A giant blob of dark matter with a mass between 20 and 60 million Suns may be lurking near our Solar System. Very close, only 2340 light years away. Scientists from the University of Wisconsin in Milwaukee (USA) hope that they have finally discovered the first cluster of dark matter in our galaxy and that it is located exactly near our star. “MK” asked to clarify the research methods of experts from the Space Center of the Lebedev Institute of Physics.
Dark matter is a cosmic object, an invisible structure of the Universe, that does not emit electromagnetic radiation. So scientists cannot see it by direct observation. Meanwhile, there is a version that it is dark matter that creates the gravitational effect, causing galaxies to rotate at almost the same speed both in the inner and outer regions, that is, as a single whole. This contradicts the situation in our own Solar System, where such uniformity does not seem to exist – for example, Mercury, located closer to the center of mass, rotates faster, and all the outer planets – slower…
A popular hypothesis says that dark matter must be spread across the entire region of a galaxy in some uniform “layer” (this is thought to give a uniformity effect). Localized sites, i.e. denser haloes of dark matter (or subhalos), if they exist, are located on the outskirts of the Universe, and it is with them that the initial formation of galaxies in the Universe is associated – already 1–2 hundred million years after the Big Bang.
And now, such a predicted subhalo is found nowhere, but not far from our solar system, at a distance of 2340 light years from the Sun, which by cosmic standards is very close. Its mass is about 20–60 million solar masses. And they helped “discover” its pulsars, discovered in 1967. These are massive neutron stars that spin rapidly around their axis, making about 1 revolution per second. At the same time, they emit a powerful beam of radio waves in the form of a spotlight, and scientists record it on Earth using radio telescopes.
As explained to MK at the Cosmic Space Center of the Lebedev Institute of Physics, when detecting dark matter halos, scientists used signals coming from so-called binary pulsars. As a rule, if a pulsar in such a pair rotates with a period of 1 second, then its companion will rotate much faster – at a speed of about a thousand revolutions per second. It is the most important object to observe, since the faster it rotates, the more convenient it is to detect the hyperfine effects associated with its deceleration (caused by manifestations of relativity, radiation of gravitational waves, etc.). According to a study by American scientists from Milwaukee, the light beam from such a millisecond pulse slows down. Surname stated in the Physical Review Letters article that its change in speed can be explained by the presence of visible matter, i.e. baryonic matter, but it was not detected in the research area (this was verified by comparing the location of the mysterious object with maps of stars, gases and other objects of ordinary matter).
Therefore, scientists concluded that the change in rotation speed of fast pulses cannot be explained by anything other than the presence of some invisible massive object along the path of its rays, or a halo of dark matter. The researchers studied objects PSR J1640+2224 and PSR J1713+0747. Pulsars in these binary systems exhibit strange gravitational deflections that occur synchronously.
Professor Philip Chang, one of the paper's authors, said: “There are a few pulsars, other objects near them and something in this region is pulling these pulsars in a strange direction that we didn't expect.”
Thus, the picture appears as follows: galaxies are immersed in thin clouds of dark matter – haloes, in which smaller subhalos are scattered (essentially condensations of dark matter). And one of these subaglos is not very far from us.
I wonder if there is any other version? According to Russian scientists, despite the fact that people are actively discussing all kinds of news related to dark matter, the fact of its existence in any form (halo or subhalo) has not yet been convincingly proven. One of the arguments that it may not exist at all is the absence of signs of it in the Solar System. About 10–15 years ago there was still a fairly large group of physicists who believed that the effects of dark matter could be explained by other phenomena: for example, the curvature of space, the special geometry of vast space, etc. But this proportion has recently gradually decreased – the hypothesis of the existence of dark matter has almost become the main hypothesis of scientists.
According to the authors of the paper, now, after the first discovery of dark matter subhalos, they have set themselves the goal of mapping the sky as many of these subhalos throughout the Galaxy as possible.
