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 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.[1] The Meteor Data Centre lists over 900 suspected meteor showers of which about 100 are well established.[2] Several organizations point to viewing opportunities on the Internet.[3]

AGOModra Leonids98
Four-hour time lapse exposure of the sky
Leonid meteor shower as seen from space (1997)
Leonids from space

Historical developments

PSM V01 D405 August meteor shower orbit
Diagram from 1872

The first great meteor storm in the modern era was the Leonids of November 1833. One estimate is a peak rate of over one hundred thousand meteors an hour,[4] but another, done as the storm abated, estimated in excess of two hundred thousand meteors during the 9 hours of storm,[5] over the entire region of North America east of the Rocky Mountains. 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, published in January–April 1834,[6] and January 1836.[7] 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.[8] Work continued, yet coming to understand the annual nature of showers though the occurrences of storms perplexed researchers.[9]

The actual nature of meteors was still debated during the XIX century. Meteors were conceived as an atmospheric phenomenon by many scientists (Alexander von Humboldt, Adolphe Qoetelet, 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 (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 in advance of the anticipated Leonid shower return of 1898 and 1899. Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of 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 reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle.[10] A graph[11] from it was adapted and re-published in Sky and Telescope.[12] 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.[13] In anticipation of the 1999 Leonid storm, Robert H. McNaught,[14] David Asher,[15] and Finland's Esko Lyytinen were the first to apply this method in the West.[16][17] In 2006 Jenniskens published predictions for future dust trail encounters covering the next 50 years.[18] Jérémie Vaubaillon continues to update predictions based on observations each year for the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE).[19]

Radiant point

PSM V18 D201 Shower of perseids sept 6 and 7
Meteor shower on chart

Because meteor shower particles are all traveling in parallel paths, and at the same velocity, they will all appear to an observer below to radiate away from a single point in the sky. This radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. Meteor showers are almost always 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. See 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 in 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 lightening 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 of the Latin possessive form is replaced by "id" or "ids". Hence, meteors radiating from near the star delta Aquarii (declension "-i") are called 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

Ssc2005-04a medium
Comet Encke's meteoroid trail is the diagonal red glow
Sig06-011 medium
Meteoroid trail between fragments of Comet 73P

A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet. Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951,[20] and by breakup. Whipple envisioned comets as "dirty snowballs," made up of rock embedded in ice, orbiting the Sun. The "ice" may be water, methane, ammonia, or other volatiles, alone or in combination. The "rock" may vary in size from that of a dust mote to that of 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, some of its ice vaporizes and a certain amount of meteoroids will be shed. The meteoroids spread out along the entire orbit 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 very small particles that are quickly blown away by solar radiation pressure).

Recently, Peter Jenniskens[18] 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, 2003 EH1 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 orbit of the comet 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 travelled 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 – 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.[18] 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,[21][22] and from earlier not widely known identifications of past earth storms.

Over longer periods of time, 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 or one of the other large planets – so many revolutions of one will equal another number of revolutions 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 change sections of the dust trail dramatically, especially for short period comets, when the grains approach the big 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 individual 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 fireballs) 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 main shower.

Famous meteor showers

Perseids and Leonids

The most visible meteor shower in most years are the Perseids, which peak on 12 August of each year at over one meteor per minute. NASA has a useful tool to calculate how many meteors per hour are visible from one's observing location.

The Leonid meteor shower peaks around 17 November of each year. Approximately every 33 years, 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.

