Charon (moon)

Charon is the largest moon of the dwarf planet Pluto and was discovered in 1978 by astronomer James Christy. It is one of the largest moons relative to the size of its parent body, with a diameter of about 1,212 kilometers (about 753 miles), which is roughly half the diameter of Pluto itself. This size relationship makes Charon unique, as it forms a binary system with Pluto; they both orbit a common center of mass that lies outside of Pluto.