Fleeting flash: pinpointing a short gamma-ray burst.An invisible, highly energetic flash detected by a spacecraft early this week may have given astronomers their first glimpse of two neutron stars crashing together, forging a black hole at a galaxy's edge. NASA's Swift satellite detected the flash--a burst of gamma rays that lasted one-twentieth of a second--on May 9. Fifty-three seconds later, the craft slewed its X-ray telescope toward the same spot in the sky, fast enough to catch a rapidly fading 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. . The X-ray detection marks the first time that astronomers have identified the location of a short-duration gamma-ray burst, which lasts less than 2 seconds, says Swift project scientist Neil Gehrels of NASA's Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. Astronomers worldwide raced to find the galaxy from which the burst emanated as well as a possible visible-light afterglow of the cataclysmic cat·a·clysm n. 1. A violent upheaval that causes great destruction or brings about a fundamental change. 2. A violent and sudden change in the earth's crust. 3. A devastating flood. event. With Swift's X-ray data as guidance and using two telescopes in Arizona, the WIYN WIYN Wisconsin, Indiana, Yale, NOAO (consortium) WIYN What Is Your Number? Telescope on Kitt Peak and the PAIRITEL on Mount Hopkins, Josh Bloom of 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 and his colleagues found an elliptical galaxy, devoid of new stars, that lies about 2.7 billon bil·lon n. 1. An alloy of gold or silver with a greater proportion of another metal, such as copper, used in making coins. 2. An alloy of silver with a high percentage of copper, used in making medals and tokens. light-years from Earth. The X-ray afterglow appears to coincide with the outskirts of this galaxy. Researchers haven't come to a consensus about whether this burst generated a visible-light afterglow. The characteristics of the burst, along with the discovery of the elliptical galaxy, suggest that the flash was generated by the collision of two extremely compact objects--either a pair of neutron stars or a neutron star coalescing with an even more-compact body, a black hole. The dense cinder cin·der n. 1. a. A burned or partly burned substance, such as coal, that is not reduced to ashes but is incapable of further combustion. b. A partly charred substance that can burn further but without flame. of an exploded massive star, a neutron star packs as much material as the sun into a sphere 20 kilometers in diameter. Theorists proposed nearly 20 years ago that the collision of two neutron stars produces a variety of gamma-ray bursts, but the collisions are now believed to generate only shorter-lived bursts. These account for about one-third of all bursts. Simulations suggest that the merger of two neutron stars generates an extremely energetic, short-lived blast of gamma rays, with little if any visible-light emission--just as the May 9 burst, which is now dubbed GRB 050509b, did. Another feature of the finding suggests coalescing neutron stars. In the billion years that it takes a pair of neutron stars to spiral together, they can migrate far from a star-birthing region, including a place like the outskirts of an elderly elliptical galaxy. In contrast, long-lived gamma-ray bursts--which last for more than 2 seconds--are probably generated during massive supernova explosions, which typically occur in star-birthing regions. The after-glows of long-duration bursts can last for days and include visible light. "It has long been suspected that short-lived gamma-ray bursts are a very different beast [than the longer-lived ones], but now there's no question," says Shri Kulkarni of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena. He cautions that it's uncertain whether the observed elliptical galaxy is the host of GRB 050509b. Using the Keck Observatory on Mauna Kea in Hawaii, his team has found several other candidate sources for the burst. 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. will soon scan the region. At press time, the Chandra X-ray Observatory Chandra X-ray Observatory U.S. X-ray space telescope. It was named after astrophysicist Subrahmanyan Chandrasekhar and was launched into orbit in 1999. Its mirror, with an aperture of 1.2 m (4 ft) and a focal length of 10 m (33 ft), produces unprecedented resolution. had also been slated to take a look. "We're using all our premiere telescopes to shed any light that we can" on the burst, says Kulkarni. |
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