Science & Tech

Chandra X-ray Observatory helps put pieces together on gamma-ray bursts

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Massive collapsed stars believed to generate mysterious blasts of high-energy radiation

Astronomers have long debated how gamma-ray bursts (or “GRBs”) originate. One theory contends that GRBs result when two “compact objects,” that is, neutron stars or black holes, collide and coalesce. Another theory speculates that a “hypernova,” a gigantic star collapsing on itself under its own weight, could cause these extremely energetic outbursts. An international team of scientists used NASA’s Chandra X-ray Observatory to observe iron emission lines from ejected material surrounding the gamma-ray burst (GRB) known as GRB991216. This is the first time emission lines associated with GRBs have been unambiguously detected and their properties precisely measured at X-ray wavelengths. This discovery strengthens the case for a “hypernova” model. “The discovery of iron lines in the X-ray spectrum is an important clue to our understanding of GRBs,” said Luigi Piro, lead author of the paper that appeared in the Nov. 3, 2000, issue of the journal Science. “Studying the immediate area around the GRB tells us a great deal about the origin of the GRB itself.”