I'm going to start this blog talking about my favorite quasar, OJ287. Quoting from http://stardate.org/radio/program/2008-03-24:
It's hard to think of a black hole that's a hundred million times as massive as the Sun as little. But in a distant quasar known as OJ 287, that may be the case. According to a team of astronomers that studied the system, the black hole appears to orbit another black hole that's the most massive yet discovered -- 18 billion times the mass of the Sun.A quasar is a small object that can outshine an entire galaxy of normal stars. It's probably powered by a disk of superhot gas spiraling around a supermassive black hole.Astronomers have been watching OJ 287 for more than a century. It's about three and a half billion light-years away, and it looks like a faint, fuzzy galaxy. But twice every 12 years, it flares up. Each outburst lasts a few days.Although many astronomers are skeptical, an international team says the flareups and other evidence suggest that the system consists of two giant black holes. The smaller one orbits its bigger cousin once every 12 years. Its orbit is stretched out, and it's tilted. So twice during each orbit, it passes through the hot gas surrounding the bigger black hole, causing the flareups.The team tested this model last year. It predicted that a flareup would occur on September 13th -- and it came right on cue, bolstering the model of how OJ 287 works. The same team of astronomers will be looking for more evidence when the next outburst is due -- in about eight years."
As you can see, OJ287 is a very interesting quasar. The black hole is about six times as massive as the previous record holder and in fact weighs as much as a small galaxy. It lurks 3.5 billion light years away, and forms the heart of a quasar called OJ287. A quasar is an extremely bright object in which matter spiralling into a giant black hole emits copious amounts of radiation.But rather than hosting just a single colossal black hole, the quasar appears to harbour two - a setup that has allowed astronomers to accurately 'weigh' the larger one.The smaller black hole, which weighs about 100 million Suns, orbits the larger one on an oval-shaped path every 12 years. It comes close enough to punch through the disc of matter surrounding the larger black hole twice each orbit, causing a pair of outbursts that make OJ287 suddenly brighten. General relativity predicts that the smaller hole's orbit itself should rotate, or precess, over time, so that the point at which it comes nearest its neighbour moves around in space - an effect seen in Mercury's orbit around the Sun, albeit on a smaller scale.