Current understanding divides gamma-ray bursts into those that last less than two seconds and those of longer duration. The latter occur when a massive, young star goes supernova and leaves behind a black hole. The former happen when an old neutron star spirals into a preexisting black hole. The two kinds also differ in the type and intensity of energy released. But GRB060614, detected last June, fits neither category. Its duration of 102 seconds supports the longer-lasting variety, but the intensity of its emissions more closely matches the shorter-lasting one. “All the data seem to point to a new but perhaps not so uncommon kind of cosmic explosion,” says Neil Gehrels of the NASA Goddard Space Flight Center, lead author of one of four papers in the December 21 Nature describing the phenomenon. Indeed, other bursts also hint at similar “hybrids.” A possible explanation is the creation of black holes so powerful that the dying stars get no chance to supernova.
This article was originally published with the title "The Long and Short of It" in Scientific American 296, 3, 30 (March 2007)