The above 533 KB QuickTime simulation illustrates the relationship during a Leonids meteor shower between the earth, comet Tempel-Tuttle's dust field, and the constellation of Leo. The size of the earth and sun have been exaggerated for clarity. When the earth passes through Tempel-Tuttle's dust field every November 17-18, the dust particles stream into our atmosphere and burn up as meteors. The red arrow during the simulation indicates that a ground-based observer would perceive the meteors as coming from a point (called the "radiant") within Leo, hence the name Leonids.