If supersensitive gravitational wave detectors register waves from merging black holes from sources with high redshifts more often than once a year, then these sources are black holes that appeared without supernova explosions.
Astrophysicists Savvas M Koushiappas of Brown University in Rhode Island and Abraham Loeb of Harvard calculated how often black holes should merge in the observable universe. In the calculations, the scientists proceeded from the assumption that black holes are formed as a result of the gravitational collapse of massive stars, and those, in turn, from matter trapped in a dark matter halo. For the star formation process to begin, the halo mass must be above the limit calculated in the previous work of the other team.
According to calculations, for objects with a redshift of 40 (meaning that the object formed about 65 million years after the Big Bang), the frequency of collisions of black holes in the observable part of the Universe should be less than one event per year - if black holes are formed only as a result of supernova explosions. The redshift is the shift of the spectral lines of chemical elements, which increases approximately proportionally to the distance to the observed radiation source, and therefore to its age.
There is another hypothetical pathway for the formation of black holes. According to this hypothesis, primordial black holes could have arisen in the early stages of the universe, earlier than 550 million years after the Big Bang, in places where matter was particularly dense.
Loeb and Kushiappas suggested that if high-precision gravitational-wave detectors detect more than one black hole merger with redshifts of more than forty per year, this would mean that primordial black holes do exist. By the number of such events, it will be possible to judge the nature of the early Universe and the matter in it.
Recall that the LIGO / Virgo collaboration has recorded gravitational waves created by merging black holes four times already. In 2017, the heads of the collaboration, Rainer Weiss, Barry Barish and Kip Thorne, received the Nobel Prize in Physics for the creation of the LIGO detector and the registration of the first gravitational waves.
Previously, scientists suggested that black holes in a young universe could be born as a result of the collapse of matter in high-speed streams.
The article was published in Physical Review Letters.
Promotional video:
Ksenia Malysheva