What is a gamma-ray burst?

Gamma-ray bursts are brief but enormous releases of energy, lasting from milliseconds to several minutes. Long bursts are thought to come from the collapse of massive stars into black holes, while short bursts are linked to mergers of neutron stars. In a few seconds a burst can release as much energy as the Sun will emit over its entire 10-billion-year lifetime. They were discovered by accident in 1967 by US Vela satellites built to detect secret nuclear tests. In 2017 a short burst was detected alongside gravitational waves from a neutron star merger, confirming that link.