Some dark matter models postulate the existence of very heavy particles that penetrate matter in detectors on Earth that are indistinguishable from the neutrinos of the Big Bang. But these particles could turn neutron stars into unusually low-mass black holes, like those we might detect with gravitational waves.
Looking back, we can say that the idea of dark matter – we spoke of missing mass or hidden mass back then – emerged in the noosphere almost a century ago with the work of the Swiss astronomer Zwicky. By studying the movements of galaxies within the Coma galaxy cluster in the constellation Berenice’s Hair, he realized that, despite the very high velocities, the cluster appeared to show no signs of sustained dispersal. And yet, the mass derived from the luminosity of the stars of these galaxies suggested that gravity was apparently insufficient to counteract the evaporation of the clusters, which are considered a type of hot gas from self-galaxies.
It was necessary to postulate the existence of hidden masses that do not emit light, a hypothesis that we will take up following the work of Vera Rubin on the speed of stars and gases, this time at the level of galaxies, and which we Dark will be called matter.
The search for these hidden masses began in earnest around thirty years ago, at a time when several theories proposed going beyond the physics known from the Standard Model of high energy physics and predicting the existence of dark matter particles in a natural way. The zoo of these particles (million-charged particles, “fuzzy” dark matter, etc.) has only expanded since then, as attempts to detect them by producing them in accelerators or by studying anomalies in radiation cosmics have been unsuccessful.
Huge detectors buried under mountains to filter common cosmic radiation have also failed so far, for example XENON1T. To top it all off, on the contrary, an alternative to dark matter particles is gaining more and more weight, the lunar theory, which proposes to modify Newton’s laws of celestial dynamics and thus ultimately Einstein’s theory of gravity.
Dark matter particle hunters have not yet said their last word, according to a team of theoretical physicists from the Tata Institute of Fundamental Research in Mumbai, India, the Indian Institute of Science in Bengaluru and the University of California at Berkeley, who investigated a new method for Discovery and identification of dark matter in a paper published in Physical Review Letters and accessible on arXiv.
Particles that are a billion times more massive than a proton
The method, already partially presented in a previous Futura article, only applies to certain models of dark matter; However, they must be very massive particles (from around 1 to 1000 PeV, i.e. up to a billion times the mass of a proton) and cannot destroy themselves. The central idea assumes that these particles can accumulate in the hearts of neutron stars over billions of years.
Then comes the moment when the density achieved causes the collection of dark matter particles to collapse into a mini-black hole, a mini-black hole, which then swallows the entire neutron star, turning it into a black hole. However, since the work of Oppenheimer (inspired by the ideas of the legendary Russian physicist Lev Landau) and his graduate student Georges Volkoff, we know that there must be a limiting mass for the stability of a neutron star.
Modern calculations show a so-called Tolman-Oppenheimer-Volkoff limit of around 2.5 times the mass of the sun. In fact, we don’t know of any heavier neutron stars. It follows that the vast majority of stellar black holes formed by the collapse of a star exploding into a supernova cannot have a mass below this limit.
However, the discovery of two special gravitational wave sources by Ligo and Virgo, GW190814 and GW190425, suggests that they are the product of collisions of black holes, at least one of which may have had a mass below the Tolman-Oppenheimer limit. Volkoff.
Original black holes or neutron stars transformed into black holes?
These could be examples of the original black holes postulated more than 50 years ago by Hawking and Zeldovich, black holes that were formed during the Big Bang by density fluctuations in very primitive plasma. However, binary black holes could also have formed, in which at least one component results from the transformation of a neutron star proposed by astrophysicists.
In general, the existence of a population of low-mass black holes, revealed by gravitational waves accessible by existing detectors such as Kagra, but in the near future also by Ligo India, Cosmic Explorer and the Einstein Telescope, could be used for testing become hypothesis of catalysis of the conversion of neutron stars into black holes by dark matter. More specifically, in certain theories, this would place limits on the masses of dark matter particles, as well as their ability to interact, albeit very weakly, with ordinary matter other than through gravity.
In fact, some dark matter detectors couldn’t tell the difference between measuring the cosmic neutrino background and some of the theorized dark matter particles, but fortunately the very ones that could were able to transform neutron stars. Additionally, the researchers conclude that “gravitational wave detectors, which have already proven useful for directly detecting black holes and gravitational waves predicted by Einstein, could also become a powerful tool for testing black matter theories.”