A meteor shower is a celestial event in which a number of
meteor
A meteoroid () is a small rocky or metallic body in outer space.
Meteoroids are defined as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than this are classified as mi ...
s are observed to radiate, or originate, from one point in the
night sky
The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon.
Natural light sources in a night sky in ...
. These meteors are caused by streams of cosmic debris called
meteoroids entering
Earth's atmosphere
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing fo ...
at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit the Earth's surface. Very intense or unusual meteor showers are known as meteor outbursts and meteor storms, which produce at least 1,000 meteors an hour, most notably from the
Leonids
The Leonids ( ) are a prolific meteor shower associated with the comet Tempel–Tuttle, which 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 ...
.
The Meteor Data Centre lists over 900 suspected meteor showers of which about 100 are well established. Several organizations point to viewing opportunities on the Internet. NASA maintains a daily map of active meteor showers.
Historical developments
A meteor shower in August 1583 was recorded in the
Timbuktu manuscripts
Timbuktu Manuscripts (or Tombouctou Manuscripts) is a blanket term for the large number of historically significant manuscripts that have been preserved for centuries in private households in Timbuktu, a city in northern Mali. The collections i ...
.
[Abraham, Curtis]
"Stars of the Sahara"
''New Scientist'', issue 2617,15 August 2007, page 39–41
In the modern era, the first great meteor storm was the
Leonids
The Leonids ( ) are a prolific meteor shower associated with the comet Tempel–Tuttle, which 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 ...
of November 1833. One estimate is a peak rate of over one hundred thousand meteors an hour, but another, done as the storm abated, estimated more than two hundred thousand meteors during the 9 hours of the storm,
[Leonid MAC]
Brief history of the Leonid shower over the entire region of
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
east of the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...
. American
Denison Olmsted (1791–1859) 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
The ''American Journal of Science'' (''AJS'') is the United States of America's longest-running scientific journal, having been published continuously since its conception in 1818 by Professor Benjamin Silliman, who edited and financed it himself ...
'', published in January–April 1834, and January 1836. He noted the shower was of short duration and was not seen in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, and that the meteors radiated from a point in the
constellation of Leo. He speculated the meteors had originated from a cloud of particles in space.
[Observing the Leonids](_blank)
Gary W. Kronk
Gary W. Kronk (born 1956) is an American amateur astronomer and writer.
Biography
Kronk was born in Granite City, Illinois, United States, on March 23, 1956. He developed an interest in space at an early age, during the time of the first manned ...
Work continued, yet coming to understand the annual nature of showers though the occurrences of storms perplexed researchers.
The actual nature of meteors was still debated during the 19th century. Meteors were conceived as an atmospheric phenomenon by many scientists (
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister ...
,
Adolphe Quetelet
Lambert Adolphe Jacques Quetelet FRSF or FRSE (; 22 February 1796 – 17 February 1874) was a Belgian astronomer, mathematician, statistician and sociologist who founded and directed the Brussels Observatory and was influential in intro ...
,
Julius Schmidt) until the Italian astronomer
Giovanni Schiaparelli ascertained the relation between meteors and comets in his work ''"Notes upon the astronomical theory of the falling stars" (
1867).'' In the 1890s, Irish astronomer
George Johnstone Stoney
George Johnstone Stoney FRS (15 February 1826 – 5 July 1911) was an Irish physicist. He is most famous for introducing the term ''electron'' as the "fundamental unit quantity of electricity".
He had introduced the concept, though not the wor ...
(1826–1911) and British astronomer
Arthur Matthew Weld Downing (1850–1917) were the first to attempt to calculate the position of the dust at Earth's orbit. They studied the dust ejected in 1866 by comet
55P/Tempel-Tuttle before the anticipated Leonid shower return of 1898 and 1899. Meteor storms were expected, but the final calculations showed that most of the dust would be far inside Earth's orbit. The same results were independently arrived at by
Adolf Berberich of the
Königliches Astronomisches Rechen Institut (Royal Astronomical Computation Institute) in Berlin, Germany. Although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions.
In 1981, Donald K. Yeomans of the
Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, La Cañada Flintridge, California ...
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.
