Seeing the black hole at the center of our galaxy is just the beginning, says researcher Katie Bouman

Eva Deschamps / May 13, 2022

At just 33 years old, Katie Bouman has already been involved in two huge scientific feats: after revealing the first image of a black hole in 2019, she again played a key role in the never-before-seen image revealed Thursday of the black hole at the center of our own galaxy, called Sagittarius A.
A few years ago, she had become a worldwide celebrity, invited even to the American Congress. Today, she is a specialist in computational imaging at Caltech University in California and is still part of the huge international collaboration that made this feat possible, the Event Horizon Telescope (EHT).
His working group is in charge of reconstructing an accurate picture, from the gigantic mass of data gathered by telescopes around the world.
AFP spoke with her just after the new image was revealed.
The first image was spectacular, because it was the first time we could see a black hole. But I think the Holy Grail for the Event Horizon Telescope has always been to get an image of Sagittarius A.
Because we have much more information about what Sgr A is supposed to look like, via other scientific observations (for example the rotation of stars around it, editor's note). So being able to see an image of it makes it much easier for us to compare whether it matches what we expected from our previous observations and theories.
That's why I think that even though this is the second image we show, it's actually much more exciting, because we can use it to further test our understanding of gravity.
We observed both in the same week, in 2017. But it took us much longer to create the image of Sgr A*, than for M87*.
Many things make it much more difficult to get an image of Sgr A*. First, we observe the black hole through the plane of our galaxy. This means that the gas in the galaxy hinders the image. A bit like looking through a frosted window, for example in a shower.
This is one of the challenges. But the most difficult one we had to face is the fact that the black hole is evolving very fast. The gas around M87* and Sgr A* is moving at roughly the same speed. But while it takes days or even weeks to go around M87*, for Sgr A*, it evolves every minute.
They break with what we know on Earth. Light can't even escape them, and they distort the space-time around them. They are this mysterious thing, and I think they capture our imagination.
What's cooler than working on black holes? And the fact that you can take an image of it, of something that you shouldn't be able to see... I think it's fascinating.
I think this is just the beginning. Now that we have these extreme gravity labs, we can improve our instruments and algorithms, so we can see more, and do more science.
We made a first attempt to get a movie, and we've made a lot of progress, but we're not yet at the point where we can say, this is what Sgr A* looks like minute by minute. So we're going to try to add more telescopes around the world, collect more data, so that we can show something that we're sure of.
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