Astronomers have discovered a black hole in the Milky Way so large that it defies existing models of how stars evolve, researchers said on Thursday.
LB-1 is 15,000 light years from Earth and has a mass 70 times larger than the Sun, according to Nature magazine.
The Milky Way is estimated to contain 100 million star black holes, but LB-1 is twice as large as anything scientists thought possible, said Liu Jifeng, professor at the China National Astronomical Observatory who led the research. .
"Black holes of this mass should not even exist in our galaxy, according to most current models of stellar evolution," he added.
Scientists generally believe that there are two types of black holes.
The most common star black holes – up to 20 times more massive than the sun – form when the center of a very large star collapses.
Supermassive black holes are at least a million times larger than the sun and their origins are uncertain.
But the researchers believe typical Milky Way stars release most of their gas through stellar winds, preventing the emergence of a black hole the size of an LB-1, Liu said.
"Now theorists will have to accept the challenge of explaining their background," he said in a statement.
& # 39; New Type & # 39; black hole
Astronomers are still just beginning to understand "the abundance of black holes and the mechanisms by which they form," David Reitze, a physicist at the California Institute of Technology (Caltech), told AFP that he had not participated in the discovery.
The Reitze-supervised Laser Interferometer Gravitational Wave Observatory had already detected ripples in space-time suggesting the possibility of black holes in far larger galaxies than previously thought possible.
Stellar black holes are usually formed after supernova explosions, a phenomenon that occurs when extremely large stars burn at the end of their lives.
The large mass of LB-1 falls within a range "known as the pair instability gap where the supernovae should not have produced," Reitze said.
"It means this is a new kind of black hole, formed by another physical mechanism!"
100 million black holes
The LB-1 was discovered by an international team of scientists using China's sophisticated LAMOST telescope.
Additional images from two of the world's largest optical telescopes – the Gran Canarias Spanish Telescope and the Keck I telescope in the United States – confirmed the size of the LB-1, which China's National Astronomical Observatory said was "nothing short of fantastic." .
Scientists tend to find black holes by detecting the X-rays they emit.
But this method has limited utility because only a small number of black hole systems in which the companion star orbits very close to the black hole emits detectable X-rays, Liu told a news conference.
Instead, the team that discovered LB-1 tracked the movements of "a large number of stars over a long period of time" before identifying LB-1 based on its companion star's movement, Liu said.
This method has been used for decades without much success due to the limitations of available equipment, Liu added.
But LAMOST, built between 2001 and 2008 in northern China's Hebei Province, allows researchers to detect up to 4,000 stars simultaneously with each exposure, making it one of the most powerful ground telescopes in the world.
Liu told AFP that the method used to discover LB-1 could help scientists identify many other black holes in the future.
Of the 100 million black holes believed to exist in our galaxy, Liu said, only 4,000 "can provide X-rays that can be detected by us."