BACKGROUND: Astronomers have always thought that large stars die in one big explosion that creates a black hole. New data from NASA's Swift satellite indicates that a star dies through a series of explosions -- three or four of them -- before forming a black hole.
WHAT IS SWIFT: Swift was launched in November 2004 to collect and analyze data on gamma ray bursts and other higher-energy happenings in the universe. Using Swift's state-of-the-art X-ray and ultraviolet telescopes, astronomers can now see gamma ray bursts within minutes, instead of hours or days, and can thus catch a glimpse of newborn black holes.
WHAT THEY FOUND: Whenever a massive star explodes, first there is a blast of gamma rays, followed by intense pulses, or "hiccups," of X-rays. There have been hints of such activity before, but Swift has detected more than a dozen clear cases of multiple explosions. Scientists are now exploring several hypotheses to describe this new phenomenon.
ABOUT BLACK HOLES: A black hole forms when a massive star has used up all its fuel and explodes, becoming a supernova or its more powerful cousin, a hypernova. The reason the Sun and other stars emit light is because trillions of nuclear reactions are taking place at the cores. With core temperatures of millions of degrees, hydrogen atoms can convert into helium atoms, emitting radiation in the process. At some point, however, all the atoms are used up and no more nuclear fusion can take place. Without that outward counter-force to the pull of gravity, a star collapses inward, eventually reaching a point where the attractive gravitational force is so strong, not even light can escape.
The American Astronomical Society contributed to the information contained in the TV portion of this report.