Astronomers think some of these explosions occur when a massive star — five or 10 times the mass of our sun — detonates, abruptly becoming a black hole. Gamma-ray bursts may also occur when two superdense stellar corpses called neutron stars collide, often forming a black hole. And conveniently, a gamma-ray burst that scientists watched during a few nights in 2019 likely occurred only about 1 billion light-years away from Earth, relatively close by for these dramatic events. Two NASA space-based observatories, Fermi and Swift, first detected the event, which is known as GRB 190829A because it was detected on...