Black holes that wander

Supermassive black holes that have escaped their host galaxies may be wandering the universe alone. Intriguing new observations i by NASA’s Chandra X-ray telescope have | revealed what appears to be a supermassive | black hole being “kicked out of a galaxy at enormous speed,” Francesca Civano of the Harvard-Smithsonian Center for Astrophysics tells Astronomers observed two distinct light sources from distant galaxy CID-42 racing away from one another at a speed of 3 million miles an hour. They also detected high-energy X-rays—believed to be signs of a black hole devouring gas—emitting from one of the light sources, but not from the other.

The best explanation for the phenomenon, Civano says, is that two galaxies, each with a central black hole, slammed together. The crash likely produced gravitational waves, or ripples in the fabric of space, of the sort Albert Einstein predicted would occur when incredibly heavy objects collided. The waves would have caused the new, supermassive black hole to recoil violently enough to tear it away from its host galaxy altogether. If this analysis is correct, there may be many supermassive black holes roaming through deep space, invisible to us because there’s nothing for them to consume.