Column density projection showing the disc structure for the ? = 120? simulation. The disc has evolved for about 50 dynamical times (about 10 orbits). Note the new innermost disc (of high density and therefore white) which has formed from the dynamical infall of gas from the warp region. Image: University of Leicester
have put forward a new theory about why black holes become so hugely
massive – claiming some of them have no ‘table manners’, and tip their
‘food’ directly into their mouths, eating more than one course
from the UK and Australia investigated how some black holes grow so
fast that they are billions of times heavier than the sun.
team from the University of Leicester (UK) and Monash University in
Australia sought to establish how black holes got so big so fast. Their
research is due to be published in the Monthly Notices of the Royal Astronomical Society.
The research was funded by the UK Science and Technology Facilities Council.
Andrew King from the Department of Physics and Astronomy, University of
Leicester, said: “Almost every galaxy has an enormously massive black
hole in its centre. 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
hugely massive black holes were already full—grown when the universe
was very young, less than a tenth of its present age.”
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.”
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.
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.
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.”
The two biggest black holes ever discovered are each about ten billion times bigger than the Sun.
Source: University of Leicester