(ORDO NEWS) — Researchers in China have studied in detail the two nearest binary systems containing a star and a stellar-mass black hole, and have found new circumstantial evidence for the existence of dense dark matter near their black holes.
The model of dynamic friction applied by the authors also made it possible to explain the behavior of companion stars much better than any other theory that does not take into account dark matter.
Dark matter does not emit or reflect light, because it does not participate in electromagnetic interaction in any way, which makes it extremely difficult to detect.
Many modern studies are aimed at finding evidence for the existence of this form of matter or methods that would allow it to be detected.
And all scientists can have is the knowledge that hypothetical dark matter particles interact with each other and other particles only gravitationally, and that there is about five times more of this invisible matter than the substance we observe.
Nevertheless, today we know about a dozen theoretical and observational proofs of the existence of dark matter.
Although all of them are indirect, each evidence allows us to learn a little more about the properties and prevalence of dark matter, as well as get closer to understanding its nature and the discovery of its constituent particles.
Another proof of the existence of dark matter was proposed by a duet of astrophysicists from the Hong Kong University of Education (PRC).
The scientists chose the two nearest X-ray binary systems, consisting of a stellar-mass black hole and a companion star, A0620-00 and XTE J1118+480, as objects of study.
Systems located at three and six thousand light-years from the Sun are active and emit X-rays when matter from a companion star falls onto a black hole.
As they orbit their black holes, the companion stars gradually slow down at a rate of about one to two milliseconds per year, according to astronomers.
However, the standard theoretical estimate gives a value two orders of magnitude lower, namely 0.02 milliseconds per year.
At the same time, taking into account possible magnetic braking or the influence of tidal forces does not provide the desired result and also disagrees with observational data.
In the new study, the authors decided to apply a dynamic friction model to dark matter to try to explain this discrepancy between the theory and observations, and at the same time to find out whether there are bursts of dark matter density near stellar-mass black holes.
The essence of the model is that a star moving in a dense medium of dark matter particles will gravitationally attract them, creating an increased concentration of particles behind it.
This even denser collection of dark matter particles, in turn, will have a collective gravitational effect on the star, slowing it down.
The effect of dynamic friction was proposed more than 70 years ago by the Nobel Prize-winning astrophysicist Subramanyan Chandrasekhar and, to the surprise of the authors of the study, it had not previously been applied to such systems.
But it is precisely in the case under consideration that this effect made it possible to obtain the closest values ​​of the deceleration rate of the companion star to the observed ones.
In the future, the researchers hope to apply this model to other binary systems, of which there are at least 18 in our Galaxy alone.
According to the authors of the work, the study of such systems can provide more information, which in the future will finally unravel the mystery of dark matter.
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