The Curious Little World of Pluto

Pluto is the smallest of the planets, and also one of the most puzzling. It is so far from the sun that it takes almost 248 years to complete one orbit; it is made up of a mixture of rock and ice; it has an extensive though thin atmosphere; and it is attended by a companion. This autumn Pluto reaches its closest point to the sun, and Patrick Moore takes the opportunity to sum up what is known about this curious little world.