Hubble image of NGC 1277NGC 1277: Hubble Space Telescope image of galaxy that may have commandeered another galaxy’s supermassive black hole.Image: NASA/ESA/Andrew C. Fabian

Do black holes jump ship and wander off to other galaxies? If so, a galaxy called NGC 1277 may harbor a fugitive in its core. In 2012 astronomers discovered a supermassive black hole at its center with the mass of 17 billion suns—the most massive known. Normally, a black hole this enormous would be found in a much larger galaxy, which points to something unusual in NGC 1277’s past. Two astronomers have one idea: What if the black hole was captured after being spit out of a galactic collision billions of years ago?

In fact, the black hole may be a reject from an even larger nearby galaxy. Billions of years ago two galaxies—each carrying a black hole in its core—slammed together to form a massive galaxy called NGC 1275. During the collision, the central black holes spiraled together, merged and recoiled into intergalactic space. The newly coalesced homeless black hole wandered the Perseus galaxy cluster until NGC 1277 passed close enough to gravitationally ensnare it. “It is speculative, but it’s a fun story,” says Gregory Shields, an astronomer at The University of Texas at Austin and lead author on a paper in The Astrophysical Journal Letters proposing this scenario. “You don’t need to invent any new physics. You just need to have the luck to run into the smaller galaxy.”

via Are Galaxies Playing Catch with Black Holes?: Scientific American.