Charon is Pluto's largest moon (1 photo)

Pluto's largest moon, Charon, has an average diameter of approximately 1,212 kilometers. For comparison, Pluto itself has an average diameter of 2,376.6 kilometers. This image was acquired on July 14, 2015, by NASA's New Horizons spacecraft.



Charon's mass is approximately 12% that of Pluto (the Moon is only 1.2% the mass of Earth). Because of this large moon-to-dwarf planet ratio (≈0.12), the center of mass of the Pluto-Charon system lies outside Pluto. In the case of the Earth-Moon system, the center of mass is located inside our planet, at a depth of approximately 1,700 kilometers from the surface, which is typical for a "classical" pair: a main body and a significantly lighter satellite.

Pluto and Charon don't fit this framework, leading scientists to debate whether Charon is simply a satellite or the second full-fledged component of a binary dwarf planet system.