Other meteor showers

Established meteor showers

Official names are given in the International Astronomical Union's list of meteor showers.[23]

Shower Time Parent object
Quadrantids early January The same as the parent object of minor planet 2003 EH1,[24] and Comet C/1490 Y1.[25][26] Comet C/1385 U1 has also been studied as a possible source.[27]
Lyrids late April Comet Thatcher
Pi Puppids (periodic) late April Comet 26P/Grigg-Skjellerup
Eta Aquariids early May Comet 1P/Halley
Arietids mid-June Comet 96P/Machholz, Marsden and Kracht comet groups complex[1][28]
June Bootids (periodic) late June Comet 7P/Pons-Winnecke
Southern Delta Aquariids late July Comet 96P/Machholz, Marsden and Kracht comet groups complex[1][28]
Alpha Capricornids late July Comet 169P/NEAT[29]
Perseids mid-August Comet 109P/Swift-Tuttle
Kappa Cygnids mid-August Minor planet 2008 ED69[30]
Aurigids (periodic) early September Comet C/1911 N1 (Kiess)[31]
Draconids (periodic) early October Comet 21P/Giacobini-Zinner
Orionids late October Comet 1P/Halley
Southern Taurids early November Comet 2P/Encke
Northern Taurids mid-November Minor planet 2004 TG10 and others[1][32]
Andromedids (periodic) mid-November Comet 3D/Biela[33]
Alpha Monocerotids (periodic) mid-November unknown[34]
Leonids mid-November Comet 55P/Tempel-Tuttle
Phoenicids (periodic) early December Comet 289P/Blanpain[35]
Geminids mid-December Minor planet 3200 Phaethon[36]
Ursids late December Comet 8P/Tuttle[37]

Extraterrestrial meteor showers

Earth Sol63A UFO-A067R1
Mars meteor by MER Spirit rover

Any other solar system 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.[38] NASA now maintains an ongoing database of observed impacts on the moon[39] maintained by the Marshall Space Flight Center 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.[40] 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 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 in that the slower descent means that Martian meteors have more time in which to ablate.[41]

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.[42]

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.) Meteors or meteor showers have been discussed for most of the objects in the solar system with an atmosphere: Mercury,[43] Venus,[44] Saturn's moon Titan,[45] Neptune's moon Triton,[46] and Pluto.[47]

