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Gamma view of a big blast

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1:20pm, December 5, 2004
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Astronomers have for the first time used extremely high-energy gamma rays to image a celestial body.

Paula Chadwick of the University of Durham in England and her colleagues recorded flashes of blue light known as Cerenkov radiation, which is produced when Earth's atmosphere stops incoming gamma rays.

The team aimed the High Energy Stereoscopic System, an array of four telescopes in Namibia, at a supernova remnant in the Southern Hemisphere. The remnant is an expanding shell of debris left behind by a stellar explosion that sky watchers would have witnessed about 1,000 years ago.

The production of gamma rays suggests that the supernova's blast wave acts as a cosmic version of a particle accelerator, revving up charged particles to energies a billion times those of a hospital X ray. The gamma-ray emissions are also some of the first proof that this and other supernova remnants are likely sources of the cosmic rays that continually bombard Earth, the team asserts in the Nov. 4 Nature.

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