentally, M81 and M82 had their last close interaction 200 million years ago, and Arp's Loop is thought to have been drawn out of the galaxies during the mashup. De Mello proposes that turbulence from the encounter created some knots of gas dense enough to trigger star formation, leading to the free-floating clusters we see there now.
When worlds collide
Have astronomers observed the aftermath of a distant planetary collision?
Provided by Harvard-Smithsonian CfA
 Illustrated here in this artist's concept, astronomers may have observed the aftermath of a collision between two protoplanets, one Jupiter-sized and one Neptune-sized, in the system 2M1207. David A. Aguilar (Harvard-Smithsonian CfA) [View Larger Image] Astronomers announced today that a mystery object orbiting a star 170 light-years from Earth might have formed from the collision and merger of two protoplanets. The object, known as 2M1207B, has puzzled astronomers since its discovery because it seems to fall outside the spectrum of physical possibility. Its temperature, luminosity, age, and location do not match up with any theory. "This is a strange enough object that it needs a strange explanation," says Eric Mamajek of the Harvard-Smithsonian Center for Astrophysics (CfA). The announcement was made in a press conference at the 211th meeting of the American Astronomical Society. 2M1207B orbits a 25-Jupiter-mass brown dwarf called 2M1207A seen in the direction of the constellation Centaurus. Computer models show that 2M1207A is very young, only about 8 million years old; therefore its companion should also be 8 million years old. At that age, it should have cooled to a temperature of less than 1300° F (1000 K). However, observations show that 2M1207B is actually about 2400° F (1600 K). The extra heat might be the result of a protoplanetary collision. "Most, if not all, planets in our solar system were hit early in their history. A collision created Earth's moon and knocked Uranus on its side," explains Mamajek. "It's quite likely that major collisions happen in other young planetary systems, too." Given its temperature, astronomers would expect a certain luminosity for 2M1207B, but it is 10 times fainter than expected. In 2006, astronomers suggested that it is obscured by a dusty, edge-on disk. Mamajek and his colleague, Michael Meyer of the University of Arizona, propose an alternative explanation: 2M1207B is small, only about the size of Saturn, and therefore has a smaller-than-expected surface area radiating energy. They derive a radius of 31,000 miles (50,000 km) for 2M1207B, compared to 37,000 miles (60,000 km) for Saturn. Given typical densities for giant planets, this would give 2M1207B a mass about 80 times Earth (or one-fourth Jupiter). The only plausible way for such a small object to be so hot millions of years after it formed is if it suffered a recent, titanic collision that heated it. The planets in our solar system assembled from dust, rock, and gas, gradually growing larger over millions of years. But sometimes, two planet-sized objects collided catastrophically. For example, the Moon formed when an object about half the size of Mars hit the proto-Earth. If planet formation works the same way in other star systems, then 2M1207B might be the product of a collision between a Saturn-sized gas giant and a planet about three times the size of Earth. The two smacked into each other and stuck, forming one larger world still boiling from the heat generated in the collision. "The Earth was hit by something one-tenth its mass, and it's likely that other planets in our solar system were too, including Venus and Uranus," explains Meyer. "If that one-tenth scale holds in other planetary systems, then we could be seeing the aftermath of a collision between a 72 Earth-mass gas giant and an 8 Earth-mass planet, even though such collisions are very unlikely." Mamajek also points out that the collision theory is reasonable from a timescale point of view. A 2400-degree, Saturn-sized object would radiate its heat away over about 100,000 years. If the system were billions of years old, it is unlikely that we would be looking at the right time, but since the system is young, the chances are much better that we would catch it shortly after the collision while the hot aftermath is still observable. The collision hypothesis makes several predictions that astronomers can test. Chief among them is a low surface gravity (which depends on a planet's mass and radius). To check this prediction, astronomers will need to get a better spectrum of 2M1207B, a challenge since it is very faint and very close to the brown dwarf 2M1207A. Others are checking the dusty disk theory by looking for signs of polarization in the light from 2M1207B. More answers should be forthcoming within a year or two. Mamajek emphasizes that while a planet collision may not be the correct explanation for the weirdness of 2M1207B, examples of colliding planets are likely to be found by the next generation of ground-based telescopes. "Hot, post-collision planets might be a whole new class of objects we will see with the Giant Magellan Telescope." "Even if we're wrong, I wouldn't be surprised if someone finds a clear-cut case in the next 10 years," Mamajek adds. |
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New X-ray source in nearby galaxy spawns mystery
OHIO STATE UNIVERSITY NEWS RELEASE
Posted: January 9, 2008
AUSTIN, Texas -- Astronomers studying a nearby galaxy have spied a rare type of star system -- one that contains a black hole that suddenly began glowing brightly with X-rays.
Though this type of star system is supposed to be rare, it's the second such system discovered in that galaxy, called Centaurus A.
The discovery suggests that astronomers have more to learn about the lives and deaths of massive stars in galaxies such as our own.
Normally when astronomers study Centaurus A, it's the giant X-ray jets emanating from the heart of the galaxy that steal the show, explained Gregory Sivakoff, a postdoctoral researcher in astronomy at Ohio State University. The jets extend from the galaxy for 13,000 light years in different directions.
But when his team studied Centaurus A with NASA's Chandra X-ray Observatory starting in March 2007, they saw a new X-ray source -- much smaller than the X-ray jets, but still glowing brightly. The source wasn't there during the last survey of the galaxy in 2003, but it shined throughout the time of the new observations, from March to May of 2007.
