INTRO:
       Charon is the only known satellite of Pluto. Its discovery helped us learn more about Pluto and led to a better understanding of the farthest planet from the Sun. Charon orbits 19,640 kilometers from Pluto, has a diameter of 1172 kilometers, and a mass of 1.9 x 10e21 kilograms. It is the largest moon in respect to its primary planet (one half Pluto's size), a distinction the Earth's moon once held. Prior to its discovery, Pluto was believed to be much bigger than it actually is. This is because photographs blurred Pluto and Charon together. Several things about Charon make it unique among the moons of the solar system. Charon is in synchronous orbit with Pluto. The same faces of Pluto and Charon face each other year round. From Pluto's point of view, Charon remains constant while all the stars in the sky move around, completing an orbit every 6.26 days. The angular size of the moon from Pluto's point of view is 4° wide, eight times the size of the moon on Earth. It is also believed that Pluto, Charon, and Triton, one of Neptune's moons, could actually be related to each other and are actually satellites for a bigger planet, such as Neptune.

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DISCOVERY:
       Charon was discovered by James W. Christy almost by accident. While studying pictures in an attempt to gain more knowledge on Pluto's orbit, Christy noticed a moving bulge. In one picture, it was in one position. In the next picture, the bulge had moved. Christy took this moving bulge to mean that Pluto had a satellite. More photographs verified the results. In keeping with the theme of death (Pluto is the god of the underworld.), Charon was named after the boatman who ferries the souls of the dead across the Styx River to the underworld. Christy also picked this name because it sounded much like his wife's nickname, Char. This is also the cause of Charon's informal pronounciation as "SHAR- en".

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THEORIES:
       Charon was long believed to be a double planet with Pluto. Now, scientists believe that Pluto, Charon, and Triton might actually be related to each other. Because of similarities in their nature of orbits and bulk properties, Triton, Pluto and Charon are believed to share a history. Several theories exist. One theory believes that Pluto might actually be a satellite of Neptune. The more popular theory involves Triton once being like Pluto, orbiting in an independent orbit around the sun, but was eventually captured by Neptune's gravity field. Another theory maintains that Triton, Pluto, and Charon are the only remaining members of a large class of similar objects. The rest were ejected into the Oort Cloud.
       Another theory is based on the idea that Charon and Pluto actually originated from the same body of mass. The mean density of Charon and Pluto are much higher than the ice moons of Saturn and Uranus. Pluto and Charon only composed of 30% ice. The rest is composed of rock. This is highly unusual given their distance from the sun. One would expect them to be icier. Scientists believe this unusual occurrence is because of how Charon was formed. Some scientists believe that if Charon was created from a collision that occurred AFTER the rocky center of Pluto had settled, most of the material blown off would have been the ice. This would explain why Charon is icier than Pluto, but why both Charon and Pluto are not as icy as the ice moons.
       There is, however, another theory that argues against the idea that Charon is actually the result of Pluto's collision with another celestial body. Because Charon has a density between 1.2 to 1.3 g/cc and Pluto's density is higher at 1.8 to 2.1 g/cc, scientists believe that Charon is not very solid, containing small to no amount of rock. Pluto, on the other hand, is more solid and probably contains more rock. This reputes earlier theories that Pluto and Charon split from the same original mass after Pluto collided with another celestial body.

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