4/29/2009 PERMALINK
Hundreds of roaming rogue black holes ripping planets from their stars
It sounds like the plot of a sci-fi movie, rogue black holes roaming our galaxy, destroying stellar systems. But it is probably fact, not fiction. New calculations by Ryan O'Leary and Avi Loeb of the Harvard-Smithsonian Center for Astrophysics suggest that hundreds of massive black holes are wandering the Milky Way.

These rogue black holes would have originally lurked at the centers of tiny, low-mass galaxies. Over billions of years, those dwarf galaxies smashed together to form full-sized galaxies like the Milky Way.

Each time two proto-galaxies with central black holes collided, their black holes merged to form a single, "relic" black hole. During the merger, directional emission of gravitational radiation would cause the black hole to recoil. A typical kick would send the black hole speeding outward fast enough to escape its host dwarf galaxy, but not fast enough to leave the galactic neighborhood completely. As a result, such black holes would still be around today in the outer reaches of the Milky Way halo.

Hundreds of rogue black holes should be traveling the Milky Way's outskirts, each containing the mass of 1,000 to 100,000 suns.... READ