Because it hadn't been seen before, the astronomers classified the object as a "transient" X-ray source, meaning that the object had been there before 2007, but had only recently brightened enough to stand out.
Sivakoff discussed the results in a press briefing at the American Astronomical Society meeting in Austin, Texas.
The newly bright object, dubbed CXOU J132518.2-430304, is most likely a binary star system, the researchers concluded. The two stars likely formed at the same time, with one much more massive than the other. The more massive star evolved more quickly, and collapsed to form a black hole. It is now slowly devouring its companion. Such binary systems are thought to be extremely rare.
But this is the second bright, transient X-ray binary system discovered in Centaurus A -- and that's the problem, Sivakoff said.
"When we look at other galaxies like Centaurus A, we don't see these bright, transient X-ray binaries," he said. "But now we've found two such objects in Centaurus A, and the implication is that we may not understand these objects as well as we thought we did."
"So right now, our discovery is actually pointing to a puzzle rather than a solution."
Because Centaurus A is near to our galaxy, astronomers have long hoped to use it as a Rosetta stone for studying other galaxies with black holes.
As astronomers piece together an explanation for the existence of the newly-discovered binary system, they may gain a better understanding of how black holes form from massive stars and how binary systems evolve.
"These binary systems are signposts of the massive stars that once existed in galaxies like Centaurus A. To understand the massive stars, we must first know how to read the signs," he said.
Sivakoff and Ralph Kraft of the Harvard-Smithsonian Center for Astrophysics led the study; their collaborators were from NASA Goddard Space Flight Center, Oak Ridge Associated Universities, University of Hertfordshire, University of Virginia, University of Bristol, McMaster University, and the University of Birmingham.
This research was sponsored by NASA.
Posted by:
Lucimary Vargas
Além Paraíba-MG-Brasil
observatorio.monoceros@gmail.com
UNIVERSITY OF ARIZONA NEWS RELEASE
Posted: January 10, 2008
Something bizarre orbiting a young, failed star 170 light-years from Earth may be the progeny of two protoplanets that collided and merged, astronomers announced at the American Astronomical Society meeting in Austin, Texas.
Given its hotter-than-expected temperature, dim luminosity, young age and location, the orbiting object, known as 2M1207B, should be a physical impossibility, scientists say.
"This is a strange enough object that it needs a strange explanation," Eric Mamajek of the Harvard-Smithsonian Center for Astrophysics said.
Mamajek and Michael Meyer of The University of Arizona propose that the object orbiting brown dwarf 2M1207A is small, about the size of Saturn. The "brown dwarf," or failed star, in the system is believed to be 25 times as massive as Jupiter and only about eight million years old.
The brown dwarf might be the outcome of a collision between a Saturn-sized gas giant and a planet about three times the size of Earth, Mamajek and Meyer suggest. The two smacked into each other and fused, forming one larger world still boiling from the heat generated in the titanic collision.
"Most, if not all, planets in our solar system were hit early in their history," Mamajek said. "A collision created Earth's moon and knocked Uranus on its side. It's quite likely that major collisions happen in other young planetary systems, too."
"The Earth was hit by something one-tenth its mass, and it's likely that other planets in our solar system were, too, including Venus and Uranus," Meyer said. "If that one-tenth scale holds in other planetary systems, then we could be seeing the aftermath of a collision between a 72 Earth-mass gas giant and an eight Earth-mass planet."
The collision theory is reasonable from a timescale point of view, Mamajek said. A 2400-degree Fahrenheit, Saturn-sized object would radiate its heat away over about 100,000 years. If the system were billions of years old, it is unlikely that astronomers would be looking at the right time, but because the system is only eight million years old, chances are much better that they would catch it shortly after the collision, when they could still see the hot aftermath.
The collision hypothesis makes several predictions that astronomers can test. Chief among them is a low surface gravity, which depends on a planet's mass and radius. To check this prediction, astronomers will need to get a better spectrum of 2M1207B. That's challenging because the object is very faint and very close to the brown dwarf 2M1207A.
Mamajek emphasized that while a planet collision may not be the correct explanation for the weirdness of 2M1207B, examples of colliding planets are likely to be found by the next generation of ground-based telescopes.
"Hot, post-collision planets might be a whole new class of objects we will see with the Giant Magellan Telescope."
Harvard and UA are members of an international consortium building the Giant Magellan Telescope, which is slated for completion in 2016 at a site in northern Chile. It will be composed of seven 8.4-meter primary mirrors arranged in a hexagonal pattern, giving it 4.5 times the collecting area of any current optical telescope. The UA Steward Observatory Mirror Lab cast the first GMT mirror in 2005.
"Even if we're wrong, I wouldn't be surprised if someone finds a clear-cut case in the next 10 years," Mamajek added.
Lucimary Vargas
Além Paraíba-MG-Brasil
observatorio.monoceros@gmail.com
Dark matter found in accretion disks
This new discovery suggests major revisions to concepts of disk structure and luminosity.
