Pluto: Moons

Pluto has only one known moon, Charon.

Charon

Icy and cold, Charon shares some characteristics with Pluto. It was discovered in 1978 and measures 1,270 km in diameter, making it almost half as large as its planet. Charon (named after the Roman ferryman of the dead) is a bright blue, possibly because of the large amounts of water ice on its surface. Researchers once believed Charon to be no more than a piece of Pluto, but the drastic differences in their compositions now suggest otherwise. The average density of Charon is 1,200 to 1,300 kg/m³, just more than half of Pluto's density. Its geometric albedo ranges from 0.36 to 0.39 as compared with Pluto's 0.49 to 0.66. Charon could, perhaps, be an accumulation of lighter materials from an ancient collision.
Charon's rotation is synchronous with that of Pluto, completing one rotation in 6.4 Earth days. Since the two bodies are tidally locked to each other, both satelittes always show each other the same side. The radial distance between Pluto and its moon is 19,600 km. Charon is approximately 1.3 x 10²² kg and has no large light-reflective features.

Copyright © 2000 by Gary Chan and Matthew McDermott. All rights reserved.