WEBVTT FILE

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Narrator: In 2011, NASA's Swift satellite

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caught an X-ray outburst from a small galaxy

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3.8 billion light-years away. Within a couple of days. researchers realized

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they were witnessing the aftermath of a tidal disruption event--a star

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ripped apart by the monster black hole at the galaxy's center.

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Some of the stellar material fell toward the black hole, forming

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an accretion disk and a jet pointed in our direction.

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Erin Kara: Tidal disruption events offer us this rare view

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at the most common kind of supermassive black hole in the universe, these so-called

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dormant supermassive black holes. Ninety percent of black holes

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in the universe don't have a lot of hot material orbiting around

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them, they don't form these accretion disks, and so we can't observe

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them. Tidal disruption events, where the stellar debris

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causes the formation of a temporary accretion disk, offers

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us a way to probe this probe this population of supermassive black holes.

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Narrator: Swift monitored the outburst's progress and was joined

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by the European Space Agency's XMM-Newton observatory,

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and the Japanese Suzaku satellite. Recently,

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astronomers introduced a new analysis technique that for the first time allows

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them to peer deep into the gravitational well of a normally quiescent black hole.

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Called X-ray reverberation mapping, the

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method charts the region close to the black hole using light echoes from X-ray flashes,

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similar to the way sonar uses sound to map the ocean floor.

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Erin: X-ray reverberation mapping has been

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very successful at probing the accretion flow in

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well-established accretion disk structures, but had never been used

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to look at tidal disruption events. My collaborator at the

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University of Maryland and I were having lunch one day, and she says

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"Has anyone ever looked at tidal disruption events with X-ray

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reverberation mapping?" That night I stayed late at the office and

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just tried it out on this data from Swift J1644

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and much to my surprise the result was

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amazing and I could see that we were looking at

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the structure of the inner accretion flow around a normally

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dormant black hole for the first time. It's not like a normal accretion flow

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in an active galaxy that's a flat disk, this is

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something that is extremely puffy, very turbulent, and

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we are measuring flashes of X-ray emission deep within this

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newly formed accretion disk. Narrator: Stellar

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material streamed into the developing disk, churning it into a thick, chaotic

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whirlpool of X-ray emitting gas, funneling toward the central black hole.

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Deep inside this cavity, multiple X-ray flares

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erupted, providing a flash that echoed throughout the region.

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Erin: Previously, astronomers had thought that the X-ray emission

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is coming from far out in a jet, but we're finding

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with these observations is that the X-ray emission is coming from

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flares very close to the supermassive black hole.  And we can

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use these observations to probe properties of the black hole

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itself. For instance, we found that the mass of the black hole is something

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on the order of a million times the mass of the sun.

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Narrator: The first observations of X-ray reverberations from deep inside an

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accretion disk are providing new insights into a rarely observed class

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of black holes. They're also laying the groundwork for a better

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understanding of tidal disruption events, and the black holes they illuminate.

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[Music]

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[Music]

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[Beeping]

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[Beeping]

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[Beeping]