Last year, scientists discovered GW190521, the largest gravitational wave event in the history of the merger of two black holes. The mass of the new black hole after the merger is 142 times the mass of the sun. However, according to new research conclusions, in fact, this may not be a double black hole collision, but a merger of two boson stars.
At present, the black holes we have discovered can only be classified into two categories: one is a stellar black hole with a mass between 5 to tens of times the mass of the sun; the other is a supermassive black hole with a mass of millions or even billions of times that of the sun. . A “blank zone” is formed between a stellar black hole and a supermassive black hole. Scientists cannot find a black hole whose mass falls in this gap. They can only assume that there is an intermediate mass black hole (IMBH) lurking in this zone with a mass between 100～ Between 10,000 solar masses.
Although some clues to intermediate-mass black holes have been discovered in the past, the evidence for their existence has yet to be confirmed. In September last year, LIGO and Vergo announced the gravity wave signal GW190521. According to analysis, this signal came from two black holes with a mass of 85 and 66 times the sun. The two merged to form a new black hole with a mass of 142 times the sun. It was the first medium-mass black hole to be confirmed.
However, this observation also poses a huge challenge to the existing stellar evolution model. If the current theory of star birth and death is correct, then it is impossible for a star to form a black hole of up to 85 solar masses when it collapses at the end of its life. How to explain the existence of this celestial body 85 times the mass of the sun?
Recently, an international team from the Galician Institute of High Energy Physics (IGFAE), the University of Aveiro in Portugal, the Advanced Institute of Technology of the University of Lisbon, the University of Valencia in Spain and the Monash University in Australia proposed a new source of GW190521 Object: Double Boson Star.
A strange boson star that may be made of dark matter
In the analysis of the new paper, the particles that make up these stars (the ultralight bosons) are billions of times smaller than electrons.
The boson star is still an imaginary celestial body, and it is also the simplest one among many imaginary strange stars. Compared with ordinary stars, which are mainly composed of fermions, boson stars are composed of stable and self-repelling bosons. , And the constituent matter is likely to be a hypothetical dark matter particle axion (Axion).
Therefore, compared with ordinary stars that emit light due to gravity and nuclear fusion, boson stars are theoretically invisible and difficult to detect. In essence, boson stars act like black holes and have strong gravitational pull from the surrounding environment. Absorbing matter and bending the path of light is similar to the situation near the event horizon of a black hole. The difference between the two is that light cannot escape from the black hole, but boson stars do not have this problem, and at most we cannot see it.
Researchers simulated the merging process of boson stars and found that they would produce a signal consistent with the GW190521 event. In other words, double boson stars can explain the origin of intermediate-mass black holes more reasonably than double black holes.
The team pointed out that because the merger process of boson stars is much weaker than the merger of black holes, the calculated distance is also closer than the original estimate, which will also cause the mass of the final black hole to increase, about 250 suns. The mass is still within the range of a medium-mass black hole, but it can solve the problem that the original black hole exceeds the theoretical upper limit.
This is likely to be the first evidence of the discovery of a boson star, but it is still uncertain. If this research is rigorously reviewed and confirmed, the achievements will go far beyond the discovery of new celestial bodies, and it will help unlock the universe. One of the most puzzling mysteries in science-dark matter, that is, the existence of axons.
New treatisePublished in “Physical Review Letters” (Physical Review Letters).
(Source of the first image:IGFA）
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