|Diameter||2274 km, 0.18 x Earth's|
|Average Distance from Sun||5900 x 106km = 39.44 AU|
|Colour||Unknown. Possibly grey.|
|Temperature||Probably between -228°C and -238°C|
|Atmosphere||Probably nitrogen, carbon monoxide and methane|
|Length of Day||6.39 days|
|Length of Year||247.7 years|
|No. of Moons||1|
Pluto is the smallest and most distant planet in the Solar System. It is so small that many astronomers think that it is not a planet at all but part of a huge band of rocky objects at the edge of the Solar System called the Kuiper Belt.
Pluto is the only planet not to have been visited by a spacecraft. This means that we don't know much about it.
Plutoís moon, Charon, is very unusual because it is about half the size of the planet. It is closer in size to its planet than any other moon in the Solar System.
Pluto is so far away from the Sun that it gets no proper daylight like we do here on Earth. Instead the Sun just looks like a very bright star in Plutoís sky. This also means that the planet gets very little heat. It is so cold that itís atmosphere is probably frozen, and the atmosphere only turns into a gas when the planet gets closest to the Sun.
Pluto is usually the furthest planet in the Solar System, but its orbit is so oval that it sometimes gets closer to the Sun than Neptune. Between 1979 and February 1999 Neptune was the furthest planet from the Sun. Plutoís orbit is also very unusual because it is at a steeper angle than the other planets.
Authors: Carolyn Brinkworth and Claire Thomas
Last updated: July 2001