Provided by NOAO
 An artist's concept of the accretion disk around the binary star system WZ Sge. This image shows the previous concept. P. Marenfeld and NOAO/AURA/NSF [View Larger Image] Observations of the interacting binary star using telescopes at Kitt Peak National Observatory and NASA's Spitzer Space Telescope suggest that the disks of hot gas that accumulate around a wide variety of astronomical objects, from degenerate stars in energetic binary systems to supermassive black holes at the hearts of active galaxies, are likely to be much larger than previously believed. The target of this specific investigation, named WZ Sagittae (WZ Sge), is an interacting binary star located in the constellation Sagitta, the arrow of the archer Sagittarius. As part of a program called the Spitzer-NOAO Observing Program for Teachers and Students, Steve B. Howell and a team of astronomers and educators imaged WZ Sge using the National Science Foundation's 2.1-meter telescope and the WIYN 0.9-meter telescope, both located at Kitt Peak, and the Infrared Array Camera (IRAC) on Spitzer. "We were very surprised to see the contrasting results obtained with the optical telescopes on the ground and the infrared telescope in space," says Howell, an astronomer at the National Optical Astronomy Observatory (NOAO) and leader of the team who made the discovery that was reported Wednesday in Austin, Texas, at the 211th meeting of the American Astronomical Society (AAS). "The much larger size of the infrared-emitting portion of the accretion disk around WZ Sge was immediately obvious in the data. Our observations strongly imply the presence of dark matter in these structures, which are ubiquitous throughout the universe." Interacting binary stars such as WZ Sge contain a white dwarf star (a compact star about the size of the Earth, but with a mass near that of the Sun) and a larger, but less massive and much cooler companion star. The companion, usually a low-mass star or a brown dwarf, has material ripped off its surface by the stronger gravity of the white dwarf. This material flows toward the more massive star and, in the process, forms a disk surrounding the white dwarf, known as an accretion disk. |
 This image is an artist's conception of the revised concept of the accretion disk using new data from Kitt Peak Observatory and the Spitzer Space Telescope. P. Marenfeld and NOAO/AURA/NSF [View Larger Image] Whether they form in cataclysmic variable systems or they surround the massive black hole hearts of active galaxies, accretion disks have been well observed and modeled using measurements obtained across much of the electromagnetic spectrum, from X-rays to the near-infrared. The derived picture of the "standard accretion disk" model is a geometrically thin disk of gaseous material surrounding the white dwarf or black hole. Accretion disk models, bolstered by observation, are generally composed of hot gas having a temperature distribution within them, being hottest near the center and falling off in temperature toward the outer edge. In order to confirm the general accretion disk models and extend them into the mid-infrared portion of the spectrum, Howell's team obtained the first time series observations of an accretion disk system at 4.5 and 8 microns with the Spitzer Space Telescope. At nearly the same time, they obtained optical observations of WZ Sge at Kitt Peak. The optical observations confirmed the standard view of the accretion disk size and temperature, values known for over a decade. The mid-infrared observations, however, were completely unexpected and revealed that a larger, thicker disk of cool dusty material surrounds much of the gaseous accretion disk. This outer dust disk likely contains as much mass as a medium-sized asteroid. The newly discovered outer disk extends about 20 times the radius of the gaseous disk. "This discovery suggests that our current model for accretion disks of all kinds is wrong," says team member Donald Hoard of the Spitzer Science Center. "We will need to rethink and recast these models for accretion disks, not only in interacting binary stars but also in distant, highly luminous active galaxies." The implications from such a discovery are far reaching, affecting not only the theoretical models (since the formation and evolution of the disks are modeled based on their size, temperature, and composition-all quantities that now need to be revised), but also nearly all previous observations of systems containing accretion disks. In addition, the dust disk (which is thicker than the known gaseous disk) blocks infrared light emitted by the compact central object and the inner hot regions of the gaseous disk. Not knowing that some mid to far infrared light is blocked by the newly discovered outer dust ring can lead observers to significantly underestimate the total luminosity of the central object. "The amount of this underestimation is not yet accurately known from our initial discovery, but may be as large as 50 percent," Howell says. |
Caught in the cosmic-matter web
Astronomers are using Hubble to dissect one of the largest structures in the universe as part of a quest to understand the violent lives of galaxies.
