Gamma-ray bursts are common, yet random, and fleeting events that have mystified astronomers since their discovery in the late 1960s. Many scientists say longer bursts (more than four seconds in duration) are caused by massive star explosions; shorter bursts (less than two seconds in duration) are caused by mergers of binary systems with black holes or neutron stars. While uncertainty remains, most scientists say in either scenario a new black hole is born. (Illustration: NASA/D.Berry)
