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Astronomers have spotted the largest known stellar black hole in the Milky Way galaxy after detecting an unusual blip in space.
The so-called “sleeping giant,” named Gaia BH3, has a mass nearly 33 times that of our sun and is located 1,926 light-years away in the constellation Aquila, making it the second largest black hole. close to Earth. . The nearest black hole is Gaia BH1, located about 1,500 light-years away and with a mass nearly 10 times that of our sun.
Astronomers discovered the black hole while combing through observations taken by the European Space Agency’s Gaia space telescope for an upcoming release of data to the scientific community. The researchers did not expect to find anything, but a strange secret – which was the result of Gaia BH3’s gravitational influence on a nearby companion – caught their eye.
Many “dormant” black holes do not have a companion close enough to lie on them, so they are much harder to see and do not generate light. But other stellar black holes siphon material from companion stars, and this material exchange emits bright X-rays that can be seen through telescopes.
The wobbling motion of an old giant star in the constellation Aquila revealed that it was in orbit with a dormant black hole, the third such dormant black hole observed by Gaia.
The researchers used the European Southern Observatory’s Very Large Telescope in Chile’s Atacama Desert and other ground-based observatories to confirm the mass of Gaia BH3, and their study has also provided new clues about how the black holes came to be. that huge. The results appeared on Tuesday in the journal Astronomy & Astrophysics.
“No one expected to find a high-mass black hole nearby, which had not been noticed until now,” said lead study author Pasquale Panuzzo, an astronomer at the Observatoire de Paris, part of the National Center for France for Scientific Research, and member of the Gaia collaboration. , in a statement. “This is the kind of discovery you make once in your research life.”
secrets of the ancient stars free,
Sagittarius A*, the supermassive black hole at the center of the Milky Way, with about 4 million times the mass of the Sun, takes the title of the largest black hole in our galaxy, but that’s because it is 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 that it occurs when massive cosmic clouds collapse. Stellar black holes form when massive stars die. So Gaia BH3 is the most massive black hole in our galaxy formed from the death of a massive star.
The stellar black holes observed across the Milky Way galaxy are on average about 10 times as massive as the sun. Until the discovery of Gaia BH3, Cygnus X-1 was the largest known stellar black hole in our galaxy, which is 21 times the mass of the Sun. Although Gaia BH3 is an exceptional discovery within our galaxy by astronomers’ standards, it is similar in mass to objects found in very distant galaxies.
Scientists believe that stellar black holes with masses similar to Gaia BH3 were formed when metal-poor stars collapsed. These stars, which include hydrogen and helium as the heaviest elements, are thought to lose less mass over their lifetimes, so they have more material at the end that could lead to a high-mass black hole.
But astronomers couldn’t find evidence directly linking high-mass black holes and metal-poor stars until they discovered Gaia BH3.
The authors of the study said that the paired stars appear to be similar in composition. True to expectations, the researchers found that the star orbiting Gaia BH3 was metal-poor, meaning that 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,” study co-author Elisabetta Caffau, a member of the Gaia collaboration at Observatoire de Paris, said in a statement .
The star orbiting Gaia BH3 probably formed in the first 2 billion years after the big bang created the universe 13.8 billion years ago. The star’s trajectory, which moves in the opposite direction to many stars in the Milky Way’s galactic disk, suggests that it is part of a small galaxy that merged with the Milky Way more than 8 billion years ago.
Now, the team hopes that the research can allow other astronomers to study the supermassive black hole and reveal more of its secrets without waiting for the rest of the Gaia data release, which is planned for late 2025 .
“It’s amazing to see the transformative impact Gaia is having on astronomy and astrophysics,” Carole Mundell, the European Space Agency’s science director, said in a statement. “Its discoveries go far beyond the mission’s original purpose, which was to create an extremely precise multidimensional map of more than a billion stars across our Milky Way.”
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