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The mystery of young stars near black holes solved

Staff writer |
The team of astrophysicists at the Universities of St Andrews and Edinburgh solved the mystery of how young stars can form within the strong gravity of black holes.

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The team made the discovery after developing computer simulations of giant clouds of gas being sucked into black holes. The new research may help scientists gain better understanding of the origin of stars and super massive black holes in our Galaxy and the Universe.

Until now, scientists have puzzled over how stars could form around a black hole, since molecular clouds - the normal birth places of stars - would be ripped apart by the black hole's immense gravitational pull. However, the new study by Professor Ian Bonnell (St Andrews) and Dr Ken Rice (Edinburgh) found that stars appear to form from an elliptical-shaped disc, the remnant of a giant gas cloud torn apart as it encounters a black hole.

The discovery of hundreds of young stars, of high masses and making oval-shaped orbits around a black hole three million times more massive than the sun, and at the centre of our Galaxy, is described as one of the most exciting recent discoveries in astrophysics.

The simulations, performed on the Scottish Universities Physics Alliance (SUPA) SGI Altix supercomputer, taking over a year of computer time, followed the evolution of two separate giant gas clouds up to 100,000 times the mass of the sun, as they fell towards the super massive black hole.

The simulations, stated the press release from Science & Technologies Facilities Council, show how the clouds are pulled apart by the immense gravitational pull of the black hole. The disrupted clouds form into spiral patterns as they orbit the black hole; the spiral patterns remove motion energy from gas that passes close to the black hole and transfers it to gas that passes further out. This allows part of the cloud to be captured by the black hole while the rest escapes.

In these conditions, only high mass stars are able to form and these stars inherit the eccentric orbits from the disc. These results match the two primary properties of the young stars in the centre of our Galaxy: their high mass and their eccentric orbits around the super massive black hole.

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