The Smallest and Closest to the Earth Black Hole is Discovered
OREANDA-NEWS. Astronomers have discovered an object that claims to be the smallest and closest to the Earth black hole in the universe. So far, it has received only an unofficial name: Unicorn. She received this name for her exclusivity, as well as for being in the constellation of the Unicorn.
Prior to that, scientists believed that the masses of black holes formed by exploding stars should start at around 2.7 solar. However, for many years, observers have known only black holes with a mass of five suns. Many experts believed that lighter black holes in supernova explosions did not form at all.
And in 2019, astronomers discovered a black hole with a mass of about 3.3 solar in the constellation Auriga. The success came thanks to a new method. The researchers purposefully searched for stars orbiting something invisible and massive. As a result, their attention was attracted by the red giant star 2MASS J05215658 + 4359220. She was found to have a companion that turned out to be a black hole.
This result inspired scientists to continue their search. Now a team of researchers, which includes several discoverers of the black hole in Auriga, reported the discovery of a similar object in the Unicorn.
The black hole was found by the same method. A red giant turns around her too. The black hole's gravity not only makes the star move in its orbit, but also pulls it out, transforming the celestial body from a ball into a kind of melon or potato. This deformation and the speed of the star's orbital motion helped scientists calculate the mass of an invisible object. It turned out to be 3.04 ± 0.06 solar.
Thus, the Unicorn is probably the lightest black hole known to science to date.
It is also noteworthy how close the Unicorn is to Earth: it is only 1,500 light years away (this is about 67 times smaller than the diameter of the Galaxy). The authors call their find the closest black hole to Earth.