From Science:
Astronomers have, for the first time, discovered what seems to be a binary set of supermassive black holes. The galactic beasts are orbiting each other about every 100 years, and ultimately they will collide with enough force to trip gravitational-wave detectors on Earth. Spotting a single supermassive black hole is fairly easy, so much so that astronomers are convinced that one lurks in the center of just about every galaxy. Finding two supermassives locked in a binary orbit is another story. Only about as big as a solar system–though they can weigh as much as a billion suns–spotting them as distinct objects is as difficult as finding the proverbial needle in the haystack.
But that's what a pair of astronomers from the National Optical Astronomical Observatory in Tucson, Arizona, appear to have done. Todd Boroson and Tod Lauer were combing through the Sloan Digital Sky Survey, a collection of images and spectral information on hundreds of thousands of galaxies, when their software flagged a quasar whose light characteristics differed significantly from the rest of the sample. Quasars are the most luminous objects in the universe, and their brightness is thought to be caused by the energy from supermassive black holes consuming tremendous amounts of surrounding gas and dust.
More here.
