Astronomers identified the stellar black hole most massive known in Milky Way after detecting an unusual oscillation in space.
The so-called “sleeping giant”, named Gaia BH3 has a mass almost 33 times greater than that of our Sun and is located 1,926 light years away in the constellation Aquila , making it the second closest black hole to Earth ever known. The closest black hole is Gaia BH1, which is located about 1,500 light-years away and has a mass almost 10 times that of our Sun.
Astronomers discovered the black hole while combing through observations made by the European Space Agency (ESA) Gaia Space Telescope for the next release of data to the scientific community. Researchers weren't expecting to find anything, but a peculiar motion — caused by Gaia BH3's gravitational influence on a nearby companion star — caught their attention.
Many “sleeping” black holes don’t have a companion close enough to devour, so they are much harder to detect and don’t generate any light. But other stellar black holes suck in matter from companion stars, and this exchange of matter releases bright X-rays that can be detected by telescopes.
The wobbling motion of an old giant star in the constellation Aquila revealed that it was in an orbital dance with a dormant black hole, making it the third dormant black hole of its kind detected by Gaia.
Researchers used the European Southern Observatory's (ESO) Very Large Telescope in Chile's Atacama Desert and other ground-based observatories to confirm the mass of Gaia BH3. The study also offered new clues about how these massive black holes formed. The findings were published on Tuesday (16) in Astronomy & Astrophysics magazine.
“No one expected to find a high-mass black hole lurking nearby, undetected until now,” said study lead author Pasquale Panuzzo, an astronomer at the Paris Observatory, part of France's National Center for Scientific Research and a member of the collaboration. Gaia, in a statement. “This is the kind of discovery you make once in a lifetime as a researcher.”
The secrets of ancient stars
The title of most massive black hole in our galaxy will always belong to Sagittarius A*, the supermassive black hole located in center of the Milky Way which is about 4 million times the mass of the Sun, but that's because it's a supermassive black hole, rather than a stellar black hole.
The process by which supermassive black holes form is poorly understood, but one theory suggests it happens when massive cosmic clouds collapse. Stellar black holes form when massive stars die. Therefore, Gaia BH3 is the most massive black hole in our galaxy, formed from the death of a massive star.
Stellar black holes observed throughout the Milky Way are about 10 times the mass of the Sun, on average. Until the discovery of Gaia BH3, the largest known stellar black hole in our galaxy was Cygnus X-1, which is 21 times the mass of the Sun. Although Gaia BH3 is an exceptional find in our galaxy by astronomers' standards, it has similar mass to objects found in very distant galaxies.
Scientists believe that stellar black holes with masses like Gaia BH3 formed when metal-poor stars collapsed. These stars, which include hydrogen and helium as their heaviest elements, likely lose less mass over their lifetimes, so they have more material at the end, which could result in a high-mass black hole.
But astronomers have been unable to find evidence directly linking high-mass black holes and metal-poor stars until they discovered Gaia BH3.
The study authors said that stars in pairs tend to have similar composition. True to expectations, the researchers found that the star orbiting Gaia BH3 was metal-poor, meaning the star that formed Gaia BH3 was likely the same.
“What strikes me is that the chemical composition of the companion is similar to what we find in old, metal-poor stars in the galaxy,” said study co-author Elisabetta Caffau, a member of the Gaia collaboration at the Paris Observatory.
The star orbiting Gaia BH3 likely formed within the first 2 billion years after the big bang created the universe 13.8 billion years ago. The trajectory of the star, which moves in the opposite direction of many stars in the Milky Way's galactic disk, suggests it was part of a small galaxy that merged with the Milky Way more than 8 billion years ago.
Now the team hopes the research will allow other astronomers to study the colossal black hole and discover more of its secrets without having to wait for the rest of Gaia's data release, scheduled for late 2025.
“It is impressive to see the transformative impact that Gaia is having on astronomy and astrophysics,” said Carole Mundell, director of science at the European Space Agency. “Their discoveries are going far beyond the mission’s original purpose, which was to create an extraordinarily accurate multidimensional map of more than a billion stars across the Milky Way.”
Source: CNN Brasil
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