Comet Kohoutek

Not to be confused with the short-period comet 75D/Kohoutek.

C/1973 E1 (Kohoutek)
A color image of Comet Kohoutek, with its tail pointed towards the bottom right with the coma at top left
Comet Kohoutek on 11 January 1974 as seen from Catalina Observatory
Discovery
Discovered byLuboš Kohoutek
Discovery date18 March 1973
Designations
Pronunciation/koʊˈhuːtɛk/
ko-HU-tek
/koʊhoʊtɛk/
ko-ho-tek[a]
1973f, 1973 XII
Orbital characteristics[4]
Epoch 24 December 1973 (JD 2442040.5)
Observation arc1.24 years (594 observations)
Aphelion98000 AU (inbound)
3700 AU (outbound)[4]
Perihelion0.1424249 AU[5]
Eccentricity0.999997 (inbound)
0.99992 (outbound)[4]
≈11 million yr (inbound)
≈ 80 thousand yr (outbound)[4]
Inclination14.30426°
258.48953°
28 December 1973[5][6]
37.79761°
Earth MOID0.029043 AU (4.34 million km)[6]
Physical characteristics
4.2 km (2.6 mi)[7]
Albedo0.67[7][b]
–3 (1973 perihelion)
0 (peak for ground observers)[8]
5.8 (total)
9.5 (nucleus)

Comet Kohoutek (formally designated C/1973 E1 and formerly as 1973 XII and 1973f)[c] is a comet that passed close to the Sun towards the end of 1973. Early predictions of the comet's peak brightness suggested that it had the potential to become one of the brightest comets of the 20th century, capturing the attention of the wider public and the press and earning the comet the moniker of "Comet of the Century". Although Kohoutek became rather bright, the comet was ultimately far dimmer than the optimistic projections: its apparent magnitude peaked at only –3 (as opposed to predictions of roughly magnitude –10) and it was visible for only a short period, quickly dimming below naked-eye visibility by the end of January 1974.[d]

The comet was discovered by and named after Luboš Kohoutek at the Hamburg Observatory on 18 March 1973; Kohoutek had been searching for Biela's Comet and had serendipitously discovered his eponymous comet while reviewing photographic plates for a different object. The comet was discovered farther away from the Sun than any previous comet. Conventional practices for predicting comet brightness led to generous projections of Comet Kohoutek's luminosity towards the end of 1973 and the beginning of 1974, leading to great anticipation within both scientific circles and the general public. Comet Kohoutek reached perihelion on 28 December 1973. Though the comet was then at its brightest, it could only be observed by scientific instrumentation and astronauts on Skylab. For most ground observers, Kohoutek only reached as bright as magnitude 0 when it emerged from the Sun's glare in January 1974. It quickly faded beyond naked-eye visibility later that month and was last observed in November 1974. Due to its underwhelming brightness after intense publicity, Kohoutek became synonymous with spectacular disappointment.

Because of its early detection and unique characteristics, numerous scientific assets were dedicated to observing Kohoutek during its 1973–74 traversal of the inner Solar System, making Kohoutek the most well-studied comet at the time; the resulting findings significantly advanced the understanding of comets. The identification of larger and more complex molecules emanating from Kohoutek alongside related but simpler chemical species confirmed the hypothesis that comets were composed of larger molecules that dissociated into simpler products. The significant presence of gasses and plasma expelled from Kohoutek supported the longstanding "dirty snowball" hypothesis concerning the composition of comet nuclei. The detection of water,[e] methyl cyanide, hydrogen cyanide, and silicon in Kohoutek were the first time such chemical species were observed in any comet. Its underwhelming display challenged longstanding assumptions regarding the light curve of similar comets entering the inner Solar System.

Kohoutek's highly eccentric orbit preceding its 1973 perihelion suggests that it may have been formed early in the formation of the Solar System or it may have originated from a different planetary system. Its orbital period may have been initially in the order of several million years, or its 1973 apparition may have been its first trek into the inner Solar System. Its nucleus has an estimated average radius of 2.1 km (1.3 mi).[7]

  1. ^ a b Chapman, Robert D. (September 1973). Comet Kohoutek: A Teacher's Guide With Student Activities (PDF) (Technical Memorandum). Greenbelt, Maryland: NASA. Archived (PDF) from the original on 6 July 2022. Retrieved 6 July 2022.
  2. ^ McElheny, Victor (7 January 1974). "Discoverer of Comet: Lubas Kohoutek". The New York Times. New York. p. 61. Archived from the original on 6 July 2022. Retrieved 6 July 2022.
  3. ^ Cite error: The named reference Time was invoked but never defined (see the help page).
  4. ^ a b c d "JPL Horizons Orbital Elements at epoch 1600 and 2500". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Archived from the original on 3 August 2022. Retrieved 3 August 2022. Solution using the Solar System Barycenter. Ephemeris Type: Elements and Center: @0 (To be outside planetary region, inbound epoch 1600 and outbound epoch 2500. Aphelia/orbital periods defined while in the planetary-region are misleading for knowing the long-term inbound/outbound solutions.)
  5. ^ a b "C/1973 E1 (Kohoutek)". Minor Planet Center. Archived from the original on 20 September 2022. Retrieved 7 July 2022.
  6. ^ a b "C/1973 E1 (Kohoutek)". Small-Body Database Lookup. Jet Propulsion Laboratory. Archived from the original on 7 February 2022. Retrieved 7 July 2022.
  7. ^ a b c Cite error: The named reference ODell1976 was invoked but never defined (see the help page).
  8. ^ "Brightest comets seen since 1935". International Comet Quarterly. Archived from the original on 18 September 2013. Retrieved 8 July 2022.
  9. ^ "Comet Names and Designations; Comet Naming and Nomenclature; Names of Comets". International Comet Quarterly. Archived from the original on 29 July 2012. Retrieved 7 July 2022.
  10. ^ Green, Daniel W E; Marsden, Brian G; Morris, Charles S (February 2001). "Brightness predictions for comets". Astronomy and Geophysics. 42 (1): 1.11–1.12. Bibcode:2001A&G....42a..11G. doi:10.1046/j.1468-4004.2001.0420011.11.x. S2CID 12022471.


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