Black hole news: ‘Wobbling shadow’ of M87* seen for the first time

Last year, researchers using the Event Horizon Telescope (EHT) – an international collaboration between astronomers and their telescopes – revealed the first ever image of a black hole, M87*. M87* is a black hole some 55 million light years away from Earth and has the mass equal to six and a half billion Suns.

The black hole is continuing to throw up surprises, and now astronomers have revealed the “wobbling” crescent of M87*.

Using archival data from 2009 to 2013, scientists involved in the EHT project found the glowing ring around the black hole is wobbling and is inconsistent, changing rapidly over time.

According to the research, the wobbling outer ring is caused by “turbulence” in the accretion disk.

An accretion disk is a glowing halo surrounding a black hole which produce enormous amounts of heat and light.

They are created when the material being sucked in by a black hole generates huge friction, which manifests itself in tremendous heat and light energy.

However, by spotting the wobbling nature of the light, scientists from the EHT “can get a glimpse of the dynamical structure of the accretion flow so close to the black hole’s event horizon, in extreme gravity conditions”.

Maciek Wielgus, an astronomer at Center for Astrophysics at Harvard & Smithsonian, Black Hole Initiative Fellow, and lead author of the new paper, said: “Last year we saw an image of the shadow of a black hole, consisting of a bright crescent formed by hot plasma swirling around M87*, and a dark central part, where we expect the event horizon of the black hole to.

“But those results were based only on observations performed throughout a one-week window in April 2017, which is far too short to see a lot of changes.

“Because the flow of matter is turbulent, the crescent appears to wobble with time.

“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.”

Shep Doeleman, the founding director of EHT, added: “These early-EHT experiments provide us with a treasure trove of long-term observations that the current EHT, even with its remarkable imaging capability, cannot match.

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“When we first measured the size of M87 in 2009, we couldn’t have foreseen that it would give us the first glimpse of black hole dynamics.

“If you want to see a black hole evolve over a decade, there is no substitute for having a decade of data.”

EHT project scientist Geoffrey Bower added: “Monitoring M87* with an expanded EHT array will provide new images and much richer data sets to study the turbulent dynamics.

“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!”

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