Gamma-ray burst: the mystery deepens.Some call it the greatest fireworks fireworks: see pyrotechnics. fireworks Explosives or combustibles used for display. Of ancient Chinese origin, fireworks evidently developed out of military rockets and explosive missiles and accompanied the spread of military explosives westward to show never seen. Nearly once a day, a burst of gamma rays Gamma rays Electromagnetic radiation emitted from excited atomic nuclei as an integral part of the process whereby the nucleus rearranges itself into a state of lower excitation (that is, energy content). explodes somewhere in the universe, emitting high-energy photons and then disappearing - usually within seconds. The short duration of the bursts has made studying this phenomenon extremely difficult. Last February, however, NASA's Compton Gamma Ray Observatory Compton Gamma Ray Observatory Space observatory in service from 1991 to 2000 that was designed to identify the sources of celestial gamma rays. It was named after physicist Arthur Holly Compton. (GRO GRO Guerrero (Estado de México) GRO General Register Office (UK) GRO Greater Research Opportunities GRO Gamma Ray Observatory GRO Growth-Related Oncogene GRO Greensboro, North Carolina ) spotted a gamma-ray burst gamma-ray burst n. A short-lived, localized, and intense burst of gamma radiation that originates outside the solar system from an unknown source. that appeared to last 90 minutes. Because Earth slid in front of the orbiting GRO's view, the craft detected only the opening and the finale of the light show, leading astronomers to infer that the burst lasted a full hour and a half. What's more, the burst contained delayed gamma rays with many times the energy of those previously detected. "Although some scientists had theorized about the presence of [such] delayed high-energy gamma rays, this was the first time we actually observed them," says Kevin Hurley, an astrophysicist at the University of California, Berkeley The University of California, Berkeley is a public research university located in Berkeley, California, United States. Commonly referred to as UC Berkeley, Berkeley and Cal . Hurley and his colleagues report their findings in the Dec. 15 NATURE. These observations add to the continuing mystery about the sources of gamma-ray bursts (SN: 2/5/94, p.85). A number of scientists have suggested that the bursts originate from colliding comets within the Milky Way Milky Way, the galaxy of which the sun and solar system are a part, seen as a broad band of light arching across the night sky from horizon to horizon; if not blocked by the horizon, it would be seen as a circle around the entire sky. ; others Burst seen by GRO instruments on Feb. 17. Green line indicates position plotted by the Burst and Transient Source Experiment (in conjunction with readings from the Ulysses spacecraft). The Energetic Gamma-Ray Experiment Telescope localized the burst to the area inside the jagged contour line. The Compton Telescope revealed that the burst lies within the larger dotted circle. The location of the highest-energy photon recorded by GRO lies within the small dotted circle. maintain that the bursts come from merging neutron stars in a distant cosmos billions of light-years away. "This observation doesn't necessarily fit one model or the other," Hurley cautions. "The fact that there were delayed high-energy gamma rays is the significant part, but we don't yet know what to make of it." |
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