Tidal phenomena in the Galactic Center: The curious case of X7

¹ University of Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching, Germany
³ The Oskar Klein Centre, Department of Astronomy, AlbaNova, Stockholm University, 106 91 Stockholm, Sweden
⁴ Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ibáñez, Av. Padre Hurtado 750, Vina del Mar, Chile
⁵ Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes (TITANS), Chile
⁶ Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
⁷ W. M. Keck Observatory, Waimea, HI 96743, USA

^★ Corresponding authors: wasifshaqil@gmail.com; calderon@mpa-garching.mpg.de

Received: 17 April 2025
Accepted: 30 June 2025

Abstract

Context. Several enigmatic dusty sources have been detected in the central parsec of the Galactic Center. Among them is X7, located at only ~0.02 pc from the central supermassive black hole, Sagittarius A* (Sgr A*). Recent observations have shown that X7 is becoming elongated due to the tidal forces of Sgr A*. X7 is expected to be fully disrupted during its pericenter passage around 2035, which might impact the accretion rate of Sgr A*. However, its origin and nature are still unknown.

Aims. We investigated the tidal interaction of X7 with Sgr A* in order to constrain its origin. We tested the hypothesis that X7 was produced by one of the observed stars with constrained dynamical properties in the vicinity of Sgr A*.

Methods. We employed a set of test-particle simulations to reproduce the observed structure and dynamics of X7. The initial conditions of the models were obtained by extrapolating the observationally constrained orbits of X7 and the known stars into the past, making it possible to find the time and source of origin by minimizing the three-dimensional separation and velocity difference between them.

Results. Our results show that ejecta from the star S33/S0-30, launched in ~1950, can to a large extent replicate the observed dynamics and structure of X7, provided that it is initially elongated with a velocity gradient across it, and with an initial maximum speed of ~600 km s⁻¹.

Conclusions. Our results show that a grazing collision between the star S33/S0-30 and a field object such as a stellar-mass black hole or a Jupiter-mass object is a viable scenario to explain the origin of X7. Despite the uncertainties in the rate of these encounters, recent estimations show that it is plausible for such a scenario to have occurred recently.