This picture shows Pluto (left) and its big moon Charon (right). This picture was taken by the Hubble Space Telescope in 1994.
Click on image for full size
Image courtesy Dr. R. Albrecht (ESA/ESO Space Telescope European Coordinating Facility) and NASA.

Charon - Pluto's biggest moon

Charon is a moon of Pluto. Pluto has moons. Charon is much bigger than Pluto's other moons. James Christy discovered Charon in 1978.

Charon is nearly as big as Pluto. Some astronomers call Pluto and Charon a "double planet". Charon is also very close to Pluto. Because Charon is so close, it goes around Pluto fast. It only takes Charon about six days to orbit Pluto. It takes our Moon a month to go around Earth!

Did you know that we can only see one side of our Moon from Earth? That's because the Moon spins around in exactly the same amount of time it takes it to orbit Earth. The same thing is true for Charon and Pluto. Someone on Pluto could only ever see one side of Charon. Now here's the really strange part. Pluto also spins exactly as fast as Charon. So if you were on one side of Pluto, Charon would always be up in the sky. If you were on the other side of Pluto, you would never see Charon at all!

Charon is made of rock and ice, like Pluto. Some astronomers think Charon formed when a large object crashed into Pluto. That is a lot like how scientists think Earth's moon formed. Other scientists aren't quite so sure that Charon was formed that way.

Charon is named after a character from Greek mythology. Charon was the ferryman of the dead. He took people who had just died across a river in a boat. He took them to Hades, the underworld. Hades was also the name of the god of the underworld. In Roman mythology, Hades was called Pluto.

Last modified January 23, 2006 by Randy Russell.

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