Astrophysicists using gravitational wave detectors LIGO and Virgo for the first time saw how a black hole belonging to the intermediate class of mass is formed. Previously, scientists only assumed the possibility of the existence of such objects. The results are published in the journal Physical Review Letters and Astrophysical Journal Letters.
“LIGO and Virgo caught their biggest fish,” they write enthusiastically about the discovery in a press release of the German Institute of Gravitational Physics by Max Planck. On May 21, 2019, both detectors detected the signal GW190521, which scientists interpreted as the merger of two black holes weighing 85 and 66 solars with one new one formation – with a mass of 142 times the size of the Sun.
This is the largest confluence of black holes ever observed in gravitational waves, as well as the first confirmation of the existence of objects occupying an intermediate position between light black holes, which are located in the centers of galaxies and weigh up to 100 solar masses, and super-heavy – from 100,000 solar masses, arising from the collapse of massive stars. Until now, scientists had only circumstantial evidence from electromagnetic observations.
It is also the most distant event recorded in gravitational waves. It took seven billion years for the signal to reach us, which means that the birth of a black hole, accompanied by the release of vast amounts of energy, occurred when the universe was half the age of.
Astrophysicists have long been trying to find intermediate-mass black holes. Their existence could support the hypothesis that supermassive black holes are formed as a result of successive mergers of smaller ones.
By the way, one of the two original holes – weighing 85 solar – according to the authors, is also likely formed by the merger of the other two, because, based on current views, the gravitational collapse of the star can not form black holes with a mass of 60 to 120 solar, because the most massive stars fly apart as a result of a supernova explosion, which accompanies the collapse, leaving only gas and dust. This range in astrophysics is called the rupture of the mass of vapor instability.
“We have been looking for an intermediate-mass black hole for a long time to close the gap between the black stars and supermassive black holes. Now we have proof of the existence of intermediate black holes,” said one of the study’s authors, Professor Christopher Berry of the Center for Interdisciplinary Research and Astrophysics at Northwestern University in the United States.
The signal GW190521 in the form of four small vibrations was extremely short, it lasted less than one-tenth of a second. But it was the most powerful signal that LIGO and Virgo detectors had ever recorded. In a short time, its frequency increased from 30 to 80 hertz before the event ended.
To date, almost every confirmed signal of gravitational waves is derived from the merger of two black holes or two neutron stars.
“Each new event refines our understanding of how black holes are formed. With these gravitational wave breakthroughs, we’ll soon have enough data to reveal the secrets of how black holes are born and how they grow,” Berry says.
Based on observations, scientists have built a model of rotation of black holes before merging. The authors suggest that as black holes approached each other, they began to rotate around their own axes at angles that did not match the axis of their orbit. Uneven rotation, according to the authors, caused their orbits to fluctuate, or precess, which eventually led to a fusion.