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US: Astronomers see “shockingly bright” gamma-ray burst

4th May 2013

WASHINGTON, (Xinhua): Astronomers have witnessed a record-setting blast of gamma rays from a dying star in a distant galaxy that produced the highest-energy light ever detected from such an event.

The eruption, which is classified as a gamma-ray burst(GRB), and designated GRB 130427A, occurred just after 3:47 a.m. EDT ( 0747GMT) on April 27, U.S. space agency NASA said in a statement on Friday.

NASA’s Fermi Gamma-ray Space Telescope recorded one gamma ray with an energy of at least 94 billion electron volts (GeV), or some 35 billion times the energy of visible light, and about three times greater than the telescope’s previous record.

The GeV emission from the burst lasted for hours, and it remained detectable by the telescope for the better part of a day, setting a new record for the longest gamma-ray emission from a GRB.

The burst subsequently was detected in optical, infrared and radio wavelengths by ground-based observatories. Astronomers quickly learned that the GRB was located about 3.6 billion light- years away, which for these events is relatively close.

“We have waited a long time for a gamma-ray burst this shockingly, eye-wateringly bright,” said Julie McEnery, project scientist for the Fermi Gamma-ray Space Telescope at NASA’s Goddard Space Flight Center. “The GRB lasted so long that a record number of telescopes on the ground were able to catch it while space-based observations were still ongoing.”

Gamma-ray bursts are the universe’s most luminous explosions. Astronomers think most occur when massive stars run out of nuclear fuel and collapse under their own weight. As the core collapses into a black hole, jets of material shoot outward at nearly the speed of light.

The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade with time.

If the GRB is near enough, astronomers usually discover a supernova at the site a week or so after the outburst. Ground- based observatories are monitoring the location of GRB 130427A and expect to find an underlying supernova by midmonth.

Editor: yan

http://news.xinhuanet.com/english/sci/2013-05/04/c_132358214.htm

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