"Supermassive Ghosts'--Astronomers Looking for a Star in Andromeda Galaxy Stumble Upon Orbiting Pair of Giant Black Holes 2.6 Billion Light Years Beyond

A background object in images of the nearby Andromeda galaxy has revealed what could be the most tightly coupled pair of supermassive black holes ever seen. "We were looking for a special type of star in M31 and thought we...