Markarian 231 won't win any galactic beauty contests. Seen through the Hubble Space Telescope, it's a bit lopsided and dull. But boy, what a personality. This galaxy near the tail of the Big Dipper is, at a distance of 581 million light-years, the closest that contains a quasar—an ultraluminous region powered by the ravenous appetite of a single, giant black hole.
Or so it was thought. In August, Chinese astronomers, working with collaborators at the University of Oklahoma, reported that intense beams of optical and ultraviolet light shining from Markarian 231's center are best explained by not one but two invisible black holes, locked in fast orbit around each other. If the finding is confirmed, the pair will be the first binary black hole shown to drive a quasar, although the researchers suggest that such an arrangement may actually be the norm for quasars.
The smaller of Markarian 231's two black holes, they estimate, is 4.5 million times as massive as our sun—the same size as the black hole at the heart of the Milky Way. Its companion, however, appears to be more than 30 times larger. The shared orbit is almost 600 times wider than Earth's circular path around the sun, yet the duo takes only about 440 days to make a lap.
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The blue welts near the glimmering “eye” make Markarian 231 look like it lost a fight—and in a way, it did. Most likely, the astronomers say, this quasar formed when two smaller galaxies collided. But it was a creative destruction: thanks in part to the cosmic tug-of-war happening at Markarian 231's center, new stars are forming in that galaxy at 100 times the birthrate in the Milky Way.