Provided by Hubble/ESA
 This image reveals the distribution of dark matter in the supercluster Abell 901/902, which is composed of hundreds of galaxies. The image shows the entire supercluster. NASA/ESA/C. Heymans/M. Gray/M. Barden/STAGES [View Larger Image] The images are part of the Space Telescope Abell 901/902 Galaxy Evolution Survey (STAGES), which covers one of the largest patches of sky ever observed by the Hubble Space Telescope. The area surveyed is so wide that it took 80 Hubble images to cover the entire STAGES field, measuring about 0.5°×0.5° on the sky. The new work is led by Meghan Gray of the University of Nottingham in the United Kingdom and Catherine Heymans of the University of British Columbia in Vancouver, along with an international team of scientists. The Hubble study pinpointed four main areas in the supercluster where dark matter has pooled into dense clumps, totaling 1012 times the Sun's mass. These areas match the location of hundreds of old galaxies that have experienced a violent history in their passage from the outskirts of the supercluster into these dense regions. These galaxies make up four separate galaxy clusters. "Thanks to Hubble's Advanced Camera for Surveys, we are detecting for the first time the irregular clumps of dark matter in this supercluster," Heymans says. "We can even see an extension of the dark matter toward a very hot group of galaxies that are emitting X-rays as they fall into the densest cluster core." The dark matter map was constructed by measuring the distorted shapes of over 60,000 faraway galaxies. To reach Earth, the galaxies' light traveled through the dark matter that surrounds the supercluster galaxies and was bent by the massive gravitational field. Heymans used the observed, subtle distortion of the galaxies' shapes to reconstruct the dark matter distribution in the supercluster using a method called weak gravitational lensing. The new dark matter map is 2.5 times sharper than that from a previous ground-based survey of the supercluster. |
 A Hubble study pinpointed four main areas in the Abell 901/902 supercluster where dark matter has pooled into dense clumps. These areas match the location of hundreds of galaxies that have experienced a violent history in their passage from the outskirts of the supercluster into these dense regions. This image shows one of the four main areas. NASA/ESA/C. Heymans/M. Gray/M. Barden/STAGES [View Larger Image] On Earth, the pace of quiet country life is vastly different from the hustle of the big city. In the same way, galaxies living lonely isolated lives look very different from those found in the most crowded regions of the universe, like a supercluster. "We've known for a long time that galaxies in crowded environments tend to be older, redder, and rounder than those in the field," Gray says. "Galaxies are continually drawn into larger and larger groups and clusters by the inevitable force of gravity as the universe evolves." In such busy environments galaxies are subject to a life of violence: high-speed collisions with other galaxies; the stripping away of gas, the fuel supply they use to form new stars; and distortion due to the strong gravitational pull of the underlying invisible dark matter. "Any or all of these effects may play a role in the transformation of galaxies, which is what we're trying to determine," Gray says. The STAGES survey's simultaneous focus on both the big picture and the details can be likened to studying a big city. "It's as if we're trying to learn everything we can about New York City and New Yorkers," Gray explains. "We're examining large-scale features, like mapping the roads, counting skyscrapers, monitoring traffic. At the same time we're also studying the residents to figure out how the lifestyles of people living downtown differ from those out in the suburbs. But in our case the city is a supercluster, the roads are dark matter, and the people are galaxies." Further results by other team members support this view. "In the STAGES supercluster we clearly see that transformations are happening in the outskirts of the supercluster, where galaxies are still moving relatively slowly and first feel the influence of the cluster environment," says Christian Wolf, an Advanced Research Fellow at the University of Oxford in the U.K. Assistant professor Shardha Jogee and graduate student Amanda Heiderman, both of the University of Texas in Austin, concur. "We see more collisions between galaxies in the regions toward which the galaxies are flowing than in the centers of the clusters," Jogee says. "By the time they reach the center, they are moving too fast to collide and merge, but in the outskirts their pace is more leisurely, and they still have time to interact." The STAGES team also finds that the outer parts of the clusters are where star formation in the galaxies is slowly switching off and where the supermassive black holes at the hearts of the galaxies are most active. "The galaxies at the centres of the clusters may have been there for a long time and have probably finished their transformation," adds Heiderman. "They are now old, round, red, and dead." The team plans more studies to understand how the supercluster environment is responsible for producing these changes. Abell 901/902 resides 2600 million light-years from Earth and measures more than 16 million light-years across. |
Blue blobs' in space are orphaned clusters of stars
SPACE TELESCOPE SCIENCE INSTITUTE NEWS RELEASE
Posted: January 9, 2008
Finding blue blobs in space sounds like an encounter with an alien out of a science fiction movie. But the Hubble Space Telescope's powerful vision has resolved strange objects nicknamed "blobs" and found them to be brilliant blue clusters of stars born in the swirls and eddies of a galactic smashup 200 million years ago.
The findings are being reported by Duilia de Mello of the Catholic University of America, Washington, D.C. and NASA's Goddard Space Flight Center, Greenbelt, Md. and her colleagues at the 211th meeting of the American Astronomical Society in Austin, Texas.
Such "blue blobs"-weighing tens of thousands of solar masses-have never been seen in detail before in such sparse locations, say researchers. They are more massive than most open clusters found inside galaxies but a fraction of the mass of globular star clusters that orbit a galaxy.
Because the orphan stars don't belong to any particular galaxy, the heavier elements produced in their fusion furnaces may easily be expelled back into intergalactic space. This may offer clues as to how the early universe was "polluted" with heavier elements early in its history, say researchers.
The mystery is that the "blue blobs" are found along a wispy bridge of gas strung among three colliding galaxies, M81, M82, and NGC 3077, residing approximately 12 million light-years from Earth. This is not the place astronomers expect to find star clusters: in the "abyssal plain" of intergalactic space. "We could not believe it, the stars were in the middle of nowhere," says de Mello.
The "blue blobs" are clumped together in a structure called Arp's Loop, along the tenuous gas bridge. The gas filaments were considered too thin to accumulate enough material to actually build these many stars, says de Mello. But Hubble reveals the "blue blobs" contain the equivalent of five Orion Nebulae.
After finding that these "blobs" were resolved into stars, the team used the Hubble image to measure an age for the clusters of less than 200 million years with many stars as young and even younger than 10 million years. Not coincidentally, 200 million years is the estimated age of the galactic collision that created the tidal gas streamers, pulled between the galaxies like taffy.
De Mello and her team propose that the star clusters in this diffuse structure might have formed from gas collisions and subsequent turbulence, which enhanced locally the density of the gas streams. Galaxy collisions were much more frequent in the early universe, so "blue blobs" should have been common. After the stars burned out or exploded, the heavier elements forged in their nuclear furnaces would have been ejected to enrich intergalactic space.
