gamma-ray bursts

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gamma-ray bursts

Intense flashes of hard X-rays or gamma rays, detected at energies up to one million electronvolts. They are of short duration (0.1–1000 seconds) and were discovered by US Air Force satellites in 1967 but not declassified until 1973. There are sharp temporal features in the burst time profile; this allows the measurement of differences in arrival times of wavefronts of the order of a few milliseconds over baselines separated by hundreds of light-seconds. For the strongest and most rapidly varying bursts, such measurements yield angular resolutions of the order of arc seconds. The most intense burst observed so far lies within the supernova remnant N49 in the Large Magellanic Cloud. The BATSE experiment on the Compton Gamma Ray Observatory has detected hundreds of γ-ray bursts, averaging about one per day. Measurements have revealed that the distribution of the bursts is consistent with isotropy: they are uniformly distributed across the sky. Their origin still remains a mystery. γ-ray emission lines in their spectra may be related to annihilation radiation redshifted by the strong gravitational field of a neutron star, and γ-ray absorption features to cyclotron absorption in intense magnetic fields. The rapid temporal structure, including the periodic emission, is generally assumed to point to neutron star origins for γ-ray bursts, although sources at cosmological distances cannot be ruled out. The most probable energy source is thought to be either gravitational or nuclear in origin.

gamma-ray bursts

[′gam·ə ‚rā ‚bərsts]
(astronomy)
Intense blasts of soft gamma rays of unknown origin, which range in duration from a tenth of a second to tens of seconds and occur several times a year from sources widely distributed over the sky.
References in periodicals archive ?
Astronomers say it is incredibly unlikely that a gamma ray burst -- especially a big one like this -- could go off in our galaxy, near us
Gamma ray bursts are mysterious flashes of intense high-energy radiation that appear from random directions in space.
THE mystery of the forces behind the most powerful explosions in the Universe - Gamma Ray Bursts - has been solved by Liverpool scientists.
The angle of the shadow points back to the gamma ray burst.
Unlike cosmic gamma ray bursts, which typically last a few seconds, TFGs last only about one to two milliseconds.
There is new and compelling evidence that cosmic gamma ray bursts originate from within the Milky Way and not from the edge of the universe, as many astronomers had believed, according to University of Chicago astrophysicists Jean Quashnock and Don Lamb.
The instruments will study cosmic phenomena such as gamma ray bursts, neutron stars, supernova remnants and distant galaxies fueled by super massive black holes at their centers.
The Swift space observatory, launched in 2004, has been scanning for gamma ray bursts, the most energetic objects in the sky.
Bromm and Loeb calculate that the first 15 percent of stars that formed in the cosmos could be responsible for a significant fraction of all gamma ray bursts that may be observed from Earth.
The intense conditions needed to generate such energetic particles have focused physicists' interest on two potential sources: the massive black holes at the centers of active galaxies, and the exploding fireballs observed by astronomers as gamma ray bursts (GRBs).
Gamma ray bursts can emit more than a hundred billion times the amount of energy the sun produces in a year in a few seconds.
studied mysterious, fleeting blasts of energy from space known as gamma ray bursts.