Background image: Artist’s impression of the violent formation of a gamma-ray burst (the polar jets) through the supernova explosion of a star.
Gamma-ray bursts are bright flashes of energetic gamma-ray radiation, lasting from tens of microseconds to minutes, occurring isotropically across the sky. First discovered by the Vela satellites in 1967, the bursts are believed to originate in supernova explosions where a highly collimated beam is generated. Some shorter-duration bursts appear to be of different origin, e.g. the merger of binary stars, particularly binary neutron stars.
The Vela satellites were launched by the USA to monitor compliance with the 1963 Partial Test Ban Treaty by nuclear-capable states. Gamma-ray emission from the Earth would be a tell-tale sign of nuclear processes, and thus violations. The discovery of extragalactic gamma-ray bursts was initially classified, and not publicly revealed until 1973.
Later satellites such as BeppoSAX and Fermi provide increasing statistics and detail on gamma-ray bursts.