Pluto from Charon. Artwork of Pluto seen from the cratered ice and rock surface of its moon Charon. Pluto is the most distant planet of the solar system, circling the Sun at a distance of around 6 billion kilometres every 248 years. Charon is only half its size, making this a double planet system. Little is known about these worlds, which are yet to be visited by spacecraft from Earth. Pluto has a diameter of less than 2300 kilometres, by far the smallest planet, and has an extremely eccentric orbit around the Sun. Some astronomers do not consider Pluto to be true planet, instead classifying as part of the nearby Kuiper Belt of small rocky, icy bodies.