Radio observations with the Very Large Array of radio telescopes in Socorro, New Mexico, gave a detailed map of the intergalactic bridge that revealed knots of denser gas. Studies with the 3.5-meter WIYN telescope on Kitt Peak in Arizona mapped the optical light glow of hydrogen along the bridge. Observations with NASA's Galaxy Evolution Explorer (GALEX) ultraviolet space telescope revealed an ultraviolet glow at the knots, and that earned them the nickname "blue blobs." But GALEX did not have the resolution to see individual stars or clusters. Only Hubble's Advanced Camera for Surveys at last revealed the point sources of the ultraviolet radiation.
Posted: January 9, 2008
Finding blue blobs in space sounds like an encounter with an alien out of a science fiction movie. But the Hubble Space Telescope's powerful vision has resolved strange objects nicknamed "blobs" and found them to be brilliant blue clusters of stars born in the swirls and eddies of a galactic smashup 200 million years ago.
 See larger image here |
Such "blue blobs"-weighing tens of thousands of solar masses-have never been seen in detail before in such sparse locations, say researchers. They are more massive than most open clusters found inside galaxies but a fraction of the mass of globular star clusters that orbit a galaxy.
Because the orphan stars don't belong to any particular galaxy, the heavier elements produced in their fusion furnaces may easily be expelled back into intergalactic space. This may offer clues as to how the early universe was "polluted" with heavier elements early in its history, say researchers.
The mystery is that the "blue blobs" are found along a wispy bridge of gas strung among three colliding galaxies, M81, M82, and NGC 3077, residing approximately 12 million light-years from Earth. This is not the place astronomers expect to find star clusters: in the "abyssal plain" of intergalactic space. "We could not believe it, the stars were in the middle of nowhere," says de Mello.
The "blue blobs" are clumped together in a structure called Arp's Loop, along the tenuous gas bridge. The gas filaments were considered too thin to accumulate enough material to actually build these many stars, says de Mello. But Hubble reveals the "blue blobs" contain the equivalent of five Orion Nebulae.
After finding that these "blobs" were resolved into stars, the team used the Hubble image to measure an age for the clusters of less than 200 million years with many stars as young and even younger than 10 million years. Not coincidentally, 200 million years is the estimated age of the galactic collision that created the tidal gas streamers, pulled between the galaxies like taffy.
De Mello and her team propose that the star clusters in this diffuse structure might have formed from gas collisions and subsequent turbulence, which enhanced locally the density of the gas streams. Galaxy collisions were much more frequent in the early universe, so "blue blobs" should have been common. After the stars burned out or exploded, the heavier elements forged in their nuclear furnaces would have been ejected to enrich intergalactic space.
Radio observations with the Very Large Array of radio telescopes in Socorro, New Mexico, gave a detailed map of the intergalactic bridge that revealed knots of denser gas. Studies with the 3.5-meter WIYN telescope on Kitt Peak in Arizona mapped the optical light glow of hydrogen along the bridge. Observations with NASA's Galaxy Evolution Explorer (GALEX) ultraviolet space telescope revealed an ultraviolet glow at the knots, and that earned them the nickname "blue blobs." But GALEX did not have the resolution to see individual stars or clusters. Only Hubble's Advanced Camera for Surveys at last revealed the point sources of the ultraviolet radiation.
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Lucimary Vargas de Oliveira Guardamino Espinoza
Além Paraíba-MG-Brasil
Presidente:
Observatório Astronômico Monoceros
Estacão Meteorológica Nº083/5ºDISME-INMET
CEPESLE -Centro de Estudos e Pesquisas Sertões do Leste
AHAP-Arquivo Histórico de Além Paraíba
http://www.monoceros.xpg.com.br
http://astronomicando.blogspot.com/
http://arqueoastronomy.blogspot.com/
http://www.arquivohistorico-mg.com.br
http://br.groups.yahoo.com/group/Observatorio_Monoceros/
MSN: observatoriomonoceros@hotmail.com
--------------------------------------------------------------------------
Lucimary Vargas de Oliveira Guardamino Espinoza
Além Paraíba-MG-Brasil
Presidente:
Observatório Astronômico Monoceros
Estacão Meteorológica Nº083/5ºDISME-INMET
CEPESLE -Centro de Estudos e Pesquisas Sertões do Leste
AHAP-Arquivo Histórico de Além Paraíba
http://www.monoceros.xpg.com.br
http://astronomicando.blogspot.com/
http://arqueoastronomy.blogspot.com/
http://www.arquivohistorico-mg.com.br
http://br.groups.yahoo.com/group/Observatorio_Monoceros/
MSN: observatoriomonoceros@hotmail.com
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Centaurus A exposed
Jet power and black hole assortment revealed in a new Chandra image.
