Leonids

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Leonid (disambiguation).
Leonids (LEO)
Leonid Meteor.jpg
A Leonid meteor during the peak of Leonids in 2009
Pronunciation /ˈlənɪdz/
Discovery date 902 AD (first record)[1]
Parent body 55P/Tempel–Tuttle[2]
Radiant
Constellation Leo
Right ascension 10h 08m[2]
Declination +22°[2]
Properties
Occurs during November 15 – November 20[2]
Date of peak November 18[2]
Velocity 71[3] km/s
Zenithal hourly rate Varies[2]
See also: List of meteor showers

The Leonids (/ˈlənɪdz/ 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[citation needed] 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.[4] 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.[5] An annual Leonid shower may deposit 12 or 13 tons of particles across the entire planet.

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[6] and to a lesser extent by radiation pressure from the sun, the Poynting–Robertson effect, and the Yarkovsky effect.[7] These trails of meteoroids cause meteor showers when Earth encounters them. Old trails are spatially not dense and compose the meteor shower with a few meteors per minute. In the case of the Leonids, that tends to peak around November 18, but some are spread through several days on either side and the specific peak changes every year. Conversely, young trails are spatially very dense and the cause of meteor outbursts when the Earth enters one. Meteor storms (large outbursts) exceed 1000 meteors per hour, to be compared to the sporadic background (5 to 8 meteors per hour) and the shower background (several per hour).

History[edit]

1800s[edit]

Leonids-1833.jpg
The great Leonid shower storm of 1833|A famous depiction of the 1833 meteor storm, produced in 1889 for the Seventh-day Adventist book Bible Readings for the Home Circle.
Trouvelot- The November meteors. - 1868.jpgÉtienne Léopold Trouvelot, 1868
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."
Leonids as seen from space in 1997, NASA

The Leonids are famous because their meteor showers, or storms, can be among the most spectacular. Because of the storm of 1833 and the recent developments in scientific thought of the time (see for example the identification of Halley's Comet) 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,[8] but another, done as the storm abated, estimated in excess of 240,000 meteors during the nine hours of the storm[1] over the entire region of North America east of the Rocky Mountains. It was marked by the Native Americans,[9][10] abolitionists like Harriet Tubman and Frederick Douglass and slave-owners[11][12] and others.[13] Near Independence, Missouri, in Clay County, a refugee Mormon community watched the meteor shower on the banks of the Missouri River after having been driven from their homes by local settlers.[14] The founder and first leader of Mormonism, Joseph Smith, noted in his journal that this event was a literal fulfillment of the word of God and a sure sign that the coming of Christ is close at hand.[15] Denison Olmsted explained the event most accurately. After spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834,[16] and January 1836.[17] He noted the shower was of short duration and was not seen in Europe, and that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space.[18] Accounts of the 1866 repeat of the Leonids counted hundreds per minute/a few thousand per hr in Europe.[19] The Leonids were again seen in 1867, when moonlight reduced the rates to 1000 per hour. Another strong appearance of the Leonids in 1868 reached an intensity of 1000 per hour in dark skies. It was in 1866–67 that information on Comet Tempel-Tuttle was gathered pointing it out as the source of the meteor shower.[18] 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.

1900s[edit]

Then, in 1966 a spectacular storm was seen over the Americas.[20] Historical notes were gathered thus noting the Leonids back to 900AD.[21] Radar studies showed the 1966 storm included a relatively high percentage of smaller particles while 1965's lower activity had a much higher proportion of larger particles. In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle.[22] A graph [23] from it was adapted and re-published in Sky and Telescope.[24] It showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. This showed that the meteoroids are mostly behind and outside the path of the comet, but paths of the Earth through the cloud of particles resulting in powerful storms were very near paths of nearly no activity. But overall the 1998 Leonids were in a favorable position so interest was rising. 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.[25] There were also efforts to observe impacts of meteoroids, as an example of transient lunar phenomenon, on the Moon in 1999. A particular reason to observe the Moon is that our vantage from a location on Earth sees only meteors coming into the atmosphere relatively close to us while impacts on the Moon would be visible from across the Moon in a single view.[26] A sodium tail of the Moon tripled just after the 1998 Leonid shower which was composed of larger meteoroids (which in the case of the Earth was witnessed as fireballs.)[27] However in 1999 the sodium tail of the Moon did not change from the Leonid impacts. Research by Kondrat'eva, Reznikov and colleagues[28] at Kazan University had shown how meteor storms could be accurately predicted but for some years the worldwide meteor community remained largely unaware of these results. The work of David J. Asher, Armagh Observatory and Robert H. McNaught, Siding Spring Observatory[6] and independently by Esko Lyytinen[29][30] in 1999, following on from the Kazan research, is considered by most meteor experts as 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 ten minutes by narrowing down the clouds of particles to individual streams from each passage of the comet, and their trajectories amended by subsequent passage near planets. However, whether a specific meteoroid trail will be primarily composed of small or large particles, and thus the relative brightness of the meteors, was not understood. But McNaught did extend the work to examine the placement of the Moon with trails and saw a large chance of a storm impacting in 1999 from a trail while there were less direct impacts from trails in 2000 and 2001 (successive contact with trails through 2006 showed no hits.)[27]

