In January an international team of astronomers confirmed that one of the largest black holes in the universe is paired with a much smaller partner nearby—the first definitive observation of black holes in a close binary system [subscription required]. The clues coming from the supermassive quasar OJ287 were periodic flashes of light, which were occurring less than two years apart every 12 years or so. Team leader Mauri Valtonen of the University of Turku in Finland used equations derived from Einstein’s theory of general relativity to show that the pulses could be caused by a small, orbiting black hole plunging into the debris disk around the larger one, situated at one end of the orbital ellipse.
At a meeting of the American Astronomical Society in Austin, Texas, Valtonen described how this model predicted the timing of the most recent flare-up, in September 2007. “This latest observation leaves little choice but ...
