Discovery of Charon

Charon was discovered by the American astronomer James Christy, who noticed on photographic plates taken at the United States Naval Observatory station in Flagstaff, Arizona, that the image of Pluto seemed to have a bulge that moved periodically. He realised that the bulge was a large moon. Charon is about half the diameter of Pluto, so large that the two bodies orbit a point in space above Pluto's surface, and they are often described as a double dwarf planet. The moon was named after the ferryman of the dead in Greek mythology, and the name also echoed Christy's wife Charlene. Charon allowed astronomers to measure the mass of Pluto for the first time, and in 2015 the New Horizons probe revealed a surface with canyons and a dark polar cap.

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