2000s[edit]

Viewing campaigns resulted in spectacular footage from the 1999, 2001 and 2002, storms producing up to 3,000 Leonid meteors per hour.[25] Predictions for the Moon's Leonid impacts also noted that in 2000 the side of the Moon facing the stream was away from the Earth but that impacts should be in number enough to raise a cloud of particles kicked off the Moon by impacts would cause a detectable increase in the sodium tail of the Moon.[27] Research using the explanation of meteor trails/streams have explained the storms of the past. The 1833 storm was not due to the recent passage of the comet, but from a direct impact with the previous 1800 dust trail.[31] The meteoroids from the 1733 passage of Comet Tempel-Tuttle resulted in the 1866 storm[32] and the 1966 storm was from the 1899 passage of the comet.[33] 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.[34] This ground breaking work was soon applied to other meteor showers – for example the 2004 June Bootids. Peter Jenniskens has published predictions for the next 50 years.[35] 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. Recent work tries to take into account the roles of differences in parent bodies and the specifics of their orbits, ejection velocities off the solid mass of the core of a comet, radiation pressure from the sun, the Poynting–Robertson effect, and the Yarkovsky effect on the particles of different sizes and rates of rotation to explain differences between meteor showers in terms of being predominantly fireballs or small meteors.[7]

Year Leonids active between Peak of shower ZHRmax
2006 Nov 19th. Outburst of ZHR=35-40 was predicted from the 1932 trail.[36] 78[37]
2007 Nov 19th. Outburst of ZHR=~30 from the 1932 trail was predicted for Nov 18th.[36] 35[38]
2008 November 14–22 Nov 17th.[25] Considerable outburst of ZHR=130 from the 1466 trail was predicted for Nov 17th.[36] 99[39]
2009 November 10–21 ZHRmax ranging from 100[40][41] to over 500[25][42][43] on Nov 17th. The peak was observed at predicted time.[44] 79[44]
2010 November 10–23 Nov 18th 32[45]
2011 Nov 18th 22[46]
2012 November 6–30 Nov 20. Nov 17 ZHR=5-10 (predicted) / Nov 20 ZHR=10-15 (predicted from 1400 trail)[36] 47[47]
2013 November 15–20 Nov 17 but was washed out by a Full moon on Nov 17
2014 November 6–30 Nov 17 15?

Predictions until the end of the 21st century have been published by Mikhail Maslov.[36]

See also[edit]

References[edit]

