Leonids

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The Leonids ( lee-uh-nids) 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 stream from that point in the sky. The 2009 display peaking on November 17 may produce more than 500 meteors an hour.

Earth moves through the meteoroid stream of particles left from the passages of the comet. The stream comprises solid particles, known as meteoroids, ejected by the comet as its frozen gases evaporate under the heat of the Sun which begins to warm the comet as it comes within the orbit of Jupiter. A typical particle is no bigger than fine dust. The main source of light of a meteor is caused by the solar wind, which fragments and atomizes the dust, and the resulting spray of microscopic debris collides with individual atoms of the atmosphere ionizing the air. The air molecules recombine and cool by giving off photons. Larger particles leave a stream of smaller particles and form a tail, which can leave a glowing trail in the atmosphere. Leonids in particular are well known for having such bright meteors. The meteoroids left by the comet are organized in trails in orbits similar to though different from that of the comet. They are differentially disturbed by the planets, in particular Jupiter (see also a full explanation by McNaught & Asher (1999)). The ensemble of the trails compose the meteoroid stream. Old trails are spatially not dense and compose the meteor shower background (a few meteors per minute), happening around November 17, but changing every year. Conversely, young trails are spatially very dense and the cause of meteor storms when the Earth enters one of these structures. Usual counts during a storm exceed 1000 meteors per hour, to be compared to the annual background (1 to 2 meteors per hour) and the shower background (a few per hour).

1 History
2 See also
3 References
4 External links

History

The Leonids are famous because their meteor showers, or storms, can be, and have been in a few cases, among the most spectacular. Because of the superlative storm of 1833 and the recent developments in scientific thought the Leonids have had a major effect on the development of the scientific study of meteors which had previously been thought to be atmospheric phenomena. The meteor storm of 1833 was of truly superlative strength. One estimate is over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of two hundred thousand meteors an hour over the entire region of North America east of the Rocky Mountains. It was marked by the Native Americans, slaves and owners, and many others. That same 1833 shower, near Independence, Missouri, was taken as a sign to push the growing Mormon community out of the area.

Other great Leonid storms were seen in 1866 and 1867. When the storms failed to return in 1899, it was generally thought that the dust had moved on and storms were a thing of the past. Then, in 1966 a spectacular storm was seen over the Americas. Leading up to the 1998 return, an airborne observing campaign was organized to mobilize modern observing techniques by Peter Jenniskens at NASA Ames Research Center. This resulted in spectacular footage from the 1999,

Even more about Meteor Shower November 2009

Meteor Shower November 2009

2009 Meteor Showers and Viewing Tips. The next meteor shower is the Leonids on November 17-18. The shower will peak in the predawn hours of November 17.