Provided by Chandra X-Ray Center
 This image shows Centaurus A. NASA/CXC/CfA/R. Kraft et al./ESO/VLT/ISAAC/M. Rejkuba et al. [View Larger Image] A dramatic new Chandra image of the nearby galaxy Centaurus A provides one of the best views to date of the effects of an active supermassive black hole. Opposing jets of high-energy particles can be seen extending to the outer reaches of the galaxy, and numerous smaller black holes in binary star systems are also visible. The image was made from an ultra-deep look at the galaxy Centaurus A, equivalent to more than 7 days of continuous observations. Centaurus A is the nearest galaxy to Earth that contains a supermassive black hole actively powering a jet. A prominent X-ray jet extending for 13,000 light-years points to the upper left in the image, with a shorter "counterjet" aimed in the opposite direction. Astronomers think that such jets are important vehicles for transporting energy from the black hole to the much larger dimensions of a galaxy, and affecting the rate at which stars form there. |
 This image shows a composite of a radio and an optical image of Centaurus A. NASA/CXC/CfA/R. Kraft et al./ESO/VLT/ISAAC/M. Rejkuba et al. [View Larger Image] The inner part of the X-ray jet close to the black hole is dominated by these knots of X-ray emission, which probably come from shock waves, akin to sonic booms, caused by the jet. Farther from the black hole there is more diffuse X-ray emission in the jet. The cause of particle acceleration in this part of the jet is unknown. Hundreds of point-like sources are also seen in the Chandra image. Many of these are X-ray binaries that contain a stellar-mass black hole and a companion star in orbit around one another. Determining the population and properties of these black holes should help scientists better understand the evolution of massive stars and the formation of black holes. Another surprise was the detection of two particularly bright X-ray binaries. These sources may contain stellar mass black holes that are unusually massive, and this Chandra observation might have caught them gobbling up material at a high rate. High-energy electrons spiraling around magnetic field lines produce the X-ray emission from the jet and counterjet. This emission quickly saps the energy from the electrons, so they must be continually reaccelerated or the X-rays will fade out. Knot-like features in the jets detected in the Chandra image show where the acceleration of particles to high energies is currently occurring, and provides important clues to understanding the process that accelerates the electrons to near-light speeds. |
Weird object may be result of colliding protoplanets
UNIVERSITY OF ARIZONA NEWS RELEASE
Posted: January 10, 2008
Something bizarre orbiting a young, failed star 170 light-years from Earth may be the progeny of two protoplanets that collided and merged, astronomers announced at the American Astronomical Society meeting in Austin, Texas.
Given its hotter-than-expected temperature, dim luminosity, young age and location, the orbiting object, known as 2M1207B, should be a physical impossibility, scientists say.
"This is a strange enough object that it needs a strange explanation," Eric Mamajek of the Harvard-Smithsonian Center for Astrophysics said.
Mamajek and Michael Meyer of The University of Arizona propose that the object orbiting brown dwarf 2M1207A is small, about the size of Saturn. The "brown dwarf," or failed star, in the system is believed to be 25 times as massive as Jupiter and only about eight million years old.
The brown dwarf might be the outcome of a collision between a Saturn-sized gas giant and a planet about three times the size of Earth, Mamajek and Meyer suggest. The two smacked into each other and fused, forming one larger world still boiling from the heat generated in the titanic collision.
"Most, if not all, planets in our solar system were hit early in their history," Mamajek said. "A collision created Earth's moon and knocked Uranus on its side. It's quite likely that major collisions happen in other young planetary systems, too."
"The Earth was hit by something one-tenth its mass, and it's likely that other planets in our solar system were, too, including Venus and Uranus," Meyer said. "If that one-tenth scale holds in other planetary systems, then we could be seeing the aftermath of a collision between a 72 Earth-mass gas giant and an eight Earth-mass planet."
The collision theory is reasonable from a timescale point of view, Mamajek said. A 2400-degree Fahrenheit, Saturn-sized object would radiate its heat away over about 100,000 years. If the system were billions of years old, it is unlikely that astronomers would be looking at the right time, but because the system is only eight million years old, chances are much better that they would catch it shortly after the collision, when they could still see the hot aftermath.
The collision hypothesis makes several predictions that astronomers can test. Chief among them is a low surface gravity, which depends on a planet's mass and radius. To check this prediction, astronomers will need to get a better spectrum of 2M1207B. That's challenging because the object is very faint and very close to the brown dwarf 2M1207A.
Mamajek emphasized that while a planet collision may not be the correct explanation for the weirdness of 2M1207B, examples of colliding planets are likely to be found by the next generation of ground-based telescopes.
"Hot, post-collision planets might be a whole new class of objects we will see with the Giant Magellan Telescope."
Harvard and UA are members of an international consortium building the Giant Magellan Telescope, which is slated for completion in 2016 at a site in northern Chile. It will be composed of seven 8.4-meter primary mirrors arranged in a hexagonal pattern, giving it 4.5 times the collecting area of any current optical telescope. The UA Steward Observatory Mirror Lab cast the first GMT mirror in 2005.
"Even if we're wrong, I wouldn't be surprised if someone finds a clear-cut case in the next 10 years," Mamajek added.
Sloan Digital Sky Survey extended to 2014
New SDSS projects will explore dark energy, the Milky Way, and extrasolar planets.
