An international team of astronomers confirmed, on Thursday, the presence of a supermassive black hole in the heart of our galaxy called “Sagittarius A8”.
This image came three years following the publication of the first image of a black hole located in a distant galaxy.
The black hole’s “shadow” on a luminous disk of matter is reminiscent of the black hole in the distant galaxy M87, which is much larger than our own Milky Way.
Scientists see this as evidence that the same mechanisms of physics operate at the core of two systems of very different sizes.
“I can show you an image of the Sagittarius A black hole in the middle of the galaxy,” EHT project manager Hoip Jan van Langevelde told a press conference in Garching, Germany, to applause.
Technically, a black hole cannot be seen, because this object is so dense and its gravitational force is so strong that not even light can escape from it. But the material swirling around it can be observed before it is swallowed.
“We have direct evidence that this object is a black hole,” Sarah Esson of the Harvard Center for Astrophysics explained, describing: “The gas cloud (around the black hole) emitting radio waves that we observed.”
Black holes are stellar when they have a mass of a few suns, or extremely massive when they have a mass of millions or even billions of suns.
The mass of “Sagittarius A” or “SGRA”, which is named following its discovery in the direction of the constellation Sagittarius, is regarding four million suns and is 27,000 light years away from Earth. Its existence has been assumed since 1974, with the discovery of an unusual radio source in the galactic center.
In 2019, EHT, an international network of eight radio astronomical observatories, brought the historical image of “M87”, a supermassive black hole with a mass of six billion solar masses in its galaxy called “Messier 87” located 55 million km away. Light year.
With a solar mass of four million, sGRA is classified as an extremely light in the group of supermassive black holes.
“These unprecedented observations have greatly improved our understanding of what is happening at the center of our galaxy,” said EHT project scientist Jeffrey Bauer of Taiwan’s Academia Sinica.
moving targets
In the 1990s, astronomers mapped the orbits of the brightest stars near the center of the Milky Way, confirming the presence of a compact, supermassive object there, a work that won the Nobel Prize in Physics in 2020.
The black holes SGRA and M87 bear striking similarities, although the first is 2,000 times smaller than the second.
“Near the edges of these two black holes, the similarity is striking,” said Sera Markov, co-chair of the EHT Science Council and a professor at the University of Amsterdam.
Both acted according to Einstein’s theory of general relativity in 1915, which notes that the force of gravity is caused by the curvature of space and time, and cosmic bodies change this geometry.
Although SGRA is much closer to us, its portrayal presents unique challenges.
Gas near the black holes is moving at the same speed, close to the speed of light. But while it took weeks to circle the M87, the rounds around the SGRA took just minutes.
The brightness and pattern of the gas around the SGRA changed rapidly as the team monitored it, “a bit like trying to capture a clear picture of a puppy chasing its tail quickly,” said EHT scientist Chi Kwan Chan of the University of Arizona. .
Researchers have had to develop sophisticated new tools to use in monitoring moving targets.
The image obtained by the team following the efforts of more than 300 researchers in 80 countries over a period of five years, is the result of compiling many images of the massive hole in the center of the galaxy.
Scientists are now eager to compare the two black holes to test theories regarding how gas behaves around them, a poorly understood phenomenon believed to play a role in the formation of new stars and galaxies.
Exploring black holes, especially their centers so infinitely small and dense that Einstein’s equations are broken, would help physicists deepen their understanding of gravity and develop a more advanced theory regarding it.
