Black hole devours 300million suns in the biggest of bangs
08jan05 - The Australian

US scientists have detected the largest explosion ever in the universe, which saw a mass equivalent to about 300million suns sucked into a black hole.

"The eruption, which has lasted for more than 100million years, has generated energy equivalent to hundreds of millions of gamma-ray bursts," NASA, the US space agency, said yesterday. The discovery was made by NASA's orbiting Chandra X-ray Observatory which is controlled from a base in Cambridge, Massachusetts. The huge eruption was seen in a Chandra image of the hot, X-ray-emitting gas of a galaxy cluster called MS 0735.6+7421, the agency said. The galaxy is about 2.6billion light years away.

Scientists believe that this black hole is a relatively recent phenomenon. This event was caused by gravitational energy release, as enormous amounts of matter fell towards a black hole. Most of the matter was swallowed, but some of it was violently ejected before being captured by the black hole. "I was stunned to find that a mass of about 300million suns was swallowed," said Brian McNamara of Ohio University, lead author of a study on the discovery published in the latest issue of Nature. The energy released shows the black hole in MS 0735 has grown dramatically during this eruption. Previous studies suggest other large black holes have grown very little in the recent past, and that only smaller black holes are still growing quickly.

"This new result is as surprising as it is exciting," said co-author Paul Nulsen, of the Harvard-Smithsonian Centre for Astrophysics in Cambridge. "This black hole is feasting, when it should be fasting."
Gas is being pushed away from the black hole at supersonic speeds over a distance of about 1million light years, said the scientists. The mass of the displaced gas equals about a trillion suns, more than the mass of all the stars in the Milky Way.
"Until now we had no idea this black hole was gorging itself," said Michael Wise, of the Massachusetts Institute of Technology in Cambridge. "The discovery of this eruption shows X-ray telescopes are necessary to understand some of the most violent events in the universe."
AFP
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- posted by Andy @ 4:40 PM

 
NASA Swift Mission Turns On And Sees A Blast Of Bursts
Jan 7 2005 - NASA/Godard Space Center

The NASA-led Swift mission opened its doors to a flurry of gamma ray burst action. Scientists were still calibrating the main instrument, the Burst Alert Telescope (BAT), when the first burst appeared on December 17. Three bursts on December 19, and one on December 20, followed.

Swift's primary goal is to unravel the mystery of gamma ray bursts. The bursts are random and fleeting explosions, second only to the Big Bang in total energy output. Gamma rays are a type of light millions of times more energetic than light human eyes can detect. Gamma ray bursts last only from a few milliseconds to about one minute. Each burst likely signals the birth of a black hole.

"The optimists among us were hoping to detect two bursts a week, not three in one day just after turning the telescope on," said Dr. Scott Barthelmy, the BAT lead scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "Maybe we got lucky, or maybe we've underestimated the true rate of these bursts. Only time will tell," he added.

Once the BAT, that covers about one-seventh of the sky at any time, detects a gamma ray burst, it quickly relays a location to the ground. Within about one minute, the satellite automatically turns toward the burst. The move brings the burst within view of Swift's two other telescopes: the X-ray Telescope (XRT) and the Ultraviolet/Optical Telescope (UVOT).

Once all three instruments are turned on and calibrated, Swift will get down to the business of analyzing gamma ray bursts. "The universe kept up its side of the bargain, and we kept up ours," said Dr. Neil Gehrels, Swift's Principal Investigator at Goddard. "This is going to be an exciting mission," he said.

The Swift team tested the BAT by observing Cygnus X-1, a well-known bright source that produces gamma rays in our galaxy. It is thought to be a black hole in orbit around a star. The team called this BAT's "first light."

The BAT is the most sensitive gamma ray detector ever flown. The BAT employs a novel technology to image and locate gamma ray bursts. Unlike visible light, gamma rays pass right through telescope mirrors and cannot be reflected onto a detector. The BAT uses a technique called "coded aperture mask" to create a gamma ray shadow on its detectors. The mask contains 52,000 randomly placed lead tiles that block some gamma rays from reaching the detectors. With each burst, some detectors light up while others remain dark, shaded by the lead tiles. The angle of the shadow points back to the gamma ray burst.

"The BAT coded aperture mask is about the size of a pool table, the largest and most intricate ever fabricated," said Ed Fenimore of Los Alamos National Laboratory, N.M. Los Alamos created the BAT software. "BAT can accurately pinpoint a burst within seconds and detect bursts five times fainter than previous instruments," he added.

Swift, a medium-class explorer mission managed by Goddard, was launched from Cape Canaveral on November 20, 2004. The mission is in participation with the Italian Space Agency and the Particle Physics and Astronomy Research Council in the United Kingdom.

Swift was built at Goddard in collaboration with General Dynamics, Ariz.; Penn State University, College Station, Pa.; Sonoma State University, Rohnert Park, Calif.; Los Alamos; Mullard Space Science Laboratory, Surrey, England; the University of Leicester, England; the Brera Observatory, Milan, Italy; and ASI Science Data Center, Rome.
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- posted by Andy @ 1:47 AM