X-ray flare from a dim source

Last Dec. 15, the Chandra X-ray Observatory stared at an old, failed star for 9 hours and saw absolutely nothing. That’s just what Gibor Basri of the University of California, Berkeley was hoping. The absence of radiation confirms that as failed stars, known as brown dwarfs, grow older, they lose their hot outer atmosphere, or corona, and can’t readily generate X-ray flares, he says.