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In the new work, physicists have disputed the findings of their colleagues.
An international group of scientists have found evidence of alternative theories of gravity, which has no significant support among astronomers and physicists. According to this model, the galaxies do not possess a dark matter halo that affect the speed of stars in the outer regions. An article by researchers published in the journal Nature.
This writes with reference to rambler.ru.
According to the Newtonian theory of gravity, the speed of outer regions of galaxies should fall with distance from the center, similar to how the orbital speed of the planets becomes smaller with distance from the Sun. However, in the early 80-ies of XX century, astronomers found that stars on the periphery of galaxies have the same speed as the stars in the inner regions. The generally accepted hypothesis explains this paradox by the existence of a dark matter halo that surrounds the galaxy and the outer disperse region. However, In 1983, Israeli physicist Mordechai Milgrom (Mordehai Milgrom) proposed to amend the Newtonian theory of gravitation, of which it turned out that the velocity of stars on circular orbits does not depend on their distance from the center of the galaxy. His hypothesis became known as modified Newtonian dynamics (MOND).
In March 2018 in the journal Nature has published an article with the results of observations of the dwarf irregular galaxy NGC1052–DF2, in which there was no dark matter. Scientists have measured the speed of 10 objects in different regions of the galaxy, and found that the observed variance (dispersion around the mean value) of velocities of stars NGC1052–DF2, is almost two times lower than the values calculated in the framework of MOND and is about 20 kilometers per second.
In the new work, physicists have disputed the conclusions of his colleagues, arguing that NGC1052–DF2 is not an isolated galaxy and experiencing the gravitational influence of its neighbors. Nearby, 80 kiloparsecs, is a bright elliptical galaxy NGC1052 (both star systems removed from Earth for 20 megaparsecs). Thus, according to the researchers, the calculations in the framework of MOND it is necessary to consider the acceleration of stars under the influence of external gravitational forces.Scientists calculated the velocity dispersion (σ) for NGC1052–DF2, using the method for calculating the resultant of the gravitational forces of N bodies. it Turned out that the influence of NGC1052 reduces the variance for MOND to 15 kilometers per second, bringing it closer to the observed values. The difference between the theoretical and the measured σ was about two standard deviations and was statistically insignificant. Thus, the researchers conclude, observation is consistent with the dynamics Milgrom.