Runaway black hole leaves trail of stars in its wake

A team of researchers has discovered a long, thin smear in an image taken by the Hubble Space Telescope, which appears to be the wake left behind by a supermassive black hole that's been shot free of the galaxy that used to host it. Its liberation likely resulted from two additional supermassive black holes, all brought together by a merger of galaxies. The streak is estimated to be about 200,000 light-years long and started forming about 40 million years ago, and its tip has been progressively moving away from the galaxy at about 1,600 kilometers a second since.