Wednesday, July 17, 2013

Feeding a black hole Online - BBC

VLT telescope for the first time made it possible to observe the feeding ground of our nearest supermassive black hole. If it escapes from a giant cloud, it will become clear in the near future.

At the center of our Milky Way galaxy has recently begun to unfold the drama that astronomers were waiting for the last year and a half. At the end of 2011 with the Very Large Telescope (VLT) European Southern Observatory (Chile), scientists first saw the giant cloud, rushing at a rate of 8,000,000 km. per hour in the direction of the object Sagittarius A * (Sgr A *) – a compact radio source, presumably representing a supermassive black hole, around which the entire galaxy.

Presumably

– because in astrophysics these facilities continue to be formally hypothetical, although their existence is confident the majority of astronomers. The fact that Sagittarius A * – a black hole mass of 4 million solar masses, for example, astronomers assure frantic rotation stars closest to it.

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Cloud in a few Earth masses (to G2) was found a group of scientists led by Stephen Gillessena of Institute for Extraterrestrial Physics, Max Planck in Garching (Germany). That’s when astronomers began to wait for the middle of 2013, when according to their calculations it was supposed to come close to the black hole.

Watching like a giant bunch of gas will be torn apart and partially absorbed by the supermassive black hole, astronomers manifestation of the promise of interesting new effects that can occur near black holes.

Observations on the VLT, made in 2013 by the integral field spectrometer SINFONI, brought the long-awaited results. Just the eyes of scientists, reaching the point of closest approach to the black hole, the cloud has been severely stretched and torn into pieces. According to scientists, the ionized gas at the head of the cloud is now stretches for more than 15 thousand Schwarzschild radii (the event horizon of a black hole) of perihelion around its elliptical orbit. “The gas in front of the cloud stretches for more than 160 billion miles. relative to the nearest point to the black hole. But the point itself is separated from the black hole is 25 billion kilometers., So that the cloud was almost dropped it, “- said Stefan Gillessen.

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«The cloud is so stretched that the rapprochement with the black hole will not momentary event, and will take at least one year”, – said the scientist.

Stretching

in space, the cloud turned white, and his form became less clearly visible on direct photographs. Therefore, its evolution, astronomers judged by the velocity of its various components, measuring the line shifts of individual elements in the spectral observations. For this we have to use the 20-hour exposure, a record for the observation of this point of space.

«The most exciting was the observation of the head of the cloud, which is rushing at us at a speed of 10 million miles. per second – 1% of the speed of light.

This indicates that the front part of the cloud has already passed the point closest to the hole “- says Reinhard Genzel , who studies the vicinity of the black hole for twenty years.

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While it remains unexplained the nature of this mysterious cloud, although versions rife. The observations show that the cloud is not a self-gravitating object. Is there a star inside it is an open question – astronomers can only impose a limit to the brightness of a star. According to one version, the cloud could have been formed recently as a result of collision of stellar winds from the nearby hot stars Wolf-Rayet . In another version of the gas was originally associated with a star and pulled away from her as she approached the hole.

However, recent observations, results which will be published in Astrophysical Journal, should clarify the nature of the object. “Like the hapless astronaut from the sci-fi movie, now cloud stretched so much that resembles spaghetti. This means that the stars within it, probably not, “- said Gillessen, the second time in eighteen months by drawing an analogy with spaghetti. “We now believe that the gas comes from the stars revolving around the hole,” – he added.

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