ESO Science Release | GRAVITY | 2018 Oct 31
ESO’s GRAVITY instrument confirms black hole status of the Milky Way centre
ESO’s GRAVITY instrument on the Very Large Telescope (VLT) Interferometer has been used by scientists from a consortium of European institutions, including ESO , to observe flares of infrared radiation coming from the accretion disc around Sagittarius A*, the massive object at the heart of the Milky Way. The observed flares provide long-awaited confirmation that the object in the centre of our galaxy is, as has long been assumed, a supermassive black hole. The flares originate from material orbiting very close to the black hole’s event horizon — making these the most detailed observations yet of material orbiting this close to a black hole.
While some matter in the accretion disc — the belt of gas orbiting Sagittarius A* at relativistic speeds  — can orbit the black hole safely, anything that gets too close is doomed to be pulled beyond the event horizon. The closest point to a black hole that material can orbit without being irresistibly drawn inwards by the immense mass is known as the innermost stable orbit, and it is from here that the observed flares originate. ...
Hotspot Discovery Proves Black Hole Theory
University of Waterloo | 2018 Oct 31
Detection of Orbital Motions Near the Last Stable Circular
Orbit of the Massive Black Hole Sgr A* ~ GRAVITY Collaboration