On 28 March, NASA’s Swift satellite
observed a flash of gamma rays brighter than anything astronomers had seen before. It soon became evident that the event wasn’t a typical gamma ray burst, an emission of high-energy radiation that often accompanies a supernova
explosion. The flash didn’t die out but was sustained for weeks, and although it has faded in intensity, it is still going strong 2½ months later. Two
papers published online today in Science provide an explanation for this luminous surprise. The flare is in fact a high-energy jet of radiation produced by a star falling into a black
hole at the center of a galaxy 4 billion light-years away. The reason the flare is so bright is that the jet is pointed straight in the direction of
Earth. And it’s sustained because the black hole is consuming the star gradually. “That’s because as the
black hole rips the star apart, the mass swirls around like water going down a drain, and this swirling process releases a lot of energy,” says Joshua
Bloom, an astronomer at the University of California, Berkeley, and lead author of one of the two papers. Bloom expects the flare to fade out over the
next year.
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