Optical interferometry just recently came to an age with the transformative results brought up by GRAVITY at the VLTI, on topics such as exoplanets, active galactic nuclei (AGN) and the Galactic Center. The next stage is already upcoming with GRAVITY+, a series of upgrades of the instrument and the infrastructure. With laser-assisted, extreme adaptive optics for each unit telescope and...
The continuous monitoring of stellar orbits in the Galactic Centre over the past few decades revealed the massive central object Sgr A at their shared focal point (→ Nobel prize 2020). These and other observations (orbits of hot flares, black hole shadow) are in best agreement with the notion of Sgr A being a massive black hole of about 4 million solar masses. Assuming the black hole model,...
