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Post Info TOPIC: Abell 400 black holes


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3C 75 in Abell 400: Black Holes Determined to be Bound
This composite X-ray/radio image of the galaxy cluster Abell 400 shows radio jets immersed in a vast cloud of multimillion degree X-ray emitting gas that pervades the cluster.

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Position (2000) : RA = 02h 57m 41.58s Dec = +06 01' 28.81

This composite X-ray (blue)/radio (pink) image of the galaxy cluster Abell 400 in the constellation Cetus shows radio jets immersed in a vast cloud of multimillion degree X-ray emitting gas that pervades the cluster. The jets emanate from the vicinity of two supermassive black holes (bright spots in the image). These black holes are in the dumbbell galaxy NGC 1128, which has produced the giant radio source, 3C 75.

The peculiar dumbbell structure of this galaxy is thought to be due to two large galaxies that are in the process of merging. Such mergers are common in the relatively congested environment of galaxy clusters. An alternative hypothesis is that the apparent structure is the result of a coincidence in time when the two galaxies are passing one another, like ships in the cosmic sea.

Careful analysis of the recent Chandra and radio data on 3C 75 indicates that the galaxies and their supermassive black holes are indeed bound together by their mutual gravity. By using the shape and direction of the radio jets, astronomers were able to determine the direction of the motion of the black holes. The swept-back appearance of the radio jets is produced by the rapid motion of the galaxy through the hot gas of the cluster, in much the same way that a motorcyclist's scarf is swept back while speeding down the road.

The binary black holes in 3C 75 are about 25,000 light years apart. They are likely at an earlier stage in their evolution than the pair found in NGC 6240, which are about 3,000 light years apart. Computer simulations indicate that binary supermassive black holes gradually spiral toward each other until they coalesce to form a single, more massive black hole, accompanied by an enormous burst of gravitational waves.

These gravitational waves would spread through the Universe and produce ripples in the fabric of space, which would appear as minute changes in the distance between any two points. Sensitive gravitational wave detectors scheduled to be operational in the next decade could detect one of these events, which are estimated to occur several times each year in the observable Universe.



Posts: 131433
Abell 400 black holes

A pair of supermassive black holes in the distant universe are intertwined and spiralling toward a merger that will create a single super-supermassive black hole capable of swallowing billions of stars, according to a new study by astronomers at the University of Virginia, Bonn University and the U.S. Naval Research Laboratory.

The study appears in the April 6, 2006 issue of the journal Astronomy & Astrophysics.

Black holes are among the oldest regions of the universe and hold clues to understanding the formation of the universe and its destiny. Though astronomers have theorized that coupled black holes exist, and that black holes sometimes merge and form supermassive black holes, the new study provides further evidence that this in fact occurs.

"The two key questions about supermassive black holes are: Where do they come from and how do they grow over time? The birth, care and nurturing of supermassive black holes is a very active area of study in astronomy." - Craig Sarazin, W.H. Vanderbilt Professor of Astronomy at the University of Virginia and co-author of the study.

Supermassive black holes are areas in space that are so dense and massive they contain up to billions of stars and continually suck in more stars, further building their mass and gravitational pull. Even light cannot escape the pull of gravity in a black hole. The area appears as it is described: a black hole in space.

"Black holes are the ultimate garbage disposals. The material they swallow disappears without any trace, except for the gravity of the black hole."- Craig Sarazin.

Sarazin and his colleagues used NASA's Chandra X-ray Observatory to glean their results. Black holes are detectable because they produce large amounts of X-ray emission, similar to the radiation used for medical diagnosis. This high-energy radiation is invisible to our eyes, but can be seen with X-ray telescopes.

"There is no way to determine how a black hole was created or what kinds of things it has swallowed just by looking at the resulting black hole. You have to catch the black hole when it is sitting down to dinner or still eating." - Craig Sarazin

That, essentially, is what the Sarazin team has accomplished. They focused their observations on the centre of a cluster of galaxies named Abell 400 where astronomers had previously suggested that a pair of supermassive black holes might be colliding. The two holes seemed to be relatively close together, but there was no proof that they were bound to one another or merging.

"The question was: Is this pair of supermassive black holes an old married couple, or just strangers passing in the night? 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"- Craig Sarazin.

NASA is interested in helping astronomers better understand the formation of supermassive black holes and is currently planning to build an array of three space satellites called LISA (Laser Interferometry Space Antenna) to detect gravity waves from merging black holes.

"Obviously, astronomers would like to be certain that this process of supermassive black hole mergers really does occur, so that LISA will have something to detect."- Craig Sarazin.

In recent years, astronomers have discovered that every large galaxy in the present day universe likely has a supermassive black hole. The Milky Way's own supermassive black hole has swallowed as much material as four million suns. The biggest galaxies contain black holes that have swallowed many billions of stars worth of material.
In some cases, two galaxies containing supermassive black holes collide and merge together, and eventually the two supermassive black holes fall into the centre of the merged larger galaxy, and spiral together. Ultimately, they merge into one even larger hole. Sarazin's team found that the two merging supermassive black holes in Abell 400 appear to be swallowing gas from their host galaxy, and each is ejecting a pair of oppositely-directed jets of radio-emitting plasma. As the supermassive black holes fall through the gas in the cluster Abell 400, jets of radio-emitting plasma are swept back behind them.

"The jets are similar to the contrails produced by planes as they fly through the air on Earth. 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"- Craig Sarazin.


-- Edited by Blobrana at 08:41, 2006-04-06

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