You're lucky, this is about the last question the the scientists will answer this school year. We asked Pierre Kerr, ac210@freenet.carleton.ca, to enlighten us.

There are lots of good books in your school library about the planets, but since school is almost over, here are some facts for you.

Pluto was predicted to exist in 1905 by observing irregularities in Uranus' orbit. It was actually seen by Clyde Tombaugh in 1930. Pluto's moon, Charon, was discovered by James Christy in 1978.

The temperature on Pluto is very cold. It varies from -223C to -233C. The reason it's so cold is because it's so far from the Sun. It's average distance from the sun is almost 6 billion kilometres. At that distance, the sun just looks like a very bright star and Pluto would receive hardly any warmth from it. Pluto, unlike some of the giant planets, does not generate any heat itself.

There has recently been the discovery of a comet belt just outside of Uranus' orbit. If Pluto were discovered today, it would not be considered a planet, but a comet.

Thanks for your questions and have a good summer.