Relativistic redshift of the star S0-2 orbiting the Galactic center supermassive black hole

Do, Tuan; Hees, Aurelien; Ghez, Andrea; Martinez, Gregory D.; Chu, Devin S.; Jia, Siyao; Sakai, Shoko; Lu, Jessica R.; Gautam, Abhimat K.; Kosmo O'Neil, Kelly; Becklin, Eric E.; Morris, Mark R.; Matthews, Keith; Nishiyama, Shogo; Campbell, Randy; Chappell, Samantha; Chen, Zhuo; Ciurlo, Anna; Dehghanfar, Arezu; Gallego-Cano, Eulalia; Kerzendorf, Wolfgang E.; Lyke, James E.; Naoz, Smadar; Saida, Hiromi; Schödel, Rainer; Takahashi, Masaaki; Takamori, Yohsuke; Witzel, Gunther; Wizinowich, Peter

August, 2019

The general theory of relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. In this study, we used observations of the Galactic Center star S0-2 to test this prediction. We combined existing spectroscopic and astrometric measurements from 1995─2017, which cover S0-2’s 16-year orbit, with measurements from March to September 2018, which cover three events during S0-2’s closest approach to the black hole. We detected a combination of special relativistic and gravitational redshift, quantified using the redshift parameter ϒ. Our result, ϒ = 0.88 ± 0.17, is consistent with general relativity (ϒ = 1) and excludes a Newtonian model (ϒ = 0) with a statistical significance of 5σ.