New class of celestial bursters.New class of celestial bursters Up to now astronomers have known two classes of bursting sources of high-energy radiation in the sky, gamma-ray bursters and X-ray bursters. Gamma-ray bursters tend to burst once and not again. Nobody is sure whether they are in our galaxy or out of it. X-ray bursters repeat and seem to be clustered in the bulge of our galaxy. Now there is a third class, represented so far by one object, called by its discoverers Soft Gamma Repeater A soft gamma repeater is an astronomical object, now known to be a type of magnetar, which emits large bursts of gamma rays and X-rays at irregular intervals. On March 5, 1979 a powerful gamma ray burst was noted. 1806-20. In two papers in the Sept. 15 ASTROPHYSICAL JOURNAL The Astrophysical Journal, often abbreviated to ApJ, is a scientific journal covering astronomy and astrophysics. It was founded in 1895 by George Ellery Hale and James E. Keeler. It currently (October 2006) publishes three issues per month, with 500 pages per issue. , 17 scientists from France, the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. and the Soviet Union report observations of SGR SGR Sustainable Growth Rate SGR Societa' di Gestione del Risparmio (Italian: Investment Management Company) SGR Specific Growth Rate SGR Surgeon General's Report SGR Soft Gamma-ray Repeater 1806-20 since it was first noticed on Jan. 7, 1979. The accumulated data indicate that although the shape of the object's pulses in time resembles that of a gamma-ray burster A mechanical device that separates continuous paper forms into cut sheets. A burster can be attached to the end of a collator, which separates multipart forms into single parts. , it repeats like an X-ray burster. It has repeated 100 times between Aug. 13, 1978 and June 27, 1986. Its spectral characteristics lie between the other two classes. Gamma-ray bursters may lie outside our galaxy, and some theorists have suggested exotic explanations for them--for example, that they are vibrating vibrating, v using quivering hand motions made across the client's body for therapeutic purposes. cosmic strings (SN: 5/30/87, p.345). X-ray bursters are probably in our galaxy and may be stars that suffer periodic nuclear explosions on their surfaces. If the Soft Gamma Repeater source lies on the galactic bulge, where the X-ray bursters are believed to be, its discoverers calculate that it would have to be 1,500 times as bright as they are. However, certain of its characteristics suggest it may be much closer, perhaps as near as 6 parsecs (20 light-years). |
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