See also

  • Portal-puzzle.svg Meteor showers portal

References

  1. ^ a b c d Jenniskens, P. (2006). Meteor Showers and their Parent Comets. Cambridge University Press. ISBN 978-0-521-85349-1.
  2. ^ Meteor Data Center list of Meteor Showers
  3. ^ St. Fleur, Nicholas, The Quadrantids and Other Meteor Showers That Will Light Up Night Skies in 2018, The New York Times, January 2, 2018
  4. ^ Space.com The 1833 Leonid Meteor Shower: A Frightening Flurry
  5. ^ Leonid MAC Brief history of the Leonid shower
  6. ^ Olmsted, Denison (1833). "Observations on the Meteors of November 13th, 1833". The American Journal of Science and Arts. 25: 363–411. Retrieved 21 May 2013.
  7. ^ Olmsted, Denison (1836). "Facts respecting the Meteoric Phenomena of November 13th, 1834". The American Journal of Science and Arts. 29 (1): 168–170.
  8. ^ Observing the Leonids Gary W. Kronk
  9. ^ F.W. Russell, Meteor Watch Organizer, by Richard Taibi, May 19, 2013, accessed 21 May 2013
  10. ^ Yeomans, Donald K. (September 1981). "Comet Tempel-Tuttle and the Leonid meteors". Icarus. 47 (3): 492–499. Bibcode:1981Icar...47..492Y. doi:10.1016/0019-1035(81)90198-6{{inconsistent citations}}
  11. ^ https://web.archive.org
  12. ^ Comet 55P/Tempel-Tuttle and the Leonid Meteors Archived 2007-06-30 at the Wayback Machine(1996, see p. 6)
  13. ^ Article published in 1997, notes prediction in 1995 - Jenniskens, P.; Betlem, H.; De Lignie, M.; Langbroek, M. (1997). "The Detection of a Dust Trail in the Orbit of an Earth-threatening Long-Period Comet". Astrophysical Journal. 479 (1): 441. Bibcode:1997ApJ...479..441J. doi:10.1086/303853.
  14. ^ Re: (meteorobs) Leonid Storm? Archived 2007-03-07 at the Wayback Machine By Rob McNaught,
  15. ^ Blast from the Past Armagh Observatory press release 1999 April 21st.
  16. ^ Royal Astronomical Society Press Notice Ref. PN 99/27, Issued by: Dr Jacqueline Mitton RAS Press Officer
  17. ^ Voyage through a comet's trail, The 1998 Leonids sparkled over Canada By BBC Science's Dr Chris Riley on board NASA's Leonid mission
  18. ^ a b c Jenniskens P. (2006). Meteor Showers and their Parent Comets. Cambridge University Press, Cambridge, U.K., 790 pp.
  19. ^ IMCCE Prediction page Archived 2012-10-08 at the Wayback Machine
  20. ^ Whipple, F. L. (1951). "A Comet Model. II. Physical Relations for Comets and Meteors". Astrophys. J. 113: 464. Bibcode:1951ApJ...113..464W. doi:10.1086/145416.
  21. ^ Jenniskens P., 1997. Meteor steram activity IV. Meteor outbursts and the reflex motion of the Sun. Astron. Astrophys. 317, 953–961.
  22. ^ Jenniskens P., Betlem, H., De Lignie, M., Langbroek, M. (1997). The detection of a dust trail in the orbit of an Earth-threatening long-period comet. Astrohys. J. 479, 441–447.
  23. ^ "List of all meteor showers". International Astronomical Union. 15 August 2015.
  24. ^ Jenniskens, P. (March 2004). "2003 EH1 is the Quadrantid shower parent comet". Astronomical Journal. 127 (5): 3018–3022. Bibcode:2004AJ....127.3018J. doi:10.1086/383213.
  25. ^ Ball, Phillip. Dead comet spawned New Year meteors, Nature online website, ISSN 1744-7933, doi:10.1038/news031229-5, published online on December 31, 2003.
  26. ^ Haines, Lester, Meteor shower traced to 1490 comet break-up: Quadrantid mystery solved, The Register, January 8, 2008.
  27. ^ Marco Micheli; Fabrizio Bernardi; David J. Tholen (May 16, 2008). "Updated analysis of the dynamical relation between asteroid 2003 EH1 and comets C/1490 Y1 and C/1385 U1". Monthly Notices of the Royal Astronomical Society: Letters. 390 (1): L6–L8. arXiv:0805.2452. Bibcode:2008MNRAS.390L...6M. doi:10.1111/j.1745-3933.2008.00510.x.
