Black Holes are Double Trouble for Galaxy

Two monstrous black holes are jostling for power in the same galaxy, the Chandra X-ray satellite has revealed. The pair will slam into each other in a few hundred million years, giving the fabric of space-time a good shake.

"Today for the first time, thanks to the Chandra X-ray observatory's unparalleled ability to spot black holes, we see something that is a harbinger of a cataclysmic event to come," a NASA official told a press conference on Tuesday.

Stefanie Komossa of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and her colleagues used Chandra to look at an extraordinarily bright galaxy called NGC 6240, which is about 400 million light years from Earth.

This galaxy has two bright knots near its centre. "With Chandra, we hoped to determine which one, if either, of the nuclei was an active supermassive black hole," said Komossa. "Much to our surprise, we found that both were."

Chandra showed that both regions emit telltale X-rays generated by superhot matter falling onto a black hole near its event horizon, the point of no return.

The black holes in NGC 6240 are currently orbiting each other about 3000 light years apart. They will gradually get closer and eventually crash into one another. The dramatic collision will unleash intense radiation and gravitational waves, ripples in the fabric of space-time predicted by Einstein.

Although the astronomers call the discovery "surprising", it makes sense given that the shape of NGC 6240 implies that it is formed from two giant galaxies that have merged together relatively recently.

Most, if not all, large galaxies are thought to harbour a black hole, so it is not startling that a galaxy formed by a merger could have ended up with two.

Galactic collisions are common. In fact, NGC 6240 is a perfect vision of the fate of our own Galaxy, the Milky Way. In about four billion years, the Milky Way will collide with its neighbourhood rival, the giant spiral galaxy M31 in Andromeda.

The Original Story from: www.newscientist.com