WASHINGTON– The world’s first image of the chaotic supermassive black hole at the center of our galaxy, the Milky Way, depicts not a voracious cosmic destroyer, but what astronomers Thursday called a “gentle giant” on a near-starvation diet.
Astronomers believe that almost all galaxies, including our own, have these giant black holes at their bustling, crowded centers, where light and matter can’t escape, making it extremely difficult to get pictures of them. . Light is bent and twisted by gravity as it is sucked into the abyss with superheated gas and dust.
The colorized image unveiled on Thursday comes from an international consortium behind the Event Horizon Telescope, a collection of eight synchronized radio telescopes around the world. Getting a good picture was a challenge; previous efforts have found the black hole too jittery.
“It was gurgling and gurgling as we watched it,” said Feryal Ozel of the University of Arizona.
She described it as a “gentle giant” while announcing the breakthrough along with other astronomers involved in the project. The image also confirms Albert Einstein’s general theory of relativity: the black hole is precisely the size that Einstein’s equations dictate. That’s about the size of Mercury’s orbit around our sun.
Black holes gobble up galactic matter, but Ozel said this one “eats very little.” That’s the equivalent of a person eating a single grain of rice for millions of years, another astronomer said.
“Pictures of black holes are the hardest thing to think about,” said astronomer Andrea Ghez of the University of California, Los Angeles. She was not part of the telescope team but won a Nobel Prize for the discovery of the Milky Way black hole in the 1990s.
She said the image of “my baby” is exactly what it should be – an eerie red-orange ring with total blackness in the middle.
Scientists expected the Milky Way’s black hole to be more violent, especially since the only other image from another galaxy shows a much larger and more active black hole.
“It’s the cowardly lion of black holes,” said project scientist Geoffrey C. Bower of Taiwan’s Institute of Astronomy and Astrophysics Academia Sinica.
Because the black hole is “on a starvation diet,” so little matter falls into the center, allowing astronomers to look deeper, Bower said.
The Milky Way’s black hole is called Sagittarius A (asterisk), near the boundary of the constellations Sagittarius and Scorpio. It is 4 million times more massive than our sun. Bower said it’s probably more typical of what’s at the center of most galaxies, “just sitting there doing very little.”
It’s incredibly hot, billions of degrees, Ozel said.
The same group of telescopes released the first black hole image in 2019. The image was from a galaxy 53 million light-years away, which is 1,500 times larger than our own galaxy. The Milky Way’s black hole is much closer, about 27,000 light-years away. A light year is 5.9 trillion miles (9.5 trillion kilometers).
To get the image, the eight telescopes had to coordinate so closely “in a process similar to everyone shaking hands with everyone in the room,” said Massachusetts Institute of Technology astronomer Vincent Fish.
Astronomers worked with data collected in 2017 to get the new images. The next step is a movie about one of those two black holes, maybe both, Fish said.
The project cost nearly $60 million, including $28 million from the US National Science Foundation.
Although quieter than expected, the center of the Milky Way is an important place to study, Ghez said.
It’s “like an urban downtown, everything is more extreme. It’s crowded. Things move fast,” Ghez said in an interview. “We live in the suburbs (in a spiral arm of the galaxy). Things are quiet here.”
Follow Seth Borenstein on Twitter at @borenbears
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