In April 2019, the Event Horizon Telescope (EHT) Collaboration reported the first-ever event-horizon-scale images of a black hole, resolving the central black hole — known as M87* — in the giant elliptical galaxy Messier 87 (M 87). In a new paper, astronomers present new images of M87* from data collected by the Atacama Large Millimeter/submillimeter Array (ALMA), the Greenland Telescope and several other instruments within the EHT. These new images show the shadow of M87* as predicted by general relativity. Excitingly, the brightness peak of the ring has shifted by about 30º compared to the first images, which is consistent with theoretical understanding of variability from turbulent material around black holes.
“A fundamental requirement of science is to be able to reproduce results,” said Dr. Keiichi Asada, an astronomer at Academia Sinica Institute for Astronomy and Astrophysics.
“Confirmation of the ring in a completely new data set is a huge milestone for our collaboration and a strong indication that we are looking at a black hole shadow and the material orbiting around it.”
The image of M87* taken in 2018 is remarkably similar to what the astronomers saw in 2017.
They see a bright ring of the same size, with a dark central region and one side of the ring brighter than the other.
The mass and distance of M87* will not appreciably increase throughout a human lifetime, so general relativity predicts that the ring diameter should stay the same from year to year.
The stability of the measured diameter in the images from 2017 to 2018 robustly supports the conclusion that M87* is well described by general relativity.
“One of the remarkable properties of a black hole is that its radius is strongly dependent on only one quantity: its mass,” said Dr. Nitika Yadlapalli Yurk, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory.
“Since M87* is not accreting material — which would increase its mass — at a rapid rate, general…
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