In 2010, astronomers discovered four stars, all of which are at least 300 times the mass of the Sun. Prior to their detection, stars with this solar mass were thought to be impossible to exist; not one star that has been accounted for and studied has a mass that exceeds the 150 solar mass limit, which is a universal limit. These four colossal stellar bodies have been the only ones detected in the Universe. Their origin stumped astronomers.

Recently, however, one team of astronomers – Samabaran Banerjee, Raval Kroupa, Seungkyung Oh – from the University of Bonn in Germany determined the cause of the “monster” stars’ existence by creating and using a computer model: Because the stars in the tiny R136 cluster are so close to one another, the binary systems are unusually tight; hence, the intense gravitational tug the stars impose on each in each system caused the stars to smash together and fuse to become their present hyper-massive and luminous selves.

“They start appearing very early in the life of the cluster,” Dr. Banerjee states in Royal Astronomical Society press release. “With so many massive stars in tight binary pairs, themselves packed closely together, there are frequent random encounters, some of which result in collisions where two stars coalesce into heavier objects. The resulting stars can then quite easily end up being as ultramassive as those seen in R136.”

These four stars are located in the Large Magellanic Cloud (LMC), which is one of the closest galaxies to the Milky Way and a hotbed for star formation, harboring approximately ten billion stars. Specifically, their home lies in the R136 star cluster, which is a mere 35 light-years across, in the well-known Tarantula Nebula, the LMC’s most active star formation region.

A star cluster is a group of stars tightly held together by gravity. The number of stars range from a few hundred to several hundreds of thousands. Roughly, there are more than 1000 star clusters in the LMC alone.

For accuracy, the model Banerjee, Kroupa, and Oh produced resembled the R136 region. To calculate the shape of the star cluster, the team utilized the NBODY6 – or “N-body” – integration code developed by Sverre Aaseth, a research scientist of the Institute of Astronomy at the University of Cambridge. The model contained 170,000, which were normal in mass and luminosity (that is, they were stars from the Main Sequence of the Hertzsprung-Russell diagram) and were distributed as the stars were in R136.

For Banerjee, Kroupa and Oh to monitor and analyze how the stars interacted with one another and changed over time, the computer had to solve 510,000 calculations multiple times while taking into account stellar winds, nuclear reactions caused by stellar collisions, gravity, and the result of each collision – all of which happened in the supposed densely packed environment. The N-body code the team used helped speed up these calculations.

Once the calculations were completed, the team concluded that the leviathan stars inhabiting R136 used to be ordinary stars that merged with one another, and that they are not anomalies which had formed outside our knowing of how star’s normally form.

“Not only the upper mass limit but the whole mass ingredient of any newborn assembly of stars appears identical irrespective of the stellar birthplace: the star birth process seems to [still] be universal,” Dr. Kroupa says. “This helps us relax because the collisions mean that the ultramassive stars are a lot easier to explain. The universality of star formation prevails after all.”

The team published their paper in Monthly Notices of the Royal Astronomical Society.

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Washington, US – The Herschel Space Observatory has shown galaxies with the most powerful, active black holes at their cores produce fewer stars than galaxies with less active black holes. The results are the first to demonstrate black holes suppressed galactic star formation when the universe was less than half its current age. Herschel is a European Space Agency-led mission with important NASA contributions.

“We want to know how star formation and black hole activity are linked,” said Mathew Page of University College London’s Mullard Space Science Laboratory in the United Kingdom and lead author of the Nature paper describing these findings. “The two processes increase together up to a point, but the most energetic black holes appear to turn off star formation.”

Super massive black holes, weighing as much as millions of suns, are believed to reside in the hearts of all large galaxies. When gas falls upon these monsters, the material is accelerated and heated around the black hole, releasing great torrents of energy. Earlier in the history of the universe, these giant, luminous black holes, called active galactic nuclei, were often much brighter and more energetic. Star formation was also livelier back then.

Studies of nearby galaxies suggest active black holes can squash star formation. The revved-up, central black holes likely heat up and disperse the galactic reservoirs of cold gas needed to create new stars. These studies have only provided “snapshots” in time, however, leaving the overall relationship of active galactic nuclei and star formation unclear, especially over the cosmic history of galaxy formation.

“To understand how active galactic nuclei affect star formation over the history of the universe, we investigated a time when star formation was most vigorous, between eight and 12 billion years ago,” said co-author James Bock, a senior research scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena and co-coordinator of the Herschel Multi-tiered Extragalactic Survey. “At that epoch, galaxies were forming stars 10 times more rapidly than they are today on average. Many of these galaxies are incredibly luminous, more than 1,000 times brighter than our Milky Way.”

For the new study, Page and colleagues used Herschel data that probed 65 galaxies at wavelengths equivalent to the thickness of several sheets of office paper, a region of the light spectrum known as the far-infrared. These wavelengths reveal the rate of star formation, because most of the energy released by developing stars heats surrounding dust, which then re-radiates starlight out in far-infrared wavelengths.

