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The Leonids ( ) are a prolific annual
meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at ext ...
associated with the
comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
Tempel–Tuttle, and are also known for their spectacular meteor storms that occur about every 33 years. The Leonids get their name from the location of their radiant in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
Leo: the
meteor A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a ...
s appear to radiate from that point in the
sky The sky is an unobstructed view upward from the planetary surface, surface of the Earth. It includes the atmosphere of Earth, atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from ...
. The name is derived from
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
and
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
with the prefix ''Leo-'' referring to the constellation and the suffix ''-ids'' signifying that the meteor shower is the offspring of, descendent of, the constellation Leo.
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
moves through meteoroid streams left from passages of a comet. The streams consist of solid particles, known as
meteoroid A meteoroid ( ) is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than ''asteroids'', ranging in size from grains to objects up to wide. Objects smaller than meteoroids are classifie ...
s, normally ejected by the comet as its frozen gases
evaporate Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when hum ...
under the heat of the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
once within Jupiter's orbit. Due to the retrograde orbit of 55P/Tempel–Tuttle, the Leonids are fast moving streams which encounter the path of Earth and impact at . It is the fastest annual meteor shower. Larger Leonids which are about across have a mass of and are known for generating bright (
apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
−1.5) meteors. 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 tothough different fromthat of the comet. They are differentially disturbed by the planets, in particular
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, and to a lesser extent by
radiation pressure Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of ...
from the Sunthe
Poynting–Robertson effect The Poynting–Robertson effect, also known as Poynting–Robertson drag, named after John Henry Poynting and Howard P. Robertson, is a process by which solar radiation causes a dust grain orbiting a star to lose angular momentum relative to its or ...
and the Yarkovsky effect. 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 18 November, 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. The Leonids also produce (very large outbursts) about every 33 years, during which activity exceeds 1,000 meteors per hour, with some events exceeding 100,000 meteors per hour, in contrast to the sporadic background (5 to 8 meteors per hour) and the shower background (several meteors per hour).


History


1800s

The Leonids are famous because their meteor showers, or storms, can be among the most spectacular. Because of the storm of 1833 and the developments in scientific thought of the time (see for example the identification of
Halley's Comet Halley's Comet is the only known List of periodic comets, short-period comet that is consistently visible to the naked eye from Earth, appearing every 72–80 years, though with the majority of recorded apparitions (25 of 30) occurring after ...
), the Leonids have had a major effect on the scientific study of meteors, which had previously been thought to be atmospheric phenomena. Although it has been suggested the Leonid meteor shower and storms have been noted in ancient times, it was the meteor storm of November 12–13, 1833 that broke into people's modern-day awareness. One estimate of the peak rate is over one hundred thousand meteors an hour, while another, done as the storm abated, estimated in excess of 240,000 meteors during the nine hours of the storm, over the entire region of North America east of the Rocky Mountains. The event was marked by several nations of Native Americans: the
Cheyenne The Cheyenne ( ) are an Indigenous people of the Great Plains. The Cheyenne comprise two Native American tribes, the Só'taeo'o or Só'taétaneo'o (more commonly spelled as Suhtai or Sutaio) and the (also spelled Tsitsistas, The term for th ...
established a peace treaty and the
Lakota Lakota may refer to: *Lakota people, a confederation of seven related Native American tribes *Lakota language Lakota ( ), also referred to as Lakhota, Teton or Teton Sioux, is a Siouan languages, Siouan language spoken by the Lakota people of ...
calendar was reset. Many Native American birthdays were calculated by reference to the 1833 Leonid event.
Abolitionists Abolitionism, or the abolitionist movement, is the political movement to end slavery and liberate enslaved individuals around the world. The first country to fully outlaw slavery was France in 1315, but it was later used in its colonies. T ...
including
Harriet Tubman Harriet Tubman (born Araminta Ross, – March 10, 1913) was an American abolitionist and social activist. After escaping slavery, Tubman made some 13 missions to rescue approximately 70 enslaved people, including her family and friends, us ...
and
Frederick Douglass Frederick Douglass (born Frederick Augustus Washington Bailey, February 14, 1818 – February 20, 1895) was an American social reformer, Abolitionism in the United States, abolitionist, orator, writer, and statesman. He was the most impor ...
as well as slave-owners took note and others. The ''
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'' carried a series of articles on the event including reports from Canada to Jamaica, it made news in several states beyond New York and, though it appeared in North America, was talked about in Europe. The journalism of the event tended to rise above the partisan debates of the time and reviewed facts as they could be sought out.
Abraham Lincoln Abraham Lincoln (February 12, 1809 – April 15, 1865) was the 16th president of the United States, serving from 1861 until Assassination of Abraham Lincoln, his assassination in 1865. He led the United States through the American Civil War ...
commented on it years later. Near
Independence, Missouri Independence is a city in and one of two county seats of Jackson County, Missouri, United States. It is a satellite city of Kansas City, Missouri, and is the largest suburb on the Missouri side of the Kansas City metropolitan area. In 2020 Unite ...
, in Clay County, a refugee
Mormon Mormons are a religious and cultural group related to Mormonism, the principal branch of the Latter Day Saint movement started by Joseph Smith in upstate New York during the 1820s. After Smith's death in 1844, the movement split into several ...
community watched the meteor shower on the banks of the Missouri River after having been driven from their homes by local settlers.
Joseph Smith Joseph Smith Jr. (December 23, 1805June 27, 1844) was an American religious and political leader and the founder of Mormonism and the Latter Day Saint movement. Publishing the Book of Mormon at the age of 24, Smith attracted tens of thou ...
, the founder and first leader of
Mormonism Mormonism is the theology and religious tradition of the Latter Day Saint movement of Restorationism, Restorationist Christianity started by Joseph Smith in Western New York in the 1820s and 1830s. As a label, Mormonism has been applied to va ...
, afterwards noted in his journal for November 1833 his belief that this event was "a litteral 'sic''fulfillment of the word of God" and a harbinger of the imminent
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of
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. Though it was noted in the midwest and eastern areas, it was also noted in Far West, Missouri.
Denison Olmsted Denison Olmsted (June 18, 1791 – May 13, 1859) was an American physicist and astronomer. Professor Olmsted is credited with giving birth to meteor science after the 1833 Leonid meteor shower over North America spurred him to study this phenom ...
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, and January 1836. 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.Observing the Leonids
Gary W. Kronk
Accounts of the 1866 repeat of the Leonids counted hundreds per minute/a few thousand per hour in Europe. The Leonids were again seen in 1867, when moonlight reduced the rates to 1,000 meteors per hour. Another strong appearance of the Leonids in 1868 reached an intensity of 1,000 meteors 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 and meteor storms. When the storms failed to return in 1899, it was generally thought that the dust had moved on and the storms were a thing of the past.