  28. ^ a b Sekanina, Zdeněk; Chodas, Paul W. (December 2005). "Origin of the Marsden and Kracht Groups of Sunskirting Comets. I. Association with Comet 96P/Machholz and Its Interplanetary Complex". Astrophysical Journal Supplement Series. 161 (2): 551. Bibcode:2005ApJS..161..551S. doi:10.1086/497374.
  29. ^ Jenniskens, P.; Vaubaillon, J. (2010). "Minor Planet 2002 EX12 (=169P/NEAT) and the Alpha Capricornid Shower". Astronomical Journal. 139 (5): 1822–1830. Bibcode:2010AJ....139.1822J. doi:10.1088/0004-6256/139/5/1822.
  30. ^ Jenniskens, P.; Vaubaillon, J. (2008). "Minor Planet 2008 ED69 and the Kappa Cygnid Meteor Shower". Astronomical Journal. 136 (2): 725–730. Bibcode:2008AJ....136..725J. doi:10.1088/0004-6256/136/2/725.
  31. ^ Jenniskens, Peter; Vaubaillon, Jérémie (2007). "An Unusual Meteor Shower on 1 September 2007". Eos, Transactions, American Geophysical Union. 88 (32): 317–318. Bibcode:2007EOSTr..88..317J. doi:10.1029/2007EO320001.
  32. ^ Porubčan, V.; Kornoš, L.; Williams, I.P. (2006). "The Taurid complex meteor showers and asteroids". Contributions of the Astronomical Observatory Skalnaté Pleso. 36 (2): 103–117. arXiv:0905.1639. Bibcode:2006CoSka..36..103P.
  33. ^ Jenniskens, P.; Vaubaillon, J. (2007). "3D/Biela and the Andromedids: Fragmenting versus Sublimating Comets" (PDF). The Astronomical Journal. 134 (3): 1037. Bibcode:2007AJ....134.1037J. doi:10.1086/519074.
  34. ^ Jenniskens, P.; Betlem, H.; De Lignie, M.; Langbroek, M. (1997). "The Detection of a Dust Trail in the Orbit of an Earth-threatening Long-Period Comet". Astrophysical Journal. 479 (1): 441. Bibcode:1997ApJ...479..441J. doi:10.1086/303853.
  35. ^ Jenniskens, P.; Lyytinen, E. (2005). "Meteor Showers from the Debris of Broken Comets: D/1819 W1 (Blanpain), 2003 WY25, and the Phoenicids". Astronomical Journal. 130 (3): 1286–1290. Bibcode:2005AJ....130.1286J. doi:10.1086/432469.
  36. ^ Brian G. Marsden (1983-10-25). "IAUC 3881: 1983 TB AND THE GEMINID METEORS; 1983 SA; KR Aur". International Astronomical Union Circular. Retrieved 2011-07-05.
  37. ^ Jenniskens, P.; Lyytinen, E.; De Lignie, M.C.; Johannink, C.; Jobse, K.; Schievink, R.; Langbroek, M.; Koop, M.; Gural, P.; Wilson, M.A.; Yrjölä, I.; Suzuki, K.; Ogawa, H.; De Groote, P. (2002). "Dust Trails of 8P/Tuttle and the Unusual Outbursts of the Ursid Shower". Icarus. 159 (1): 197–209. Bibcode:2002Icar..159..197J. doi:10.1006/icar.2002.6855.
  38. ^ Hunten, D. M. (1991). "A possible meteor shower on the Moon". Geophysical Research Letters. 18 (11): 2101–2104. Bibcode:1991GeoRL..18.2101H. doi:10.1029/91GL02543.
  39. ^ Lunar Impacts
  40. ^ Meteor showers at Mars
  41. ^ Can Meteors Exist at Mars?
  42. ^ Meteor Showers and their Parent Bodies
  43. ^ Rosemary M. Killen; Joseph M. Hahn (December 10, 2014). "Impact Vaporization as a Possible Source of Mercury's Calcium Exosphere". Icarus. 250: 230–237. Bibcode:2015Icar..250..230K. doi:10.1016/j.icarus.2014.11.035. hdl:2060/20150010116. (Subscription required (help)).
  44. ^ The P/Halley Stream: Meteor Showers on Earth, Venus and Mars, by Apoistolos A. Christou, Geremie Vaubaillon and Paul Withers, Earth, Moon, and Planets, vol 102, # 1–4, doi:10.1007/s11038-007-9201-3
  45. ^ Lakdawalla, Emily. "Meteor showers on Titan: an example of why Twitter is awesome for scientists and the public". Retrieved 3 June 2013.
  46. ^ Watching meteors on Triton Archived 2014-03-27 at the Wayback Machine, W. Dean Pesnell, J.M. Grebowsky, and Andrew L. Weisman, Icarus, issue 169, (2004) pp. 482–491
  47. ^ IR Flashes induced by meteoroid impacts onto Pluto's surface, by I.B. Kosarev, I. V. Nemtchinov, Microsymposium, vol. 36, MS 050, 2002

