gamma-ray burst

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A short-lived, localized, and intense burst of gamma radiation that originates outside the solar system from an unknown source.

Wiktionary

1. n. astronomy A flash of gamma rays that seem to originate from a random point in the sky; their most likely sources are believed to be supernova explosions of a very massive stars and mergers of neutron stars.