Lesser numbers of Leonids will be visible for about a week around the dates of the peak. If the weather cooperates by providing a clear sky, viewing conditions will be ideal on Nov. 17 and 18. The moon will be new, so moonlight will not interfere in the early morning hours when the constellation Leo the Lion will rise in the east. The meteor shower seems to come from a point in Leo, which gives the Leonids their name. This is when Earth will cross the orbit of Comet Tempel-Tuttle, the comet that provides the particles from which the Leonid meteors actually come.
Most meteor showers happen when Earth crosses the orbit of a comet.
The meteors are caused by tiny particles of dust that were released from the comet's nucleus and left behind in space as the comet got closer to the sun. As Earth plows through this stream of particles, each one collides with our upper atmosphere at tremendous speed and burns up almost instantly from friction with air molecules. Comet Tempel-Tuttle passed by Earth's orbit in March of this year, so there is a chance that thousands of meteors and fireballs will appear to stream from Leo as in the great Leonid storms of the past. However, any meteor storm will last no more than a few hours and perhaps less than one hour. Only observers in the region of the planet that is facing into the particle stream and also in darkness will be able to see the storm when it hits.