The Milky Way’s Central Black Hole Has Finally Been Revealed

The first images of the black hole in the center of the Milky Way have been published. They confirm many theories, but also raise their share of questions. Montreal researchers explain.

Posted at 7:00 am

Mathieu Perrault

Mathieu Perrault

Longer than expected

When the first image of a black hole was published three years ago, researchers at the Event Horizon Telescope (EHT) predicted that they would do the same six months later using Sagittarius A*, the image at the center of our galaxy, the Milky Way. “In the end, it was more complicated than expected,” explains Olivier Hernandez, director of the Montreal Planetarium, who is not involved with the EHT. “You have to understand that Sagittarius A* is 1,000 times less massive than that of the center of the M87 galaxy, imaged in 2019. The data synchronization was much more sensitive. No other images of the black hole have been made.

Einstein’s proof of relativity

in his monologue cable TV“We don’t want Sauer, we want the Ori! But for astrophysicists, what are the advantages of seeing a black hole? Can’t we just know its properties?” Hernandez says, “The images consist of measurements that allow us one of the strongest proofs of Einstein’s general relativity.” About a dozen texts were published at the same time as the image was published.One of the EHT principal investigators, Feryal Özel of the University of Arizona, began a conference call Thursday, noting that “the image closely matches Einstein’s theoretical predictions.” Studies have been published in Astrophysical Journal Letters.

Montreal team

Daryl Haggard of McGill University and doctoral student Hope Boyce worked on the areas around Arc A* with the EHT team. “These are stars located very far from the black hole, about 120 AU [plus loin que Pluton l’est du Soleil]M haggard. They lose gas due to stellar winds, and this gas falls into the black hole. When gas particles fall into the black hole, they interact with its magnetic field and emit light. By studying these particles more, we can better understand the magnetic field. »

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EHT takes its name from the black hole’s boundary, from which no light escapes, which is called “the horizon” in English event horizon. It is made up of eight networked ground-based telescopes. “We have to manage petabytes of data, millions of gigabytes,” notes Mr. Hernandez. According to the director of the planetarium, the photo is like taking a picture of a tennis ball on the moon from Earth.

the film Interstellar

in the movie InterstellarBy Christopher Nolan, we see an image of a black hole consisting of a ring cut in the middle by a rod. Olivier Hernandez expected the A* to be similar. “Among the subsequent questions, we will have to see why we see the black hole from the front and not the same inside. Interstellar, He said. Since Sagittarius A* is in the arm of the Milky Way, I would have expected to see it from the side. »

The ABCs of Black Holes

A black hole is an ancient star that has concentrated all its matter into a tiny point. These regions of space are so dense that not even light can escape. Only a few dozen black holes have been discovered, but there are billions of them in the universe.


Another fertile field of study would be the determination of the history of Arch A*. Did it exist at the beginning of the Milky Way or did it appear due to many catastrophic events? asks Mr. Hernandez. Since there is a supermassive black hole at the center of so many galaxies, it’s important to know. » Do we know about the M87? “It is a slightly different case because it is most likely caused by the interaction of spiral galaxies like ours. The merger caused the disappearance of interstellar gas, as seen in the Milky Way.”

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  • 44 million km
    arc diameter a*

    Source: NASA

    1.4 million km
    The diameter of our sun

    Source: NASA

  • 27000 light years
    The distance between Earth and Sagittarius A*

    Source: NASA

    4.3 million times
    The size of Sagittarius A* compared to our Sun

    Source: NASA

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