X-ray Echoes Map a Black Hole’s Disk

Some 3.9 billion years ago in the heart of a distant galaxy, the tidal pull of a monster black hole shredded a star that wandered too close. X-rays produced in this event first reached Earth on March 28, 2011, when they were detected by NASA's Swift satellite. Within days, scientists concluded that the outburst, now known as Swift J1644+57, represented both the tidal disruption of a star and the sudden flare-up of a previously inactive black hole.