In 1985, E. D. Kondrat'eva and E. A. Reznikov of Kazan State University first correctly identified the years when dust was released which was responsible for several past Leonid meteor storms. In 1995,
Peter Jenniskens predicted the 1995
Alpha Monocerotids outburst from dust trails. In anticipation of the 1999 Leonid storm,
Robert H. McNaught
Robert H. McNaught (born in Scotland in 1956) is a Scottish-Australian astronomer at the Research School of Astronomy and Astrophysics of the Australian National University (ANU). He has collaborated with David J. Asher of the Armagh Observator ...
,
David Asher, and Finland's Esko Lyytinen were the first to apply this method in the West. In 2006 Jenniskens published predictions for future dust trail encounters covering the next 50 years.
Jérémie Vaubaillon continues to update predictions based on observations each year for the
Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE).
Radiant point
Because meteor shower particles are all traveling in parallel paths and at the same velocity, they will appear to an observer below to radiate away from a single point in the sky. This
radiant
Radiant may refer to:
Computers, software, and video games
* Radiant (software), a content management system
* GtkRadiant, a level editor created by id Software for their games
* Radiant AI, a technology developed by Bethesda Softworks for '' ...
point is caused by the effect of
perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon. Meteor showers are normally named after the constellation from which the meteors appear to originate. This "fixed point" slowly moves across the sky during the night due to the Earth turning on its axis, the same reason the stars appear to slowly march across the sky. The radiant also moves slightly from night to night against the background stars (radiant drift) due to the Earth moving in its orbit around the Sun. Se
''IMO'' Meteor Shower Calendar 2017(
International Meteor Organization) for maps of drifting "fixed points."
When the moving radiant is at the highest point, it will reach the observer's sky that night. The Sun will be just clearing the eastern horizon. For this reason, the best viewing time for a meteor shower is generally slightly before dawn — a compromise between the maximum number of meteors available for viewing and the brightening sky, which makes them harder to see.
Naming
Meteor showers are named after the nearest constellation, or bright star with a Greek or Roman letter assigned that is close to the radiant position at the peak of the shower, whereby the grammatical
declension
In linguistics, declension (verb: ''to decline'') is the changing of the form of a word, generally to express its syntactic function in the sentence, by way of some inflection. Declensions may apply to nouns, pronouns, adjectives, adverbs, and ...
of the Latin
possessive form
A possessive or ktetic form (abbreviated or ; from la, possessivus; grc, κτητικός, translit=ktētikós) is a word or grammatical construction used to indicate a relationship of possession in a broad sense. This can include strict owne ...
is replaced by "id" or "ids." Hence, meteors radiating from near the star
Delta Aquarii
Delta Aquarii (δ Aquarii, abbreviated Delta Aqr, δ Aqr), officially named Skat , is the third-brightest star in the constellation of Aquarius. The apparent visual magnitude is 3.3, which can be seen with the naked eye. The distance to t ...
(declension "-i") are called the
Delta Aquariids. The International Astronomical Union's Task Group on Meteor Shower Nomenclature and the IAU's Meteor Data Center keep track of meteor shower nomenclature and which showers are established.
Origin of meteoroid streams
A meteor shower results from an interaction between a planet, such as Earth, and streams of debris from a
comet
A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...
. Comets can produce debris by water vapor drag, as demonstrated by
Fred Whipple in 1951, and by breakup. Whipple envisioned comets as "dirty snowballs," made up of rock embedded in ice, orbiting the
Sun. The "ice" may be
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
,
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
,
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
, or other
volatiles, alone or in combination. The "rock" may vary in size from a dust mote to a small boulder. Dust mote sized solids are
orders of magnitude more common than those the size of sand grains, which, in turn, are similarly more common than those the size of pebbles, and so on. When the ice warms and sublimates, the vapor can drag along dust, sand, and pebbles.
Each time a comet swings by the Sun in its
orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
, some of its ice vaporizes, and a certain number of meteoroids will be shed. The meteoroids spread out along the entire trajectory of the comet to form a meteoroid stream, also known as a "dust trail" (as opposed to a comet's "gas tail" caused by the tiny particles that are quickly blown away by solar radiation pressure).
