Leonids
18383
223019702
2008-07-02T05:42:09Z
75.41.102.65
/* Meteor shower */
[[Image:Leonids-1833.jpg|right|thumb|230px|The great Leonid shower storm of 1733|The most famous depiction of the 1833 meteor storm actually produced in 1889 for the [[Adventist]] book ''Bible Readings for the Home Circle'' based on a first-person account of the 1833 storm by a minister, Joseph Harvey Waggoner on his way from Florida to New Orleans.]]<!-- Commented out because image was deleted: [[Image:1966_leonids_big.gif|thumb|right|Time-lapse photograph of the 1966 Leonid meteor shower. {{deletable image-caption}}]] -->
: ''For a list of famous people named Leonid, please see [[Leonid]] (a disambiguation page).''
The '''Leonids''' ([ˈli.əˌnɪdz] ''lee-uh-nids'') are a prolific [[meteor shower]] associated with the [[comet]] [[Comet Tempel-Tuttle|Tempel-Tuttle]]. The Leonids get their name from the location of their [[Radiant (meteor shower)|radiant]] in the [[constellation]] [[Leo (constellation)|Leo]]: the meteors appear to stream from that point in the [[sky]].
==Meteor shower==
The meteor shower is visible every year around [[November 17]], plus or minus a week, when the [[Earth]] moves through the meteoroid stream of [[particles]] left from the passages of the [[comet]]. The stream comprises solid particles, known as [[meteoroid]]s, 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 air molecules ramming the meteoroid, which fragments and atomizes the dust [http://www.space.com/scienceastronomy/astronomy/leonids_science_021112.html], and the resulting spray of microscopic debris collides with individual atoms of the atmosphere which then cool by glowing (not by friction as commonly thought). Larger particles leave a stream of smaller particles and form a [[bolide]] or [[Glowworm (astronomy)|fireball]], 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 ordbits similar though different from that of the comet. They are differentially disturbed by the planets, in particular [[Jupiter]] (see also a full explanation by [http://cdsads.u-strasbg.fr/abs/1999JIMO...27...85M 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 17th, but changing every year<ref>you may check every year at the [http://www.imo.net/calendar IMO website]</ref>. On the contrary 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 hours <ref>after correction, see: [http://www.imo.net/observations the IMO pages]</ref>, to be compared to the annual background (1 to 2 meteors per hour) and the shower background (a few per hour).
==History==
[[Image:Leonids-Pickering.jpg|right|thumb|225px|Woodcut print depicts the shower as seen at Niagara Falls, New York. ''Mechanics' Magazine'' said this illustration was made by an editor named Pickering "who witnessed the scene."]]
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[http://www.space.com/scienceastronomy/astronomy/leonids_1833_011114.html], but another, done as the storm abated, estimated in excess of two hundred thousand meteors an hour[http://leonid.arc.nasa.gov/history.html] over the entire region of North America east of the Rocky Mountains. It was marked by the [[Native Americans in the United States|Native Americans]], [[slaves]] and owners, and many others. It was, in a word, unignorable. Many thought it was the end of the world. That same 1833 shower, near [[Independence, Missouri]], it was taken as a sign to push the growing [[Mormon]] community out of the area.<ref>McCullough, David, ''Truman'', 1992, p. 22</ref>
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, 2001 and 2002 storms. Initially, the exact location of the dust was unknown. A [http://www.iltrails.org/leokin4.gif graph] published in [[Sky and Telescope]] adapted from [http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/19339/1/98-0663.pdf Comet 55P/Tempel-Tuttle and the Leonid Meteors](1996, see p.6) shows relative positions of the Earth and Comet and marks where Earth encountered dense dust. This showed basically that the particles are behind and outside the path of the comet, but paths resulting in powerful storms were very near paths of nearly no activity. The work of [[David J. Asher|David Asher]], [[Armagh Observatory]] and [[Robert H. McNaught]], [[Siding Spring Observatory]], and independently that by Esko Lyytinen of Finland, following on from research by Kondrat'eva, Reznikov and colleagues at [[Kazan University|Kazan]], is generally considered the breakthrough in modern analysis of meteor storms. Whereas previously it was hazardous to guess if there would be a storm or little activity, the predictions of Asher and McNaught timed bursts in activity down to five minutes, although the relative brightness of the meteors is still not understood. The double spikes in Leonid activity in 2001 and in 2002 were due to the passage of the comet's dust ejected in 1767 and 1866.[http://www.meteorobs.org/lunar.html] The 1833 storm was not due to the recent passage of the comet, but from a direct hit with the 1800 dust [http://www.arm.ac.uk/leonid/dust1833.html] and the 1966 storm was from the 1899 passage of the comet.[http://www.arm.ac.uk/leonid/dust1966.html] Examples of other streams accounting for spikes in activity include the 2004 June Bootids. [[Peter Jenniskens]] has published predictions for the next 50 years.<ref>Jenniskens P., Meteor Showers and their Parent Comets. Cambridge University Press, Cambridge, UK, 790 pp. </ref>
However, a close encounter with [[Jupiter]] is expected to perturb the comet's path, and many streams, making storms of historic magnitude unlikely for many decades. <ref>a list of predictions can be found [http://star.arm.ac.uk/leonid/ here] and [http://www.imcce.fr/page.php?nav=/en/ephemerides/phenomenes/meteor/predictions_request.php?id=35 here]</ref>
==See also==
* [[Meteor shower]]s
* [[List of meteor showers]]
* [[Stars Fell on Alabama]], based on the 1833 Leonid shower
==References==
{{reflist|2}}
==External links==
* [http://meteorshowersonline.com/leonids.html Leonid History] by Gary W. Kronk
* [http://www.arm.ac.uk/leonid/dustexpl.html Leonid dust trails] by David Asher
* [http://science.nasa.gov/newhome/headlines/ast22jun99%5F2.htm The Great Leonid Meteor Storm of 1833.] A first-hand account by Elder Samuel Rogers
* [http://skytonight.com/observing/objects/meteors/3304116.html?page=1&c=y The Discovery of the Perseid Meteors] (after the Leonids and) Prior to 1837, nobody realized the Perseids were an annual event, by Mark Littmann
* [http://www.angelfire.com/ar/freedmen/stars.html The Night the Stars Fell My Search for Amanda Young] a slave narrative.
* [http://www.native-voice.com/fullstory.cfm?ID=1013 Winter Counts] ''The Native Voice'' By Lise Balk King
* [http://www.spaceweather.com/meteoroutlook/lunarleonids.html Lunar Leonids: Encounters of the Moon with Leonid dust trails] by Robert H. McNaught
* [http://www.chron.com/content/interactive/space/astronomy/news/1999/solarsys/991121.html Brilliant Leonid storm likely fodder for later Lincoln speech] by Jim Vertuno
* [http://leonid.arc.nasa.gov/meteor.html NASA: Background facts on meteors and meteor showers]
* [http://leonid.arc.nasa.gov/estimator.html NASA: Estimate the best viewing times for your part of the world]
* [http://science.nasa.gov/headlines/y2006/14nov_leonids.htm?list67038 Science@NASA: Leonids 2006]
* [http://www.space.com/spacewatch/061116_leonids_listen.html How to hear the Leonid Meteor Shower]
* [http://www.oarval.org/leonids.htm Observatorio ARVAL - The Leonid Meteors]
[[Category:Leo constellation]]
[[Category:Meteor showers]]
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