  1. ^ a b Leonid MAC Brief history of the Leonid shower
  2. ^ a b c d e f Moore, Patrick; Rees, Robin (2011), Patrick Moore's Data Book of Astronomy (2nd ed.), Cambridge University Press, p. 275, ISBN 0-521-89935-4 
  3. ^ Beech, Martin (July 1998), Large-Body Meteoroids in the Leonid Stream, The Astronomical Journal 116 (1): 499–502, Bibcode:1998AJ....116..499B, doi:10.1086/300435 
  4. ^ Space.com The Power of a Shooting Star
  5. ^ Jenniskens, Peter (2006), Meteor Showers And Their Parent Comets, Cambridge University Press, p. 253, ISBN 0521853494 
  6. ^ a b McNaught, Robert H.; Asher, David J. (1999), Leonid Dust Trails and Meteor Storms, WGN, Journal of the International Meteor Organization 27 (2): 85–102, Bibcode:1999JIMO...27...85M 
  7. ^ a b Brown, Peter; J. Jones and J. Rendtel. "Evolution of Two periodic Meteoroid Streams: the Perseids and Leonids". Retrieved 2009-12-24. 
  8. ^ Space.com The 1833 Leonid Meteor Shower: A Frightening Flurry
  9. ^ "Counting by Winters". Lakota Winter Counts Online Exhibit by the Smithsonian Institution National Museum of Natural History. Smithsonian Institution. Retrieved 2009-12-24. 
  10. ^ Greene, Candace S.; Thornton, Russell (eds.). The Year the Stars Fell. ISBN 978-0-8032-2211-3. 
  11. ^ "The Night the Stars Fell; My Search for Amanda Young". Freedmen of the Frontier – African American Historical and Genealogical Resource Page of the city of Ft. Smith Arkansas. Retrieved 2009-12-24. 
  12. ^ Bell, Madison Smartt (June 24, 2007). "The Fugitive". New York Times. Retrieved 2009-12-24. 
  13. ^ "The Great Leonid Meteor Storm of 1833 – A first-hand account by Elder Samuel Rogers". NASA Science News. June 22, 1999. Retrieved 2009-12-24. 
  14. ^ http://www.archive.org/stream/autobiographyofp00prat#page/n3/mode/2up
  15. ^ The Joseph Smith Papers Journals Volume 1: 1832–1839
  16. ^ Olmsted, Denison (1833). "Observations on the Meteors of November 13th, 1833". The American journal of science and arts 25: 363–411. Retrieved 3 April 2012. 
  17. ^ Olmsted, Denison (1836). "Facts respecting the Meteoric Phenomena of November 13th, 1834.". The American journal of science and arts 29 (1): 168–170. 
  18. ^ a b Observing the Leonids Gary W. Kronk
  19. ^ The Revelation of Bahá'u'lláh, Vol 2 by Adib Taherzadeh, Appendix I: The Star-fall of 1866
  20. ^ "Eyewitness accounts of the 1966 Leonid Storm". P. Jenniskens/NASA-ARC. Retrieved 2009-12-25. 
  21. ^ McIntosh,, Bruce. A; Millman,, Peter. M. (1970), The Leonids by Radar--1957 to 1968, Meteoritics 5 (1): 1–18, Bibcode:1970Metic...5....1M, doi:10.1111/j.1945-5100.1970.tb00385.x 
  22. ^ Yeomans, Donald K. (September 1981), Comet Tempel-Tuttle and the Leonid meteors, Icarus 47 (03): 492–499, Bibcode:1981Icar...47..492Y, doi:10.1016/0019-1035(81)90198-6 
  23. ^ http://web.archive.org
  24. ^ Comet 55P/Tempel-Tuttle and the Leonid Meteors(1996, see p. 6)
  25. ^ a b c d "Return of the Leonids". NASA. Dec 4, 2008. Retrieved 2009-10-21. 
  26. ^ A Leonid on the Moon? by Dr. Tony Phillips
  27. ^ a b c McNaught, Robert H. (2000-10-27). "Lunar Leonids: Encounters of the Moon with Leonid dust trails". spaceweather.com. Retrieved 2009-12-25. 
  28. ^ Kondrat'eva, E.D.; Reznikov, E.A. (1985), Comet Tempel-Tuttle and the Leonid meteor swarm, Solar System Research 19: 96–101 
  29. ^ Lyytinen, Esko (1999), Meta Research Bulletin 8: 33–40 http://metaresearch.org/publications/bulletin/#VOL8 |url= missing title (help) 
  30. ^ Lyytinen, Esko J.; Flandern, Tom Van (January 2000), Predicting the Strength of Leonid Outbursts, Earth, Moon, and Planets, 82–83 (00): 149–166, doi:10.1023/A:1017068618114, ISSN 1573-0794 ,
  31. ^ Armagh Observatory Leonid dust trail positions in 1833.
  32. ^ Leonid dust trail positions in 1866 Armagh Observatory
  33. ^ Armagh Observatory Leonid dust trail positions in 1966
  34. ^ Meteor Orbs.org Predictions & Observations of Lunar Meteor impacts
  35. ^ Jenniskens, P. (2006). Meteor Showers and their Parent Comets. Cambridge, UK: Cambridge University Press. ISBN 0-521-85349-4. 
  36. ^ a b c d e Maslov, Mikhail (2007), Leonid predictions for the period 2001-2100, WGN, Journal of the International Meteor Organization 35 (1): 5–12, Bibcode:2007JIMO...35....5M ; also see "Leonids 1901-2100". M. Maslov webpage. 
  37. ^ Leonids 2006: Morning of 19 November
  38. ^ Leonids 2007: visual data quicklook
  39. ^ Leonids 2008: visual data quicklook
  40. ^ Fazekas, Andrew (November 16, 2009). "Leonid Meteor Shower: Best Sky Show Tonight". National Geographic News. 
  41. ^ "IMO Meteor Shower Calendar 2009". The International Meteor Organization. 1997–2009. Retrieved 2009-10-21. 
  42. ^ "Strong Leonid Meteor Shower Predicted for 2009". Space.com. 4 December 2008. Retrieved 2009-10-22. 
  43. ^ Lopez, Mike (December 7, 2008). "Watch Out for Leonids 2009 Meteor Shower". Retrieved 2009-10-22. 
  44. ^ a b "Leonids 2009: visual data quicklook". The International Meteor Organization. 
  45. ^ Leonids 2010: visual data quicklook
  46. ^ Leonids 2011: visual data quicklook
  47. ^ Leonids 2012: visual data quicklook

External links[edit]

Media related to Leonids at Wikimedia Commons