Recently,
Peter Jenniskens[Jenniskens P. (2006). ''Meteor Showers and their Parent Comets''. Cambridge University Press, Cambridge, U.K., 790 pp.] has argued that most of our short-period meteor showers are not from the normal water vapor drag of active comets, but the product of infrequent disintegrations, when large chunks break off a mostly dormant comet. Examples are the
Quadrantids and
Geminids, which originated from a breakup of asteroid-looking objects, and
3200 Phaethon, respectively, about 500 and 1000 years ago. The fragments tend to fall apart quickly into dust, sand, and pebbles and spread out along the comet's orbit to form a dense meteoroid stream, which subsequently evolves into Earth's path.
Dynamical evolution of meteoroid streams
Shortly after Whipple predicted that dust particles traveled at low speeds relative to the comet, Milos Plavec was the first to offer the idea of a ''dust trail'', when he calculated how meteoroids, once freed from the comet, would drift mostly in front of or behind the comet after completing one orbit. The effect is simple
celestial mechanics
Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, ...
– the material drifts only a little laterally away from the comet while drifting ahead or behind the comet because some particles make a wider orbit than others.
These dust trails are sometimes observed in comet images taken at mid infrared wavelengths (heat radiation), where dust particles from the previous return to the Sun are spread along the orbit of the comet (see figures).
The gravitational pull of the planets determines where the dust trail would pass by Earth orbit, much like a gardener directing a hose to water a distant plant. Most years, those trails would miss the Earth altogether, but in some years, the Earth is showered by meteors. This effect was first demonstrated from observations of the 1995
alpha Monocerotids, and from earlier not widely known identifications of past earth storms.
Over more extended periods, the dust trails can evolve in complicated ways. For example, the orbits of some repeating comets, and meteoroids leaving them, are in
resonant orbits with
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
or one of the other large planets – so many revolutions of one will equal another number of the other. This creates a shower component called a filament.
A second effect is a close encounter with a planet. When the meteoroids pass by Earth, some are accelerated (making wider orbits around the Sun), others are decelerated (making shorter orbits), resulting in gaps in the dust trail in the next return (like opening a curtain, with grains piling up at the beginning and end of the gap). Also, Jupiter's perturbation can dramatically change sections of the dust trail, especially for a short period comets, when the grains approach the giant planet at their furthest point along the orbit around the Sun, moving most slowly. As a result, the trail has a ''clumping'', a ''braiding'' or a ''tangling'' of ''crescents'', of each release of material.
The third effect is that of
radiation pressure which will push less massive particles into orbits further from the sun – while more massive objects (responsible for
bolides or
fireball
Fireball may refer to:
Science
* Fireball (meteor), a brighter-than-usual meteor
* Ball lightning, an atmospheric electrical phenomenon
* ''Bassia scoparia'', a plant species
Arts and entertainment Films
* '' The Fireball'', a 1950 film starring ...
s) will tend to be affected less by radiation pressure. This makes some dust trail encounters rich in bright meteors, others rich in faint meteors.
Over time, these effects disperse the meteoroids and create a broader stream. The meteors we see from these streams are part of ''annual showers'', because Earth encounters those streams every year at much the same rate.
When the meteoroids collide with other meteoroids in the
zodiacal cloud, they lose their stream association and become part of the "sporadic meteors" background. Long since dispersed from any stream or trail, they form isolated meteors, not a part of any shower. These random meteors will not appear to come from the radiant of the leading shower.
Famous meteor showers
Perseids and Leonids
In most years, the most visible meteor shower is the
Perseids, which peak on 12 August of each year at over one meteor per minute. NASA has
toolto calculate how many meteors per hour are visible from one's observing location.
The
Leonid
Leonid (russian: Леонид ; uk, Леонід ; be, Леанід, Ljeaníd ) is a Slavic version of the given name Leonidas. The French version is Leonide.
People with the name include:
*Leonid Andreyev (1871–1919), Russian playwright a ...
meteor shower peaks around 17 November of each year. The Leonid shower produces a meteor storm, peaking at rates of thousands of meteors per hour. Leonid storms gave birth to the term ''meteor shower'' when it was first realised that, during the November 1833 storm, the meteors radiated from near the star Gamma Leonis. The last Leonid storms were in 1999, 2001 (two), and 2002 (two). Before that, there were storms in 1767, 1799, 1833, 1866, 1867, and 1966. When the Leonid shower is not ''storming'', it is less active than the Perseids.
