International collaboration of astronomers EHT and the European Southern Laboratory (ESO) on Thursday demonstrated the presence of a large black hole Sagittarius A * in the heart of our Milky Way. This is three years after the first photograph of a black hole in a distant galaxy.
I can give you a picture of Black hole Sgr A * At the center of the galaxy, “EHT project manager Huib Jan Van Langevelde announced at a press conference in Korching, Germany, to applaud.
It was a strange ballet of stars in the center of the Milky Way, the first to realize that it could have been a black hole: Andrea Guess and Reinhard Jensel Nobel Prize in Physics 2020 They “discovered a very large object in the center of our galaxy”.
The team was even able to determine its exact mass. But, thanks to the observations published today, its magnitude can be estimated. Two essential parameters to prove its existence conclusively.
Sagittarius A *, which is supposed to give its name to the direction of the Sagittarius galaxy, has approximately four million suns and is 27,000 light years away from Earth. Its existence has been considered since 1974 by the discovery of an unusual radio source in the center of the galaxy.
The thing was swallowed
Technically, you can not see a black hole because the material is so dense and its gravitational force is so strong that even light cannot escape from it. But before being swallowed, we can observe the object scattering around it: its shadow stands alone on this glowing disk.
“We have direct evidence that this object is a black hole,” explained Sarah Isaon of the Harvard Astronomical Center. [autour du trou noir] It emits radio waves and we’ve noticed “.
Roland Walter, an astrophysicist at the University of Geneva who specializes in black holes, explains that “this object is surrounded by a surface called the horizon.” In the forum microphone, he explains that the shadow in the middle is “the signature of the black hole’s presence”. It was very difficult to understand because, he notes, it was “too small, too bright, and there is a lot of meaning between it and us.”
Telescopes have to look at it for a long time to get something that can be used: “By recording this data and associating with it, we can recreate this image”.
>> Black hole size comparison Messier 87 * and Sagittarius A *:
Black holes M87 *, Messier 87 at the center of the galaxy and Sagittarius A * (Sgr A *), a size comparison at the center of the Milky Way. In terms of size, the orbits of Pluto and Mercury, as well as the diameter of the Sun and the current position of the Voyager 1 spacecraft far from Earth. Due to their relative distance from our planet, both objects appear to be the same size in the sky. [Lia Medeiros, xkcd – EHT collaboration]
The second historical film
The technique used for this image is millimeter radio interferometry. EHT, the International Network of Eight Radio-Astronomical Laboratories, brought in in 2019 the historic image of a gigantic black hole M87 * with six billion solar masses in its galaxy Messier 87, 55 million years ago.
>> Read: Mankind sees a black hole for the first time in history
Now equipped with eleven laboratories, EHT has depicted Sgr A * with its four million solar masses.
Scientists see this as evidence that the same mechanisms of physics operate at the heart of two systems at different levels: “Black holes are completely attractive objects. They are predicted by Einstein’s general relativity, but modern physics relies heavily on quantum kinetics. Roland Walter mentions.
“And the black hole is the place in the universe that connects these two theories” and can even find a theory that unites them! This is not the case at present: “This is the place where you can actually do basic physics,” says the astronomer.
>> A short film explaining how EHT works (in English, with French subtitles):
Stéphanie Jaquet and Agencies