The Solar System

What is unusual about Pluto's moon?
Answered by Science Channel
  • Science Channel

    Science Channel

  1. Pluto has one moon, named Charon. While Pluto is smaller than our own moon, and has a diameter of around one-fifth that of the Earth, Charon is more than half as big as Pluto is! Pluto and Charon are closer in size to each other than any other planet-moon pair in our solar system. As Charon orbits around Pluto, it keeps the same side facing it while Pluto keeps the same face toward its moon. This is the only example in our solar system of a planet and moon locked into rotation in this manner. Some people entertain the possibility that Pluto is really a former moon of Jupiter, which escaped its gravitational pull, or an asteroid, which was attracted by the sun into orbit. According to these theories, Charon could be thought of as a moon of a moon or a moon of an asteroid, but other scientists describe Pluto and Charon as two small planets rotating around each other.

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