Charon

Pluto's moon · dwarf planet · distant ice world · space discovery

Pluto's giant moon. Charon is the largest of five moons that orbit Pluto, with a radius of about 377 miles. It's so big that Pluto and Charon orbit around each other rather than Pluto simply holding Charon in place like our Moon does with Earth.

Far and frozen. Charon is a trans-Neptunian object, meaning it orbits even beyond Neptune, the farthest main planet in our solar system. It's an icy world in the cold, distant regions of space beyond Pluto.

Discovered in 1978. Astronomers found Charon using photographic plates at an observatory in Washington, D.C. in 1978, which was nearly 50 years after Pluto itself was discovered.

Planetary-mass moon. Charon is so massive that scientists call it a planetary-mass moon, meaning it's almost big enough to be its own planet. It's the sixth-largest trans-Neptunian object we know about, after Pluto and four other icy dwarf planets.

A balanced pair. Because Charon is so large compared to Pluto, the two bodies are locked together by gravity in a special way. Instead of one orbiting the other, they both orbit around a point in space between them, like two ice skaters spinning together.