Astronomers link gamma-ray bursts, supernovae

Gamma-ray bursts are incredibly bright flashes of high-energy radiation that likely signal the birth of black holes. Bursts occur at random locations scattered across the sky, and few last more than a minute, making them a challenge to study. A supernova is the explosion of a star at least eight times as massive as the Sun. When such stars deplete their nuclear fuel, they no longer have the energy to support their mass. Their cores implode, forming either a neutron star or (if there is enough mass) a black hole. Could the two be related? Astronomers didn’t know for sure until a recent investigation uncovered the connection. “There should no longer be doubt in anybody’s mind that gamma-ray bursts and supernovae are connected,” said Thomas Matheson of the Harvard-Smithsonian Center for Astrophysics, a member of the team that made this discovery. The investigation began on March 29, 2003, when NASA’s High-Energy Transient Explorer satellite discovered one of the brightest and closest gamma-ray bursts on record. Located in the constellation Leo, the 30-second burst outshone the entire Universe in gamma rays, and its optical afterglow was still over a trillion times brighter than the Sun two hours later. Through observations of that afterglow on subsequent nights, astronomers spotted the telltale signs of a supernova. The team cannot yet determine the timing of the burst relative to the supernova (whether one preceded the other or whether both began at the same time), but the same event – a star explosion – was certainly the trigger for both.