Although the Earth passes close to the orbit of Tempel-Tuttle every year, usually not much happens. The Earth plows through a diffuse cloud of old comet dust that shares Tempel-Tuttle's orbit, and the debris burns up harmlessly in Earth's atmosphere. Where to View Go to an open area, away from trees and city light. Allow 30 minutes for your eyes to adjust to darkness. But every 33 years, astronomers calculate, a spectacular Leonids storm can occur after the comet swoops near the sun, shrugging off layers of dusty, icy particles the size of Rice Krispies.
Earth plows straight through the comet's refreshed wake.
Astronomers believe the 1999 edition of the Leonids probably won't equal 1966, which peaked at 144,000 meteors per hour. But it is likely to be a meteor downpour of 2,000 to 6,000 meteors per hour. Tempel-Tuttle visited the inner solar system most recently in late 1997 and early 1998. Apparently, the Earth crossed Tempel-Tuttle's orbital plane too early to generate a true storm. And it may be a century before they get another chance.