What does a black hole look like? To find out, radio telescopes from around the Earth coordinated observations of black holes with the largest known event horizon s on the sky. Alone, black holes are just black , but these monster attractors are known to be surrounded by glowing gas. This first image resolves the area around the black hole at the center of galaxy M87 on a scale below that expected for its event horizon . Pictured , the dark central region is not the event horizon, but rather the black hole's shadow -- the central region of emitting gas darkened by the central black hole's gravity. The size and shape of the shadow is determined by bright gas near the event horizon , by strong gravitational lensing deflections , and by the black hole's spin. In resolving this black hole's shadow , the Event Horizon Telescope (EHT) bolstered evidence that Einstein's gravity works even in extreme regions , and gave clear evidence that M87 has a central spinn...