The researchers compared their infrared readings with X-rays streaming from the active central black holes in the survey’s galaxies, measured by NASA’s Chandra X-ray Observatory. At lower intensities, the black holes’ brightness and star formation increased in sync. However, star formation dropped off in galaxies with the most energetic central black holes. Astronomers think inflows of gas fuel new stars and super massive black holes. Feed a black hole too much, however, and it starts spewing radiation into the galaxy that prevents raw material from coalescing into new stars.

“Now that we see the relationship between active super massive black holes and star formation, we want to know more about how this process works,” said Bill Danchi, Herschel program scientist at NASA Headquarters in Washington. “Does star formation get disrupted from the beginning with the formation of the brightest galaxies of this type, or do all active black holes eventually shut off star formation, and energetic ones do this more quickly than less active ones?”

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In 2009, NASA launched Kepler to search for planets outside the solar system – called extrasolar planets, or exoplanets – that are Earth-sized and have a chance of harboring life. As of December 2011, the spacecraft has discovered 2,326 exoplanets, over a hundred of which are likely candidates to meet the requirements.

A team of astronomers at NASA decided in early January to give Kepler an additional mission of hunting for extrasolar moons, or exomoons. The team believes in the potential existence of exomoons. Natural satellites only survive half the time when they and their companion planets are still undergoing evolution, though the many moons in our solar system increase the possibility.

With this new mission, titled Hunt of Exomoons with Kepler (HEK), Kepler may find life on these moons as well as on exoplanets and help astronomers understand planetary evolution and the formation of natural satellites. Kepler will first look at the exoplanets cataloged thus far to see if any of them have any such natural satellites. The exomoons would have to be similar in size, or larger, than our Moon because they would be easiest for the spacecraft to detect.

It is also possible that exomoons are capable of harboring life. In our solar system, Jupiter’s Europa and Saturn’s Enceladus have liquid water beneath their surfaces. It is not known for sure if these two large moons contain life, though the presence of water heightens the probability as well as the probability that exomoons may be habitable.

Kepler will attempt to search for exomoons through two means: dynamical effects and eclipses features. With dynamical effects, the spacecraft would observe and measure the gravitational effect between the exoplanet and the exomoon (i.e. how much they tug on each other).

The amount of gravitational effects on the two bodies would determine whether or not the system would be a planet-moon system or a binary-planet system (it would be easy for the former to be mistaken with the latter). With eclipse features, Kepler would be on the lookout for solar and lunar eclipses, involving the exomoon, its companion planet, and their star. Kepler would see if the exomoon may make subtle changes in a star’s brightness through eclipsing the star, which would drop a bit in brightness.

Once Kepler finds an exomoon, it would be able to determine its size and mass based on the gravitational effect and eclipse features. Upon discovering the size and mass, it would then calculate the density. Thereafter, the exomoon’s composition can be determined, giving insight as to how to the exomoon formed and, ultimately, revealing the process of planetary evolution.

“Extrasolar moons represent an outstanding challenge in modern observational astronomy,” writes head author David Kipping in the team’s paper. Kipping,  a member of the team at NASA, is an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

“Their detection and study would yield a revolution in the understanding of planet/moon formation and evolution, but perhaps most provocatively, they could be frequent seats for life in the Galaxy.”

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After more than three years in space, NASA’s Fermi Gamma-ray Space Telescope is extending its view of the high-energy sky into a largely unexplored electromagnetic range. On January 10, the Fermi team announced its first census of energy sources in this new realm.

Fermi’s Large Area Telescope scans the entire sky every three hours, continually deepening its portrait of the sky in gamma rays, the most energetic form of light. While the energy of visible light falls between about 2 and 3 electron volts, the LAT detects gamma rays with energies ranging from 20 million to more than 300 billion electron volts.

At higher energies, gamma rays are rare. Above 10 GeV, even Fermi’s LAT detects only one gamma ray every four months.

“Before Fermi, we knew of only four discrete sources above 10 GeV, all of them pulsars,” said David Thompson, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “With the LAT, we’ve found hundreds, and we’re showing for the first time just how diverse the sky is at these high energies.”

Any object producing gamma rays at these energies is undergoing extraordinary astrophysical processes. More than half of the 496 sources in the new census are active galaxies, where matter falling into a supermassive black hole powers jets that spray out particles at nearly the speed of light.

Only about 10 percent of the known sources lie within our own galaxy. They include rapidly rotating neutron stars called pulsars, the expanding debris from supernova explosions, and in a few cases, binary systems containing massive stars.

More than a third of the sources are completely unknown, having no identified counterpart detected in other parts of the spectrum. With the new catalog, astronomers will be able to compare the behavior of different sources across a wider span of gamma-ray energies for the first time.

