European astronomers conclude that black holes release energy
A European-led team of astronomers using the European Space Agency (ESA) XMM Newton X-ray observatory has produced evidence indicating that black holes release as well as consume energy. Detailed analysis of the matter swirling around the entrance to black holes has produced surprising new results which seem to correspond to a theory proposed over a quarter of a century ago that energy could escape from a black hole when it is in a strong magnetic field. Black holes can contain the mass of a billion suns compressed into the space the size of the solar system. Their gravitational fields are so intense that nothing, not even light, can escape their attraction. Before being swallowed, the gas and dust takes the form of a rotating 'accretion disc.' This disc of material accumulates around the black hole, where friction causes it to glow strongly in X-rays. In June 2000, the astronomers focused their research on the spiral galaxy MCG-6-30-15, situated 100 million light years away. Dr Jörn Wilms from the Astronomy and Astrophysics Institute at Eberhard-Karls University in Tuebingen, Germany, led the team of astronomers. The data obtained has led them to conclude that energy is not only going in to the galaxy's black hole, but is also escaping. Co-investigator Dr Christopher Reynolds at the University of Maryland said: 'Never before have we seen energy extracted from black holes. We always see energy going in, not out.' 'With XMM-Newton's great collecting power we have discovered something never observed before in a black hole,' explains Dr Wilms. 'The observatory's EPIC cameras have obtained a spectrum, a kind of chemical fingerprint of the elements present. This graph displays an unusually broad 'line' for the X-ray emission corresponding to the presence of iron in the accretion disc. This broad line had first been detected in 1995 with the ASCA satellite but we had never seen it so clearly. And, it is full of surprising features.' Analysis of this iron line led the team to deduce that it arises from X-ray emission stemming from the innermost areas of the accretion disc, just before matter disappears into the black hole. But the energy measured by XMM Newton far exceeds what could be expected from established models of black holes., leading them to conclude that a magnetodynamic process is leading the black hole to give out as well as absorb energy. The team's conclusion is already provoking intense debate. 'We recognise that more observations are required to confirm our work,' Dr Wilms said. 'But there is no disputing the presence of this exceptionally strong iron line in the spectrum of MCG-6-30-15. It is extremely puzzling and an explanation must be found.' The XMM Newton observatory, ESA's second 'cornerstone' mission, was launched in December 1999. It carries three advanced X-ray telescopes with an unprecedented X-ray collecting power. Its instruments were provided by large European consortia, including American institutes. NASA helped fund the mission development and supports guest observatory time.