A gamma-ray burst's enduring fireball.It's the cosmic ember that keeps on glowing. Last March, astronomers spied for the first time in visible light the smoldering smol·der also smoul·der intr.v. smol·dered, smol·der·ing, smol·ders 1. To burn with little smoke and no flame. 2. remnant of a gamma-ray burst--a titanic explosion that unleashes its 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 in a matter of seconds (SN: 5/17/97, p. 305). This afterglow afterglow small amounts of light emitted by a phosphor after the stimulating radiation has ceased. Seen in x-ray intensifying screens and fluoroscopic screens. has since faded substantially, but it remains visible in images taken Sept. 5 by the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. . The duration of the afterglow and its slow decline provide further evidence that bursts originate far beyond the Milky Way rather than inside it, Hubble scientists assert. Astronomers have long debated the origin of gamma-ray bursts. A nearby burst carries much less energy than a faraway burst of the same observed brightness. Therefore, if the fireball imaged by Hubble, called GRB GRB Gamma Ray Burst(er) GRB Graduate Recruitment Bureau GRB Grid Resource Broker GRB Grootschalig Referentiebestand (Dutch: large scale mapping program) GRB Gharb 970228, had erupted in the Milky Way, it would have packed less of a wallop and faded drastically after a few days, says Mario Livio of the Space Telescope Science Institute The Space Telescope Science Institute (STScI) is the science operations center for the Hubble Space Telescope (HST; in orbit since 1990) and for the James Webb Space Telescope (JWST; scheduled to be launched in 2013). (STScI) in Baltimore. "We've followed this [burst] for 6 months, and it continues to decay at the same rate," says Livio. "This strongly argues that the burst is distant." He points out that the fading fireball lies at the edge of a fuzzy blob that remains as bright as when Hubble imaged it in March. This suggests that the blob is a galaxy, perhaps the one in which the burst exploded, rather than material temporarily heated by the fireball. Livio and his colleagues, including Andrew S. Fruchter and Kailash C. Sahu of STScI and Elena Pian of the Italian National Research Council in Bologna, reported the findings last week at a meeting in Huntsville, Ala., on gamma-ray bursts. Last May, researchers measured for the first time the distance to a gammaray burst, called GRB 970508, proving that it resided far beyond the Milky Way (SN: 5/31/97, p. 335). Although scientists have compelling data on only 2 of the roughly 3,000 bursts detected, "there's no way to defend the [Milky Way] origin at the moment," says Bohdan Paczynski of Princeton University. The source of the bursts remains "anybody's guess," he adds. With instruments on three spacecraft--the repaired BeppoSAX satellite, the Rossi X-ray Timing Explorer The Rossi X-ray Timing Explorer (RXTE) satellite observes the fast-moving, high-energy worlds of black holes, neutron stars, X-ray pulsars and bursts of X-rays that light up the sky and then disappear forever. , and the Compton Gamma Ray Observatory--searching for flashes, an answer may not be long in coming. |
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