GRAVITY and the Galactic Centre

On a clear night, our home galaxy, the Milky Way, is visible as a starry ribbon across the sky. Its core is located in the constellation of Sagittarius, approximately where the bright glow is interrupted by the darkest dust filaments. There, hidden, lies a massive black hole. To peer through the obscuring clouds and see the stars and gas near the black hole we use GRAVITY. The main GRAVITY results are the detection of gra- vitational redshift, the most precise mass- distance measurement, the test of the equivalence principle, and the detection of orbital motion near the black hole.