External links

1490 Ch'ing-yang event

35.738152°N 107.632027°E / 35.738152; 107.632027

The Ch'ing-yang event of 1490 (also Ch'ing-yang, Chi-ing-yang or Chíing-yang meteor shower) is a presumed meteor shower or air burst in Qingyang in March or April 1490. The area was in the province of Shaanxi but is now part of Gansu. If a meteor shower did occur, it may have been the result of the disintegration of an asteroid during an atmospheric entry air burst.

A large number of deaths were recorded in historical Chinese accounts of the meteor shower, but have not been confirmed by researchers in the modern era. In the same year, Asian astronomers coincidentally discovered comet C/1490 Y1, a possible progenitor of the Quadrantid meteor showers.

169P/NEAT

169/NEAT is a periodic comet in the solar system. It is the parent body of the alpha Capricornids meteor shower. 169/NEAT may be related to comet P/2003 T12 (SOHO).169P is a low activity comet roughly a few kilometers in diameter. 169P and the smaller body P/2003 T12 likely fragmented from a parent body roughly 2900 years ago.

209P/LINEAR

209P/LINEAR is a periodic comet discovered on 3 February 2004 by Lincoln Near-Earth Asteroid Research (LINEAR) using a 1.0-metre (39 in) reflector. Initially it was observed without a coma and named 2004 CB as a minor planet or asteroid, but in March 2004 Robert H. McNaught observed a comet tail which confirmed it as a comet. It was given the permanent number 209P on 12 December 2008 as it was the second observed appearance of the comet. Prediscovery images of the comet, dating back to December 2003, were found during 2009. Arecibo imaging in 2014 showed the comet nucleus is peanut shaped and about 2.4 km in diameter. The comet has extremely low activity for its size and is probably in the process of evolving into an extinct comet.

209P/LINEAR was recovered on 31 December 2018 at magnitude 19.2 by Hidetaka Sato, but not officially announced yet.

21P/Giacobini–Zinner

Comet Giacobini–Zinner (official designation: 21P/Giacobini–Zinner) is a periodic comet in the Solar System.

It was discovered by Michel Giacobini (from Nice, France), who observed the comet in the constellation of Aquarius on December 20, 1900. It was recovered two passages later by Ernst Zinner (from Bamberg, Germany) while observing variable stars near Beta Scuti on October 23, 1913.

During its apparitions, Giacobini–Zinner can reach about the 7-8th magnitude, but in 1946 it underwent a series of outbursts that made it as bright as 5th magnitude. It is the parent body of the Giacobinids meteor shower (also known as the Draconids). The comet currently has an Earth-MOID of 0.035 AU (5,200,000 km; 3,300,000 mi).Giacobini–Zinner was the target of the International Cometary Explorer spacecraft, which passed through its plasma tail on September 11, 1985. In addition, Japanese space officials considered redirecting the Sakigake interplanetary probe toward a 1998 encounter with Giacobini–Zinner, but that probe lacked the propellant for the necessary maneuvers and the project was abandoned.

The comet nucleus is estimated to be 2.0 kilometers in diameter.

55P/Tempel–Tuttle

55P/Tempel–Tuttle (commonly known as Comet Tempel–Tuttle) is a periodic comet with an orbital period of 33 years. It fits the classical definition of a Halley-type comet with (20 years < period < 200 years). It was independently discovered by Wilhelm Tempel on December 19, 1865, and by Horace Parnell Tuttle on January 6, 1866.

It is the parent body of the Leonid meteor shower. In 1699, it was observed by Gottfried Kirch but was not recognized as a periodic comet until the discoveries by Tempel and Tuttle during the 1866 perihelion. In 1933, S. Kanda deduced that the comet of 1366 was Tempel–Tuttle, which was confirmed by Joachim Schubart in 1965. On 26 October 1366, the comet passed 0.0229 AU (3,430,000 km; 2,130,000 mi) from Earth.The orbit of 55P/Tempel–Tuttle intersects that of Earth nearly exactly, hence streams of material ejected from the comet during perihelion passes do not have to spread out over time to encounter Earth. The comet currently has an Earth-MOID of 0.008 AU (1,200,000 km; 740,000 mi). This coincidence means that streams from the comet at perihelion are still dense when they encounter Earth, resulting in the 33-year cycle of Leonid meteor storms. For example, in November 2009, the Earth passed through meteors left behind mainly from the 1466 and 1533 orbit.In February, 2016, two bolides detected by the NASA All-Sky Fireball Network were calculated to have orbits consistent with those of 55P, although with a node 100 degrees less than 55P. The reason for this is yet to be determined.

