The galaxy cluster PKS 0745-19 is shown in this NASA composite image containing X-rays from Chandra (purple) and optical date from the Hubble Telescope (yellow) released December 19, 2012. The black hole at the center of this galaxy is part of a survey of 18 of the biggest known black holes in the universe. Researchers found that the black holes in the survey may be about ten times more massive than previously thought. (Photo by Reuters/NASA/CXC/Stanford)
