Probing Post-Newtonian Physics near the Galactic Black Hole with Stellar Redshift Measurements

Stars very close to the massive black hole (MBH) in the center of the Galaxy allow us to probe post-Newtonian (PN) physics in a yet unexplored regime of celestial mechanics. Recent advances in infrared spectroscopy enable us to take precise measurements of stellar redshift curves and thereby detect 𝒪(β2) PN effects (gravitational redshift in the MBH's potential and the transverse Doppler shift). We use simulations to show that these effects can be decisively detected with existing instruments after ~10 years of observations. We find that neglecting these effects leads to statistically significant systematic errors in the derived MBH mass and distance.