1900s

In 1966, a spectacular meteor storm was seen over the Americas. Historical notes were gathered thus noting the Leonids back to 900 AD. 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. A graph from it was adapted and re-published in '' Sky and Telescope''. 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. In 1999, there were also efforts to observe impacts of meteoroids on the Moon, as an example of transient lunar phenomenon. 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. The 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). However, in 1999 the sodium tail of the Moon did not change from the Leonid impacts. Research by Kondrat'eva, Reznikov and colleagues 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 Siding Spring Observatory near Coonabarabran, New South Wales, Australia, part of the Research School of Astronomy & Astrophysics (RSAA) at the Australian National University (ANU), incorporates the Anglo-Australian Telescope along with a coll ...
and independently by Esko Lyytinen 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).


2000s

Viewing campaigns resulted in spectacular footage from the 1999, 2001, and 2002 storms which produced up to 3,000 Leonid meteors per hour. 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 which could cause a detectable increase in the sodium tail of the Moon. 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. The meteoroids from the 1733 passage of Comet Tempel-Tuttle resulted in the 1866 storm and the 1966 storm was from the 1899 passage of the comet. 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. 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. However, a close encounter with
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
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 Radiation pressure (also known as light pressure) is mechanical pressure exerted upon a surface due to the exchange of momentum between the object and the electromagnetic field. This includes the momentum of light or electromagnetic radiation of ...
from the Sun, the
Poynting–Robertson effect The Poynting–Robertson effect, also known as Poynting–Robertson drag, named after John Henry Poynting and Howard P. Robertson, is a process by which solar radiation causes a dust grain orbiting a star to lose angular momentum relative to its or ...
, 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. Predictions until the end of the 21st century have been published by Mikhail Maslov.; also see


See also

* List of meteor showers * " Stars Fell on Alabama", based on the 1833 Leonid shower *
Perseids The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle that are usually visible from mid-July to late-August. The meteoroid, meteors are called the Perseids because they appear from the general direction of the const ...
, associated with the comet Swift–Tuttle


References


Further reading

* *


External links


The Discovery of the Perseid Meteors
(after the Leonids and) Prior to 1837, nobody realized the Perseids were an annual event, by Mark Littmann

by Robert H. McNaught



* ttps://www.space.com/3117-hear-leonid-meteor-shower.html How to hear the Leonid Meteor Shower
Observatorio ARVAL – The Leonid Meteors


at shadow&substance.com {{Authority control Leo (constellation) Meteor showers November