55P/Tempel–Tuttle is estimated to have a nucleus of mass 1.2×1013 kg and radius 1.8 km and a stream of mass 5×1012 kg.

8P/Tuttle

8P/Tuttle (also known as Tuttle's Comet or Comet Tuttle) is a periodic comet in the Solar System. It fits the classical definition of a Jupiter-family comet with an orbital period of less than 20 years, but does not fit the modern definition of (2 < TJupiter< 3). Perihelion was late January 2008, and as of February was visible telescopically to Southern Hemisphere observers in the constellation Eridanus. On December 30, 2007 it was in close conjunction with spiral galaxy M33. On January 1, 2008 it passed Earth at a distance of 0.25282 AU (37,821,000 km; 23,501,000 mi).Comet 8P/Tuttle is responsible for the Ursid meteor shower in late December.Predictions that the 2007 Ursid meteor shower could be expected to be stronger than usual due to the return of the comet, did not appear to materialize, as counts were in the range of normal distribution.

C/1861 G1 (Thatcher)

Comet C/1861 G1 (Thatcher) is a long-period comet with roughly a 415-year orbit discovered by A. E. Thatcher. It is responsible for the Lyrid meteor shower. Carl Wilhelm Baeker also independently found this comet. The comet passed about 0.335 AU (50,100,000 km; 31,100,000 mi) from the Earth on 1861-May-05 and last came to perihelion (closest approach to the Sun) on 1861-Jun-03.

Chelyabinsk meteor

The Chelyabinsk meteor was a superbolide that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately 20 m (66 ft) near-Earth asteroid with a speed of 19.16 ± 0.15 kilometres per second (60,000–69,000 km/h or 40,000–42,900 mph). It quickly became a brilliant superbolide meteor over the southern Ural region. The light from the meteor was brighter than the Sun, visible up to 100 km (62 mi) away. It was observed over a wide area of the region and in neighbouring republics. Some eyewitnesses also felt intense heat from the fireball.

Due to its high velocity and shallow angle of atmospheric entry, the object exploded in an air burst over Chelyabinsk Oblast, at a height of around 29.7 km (18.5 mi; 97,000 ft). The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26.2 km (16.3 mi), and many surviving small fragmentary meteorites, as well as a large shock wave. The bulk of the object's energy was absorbed by the atmosphere, with a total kinetic energy before atmospheric impact estimated from infrasound and seismic measurements to be equivalent to the blast yield of 400–500 kilotons of TNT (about 1.4–1.8 PJ) range – 26 to 33 times as much energy as that released from the atomic bomb detonated at Hiroshima.The object was undetected before its atmospheric entry, in part because its radiant was close to the Sun. Its explosion created panic among local residents, and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide's flash. Some 7,200 buildings in six cities across the region were damaged by the explosion's shock wave, and authorities scrambled to help repair the structures in sub-freezing temperatures.

With an estimated initial mass of about 12,000–13,000 metric tons (13,000–14,000 short tons, heavier than the Eiffel Tower), and measuring about 20 m (66 ft) in diameter, it is the largest known natural object to have entered Earth's atmosphere since the 1908 Tunguska event, which destroyed a wide, remote, forested, and very sparsely populated area of Siberia. The Chelyabinsk meteor is also the only meteor confirmed to have resulted in a large number of injuries. No deaths were reported.

The earlier-predicted and well-publicized close approach of a larger asteroid on the same day, the roughly 30 m (98 ft) 367943 Duende, occurred about 16 hours later; the very different orbits of the two objects showed they were unrelated to each other.

Draconids

The October Draconids, in the past also unofficially known as the Giacobinids, are a meteor shower whose parent body is the periodic comet 21P/Giacobini-Zinner. They are named after the constellation Draco, where they seemingly come from. Almost all meteors which fall towards Earth ablate long before reaching its surface. The Draconids are best viewed after sunset in an area with a clear dark sky.

