Space

Black Holes, the Galaxy-Devouring Cosmic Piranhas

They eat up young galaxies with voracious appetite

By Lucian Dorneanu, Science Editor

25th of July 2007, 08:16 GMT

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The galaxy cluster in the left image is almost completely devoured by its active galactic nucleus, utin almost nothing is left, as it shows in the right picture

Black holes are space objects which have an immense gravitational field that cuts off a region of space from the rest of the universe, trapping all matter and radiation that enters that region. They are objects with a gravitational field so powerful that a region of space becomes cut off from the rest of the universe. Not even radiation (including light) that has entered the region

can ever escape.

A new study made by astronomers, using NASA's Chandra X-ray Observatory, analyzed the number of rapidly growing supermassive black holes, called active galactic nuclei in two populations of galaxy clusters and reached a grim conclusion.

These supermassive black holes devour all the gas inside young galaxies, until little fuel is left and then they fade away. In the process, the galaxies are shrunk to little bits, not nearly enough to form new stars, planet and life.

One of the observed groups consisted of young-looking clusters located very far from Earth and the other consisted of an older group located closer to us. The results indicated that the more distant, younger clusters contained about 20 times more active galactic nuclei (AGN) than nearer ones.

The implication, said study team member Paul Martini of Ohio State University, "is that when clusters were young, there were much more AGN present in the cluster galaxies. As the clusters galaxies continued to evolve, the AGN faded away."

So it seems that as the cluster gets older, less gas fuel is available for their central to consume and they become less active. "Really it's the activity of the black hole that has faded away," Martini told Space.com. "The black hole is still there and the galaxy is still there as well. It's just the activity that we see from the black hole has diminished a great deal."

The ultimate fate of the galaxies is a sad one, as galaxies in clusters become starved of gas over time and black hole activity and star formation in these galaxies slows. "There's no freshening of the gas in the cluster galaxies themselves," concluded Martini.

TAGS:

black | hole | galaxy | cluster | gas

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