The largest known black hole has a mass of 18 billion Suns!

Located 3.5 billion light years away, this black hole is SO massive that it weighs six times as much as the previous record-holder and is contains about the same mass as a small galaxy! The gravitational field of the giant is so strong that it actually causes a smaller black hole with the mass of 100 million Suns to orbit it! At two points in every 12-year orbit, the smaller hole gets close enough to break through the matter on the outer edge of the larger hole, which causes an outburst that makes the surrounding quasar suddenly brighten. A quasar is a bright celestial object into which matter entering a black hole emits large amounts of radiation.