The 1933 and 1946 Draconids had Zenithal Hourly Rates of thousands of meteors visible per hour, among the most impressive meteor storms of the 20th century. Rare outbursts in activity can occur when the Earth travels through a denser part of the cometary debris stream; for example, in 1998, rates suddenly spiked and spiked again (less spectacularly) in 2005. A Draconid meteor outburst occurred as expected on 2011 October 8, though a waxing gibbous Moon reduced the number of meteors observed visually. During the 2012 shower radar observations detected up to 1000 meteors per hour. The 2012 outburst may have been caused by the narrow trail of dust and debris left behind by the parent comet in 1959.

Geminids

The Geminids are a prolific meteor shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid with a "rock comet" orbit. This would make the Geminids, together with the Quadrantids, the only major meteor showers not originating from a comet. The meteors from this shower are slow moving, can be seen in December and usually peak around December 6–14, with the date of highest intensity being the morning of December 14. The shower is thought to be intensifying every year and recent showers have seen 120–160 meteors per hour under optimal conditions, generally around 02:00 to 03:00 local time. Geminids were first observed in 1862, much more recently than other showers such as the Perseids (36 AD) and Leonids (902 AD).

Leonids

The Leonids ( LEE-ə-nidz) 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 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 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. 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. 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 and to a lesser extent by radiation pressure from the sun, the Poynting–Robertson effect, 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 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. The Leonids also produce meteor storms (large outbursts) about every 33 years, which exceed 1,000 meteors per hour, in contrast to the sporadic background (5 to 8 meteors per hour) and the shower background (several per hour).

Lyrids

The April Lyrids (LYR, IAU shower number 6 ) are a meteor shower lasting from April 16 to April 26 each year. The radiant of the meteor shower is located in the constellation Lyra, near this constellation's brightest star, Alpha Lyrae (proper name Vega). Their peak is typically around April 22 each year.

The source of the meteor shower is particles of dust shed by the long-period Comet C/1861 G1 Thatcher. The April Lyrids are the strongest annual shower of meteors from debris of a long-period comet, mainly because as far as other intermediate long-period comets go (200–10,000 years), this one has a relatively short orbital period of about 415 years. The Lyrids have been observed and reported since 687 BC; no other modern shower has been recorded as far back in time.The shower usually peaks on around April 22 and the morning of April 23. Counts typically range from 5 to 20 meteors per hour, averaging around 10. As a result of light pollution, observers in rural areas will see more than observers in a city. Nights without a moon in the sky will reveal the most meteors. April Lyrid meteors are usually around magnitude +2. However, some meteors can be brighter, known as "Lyrid fireballs", cast shadows for a split second and leave behind smokey debris trails that last minutes.Occasionally, the shower intensifies when the planets steer the one-revolution dust trail of the comet into Earth's path, an event that happens about once every 60 years. This results in an April Lyrid meteor outburst. The one-revolution dust trail is dust that has completed one orbit: the stream of dust released in the return of the comet prior to the current 1862 return. This mechanism replaces earlier ideas that the outbursts were due to a cloud of dust moving in a 60-year orbit. In 1982, amateur astronomers counted 90 April Lyrids per hour at the peak and similar rates were seen in 1922. A stronger storm of up to 700 per hour occurred in 1803, observed by a journalist in Richmond, Virginia:

Shooting stars. This electrical [sic] phenomenon was observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets ...

Another such outburst, and the oldest known, the shower on March 23.7, 687 BC (proleptic Julian calendar) was recorded in Zuo Zhuan, which describes the shower as "On the 4th month in the summer in the year of xīn-mǎo (of year 7 of King Zhuang of Lu), at night, (the sky is so bright that some) fixed stars become invisible (because of the meteor shower); at midnight, stars fell like rain." (夏四月辛卯 夜 恆星不見 夜中 星隕如雨) In the Australian Aboriginal astronomy of the Boorong tribe, the Lyrids represent the scratchings of the Mallee fowl (represented by Vega), coinciding with its nest-building season.

