The first image of the Milky Way's supermassive black hole was revealed Thursday, providing the first direct visual evidence of "the gentle giant" that lies at the center of our galaxy.
The photo, which shows an oval-shaped void surrounded by a bright ring of glowing gas, is only the second image captured of a black hole, and it is the first to provide a detailed glimpse of the immense feature, dubbed Sagittarius A*, at the Milky Way's core.
“For decades, astronomers have wondered what lies at the heart of our galaxy, pulling stars into tight orbits through its immense gravity,” Michael Johnson, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, said in a statement.
Now, scientists have the first direct image that confirms Sagittarius A* is indeed a black hole.
The research was conducted by an international team of astronomers known as the Event Horizon Telescope, which is made up of more than 300 scientists from 80 different institutions around the world.
The findings were published Thursday in a special issue of The Astrophysical Journal Letters.
Sagittarius A* is about 27,000 light-years away and is 4 million times more massive than the sun. It's thought that almost all galaxies contain a black hole at their center, but since these behemoths do not emit light, it is challenging for astronomers to get direct views of them.
Sagittarius A* is completely dark, but the photo captured a glowing ring around a cloaked center — what astronomers identified as the black hole's telltale shadow, said Feryal Özel, a professor of astronomy and astrophysics at the University of Arizona and a member of the research team.
The observations show how black holes "eat," swallowing nearby gas and bending light with its powerful gravity, she added.
"Light escaping from the hot gas swirling around the black hole appears to us as the bright ring," Özel said. "Light that is too close to the black hole — close enough to be swallowed by it — eventually crosses its horizon and leaves behind just the dark void in the center."
The image was produced using eight radio telescopes around the world that operated as one giant observatory. The technique involved linking "pairs of telescopes that are very far apart into the equivalent of a planet-sized telescope," said Vincent Fish, a research scientist at the MIT Haystack Observatory in Massachusetts.
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The network of radio telescopes allowed astronomers to observe Sagittarius A* from different distances and angles, providing key details that could be pieced together to form a cohesive picture. The process is similar to hearing a song played on a piano with bunch of missing keys, said Katie Bouman, an assistant professor of computing and mathematical sciences at the California Institute of Technology.
"Since we don't know when the missing keys should be hit, there's an endless number of possible tunes that could be playing," she said. "Nonetheless, with enough functioning keys, our brains can often fill in the gaps to recognize the song correctly."
The Event Horizon Telescope observations could help scientists learn how black holes gobble light and matter in their vicinity, which could help researchers understand how supermassive black holes form and grow to such monstrous sizes.
In 2019, the same Event Horizon Telescope team released the first image of a black hole — one named M87* that is lies at the center of the Messier 87 galaxy, more than 53 million light-years away.
The researchers said the two black holes look similar, even though Sagittarius A* is more than 1,000 times smaller and less massive than the black hole at Messier 87's core.
Bouman called it "amazing" to finally be able to see what lies at the heart of our galaxy.
"It's just super exciting," she said. "I mean, what's more cool than seeing the black hole at the center of our own Milky Way?"