Shep Doeleman
Harvard University
“The Event Horizon Telescope: Using Radio Interferometry to Image a Black Hole”
The Event Horizon Telescope 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 millimeter radio wavelengths enables detection of photons that originate from deep within the gravitational potential well of the black hole, and which travel unimpeded to telescopes on the Earth. The primary goal of the Event Horizon Telescope is to resolve and image the predicted ring of emission formed by the photon orbit of a black hole and to eventually track dynamics of matter as it orbits close to the event horizon. A sustained program of improvements to VLBI instrumentation and the 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. After two years of data reduction and analysis we report success: we have imaged a black hole. The resulting image is an irregular but clear bright ring, whose size and shape agree closely with the expected lensed photon orbit of a 6.5 billion solar mass black hole. This talk will cover the project background and first results as well as some future directions that will sharpen our imaging capability and produce real-time movies of black hole accretion within the next decade.