Here's What Happens When A Sleeping Black Hole Wakes Up To Devour A Star


Somewhere in the infinitely vast universe lies a sleeping giant that, like the creatures in mythology, has the power to devour and consume.

But this cosmic giant does not feed off living beings when it awakens. Instead, this supermassive black hole shreds matter and releases radiation.

And when an unlucky star wanders too close to the sleeping black hole, an ensuing feeding frenzy occurs -- a process called tidal disruption event -- which triggers spectacular cosmic fireworks, new research suggests.

Black Hole's Disk

Approximately 90 percent of the supermassive black holes in the known universe are dormant and are not actively devouring matter. Most of what astronomers know about supermassive black holes come from black holes that actively gather and consume matter, which are only 10 percent of the total population of supermassive black holes in the universe.

Now, the new study, which is the first research ever to make such detailed observations about dormant supermassive black holes, documented X-rays bouncing around the deep walls of a newly-formed accretion disk which is located near a once-sleeping supermassive black hole.

The accretion disk is a puffy cloud of pieces of star stuff that circles the black hole and waits for its turn to be gobbled up.

NASA's Swift satellite first saw the tidal disruption event and then triggered the XMM-Newton satellite of the European Space Agency as well as the Suzaku satellite of the Japanese Aerospace Exploration Agency to target the black hole for follow-up.

Using these data, NASA researchers discerned the activity and shape of the accretion disk near the supermassive black hole known as Swift J1644+57.

Astronomer Erin Kara says most tidal disruption events do not emit much in the high-energy X-ray band. However, there have been at least three known tidal disruption events that have done so, she says.

Kara says the tidal disruption event involving Swift J1644+57 is the first and only time such an event has been caught in its peak. Because of this, she says they have gathered "excellent data."

Clear Evidence

Scientists say the accretion disk's effect is somewhat akin to a reflective shield behind a lightbulb. The disk reflects, amplifies and focuses the radiation.

Before the study, astronomers had no evidence that the high-energy X-rays created from the black hole were part of the innermost regions of the accretion disk. They thought that the emission was from the jet pointed further away and not close to the central black hole.

Kara says the findings of the study show that scientists can see the reverberation at work very near the central black hole.

Details of the study are published in the journal Nature.

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