The central region of the Milky Way, consisting of billions of stars, slowed its rotation by a quarter from the moment of its formation due to the influence of dark matter. Scientists of University College of London and Oxford University, who published an article in MONTHLY NOTICES OF THE ROYAL ASTRONOMOMICAL SOCIETY, came to this conclusion. Scientific work not only proves the existence of an invisible substance in the form of a halo surrounding the galaxy, but also rejects alternative gravity theories that are trying to explain the dynamics of stars in the Milky Way without attracting dark matter.
Researchers analyzed the data obtained by the GAIA telescope about the metallicity of the stars in the center of the Galaxy. Metal movements shows how many stars are enriched with metals, that is, elements of hydrogen and helium (in astronomy, metals may be called elements that are not metals from the point of view 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 – a dense extended area of stars and gas, from which the branches of the Milky Way are diverted. In turn, the jumper affects a galactic disk through orbital resonances, when the periods of stars around the center become commensurate at the speed of rotation of the jumper itself. When the jumper slows down, more and more disk stars become involved in the orbital resonance with the bar. At the same time, the captured stars are trapped, and those that have fallen into the resonance earlier should have a greater average mettle. Thus, on the distribution of metallicity within the resonant region, it is possible to measure how much the speed of rotation of the jumper has changed.
Scientists determined that the speed of rotation of the jumper is 35 kilometers per second per one kiloparsk, and the boundary of the resonance coincides with the orbit of the stream of Hercules. Star stream is a strip of stars that were previously part of the ball cluster, but stretched along the orbit under the action of the tidal forces of the galaxy. In addition to confirming the theory of the slow bar, this measurement demonstrates the drop in the jumper speed by more than 24 percent from the date of its formation.
According to scientists, the slowdown is explained by the friction of the jumper on the accumulation of dark matter in the galactic haloe, and the results of the observation make it possible to measure the inert mass of the invisible substance, which affects the speed of rotation of the Galaxy Center. This will allow you to establish limitations both on various models of dark matter, and reject alternative gravity theories that do not recognize dark matter and do not predict slowing the rotation.