Michael Johnson

Harvard-Smithsonian, December 1, 1:00 pm

Black Hole Shadows and Photon Rings: Experimental Relativity with Radio Interferometry

By combining global networks of radio telescopes, very long baseline interferometry provides the sharpest images in astronomy. This technique has recently culminated in the first images of a black hole, produced using the Event Horizon Telescope (EHT). These images revealed dark “shadows” encircled by bright and unresolved rings for the nuclear supermassive black holes in M87 and the Milky Way. I will discuss these results, including their implications for astrophysical theories of black hole accretion and jet formation. I will then describe our efforts to develop the next-generation EHT (ngEHT) and a space-enhanced EHT over the coming decade, which will improve the dynamic range of current EHT images by two orders of magnitude and will enable studies of horizon-scale dynamics through black hole movies. These efforts can resolve the fractal substructure from unstable photon orbits near a black hole that is predicted to appear within the blurry EHT ring, and they will ultimately measure the masses of thousands of supermassive black holes across cosmic history.