Astronomers from the University of Birmingham in the UK have uncovered the circumstances of a catastrophic collision of black holes, located at a distance of 1-3 billion light years from Earth. Scientists analyzed the data obtained by registering gravitational waves that occurred at the time of the merger. It turned out that the objects revolving around each other were not similar to those found in the Milky Way. The material on this was published in the journal Nature.
Binary (binary) systems, such as a pair of black holes orbiting each other, are characterized by a parameter called the effective spin. It shows how the axis of rotation of the objects themselves is oriented relative to the orbital plane and takes values from minus one to one. If the direction of proper rotation of black holes coincides with the direction of their orbital rotation, then the effective spin is greater than or equal to zero. In this case, astronomers conclude that the objects were born together. Otherwise, one black hole could simply be captured by another, or both objects rotate very slowly.
In the Milky Way, currently known systems including black holes have high effective spin. In this case, the axes of even initially disoriented objects are usually aligned due to tidal forces and the transfer of matter.
Scientists analyzed data obtained by the laser-interferometric gravitational-wave observatory LIGO, which recorded space-time disturbances four times. The researchers determined the effective spins for each pair of black holes, whose catastrophic merger led to the generation of gravitational waves. These objects are located at a distance of 1-3 billion light years from Earth.
It turned out that this parameter takes predominantly low values. At the same time, the models of binary black holes, the effective spins of which corresponded to the observed ones, did not help to accurately explain such a result. Although scientists are inclined to believe that the axes of the colliding objects were most likely disoriented, it is possible that the black holes rotated slowly.
According to the researchers, the rotation and direction of the axis of the merged objects could be influenced by a supernova shock wave, dense interstellar medium, or other processes. In this case, the low effective spin could persist for a long time until the black holes collided with each other.