Implications of These Findings
Analysis of this iron line has led to the conclusion that it comes from X-ray emission at the innermost areas of the accretion disc, just before matter disappears into the black hole. Because the amount of photon energy here far exceeds what could be expected according to the established models for accretion disks of supermassive black holes, it was clear to the team that something else was powering the iron atoms which glow so much in X-rays.
This required Wilm's team to come up with a new model for how the supermassive holes accrete matter, one which postulates that black holes actually spin.
The model they came up with seems to fit the XMM-Newton data well, and it also corresponds to a theory proposed over 25 years ago by astronomers Roger Blandford and Roman Znajek. Their Blandford-Znajek Theory suggests that rotational energy could escape from a black hole when it is in a strong magnetic field, which exerts a braking effect like the one implicated in Wilm's observations.
"We have probably seen this electric dynamo effect for the very first time. Energy is being extracted from the black hole's spin and is conveyed into the innermost parts of the accretion disc, making it hotter and brighter in X-rays," said Wilms.
None of this can be concluded with absolute certainty, however, and the Blandford-Znajek Theory itself was meant to apply only to quasars. The team's conclusion that a magnetodynamic process is involved is already provoking intense debate. "We recognize that more observations are required to confirm our work," said Wilms. "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."
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