Posted: Sat, Dec 28, 2002, 7:31 PM ET (0031 GMT)
Thanks to a fast-acting network of spacecraft and telescopes, astronomers were able to observe for the first time a class of "dark" gamma-ray bursts (GRBs). The GRB was observed on December 11 by NASA's High-Energy Transient Explorer (HETE) spacecraft, which relayed information about the location of the burst to ground-based telescopes within 22 seconds. One telescope, the RAPTOR (RAPid Telescopes for Optical Response) in New Mexico, took its first image of the GRB at optical wavelengths just 65 seconds after the burst was first detected. The telescopes were able to observe the optical afterglow of the burst that faded within two hours. Bursts with no detectable afterglow are called "dark" GRBs, and this one would likely have been classified as such had there not been such a rapid response to observe it, leading astronomers to question how many dark GRBs truly have no afterglow. About half of all GRBs observed to date are considered dark. The original burst, with a duration of 2.5 seconds, puts it into a rare class of "transitional" bursts that lie between short- and long-duration bursts.

Related Links:

•  NASA press release
•  SPACE.com article