Short cosmic blasts of very high energy electromagnetic radiation (gamma radiation) that are recorded at an average of about once per day by detectors placed above the Earth's atmosphere. At distances of billions of light-years, the energy emitted in a gamma-ray burst (GRB) is more than a billion billion (10¹⁸) times the energy emitted each second by the Sun. The mechanism for the origin of gamma-ray bursts remains a focus of current research. Gamma-ray bursts longer than 2 seconds appear to be associated with the supernova explosions of massive stars in distant galaxies. Recent evidence suggests that shorter gamma-ray bursts are the result of merging neutron stars or black holes. There are indications that both types of gamma-ray bursts lead to the birth of black holes.