Scientists may have discovered the smallest black hole ever discovered, according to a study published in the journal Science. This is made possible by a new technique that combines multiple datasets. The researchers believe that the black hole is about 3.3 times more massive than the Sun and is located in the J05215658 binary system, which is located about 10,000 light-years from the outer edge of the Milky Way disk. While more research is needed to confirm the black hole's low mass, there is a possibility that the object is part of a mysterious class of small black holes. These objects have not been discovered in the past, as no one understood exactly how to look for them.
Could small black holes exist?
Most of the observed black holes are about 5-15 times more massive than the Sun, but this does not mean that all black holes in the Universe are of this size. This is partly because massive and supermassive black holes are much easier to detect. When such objects revolve around stars in binary systems, they attract material from their satellites. This accretion process emits X-rays that can be observed with telescopes.
Small black holes that are only two to five times more massive than the Sun, provided they exist, do not appear to produce this X-ray signature, making these objects invisible to scientists. When a star goes supernova, the subsequent evolution of the star is determined by its mass. Small stars become neutron stars, the densest objects in the universe, while large stars collapse into black holes. However, researchers cannot yet say how massive a star must be to become a black hole. It is possible that there is an intermediate process in which the star temporarily becomes a neutron star and then evolves into a black hole.
The most mysterious objects in the universe may turn out to be portals to other universes
Scientists wanted to find out if there is anything in common between the most massive neutron stars known to date (whose mass is about 2.1 times the mass of the Sun) and the least massive black holes, the mass of which does not exceed five solar masses.
To fill this gap, the research team has screened observations of about 100,000 stars in the Milky Way using the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Scientists have looked for signs of stars in binary systems with black holes in much the same way that some exoplanet researchers search for worlds around other stars. By observing how stars affect gravity from nearby objects, the team narrowed the search down to a few hundred candidates who may have satellites. The researchers then used data from the automated supernova survey (ASAS-SN) to further search for the desired system. As a result, by combining the two datasets, the scientists found the very star. As writes the edition of Vice, the new method proved to be incredibly effective in finding previously invisible objects.
Figure illustrating the mass gap between neutron stars and black holes
Despite the fact that according to the most probable estimates, the mass is equal to 3.3 times the mass of the Sun, the researchers do not exclude that the object J05215658 could potentially turn out to be about five times more massive than the Sun. Previously, several other black holes were discovered, the mass of which researchers still argue about, so at the moment it is not safe to say that the new object is the smallest of all black holes known today. However, the very suggestion that the most mysterious objects in the universe might be even more mysterious should probably not surprise us.