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Black Holes Bound to Merge

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Black Holes Bound to Merge

By Robert Roy Britt

Senior Science Writer

posted: 06 April 2006

11:48 am ET

Two supermassive black holes have been found to be spiraling toward a merger, astronomers said today.

The collision will create a single super-supermassive black hole capable of swallowing material equal to billions of stars, the researchers said.

Mergers between black holes are thought to be one way they grow. A handful of similar setups have been observed in which black holes appear inevitably on a merger course. This pair, at the center of a galaxy cluster called Abell 400, was known to be close but their fate hadn't been determined.

"The question was: Is this pair of supermassive black holes an old married couple, or just strangers passing in the night?" said Craig Sarazin of the University of Virginia. "We now know that they are coupled, but more like the mating of black widow spiders. One of the black holes invariably will eat the other."

Black holes can't be seen. Their presence is inferred by their gravitational effects on their surroundings and by radiation from near the black hole, where a feeding frenzy superheats gas so much that it emits X-rays.

Determining that these two black holes will collide involved other indirect evidence, drawing data from NASA's Chandra X-ray Observatory.

Each of the black holes in Abell 400 is ejecting a pair of oppositely directed jets of superheated gas called plasma. The movement of the black holes through gas in the galaxy cluster causes the plasma jets to be swept backward.

"The jets are similar to the contrails produced by planes as they fly through the air on Earth," Sarazin said. "From the contrails, we can determine where the planes have been, and in which direction they are going. What we see is that the jets are bent together and intertwined, which indicates that the pair of supermassive black holes are bound and moving together."

When the objects merge several million years from now, Einstein's theory of relativity predicts they will emit a burst of gravitational waves. Similar mergers could soon be detected by NASA's planned Laser Interferometer Space Antenna (LISA).

The results will be published in an upcoming issue of the journal Astronomy & Astrophysics.

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When Black Holes Merge

By Staff

posted: 07:00 am ET

31 January 2002

Huge black holes that populated the early universe may have grown by mergers, scientists say, but the details of the process are not well known.

A new set of calculations shows how a merger might involve a slow dance lasting up to 10 million years, ending in a violent outflow of energy. The sudden burst could help explain a tendency in the largest black holes -- supermassive objects -- to be either "on" or "off" in terms of their energy emissions.

Other researchers have sought clues to this on/off switch. The new study looked at how two merging supermassive black holes, one larger than the other, might be the cause.

"It's a violent, very high-energy event," said Priyamvada Natarajan, assistant professor of astronomy at Yale University and one of the authors of an article that will appear in Astrophysical Journal Letters. Philip Armitage, an assistant professor at the University of Colorado, is the paper's lead author.

Black holes are dense objects that trap anything that enters them, including light. Astronomers say most large galaxies have one at their centers. Because they can't be seen, black holes are difficult to study, and technically they exist only in theory. They are detected by noting how their incredible gravity affects their surroundings.

Any matter spiraling into a black hole does so in a so-called accretion disk, a fairly flat plane of material that surrounds the central object. As the material gets closer, it approaches the speed of light, becomes superheated, and emits X-rays (which is one other way astronomers detect black holes).

Some black holes, at the centers of bright galaxies called quasars, are among the most energetic objects known and exist in the distant reaches of the universe, which means they are very old. But not all black holes emit X-rays. The one at the center of our Milky Way Galaxy emits almost none.

In the computer simulation, two supermassive black holes become embedded in an accretion disk. They sit quietly at first, then slowly their orbit shrinks, causing them to move closer together, Natarajan said.

"What is interesting during this phase is the critical separation stage when the black holes get close enough and all the gas trapped between them immediately rushes to the more massive black hole, leading to a brief increase in brightness coupled with an energetic outflow of gas at very high speeds," she said.


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Posted (edited)

Data strongly supports the idea that the hard X-ray emission of Sgr B2 is Compton scattered and reprocessed radiation emitted 300 years ago by Sgr A*, the supermassive black-hole candidate in the center of our Galaxy.


Edited by magnetar

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Wow, impressive, thanks for the link. :yes:

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