By Write news
See my news
The galaxy and its billions of stars. Its mysteries too, which have fascinated the scientific community and space enthusiasts for years.
One of them has just been revealed this Thursday, May 12, in the magazine The Astrophysical Journal Letterswith the proof, in the image of existence of a supermassive black hole in the heart of the Milky Way : Sagittarius A *.
It is thanks to the international collaboration of astronomers EHT (Event Horizon Telescope) that the discovery was made, three years after the first photo of a black hole, located in a distant galaxy. In a press release, CNRS explains:
To achieve this image, it was necessary to combine the data collected night after night by the eight telescopes scattered on our planet, and then to refine the “raw” images obtained by relying on the digital models of black gaps available to researchers. .
A diameter equal to 30 times that of the Sun.
Sagittarius A * (Sgr A *), which owes its name to its detection in the direction of the constellation Sagittarius, has a diameter equal to 30 times that of the Sun. and is 27,000 light-years from Earth.
Its existence has been adopted since 1974, with the detection of an unusual radio source at the center of the galaxy. “But since it is located 27,000 light-years from Earth, its apparent size is an orange that we would distinguish on the Moon,” CNRS reports.
What is a black hole?
According to CNRS, a “black hole” is defined as “an area in space where there is a gravitational field so intense that not even light can escape”. Understand that if nothing moves faster than light, then everything that enters this region is “trapped there”.
The “silhouette” of the black hole set in the silhouette against a luminous disk of fabric is reminiscent of the silhouette of the black hole in the distant galaxy M87, which is much larger than ours.
Researchers see this as proof that the same physics mechanisms are at work in the heart of two systems of very different sizes.
Technically, you can not see a black hole because the object is so dense and its gravity so strong that not even light can escape from it. But we can observe the material circulating around before it is swallowed.
“We have direct evidence that this object is a black hole,” explained Sara Issaoun, of the Harvard Center for Astrophysics, describing “the cloud of gas (around the black hole) that emits radio waves and that we have observed. . »
Very old, just like our galaxy about 13 billion yearshe lost his appetite and swallows very little material. “If you ate like him, it would be like a grain of rice every two million years,” smiled Sara Issaoun.
Unlike its famous genus, M87 *, which still celebrates. And Earthlings have so much less to fear, as our planet is far from the galactic center.
Black holes are said to be stars when they have the mass of few suns, or supermassive when they have a mass of millions or even billions of suns.
With its four million solar masses, Sgr A * a featherweight in the bestiary of supermassive black holes.
Five year calculation
The displayed image is the result of several hours of observation performed mainly in 2017 and followed by five years of calculations and simulations involving more than 300 researchers from 80 institutes.
It was much harder to achieve than the M87 * because the black hole in the middle of the Milky Way is much smaller. The cloud of gas that surrounds it before it was swallowed into it, barely enough 12 minutes to walk around Compared to more than two weeks for M87 *.
The brightness and configuration of the gas therefore changed rapidly during the observation: “It’s a bit like trying to take a clear picture of a puppy chasing its tail,” commented Chi-Kwan Chan, a scientist from EHT.
The two images and their comparison will make it possible to study in more detail the behavior of matter in the most extreme environment of the universe, “with gases heated to billions of degrees, powerful magnetic currents and matter circulating at a speed close to light”, explained to AFP , Professor Heino Falcke, former head of the EHT Scientific Council.
This environment should make it possible to observe the deformations of space-time near a supermassive object and the behavior of gravity, predicted in the general theory of relativity, which Albert Einstein postulated in 1915.
Was this article helpful to you? Note that you can follow Actu in the My Actu room. With a single click, after registration, you will find all the news about your favorite cities and brands.