Astronomers recently discovered the largest known black hole in the universe. At the center of quasar OJ287 is a super-massive black hole with a mass equivalent to 18 billion suns which is roughly the mass of a small galaxy. Even more interesting is that a second black hole, a smaller mass of 100 million suns, also lies in the quasar and orbits around the first. The two are expected to collide in 10,000 years.