The Galactic Center and M87: Observations and Interpretations

• Published in: Physics of particles and nuclei letters Vol. 20; no. 3; pp. 538 - 543
• Main Author: Zakharov, A. F.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.06.2023; Springer Nature B.V
• Subjects: Celestial bodies; Collaboration; Constraint modelling; Cooperation; Elliptical galaxies; Event horizon; Particle and Nuclear Physics; Physics; Physics and Astronomy; Physics of Elementary Particles and Atomic Nuclei. Theory; Reconstruction; Relativity; Shadows; Stars
• ISSN: 1547-4771; 1531-8567
• DOI: 10.1134/S1547477123030743

Precise observations of the trajectories of bright stars near the Galactic Center (GC) make it possible to estimate the gravitational potential, because bounded stars move along trajectories that are very close to elliptical ones. Since the position of Sgr A* is very close to the foci of the associated trajectories, astronomers conclude that the Newtonian potential is a very good approximation for the available observational data. In 2018–2019, the GRAVITY and Keck collaborations found that the gravitational redshifts for the S2 star near its passage of the pericenter correspond to the first post-Newtonian correction of general relativity (GR). In 2020, the GRAVITY collaboration found that the Schwarzschild precession for the S2 star corresponds to the GR predictions. Thus, GR has successfully passed an important test for the GC, and astronomers have gotten new confirmations of the universality of the predictions of the Einstein’s gravity law. In recent years, we have considered several versions of alternative theories of gravity and have shown that observations of bright stars make it possible to constrain the parameters of such theories. In 2019, the Event Horizon Telescope (EHT) collaboration reported on the reconstruction of a shadow at the center of galaxy M87, and in May 2022 it reported on the results of the reconstruction of the shadow at the GC. Earlier we discussed the constraints on the GC and M87* models, as well as on the theories of gravity from these observations.