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Wednesday, September 8, 2010

The origin of super-massive black holes

A team of astronomers from the University of Zurich, Ohio State University, Universidad de Chile and Stanford University has developed new ideas about the formation of super-massive black holes in the early universe. Contrary to prior opinion, these black holes were formed by mergers between protogalaxies.

Let’s define a few terms. A super-massive black hole is exactly what the name implies: a ginormous black hole, hundreds of thousands to billions of times the mass of our sun. Most galaxies are now thought to contain a super-massive black hole in their centers. Protogalaxies are simply clouds of gas and stars that are in the process of forming into galaxies. Current estimates place the development of the first large galaxies at about one billion years after the Big Bang (or about thirteen billion years ago).

It had been thought that galaxies and their internal black holes grew in concert, that is, the galaxy and the black hole both slowly gained material as the protogalaxy developed. But according to new computer simulations, the black hole actually grows much more quickly. The new models show that the most massive black holes formed not by gradual accretion of material, but following mergers of large protogalaxies.

The following simulation shows how that could have happened:

Merger of two galaxies into a single structure, with super-massive black hole at the center.

Credit: University of Zurich/Ohio State University