Merging forest stars can explain the massive collision in black holes and prove the existence of dark matter

An international team of scientists led by the Galician Institute of High Energy Physics (IGFAE) and the University of Aveiro shows that the heaviest drilling with black holes ever observed and produced by the gravitational wave GW190521 may still be something mysterious : the fusion of two forest stars. This would be the first proof of the existence of these hypothetical objects, which are a candidate for dark matter, which is believed to make up 27% of the mass in the universe.

Gravitational waves are wrinkles in the tissue of space-time that move at the speed of light. It comes from the most violent events in the universe, with information about their sources. Since 2015, the two LIGO detectors in the US and the Virgo detector in Cascina, Italy, have detected and interpreted gravitational waves. To date, these detectors have detected about 50 gravitational wave signals. All of this originated in the collisions and mergers of black holes and neutron stars, allowing physicists to deepen their knowledge about these objects.

However, the promise of gravitational waves goes far beyond that, as it should ultimately provide us with evidence for previously unnoticed and even unexpected objects, and shed light on current mysteries such as the nature of dark matter. However, the latter may have already happened.

In September 2020, the LIGO and Virgo collaboration (LVC) announced the gravitational wave signal GW190521 to the world. According to their analysis, the signal corresponds to the collision of two heavy black holes, 85 and 66 times the solar mass, yielding a final black hole with 142 solar masses. The resulting black hole was the first of a new, previously unmarked black hole family: intermittent black holes. This discovery is of paramount importance, as such black holes were the missing link between two known black hole families: star masses formed by the collapse of stars, and supermassive black holes found in the center of almost every galaxy, including the Milky Way.

In addition, this observation posed an enormous challenge. If what we think we know about how stars live and die is correct, the heaviest of the colliding black holes (85 solar masses) could not have arisen due to the collapse of a star at the end of its life. , which opens up a variety of doubts and possibilities about its origin.

In an article published today in Physical overview letters, a team of scientists led by Dr Juan Calderón Bustillo at the Galician Institute of High Energy Physics (IGFAE), joint center of the University of Santiago de Compostela and Xunta de Galicia, and Dr Nicolás Sanchis-Gual, a postdoctoral researcher at the University of Aveiro and the Instituto Superior Técnico (Univ. Lisboa), together with collaborators from the University of Valencia, Monash University and the Chinese University of Hong Kong, proposed an alternative explanation for the origin of the signal GW190521: the collision of two exotic objects known as forest stars, which is one of the most likely candidates to explain dark matter. In their analysis, the team was able to estimate the mass of a new particle component of these stars, an ultralight boson with a mass billions of times smaller than electrons.

The team compared the GW190521 signal with computer simulations of mergers between forest stars and found that it actually explains the data better than the analysis done by LIGO and Virgo. The result implies that the source will have different properties than those mentioned earlier. Dr. Calderón Bustillo says: “Firstly, we will no longer talk about the collision of black holes, which eliminates the issue of dealing with a ‘forbidden’ black hole. Secondly, because the fusion of forest stars is much weaker, we are a much narrower distance down than those estimated by LIGO and Virgo, which results in a much larger mass for the final black hole, of about 250 solar masses, hence the fact that we are forming an intermediate mass of black hole have seen, stay true. ‘

Dr. Nicolás Sanchis-Gual says: “Forest stars are objects that are almost as compact as black holes, but, unlike them, do not have a ‘no return’ surface. When they collide, they form a forest star that can eventually become unstable. collapses into a black hole and produces a signal similar to that observed by LIGO and Virgo, unlike ordinary stars, which consist of what we generally know as matter, boson stars consist of what we call ultralight bosons. This forest zone is one of the most attractive candidates for the composition of what we know as dark matter. ‘

The team found that, although the analysis tends to favor the merging hypothesis of black holes, a fusion of boson stars is actually preferred by the data, although in a non-conclusive way. Prof. Jose A. Font of the University of Valencia says: “Our results show that the two scenarios are almost indistinguishable, given the data, although the exotic boson star hypothesis is slightly preferred. This is very exciting as our boson star model “From now on, very limited and subject to major improvements. A more developed model could lead to even greater evidence for this scenario and would also allow us to study previous gravitational wave observations under the fusion star of the bush star.”

This result will not only involve the first observation of boson stars, but also that of their building block, a new particle known as an ultralight boson. Prof. Carlos Herdeiro of Aveiro University says: “One of the most fascinating results is that we can measure the mass of this supposed new dark dust particle, and that the value of zero is thrown away with great confidence. An analysis of these and other gravitational wave observations would our result provides the first evidence for a long-sought candidate for dark matter. ‘