Discovery of Charon, Pluto's Moon

Date: June 22, 1978 • Location: Adams Morgan, United States

Charon, the first of Pluto's satellites to be discovered, was first seen at the United States Naval Observatory by James W. Christy.

Charon, formal designation (134340) Pluto I, is the largest of the five known natural satellites of the dwarf planet Pluto. It has a mean radius of 606 km (377 mi). Charon is a planetary-mass moon and the sixth-largest known trans-Neptunian object after Pluto, Eris, Haumea, Makemake, and Gonggong. It was discovered in 1978 at the United States Naval Observatory in Washington, D.C., using photographic plates taken at the United States Naval Observatory Flagstaff Station (NOFS).