 | |
| Discovery | |
|---|---|
| Discovered by: | Pierre Méchain |
| Discovery date: | 1786 |
| Alternate designations: | 1786 I; 1795; 1805; 1819 I; 1822 II; 1825 III; 1829; 1832 I; 1835 II; 1838; 1842 I; 1845 IV |
| Orbital characteristics A | |
| Epoch: | September 22, 2006 (JD 2454000.5) |
| Aphelion distance: | 4.11 AU |
| Perihelion distance: | 0.3302 AU |
| Semi-major axis: | 2.2178 AU |
| Eccentricity: | 0.8471 |
| Orbital period: | 3.30 a |
| Inclination: | 11.76° |
| Last perihelion: | 19 April 2007 |
| Next perihelion: | 6 August 2010 |
Comet Encke or Encke's Comet (official designation: 2P/Encke) is a periodic comet that completes an orbit of the sun once every three years — the shortest period of any known comet. It was first recorded by Pierre Méchain in 1786, but it was not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke; like Halley's Comet, it is unusual in being named after the calculator of its orbit rather than its discoverer.
Discovery
As its official designation implies, Encke's Comet was the first periodic comet discovered after Halley's Comet (designated 1P/Halley). Its orbit was calculated by Johann Franz Encke, who, through laborious calculations was able to link observations of comets in 1786 (designated 2P/1786 B1), 1795 (2P/1795 V1), 1805 (2P/1805 U1) and 1818 (2P/1818 W1) to the same object. In 1819 he published his conclusions in the journal Correspondance astronomique, and predicted correctly its return in 1822 (2P/1822 L1).
Characteristics
The diameter of the nucleus of Encke's Comet is 4.8 km [1]
Comets are on unstable orbits that evolve over time due to perturbations and outgassing. Given Encke's low orbital inclination near the ecliptic and brief orbital period of 3 years, the orbit of Encke is frequently perturbed by the inner planets.[2]
Observations
The failed CONTOUR mission was launched to study this comet, and also Schwassmann-Wachmann 3.
On April 20, 2007, the tail of Comet Encke was observed to be temporarily torn off by magnetic field disturbances caused by a Coronal Mass Ejection: a blast of solar particles from the sun. The tail grew back due to the continuous shedding of dust and gas by the comet.[3]
Meteor showers
Comet Encke is believed to be the originator of several related meteor showers known as the Taurids (which are encountered as the Northern and Southern Taurids across November, and the Beta Taurids in late June and early July).[4][5]
Near Earth object 2004 TG10 may be a fragment of Encke.[6]
Effects on Earth
More than one theory has associated Encke's Comet with impacts of cometary material on Earth, and with cultural significance.
Theorists arguing that the Bronze Age collapse of several civilizations in the Fertile Crescent was caused by a meteoric impact (perhaps evidenced by a large (unconfirmed) meteorite crater in Iraq identified as Umm al Binni lake)[7] have suggested that Encke's Comet is the remnant of the breakup of a larger body that produced the impactor.[citation needed]
The Tunguska event of 1908, likely caused by the impact of a cometary body, has also been postulated by a Czechoslovak astronomer as a fragment of Comet Encke.[8]
A theory holds that the ancient symbol of the swastika appeared in a variety of cultures across the world at a similar time, and could have been inspired by the appearance of a comet from head on, as the curved jets would be reminiscent of the swastika shape - see origin of the swastika. Comet Encke has sometimes been identified as the comet in question. In their 1982 book Cosmic Serpent (page 155) Victor Clube and Bill Napier reproduce an ancient Chinese catalogue of cometary shapes from the Mawangdui Silk Texts, which includes a swastika-shaped comet, and suggest that some of the comet drawings were related to the breakup of the progenitor of Encke and the Taurid meteoroid stream. Fred Whipple in his The Mystery of Comets (1985, page 163) points out that Comet Encke's polar axis is only 5 degrees from its orbital plane: such an orientation is ideal to have presented a pinwheel like aspect to our ancestors when Encke was more active.
References
- ^ NASA JPL Small-Body Database Browser on 2P
- ^ "JPL Close-Approach Data: 2P/Encke". 2008-09-30 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2P;orb=0;cov=0;log=0;cad=1#cad. Retrieved on 2009-05-07.
- ^ Astronomy Picture of the Day 2007 October 3
- ^ http://www.serve.com/~wh6ef/comets/meteors/showers/beta_taurids.html
- ^ Whipple, 1940; Klačka, 1999).
- ^ Porubčan, V.; Kornoš; Williams (2006). "The Taurid complex meteor showers and asteroids". Contributions of the Astronomical Observatory Skalnaté Pleso 36: 103–117. http://arxiv.org/abs/0905.1639. Retrieved on 2009-05-18.
- ^ Google Maps image
- ^ "The Tunguska object - A fragment of Comet Encke". Astronomical Institutes of Czechoslovakia. http://adsabs.harvard.edu/abs/1978BAICz..29..129K. Retrieved on 2007-10-15.
- Klačka, Jozef (1999). "Meteor Streams of Comet Encke. Taurid Meteor Complex". Abstract
- Whipple, F.L. (1940). "Photographic meteor studies. III. The Taurid shower." Proc. Amer. Phil. Soc., 83, 711-745.
- Master, S. and Woldai, T. (2004) The UMM Al Binni structure in the Mesopotamian marshlands of Southern Iraq, as a postulated late holocene meteorite impact crater : geological setting and new LANDSAT ETM + and Aster satellite imagery. Johannesburg, University of Witwatersrand, Economic Geology Research Institute (EGRI), 2004. EGRI - HALL : information circular 382, p. 21
- Master, S. and Woldai, T. (2004) Umm al Binni structure, southern Iraq, as a postulated late holocene meteorite impact crater : new satellite imagery and proposals for future research. Presented at the ICSU workshop : comet - asteroid impacts and human society, Santa Cruz de Tenerife, Canary Islands, Spain, November 27- December 2, 2004. p. 20
- Hamacher, D. W. (2005) "The Umm Al Binni Structure and Bronze Age Catastrophes", The Artifact: Publications of the El Paso Archaeological Society, Vol. 43
- Hamacher, D. W. (2006) "Umm al Binni lake: Effects of a possible Holocene bolide impact", Astronomical Society of Australia Meeting 40, #15
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