This image was published just this past week and revealed at a press conference.
About 27,000 light-years away sits a massive astrophysical object, some four million times the mass of our sun, surrounded by swirling super-hot gasses. The existence of this supermassive blackhole called Sagittarius A* has been theorized for decades as astronomers observed nearby stars orbiting something invisible, compact and very massive at the center of the Milky Way. But they have never seen what it is – until now.
The effort shows the need for global science cooperation to undertake a project of this magnitude.
The announcement represents the work of more that 300 researchers at 80 institutions, including the Smithsonian Astrophysical Observatory, across the globe who turned a network of telescopes into a planet-sized observatory known as the Event Horizon Telescope (EHT).
“Our telescope has to be almost as big as the Earth,” said Vincent Fish, an astronomer at the MIT Haystack Observatory and EHT collaborator, at the event. To do that, the team connected more than half a dozen telescopes around the globe using a technique called interferometry. “By correlating their signals and studying the resulting data, we can reconstruct images of the source. The more telescopes the better.”
Note that this is not the first image we have obtained of a black hole. It is the first one of the one in our own galaxy.
EHT scientists used a similar technique to create the first images of a black hole M87*’s event horizon, released in 2019. But the supermassive black hole at the center of the Milky Way is quite different; it’s much smaller, and the gas swirls around it far more rapidly. Capturing the image was “a bit like trying to take a clear picture of a puppy quickly chasing its tail,” said EHT scientist Chi-kwan Chan from the University of Arizona.
The images of Sagittarius A* along with previous images of the black hole M87* give scientists more data to study black holes. M87* is much farther away from Earth and more than 1,000 times bigger than Sagittarius A*, which gives scientists the opportunities to compare the two.
This video compares the two black holes.
We have been able to learn so many things about the universe that it is easy to become blase and take it all for granted. When I step back a bit, I find it incredible that we who live in a tiny speck in a vast cosmos have been able to develop techniques that enable us to see into regions of space that our ancestors could not even dream about.