The Odd Case of "0402+379": A Galaxy With Two Supermassive Black Holes

Scientist believe that most galaxies, certainly all the spiral ones, have such supermassive black holes in the center. Several have been observed or inferred by their radiation signatures, polar jets or other massively energetic effects. While the exact mechanics of such singularity-centrality have to be worked out, a simple picture can explain why they should be there. Of all the places in the universe, a galactic core is the most likely place for a vast star to form (and then collapse into a black hole), or for a smaller black hole to consume enough matter to become supermassive.

Once the hole passes a certain size its gravitational attraction will shape the orbits of everything it doesn't eat. It no longer matters if it was exactly at the center before - it's made itself the center now. Does this mean that asymmetric dwarf galaxies or globular clusters will eventually develop their own black hole pivot points? It seems inevitable: all black holes below a certain size evaporate, and above a certain size they just keep growing. Wait long enough and one will turn up. And eat you.

Galaxy 0402+379 is kind of an unimposing name for the greatest unexploded bomb in existence. It doesn't have one supermassive black hole - it has two, and is thought to be the result of a truly massive collision between two galaxies, each with only the standard "one mega-ultra-huge black hole per galaxy". A galactic collision is the second most amazingly violent event you can think of - the first will be when those two black holes eventually hit each other. The resulting merger will release energy on an utterly unprecedented scale, and emit gravity waves which will bend spacetime itself.

Posted by Luke McKinney.

Image courtesy of NRAO/AUI and Greg Taylor, University of New Mexico