A black hole is indeed at the heart of our galaxy. Sagittarius A has been immortalized, for the first time, in photos thanks to an international collaboration of astronomers. “A historic moment”, reacts Thursday, May 12 on franceinfo Eric Lagadec, astrophysicist at the Observatory of the Côte d’Azur and president of the French Society of Astronomy and Astrophysics. This snapshot comes three years after the first photo of a black hole, located in a distant galaxy M87. Sagittarius A has a mass of about four million Suns and is 27,000 light years from planet Earth.
franceinfo: Why is this a historic moment?
Eric Lagadec: I like to say we have two cribs. We have the solar system, which is the Sun and the Earth that revolves around it, and the other planets. And there is also the Milky Way, our galaxy. Since mankind, it was obviously easy to observe the Sun. But there since 1933, we know that there is something amazing in the center of the galaxy, that we had a source of radiation, then we realized that it was compact. The observations were able to show that there were stars which turned very quickly around it, that it was a black hole.
“Today marks the first time in human history that we’ve seen this black hole at the center of our galaxy. It’s a historic moment.”
Eric Lagadec, President of the French Society of Astronomy and Astrophysicsat franceinfo
What do we learn from this image?
We learn a lot of things. Many say the image is blurry, but it’s the sharpest ever in human history. What we see there is the equivalent of a beer bubble in Munich observed from New York. It really is something very, very small. It’s a pretty mind-blowing image. And what we learn is a fine confirmation of Einstein’s theory.
Black holes, have they long been one of the great mysteries of physics?
It’s something that makes you dream and it’s a little scary. It’s something quite complicated to approach and there, we see it.
“Today we learned, thanks to this image, that the black hole rotates, we were able to determine its size and especially see its orientation.”
Eric Lagadec, President of the French Society of Astronomy and Astrophysicsat franceinfo
It looks a bit like a donut, which is amazing is that we see it from above.
What is most complicated with this black hole story is that we are talking about something that, until now, we could not see and which weighs very heavily when we do not see it?
A black hole, a simple way to see it is: imagine, you take an object, you throw it, it will fall. If you take a rocket: beyond a certain speed, it will be able to escape from the Earth’s gravity field and you will be able to go into orbit. A black hole is so dense, it’s so heavy that to escape it would have to go faster than light. So we can’t escape it. When you enter the black hole, you can’t get out. In the photo, we still see something shiny. In the center is the shadow of the black hole and around it, which is orange in the image, is gas that is being absorbed by the black hole. Sometimes science goes beyond science fiction.