‘Wobbling’ black hole is the most extreme ever seen

A “wobbling” black hole is the most extreme example ever seen, scientists have said.

Scientists have watched as two colliding black holes became locked in a twisting motion. It is caused by an effect called precession, which made the twisting 10 billion times faster than has been seen before.

The black hole system was first spotted with gravitational waves, two years ago. It was detected by the Advanced LIGO and Virgo detectors in early 2020.

One of them is 40 times bigger than our Sun and is probably the fastest spinning black hole that has ever been founding that way. It is pulling at the fabric of time and space so much that it is causing the whole orbit of the two black holes to wobble, the scientists have found.

“So far most black holes we’ve found with gravitational waves have been spinning fairly slowly,” said Dr Charlie Hoy, a researcher at Cardiff University during the study, and now at the University of Portsmouth.

“The larger black hole in this binary, which was about 40 times more massive than the Sun, was spinning almost as fast as physically possible. Our current models of how binaries form suggest this one was extremely rare, maybe a one in a thousand event. Or it could be a sign that our models need to change.”

It is the first time that phenomenon has been seen in black holes like this, after years of theory, the researchers who found it said.

“We’ve always thought that binary black holes can do this,” said Professor Mark Hannam of Cardiff University’s Gravity Exploration Institute.

“We have been hoping to spot an example ever since the first gravitational wave detections. We had to wait for five years and over 80 separate detections, but finally we have one!”

Precession is part of Einstein’s theory of general relativity, and so its existence has been known for some time. But seeing it in black holes means that it can be seen in the most extreme possible circumstances.

Previously, the best example of such precessions two orbiting neutron stars, where the orbit precessed every 75 years. In the new example, it happens every few seconds.

The findings are reported in a new paper, ‘General-relativistic precession in a black-hole binary’, published in Nature today.