The Event Horizon Telescope: Imaging a Black Hole

The Event Horizon Telescope (EHT) is a Very Long Baseline Interferometry (VLBI) array operating at the shortest possible wavelengths, which can resolve the event horizons of the nearest supermassive black holes.  Observing at mm radio wavelengths, enables detection of photons that originate from deep within the gravitational potential well of the black hole, and travel unimpeded to telescopes on the Earth.  Early observations with a proto-EHT array have revealed Schwarzschild radius scale structure in SgrA*, the 4 million solar mass black hole at the Galactic Center, and in the much more luminous and massive black hole at the center of the giant elliptical galaxy M87.  Subsequent improvements to the instrumentation and addition of new sites through an international collaborative effort led to Global observations in April 2017: the first campaign with the potential for horizon imaging.  The science goals of the EHT are to imaging strong GR signatures near the horizon, detecting magnetic field structures through full polarization observations, time-resolving black hole orbits, testing GR, and modeling black hole accretion, outflow and jet production.  This talk will review the project and discuss latest science results.