Detection of Intrinsic Source Structure at ~3 Schwarzschild Radii with Millimeter-VLBI Observations of SAGITTARIUS A*
Ru-Sen Lu et al 2018 ApJ 859 60
Very long baseline interferometric observations of the supermassive black hole in the galactic center, Sgr A*, suggest the presence of compact intrinsic source structure on scales of ~3 Schwarzschild radii.