By Francis Reddy
 A theoretical model of a galaxy like the Milky Way, showing trails of stars torn from disrupted satellite galaxies that have merged with the central galaxy. S. Sharma/J. Bullock/K. Johnston [View Larger Image] During the past 8 years, the Sloan Digital Sky Survey (SDSS) and its extension (SDSS-II) have made extraordinary discoveries ranging from asteroids to the distant cosmos. Researchers announced January 10 at the American Astronomical Society meeting in Austin, Texas, that the Alfred P. Sloan Foundation of New York has approved $7 million to support a new program, called SDSS-III. With additional funding expected from collaboration members and government agencies, SDSS-III will run from mid-2008 to 2014. Results from SDSS range from star streams in our galaxy's halo to the largest three-dimensional map of cosmic structure. "At this meeting alone, there are nearly 200 abstracts that mention Sloan or the SDSS," said Ohio State University's David Weinberg. |
 An SDSS map of the distribution of luminous galaxies, with a bullseye showing the characteristic scale imprinted by sound waves in the early universe. With three-dimensional maps of 1.5 million luminous galaxies and of absorbing gas towards 160,000 distant quasars, BOSS will measure this scale with high precision, yielding new insights into the nature of dark matter and the geometry of space. SDSS II [View Larger Image] SDSS-III comprises four coordinated projects. The largest of these, called the Baryon Oscillation Spectroscopic Survey (BOSS), will use a novel and powerful technique to study dark energy, one of contemporary science's biggest mysteries. "Whatever the answer turns out to be, it's going to rewrite fundamental physics," Weinberg says. |
| Acoustic oscillations A decade ago, astronomers made the startling discovery that the universe's expansion is speeding up. Cosmologists attribute this acceleration to so-called dark energy, which pervades otherwise empty space and exerts repulsive gravitational force. Dark energy could be the cosmological constant proposed by Albert Einstein in 1917. Or it could be a new, exotic form of energy whose properties evolve with time. In 2005, SDSS studies achieved one of the first clear detections of "baryon acoustic oscillations," a feature imprinted on the clustering of galaxies by sound waves that traveled through the early universe. "They imprinted a characteristic scale on the clustering of matter, which, in turn, imprinted a scale on the clustering of matter," Weinberg says. This find opens up a new way of measuring cosmic distances. "So, with a large enough galaxy map, the acoustic oscillations will allows us to determine the absolute distance scale of the universe with unprecedented accuracy and precision," Weinberg explains. Astronomers believe these measurements could reach 1-percent accuracy and extend to distances of 10 billion light-years. |
| Galactic structure SDSS-III also includes a 1-year extension of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). The project, which maps the outer Milky Way, was slated to end in June. The extension will be called SEGUE-2. |
 Artist's rendition of planets orbiting a sun-like star. T. Riecken [View Larger Image] A new project, called the Apache Point Observatory Galactic Evolution Experiment (APOGEE), will peer through dust-obscured regions near the galactic center. Although dust blocks light, infrared radiation can penetrate it. APOGEE will employ a unique instrument that simultaneously observes infrared emissions from 300 stars to survey 100,000 stars located in the inner galaxy. The goal is to determine the chemical signatures of these stars. "It's the ultimate exercise in forensic archeology," says the University of Virginia's Steven Majewski, because today's stars contain elements forged and released by a previous stellar generation. |
| Finding exoplanets Astronomers have identified more than 250 extrasolar planets, but most are Jupiter-like gas giants that follow non-circular orbits and lie close to their parent stars. The SDSS-III MARVELS project will search for giant planets orbiting some 10,000 stars — more than 3 times the number searched by all other telescopes to date. "By systematically monitoring such a large number of stars, MARVELS will address two of the biggest questions in planetary science: How do giant planets form, and why are so many in such unusual orbits?" explains lead researcher Jian Ge of the University of Florida. Princeton University's James Gunn has led the Sloan Digital Sky Survey through nearly 2 decades of construction and operation. "It's amazing to see that the SDSS can transform scientific fields we hadn't even conceived of 20 years ago," he says. |
Even thin galaxies can grow fat black holes
NASA/JPL NEWS RELEASE
Posted: January 14, 2008
NASA's Spitzer Space Telescope has detected plump black holes where least expected -- skinny galaxies.
Like people, galaxies come in different shapes and sizes. There are thin spirals both with and without central bulges of stars, and more rotund ellipticals that are themselves like giant bulges. Scientists have long held that all galaxies except the slender, bulgeless spirals harbor supermassive black holes at their cores. Furthermore, bulges were thought to be required for black holes to grow.
Posted: January 14, 2008
NASA's Spitzer Space Telescope has detected plump black holes where least expected -- skinny galaxies.
Like people, galaxies come in different shapes and sizes. There are thin spirals both with and without central bulges of stars, and more rotund ellipticals that are themselves like giant bulges. Scientists have long held that all galaxies except the slender, bulgeless spirals harbor supermassive black holes at their cores. Furthermore, bulges were thought to be required for black holes to grow.
 This artist's concept illustrates the two types of spiral galaxies that populate our universe: those with plump middles, or central bulges (upper left), and those lacking the bulge (foreground). Credit: NASA/JPL-Caltech |
The new Spitzer observations throw this theory into question. The infrared telescope surveyed 32 flat and bulgeless galaxies and detected monstrous black holes lurking in the bellies of seven of them. The results imply that galaxy bulges are not necessary for black hole growth; instead, a mysterious invisible substance in galaxies called dark matter could play a role.
"This finding challenges the current paradigm. The fact that galaxies without bulges have black holes means that the bulges cannot be the determining factor, " said Shobita Satyapal of the George Mason University, Fairfax, Va. "It's possible that the dark matter that fills the halos around galaxies plays an important role in the early development of supermassive black holes."
Satyapal presented the findings at the 211th meeting of the American Astronomical Society in Austin, Texas. A study from Satyapal and her team will be published in the April 10 issue of the Astrophysical Journal.
Our own Milky Way is an example of a spiral galaxy with a bulge; from the side, it would look like a plane seen head-on, with its wings out to the side. Its black hole, though dormant and not actively "feeding," is several million times the mass of our sun.
Previous observations had suggested that bulges and black holes flourished together like symbiotic species. For instance, supermassive black holes are almost always about 0.2 percent the mass of their galaxies' bulges. In other words, the more massive the bulge, the more massive the black hole. Said Satyapal, "Scientists reasoned that somehow the formation and growth of galaxy bulges and their central black holes are intimately connected."
