Phaeton was an idea of a huge planet that once orbited the Sun, but has since broken apart. It was not real, just an idea made up by scientists to explain why some of the planets in our Solar System are in the same places they are. When scientists looked at the patterns of planets in outer space, they noticed that they seemed to move in certain regular patterns. They thought that maybe these regular patterns were caused by a planet that had broken apart as it orbited the Sun. They called this planet Phaeton.