The echoes of the largest black hole collision reached the earth in 2020.
Astronomers have recorded the fusion of black holes, on a scale ahead of all previously discovered cases. This incredible cataclysm occurred 7 billion years ago, but its traces only reached us, and the researchers had the opportunity to be in the front row at the birth of one of the rarest objects in the universe. The corresponding discovery is described in the article for Physical Review Letters.
One of the black holes reached the size of 66 solar masses, the other – 85 solar masses. As they approached, they began to rotate one around the other, making several turns per second, before colliding and producing a huge emission of energy, which spread across the universe. As a result of the merger, a huge black hole of 142 solar masses was formed.
The event was called GW190521. In fact, no one directly observed it. Its power was so weak that the hardware could well miss it. The detectors caught only four small waves from the fusion. These ‘outrages’ only lasted a fraction of a second.
This discovery is of great importance for astrophysicists who have long been hunting for medium-mass black holes, one of the rarest kinds of black holes. Most often, researchers observe smaller objects (from 5 to 100 solar masses) and supermassive objects (sizes count in millions of solar masses and above), which are in the center of many galaxies. Direct evidence of the existence of black holes of average mass has not been obtained until now, there are only potential candidates.
One theory of the appearance of supermassive black holes is based on the hypothesis that smaller objects merge with each other, gradually reaching huge sizes. In this case, there should be “medium” black holes, which would become an intermediate link. “Therefore, astronomers are looking for them diligently, because they will help to fold the puzzle”, – explained Salvatore Vitale from the laboratory LIGO at the Massachusetts Institute of Technology.