First image of Milky Way’s black hole produced

A global collaboration of telescopes, including two observatories on Mauna Kea, helped produce the first image of the black hole at the center of the Milky Way galaxy.

Eight radio telescopes in different parts of the world — all part of a global research team known as the Event Horizon Telescope Collaboration — teamed up to form an “Earth-sized” virtual telescope and create an image of the supermassive black hole known as Sagitta­rius A* (the asterisk denotes a star).

The Hawaii-based James Clerk Maxwell Telescope and the Submillimeter Array were involved in the 2017 observations that led to the creation of the image, which was revealed Thursday by EHT.

The unveiling of the image follows the EHT’s reveal of Powehi, the first black hole to ever be photographed, in 2019. Powehi is more than 1,000 times bigger than the Milky Way black hole and is found farther from Earth, in a distant galaxy called Messier 87.

“Powehi — that was cool. I mean, who doesn’t want an image of a black hole?” said Harriet Parsons, JCMT head of operations. “But this time it’s cool because it’s ours.”

The Milky Way black hole is near the border of the Sagittarius and Scorpius constellations and, while much smaller than Powehi, is still 4 million times more massive than our sun.

Most galaxies are thought to have giant black holes at their center, but images of them are difficult to produce.

“Pictures of black holes are the hardest thing to think about,” said astronomer Andrea Ghez of the University of California, Los Angeles. Ghez earned a Nobel Prize for the discovery of the Milky Way’s black hole in the 1990s and is a longtime user of the W.M. Keck Observatory on Mauna Kea.

The new image, which shows a ringlike formation of glowing gas around the black hole, was particularly difficult to capture and process compared with Powehi because of its smaller size.

“The gas in the vicinity of the black holes moves at the same speed — nearly as fast as light — around both Sgr A* and Powehi,” said EHT scientist Chi-kwan Chan, from Steward Observatory and Department of Astronomy and the Data Science Institute of the University of Arizona, in a statement. “But where gas takes days to weeks to orbit the larger Powehi, in the much smaller Sgr A* it completes an orbit in mere minutes. This means the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration was observing it — a bit like trying to take a clear picture of a puppy quickly chasing its tail.”

The image provides new data for physicists studying black holes.

“We were stunned by how well the size of the ring agreed with predictions from (Albert) Einstein’s Theory of General Relativity,” said EHT Project Scientist Geoffrey Bower, of Taiwan’s Academia Sinica Institute of Astronomy and Astrophysics. “These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy, and offer new insights on how these giant black holes interact with their surroundings.”

Getting images of black holes requires the coordination of all the involved telescopes and researchers involved, Parsons said. More than 300 researchers from 80 institutions that are part of the EHT Collaboration helped synchronize all the telescopes to collect the data that, for five years, was analyzed to create the image of the black hole.

At JCMT it took the work of telescope operators, administrative employees, scientists and others to produce Hawaii’s share of that data.

“You can tell this is such a big logistical undertaking. … It really does take everyone at the observatory to get this science out,” Parsons said.

The next step for astronomers is to create “movies” of one of or both of the black holes to show how they change over time. Higher resolutions of the black holes are also possible now that 11 telescopes are part of the EHT Collaboration, Parsons said.

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The Associated Press contributed to this story.