The comet swings through the inner Solar System every 33 years, laying down a trail of dust as it goes. It was last here in 1988. The Leonids are caused when the Earth passes through the dusty debris that follows the comet's orbit. Most particles are no bigger than a grain of sand. These hit the Earth's atmosphere at up to 70km per second.
More impressive fireballs are meteors that are just a few centimetres in diameter.
The fireball lit up the sky over North America Scientists have revealed new data about a meteorite that could be one of the most primitive Solar System objects yet studied. The space rock was recovered from the frozen Tagish Lake in Canada. The meteorite has aroused huge excitement among researchers because its fragments could help us understand better how the planets were formed. The rock fell to Earth on 18 January, 2000. The exceptionally long and bright fireball was seen throughout the Yukon, Northern British Columbia, parts of Alaska, and the Northwest Territories.