The XO Directory

The biggest black hole in the universe weighs in with a respectable mass of 18 billion Suns, and is about the size of an entire galaxy. Just like in the Arnold Schwarzenegger and Danny Devito flick “Twins”, the massive black hole has a puny twin hovering nearby. By observing the orbit of the smaller black hole, astronomers are able to test Einstein's theory of general relativity with stronger gravitational fields than ever before. The biggest black hole beats out its nearest competitor by six times. Fortunately, it’s 3.5 billion light years away, forming the heart of a quasar called OJ287. Quasars are extremely bright objects in which matter spiraling into a giant black hole emits large amounts of radiation.