Just as bright infrared sources may fade to invisibility in the ultraviolet, some of the gamma-ray sources above 1 GeV vanish completely when viewed at higher, or “harder,” energies.

One example is the well-known radio galaxy NGC 1275, which is a bright, isolated source below 10 GeV. At higher energies, it fades appreciably and another nearby source begins to appear. Above 100 GeV, NGC 1275 becomes undetectable by Fermi, while the new source, the radio galaxy IC 310, shines brightly.

The Fermi hard-source list is the product of an international team led by Pascal Fortin at the Ecole Polytechnique’s Laboratoire Leprince-Ringuet in Palaiseau, France, and David Paneque at the Max Planck Institute for Physics in Munich.

The catalog serves as an important roadmap for ground-based facilities called Atmospheric Cherenkov Telescopes, which have amassed about 130 gamma-ray sources with energies above 100 GeV. They include the Major Atmospheric Gamma Imaging Cherenkov telescope on La Palma in the Canary Islands, the Very Energetic Radiation Imaging Telescope Array System in Arizona, and the High Energy Stereoscopic System in Namibia.

“Our catalog will have a significant impact on ground-based facilities’ work by pointing them to the most likely places to find gamma-ray sources emitting above 100 GeV,” Paneque said.

Compared to Fermi’s LAT, these ground-based observatories have much smaller fields of view. They also make fewer observations because they cannot operate during the daytime, bad weather, or a full moon.

“As Fermi’s exposure constantly improves our view of hard sources, ground-based telescopes are becoming more sensitive to lower-energy gamma rays, allowing us to bridge these two energy regimes,” Fortin added.

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. Fermi is managed by Goddard. It was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the United States.

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Brad Pitt has been voted the Top Money-Making Star of 2011 in Quigley Publishing Company’s 80th Annual Poll of Motion Picture Exhibitors. This is Pitt’s sixth appearance in the Poll, but his first win. Exhibitors felt Pitt was responsible for more traffic to theatres than any other Hollywood star based on his performances this year in “Moneyball,” “The Tree of Life,” and “Happy Feet Two.”

The Quigley Poll, conducted each year since 1932, is an annual survey of motion picture theatre owners and film buyers, which asks them to vote for the ten stars that they believe generated the most box-office revenue for their theatres during the year. It has been long regarded as one of the most reliable indicators of a star’s real box office draw because the selections are made by professionals whose livelihood depends on choosing the films and actors that will bring audiences to their theatres. The Quigley Poll lists the results of all the Polls since Marie Dressler, Janet Gaynor, and Joan Crawford took the top three places in 1932.

George Clooney placed second this year based on “The Ides of March,” where he was also the director, producer, and co-writer, and “The Descendants.” Johnny Depp, last year’s winner, made it to number three this year with 2011 roles in “Pirates of the Caribbean: On Stranger Tides” and “The Rum Diary.”  Depp has placed in the poll seven times, as has this year’s number four, Leonardo DiCaprio, who starred in “J. Edgar.” Matt Damon, number five, had a very busy year with “Contagion,” “The Adjustment Bureau,” “Margaret,” and “We Bought a Zoo.”

Sandra Bullock, winner of 2009, placed number six, which marks her fifth appearance in the poll. She first placed in the survey in 1995. There were two first-timers this year, Bradley Cooper number seven and Ben Stiller number ten. Bradley Cooper was in “The Hangover Part II,” and Ben Stiller was in “Tower Heist.” Robert Downey, Jr. was number eight on the strength of “Sherlock Holmes: A Game of Shadows,” and Meryl Streep was number nine as ‘The Iron Lady” and is in the Top Ten for the fourth time.

Tom Cruise has not placed in the Poll since 2006, but he has been in the Top Ten 20 times since 1983 and has been voted number one the most of any actor – seven times. Tom Hanks, Clint Eastwood, Burt Reynolds, and Bing Crosby have all won five times. Clint Eastwood has been in the poll 21 times starting in 1968. Currently, exhibitors appreciate him more as a director that brings audiences to their theatres. John Wayne, Doris Day, and Shirley Temple each finished first four times, but John Wayne was voted one of the Top Ten Money-Making Stars an astounding 25 times from 1949 to 1974.

Exhibitors were also asked to name the Stars of Tomorrow for 2011, one actor and one actress who they feel will be Top Money-Makers in the years to come. The 2011 winners are Rooney Mara, who played Lisbeth Salander in “The Girl with the Dragon Tattoo,” and Jonah Hill, who had a breakthrough performance in “Moneyball” and starred in “The Sitter.”

Top Ten Money-Making Stars of 2011

1. Brad Pitt
2. George Clooney
3. Johnny Depp
4. Leonardo Di Caprio
5. Matt Damon
6. Sandra Bullock
7. Bradley Cooper
8. Robert Downey, Jr.
9. Meryl Streep
10. Ben Stiller

Stars of Tomorrow:

Rooney Mara
Jonah Hill

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