URBANA, Ill. (WCIA) — A team of researchers from the University of Illinois were among those who contributed to the latest discovery that has the astronomical world buzzing: a photograph of the supermassive black hole at the center of the Milky Way Galaxy.
This is not the first photo of a black hole; one was released in 2019. But that photo shows the black hole located at the center of Messier 87, a galaxy located tens of millions of light years away from Earth. The most recent photo shows Sagittarius A, located at the center of our own galaxy.
Black holes themselves cannot be seen, but researchers said that they are surrounded by a “glowing ring” of hot gas that is billions of degrees in temperature. The ring surrounds a dark central region called a shadow, and that is the telltale signature of a black hole.
Astronomers had long known that something was at the center of the Milky Way after watching stars orbit an invisible, compact and very massive object. They suspected the object was a black hole, and this new image provides the first direct visual evidence.
The image was captured in 2017 by the Event Horizon’s Telescope, a network of telescopes around the world. U of I astronomy and physics professor Charles Gammie contributed to the astrophysical modeling portion of the research.
“It’s very exciting,” Gammie said. “It’s clearly getting a lot of attention, which is great not so much from the standpoint of getting one’s own work recognized, because we’ve had plenty of recognition in the community. But what’s really exciting is to have the public share in this.”
EHT was also responsible for imaging Messier 87’s black hole. However, imaging Sagittarius A was much more difficult because the gas surrounding Sagittarius A is orbiting much closer than the gas surrounding Messier 87’s black hole. It takes only a matter of minutes for gas to orbit Sagittarius A while it takes days to weeks for gas to orbit Messier 87’s black hole, which means the brightness and pattern of Sagittarius’s gas is changing much more rapidly.
Researchers had to develop new tools to account for this gas movement.
“My group and I have spent more than a decade developing key techniques into building models of Sgr A star,” Gammie said. “The models do a terrific job of explaining nearly all the data. But we uncovered a mystery: Sgr A star is much quieter than we expected.”
Video of Gammie discussing his team’s contribution to the EHT project can be found on YouTube, as can video of the model building.
Progress and expansion of the EHT project is continuing and scientists hope these improvements will allow them to photograph and observe more black holes in the future.