A team of scientists that included researchers from Harvard and MIT on Thursday unveiled the first-ever picture of the supermassive black hole at the center of the Milky Way galaxy.
The Event Horizon Telescope (EHT) team — which includes researchers from the Center for Astrophysics | Harvard & Smithsonian (CfA) and MIT’s Haystack Observatory — used observations from a worldwide network of radio telescopes to look at Sagittarius A*, or Sgr A*, a black hole with a mass 4 million times that of the sun.
The black hole, about 27,000 light-years away, had never before been directly observed, though the way stars orbited around it had led scientists to believe it was there.
Scientists said the observation had matched up with what they were expecting. Michael Johnson, a CfA astrophysicist, said at a news conference in Washington, D.C., that previous research had yielded predictions for the black hole with “no wiggle room. They gave a very precise measurement of exactly what we should expect. And so I remember seeing this and just kind of walking around in a daze,” he said. He said he was thinking, “Look at that image, and that hole in the center has 4 million solar masses. That’s incredible!”
The discovery was announced in multiple news conferences around the world. The results were published in a special issue of The Astrophysical Journal Letters,
At the news conference at the National Press Club in Washington, Vincent Fish, the operations data manager and scheduler for the EHT and a research scientist at MIT’s Haystack Observatory, said, ”Our collaboration’s remarkable images of Sgr A* [pronounced ‘Sadge A star’] and our scientific conclusions were a combined effort that involved not just the handful of us on stages around the world today, but more than 300 people all working together united by our fascination with black holes.”
“Our results built upon decades of studies by other groups that established that Sgr A* contains a dark massive object, characterized its properties and obtained accurate measurements of its mass and distance,” he said, noting the work of Andrea Ghez and Reinhard Genzel and their teams. Ghez and Genzel won Nobel prizes in 2020 for developing evidence of the black hole at the center of our galaxy.
“I’ve been with the project now for almost 15 years. It’s been exciting watching the project evolve, watching the collaboration grow,” said Fish. “The data get better and better. What seemed like it was going to be an impossible task is now -- well, it’s still hard, but it’s doable.”
The picture shows a ring of light surrounding a black hole. Paul Tiede, a postdoctoral researcher at CfA, said, “Around this black hole as matter starts to fall in, it heats up. ... We’re seeing this really hot gas give off light,” he said.
Black holes are thought to reside at the center of most galaxies, but scientists don’t know why, Tiede said in a telephone interview. “It’s very much an open question what formed these things and how they’re related to the central galaxy,” he said.
The project used eight radio telescopes around the world to act as one virtual telescope. Hard drives full of massive amounts of data were shipped, half to Haystack, which is located off Route 40 in Westford, Mass., and half to the Max Planck Institute for Radio Astronomy in Germany for processing by supercomputers, MIT said in a statement. Researchers then weeded out noise in the data and translated it into an image.
“Through the power of computational imaging, the EHT team overcame seemingly impossible hurdles to capture the first image of the beastly black hole at the heart of our galaxy,” Katherine Bouman, an assistant professor at Caltech, said at the news conference.
Ferya Ozel, a professor of astronomy and physics and associate dean of research at University of Arizona, said at the news conference, “I’m one of those people who have thought about Sgr A* for a long time. Twenty-two years ago was my first paper on it when I was a graduate student. So I feel like I had this remote friend that I kind of had an idea in my, in my, head about what it looked like - we were online chatting - and then I was, like, ‘Oh, you’re real!’ meeting in person. So it’s very nice.”
Duncan Brown, a professor of physics at Syracuse University who was not involved in the research, said the EHT scientists had faced an “incredibly challenging” problem in producing a “snapshot” of the black hole, since hot gas is swirling around it incredibly fast. Producing the image was “a tour de force of radio astronomy and computational astronomy,” he said.
In 2019, the EHT team released the first-ever picture of any black hole. The picture was of Messier 87, a black hole much larger and much farther away than Sgr A*.
Martin Finucane can be reached at email@example.com.