The above 400 KB QuickTime simulation illustrates the orbits of comet Tempel-Tuttle, Earth, and Jupiter from 1997-1999. The motion of the comet and planets are correct but their sizes have been exaggerated for clarity. Comet Tempel-Tuttle orbits the sun every 33 years and most recently passed near Earth in spring 1998. Like all comets, Temple-Tuttle is composed of ice and dust. As the sun slowly melts the ice, the comet's dust breaks off and spreads along the orbital path. Earth passes through Tempel-Tuttle's orbital dust field every November 17-18, causing the Leonids meteor shower.