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Leonids

The Leonids are a prolific meteor shower associated with comet Tempel-Tuttle. This shower is exceptional every 33 years, when the Earth passes through the densest region of cometary dust. Their radiant - the point in the sky from which the Leonids appear to come - is the constellation Leo, the lion, near the bright star Regulus. This is where the shower's name comes from.

Leonids are also known for their fireballs and earthgrazer meteors. Fireballs are larger explosions of light and color that can persist longer than an average meteor streak. This is due to the fact that fireballs originate from larger particles of cometary material. Fireballs are also brighter, with magnitudes brighter than -3. Earthgrazers are meteors that streak close to the horizon and are known for their long and colorful tails.

The Leonids, which peak during mid-November each year, are considered to be a major shower, even though meteor rates are often as low as about 15 meteors per hour. The Leonids are bright meteors and can also be colorful. They are also fast: Leonids travel at speeds of 71 km (44 miles) per second, among the fastest known.

Every 33 years, or so, viewers on Earth may experience a Leonid storm that can peak with hundreds to thousands of meteors seen per hour depending on the location of the observer. A meteor storm versus a shower is defined as having at least 1,000 meteors per hour. Viewers in 1966 experienced a spectacular Leonid storm: thousands of meteors per minute fell through Earth's atmosphere during a 15 minute period. There were so many meteors seen that they appeared to fall like rain. The last Leonid meteor storm took place in 2002.

The pieces of space debris that interact with our atmosphere to create the Leonids originate from comet 55P/Tempel-Tuttle. It takes comet Tempel-Tuttle 33 years to orbit the sun once.