Illustration drawing showing two supermassive black holes orbiting one in the galaxy 0402 + 379, located 750 million light-years away from us.
Josh Valenzuela / UNM
This major discovery, which took nearly 15 years of work, allows us to better understand the evolution of the universe, but also to imagine the future of our galaxy.
Look at the past to better understand the future of our galaxy, even our species, if we are still alive by then. Astronomers managed to observe, for the first time, two supermassive black holes orbiting one another, reveals their study published in The Astrophysical Journal, available on arXiv.org.
"For a very long time, we scanned space, looking for a pair of supermassive black holes in orbit, the result of the fusion of two galaxies," says Greg Taylor, one of the astronomers at the origin of the discovery , On the site of the University of New Mexico (UNM), but if we had theoretically planned this event [considered a natural step in the evolution of galaxies], nobody had ever observed it. Perhaps because the black holes that meet meet up very quickly or because one of the two black holes is expelled, researchers say in their study.
Observing the invisible, mission (not so) impossible
But also because the black holes are so massive that they even absorb light, and are therefore (almost) invisible. To "see" them, one must observe their surroundings and detect the influence they exert on the surrounding matter. To achieve this, astronomers pointed to the Very Long Baseline Array (VLBA), a network of 10 radio telescopes, to galaxy 0402 + 379, about 750 million light-years away from Earth. They then recorded different radio frequencies emitted by two black holes, named C1 and C2.
"Professor Greg Taylor first sent me the first data from the VLBA [...], which we have combined with VLBA data from 2003," explains UNAM researcher Karishma Bansal and lead author of the VLBA. This is what made it possible for us to determine that the two black holes orbit one around the other. But contrary to what the illustration above suggests, the astronomers could not see two magnificent black holes in the center of their galaxy, but rather that:
Observations of galaxy 0402 + 379 obtained from the Very Long Baseline Array telescope network. The two black holes were named C1 and C2.
UNM / Very Long Baseline Array
Or, in its most visual version:
VLBA colorized map of galaxy 0402 + 379, which hosts two supermassive black holes in its center, C1 and C2.
UNM Newsroom
This is already exceptional
15 billion times more "heavy" than our Sun
Especially since these observations also allowed them to determine the mass of the two galactic monsters, which is about 15 billion times higher than that of our Sun. The two entities are separated by 7.3 parsec, or 23.8 light-years. They go around each other in about 24,000 years, adds Karishma Bansal.
This means that, despite ultra-precise observations spread over more than 15 years, astronomers have not been able to detect the slightest trace of curvature in the respective trajectories of black holes.
"Imagine a snail traveling at 1 cm per second on a planet orbiting Proxima Centaur-a star located at 4243 light-years from Earth-and this is the kind of angular momentum [trajectory] Attempts to calculate, illustrates Roger W. Romani, a researcher from Stanford University. Obviously, the astronomers team will continue to observe the two black holes to refine its results.
The Andromeda galaxy puts us on top
Far from being anecdotal, this new study will greatly improve our understanding of the black holes, which are still very enigmatic, even after the discovery of gravitational waves. Observing these two black holes in orbit should enable us to better understand where the galaxies - especially our own, the Milky Way - are coming from, where they are heading and the role of black holes in this process.
This is particularly interesting when we know that the Andromeda galaxy, which has a supermassive black hole in its center, like the Milky Way, strikes us at 430,000 km / h. What UNM researchers are currently observing in galaxy 0402 + 379 may well be what awaits us when Andromeda strikes us in about four billion years.
From top to bottom and from left to right.1) Today Andromeda appears as a small oval spot. 2) +2 billion years, it will be much larger 3) + 3.75 billion years, it will spread throughout the sky 4) + 3.85 billion years: collision causes births d Series stars. 5) +3.9 billion years, the stellar outbreak continues. 6) +4 billion years, the two galaxies are totally deformed.
NASA / ESA
"Supermassive black holes exert enormous influence on the stars around them, but also on the growth and evolution of galaxies," says Greg Taylor, "better understand them and better understand what happens when They are very important for our understanding of the universe. "
Deux trous noirs se tournent autour et nous permettent de voir l'avenir
