4 simple questions to understand why the discovery of a black hole in the center of our galaxy is a “historic moment”

“It’s a historic moment”excites Eric Lagadec, astrophysicist at the Côte d’Azur Observatory in Nice and president of the French Society of Astronomy and Astrophysics.

Sagittarius A *, as it is nicknamed, is the black hole located at the center of our galaxy, the Milky Way. Its existence was confirmed in the picture this Thursday by the international collaboration between the astronomers EHT.

This is the second image of a black hole; the first, the black hole M87 *, located in a (very) distant galaxy that was unveiled in 2019.

Did you not understand everything? Eric Lagadec is responsible for Good morning four simple questions.

What is a black hole?

A simple question, but not necessarily easy to answer. There are different ways to describe a black hole. The simplest thing is to imagine a stone: when I throw it, it falls. In order for a rocket to escape the gravity of the earth, it must basically exceed a certain speed. In a black hole, gravity is so strong that to get out of it, you have to go faster than the speed of light. If we go into a black hole, we can not get out. And there happens to be one at the center of our galaxy, which is 4 million times the mass of the Sun!

Is it dangerous for current and future space travel?

Often people are afraid of black holes, but you really should not, it’s just that you should not get too close to them because you would be swallowed! In short, we have two houses. First, the Earth orbits the Sun in our solar system. Then this solar system is located in the Milky Way, our galaxy. And in the middle there is a black hole! It is 27,000 light years from us, knowing that the nearest star to us is 4 light years away and we are very far from going there!

Moreover, the most accurate cartography of this galaxy with almost 2 billion stars will soon be revealed. This is the Gaia space mission, the announcement will take place on June 13 in Nice.

What changes this first image of the black hole in our galaxy?

It’s a historic moment, it’s the first time humans have seen the center of their galaxy! For the little anecdote, I was with interns from the observatory in the Côte d’Azur when the picture was revealed. Everyone was very touched, we had known we were going to see her for a few months. And then it’s a colossal work that gathers more than 300 people! A giant telescope that almost covers the earth’s surface allowed us to see these details.

Some say the image is blurry, but it’s the sharpest ever! If you will, it’s as if you from Munich could observe the bubble of a beer in New York! It is an overwhelming technological challenge. Symbolically, it is also very powerful to see scientists from all over the world working together in these complicated times.

What is left to understand about black holes?

Many things! There we learned that the black hole rotates, that it looks like a donut, and that it faces us. There are two theories: Einstein’s general theory of relativity, which explains what is large and massive, and quantum mechanics, which explains what is small. The black hole is massive AND small, so we must try to reconcile these two theories … and at the moment we do not know how to do it! The work to be done in Nice will help to understand these black holes better. One of the researchers from the Côte d’Azur Observatory, Olivier Minazzoli, proposed the new theory of intricate relativity. Maybe new observations of black holes will confirm that!

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