Millimeter VLBI has become a reality and sub-millimeter VLBI will be possible in the very near future. These techniques make possible the imaging of supermassive black hole horizons in at least two systems, Sgr A* and M87. Already results have been obtained that have importance for fundamental gravitational physics: whether or not black hole horizons exist. Future observations promise to test whether or not the Kerr metric is an adequate description of strong gravity in the vicinity of supermassive black holes. In addition, such observations are being brought to bear upon unresolved astrophysical questions surround black hole accretion and outflows, providing critical observational input into jet-formation physics as well as the inner structure of black hole accretion flows. I will discuss how these observations are being done, how they may be optimized in the near future using existing observatories, what we expect to see and how they may be used to address fundamental questions in black hole science.
Host: Eric Poisson