Gamma-ray bursts: Going the distance.Astronomers Famous astronomers and astrophysicists include: Directory: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A
n. A short-lived, localized, and intense burst of gamma radiation that originates outside the solar system from an unknown source. . If the finding proves correct, scientists could use bursts to probe some of the earliest events in the cosmos. Although Earth-orbiting satellites record a burst popping off at least once a day, astronomers have measured the distance to only a handful. That's because scientists must find the fleeting, visible-light counterpart to the 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). and then determine its redshift--the amount by which the expansion of the universe has shifted the light to redder, or longer, wavelengths. Two researchers have now closely examined the six bursts for which astronomers have measured distances. Enrico Ramirez-Ruiz, now at the University of Cambridge in England, and Edward E. Fenimore of the Los Alamos Los Alamos (lôs ăl`əmōs', lŏs), uninc. town (1990 pop. 11,455), seat of Los Alamos co., N central N.Mex. It is on a long mesa extending from the Jemez Mts. The U.S. (N.M.) National Laboratory calculated the intrinsic brightness of each flash. They found that the most luminous flashes flicker the most, while those that are intrinsically dimmest vary the least. If that pattern holds true, scientists would have a new way to determine distance. They would simply compare the luminosity luminosity, in astronomy, the rate at which energy of all types is radiated by an object in all directions. A star's luminosity depends on its size and its temperature, varying as the square of the radius and the fourth power of the absolute surface temperature. of a burst, as indicated by the flickering, with the observed brightness, which declines as the inverse square of distance. Ramirez-Ruiz and Fenimore presented their findings last month at the annual gamma-ray-burst symposium in Huntsville, Ala. If the link between flickering and brightness proves reliable, a burst could serve as a new yardstick for measuring distances to other objects. Because bursts are bright enough to be detected from far away, the yardstick would allow astronomers to measure distances deep in space and far back in time, Fenimore says. "The correlation looks good, but there are still very few data points," says Stan Woosley of the University of California, Santa Cruz The University of California, Santa Cruz, also known as UC Santa Cruz or UCSC, is a public, collegiate university, one of the ten campuses of the University of California. . At the conference, Jay P. Norris 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., presented evidence for another type of distance indicator. Norris finds that the more luminous the measured burst, the smaller the lag time between its high-energy and low-energy photons. |
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