But a wrinkle appeared in this theory in 2003, when astronomers at the University of California, Berkeley, and Observatories of the Carnegie Institution of Washington, Pasadena, Calif., discovered a relatively "lightweight" supermassive black hole in a galaxy lacking a bulge. Then, earlier this year, Satyapal and her team uncovered a second supermassive black hole in a similarly svelte galaxy.
In the latest study, Satyapal and her colleagues report the discovery of six more hefty black holes in thin galaxies with minimal bulges, further weakening the "bulge-black hole" theory. Why hadn't anybody seen these black holes before? According to the scientists, bulgeless galaxies tend to be very dusty, letting little visible light escape. But infrared light can penetrate dust, so the team was able to use Spitzer's infrared spectrograph to reveal the "fingerprints" of active black holes lurking in galaxies millions of light years away.
"A feeding black hole spits out high-energy light that ionizes much of the gas in the core of the galaxy," said Satyapal. "In this case, Spitzer identified the unique fingerprint of highly ionized neon -- only a feeding black hole has the energy needed to excite neon to this state." The precise masses of the newfound black holes are unknown.
If bulges aren't necessary ingredients for baking up supermassive black holes, then perhaps dark matter is. Dark matter is the enigmatic substance that permeates galaxies and their surrounding halos, accounting for up to 90 percent of a galaxy's mass. So-called normal matter makes up stars, planets, living creatures and everything we see around us, whereas dark matter can't be seen. Only its gravitational effects can be felt. According to Satyapal, dark matter might somehow determine the mass of a black hole early on in the development of a galaxy.
"Maybe the bulge was just serving as a proxy for the dark matter mass -- the real determining factor behind the existence and mass of a black hole in a galaxy's center," said Satyapal.
Other authors of this study include: D. Vega of the George Mason University; R.P. Dudik of the George Mason University and NASA Goddard Space Flight Center, Greenbelt, Md.; N.P. Abel of the University of Cincinnati, Ohio; and Tim Heckman of the Johns Hopkins University, Baltimore, Md.
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, also in Pasadena. Caltech manages JPL for NASA. Spitzer's infrared spectrograph was built by Cornell University, Ithaca, N.Y. Its development was led by Jim Houck of Cornell.
"This finding challenges the current paradigm. The fact that galaxies without bulges have black holes means that the bulges cannot be the determining factor, " said Shobita Satyapal of the George Mason University, Fairfax, Va. "It's possible that the dark matter that fills the halos around galaxies plays an important role in the early development of supermassive black holes."
Satyapal presented the findings at the 211th meeting of the American Astronomical Society in Austin, Texas. A study from Satyapal and her team will be published in the April 10 issue of the Astrophysical Journal.
Our own Milky Way is an example of a spiral galaxy with a bulge; from the side, it would look like a plane seen head-on, with its wings out to the side. Its black hole, though dormant and not actively "feeding," is several million times the mass of our sun.
Previous observations had suggested that bulges and black holes flourished together like symbiotic species. For instance, supermassive black holes are almost always about 0.2 percent the mass of their galaxies' bulges. In other words, the more massive the bulge, the more massive the black hole. Said Satyapal, "Scientists reasoned that somehow the formation and growth of galaxy bulges and their central black holes are intimately connected."
But a wrinkle appeared in this theory in 2003, when astronomers at the University of California, Berkeley, and Observatories of the Carnegie Institution of Washington, Pasadena, Calif., discovered a relatively "lightweight" supermassive black hole in a galaxy lacking a bulge. Then, earlier this year, Satyapal and her team uncovered a second supermassive black hole in a similarly svelte galaxy.
In the latest study, Satyapal and her colleagues report the discovery of six more hefty black holes in thin galaxies with minimal bulges, further weakening the "bulge-black hole" theory. Why hadn't anybody seen these black holes before? According to the scientists, bulgeless galaxies tend to be very dusty, letting little visible light escape. But infrared light can penetrate dust, so the team was able to use Spitzer's infrared spectrograph to reveal the "fingerprints" of active black holes lurking in galaxies millions of light years away.
"A feeding black hole spits out high-energy light that ionizes much of the gas in the core of the galaxy," said Satyapal. "In this case, Spitzer identified the unique fingerprint of highly ionized neon -- only a feeding black hole has the energy needed to excite neon to this state." The precise masses of the newfound black holes are unknown.
If bulges aren't necessary ingredients for baking up supermassive black holes, then perhaps dark matter is. Dark matter is the enigmatic substance that permeates galaxies and their surrounding halos, accounting for up to 90 percent of a galaxy's mass. So-called normal matter makes up stars, planets, living creatures and everything we see around us, whereas dark matter can't be seen. Only its gravitational effects can be felt. According to Satyapal, dark matter might somehow determine the mass of a black hole early on in the development of a galaxy.
"Maybe the bulge was just serving as a proxy for the dark matter mass -- the real determining factor behind the existence and mass of a black hole in a galaxy's center," said Satyapal.
Other authors of this study include: D. Vega of the George Mason University; R.P. Dudik of the George Mason University and NASA Goddard Space Flight Center, Greenbelt, Md.; N.P. Abel of the University of Cincinnati, Ohio; and Tim Heckman of the Johns Hopkins University, Baltimore, Md.
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, also in Pasadena. Caltech manages JPL for NASA. Spitzer's infrared spectrograph was built by Cornell University, Ithaca, N.Y. Its development was led by Jim Houck of Cornell.
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