The central region of the Milky Way, made up of billions of stars, has slowed its rotation by a quarter since its formation due to the influence of dark matter. This is the conclusion reached by scientists at University College London and Oxford University, who published an article in the journal Monthly Notices of the Royal Astronomical Society. Scientific work not only proves the existence of invisible matter in the form of a halo surrounding the Galaxy, but also rejects alternative theories of gravity, which are trying to explain the dynamics of stars in the Milky Way without the involvement of dark matter.
The researchers analyzed data obtained by the Gaia telescope on the metallicity of stars at the center of the Galaxy. Metallicity shows how enriched stars are in metals, that is, elements heavier than hydrogen and helium (in astronomy, metals can be called elements that are not metals in terms of chemistry). It is known that the metallicity decreases with increasing distance from the center of the Galaxy.
According to galactic models, the presence of dark matter should slow down the rotation of the jumper, the dense, extended region of stars and gas from which the Milky Way branches off. In turn, the cofferdam affects the galactic disk through orbital resonances, where the periods of stellar rotation around the center become commensurate with the rotation speed of the cofferdam itself. When the jumper slows down, more and more stars of the disk become involved in orbital resonance with the bar. At the same time, the captured stars are trapped, and those that are caught in the resonance earlier must have a larger average metallicity. Thus, the distribution of metallicity within the resonance region can be used to measure how much the jumper velocity has changed.
Scientists have determined that the lintel rotation rate is 35 kilometers per second per kiloparsec, with the resonance boundary coinciding with the orbit of the Hercules flow. The stellar flow is a band of stars, which were previously part of the globular cluster, but stretched out along the orbit under the tidal forces of the Galaxy. In addition to confirming the slowed-bar theory, this measurement demonstrates a drop of more than 24 percent in the velocity of the lintel since its formation.
According to the scientists, the deceleration is explained by the friction of the jumper against clusters of dark matter in the galactic halo, and the observations allow us to measure the inert mass of invisible matter, which affects the rotational speed of the center of the Galaxy. This will make it possible both to set limits on various models of dark matter and to reject alternative theories of gravity that do not recognize dark matter and do not predict the slowing down of rotation.