University of California, Berkeley found an object that could be a free-floating black hole. It could be seen watching the light of a distant star, which became brighter due to the strong gravitational field of the object – the so-called gravitational microlensing.
Astronomers believe that the death of big stars leaves behind black holes, of which there must be hundreds of millions in the Milky Way galaxy. However, these holes are still invisible.
The Berkeley team estimates that the mass of the object found is 1.6-4.4 times greater than the mass of the Sun. Since astronomers believe that the remains of a dead star must be 2.2 times heavier than the Sun to collapse into a black hole, the object found could also be a neutron star.
Neutron stars are dense and compact objects. However, their gravity is balanced by internal neutron pressure, which prevents them from turning into black holes.
The detected object is the first dark stellar remnant – a stellar “ghost” – found roaming through a galaxy without a pair with another star. Astronomers are going to determine how many such objects are in the Milky Way. This will help them study the evolution of stars and galaxies, and perhaps find out if there are any primary black holes in these objects. It is believed that such holes formed in large numbers after the Big Bang. According to preliminary estimates, there are about 200 million “ghosts” in the galaxy.
Interestingly, the other team also studied found object, their numbers differ. Scientists from the Space Telescope Science Institute in Baltimore have estimated that the weight of the “ghost” is closer to 7.1 than the mass of the Sun. In this case, the find is almost certainly a black hole.
The distance to the object is also different. The University of California claims that it is between 2280 and 6260 light years. Competitors estimate that there are 5,153 light-years from Earth to the object.