Gamma-ray bursts (GRBs) are streams of high energy photons from space, first detected in the 1960s by the United States’ Vela satellites, designed to detect clandestine nuclear weapons tests in space.
Most GRBs are believed to originate from supernova explosions, when rapidly rotating, high-mass stars emit a narrow beam of intense electromagnetic radiation as their cores collapse to form a neutron star, quark star or black hole.
A second proposed mechanism, responsible for what are termed short gamma-ray bursts, is the merger of two neutron stars in a binary system.
GBRs are the most energetic electromagnetic events known, with total energies equivalent to the mass of the Earth emitted in a pulse lasting from a few milliseconds to a few hours.
GBRs are usually followed by a longer afterglow, where electromagnetic energy of longer wavelengths is emitted.