Meteor Shower (TV series)

Meteor Shower (Chinese: 一起来看流星雨; pinyin: Yīqǐ Lái Kàn Liúxīngyǔ) is a 2009 Chinese television series starring Zheng Shuang, Hans Zhang, Yu Haoming, Vision Wei and Zhu Zixiao. It premiered on Hunan TV on August 8, 2009.

Due to the success and popularity of Japanese manga Hana Yori Dango and its franchise (Meteor Garden, Hana Yori Dango and Boys Over Flowers), Hunan TV decided to create a new series based on the same name. It is an unlicensed live-television drama production not authorized by Japanese publisher Shueisha. According to the producer, the series is only inspired by the manga and not based on it.

Meteor Shower (play)

Meteor Shower is a 2016 play written by Steve Martin. The play, a comedy, is set in 1993 in Ojai, California. It premiered on Broadway in 2017, where Amy Schumer received the production's sole Tony Award nomination.

Orionids

The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley's Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion, but they can be seen over a large area of the sky. Orionids are an annual meteor shower which last approximately one week in late October. In some years, meteors may occur at rates of 50–70 per hour.

Perseids

The Perseids are a prolific meteor shower associated with the comet Swift–Tuttle. The meteors are called the Perseids because the point from which they appear to hail (called the radiant) lies in the constellation Perseus.

Quadrantids

The Quadrantids (QUA) are a January meteor shower. The zenithal hourly rate (ZHR) of this shower can be as high as that of two other reliably rich meteor showers, the Perseids in August and the Geminids in December, yet Quadrantid meteors are not seen as often as meteors in these other two showers, because the peak intensity is exceedingly sharp, sometimes lasting only hours. Additionally, the meteors are quite faint (mean magnitude 3-6 mag).

Radiant (meteor shower)

The radiant or apparent radiant of a meteor shower is the celestial point in the sky from which (from the point of view of a terrestrial observer) the paths of meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus.

Meteor paths appear at random locations in the sky, but the apparent paths of two or more meteors from the same shower will converge at the radiant. The radiant is the vanishing point of the meteor paths, which are parallel lines in three-dimensional space, as seen from the perspective of the observer, who views a two-dimensional projection against the sky. The geometric effect is identical to crepuscular rays, where parallel sunbeams appear to converge.

A meteor that does not point back to the known radiant for a given shower is known as a sporadic and is not considered part of that shower.

Shower meteors may appear a short time before the radiant has risen in observer's eastern sky. The radiant in such cases is above the horizon at the meteor's altitude.

During the active period of most showers, the radiant moves nearly one degree eastwards, parallel to the ecliptic, against the stellar background each day. This is called the radiant’s diurnal drift, and is to a large degree due to the Earth’s own orbital motion around the Sun, which also proceeds at nearly one degree a day. As the radiant is determined by the superposition of the motions of Earth and meteoroid, the changing orbital direction of the Earth towards the east causes the radiant to move to the east as well.

Taurids

The Taurids are an annual meteor shower, associated with the comet Encke. The Taurids are actually two separate showers, with a Southern and a Northern component. The Southern Taurids originated from Comet Encke, while the Northern Taurids originated from the asteroid 2004 TG10. They are named after their radiant point in the constellation Taurus, where they are seen to come from in the sky. Because of their occurrence in late October and early November, they are also called Halloween fireballs.

Encke and the Taurids are believed to be remnants of a much larger comet, which has disintegrated over the past 20,000 to 30,000 years, breaking into several pieces and releasing material by normal cometary activity or perhaps occasionally by close encounters with the tidal force of Earth or other planets (Whipple, 1940; Klačka, 1999). In total, this stream of matter is the largest in the inner solar system. Since the meteor stream is rather spread out in space, Earth takes several weeks to pass through it, causing an extended period of meteor activity, compared with the much smaller periods of activity in other showers. The Taurids are also made up of weightier material, pebbles instead of dust grains.

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