Quick overview of Pluto and Charon

Percival Lowell predicted the existence of a planet beyond Neptune based on slight irregularities in the orbits of Uranus and Neptune. Based on these predictions, Clyde Tombaugh discovered Pluto in 1930.

Charon - Pluto's moon - was discoverd in 1978. Charon's surface is much darker than Pluto. It is probably covered with dirty water ice. Pluto and Charon always keep the same surface areas turned towards each other - just like the Earth and the Moon.

Charon does not really orbit around Pluto. Pluto and Charon together orbits each other around a shared central point - their barycenter. (Barycenter: a common center of mass around which two or more bodies revolve).

Scientists sometimes call Pluto and Charon a double planet, since Charon is nearly half the size of Pluto.

Pluto and Charon orbit the Sun in the Kuiper belt (Picture of the Kuiper Belt). Objects that orbit the Sun at this distance are also called trans-Neptunian objects OR Edgeworth-Kuiper Disk objects OR ice dwarves.

Pluto has a very elliptical orbit. From 1979 to 1999 the planet Neptune was actually the furthest planet from the Sun. Here is a drawing of pluto's orbit and a press release by NASA about Pluto's orbit.

Pluto has a VERY thin atmosphere. Its atmospheric pressure is about 100,000 times less than Earth's atmospheric pressure at sea level.

Pluto has large frozen ice caps. When it is closest to the Sun in its orbit, the ice caps evaporate to create the atmosphere

The rest of this website has pictures of Pluto and Charon as well as an interactive quiz.

Go back to the planet Pluto home page to have a look at those pictures.

Sources
Microsoft® Encarta® Encyclopedia 2002
Oxford Paperback Encyclopedia, © Oxford University Press 1998