See the Infographics on Meteor Shower Calendar-2021 on the right.
Other meteor showers
Established meteor showers
Official names are given in the International Astronomical Union's list of meteor showers.
Extraterrestrial meteor showers
Any other
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
body with a reasonably transparent atmosphere can also have meteor showers. As the Moon is in the neighborhood of Earth it can experience the same showers, but will have its own phenomena due to its lack of an atmosphere ''per se'', such as vastly increasing its
sodium tail. NASA now maintains an ongoing database of observed impacts on the moon maintained by the
Marshall Space Flight Center
The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama (Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's firs ...
whether from a shower or not.
Many planets and moons have impact craters dating back large spans of time. But new craters, perhaps even related to meteor showers are possible. Mars, and thus its moons, is known to have meteor showers. These have not been observed on other planets as yet but may be presumed to exist. For Mars in particular, although these are different from the ones seen on Earth because of the different orbits of Mars and Earth relative to the orbits of comets. The Martian atmosphere has less than one percent of the density of Earth's at ground level, at their upper edges, where meteoroids strike; the two are more similar. Because of the similar air pressure at altitudes for meteors, the effects are much the same. Only the relatively slower motion of the meteoroids due to increased distance from the sun should marginally decrease meteor brightness. This is somewhat balanced because the slower descent means that Martian meteors have more time to ablate.
On March 7, 2004, the panoramic camera on
Mars Exploration Rover ''
Spirit'' recorded a streak which is now believed to have been caused by a meteor from a Martian meteor shower associated with comet
114P/Wiseman-Skiff. A strong display from this shower was expected on December 20, 2007. Other showers speculated about are a "Lambda Geminid" shower associated with the
Eta Aquariids of Earth (''i.e.'', both associated with
Comet 1P/Halley), a "Beta Canis Major" shower associated with
Comet 13P/Olbers, and "Draconids" from
5335 Damocles
(5335) Damocles , provisional designation , is a centaur and the namesake of the damocloids, a group of minor planets which may be inactive nuclei of the Halley-type and long-period comets. It was discovered on 18 February 1991, by A ...
.
Isolated massive impacts have been observed at Jupiter: The 1994
Comet Shoemaker–Levy 9 which formed a brief trail as well, and successive events since then (see
List of Jupiter events
In recorded history, the planet Jupiter has experienced impact events and has been probed and photographed by several spacecraft.
Impact
Spacecraft entry
*''Galileo'' spacecraft entry – September 21, 2003
*''Galileo'' probe entry – Decembe ...
.) Meteors or meteor showers have been discussed for most of the objects in the Solar System with an atmosphere: Mercury, Venus, Saturn's moon
Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
, Neptune's moon
Triton
Triton commonly refers to:
* Triton (mythology), a Greek god
* Triton (moon), a satellite of Neptune
Triton may also refer to:
Biology
* Triton cockatoo, a parrot
* Triton (gastropod), a group of sea snails
* ''Triton'', a synonym of ''Triturus'' ...
, and
Pluto
Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...
.
IR Flashes induced by meteoroid impacts onto Pluto's surface
by I.B. Kosarev, I. V. Nemtchinov, ''Microsymposium'', vol. 36, MS 050, 2002
See also
* American Meteor Society
The American Meteor Society, Ltd. (AMS) is a non-profit scientific organization established to encourage and support the research activities of both amateur and professional astronomers who are interested in the field of meteor astronomy. Its aff ...
(AMS)
* Earth-grazing fireball
* International Meteor Organization (IMO)
* List of meteor showers
* Meteor procession
* North American Meteor Network (NAMN)
* Radiant
Radiant may refer to:
Computers, software, and video games
* Radiant (software), a content management system
* GtkRadiant, a level editor created by id Software for their games
* Radiant AI, a technology developed by Bethesda Softworks for '' ...
– point in the sky from which meteors appear to originate
* Zenith hourly rate (ZHR)
References
External links
Meteor Showers
by ''Sky and Telescope''
Joe Rao (SPACE.com)
The International Meteor Organisation
Meteor Shower Portal
shows the direction of active showers each night on a celestial sphere.
{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System
Astronomical events of the Solar System
Atmospheric entry
Meteoroids