Dormant black hole wakes up to devour passing star at theoretically impossible speed

'This is the first and only such event that has been caught at its peak'

A dormant supermassive black hole woke up and devoured a star that had wandered too close, astronomers have discovered.

About 90 per cent of the black holes in the universe are not actively consuming matter on a significant scale, but if something like a star gets too close the results are spectacular.

An artist’s rendering of the encounter shows the star drifting through space, then being pulled apart by the black hole, creating a disk of material around it and sending out X-rays that were picked up by a Nasa satellite.

According to the research, the black hole consumed the star so quickly that it briefly exceeded the so-called Eddington Limit – the theoretical maximum “speed limit” that defines how fast a black hole can consume matter.

“Most tidal disruption events [stars being eaten by black holes] don’t emit much in the high-energy X-ray band,” said Dr Erin Kara, of Maryland University, who led the study.

“But there have been at least three known events that have, and this is the first and only such event that has been caught at its peak.

“Nasa’s Swift satellite saw it first and triggered the European Space Agency’s XMM-Newton satellite and the Japanese Aerospace Exploration Agency and NASA’s Suzaku satellite to target it for follow-up.

“So we have excellent data. We’re lucky that the one event we have is showing us all these exciting new things.”

Dr Kara said it was surprising that X-rays had originated from the disk of material so close to the black hole.

“Before this result, there was no clear evidence that we were seeing into the innermost regions of the accretion disk,” she said.

“This new study shows us that … we can see this reverberation at work very close to the central black hole.”

The discovery could help astronomers to understand how supermassive black holes grow to as much as several million times the mass of the sun.

“The meaning of this extends far beyond the studies of tidal disruption events,” said Dr Lixin Dai, a co-author on the study.

“It can help us understand how the biggest black holes in the universe formed and co-evolved with their host galaxies.”