New confirmation of an alternative theory of gravity obtained
An international team of physicists has made a mysterious discovery that challenges Newton’s classical law of gravity and is consistent with an alternative theory called Milgrom Dynamics (MOND). The results are published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS), and a preprint of the paper is available in the arXiv repository.
Scattered star clusters that have so-called “tidal tails” – extended groups of stars that lie outside the cluster – have been studied. Tails are formed due to the scattering of the cluster as a result of interaction with the galactic environment and due to the expansion of the parent gas cloud as a result of processes occurring within the cluster (such as stellar winds or supernova outbursts). One of the tails is the leading one, while the other, the posterior one, is directed in the opposite direction and extends behind the cluster.
Different models of gravity, evaluating the interaction of the stars inside the cluster and the cluster itself with the surrounding galactic medium, predict the asymmetry of the tidal tails in different ways. According to Newtonian gravity, the tails should be symmetrical. Astronomers have found that in five scattered clusters, the leading tails within 50 parsecs of the center contain noticeably more stars than the trailing ones, which is consistent with the MOND theory prediction.
MOND, unlike Einstein’s classical theory of gravity, does not require the presence of dark matter to explain the observed dependence of the velocity of matter in the galaxy on the distance from the nucleus. It is known that the outer regions of galaxies rotate faster than it can be expected from the Newtonian dynamics of visible (baryonic) matter composing stars, planets and gas-dust clouds. Hence, within the framework of classical theory, it follows that there must be some hidden mass or dark matter in the galaxy. But in 1983 the Israeli physicist Mordehai Milgrom (Mordehai Milgrom) proposed amendments to the Newtonian theory of gravity, according to which it turned out that the speed of stars in circular orbits does not depend on their distance from the center of the galaxy.
The asymmetry of tidal clusters is the reason for a significant reduction in the lifetime of scattered clusters. Uneven ejection of matter from the cluster leads to the fact that clusters after about 200 million years after birth begin to rotate around the center of the galaxy on an increasingly elongated orbit, simultaneously spinning in the opposite direction to the direction of the orbital rotation. As the eccentricity of the orbit increases, the cluster dissipates faster and faster.
In conclusion, the authors of the paper suggest a number of more direct ways to detect deviations from the Newtonian dynamics, for example, including the observation of a large number of double star systems, tracking the orbital motion of Proxima Centauri using high-precision astrometry and using a group of small spacecraft to map the gravitational field surrounding the Sun.