Pluto's Orbit. You may be wondering why Pluto does not collide with Neptune, since their orbits are close. This is because their orbits are in resonance. Pluto orbits the Sun twice for every 3 orbits of Neptune. As a result, Pluto and Neptune are never very close to each other. This is a program which illustrates the resonance of their orbits. The left diagram is the usual map of the solar system looking down from above the Sun. The right diagram has been made by keeping Neptune and the Sun fixed - the planets are then allowed to follow their orbits over thousands of years. You will see Pluto's eccentric orbit maps out a strange, curly path - but never comes close to Neptune. With this program, one can draw images to see the effect of the Pluto - Neptune resonance. You can easily test the effects of several parameters by changing them and redrawing the image. It's best to use the highest colour settings in windows for the optimal results.

This image was created with the program using the default values.