The telescope is named after the point of no return around a black hole. The team scored its first triumph in April 2019, when it presented a picture of the M87 black hole. In 2021, team members refined their data to reveal magnetic fields swirling around the black hole like a finely grooved rifle barrel pumping matter and energy into the void.
The data for Sagittarius A* were recorded during the same observing run in 2017 that produced the M87 image, but with more antennas — eight instead of seven — because the team was able to include a South Pole telescope that could not see M87.
Sagittarius A*, the black hole in the Milky Way galaxy, was a harder target. It is less than one-thousandth the mass and size of the M87 hole and, therefore, evolves a thousand times faster. The M87 black hole barely budges during a weeklong observing run, but Sagittarius A* changes its appearance as often as every five minutes, “burbling and gurgling” in the words of Dr. Özel.
Dr. Doeleman said, “The key thing is that, for M87, after a week of observing, it’s hardly budged.” He likened it to “the Buddha, just sitting there.”
By comparison, he said, the Sagittarius black hole was “whirling.” An orbit around it can take as little as four minutes or as long as a half-hour, depending on how it is spinning. “So over a night of observing. it’s changing while you’re collecting data,” he said. “You’re trying to trying to take a picture of something with the lens cap off and you just get this blurry mess.”
Dr. Doeleman’s new goal is to expand the network to include more antennas and gain enough coverage to produce a movie of the Sagittarius black hole. The challenge for black-hole cinema will be to separate what stays the same from what changes — to delineate the underlying structure of the black hole from the matter that is moving around in it.
The results could be spectacular and informative, said Janna Levin, a gravitational theorist at Barnard College of Columbia University, who was not part of the project. “I’m not bored with pictures of black holes yet,” she said.