Black hole is wobbling and rotating, scientists say

A black hole 55 million lightyears away is wobbling and rotating in interesting and helpful ways, scientists have said.

The object known as M87* has undergone major changes over time, astronomers have found after detailed research.

The galaxy called M87 became famous last year, when the black hole at its centre became the first ever to be shown in an image taken by humanity. That image helped reveal the nature of the black hole and the ring of hot plasma that surrounded it – but does not appear to have given the full picture.

Those images captured the black hole by looking at the shadow of the black hole over a relatively limited time period: just a one-week window. That is too short to see many of the changes that would happen to the object, scientists say.

Looking at observations taken over a longer period – between 2009 and 2013 – researchers were able to test how the black hole’s shadow might have changed over time. Because they had much less detailed information than during the 2019 observations, the researchers took the data and ran it through statistic models to understand how the appearance of M87* might have changed over time.

They found that the black hole behaved as expected: the crescent shape seen in the original image appears to stick around over a period of several years, the researchers said.

That helps confirm the understanding about the nature of the black hole and its shadow that they came to in the wake of the first image.

But they were surprised to discover that while the existence and diameter of the ring stays constant, it wobbles over time. That is thought to happen as gas falls onto the black hole and becomes turbulent unde the heat and extreme conditions at the edge of the object.

"Because the flow of matter is turbulent, the crescent appears to wobble with time," said Maciek Wielgus, an astronomer at Center for Astrophysics | Harvard & Smithsonian and lead author on the paper.

"Actually, we see quite a lot of variation there, and not all theoretical models of accretion allow for so much wobbling. What it means is that we can start ruling out some of the models based on the observed source dynamics."

Scientists now hope they can keep watching the object – using the extra detail they are able to view it with – to get a better look at how black holes might change over time.

“Monitoring M87* with an expanded EHT array will provide new images and much richer data sets to study the turbulent dynamics,” said Geoffrey Bower, a project scientist on the Event Horizon Telescope, which took the images.

"We are already working on analyzing the data from 2018 observations, obtained with an additional telescope located in Greenland. In 2021 we are planning observations with two more sites, providing extraordinary imaging quality. This is a really exciting time to study black holes!"