domingo, 25 de marzo de 2012

Becoming Supermassive! -- New Insights into HyperGrowth of Black Holes


The two biggest black holes ever discovered are each about ten billion times bigger than the Sun. Now, a team from the University of Leicester (UK) and Monash University in Australia sought to establish how black holes get so big so fast. 

"Almost every galaxy has an enormously massive black hole in its center,said Andrew King from the Department of Physics and Astronomy, University of Leicester. "Our own galaxy, the Milky Way, has one about four million times heavier than the sun. But some galaxies have black holes a thousand times heavier still. We know they grew very quickly after the Big Bang.''
"These hugely massive black holes were already full--grown when the universe was very young, less than a tenth of its present age," he added.
Black holes grow by sucking in gas. This forms a disc around the hole and spirals in, but usually so slowly that the holes could not have grown to these huge masses in the entire age of the universe. `We needed a faster mechanism,' says Chris Nixon, also at Leicester, "so we wondered what would happen if gas came in from different directions."
Nixon, King and their colleague Daniel Price in Australia made a computer simulation of two gas discs orbiting a black hole at different angles. After a short time the discs spread and collide, and large amounts of gas fall into the hole. According to their calculations black holes can grow 1,000 times faster when this happens.
"If two guys ride motorbikes on a Wall of Death and they collide, they lose the centrifugal force holding them to the walls and fall," says King. The same thing happens to the gas in these discs, and it falls in towards the hole.
This may explain how these black holes got so big so fast. "We don't know exactly how gas flows inside galaxies in the early universe," said King, "but I think it is very promising that if the flows are chaotic it is very easy for the black hole to feed."
NASA's Spitzer Space Telescope has imaged the coiled galaxy at top of the page with an eye-like object at its center. The 'eye' at the center of the galaxy is actually a monstrous black hole surrounded by a ring of stars. In this color-coded infrared view from Spitzer, the area around the invisible black hole is blue and the ring of stars, white. The galaxy, called NGC 1097 and located 50 million light-years away, is spiral-shaped like our Milky Way, with long, spindly arms of stars.
The black hole is huge, about 100 million times the mass of our sun, and is feeding off gas and dust, along with the occasional unlucky star. Our Milky Way's central black hole is tame in comparison, with a mass of a few million suns.
The image above of the central 5,500 light-years-wide region of NGC 1097 has than 300 star forming regions - white spots in the image - which are distributed along a ring of dust and gas. At the center is a bright central source where the active galactic nucleus and its super-massive black hole are located.
Image credit: NASA/Hubble Space Telescope
Source: The Daily Galaxy - University of Leicester, UK 

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