A star is torn

Black hole’s stellar feast caught by telescopes

Note to stars: When circling a black hole, exercise caution. Stray too close and something unfortunate might happen. See accompanying illustration for details.

If a star wanders too close to a black hole, it might be shredded. Some of that stellar material will be ejected into space (illustrated above). As the black hole sucks the material back up, it produces flares of the type recently observed around PS1-10jh, a supermassive gobbler sitting more than 2 billion light-years from Earth. NASA, S. Gezari/Johns Hopkins University and A. Rest/Space Telescope Science Institute

In spring 2010, NASA’s orbiting Galaxy Evolution Explorer and the ground-based Pan-STARRS telescope observed a suspicious brightening around a supermassive black hole parked more than 2 billion light-years from Earth. Over the next few months, the flare continued increasing in brightness — then it dimmed. Scientists now suggest that the light show was evidence of the black hole PS1-10jh shredding a star that wandered too close to the bruiser’s gravitational jaws.

An astronomical crime scene analysis presented online May 2 in Nature indicates that at the time of engulfment, the star was just a helium-rich core, the remainder of a former red giant. The black hole, a bulked-up behemoth weighing about 3 million solar masses, had probably already snacked on the star’s outer layers during a previous close encounter.

As it slowly ingested the star, the black hole spat some of the stellar material into space. The star-crumbs, visible in this computer simulation, followed elongated orbits that eventually dumped them back into the black hole, producing the observed, months-long flare.

Such disruption events are rare, thought to occur only once every 10,000 years per galaxy — and can help astronomers spot otherwise hidden black holes.

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