For the first time, astronomers from the University of Michigan and University of Maryland have mapped the flow of gas near a huge black hole, Swift J1644+57. This one suddenly woke up from a "dormant state" to destroy and swallow a star nearby.
Most of the black holes in the universe are dormant. "But sometimes a star wanders too close to a dormant black hole and the ensuing feeding frenzy, known as a tidal disruption event, sets off spectacular fireworks," according to scientists. That is what happened outside Swift J1644+57.
There were X-rays that bounced from within the walls of its accretion disk, following an event of a tidal disruption, and they were documented by astronomers.
The accretion disk is composed of giant clouds of shredded stars going around the black hole. The star will soon be consumed.
The high energy X-rays from inside the disk seemed to contradict the astronomers' belief that much of the emission emanated from a narrow jet of particles accelerate to touch the speed of light.
"Never before have we been able to see strong gravity effects from a dormant black hole," said Erin Kara, a Hubble postdoctoral fellow at the University of Maryland, and lead author of the study.
Swift J1644+57 is just one of three tidal disruptions that created high energy X-rays, and the sole event that was captured during the peak of the emission. Researchers may devise some stable measurements of the black hole spin.
The mass of the supermassive black hole is a million times more than that of the sun.
While destruction happened 3.9 billion years ago, the X-rays that were generated during the event hit the earth only in 2011. NASA's Swift Satellite detected the rays, and flares near the million-solar-mass black hole created the X-rays bouncing off the accretion disk. The structure was disclosed.
When the X-rays stoked some iron ions in the gas floating near the hole, it was found that the disk was composed of stellar debris that dropped towards the black hole.
"While we don't yet understand what causes X-ray flares near the black hole, we know that when one occurs we can detect its echo a couple of minutes later, once the light has reached and illuminated parts of the flow. This technique, called X-ray reverberation mapping, has been previously used to explore stable discs around black holes, but this is the first time we've applied it to a newly formed disc produced by a tidal disruption," University of Maryland researcher and lead author Erin Kara said in a NASA statement.
Such dormant black holes were agile when the universe was young. They had a large role to play in the evolution of galaxies.
The study was published in journal Nature.
