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

## TL;DR

This study confirms the relativistic redshift effect on star S0-2 near the Galactic center's black hole, supporting General Relativity with high statistical significance through combined spectroscopic and astrometric data.

## Contribution

It provides the first measurement of relativistic redshift for S0-2, combining multiple data sets to test predictions of General Relativity in a strong gravitational field.

## Key findings

- Relativistic redshift detected at 5 sigma significance.
- Measurement of the redshift parameter $$ close to GR predictions.
- Consistent results with Einstein's theory of gravity.

## Abstract

General Relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. We test this using observations of the Galactic center star S0-2. We combine existing spectroscopic and astrometric measurements from 1995-2017, which cover S0-2's 16-year orbit, with measurements in 2018 March to September which cover three events during its closest approach to the black hole. We detect the combination of special relativistic- and gravitational-redshift, quantified using a redshift parameter, $\Upsilon$. Our result, $\Upsilon=0.88 \pm 0.17$, is consistent with General Relativity ($\Upsilon=1$) and excludes a Newtonian model ($\Upsilon=0$ ) with a statistical significance of 5 $\sigma$.