Spectroscopic Study of the S2 Star
Astrophysics Lab, Group Project (11.2025–02.2026)
NKUA, Athens
Description:
We studied the S2 star orbiting the supermassive black hole at the Galactic Centre, using its projected orbit and radial-velocity evolution to infer key orbital parameters and estimate the central black-hole mass. The project combined Keplerian orbital dynamics, coordinate transformations, numerical modelling, and the interpretation of near-infrared spectroscopic measurements.
As part of the group, I contributed to the theoretical derivation and numerical analysis of the projected orbit and radial velocity, as well as to the reconstruction of quantities such as eccentricity, inclination, semi-major axis, and central mass.
By combining characteristic features of the radial-velocity curve with the projected orbital geometry, we constrained the parameters of the S2 orbit and examined how Doppler shifts and near-infrared spectroscopy are used observationally to trace the motion of S stars. The method recovered orbital parameters close to their expected values and yielded a Galactic Centre black-hole mass of approximately 4.15×106 M☉, demonstrating how spectroscopic and astrometric information can be combined to infer the physical properties of the S2–black-hole system.
Our project included a written report as well as an oral presentation.
Normalized swept orbital area, S/(πab), as a function of the orbital angle θ for different eccentricities. The measured time interval provides the constraint used to narrow down the allowed orbital parameters of S2.
