Friday, April 9, 2010

True Heavyweight

In the previous two posts, I wrote about some fascinating stuff involving the application of micro black holes and I also explored an interesting alternative to conventional black holes. In this post, I am going to write about the most massive black hole currently known in the universe, even though there are probably a lot more yet-to-be-discovered black holes which can be more massive than this current record holder.

OJ 287 is a pair of supermassive black holes residing in the heart of a distant galaxy located 3.5 billion light years away, where one light year is the distance light travels in one year. The primary black hole of OJ 287 contains an incredible 18 billion times the mass of the Sun while the secondary black hole contains 150 million times the mass of the Sun. This makes the primary black hole of OJ 287 one of the most massive known black holes in the universe. To put things into perspective, the supermassive black hole in the core of our Milky Way Galaxy is a mere 4 million times the mass of our Sun and the Sun alone is already 333 thousand times more massive than the Earth.

With 18 billion times the mass of the Sun, the event horizon of the monstrous primary black hole of OJ 287 will span an astonishing 110 billion kilometres in diameter. This means that about 80 thousand Suns or 9 million Earths placed end-to-end are required to span the diameter of the black hole’s event horizon. Note that the event horizon of a black hole is a region surrounding it where gravity becomes so strong that it does not let even light to escape.

The much less massive secondary black hole of OJ 287 orbits the primary black hole with a period of 11 to 12 years. Two outbursts are observed from OJ 287 every 11 to 12 years as the secondary black hole intersects the accretion disk of the much more massive primary black hole with a frequency of twice per orbit. The orbit of the secondary black hole around the primary black hole is gradually decaying via the emission of gravitational radiation and the secondary black hole is expected to merge with the primary black hole within 10 thousand years.