Leonids

Leonids (LEO)
A Leonid meteor during the peak of Leonids in 2009
Pronunciation	/ˈliːənɪdz/
Discovery date	902 AD (first record)
Parent body	55P/Tempel–Tuttle
Radiant
Constellation	Leo
Right ascension	10h 08m
Declination	+22°
Properties
Occurs during	November 15 – November 20
Date of peak	November 18
Velocity	71 km/s
Zenithal hourly rate	Varies
See also: List of meteor showers

The Leonids (/ˈliːənɪdz/ LEE-ə-nidz) are a prolific meteor shower associated with the comet Tempel–Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. Their proper Greek name should be Leontids (Λεοντίδαι, Leontídai), but the word was initially constructed as a Greek/Latin hybrid and it has been used since. They peak in the month of November.

Earth moves through the meteoroid stream of particles left from the passages of a comet. The stream comprises solid particles, known as meteoroids, ejected by the comet as its frozen gases evaporate under the heat of the Sun when it is close enough – typically closer than Jupiter's orbit. The Leonids are a fast moving stream which encounter the path of Earth and impact at 72 km/s. Larger Leonids which are about 10 mm across have a mass of half a gram and are known for generating bright (apparent magnitude -1.5) meteors. An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.