Comet Encke

Source: Wikipedia, the free encyclopedia.
2P/Encke
Semi-major axis
2.2187 AU
Eccentricity0.8469
Orbital period3.30 yr
3y 3m 27d (perihelion to perihelion)
Max. orbital speed69.5 km/s (250,000 km/h)[2]
Inclination11.34°
Argument of
periapsis		187.3°
Last perihelion22 October 2023[2]
Next perihelion9 February 2027[citation needed]
TJupiter3.025[1]
Earth MOID0.17 AU (25 million km)[1]
Physical characteristics
Dimensions4.8 km[1]

Comet Encke

perihelion (closest approach to the Sun). The diameter of the nucleus of Encke's Comet is 4.8 km.[1]

Discovery

As its official designation implies, Encke's Comet was the first periodic comet discovered after

Parramatta Observatory on 2 June 1822.[6]

Orbit

Comets are in unstable orbits that evolve over time due to

mean motion resonance with Jupiter, and it is possible that some of the larger fragments shed by the comet, or released by a larger progenitor of the comet, are trapped in this resonance.[7]

Encke's orbit gets as close as 0.173 AU (25.9 million km; 16.1 million mi) to Earth (minimum orbit intersection distance).[1] On 4 July 1997, Encke passed 0.19 AU from Earth, and on June 29, 2172, it will make a close approach of roughly 0.1735 AU.[1] On 18 November 2013, it passed 0.02496 AU (3.734 million km; 2.320 million mi) from Mercury.[1] Close approaches to Earth usually occur every 33 years.

Comet Encke has a

perihelion (closest approach to the Sun) of 0.34 AU (51 million km; 32 million mi), and at perihelion Comet Encke passes the Sun at 69.5 km/s (250,000 km/h).[2] Between 1769 and 2103, Comet Encke's perihelion distance only varies from 0.330 AU (in 2050) and 0.347 AU (in 1782).[8] Of the numbered comets less than 321P, only 96P/Machholz gets closer to the Sun.[9]

Observations

The comet has been observed at every perihelion since 1818 except 1944.[10][3]

An attempt to photograph the comet close to aphelion was made on 2 July 1913 using the

arcminutes from its then predicted position) but orbital uncertainties made it impossible to be sure of its identity.[11][12] A recalculation of Encke's orbit in the 1970s resulted in a calculated position only a few arcseconds (2.0 in ascension and 4.6 in declination) from the imaged object meaning the object probably was Encke.[12]

In March 1918 the

Greenwich 28-inch aperture telescope took observations of Encke (1917c).[13]

An observer of Encke's in March 1918 had this to say of the comet on March 12, comparing to the early March 9 observation, "The comet much shaper, brighter, smaller; its diameter was 1 1/2', magnitude 7.7 (B.D. scale). Its magnitude in the 6-inch Corbett was almost stellar, but in the 28 inch no definitive nucleus could be seen."[13]

A number of attempts were made to image the comet around the aphelion of 3 September 1972.[14][15] Elizabeth Roemer and G. McCorkle photographed the comet on 15 August.[14] R.E. McCrosky and C.-Y. Shao photographed it on 5 September and Elizabeth Roemer this time with M.R. Gonzales photographed the comet on 13 September.[14]

In 1980 Encke was the first comet to be detected by radar.[16]

In April 1984 the Pioneer Venus Orbiter observed the comet in ultra-violet and made measurements of its rate of water loss.[17]

The failed CONTOUR mission was launched to study this comet, and also Schwassmann–Wachmann 3.

Encke's Comet
loses its tail

On 20 April 2007,

STEREO-A observed the tail of Comet Encke to be temporarily torn off by magnetic field disturbances caused by a coronal mass ejection (a blast of solar particles from the Sun).[18] The tail grew back due to the continuous shedding of dust and gas by the comet.[19]

Meteor showers

A Spitzer image of Encke and its debris trail in infrared light

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).[20] A shower has similarly been reported affecting Mercury.[21]

Near-Earth object 2004 TG10 may be a fragment of Encke.[22]

Mercury

Measurements on board the NASA satellite MESSENGER have revealed Encke may contribute to seasonal meteor showers on Mercury. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument discovered seasonal surges of calcium since the probe began orbiting the planet in March 2011. The spikes in calcium levels are thought to originate from small dust particles hitting the planet and knocking calcium-bearing molecules into the atmosphere in a process called impact vaporization. However, the general background of interplanetary dust in the inner Solar System cannot, by itself, account for the periodic spikes in calcium. This suggests a periodic source of additional dust, for example, a cometary debris field.[23]

Effects on Earth

More than one theory has associated Encke's Comet with impacts of cometary material on Earth, and with cultural significance.

The Tunguska event of 1908 may have been caused by the impact of a cometary body and has also been postulated by Czechoslovakian astronomer Ľubor Kresák as possibly caused by a fragment of Comet Encke.[24]

A Han Dynasty silk comet atlas, featuring drawings of comets believed by Victor Clube and Bill Napier to be related to the breakup of Encke's Comet in the past

A theory holds that the ancient symbol of the

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.

Astronomers planned a 2019 search campaign for fragments of comet Encke which would have been visible from Earth as the Taurid swarm passed between July 5–11, and July 21 – August 10.[25] There were no reports of discoveries of any such objects.

Importance in the scientific history of luminiferous aether

Comet Encke (and Biela's Comet) had a role in scientific history in the generally discredited concept of luminiferous aether. As its orbit was perturbed and shortened, the shortening could only be ascribed to the drag of an "ether" through which it orbited in outer space. One reference reads:

Encke's comet is found to lose about two days in each successive period of 1,200 days. Biela's comet, with twice that length of period, loses about one day. That is, the successive returns of these bodies is found to be accelerated by this amount. No other cause for this irregularity has been found but the agency of the supposed ether.[26]

Encke's pole tumbles in an 81-year period, therefore it will accelerate for half that time, and decelerate for the other half of the time (since the orientation of the comets rotation to solar heating determines how its orbit changes due to outgassing forward or aft of the comet's course). The authors of this 1860 textbook of course could not know that the pole of the comet would tumble as it does over such a long period of time, or that outgassing would induce a thrust to change its course.

Gallery

  • A MESSENGER image of Comet Encke at its closest approach to Mercury, 17/11/2013[27] (NASA/JHUAPL/Carnegie Institution of Washington)
    A MESSENGER image of Comet Encke at its closest approach to Mercury, 17/11/2013[27] (NASA/JHUAPL/Carnegie Institution of Washington)

References

  1. ^ a b c d e f g h i j "JPL Small-Body Database Browser: 2P/Encke". Retrieved 2023-08-08.
  2. ^ a b c "Horizons Batch for 2P/Encke (90000090) on 2023-Oct-22" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Archived from the original on 2022-06-15. Retrieved 2022-06-15. (JPL#K204/20 Soln.date: 2022-May-23)
  3. ^
    doi:10.1086/111560
    . Retrieved 25 July 2020.
  4. ^ Herschel, Caroline Lucretia (1876). Herschel, Mrs. John (ed.). Memoir and Correspondence of Caroline Herschel. London: John Murray, Albemarle Street.
  5. ^ Biographical Encyclopedia of Astronomers. p. 924.
  6. ^ Kronk, Gary. "2P/Encke". Gary W. Kronk's Cometography. Retrieved 5 July 2014.
  7. doi:10.1093/mnrasl/slz076
    .
  8. ^ 2P/Encke past, present and future orbits by Kazuo Kinoshita
  9. ^ "JPL Small-Body Database Search Engine: numbered comets". JPL Solar System Dynamics. Retrieved 28 December 2020.
  10. ^ Rao, Joe (12 November 2013). "'Old Faithful' Comet Encke Makes Appearance in November Night Sky". SPACE.com. Retrieved 25 July 2020.
  11. ^
    Bibcode:1914PA.....22..607B
    . Retrieved 25 July 2020.
  12. ^
    doi:10.1086/111560
    . Retrieved 18 October 2020.
  13. ^
    ISSN 0035-8711
    .
  14. ^
    Bibcode:1972AcMPh..13...73B
    . Retrieved 2 September 2020.
  15. ISBN 9780521872263
    .
  16. doi:10.1016/j.icarus.2005.01.012
    . Retrieved 22 October 2020.
  17. ISBN 9780387493268
    .
  18. ^ "The Sun Rips Off a Comet's Tail". Science@NASA. 2007-10-01. Archived from the original on 2009-11-04. Retrieved 2009-10-20.
  19. ^ Nemiroff, R.; Bonnell, J., eds. (3 October 2007). "Comet Encke's Tail Ripped Off". Astronomy Picture of the Day. NASA.
  20. Whipple
    , 1940; Klačka, 1999).
  21. doi:10.1016/j.icarus.2014.11.035
    .
  22. Bibcode:2006CoSka..36..103P
    .
  23. ^ M. Killen & Joseph M. Hahn (17 December 2014). "Mercury Experiences Seasonal Meteor Showers, Say NASA Scientists". Web Article. Sci-News.com. Retrieved 29 December 2014.
  24. Bibcode:1978BAICz..29..129K
    .
  25. ^ Phil Plait (2019-05-14). "Could larger space rocks be hiding in the Beta Taurid Meteor stream? We may find out this summer". Bad Astronomy. Retrieved 2019-05-14.
  26. ^ "First principles of chemistry, for the use of colleges and schools". Philadelphia, H. C. Peck & T. Bliss. 1860.
  27. ^ "MESSENGER: MErcury Surface, Space ENvironment, GEochemistry, and Ranging". Archived from the original on 2013-12-05. Retrieved 2014-03-28.
  • 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

     http://www.itc.nl/library/Papers_2004/tech_rep/woldai_umm.pdf (1.56 MB)

  • 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

External links

Wikimedia Commons has media related to Comet Encke.


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