Supermassive Black Holes May Sterilize Nearby Planets

Shannon Hall | Scientific American

The center of any galaxy is a hazardous home. There, supernovae explosions shower nearby planets with x-rays, gamma rays and ultraviolet photons that obliterate any ozone layer present. Gamma-ray bursts hurtle even more damaging shock waves, blasting any biosphere into oblivion. Even encounters with nearby stars knock planets around, driving them out of their habitable zones. “We don’t expect life to be easy within the inner kiloparsec of the Milky Way,” says Abraham Loeb from the Harvard–Smithsonian Center for Astrophysics. But now we can add one more menace to the list that tops the rest: supermassive black holes.

Every large galaxy’s center hosts a supermassive black hole that is wont to throw wild tantrums in its youth. Although many astronomers have speculated these behemoths, called quasars when they are active, would likely wreak havoc on any nearby planets, no one had taken a quantitative look at those effects—until now. A new study, posted on the preprint server arXiv and submitted to Monthly Notices of the Royal Astronomical Society, provides the first calculations that show when, where and how planets are harmed by quasars. And the quota alone is surprisingly high.

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