LIFE on Earth could once have been seared by the galaxy鈥檚 heart.
Some black holes are ringed by discs of glowing hot matter, but the one at the Milky Way鈥檚 centre shines only at radio wavelengths. There is evidence that it used to be more active, though, so Xian Chen and Pau Amaro-Seoane from the Max Planck Institute for Gravitational Physics in Potsdam, Germany, modelled its past behaviour. They found its X-ray output, as seen from Earth, could once have matched the sun鈥檚.
If so, early Earth could have been bathed in X-rays as if hit by a modern solar flare, but for much longer periods. This would have disturbed the ancient ozone layer and ionosphere, perhaps harming early life ().
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This article appeared in print under the headline 鈥淏right black hole blasted early Earth鈥�
