Просмотр кода страницы Английская Википедия:Comet Kohoutek

{{Английская Википедия/Панель перехода}}
{{Short description|Hyperbolic comet}}
{{Distinguish|text=the short-period comet [[75D/Kohoutek]]}}
{{good article}}
{{Use dmy dates|date=July 2022}}
{{Infobox planet
| name= C/1973 E1 (Kohoutek)
| alt_names= 1973f, 1973 XII
| pronounced= {{IPAc-en|k|oʊ|'|h|uː|t|ɛ|k}}<br />{{respell|ko|HU|tek}}<br />{{IPAc-en|k|oʊ|h|oʊ|t|ɛ|k}}<br />{{respell|ko|ho|tek}}{{efn|A teaching guide published by the Educational Programs Branch of the [[NASA Goddard Space Flight Center]] lists the pronunciation of Kohoutek as "KŌ-HÜ'-TEK".<ref name="Chapman1973">{{cite book |last1=Chapman |first1=Robert D. |title=Comet Kohoutek: A Teacher's Guide With Student Activities |type=Technical Memorandum |date=September 1973 |publisher=NASA |location=Greenbelt, Maryland |url=https://files.eric.ed.gov/fulltext/ED093617.pdf |access-date=6 July 2022 |archive-date=6 July 2022 |archive-url=https://web.archive.org/web/20220706222652/https://files.eric.ed.gov/fulltext/ED093617.pdf |url-status=live }}</ref>{{rp|iii}} A January&nbsp;1974 article in the ''[[New York Times]]'' provided the phonetic pronunciation "ko-ho-tek" without any accented syllables.<ref name="Discoverer">{{cite news |last1=McElheny |first1=Victor |title=Discoverer of Comet: Lubas Kohoutek |url=https://www.nytimes.com/1974/01/07/archives/discoverer-of-comet-lubos-kohoutek.html |access-date=6 July 2022 |work=The New York Times |date=7 January 1974 |location=New York |page=61 |archive-date=6 July 2022 |archive-url=https://web.archive.org/web/20220706222651/https://www.nytimes.com/1974/01/07/archives/discoverer-of-comet-lubos-kohoutek.html |url-status=live }}</ref> A special report on the comet in ''[[Time (magazine)|Time]]'' gave the phonetic pronunciation "ko-hoe-tek".<ref name="Time" />{{rp|1}}}}
| background = #FFE0C2
| image = Comet Kohoutek (S74-17688).jpg
| image_alt=A color image of Comet Kohoutek, with its tail pointed towards the bottom right with the coma at top left
| caption=Comet Kohoutek on 11 January 1974 as seen from [[Catalina Station|Catalina Observatory]]
| discoverer=[[Luboš Kohoutek]]
| discovered=18 March 1973
| orbit_ref = <ref name="Horizons">{{cite web
  |title = JPL Horizons Orbital Elements at epoch 1600 and 2500
  |url = https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271973+E1%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271600-01-01%27&STOP_TIME=%272500-01-01%27&STEP_SIZE=%27900%20years%27&CENTER=%27@0%27&OUT_UNITS=%27AU-D%27
  |work = [[JPL Horizons On-Line Ephemeris System]]
  |publisher = [[Jet Propulsion Laboratory]]
  |accessdate = 2022-08-03
  |archive-date = 3 August 2022
  |archive-url = https://web.archive.org/web/20220803213653/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271973+E1%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271600-01-01%27&STOP_TIME=%272500-01-01%27&STEP_SIZE=%27900%20years%27&CENTER=%27%400%27&OUT_UNITS=%27AU-D%27
  |url-status = live
  }} 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.)</ref>
| epoch=24 December 1973 ([[Julian day|JD]] 2442040.5)
| observation_arc= 1.24 years (594 observations)
| aphelion=98000 [[Astronomical unit|AU]] (inbound)<br />3700 AU (outbound)<ref name="Horizons"/>
| perihelion=0.1424249 AU<ref name="MPC">{{cite web |title=C/1973 E1 (Kohoutek) |url=https://www.minorplanetcenter.net/db_search/show_object?object_id=C%2F1973+E1 |publisher=Minor Planet Center |access-date=7 July 2022 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013924/https://www.minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=C%2F1973+E1 |url-status=live }}</ref>
| time_periastron = 28 December 1973<ref name="MPC"/><ref name="JPL"/>
| eccentricity=0.999997 (inbound)<br />0.99992 (outbound)<ref name="Horizons"/>
| period = ≈11 million yr (inbound)<br/>≈ 80 thousand yr (outbound)<ref name="Horizons"/>
| inclination=14.30426°
| asc_node=258.48953°
| arg_peri=37.79761°
| moid= {{convert|0.029043|AU|e6km|sigfig=3|abbr=unit}}<ref name="JPL">{{cite web |title=C/1973 E1 (Kohoutek) |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1973E1 |website=Small-Body Database Lookup |publisher=Jet Propulsion Laboratory |access-date=7 July 2022 |archive-date=7 February 2022 |archive-url=https://web.archive.org/web/20220207193336/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=C%2F1973%20E1 |url-status=live }}</ref>
| dimensions= 
| mean_diameter= {{cvt|4.2|km}}<ref name="ODell1976" />
| albedo= 0.67<ref name="ODell1976" />{{efn|Most comets have an albedo of around 0.04.}}
| rotation=
| magnitude= –3 {{small|(1973 perihelion)}}<br />0 {{small|(peak for ground observers)}}<ref name="ICQBrightest">{{cite web |title=Brightest comets seen since 1935 |url=http://www.icq.eps.harvard.edu/brightest.html |publisher=International Comet Quarterly |access-date=8 July 2022 |archive-date=18 September 2013 |archive-url=https://web.archive.org/web/20130918011207/http://www.icq.eps.harvard.edu/brightest.html |url-status=live }}</ref>
| abs_magnitude= 5.8 {{small|(total)}}<br />9.5 {{small|(nucleus)}}
}}
'''Comet Kohoutek''' ([[Astronomical naming conventions#Comets|formally designated]] '''C/1973 E1''' and formerly as '''1973 XII''' and '''1973f'''){{efn|The designation ''C/1973 E1'' reflects the modern comet designation scheme adopted by the International Astronomical Union in 1995, and indicates that Comet Kohoutek appeared once and was the first comet discovered in the first half of March&nbsp;1973. However, during the time of perihelion the comet was contemporaneously designated as ''1973f'' as it was sixth comet discovered in 1973, or alternatively as ''1973 XII'' as the comet was the twelfth to reach perihelion in 1973.<ref name="CometNames">{{cite web |title=Comet Names and Designations; Comet Naming and Nomenclature; Names of Comets |url=http://www.icq.eps.harvard.edu/cometnames.html |publisher=International Comet Quarterly |access-date=7 July 2022 |archive-date=29 July 2012 |archive-url=https://archive.today/20120729193809/http://www.icq.eps.harvard.edu/cometnames.html |url-status=live }}</ref><ref name="Green et al. 2001">{{cite journal |last1=Green |first1=Daniel W E |last2=Marsden |first2=Brian G |last3=Morris |first3=Charles S |title=Brightness predictions for comets |journal=Astronomy and Geophysics |date=February 2001 |volume=42 |issue=1 |pages=1.11–1.12 |doi=10.1046/j.1468-4004.2001.0420011.11.x |bibcode=2001A&G....42a..11G |s2cid= 12022471|doi-access=free }}</ref><ref name="Chapman1973" />{{rp|3}}}} 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 [[Great comet|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|naked-eye visibility]] by the end of January&nbsp;1974.{{efn|All mentions of [[apparent magnitude]] in this article refer to brightness in visible light unless otherwise noted.}}

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 plate]]s 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 [[Skylab 4|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&nbsp;1974. It quickly faded beyond naked-eye visibility later that month and was last observed in November&nbsp;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 [[dissociation (chemistry)|dissociated]] into simpler products. The significant presence of gasses and plasma expelled from Kohoutek supported the longstanding "[[comet#Scientific approach|dirty snowball]]" hypothesis concerning the composition of comet nuclei. The detection of water,{{efn|name=H2O}} [[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 [[orbital eccentricity|eccentric]] orbit preceding its 1973&nbsp;perihelion suggests that it may have been formed early in the [[Formation and evolution of the Solar System|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 [[comet nucleus|nucleus]] has an estimated average radius of {{cvt|2.1|km}}.<ref name="ODell1976" />

== Discovery ==
[[File:S74-15064 Lobus Kohoutek.jpg|left|thumb|Luboš Kohoutek, eponymous discoverer of Comet Kohoutek, at the [[Christopher C. Kraft Jr. Mission Control Center|mission control center]] at [[Johnson Space Center]] speaking with the astronauts of [[Skylab 4]] during the passage of the comet in January&nbsp;1974|alt=Photograph of Luboš Kohoutek at the mission control center at the Johnson Space Center]]

The comet was discovered on 18 March 1973 by Czech astronomer [[Luboš Kohoutek]] after reviewing twice-exposed [[photographic plate]]s taken by the {{cvt|80|cm}} aperture [[Schmidt camera]] at the [[Hamburg Observatory]] in [[Bergedorf]] on 7 March and 9 March. The object remained evident and was displaced slightly towards the west-northwest in the latter plate, confirming that it was moving against the background stars and not a transient or erroneous feature.<ref name="Hendrie2000">{{cite journal |last1=Hendrie |first1=Michael J. |title=Comet Kohoutek 1973f |journal=Journal of the British Astronomical Association |date=February 2000 |volume=110 |pages=9–19 |doi=|arxiv=|bibcode=2000JBAA..110....9H|s2cid=}}</ref><ref name="Chapman1973" />{{rp|1}} Upon discovery, the comet had an [[apparent magnitude]] between 15.5 and 16 and lay in the constellation of [[Hydra (constellation)|Hydra]]; Kouhoutek described the comet as initially "diffuse with central condensation".<ref name="Kohoutek1974">{{cite journal |last1=Kohoutek |first1=Luboš |title=On the discovery of Comet Kohoutek (1973f) |journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=491–492 |doi=10.1016/0019-1035(74)90011-6|bibcode=1974Icar...23..491K|s2cid=120800003}}</ref><ref name="Stoyan2015">{{cite book |last1=Stoyan |first1=Ronald |title=Atlas of Great Comets |date=2015 |publisher=Cambridge University Press |location=Cambridge, United Kingdom |isbn=9781316195727 |pages=166–169 |edition=English |url=https://books.google.com/books?id=VEF5BgAAQBAJ |via=Google Books |access-date=6 July 2022 |chapter=Comet Kohoutek 1973/74 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013924/https://www.google.com/books/edition/Atlas_of_Great_Comets/VEF5BgAAQBAJ |url-status=live }}</ref> The comet was located near the orbit of [[Jupiter]] around the time of discovery, 4.7&nbsp;[[astronomical unit]]s (AU) away from the Sun and 4&nbsp;AU from the Earth.<ref name="Biermann1973" /><ref name="Hendrie2000" /> As a result, the comet was moving very slowly towards the west-northwest at around 0.2° per day.<ref name="Marsden1974">{{cite journal |last1=Marsden |first1=Brian G. |title=Comets in 1973 |journal=Quarterly Journal of the Royal Astronomical Society |date=December 1974 |volume=15 |pages=433–460 |bibcode=1974QJRAS..15..433M}}</ref> Based on subsequent orbital calculations, the discovery of the comet occurred roughly seven months before [[perihelion]].<ref name="BensonCompton1981">{{cite book |last1=Benson |first1=Charles Dunlap |last2=Compton |first2=William David |title=Living and Working in Space: A History of Skylab |publisher=NASA |location=Washington, D.C. |url=https://history.nasa.gov/SP-4208/app.f.htm |access-date=14 July 2022 |chapter=Appendix F: Comet Kohoutek |archive-date=28 August 2021 |archive-url=https://web.archive.org/web/20210828011248/https://history.nasa.gov/SP-4208/app.f.htm |url-status=live }}</ref> The discovery of a comet at such large distances and long leadtimes before their perihelia was unprecedented;<ref name="Roemer1976a">{{cite journal |last1=Roemer |first1=Elizabeth |title=Luminosity and Astrometry of Comets: A Review |journal=The Study of Comets, Part 1 |url=https://ntrs.nasa.gov/api/citations/19760013982/downloads/19760013982.pdf |bibcode=1976NASSP.393..380R |publisher=NASA |pages=380–409 |date=1976 |volume=393 |access-date=9 July 2022 |archive-date=26 May 2022 |archive-url=https://web.archive.org/web/20220526093807/https://ntrs.nasa.gov/api/citations/19760013982/downloads/19760013982.pdf |url-status=live }}</ref><ref name="MSFC">{{cite tech report |title=MSFC Skylab Kohoutek Project Report |type=NASA Technical Memorandum |url=https://ntrs.nasa.gov/api/citations/19740027130/downloads/19740027130.pdf |publisher=NASA Marshall Space Flight Center |access-date=8 July 2022 |location=Huntsville, Alabama |date=October 1974 |id=NASA TM X-64880 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013924/https://ntrs.nasa.gov/api/citations/19740027130/downloads/19740027130.pdf |url-status=live }}</ref>{{rp|12}} at the time comets were rarely discovered at such large distances from the Sun as most were too faint to be detected.<ref name="Whipple1976">{{cite journal |last1=Whipple |first1=Fred L. |title=Comet Kohoutek in Retrospect |journal=Proceedings of the American Philosophical Society |date=5 February 1976 |volume=120 |issue=1 |pages=1–6|bibcode=1976PAPhS.120....1W|s2cid=236815067|jstor=986346}}</ref> Kohoutek transmitted his findings to the [[Central Bureau for Astronomical Telegrams]] on 19&nbsp;March, leading to the announcement of his discovery in [[IAU circular|circular 2511]] of the [[International Astronomical Union]]. It was the sixth comet discovered in 1973 and thus given the designation ''1973f''.<ref name="Kohoutek1974" /><ref name="Chapman1973" />{{rp|3}} Due to increasing public attention towards the comet, the comet was also named ''Comet Kohoutek'' in honor of its discoverer Luboš Kohoutek.<ref name="Chapman1973" />{{rp|3}}

The comet's discovery was serendipitous: beginning in 1971, Kohoutek had been searching for [[Biela's Comet]], which had [[lost comet|not been observed]] since 1852. Using the Hamburg Observatory's Schmidt camera, the initial search in October and November&nbsp;1971 found 52&nbsp;[[minor planet]]s in a roughly 180-square-degree region of the sky. Preliminary orbits were determined for 35 of these newly-found objects, of which 15 were targeted for observation between January and April&nbsp;1973. The 7&nbsp;March photographic plate was intended to feature one of the objects, [[main-belt]] asteroid 1971&nbsp;UG,{{efn|1971 UG is a [[main-belt]] asteroid about 10 km in diameter discovered by Kohoutek on 26 October 1971.<ref>{{Cite web |url=https://www.minorplanetcenter.net/db_search/show_object?object_id=8606 |title=MPC object 8606 |access-date=5 August 2022 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304120740/http://minorplanetcenter.net/db_search/show_object?object_id=8606 |url-status=live }}</ref> It is also known as 1980 RT3 and 1995 UZ44. It has been observed every year since 1998.}} but instead captured Comet Kohoutek.<ref name="Kohoutek1974" /> Comet Kohoutek was later [[precovery|precovered]] on a photographic plate taken on 28&nbsp;January, exhibiting a similar brightness as during its discovery and a heliocentric distance of  5.2&nbsp;AU.<ref name="Biermann1973">{{cite journal |last1=Biermann |first1=L. |title=Comet Kohoutek |journal=Nature |date=December 1973 |volume=246 |issue=5433 |pages=400–402 |doi=10.1038/246400a0|arxiv=|bibcode=1973Natur.246..400B|s2cid=42320124}}</ref><ref name="Marsden1974" /> The plate was also taken in pursuit of 1971&nbsp;UG.<ref name="Marsden1974" /> The comet was the second discovered by Kohoutek in 1973; the first had been discovered on 28&nbsp;February during the same search for Biela's Comet and was also found on a photographic plate that was intended to contain another of the newly discovered minor planets.<ref name="Kohoutek1974" />{{efn|The first comet discovered by Kohoutek in 1973 was designated ''1973e'' (modern designation: C/1973 D1) and has an orbital period of about 36,751&nbsp;years. It reached its perihelion on 7 June 1973 and was last observed in October&nbsp;1973.<ref name="JPL_C1973D1">{{cite web |title=C/1973 D1 (Kohoutek) |url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=1973%20D1 |website=Small-Body Database Lookup |publisher=Jet Propulsion Laboratory |access-date=4 September 2022 |archive-date=7 February 2022 |archive-url=https://web.archive.org/web/20220207193336/https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=1973%20D1 |url-status=live }}</ref><ref name="Marsden1974" />}}

== Orbit ==
[[File:Comet Kohoutek orbit p391.svg|thumb|The orbits and timings of Comet Kohoutek near its perihelion (in red) and the Earth (in blue)|alt=Diagram of Comet Kohoutek's approach of the Sun]]
[[Orbital elements]] for Comet Kohoutek were [[Orbit determination|calculated]] by British astronomer [[Brian G. Marsden]] soon after the comet's discovery, using photographic plates taken of the comet on 7 March, 9 March, and 21 March.<ref name="Kohoutek1974" /> These calculations suggested that Kohoutek had a [[List of near-parabolic comets|nearly parabolic orbit]] lying close to the [[ecliptic]] with an [[Eccentricity (astronomy)|eccentricity]] between 0.9999 and 1 and an [[orbital inclination|inclination]] of 14.3°. Such an orbit meant that the comet would approach very close to the Sun, with [[perihelion]] occurring on 28&nbsp;December 1973 at a distance of only 0.14&nbsp;AU.<ref name="MPC"/> The close perihelion and the comet's brightness upon discovery were analogous to other comets that had become very bright. The calculated orbit also suggested that Kohoutek's close pass of the Sun could be its first traversal of the inner [[Solar System]].<ref name="Biermann1973" /><ref name="Stoyan2015" /> Marsden's calculated orbit placed Kohoutek's initial [[Semi-major and semi-minor axes|semi-major axis]] at 50,000&nbsp;AU.<ref name="Whipple1989" /><ref name="Horizons"/> Alternatively, Kohoutek may have had an orbital period of 4&nbsp;million years before experiencing the [[Perturbation (astronomy)|gravitational perturbations]] from the Solar System's planets, which would make Kohoutek a [[long-period comet]].<ref name="Dubin1975">{{cite book |last1=Dubin |first1=Maurice |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |bibcode=1975NASSP.355.....G |chapter=Foreword|journal=NASA Special Publication |volume=355 |editor-last1=Gary|editor-first1=Gilmer}}</ref> This idea was supported by [[Stephen P. Maran]], the head of NASA's efforts to study Kohoutek. Maran believed that the comet initially had a perihelion farther out than the orbit of Jupiter until it was gravitationally perturbed by a passing star, lowering its perihelion to within the orbit of [[Mercury (planet)|Mercury]] and its orbital period to 4–5&nbsp;million years; additional gravitational interactions between the comet and the planets would have shortened the comet's orbital period further to about 75,000&nbsp;years.<ref name="ChristmasCometYielding" /><ref name="Horizons"/> The closest approach of Kohoutek to Earth occurred on 15 January 1974 and be no nearer than 0.8&nbsp;AU, preventing the resolution of its nucleus via Earth-based instruments.<ref name="Lyttleton1973">{{cite journal |last1=Lyttleton |first1=R. A. |title=Prospects for Comet Kohoutek (1973f) |journal=Nature |date=September 1973 |volume=245 |issue=5422 |pages=200–201 |doi=10.1038/245200a0|arxiv=|bibcode=1973Natur.245..200L|s2cid=4255566}}</ref><ref name="Stokley1973">{{cite journal |last1=Stokley |first1=James |title=Kohoutek Comet Now Visible |journal=Science News |date=22 December 1973 |volume=104 |issue=25/26 |page=400 |doi=10.2307/3958267 |bibcode=|s2cid=86901151|jstor=3958267}}</ref>

Both the [[Minor Planet Center]] and the [[JPL Small-Body Database]] list Kohoutek as having a [[hyperbolic trajectory]] when it was near perihelion,<ref name="MPC" /><ref name="JPL" /> but the orbit became bound to the Sun by 1978.<ref name="Horizons-heliocentric">{{cite web
  | title=Osculating Orbital Elements for Comet C/1973 E1 (Kohoutek)
  | author=[[JPL Horizons On-Line Ephemeris System|Horizons]] output
  | url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271973+E1%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%271974-01-01%27&STOP_TIME=%271992-01-01%27&STEP_SIZE=%271%20year%27&CENTER=%27@Sun%27&OUT_UNITS=%27AU-D%27 }}</ref> The comet is not expected to return for about 75,000 years.<ref name="Horizons"/> Some of the meteoroids ejected by Kohoutek during its initial approach, particularly those with diameters no smaller than {{cvt|0.2|mm}}, were placed into stable orbits around the Sun.<ref name="Fulle1988" />

As seen from Earth between 1973 and 1974, the comet took a southeastward path across the sky similar to [[Comet Halley]]'s path between 1985 and 1986. The visibility of the comet was most favorable to observers in the Southern Hemisphere and the [[tropics]]. It was in the evening sky from the time of its discovery to the end of September&nbsp;1973, after which the comet became a morning sky object. After being positioned in Hydra upon the time of discovery, Comet Kohoutek moved across the constellations of [[Sextans (constellation)|Sextans]], [[Leo (constellation)|Leo]], [[Crater (constellation)|Crater]], [[Corvus (constellation)|Corvus]], [[Virgo (constellation)|Virgo]], [[Libra (constellation)|Libra]], [[Scorpius (constellation)|Scorpius]], and [[Sagittarius (constellation)|Sagittarius]] by the end of 1973. Kohoutek was near the boundary of Sagittarius and [[Ophiuchus (constellation)|Ophiuchus]] during perihelion when it was [[appulse|visually separated]] from the Sun by only 0.5°. In 1974, the comet moved across the constellations of [[Capricorn (constellation)|Capricorn]], [[Aquarius (constellation)|Aquarius]], [[Pisces (constellation)|Pisces]], and [[Taurus (constellation)|Taurus]].<ref name="Hendrie2000" /><ref name="Stoyan2015" /> {{asof|2022}}, comet Kohoutek is about {{Convert|74|AU|e9km|abbr=unit|sigfig=2|lk=on}} from the Sun in the constellation of [[Gemini (constellation)|Gemini]].<ref name="Horizons2022"/> It is currently receding from the Sun at {{convert|4.8|km/s|mph|abbr=on}}.<ref name="Horizons2022">{{cite web
  |title=Horizons Batch for Heliocentric distance for 2022-2030
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271973+E1%27&START_TIME=%272022-01-01%27&STOP_TIME=%272030-01-01%27&STEP_SIZE=%271%20year%27&QUANTITIES=%2719,22,29,39%27
  |accessdate=2022-08-03
  |archive-date=4 August 2022
  |archive-url=https://web.archive.org/web/20220804023845/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%271973+E1%27&START_TIME=%272022-01-01%27&STOP_TIME=%272030-01-01%27&STEP_SIZE=%271%20year%27&QUANTITIES=%2719%2C22%2C29%2C39%27
  |url-status=live
  }}</ref>

== Structure and composition ==
[[File:Kohoutek-uv.jpg|thumb|left|False color image of Comet Kohoutek as photographed with a far-ultraviolet electrographic camera during a Skylab spacewalk on 25 December 1973|alt=False color image of the comet, which appears as a bright object at center-right]]
Kohoutek's highly eccentric orbit and possible lack of prior planetary or solar interactions suggest that the comet may have been a primordial body of either the Solar System or that it may have originated from another [[planetary system]].<ref name="Dubin1975" /> The comet may have also originated from the [[Oort cloud]].<ref name="Whipple1976" /> A 1976 analysis of photometry and water loss rates estimated that the [[Comet nucleus|nucleus]] had a radius of around {{cvt|2.1|km}} and an [[albedo]] of around 0.67.<ref name="ODell1976" /> A photometric analysis of Kohoutek, using Mercury as a reference, established an upper limit of {{cvt|30|km}} for the diameter of Kohoutek's nucleus.<ref name="Ney1974b">{{cite journal |last1=Ney |first1=Edward P. |title=Multiband photometry of Comets Kohoutek, Bennett, Bradfield, and Encke |journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=551–560 |doi=10.1016/0019-1035(74)90018-9 |bibcode=1974Icar...23..551N|s2cid=121046622}}</ref> An attempt to detect a [[radar]] echo from Kohoutek's nucleus using the [[Haystack Observatory#Haystack Radio Telescope|Haystack Radio Telescope]] received no radar returns, constraining the nucleus's size to under {{cvt|250|km}}.<ref name="Chaisson et al. 1975">{{cite journal |last1=Chaisson |first1=E.J. |last2=Ingalls |first2=R.P. |last3=Rogers |first3=A.E.E. |last4=Shapiro |first4=I.I. |title=Upper limit on the radar cross section of the comet Kohoutek |journal=Icarus |date=February 1975 |volume=24 |issue=2 |pages=188–189 |doi=10.1016/0019-1035(75)90096-2 |bibcode=1975Icar...24..188C |s2cid=119908758}}</ref> The comet has a total [[absolute magnitude#Solar System bodies (H)|absolute magnitude]] (at 1 AU) of 5.8 and a nuclear absolute magnitude of 9.5.<ref name="JPL" /> During Kohoutek's 1973–74 apparition, its tail's width ranged from around {{cvt|30000|km}} near the coma to {{cvt|300000|km}} farther away. Detection of positive [[carbon monoxide]] ions showed that the tail was at least 20&nbsp;million km (12&nbsp;million mi) in length.<ref name="Jockers1985" />  A more yellow and orange appearance of the dust tail of Kohoutek during its perihelion{{snd}}as observed by astronauts on Skylab{{snd}}was likely the result of [[Light scattering by particles|light scattering]] by [[basalt]]ic dust particles with sizes of around 0.5&nbsp;μm. The tail lacked color closer to the coma near perihelion, indicating a large distribution of particle sizes and resulting in a white appearance.<ref name="Jambor1975">{{cite book |last1=Jambor |first1=B. J. |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |chapter=Dynamical and Colorimetric Study of the Dust Tail of Comet Kohoutek|journal=NASA Special Publication |volume=355 |editor-last1=Gary|editor-first1=Gilmer|bibcode=1975NASSP.355..209J|pages=209–216}}</ref> Observations from the [[Magdalena Ridge Observatory|Joint Observatory for Cometary Research]] in [[Socorro, New Mexico]], were able to trace the blue ion tail of Kohoutek{{snd}}featuring more prominently than the comet's dust tail{{snd}}to a distance of {{cvt|0.333|AU}} away from the nucleus.<ref name="Brandt">{{cite book |last1=Brandt |first1=John C. |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |chapter=Large-Scale Observations of the Ion Tail from the Joint Observatory for Cometary Research|journal=NASA Special Publication |volume=355 |editor-last1=Gary|editor-first1=Gilmer|bibcode=1975NASSP.355...15B|pages=15–18}}</ref> The particle density within the tail several million miles away from the nucleus was about 10&nbsp;ions per cubic centimeter, while the maximum electron density within the tail was around 20,000&nbsp;electrons per cubic centimeter.<ref name="Jockers1985">{{cite journal |last1=Jockers |first1=K |title=The ion tail of Comet Kohoutek 1973 XII during 17 days of solar wind gusts |journal=Astronomy and Astrophysics Supplement Series |date=December 1985 |volume=62 |issue=4 |pages=791–838 |bibcode=1985A&AS...62..791J|s2cid=120216058}}</ref><ref name="WrightNelson1979">{{cite journal |last1=Wright |first1=C.S. |last2=Nelson |first2=G.J. |title=Comet plasma densities deduced from refraction of occulted radio sources |journal=Icarus |date=April 1979 |volume=38 |issue=1 |pages=123–135 |doi=10.1016/0019-1035(79)90092-7 |bibcode=1979Icar...38..123W |s2cid=122229848}}</ref> At a distance of around 0.5&nbsp;AU from the Sun, the plasma outflow in Kohoutek's tail generated a weak [[magnetic field]] with a strength comparable to the [[interplanetary magnetic field]].<ref name="Ershkovich1976">{{cite journal |last1=Ershkovich |first1=A.I. |title=Solar wind interaction with the tail of Comet Kohoutek |journal=Planetary and Space Science |date=March 1976 |volume=24 |issue=3 |pages=287–291 |doi=10.1016/0032-0633(76)90025-8 |bibcode=1976P&SS...24..287E |s2cid=121782993}}</ref>

[[File:Comet Kohoutek at perihelion from Skylab with coronagraph.jpg|thumb|Sequence of images of Kohotuek at perihelion taken via coronagraph|alt=A collage of eight images of the comet as it passed by the sun. The sun is blocked out by the imaging instrument.]]
Analyses of Kohoutek have provided different assessments of the scale of the comet's release of dust and gas, with some suggesting that Kohoutek is relatively dust-rich (and consequently gas-poor) and others suggesting that the comet is relatively dust-poor (and consequently gas-rich).<ref name="deAlmeida1996" /><ref name="Biermann1973" /> Between 16 and 29&nbsp;January 1974, the nucleus was expelling roughly 1,675&nbsp;kg of gas and 16,000&nbsp;kg of dust per second on average.<ref name="deAlmeida1996">{{cite journal |last1=de Almeida |first1=A.A. |title=Photoelectric photometry of comet Kohoutek (1973 XII = C/1973 E1): the production rates of CN, C2, and solid refractory particles typical of dynamically new comets |journal=Planetary and Space Science |date=April 1996 |volume=44 |issue=4 |pages=295–304 |doi=10.1016/0032-0633(95)00130-1 |bibcode=1996P&SS...44..295D|s2cid=123609347}}</ref><ref name="Lisse et al. 1998">{{cite journal |last1=Lisse |first1=C. M. |last2=A'Hearn |first2=M. F. |last3=Hauser |first3=M. G. |last4=Kelsall |first4=T. |last5=Lien |first5=D. J. |last6=Moseley |first6=S. H. |last7=Reach |first7=W. T. |last8=Silverberg |first8=R. F. |title=Infrared Observations of Comets by COBE |journal=The Astrophysical Journal |date=April 1998 |volume=496 |issue=2 |pages=971–991 |doi=10.1086/305397 |bibcode=1998ApJ...496..971L |s2cid=119698136|doi-access=free }}</ref> The predominance of dust was thought to have been demonstrated by the emergence of an [[antitail]] when the Earth passed through the plane of Kohoutek's orbit; antitails are composed of relatively large solid particles that disperse around the nucleus.<ref name="Whipple1976" /> Particles in the antitail had radii larger than approximately 10&nbsp;μm while particle radii in the coma and tail were less than 1&nbsp;μm. At a distance of 0.23&nbsp;AU from the Sun, the less reflective material in the coma had an [[effective temperature]] of 720 ± 20&nbsp;[[Kelvin (unit)|K]] while the material in the antitail featured effective temperatures of 565 ± 10&nbsp;K.<ref name="Ney1974">{{cite journal |last1=Ney |first1=Edward P. |title=Infrared Observations of Comet Kohoutek Near Perihelion |journal=The Astrophysical Journal |date=May 1974 |volume=189 |pages=L141–L142 |doi=10.1086/181486 |bibcode=1974ApJ...189L.141N|s2cid=120737009|doi-access=free }}</ref>  Intense solar heating near the time of perihelion greatly reduced the size of particles in the antitail, leaving behind only particles with initial sizes of at least 100–150&nbsp;μm and leading to a decrease in the antitail's brightness following perihelion.<ref name="SekaninaMiller1976">{{cite journal |last1=Sekanina |first1=Zdenek |last2=Miller |first2=Freeman D. |title=On the nature of the anti-tail of Comet Kohoutek (1973f). II. Comparison of the working model with ground-based photographic observations |journal=Icarus |date=January 1976 |volume=27 |issue=1 |pages=135–146 |doi=10.1016/0019-1035(76)90190-1 |bibcode=1976Icar...27..135S |hdl=2027.42/21881 |s2cid=56252570|hdl-access=free }}</ref> [[Silicate]]s were also detected in the tail and antitail via [[infrared astronomy]].<ref name="Whipple1976" /><ref name="AHearnCowan1975" /><ref name="Gatley et al. 1974">{{cite journal |last1=Gatley |first1=I. |last2=Becklin |first2=E.E. |last3=Neugebauer |first3=G. |last4=Werner |first4=M.W. |title=Infrared observations of Comet Kohoutek (1973f) |journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=561–565 |doi=10.1016/0019-1035(74)90019-0 |bibcode=1974Icar...23..561G |s2cid=121839693}}</ref> On 2 December 1973, Kohoutek was expelling about 900&nbsp;billion dust molecules per second. However, Kohoutek became less dusty following perihelion, with dust production lowering to around 30&nbsp;billion dust molecules per second on 31 January 1974.<ref name="AHearnCowan1975">{{cite journal |last1=A'Hearn |first1=Michael F. |last2=Cowan |first2=J. J. |title=Molecular production rates in Comet Kohoutek |journal=The Astronomical Journal |date=October 1975 |volume=80 |pages=852 |doi=10.1086/111821 |bibcode=1975AJ.....80..852A |s2cid=121989799}}</ref> This transition was also underscored by an increase in the gas-to-dust ratio of Kohoutek by at least a factor of 2 after perihelion.<ref name="AHearn1975">{{cite journal |last1=A'Hearn |first1=Michael F. |title=Spectrophotometry of comet Kohoutek (1973f = 1973 XII) |journal=Astronomical Journal |date=October 1975 |volume=80 |issue=10 |pages=861–875 |doi=10.1086/111822 |bibcode=1975AJ.....80..861A |s2cid= 123614672|doi-access=free }}</ref> The change may have been enabled by the evaporation of ice-covered surfaces as Kohoutek drew closer to the Sun.<ref name="ODell1976" /> The ejection of [[meteoroids]] during Kohoutek's approach and passage of the Sun added about 1&nbsp;billion kg of mass to the [[zodiacal cloud]].<ref name="Fulle1988">{{cite journal |last1=Fulle |first1=M |title=Meteoroids from comet Kohoutek 1973 XII |journal=Astronomy and Astrophysics |date=July 1988 |volume=201 |issue=1 |pages=161–168 |bibcode=1988A&A...201..161F |s2cid=116263177}}</ref> Smaller [[micrometeoroid]]s were detected by the [[European Space Research Organisation#HEOS 1 and HEOS 2|HEOS 2]] satellite when it crossed the orbital plane of the outgoing comet around 9 June 1974, with the micrometeoroids being detected over the course of around 60&nbsp;days surrounding the plane traversal; these micrometeoroids had masses ranging between 10<sup>−13</sup>–10<sup>−11</sup>&nbsp;g.<ref name="Hoffmann et al. 2016">{{cite journal |last1=Hoffmann |first1=H.-J. |last2=Fechtig |first2=H |last3=Grün |first3=E |last4=Kissel |first4=J |title=Particles from Comet Kohoutek Detected by the Micrometeoroid Experiment on HEOS 2 |journal=International Astronomical Union Colloquium |date=1976 |volume=25 |issue=2 |pages=949–961 |doi=10.1017/S0252921100034357 |bibcode=1976NASSP.393..949H |s2cid=118057535|hdl=2060/19760014003 |hdl-access=free }}</ref><ref name="Grun et al. 1976">{{cite book |last1=Grün |first1=E. |last2=Kissel |first2=J. |last3=Hoffmann |first3=H. -J. |title=Interplanetary Dust and Zodiacal Light |chapter=Dust emission from Comet Kohoutek (1973f) at large distances from the sun |series=Lecture Notes in Physics |date=1976 |volume=48 |pages=334–338 |doi=10.1007/3-540-07615-8_503 |bibcode=1976LNP....48..334G|isbn=978-3-540-07615-5 |s2cid=118694750}}</ref>

[[File:Comet Kohoutek (S73-38731).jpg|thumb|Kohoutek as seen from Skylab in December 1973|left|alt=Gray scale photograph of Kohoutek, appearing as a bright, teardrop-shaped object at center with a faint tail]]
Later [[photometry (astronomy)|photometric analyses]] indicated that Kohoutek was a gassy comet with a high gas-to-dust ratio emblematic of comets entering the inner Solar System for the first time, suggesting a nucleus rich in [[Volatile (astrogeology)|volatiles]] and relatively depleted in [[refractory]] substances.<ref name="deAlmeida1996" /><ref name="RiekeLee1974">{{cite journal |last1=Rieke |first1=G. H. |last2=Lee |first2=T. A. |title=Photometry of Comet Kohoutek (1973f) |journal=Nature |date=April 1974 |volume=248 |issue=5451 |pages=737–740 |doi=10.1038/248737a0 |bibcode=1974Natur.248..737R |s2cid=4281170}}</ref> Analyses of Kohoutek's coma and tail in the near-ultraviolet found the roughly equal presence of [[hydrogen]] atoms and [[hydroxide]], suggesting that these chemical species [[photodissociation|were once constituents of water]]. At a distance of 1&nbsp;AU from the Sun, Kohoutek was losing roughly 1&nbsp;million tons (0.9&nbsp;million tonnes) of water per day.<ref name="Whipple1976" /> The mass of water lost between 60&nbsp;days before perihelion to 60&nbsp;days after perihelion, when Kohoutek would have been ejecting the most water, was approximately 64&nbsp;billion kg.<ref name="ODell1976">{{cite journal |last1=O'Dell |first1=C. R. |title=Physical processes in Comet Kohoutek |journal=Publications of the Astronomical Society of the Pacific |date=June 1976 |volume=88 |issue=523 |pages=342–348 |doi=10.1086/129954 |bibcode=1976PASP...88..342O |s2cid=120855634 |jstor=40675895|doi-access=free }}</ref> The mass loss due to the ejection of water after perihelion was roughly two times less than before perihelion. The surface of Kohoutek's nucleus was likely covered in a mix of particles and water ice stored in [[clathrate]]s. Much of this water was evaporated away as Kohoutek approached perihelion due to increased [[insolation]], leaving behind only subsurface ices and smaller pockets of water on the nuclear surface.<ref name="ODell1976" /> The uneven outgassing behavior of both water and other volatiles indicates that Kohoutek's nucleus likely has a heterogeneous composition and structure on scales of around {{cvt|10|m}}. Jets of vaporizing volatiles likely emanated from exposed areas where less volatile ices previously vaporized.<ref name="Huebner1975" /> Later analysis of spectrograms of Kohoutek provided strong evidence of the presence of the water [[cation]] ({{chem|H|2|O|+}}), particularly in the comet's tail.<ref name="HerzbergLew1974">{{cite journal |last1=Herzberg |first1=G |last2=Lew |first2=H |title=Tentative Identification of the {{chem|H|2|O|+}} Ion in Comet Kohoutek |journal=Astronomy and Astrophysics |date=February 1974 |volume=31 |pages=123–124 |doi=10.1017/S0252921100500864|bibcode=1974A&A....31..123H|s2cid=125675140|doi-access=free }}</ref><ref name="WehingerWyckoff1976">{{cite journal |last1=Wehinger |first1=Peter |last2=Wyckoff |first2=Susan |title=H<sub>2</sub>0<sup>+</sup> Ions in Comets: Comet Kohoutek (1973f) and Comet Bradfield (1974b) |journal=International Astronomical Union Colloquium |date=1976 |volume=25 |issue=Part1 |pages=199–205 |doi=10.1017/S0252921100500864|doi-access=free }}</ref> This chemical species was most likely the result of the [[photoionization]] of neutral water ({{chem|H|2|O}}) very near the nucleus.<ref name="MendisIp1974" /><ref name="Herbig1975">{{cite book |last1=Herbig |first1=George |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |chapter=Spectroscopy of the Coma and Tail|editor-last1=Gary|editor-first1=Gilmer|pages=233–235}}</ref>

[[Atomic oxygen]] and [[atomic carbon]] were also detected as the likely products of dissociating carbon monoxide or [[carbon dioxide]] from the nucleus.<ref name="Feldman et al. 1974">{{cite journal |last1=Feldman |first1=Paul D. |last2=Takacs |first2=Peter Z. |last3=Fastie |first3=William G. |last4=Donn |first4=Bertram |title=Rocket Ultraviolet Spectrophotometry of Comet Kohoutek (1973f) |journal=Science |date=23 August 1974 |volume=185 |issue=4152 |pages=705–707 |doi=10.1126/science.185.4152.705 |bibcode=1974Sci...185..705F|s2cid=43534328|jstor=1738738|pmid=17736378}}</ref> The nucleus also outgassed [[hydrogen]] at rates of up to approximately {{nowrap|4.5 × 10<sup>29</sup>}} atoms per second at speeds of around 7.8 ± 0.2&nbsp;km/s.<ref name="Opal et al. 1974" /><ref name="Huppler et al. 1975">{{cite journal |last1=Huppler |first1=D. |last2=Reynolds |first2=R. J. |last3=Roesler |first3=F. L. |last4=Scherb |first4=F. |last5=Trauger |first5=J. |title=Observations of comet Kohoutek /1973f/ with a ground-based Fabry-Perot spectrometer |journal=The Astrophysical Journal |date=November 1975 |volume=202 |pages=276–282 |doi=10.1086/153974 |bibcode=1975ApJ...202..276H |s2cid=120798083|doi-access=free }}</ref> Due to the low mass of hydrogen and the weak gravitational pull of Kohoutek, the cloud of hydrogen surrounding the comet was of great extent, extending over 30&nbsp;million km (19&nbsp;million mi) across;<ref name="Opal et al. 1974">{{cite journal |last1=Opal |first1=C. B. |last2=Carruthers |first2=G. R. |last3=Prinz |first3=D. K. |last4=Meier |first4=R. R. |title=Comet Kohoutek: Ultraviolet Images and Spectrograms |journal=Science |date=23 August 1974 |volume=185 |issue=4152 |pages=702–705 |doi=10.1126/science.185.4152.702 |bibcode=1974Sci...185..702O|s2cid=45497893|jstor=1738737|pmid=17736377}}</ref><ref name="Kumar et al. 1979" /> the hydrogen cloud was thus larger than the disk of the Sun.<ref name="Marsden1979">{{cite journal |last1=Marsden |first1=Brian G. |title=Comet Halley and history |journal=NASA Goddard Space Flight Center Space Missions to Comets |date=1979 |volume=2089 |pages=179–196 |bibcode=1979NASCP2089..179M}}</ref> Within the cloud, the ratio of [[deuterium]] to atomic hydrogen was at most 1&nbsp;percent.<ref name="Huppler et al. 1975" /> The atomic hydrogen was later understood to be the product of the photodissociation of water ice present in Kohoutek's nucleus.<ref name="Feldman1983">{{cite journal |last1=Feldman |first1=Paul D. |title=Ultraviolet Spectroscopy and the Composition of Cometary Ice |journal=Science |date=28 January 1983 |volume=219 |issue=4583 |pages=347–354 |doi=10.1126/science.219.4583.347 |bibcode=1983Sci...219..347F|s2cid=37048944|jstor=1689912|pmid=17815301 }}</ref> The nucleus may also have been once covered by a roughly meter-thick layer of highly volatile substances that quickly outgassed when Kohoutek first approached the inner Solar System.<ref name="Whipple1989" /> [[Cyanide]] was first observed within Kohoutek's [[coma (comet)|coma]] on 15 October 1973, while the comet was at a heliocentric distance of 1.8&nbsp;AU.<ref name="Biermann1973" /> The spectrographic signature of [[methyl cyanide]] at a wavelength of 2.7&nbsp;mm was also detected in the nucleus of Kohoutek.<ref name="UlichConklin1974">{{cite journal |last1=Ulich |first1=B. L. |last2=Conklin |first2=E. K. |title=Detection of methyl cyanide in Comet Kohoutek |journal=Nature |date=March 1974 |volume=248 |issue=5444 |pages=121–122 |doi=10.1038/248121a0 |bibcode=1974Natur.248..121U|s2cid=4287565}}</ref> Radio and [[Microwave astronomy|microwave]] observations of the comet identified [[hydrogen cyanide]], [[methylidyne radical]]s, and [[ethyl alcohol]] in addition to hydroxide and water.<ref name="Whipple1976" /><ref name="Huebner et al. 1974">{{cite journal |last1=Huebner |first1=W.F. |last2=Snyder |first2=L.E. |last3=Buhl |first3=D. |title=HCN radio emission from Comet Kohoutek (1973f) |journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=580–584 |doi=10.1016/0019-1035(74)90023-2 |bibcode=1974Icar...23..580H|s2cid=123086883}}</ref><ref name="Whipple1977">{{cite journal |last1=Whipple |first1=Fred L. |title=Comets: Data, problems, and objectives |journal=The Soviet-American Conference on Cosmochemistry of the Moon and Planets |date=1977 |volume=370 |pages=923–929 |url=https://ntrs.nasa.gov/api/citations/19780005045/downloads/19780005045.pdf |bibcode=1977NASSP.370..923W |access-date=10 July 2022 |archive-date=10 July 2022 |archive-url=https://web.archive.org/web/20220710191751/https://ntrs.nasa.gov/api/citations/19780005045/downloads/19780005045.pdf |url-status=live }}</ref> Other chemical species identified in the inner coma of Kohoutek included the [[amino radical]], [[diatomic carbon]], and [[sodium iodide]].<ref name="DelsemmeCombi1983">{{cite journal |last1=Delsemme |first1=A. H. |last2=Combi |first2=M. R. |title=Neutral cometary atmospheres. IV - Brightness profiles in the inner coma of comet Kohoutek 1973 XII |journal=The Astrophysical Journal |date=August 1983 |volume=271 |pages=388–397 |doi=10.1086/161204 |bibcode=1983ApJ...271..388D |s2cid=120962101|doi-access=free }}</ref><ref name="Goraya et al. 1986" /> Emission signatures of [[tricarbon]] and [[nitrogen gas]] were also detected.<ref name="Goraya et al. 1986" /><ref name="WyckoffWehinger1976">{{cite journal |last1=Wyckoff |first1=S. |last2=Wehinger |first2=P. A. |title=Molecular ions in comet tails |journal=The Astrophysical Journal |date=March 1976 |volume=204 |pages=604 |doi=10.1086/154209 |bibcode=1976ApJ...204..604W |s2cid=120955304}}</ref> Unlike in previously observed comets, the [[cyano radical]]s and diatomic carbon in Kohoutek's coma were not distributed spherically but instead elongated significantly away from the sun to distances of up to {{cvt|10000000|km}}.<ref name="Goraya et al. 1986">{{cite journal |last1=Goraya |first1=P. S. |last2=Rautela |first2=B. S. |last3=Sanwal |first3=B. B. |title=Absolute spectrophotometry of Comet kohoutek 1973f during post-perihelion passage |journal=Earth, Moon, and Planets |date=January 1986 |volume=34 |issue=1 |pages=77–91 |doi=10.1007/BF00054037 |bibcode=1986EM&P...34...77G |s2cid=120188816}}</ref>

{{clear}}

== Observational history ==
[[File:Comet Kohoutek from Kitt Peak 28 April 1973.jpg|thumb|Kohoutek as seen from the [[Kitt Peak National Observatory]] on 28 April 1973|alt=Two side-by-side videographs of Kohoutek, which appears as a faint blur]]
Following Luboš Kohoutek's discovery of his eponymous comet, additional photographic observations taken on 30&nbsp;March and 2&nbsp;April 1973 showed that the comet's coma was highly condensed and 20&nbsp;arcseconds in diameter. The comet was last observed by Kohoutek on 5&nbsp;May 1973 before it became too faint and unremarkable to observe or discern against the glare of [[twilight]].<ref name="Hendrie2000" /> At this stage, the comet's brightness was around magnitude 14.<ref name="CometOfTheWeek">{{cite web |last1=Hale |first1=Alan |title=Comet of the Week: Kohoutek 1973f |url=https://www.rocketstem.org/2020/12/27/ice-and-stone-comet-of-week-53/ |publisher=RocketSTEM |access-date=10 July 2022 |date=27 December 2020 |archive-date=10 July 2022 |archive-url=https://web.archive.org/web/20220710222241/https://www.rocketstem.org/2020/12/27/ice-and-stone-comet-of-week-53/ |url-status=live }}</ref> After several months of poor visibility, the comet was detected by Japanese astronomer [[Tsutomu Seki]] on 23&nbsp;September; the comet's apparent magnitude had brightened to magnitude&nbsp;11 but it remained a diffuse object.<ref name="Hendrie2000" /> By the time the comet was recovered, it had neared to a distance of 2.2&nbsp;AU away from the Sun.<ref name="Marsden1974" /> While the comet previously appeared as only a faint, featureless nebulosity, by late September a tail had become conspicuous, appearing first in a broad and fan-like form extending 2&nbsp;arcminutes to the north.<ref name="Marsden1974" /> The coma grew to about 1&nbsp;[[arcminute]] in diameter by mid-October&nbsp;1973 as the comet brightened. By the end of the month, both the nucleus and a lengthening tail had become  clearly apparent.<ref name="Bennett1973">{{cite journal |last1=Bennett |first1=J. C. |title=Visual observations of Comet Kohoutek 1973f |journal=Monthly Notes of the Astronomical Society of Southern Africa |date=December 1973 |volume=32 |issue=10, 11, 12 |pages=107–108 |doi=10.1038/246400a0|arxiv=|bibcode=1973MNSSA..32..107B|s2cid=42320124}}</ref>

In November&nbsp;1973, Kohoutek became bright enough to be visible to the naked eye.<ref name="Stoyan2015" /> The ion component of the comet's tail was first noted on 21&nbsp;November accompanying the brighter dust component.<ref name="Marsden1974" /> The comet brightened to an apparent magnitude of 2.8 by 22&nbsp;December 1973 before becoming indiscernible to ground-based observers due to Kohoutek's [[conjunction (astronomy)|conjunction]] with the Sun;<ref name="Stoyan2015" /> between 24 and 31&nbsp;December the comet was within 10° of the Sun.<ref name="Hendrie2000" /> During this period, the comet experienced a surge in brightness that{{snd}}although not clearly observable from the Earth's surface{{snd}}placed it in the echelon of [[great comet]]s.<ref name="Ferrin2014">{{cite journal |last1=Ferrín |first1=Ignacio |title=The location of Oort Cloud comets C/2011 L4 Panstarrs and C/2012 S1 ISON on a comet evolutionary diagram |journal=Monthly Notices of the Royal Astronomical Society |date=1 August 2014 |volume=442 |issue=2 |pages=1731–1754 |doi=10.1093/mnras/stu820 |bibcode=2014MNRAS.442.1731F|arxiv=1306.5010 |s2cid=54846398}}</ref> Kohoutek was at its brightest during this period, becoming a roughly –3rd magnitude object.<ref name="Hendrie2000" /> Kohoutek was a much brighter object in the infrared, reaching magnitudes of at least –4.75 and –5.70 at wavelengths of 10&nbsp;microns and 20&nbsp;microns, respectively.<ref name="Goraya et al. 1986" /> At its closest approach, the comet was visually separated by only around 0.75° from the center of the Sun.<ref name="Marsden1974" /> While the comet was too close to the Sun to be discernible from the ground, astronauts on Skylab and [[Soyuz 13]] were able to observe the comet during its perihelion.<ref name="CometOfTheWeek" /> The astronauts on Skylab noted that the comet was distinctly yellow and estimated that Kohoutek at its brightest was comparable to the magnitude –1.6 brightness of Jupiter.<ref name="Hendrie2000" /> An antitail emerged during Kohoutek's close passage, stretching as far as 5–7° from the comet towards the Sun.<ref name="Marsden1974" /> The separate gas and dust tails typically seen on comets were not observed from Skylab; instead, the comet uniformly took on a yellow texture, transitioning to white and later to a mottled violet appearance.<ref name="Gibson1974">{{cite journal |last1=Gibson |first1=Edward G. |title=Visual observations of Comet Kohoutek from Skylab III |journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=493–501 |doi=10.1016/0019-1035(74)90012-8 |bibcode=1974Icar...23..493G |s2cid=122741070}}</ref> The strikingly yellow color of the comet at perihelion was due to the scattering of sunlight by sodium released by the comet.<ref name="James1975" />

{{stack|
[[File:Edward Gibson illustration of Comet Kohoutek.jpg|thumb|upright=0.8|Illustration of Kohoutek on 29 December 1973 by Skylab 4's Edward Gibson|alt=A labeled sketch of the comet and an inverted color reproduction]]
[[File:Progressive Views Of Comet Kohoutek As Viewed By SL4 Astronauts.jpg|thumb|upright=0.8|Progressive views of Comet Kohoutek as viewed by SL4 astronauts]]
}}
{{Blockquote
|text=I just finished taking the 233 photos and Kohoutek is not looking like our old, pretty, graceful-looking, blue-white comet any more. It's getting so close to the Sun now that the tail is fanning out; it's very short. I think I can't see the rest of the tail just because it's so light. But what I can see behind the comet now, the—the [coma] is getting quite  large and bright, and the tail, all we can see is a fan behind it. And we're beginning to see some reds and some yellows in it.
|author=[[Gerald P. Carr]]
|title=speaking to NASA Mission Control Center on 25 December 1973
|source=Skylab Air-to-Ground Voice Transcription (Tape #MC1309/1)<ref name="SkylabTranscription">{{cite book |title=Skylab 1/4 Technical Air-to-Ground Voice Transcription |date=November 1973 |publisher=NASA |location=Houston, Texas}}</ref>
}}

Kohoutek once again became observable to ground-based observers beginning on 27&nbsp;December 1973. For ground observers, the comet was at most a 0th or 1st magnitude object.<ref name="Hendrie2000" /> By the time Kohoutek had reached a more favorable position for viewing by the general public, it had faded to around magnitude 2.<ref name="CometOfTheWeek" /> Although the comet was dimmer than anticipated, it was nonetheless among the ten brightest comets as seen from Earth between 1750 and 1994.<ref name="Kidger1994">{{cite journal |last1=Kidger |first1=Mark R. |title=The frequency of appearance of bright naked eye comets since 1750: Are bright comets less frequent in the 20th Century? |journal=Earth, Moon, and Planets |date=1994 |volume=66 |issue=2 |pages=231–238 |doi=10.1007/BF00644134 |bibcode=1994EM&P...66..231K |s2cid=119875072}}</ref> The comet rapidly dimmed following its perihelion on 28&nbsp;December, diminishing to magnitude –1.5 on 1 January 1974 and reaching magnitude 4 by 10 January 1974. By the end of January&nbsp;1974, Kohoutek was too faint to be seen with the unaided eye.<ref name="Stoyan2015" /> The comet dimmed to around 10th magnitude towards the end of March&nbsp;1974, after which it became too faint to clearly detect against the backdrop of the zodiacal light.<ref name="Hendrie2000" /> Unlike on the comet's inbound trek, its appearance on the outbound trek was much more diffuse and nebulous.<ref name="Marsden1978">{{cite journal |last1=Marsden |first1=Brian G. |last2=Roemer |first2=Elizabeth |title=Comets in 1974 |journal=Quarterly Journal of the Royal Astronomical Society |date=March 1978 |volume=19 |pages=38–58 |bibcode=1978QJRAS..19...38M}}</ref> When the comet returned to the same distance from the Sun at which it was discovered, it was over 100&nbsp;times fainter than at its first detection.<ref name="Whipple1989" /> The comet was last photographed in early November 1974 at a heliocentric distance of around 5&nbsp;AU with an apparent magnitude of 22.<ref name="CometOfTheWeek" /> At its greatest visual extent, Kohoutek's tail was well-defined and spanned 25° in length.<ref name="Stoyan2015" /> In January&nbsp;1974 its tail featured both a helical structure and a more irregular cloud-like structure about 0.1&nbsp;AU away from the nucleus.<ref name="Hyder et al. 1974">{{cite journal |last1=Hyder |first1=Charles L. |last2=Brandt |first2=John C. |last3=Roosen |first3=Robert G. |title=Tail structure far from the head of Comet Kohoutek|journal=Icarus |date=December 1974 |volume=23 |issue=4 |pages=601–610 |doi=10.1016/0019-1035(74)90028-1 |bibcode=1974Icar...23..601H |s2cid=119997643}}</ref>  Kohoutek's antitail spanned as much as 3° for ground observers;<ref name="Stoyan2015" /> the antitail became more diffuse and dim following perihelion, making its visibility less favorable.<ref name="James1975">{{cite journal |last1=James |first1=J. F. |title=What came out of Kohoutek's comet? |journal=Nature |date=April 1975 |volume=254 |issue=5499 |pages=382–383 |doi=10.1038/254382b0 |bibcode=1975Natur.254..382J |s2cid=4163458}}</ref> A faint [[meteor shower]] seen on 1–3&nbsp;March 1974, concurrent with Earth's closest pass of Kohoutek's orbit, may have been directly associated with Kohoutek.<ref name="Terenteva1976">{{cite journal |last1=Terenteva |first1=A. K. |last2=Kruchinenko |first2=V. G. |last3=Triashin |first3=S. S. |title=Observations of meteors connected with comet Kohoutek, 1973f |journal=Astronomicheskii Vestnik |date=July 1976 |volume=10 |issue=1 |pages=70–71 |bibcode=1976AVest..10...70T}}</ref>

== Brightness predictions ==
[[File:Comet Kohoutek light curve.svg|thumb|upright=1.4|The light curve of Kohoutek plotted from ground-based observations, with the perihelion denoted by the red line. While initial predictions assumed the comet's luminosity would scale to the 4th or even 6th power of its heliocentric distance, its brightness on approach scaled more closely with the second power.|alt=Scatterplot of brightness observations of the comet, showing the brightening and subsequent dimming of the comet as it swung around the Sun]]
Kohoutek's anticipated close passage of the Sun and its pristine condition{{snd}}having likely never approached the Sun previously{{snd}}made the comet a candidate for becoming one of the brightest comets of the 20th century. Conventional wisdom held that the brightness of a comet was [[power law|scaled]] according to the inverse [[fourth power]] of its distance from the Sun, and it was customary at the time to use this assumption in predicting the peak brightnesses of newly discovered comets.<ref name="Green et al. 2001" /> The value of the power (denoted {{math|''n''}}) would be repeatedly changed in subsequent estimates from the conventional value of 4, with estimates generally using values of {{math|''n''}} between 3–6.<ref name="Eberhart1974" /> Kohoutek's distance at the time of its discovery meant that its intrinsic brightness could increase by more than a million-fold using these assumptions.<ref name="Whipple1976" /> While a more accurate estimate for the comet's ultimate apparent brightness{{snd}}around magnitude –2.3{{snd}}could be derived from early observations,<ref name="Kohoutek1974" /> some of the first extrapolations of the comet's brightness using the initial photographic observations predicted apparent magnitudes as bright as magnitude –10 near perihelion; such a remarkably bright comet would be visible in daylight. Estimates later reached as bright as magnitude –12, comparable to the brightness of the [[full Moon]]. The high peak luminosity also implied ample visibility: early projections showed Kohoutek reaching naked-eye visibility in early November and then becoming as bright as Jupiter by mid-December, with increasing brilliance in January&nbsp;1974 following its perihelion. Kohoutek was billed by the press as the "Comet of the Century" when these estimates were publicized.<ref name="Hendrie2000" /><ref name="ChristmasCometYielding">{{cite journal |title=The Christmas Comet Begins Yielding Data |journal=Science News |date=27 October 1973 |volume=104 |issue=17 |page=262 |doi=10.2307/3958219 |bibcode=|jstor=3958219}}</ref><ref name="Murdin2000">{{cite book |editor1-last=Murdin |editor1-first=Paul |title=Encyclopedia of Astronomy & Astrophysics. |date=November 2000 |publisher=CRC Press |location=Boca Raton, Florida |isbn=9781000523034 |page=771 |edition=First |chapter=Computer Kohoutek (C/1973 E1)|doi=10.1888/0333750888/5239 |bibcode=2000eaa..bookE5239.}}</ref><ref name="Rao2020">{{cite web |last1=Rao |first1=Joe |title=How the 'comet of the century' became an astronomical disappointment |url=https://www.space.com/comet-kohoutek-flop-of-the-century.html |publisher=Space.com |date=22 January 2020 |access-date=9 July 2022 |archive-date=8 April 2022 |archive-url=https://web.archive.org/web/20220408051049/https://www.space.com/comet-kohoutek-flop-of-the-century.html |url-status=live }}</ref> [[Fred Lawrence Whipple]] also remarked that the comet could "well be the comet of the century."<ref name="Time" />{{rp|1}} Brian Marsden stated that "an object [as large as Comet Kohoutek] should achieve unusual brightness and produce an exceptional tail" with twelve weeks of naked-eye visibility, but also cautioned that "some very promising comets of the past [have] fizzled out."<ref name="HugeComet" /><ref name="BrilliantHope">{{cite news |title=New comet holds brilliant hope for star-gazers |url=https://www.newspapers.com/clip/105283367/ |via=Newspapers.com |access-date=9 July 2022 |work=The Morning News |agency=United Press International |issue=83 |volume=183 |date=6 April 1973 |page=10 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013926/https://www.newspapers.com/clip/105283367/the-morning-news/ |url-status=live }} {{free access}}</ref> The [[Associated Press]] reported in early April&nbsp;1973 that astronomers believed that the comet's approach "could be the most spectacular astrophysical event of the [20th] century".<ref name="HugeComet">{{cite news |title=Huge comet at Christmas to be visible |url=https://www.newspapers.com/clip/105097063/ |via=Newspapers.com |access-date=6 July 2022 |work=The Montreal Star |issue=81 |date=5 April 1973 |location=Montreal, Quebec |page=13 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013926/https://www.newspapers.com/clip/105097063/the-montreal-star/ |url-status=live }} {{free access}}</ref>

[[File:Skylab brightness observations of Comet Kohoutek.png|thumb|left|Kohoutek's brightness (observations plotted as points) fell short of predictions based on the light curves of past comets like [[Comet Arend–Roland|Arend–Roland]] and [[Comet Bennett|Bennett]] (the solid and dashed lines, respectively).|alt=Graph plotting both Kohoutek's brightness and predictions based on prior comets]]
Although the most bullish predictions caught the attention of the press and the general public, some astronomers{{snd}}like S. W. Milbourn and Whipple{{snd}}were more uncertain and held that such predictions were optimistic.<ref name="Hendrie2000" /><ref name="Whipple1976" /> Regardless of its luminosity, the comet would be too close to the sun to be seen by ground observers at its brightest.<ref name="Eberhart1974">{{cite journal |last1=Eberhart |first1=Jonathan |title=Eyes on the Comet |journal=Science News |date=4 May 1974 |volume=105 |issue=18 |pages=290–291 |doi=10.2307/3958991 |bibcode=|s2cid=87707864|jstor=3958991}}</ref> [[British Astronomical Association]] (BAA) circular 548, published on 25&nbsp;July 1973, provided an alternative prediction of magnitude –3 for Kohoutek's peak brightness.<ref name="Hendrie2000" /> Higher-end projections of Kohoutek's peak brightness remained as high as magnitude –10 into August&nbsp;1973. An article in ''[[Nature (journal)|Nature]]'' published in the final week of September&nbsp;1973 suggested that Kohoutek's peak brightness could have a greater than 50&nbsp;percent chance of being within two magnitudes of –4.<ref name="Lyttleton1973" /> The National Newsletter accompanying the ''[[Journal of the Royal Astronomical Society of Canada]]'' in October&nbsp;1973 estimated that Kohoutek would remain visible to the naked eye for four months bracketing perihelion.<ref name="Avery1973">{{cite journal |last1=Avery  |first1=Lorne |title=Orbital Data for Comet Kohoutek (1973f)  |journal=Journal of the Royal Astronomical Society of Canada Newsletter |date=October 1973 |volume=67 |pages=L25–L26 |doi=|arxiv=|bibcode=1973JRASC..67L..25A|s2cid=}}</ref> Brightness predictions were revised downward following the comet's behavior as perihelion approached.<ref name="BensonCompton1981" /> On 11&nbsp;October 1973, BAA circular 549 provided a revised estimate of magnitude –4 for Kohoutek's brightest apparent magnitude. While still bright, such a brightness would yield only around ten days of clear naked-eye visibility for observers in the Northern Hemisphere.<ref name="Hendrie2000" /> Publicized predictions of the comet were scaled back in November&nbsp;1973.<ref name="TonedDown">{{cite news |title=Kohoutek Predictions Toned Down |url=https://www.newspapers.com/clip/60728883/ |via=Newspapers.com |access-date=10 July 2022 |work=Sentinel Star |agency=Associated Press |issue=315 |date=11 November 1973 |page=22C |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013926/https://www.newspapers.com/clip/60728883/the-orlando-sentinel/ |url-status=live }} {{Free access}}</ref> Although Kohoutek brightened by a factor of nearly a million by perehelion, sufficiently "to be a fine object for experienced observers when seen under ideal conditions in clear skies away from city lights" according to Whipple, its peak magnitude of –3 fell short of the most publicized projections and proved mediocre to the public eye;<ref name="Whipple1976" /><ref name="Whipple1989">{{cite journal |last1=Whipple |first1=F. L. |title=Comets in the space age |journal=The Astrophysical Journal |date=June 1989 |volume=341 |pages=1–13 |doi=10.1086/167466 |bibcode=1989ApJ...341....1W |s2cid=121228906}}</ref> however, the comet's ultimate brightness was close to the published lower-end predictions.<ref name="Hendrie2000" /> Whipple later quipped that "if you want to have a safe gamble, bet on a horse{{snd}}not a comet."<ref name="ConfirmSnowballs">{{cite news |last1=Sullivan |first1=Walter |title=Observations of Kohoutek Appear to Confirm Concept of Comets as 'snowballs' |url=https://www.nytimes.com/1974/01/17/archives/observations-of-kohoutek-appear-to-confirm-concept-of-comets-as.html |access-date=15 July 2022 |work=The New York Times |date=17 January 1974 |location=New York |page=24 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715043242/https://www.nytimes.com/1974/01/17/archives/observations-of-kohoutek-appear-to-confirm-concept-of-comets-as.html |url-status=live }}</ref>

Despite higher assumed values of {{math|''n''}}, the [[light curve]] of Kohoutek from 24 November 1973 to perihelion best fit {{math|''n'' {{=}} 2.2}} while its light curve after perihelion to 16 January 1974 best fit {{math|''n'' {{=}} 3.3}} or {{math|''n'' {{=}} 3.8}}.<ref name="Angione et al. 1975">{{cite journal |last1=Angione |first1=Ronald J. |last2=Gates |first2=Bill |last3=Henize |first3=Karl G. |last4=Roosen |first4=Robert G. |title=The light curve of comet Kohoutek |journal=Icarus |date=January 1975 |volume=24 |issue=1 |pages=111–115 |doi=10.1016/0019-1035(75)90164-5 |bibcode=1975Icar...24..111A |s2cid=119799157}}</ref> The more optimistic use of {{math|''n'' {{=}} 6}} led to overestimates of Kohoutek's perihelion brightness by as much as a factor of 2800.<ref name="Opik1977">{{cite journal |last1=Öpik |first1=E. J. |title=On Predicting the Brightness of Comets |journal=Irish Astronomical Journal |date=September 1977 |volume=13 |issue=3/4 |pages=92–94 |bibcode=1977IrAJ...13...92O}}</ref> The early brightness of Kohoutek around the time of its discovery may have been influenced by the intense [[outgassing]] of highly volatile substances; such volatiles may have been abundant in the nucleus if Kohoutek had never previously entered the inner Solar System.<ref name="Murdin2000" /><ref name="Sekanina1976">{{cite journal |last1=Sekanina |first1=Zdenek |title=A Continuing Controversy: Has the Cometary Nucleus been Resolved? |journal=International Astronomical Union Colloquium |date=1976 |volume=25 |issue=2 |pages=537–587 |doi=10.1017/S0252921100034084|hdl=2060/19760013988 |hdl-access=free }}</ref> The degree of outgassing may have been enhanced by extremely porous outer layers of the nucleus that readily allowed the most volatile ices to vaporize at great distances from the Sun.<ref name="Whipple1975">{{cite book |last1=Whipple |first1=Fred L. |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |chapter=Implications for Models and Origin of the Nucleus|editor-last1=Gary|editor-first1=Gilmer|pages=227–232}}</ref> In this model, the comet would have brightened quickly in the early stages of its solar approach, at about {{math|''n'' {{=}} 5.78}}, before brightening more in line with shorter period comets.<ref name="Ferrin2014" /><ref name="Whipple1989" /> The early burst would have led to inflated expectations for the comet's ultimate brightness.<ref name="Rao2020" /> A separate study of long-period comets published in 1995 found that comets with initial semi-major axes greater than 10,000&nbsp;AU brighten more slowly and less substantially before perihelion than shorter period comets.<ref name="Green et al. 2001" /> Such comets are discovered at farther distances from the Sun than other comets as a result.<ref name="Whipple1985">{{cite book |last1=Whipple |first1=Fred L. |title=ICES in the Solar System |editor1-last=Klinger |editor1-first=Jürgen |editor2-last=Benest |editor2-first=Daniel |editor3-last=Dollfus |editor3-first=Audouin |editor4-last=Smoluchowski |editor4-first=Roman |date=1985 |series=Mathematical and Physical Sciences, Volume 156 |publisher=D. Reidel Publishing Company |isbn=9789401088916 |doi=10.1007/978-94-009-5418-2_23 |pages=343–366 |chapter=Present Status of the Icy Conglomerate Model}}</ref> It is now understood that Kohoutek's light curve preceding its 1973&nbsp;perihelion was typical for comets with similar orbits.<ref name="Green et al. 2001" />

== Observing campaigns and scientific results ==
[[File:Artist's concept of Skylab 4 astronauts observing Comet Kohoutek (S73-37274).jpg|thumb|Artist's concept of Skylab 4 astronauts observing Comet Kohoutek via the space station's airlock|alt=Illustration showing Kohoutek as seen from Skylab above the Earth's atmosphere]]
Kohoutek was the subject of intense scientific investigation and was observed over an unprecedentedly large range of the [[electromagnetic spectrum]].<ref name="Biermann1973" /> Kohoutek represented the first time [[radio astronomy]] techniques were used to study a comet.<ref name="Whipple1976" /> The possibility that the comet could be entering the inner Solar System for the first time since its formation{{snd}}making it potentially illustrative of the evolution of comets and conditions in the early Solar System{{snd}}made it an attractive scientific target.<ref name="MSFC" />{{rp|12}} The comet's exceptionally early detection, as well as the concurrence of its perihelion with [[Skylab 4]], allowed for and motivated the coordination of Operation Kohoutek, a cometary observing campaign backed by [[NASA]] and involving a wide array of instruments and observation platforms. The resulting study of Kohoutek was in its time the most comprehensive and detailed of any comet; the scale of the international effort to observe the comet would not be surpassed until the 1986 [[International Halley Watch]] for [[Halley's Comet]].<ref name="Dubin1975" /><ref name="Murdin2000" />

{{multiple image
 | align = left
 | direction = vertical
 | width = 225
 | image1 = Skylab SL 4 crew.jpg
 | alt1 = Grayscale television picture of the three members of Skylab 4
 | caption1 = The crew of Skylab 4 discussing their observations of the comet via television on 28 December 1973
 | image2 = Skylab3-Patch.png
 | alt2 = Emblem of Skylab 4, featuring the crew's names and symbols of the mission's scientific objectives
 | caption2 = Skylab 4 emblem
}}
Of particular interest were the molecular makeup of the comet and the dust in its tail.<ref name="James1975" /> Many of the observations focused on the possible detection of water, which until Kohoutek had been never detected in a comet.<ref name="Dubin1975" /><ref name="Ip and Mendis 1973">{{cite journal |last1=Ip |first1=W.-H. |last2=Mendis |first2=D. A. |title=Development of an {{chem|H|2|O}} Atmosphere around Comet Kohoutek (1973f) and its Possible Detection |journal=Nature |date=September 1973 |volume=245 |issue=5422 |pages=197–199 |doi=10.1038/245197a0|arxiv=|bibcode=1973Natur.245..197I|s2cid=4245004}}</ref>{{efn|Observations identified the cation of water ({{chem|H|2|O|+}}) in Kohoutek. It would not be until Comet Bradfield (1974 III) that neutral water ({{chem|H|2|O}}) was detected in a comet.<ref name="Whipple1976b" />|name=H2O}} While the presence of water in comets could be inferred by the identification of hydroxide and hydrogen constituents in previous comets, the prominent spectral signature of water in Kohoutek's tail was the first conclusive evidence that comets contained water.<ref name="Wehinger et al. 1974">{{cite journal |last1=Wehinger |first1=P. A. |last2=Wyckoff |first2=S. |last3=Herbig |first3=G. H. |last4=Herzberg |first4=G. |last5=Lew |first5=H. |title=Identification of {{chem|H|2|O|+}} in the Tail of Comet Kohoutek (1973f). |journal=The Astrophysical Journal |date=May 1974 |volume=190 |pages=L43 |doi=10.1086/181500 |bibcode=1974ApJ...190L..43W |s2cid=121346176|doi-access=free }}</ref> Observations also aimed to detect complex molecules in the comet; before Kohoutek, no molecule with more than three atoms had ever been detected in a comet.<ref name="Metz1973">{{cite journal |last1=Metz |first1=William D. |title=Kohoutek, the Christmas Comet: Skylab Mission Expanded? |journal=Science |date=27 July 1973 |volume=181 |issue=4097 |pages=333–334 |doi=10.1126/science.181.4097.333 |bibcode=1973Sci...181..333M|s2cid=31602518|jstor=1736609|pmid=17832027}}</ref> The detection of methyl cyanide in Kohoutek's nucleus was the first time such a molecule had been observed in a comet. It was also the first direct evidence of the hypothesis that comet nuclei harbored complex and stable chemical compounds (also known as "parent molecules") that sublimated or dissociated into the chemically unstable [[Radical (chemistry)|radicals]] and simpler molecules often identified in cometary spectra.<ref name="UlichConklin1974" /><ref name="MendisIp1974">{{cite journal |last1=Mendis |first1=D. A. |last2=Ip |first2=W-H. |title=Behaviour of Comet Kohoutek (1973f) |journal=Nature |date=June 1974 |volume=249 |issue=5457 |pages=536–537 |doi=10.1038/249536a0 |bibcode=1974Natur.249..536M |s2cid=4297924}}</ref> Kohoutek also marked the first time that hydrogen cyanide was identified in a comet,<ref name="Whipple1976b" /> supporting the hypothesis that hydrogen cyanide could be a parent molecule of the cyano radical previously detected in comets.<ref name="Krankowsky1991">{{cite book|publisher=Cambridge University Press |last1=Krankowsky |first1=Dieter |title=The Composition of Comets |chapter=Section V: The Cometary Coma |journal=International Astronomical Union Colloquium |date=1991 |volume=116 |issue=2 |pages=854–877 |doi=10.1017/S0252921100012744 |bibcode=1991ASSL..167..855K}}</ref> The signature of silicon in infrared spectra of Kohoutek offered the first direct evidence of silicon in comets.<ref name="Hendrie2000" /> The identification of a hydrogen cloud surrounding Kohoutek and its [[Lyman-alpha line]] signature validated earlier predictions that comets amass hydrogen. The low abundance of [[methane]] in Kohoutek and what Whipple described as "chemically ill-mated carbon molecules" suggested that comets were formed from the aggregation of compounds at low temperatures as opposed to the cooling of hot gasses, possibly pointing to a larger role of the [[interstellar medium]] in providing the constituents of cometary compositions.<ref name="Whipple1976b">{{cite journal |last1=Whipple |first1=Fred L. |title=Background of modern comet theory |journal=Nature |date=September 1976 |volume=263 |issue=5572 |pages=15–19 |doi=10.1038/263015a0 |bibcode=1976Natur.263...15W|s2cid=40079180}}</ref> [[Acetone]], [[ammonia]], and [[helium]] were not detected in Kohoutek despite searches.<ref name="Whipple1977" />

[[File:Mariner 10.jpg|thumb|In observing Kohoutek, Mariner 10 became the first interplanetary spacecraft to observe a comet.|alt=Photograph of a model of the Mariner 10 spacecraft]]

Skylab, the [[Orbiting Astronomical Observatory]], the [[Orbiting Solar Observatory]], ground observatories, and various [[sounding rockets]] were among the many observing platforms used to investigate Kohoutek during the comet's approach.<ref name="Metz1973" /> Some resources in other projects under the auspices of NASA were redirected to study the comet. The newly built Joint Observatory for Cometary Research near Socorro, New Mexico, was made operational in time to observe the comet.<ref name="BensonCompton1981" /><ref name="Brandt1981">{{cite report |last1=Brandt |first1=John C. |title=The JOCR Program |url=https://ntrs.nasa.gov/api/citations/19820006140/downloads/19820006140.pdf |publisher=NASA |access-date=15 July 2022 |pages=171–184 |date=1 October 1981 |work=JPL Mod. Observational Tech. for Comets |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715043242/https://ntrs.nasa.gov/api/citations/19820006140/downloads/19820006140.pdf |url-status=live }}</ref> In June&nbsp;1973, NASA also briefly considered launching a spacecraft to intercept and investigate the comet via either a [[Thor-Delta]] or [[Atlas-Centaur]] launch vehicle but scrapped the proposal due to insufficient preparation time.<ref name="AstronauticsAeronautics1973">{{cite book |title=Astronautics and Aeronautics, 1973: Chronology of Science, Technology, and Policy |date=1975 |publisher=NASA |location=Washington, D.C. |page=191 |url=https://books.google.com/books?id=5PwwnVheLEwC |access-date=14 July 2022 |chapter=June |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233604/https://books.google.com/books?id=5PwwnVheLEwC |url-status=live }}</ref><ref name="CloseStudyWeighed">{{cite news |last1=Sullivan |first1=Walter |title=Plan to 'Intercept' Comet For Close Study Weighed |url=https://www.nytimes.com/1973/06/16/archives/plan-to-intercept-comet-for-close-study-weighed-a-spare-mariner.html |access-date=14 July 2022 |work=The New York Times |date=16 June 1973 |location=New York |page=56 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233607/https://www.nytimes.com/1973/06/16/archives/plan-to-intercept-comet-for-close-study-weighed-a-spare-mariner.html |url-status=live }}</ref> [[Skylab 4]]{{snd}}the third crewed mission to the Skylab space station{{snd}}was scheduled favorably for the passage and perihelion of Kohoutek.<ref name="Metz1973" /> As a result, a substantial observation program targeting Kohoutek was appended to the original Skylab 4 mission, with the launch date selected due to scientific interest in the comet.<ref name="Skylab3Study">{{cite news |title=Skylab 3 to study a brilliant comet |url=https://www.nytimes.com/1973/08/17/archives/skylab-3-to-study-a-brilliant-comet.html |access-date=14 July 2022 |work=The New York Times |agency=Associated Press |date=17 August 1973 |page=18 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233608/https://www.nytimes.com/1973/08/17/archives/skylab-3-to-study-a-brilliant-comet.html |url-status=live }}</ref><ref name="MSFC" />{{rp|12}} The observation of the comet from Skylab was primarily conducted using instruments already on the space station, along with the backup of the [[Far Ultraviolet Camera/Spectrograph]] from [[Apollo 16]]. Due to Skylab's orbit around Earth, the comet could only be observed for at most 26&nbsp;minutes at a time. When Kohoutek appeared closest to the Sun on 27 December 1973, Skylab instruments were trained on the comet almost continuously for 21&nbsp;consecutive orbits.<ref name="Lundquist1979">{{cite book |editor1-last=Lundquist |editor1-first=Charles A. |title=Skylab's Astronomy and Space Sciences |publisher=NASA |location=Washington, D.C. |url=https://history.nasa.gov/SP-404/ch4.htm |access-date=9 July 2022 |chapter=4. Observations of Comet Kohoutek |archive-date=13 November 2004 |archive-url=https://web.archive.org/web/20041113100704/https://history.nasa.gov/SP-404/ch4.htm |url-status=live }}</ref> [[Mariner 10]], en route to [[Venus]], also made ultraviolet measurements of Kohoutek at a distance of around 0.7&nbsp;AU in January&nbsp;1974,<ref name="Kumar et al. 1979">{{cite journal |last1=Kumar |first1=S. |last2=Holberg |first2=J. |last3=Broadfoot |first3=A. L. |last4=Belton |first4=M. J. S. |title=The Lyman-alpha observations of comet Kohoutek from Mariner 10 |journal=The Astrophysical Journal |date=September 1979 |volume=232 |pages=616 |doi=10.1086/157320 |bibcode=1979ApJ...232..616K |s2cid=120955159}}</ref><ref name="Mariner10FliesBy">{{cite web |editor-last1=Mars |editor-first1=Kelli |title=45 Years Ago: Mariner 10 flies by Venus |url=https://www.nasa.gov/feature/45-years-ago-mariner-10-flies-by-venus |website=NASA History |publisher=NASA |access-date=8 July 2022 |date=5 February 2019 |archive-date=10 July 2022 |archive-url=https://web.archive.org/web/20220710213607/https://www.nasa.gov/feature/45-years-ago-mariner-10-flies-by-venus/ |url-status=live }}</ref> making the comet the first to be observed by an interplanetary spacecraft.<ref name="CometOfTheWeek" /> Although the comet's unexpected faintness prevented clear television images from being obtained by the spacecraft, Mariner 10's ultraviolet spectrometer nonetheless collected useful data concerning Kohoutek's hydrogen coma.<ref name="DunneBurgess1978">{{cite book |last1=Dunne |first1=James A. |last2=Burgess |first2=Eric |title=The Voyage of Mariner 10 |publisher=NASA |location=Washington, D.C. |url=https://history.nasa.gov/SP-424/ch5.htm |access-date=14 July 2022 |chapter=5. Venus Bound - Success and Near Failure |year=1978 |archive-date=24 January 2021 |archive-url=https://web.archive.org/web/20210124091059/https://history.nasa.gov/SP-424/ch5.htm |url-status=live }}</ref> [[Pioneer 6, 7, 8, and 9#Pioneer 6|Pioneer 6]] and [[Pioneer 6, 7, 8, and 9#Pioneer 9|Pioneer 8]] recorded data from within the comet's tail in 1974.<ref name="Pioneer6">{{cite web |title=Pioneer 06 |url=https://solarsystem.nasa.gov/missions/pioneer-06/in-depth/ |website=Solar System Exploration |publisher=NASA |access-date=14 July 2022 |date=11 August 2019 |archive-date=12 July 2022 |archive-url=https://web.archive.org/web/20220712074504/https://solarsystem.nasa.gov/missions/pioneer-06/in-depth/ |url-status=live }}</ref>

The results of the observations conducted as part of Operation Kohoutek were presented in June&nbsp;1974 at a workshop held at the [[Marshall Space Flight Center]].<ref name="Roemer1976b">{{cite journal |last1=Roemer |first1=E. |title=Operation Kohoutek |journal=Science |date=18 June 1976 |volume=192 |issue=4245 |pages=1227 |doi=10.1126/science.192.4245.1227 |bibcode=1976Sci...192.1227R|s2cid=34080360|jstor=1742598|pmid=17771755 }}</ref> Comet science saw considerable advances as a result of the observational research conducted on Kohoutek,<ref name="Murdin2000" /> ushering in what Fred Whipple termed a {{"'}}renaissance' of cometary research".<ref name="Whipple1989" /> At the time, most scientists accepted Whipple's hypothesis that cometary nuclei were "[[Comet#Scientific approach|dirty snowballs]]" made mostly of ices. However, there were other alternative models for comet nuclei, such as the "sand bank" model championed by British astronomer [[Raymond Lyttleton|Raymond A. Lyttleton]] which considered nuclei as loose collections of dust particles with negligible amounts of ice.<ref name="RevisedTheory">{{cite news |last1=Sullivan |first1=Walter |title=Revised Theory on Comets Offered |url=https://www.nytimes.com/1973/12/24/archives/revised-theory-on-comets-offered-predominant-view.html |work=The New York Times |date=24 December 1973 |location=New York |page=30 |access-date=8 July 2022 |archive-date=8 July 2022 |archive-url=https://web.archive.org/web/20220708234337/https://www.nytimes.com/1973/12/24/archives/revised-theory-on-comets-offered-predominant-view.html |url-status=live }}</ref><ref name="Time">{{cite magazine |title=SPECIAL REPORT: Kohoutek: Comet of the Century |url=https://content.time.com/time/subscriber/article/0,33009,908347-1,00.html |access-date=8 July 2022 |magazine=Time |issue=25 |volume=102 |date=17 December 1973 |archive-date=8 July 2022 |archive-url=https://web.archive.org/web/20220708234200/https://content.time.com/time/subscriber/article/0,33009,908347-1,00.html |url-status=live }}</ref>{{rp|5}} The detection and identification of various gasses emanating from Kohoutek validated the predictions of Whipple's model.<ref name="Wehinger et al. 1974" /><ref name="SAJSReportsBrief">{{cite journal |title=Reports in Brief |journal=South African Journal of Science |date=December 1975 |volume=71 |url=https://journals.co.za/doi/pdf/10.10520/AJA00382353_4963 |access-date=8 July 2022 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013927/https://journals.co.za/doi/pdf/10.10520/AJA00382353_4963 |url-status=live }}</ref><ref name="Brim1977">{{cite tech report |last1=Brim |first1=Nancy L. |title=Astronautics and Aeronautics, 1974 |date=1977 |series=NASA History Series |publisher=NASA |bibcode=1977NASSP4019.....B |id=NASA SP-4019}}</ref> Kohoutek's behavior led to the development of more detailed models seeking to explain the physical structure of comet nuclei.<ref name="Huebner1975">{{cite book |last1=Huebner |first1=W. F. |title=Comet Kohoutek: A Workshop Held at Marshall Space Flight Center |date=1975 |publisher=NASA |location=Washington, D.C. |chapter=On the structure of the nucleus of comet Kohoutek (1973f)|journal=NASA Special Publication |volume=355 |editor-last1=Gary|editor-first1=Gilmer|bibcode=1975NASSP.355...15B|pages=145–152}}</ref> One proposal suggested that Kohoutek belonged to a subset of comets containing a [[Comet nucleus#"Icy dirtball"|non-volatile dust mantle around an icy volatile core]].<ref name="MendisBrin1977">{{cite journal |last1=Mendis |first1=D. A. |last2=Brin |first2=G. D. |title=Monochromatic brightness variations of comets: II.Core-Mantle Model |journal=The Moon |date=December 1977 |volume=17 |issue=4 |pages=359–372 |doi=10.1007/BF00562645 |bibcode=1977Moon...17..359M |s2cid=119797846}}</ref> The [[occultation]] of the [[astronomical radio source|radio]] source [[Parkes Catalogue of Radio Sources|PKS]] 2025–15 by Kohoutek's tail on 5 January 1974 also served as an opportunity to study [[interplanetary scintillation]].<ref name="Iju et al. 2015">{{cite journal |last1=Iju |first1=Tomoya |last2=Abe |first2=Shinsuke |last3=Tokumaru |first3=Munetoshi |last4=Fujiki |first4=Ken’ichi |title=Plasma distribution of Comet ISON (C/2012 S1) observed using the radio scintillation method |journal=Icarus |date=May 2015 |volume=252 |pages=301–310 |doi=10.1016/j.icarus.2015.02.007 |bibcode=2015Icar..252..301I |arxiv=1410.2119 |s2cid=118607736}}</ref><ref name="Lee1976">{{cite journal |last1=Lee |first1=L. C. |title=Plasma irregularities in the comet's tail |journal=The Astrophysical Journal |date=November 1976 |volume=210 |pages=254–257 |doi=10.1086/154825 |bibcode=1976ApJ...210..254L |hdl=2060/19760012963 |s2cid=120556703|hdl-access=free }}</ref>

== Media coverage and viewing events ==
[[File:Lubos Kohoutek briefing news media.jpg|thumb|Luboš Kohoutek briefing the press on expectations for the comet on 5 January 1974|alt=Photograph of Kohoutek seated behind several microphones]]
{{Blockquote
|text=A hundred years from now, how will our great, great grandchildren remember 1973?<br /> In a future age, when the names of [[Richard Nixon|Nixon]] and [[Leonid Brezhnev|Brezhnev]] are dimly remembered, and those of [[Sam Ervin|Ervin]] and [[John N. Mitchell|Mitchell]] and [[John Dean|Dean]] are minor footnotes in scholarly treatises, the name and the discovery that will illuminate the 1973 will be Lubos Kohoutek.
|author=[[William Safire]]
|title="Kohoutek's Comet"
|source=''The New York Times'' (30 July 1973)<ref name="Safire1973">{{cite news |last1=Safire |first1=William |title=Kohoutek's Comet |url=https://www.nytimes.com/1973/07/30/archives/kohouteks-comet-essay.html |access-date=7 July 2022 |work=The New York Times |date=30 July 1973 |location=New York |page=27 |archive-date=7 July 2022 |archive-url=https://web.archive.org/web/20220707035148/https://www.nytimes.com/1973/07/30/archives/kohouteks-comet-essay.html |url-status=live }}</ref>
}}

Kohoutek was in its time the most publicized comet aside from Halley's Comet.<ref name="Marsden1974" /> The media attention was brought about by a combination of factors, including the early predictions of its brightness, its passage concurrent with the [[Christmas and holiday season]], the involvement of many observatories and powerful telescopes, and the possible effort of a manned spaceflight mission{{snd}}Skylab 4{{snd}} to investigate the comet.<ref name="BensonCompton1981" /><ref name="SternStern1992">{{cite book |last1=Stern |first1=Jane |last2=Stern |first2=Michael |title=Jane & Michael Stern's Encyclopedia of Pop Culture: An A to Z Guide of Who's who and What's What, from Aerobics and Bubble Gum to Valley of the Dolls and Moon Unit Zappa |date=1992 |publisher=HarperPerennial |location=New York |isbn=9780060553432 |pages=266–268 |edition=1st |chapter=Kohoutek}}</ref> NASA also pursued an extensive [[public relations]] campaign that led to widespread coverage of the comet's approach in American newspapers in the final six months of 1973.<ref name="BensonCompton1981" /> [[Dale D. Myers]], the Associate Administrator for Manned Space Flight at NASA, commented in July 1973 that "comets [of Kohoutek's] size come this close once in a century," further adding to the public interest.<ref name="BensonCompton1981" /><ref name="Stoyan2015" /> On the 30 July 1973 edition of the ''New York Times'', columnist [[William Safire]] wrote that Kohoutek "may well be the biggest, brightest, most spectacular astral display that living man has ever seen".<ref name="Safire1973" /> In August&nbsp;1973, a reporter from ''[[The Mercury News]]'' in [[San Jose, California]], wrote that researchers preparing to study the comet at NASA's [[Ames Research Center]] were calling Kohoutek "the comet of the century"; this honorific quickly became associated with the comet. NASA's decision to postpone the launch of Skylab 4 to support observations of the comet only further intensified public interest and added to the attention of the press towards Kohoutek after 16 August 1973. Despite more reserved and cautious statements from scientists regarding the comet's luminosity, stories referencing the more bullish and earlier estimates of Kohoutek's brightness continued to circulate as the comet drew closer, disregarding revised estimates.<ref name="BensonCompton1981" /> One edition of ''[[Time (magazine)|Time]]'' placed the comet on its cover.<ref name="Stoyan2015" /> However, NASA spokespeople continued to relay an expectation that the comet would be a generational event. As November 1973 passed, newspapers began to more frequently convey the guarded skepticism that surrounded Kohoutek's brightness. Seizing the opportunity created by the comet in giving NASA good publicity, an adviser to NASA administrator [[James C. Fletcher]] proposed a half-hour [[television special]] featuring the comet, Skylab, and a Christmas message from the [[first family of the United States|first family of the U.S.]] However, John Donnelly, the NASA Assistant Administrator for Public Affairs, derided the proposal because of its intertwining of politics with NASA. The proposal continued to be hotly contested within NASA but was eventually dropped. Although a spokesman for the [[Goddard Space Flight Center]] later stated that Kohoutek was a "roaring success" for science, "from a public relations point of view, it [was] a disaster."<ref name="BensonCompton1981" />

[[File:Queen Elizabeth 2 IMO 6725418 P Cuxhaven 08-1973.jpg|thumb|left|The ''Queen Elizabeth 2'' (pictured in August&nbsp;1973) sailed on a special three day cruise offering telescope views and comet lectures in December 1973|alt=Photograph of the starboard side of Queen Elizabeth II.]]
''[[Queen Elizabeth 2]]'' sailed on a sold-out "cruise to nowhere" dedicated to the comet from 9–12 December&nbsp;1973, including guest of honor Luboš Kohoutek; [[Isaac Asimov]] and [[Kenneth Franklin]] were also present on the cruise.<ref name="Warwick1999">{{cite book |last1=Warwick |first1=Ronald W. |title=QE2: The Cunard Line Flagship, Queen Elizabeth II |date=1999 |publisher=W.W. Norton & Co |location=New York |isbn=9780393047721 |page=97 |edition=3rd |chapter=Trafalgar House, Cunard, and the ''QE2''}}</ref><ref name="ScienceCruises">{{cite news |last1=Segal |first1=Jonathan |title=Science Cruises Becoming Popular |url=https://www.nytimes.com/1973/11/04/archives/notes-science-cruises-becoming-popular-airline-terminal-saved-pick.html |access-date=14 July 2022 |work=The New York Times |date=4 November 1973 |location=New York |page=624 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233603/https://www.nytimes.com/1973/11/04/archives/notes-science-cruises-becoming-popular-airline-terminal-saved-pick.html |url-status=live }}</ref> Astrophotography discussions and lectures discussing astronomy and the comet, led by scientists from [[Dowling College]], were also held on board.<ref name="ScienceCruises" /><ref name="DimShowingLI">{{cite news |last1=Barney |first1=Lillian |title='Comet of Century' to Get Dim Showing Over L.I. |url=https://www.nytimes.com/1973/12/02/archives/-comet-of-century-to-get-dim-showing-over-li-telescope-use-is.html |access-date=14 July 2022 |work=The New York Times |date=2 December 1973 |location=New York |page=164 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233609/https://www.nytimes.com/1973/12/02/archives/-comet-of-century-to-get-dim-showing-over-li-telescope-use-is.html |url-status=live }}</ref> Overcast and rainy conditions prevented views of the comet during the trek, which departed from New York and remained along the U.S. East Coast before returning to New York.<ref name="Warwick1999" /><ref name="FailsShowQE2">{{cite news |last1=Schuman |first1=Wendy |title=Star Fails to Show For QE2 Gazers |url=https://www.nytimes.com/1973/12/16/archives/star-fails-to-show-for-qe2-gazers-parties-and-comet-watching-series.html |access-date=14 July 2022 |work=The New York Times |date=16 December 1973 |location=New York |page=137 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233606/https://www.nytimes.com/1973/12/16/archives/star-fails-to-show-for-qe2-gazers-parties-and-comet-watching-series.html |url-status=live }}</ref><ref name="BusinessBoomlet" /> In his [[Autobiographies of Isaac Asimov|final autobiography]], Asimov later wrote that "even if it hadn't been [cloudy and rainy every night], Comet Kohoutek proved a colossal disappointment."<ref name="Asimov1995">{{cite book |last1=Asimov |first1=Isaac |title=I. Asimov: A Memoir |date=1995 |publisher=Bantam |location=New York |isbn=9780553569971 |page=365 |edition=Bantam pbk. |chapter=Cruises}}</ref> ''Queen Elizabeth 2'' later embarked on similar cruises in the Caribbean in January&nbsp;1974 which afforded better views of the comet; [[Buzz Aldrin]], [[Hugh Downs]], [[Burl Ives]], and [[Carl Sagan]] featured on the Caribbean cruises, with [[Hayden Planetarium]] director Mark Chartrand serving as the cruise's resident astronomer.<ref name="Warwick1999" /><ref name="BusinessBoomlet" /> The ''[[SS Rotterdam]]'' departed on a nine-day cruise beginning on 3 January 1974 to [[Puerto Rico]] and the [[Virgin Islands]] that was billed as a "Caribbean Comet Watch Cruise"; educational astronomy segments on the cruise were led by astronomer [[Lloyd Motz]]. [[Freelandia]] flew 149 of its members to [[Peru]] to view the comet in December&nbsp;1973. Another chartered trip sponsored by the Hayden Planetarium to take passengers to observatories to view the comet was canceled.<ref name="BusinessBoomlet" /> The [[American Automobile Association]] advised travelers to bring binoculars on roadtrips between December&nbsp;1973 and February&nbsp;1974 in anticipation of the comet's apparition.<ref name="TravelNotesEurope">{{cite news |title=Travel Notes: Survey Of Restrictions on Driving in Europe |url=https://www.nytimes.com/1973/12/09/archives/travel-notes-survey-of-restrictions-on-driving-in-europe-worlds.html |access-date=14 July 2022 |work=The New York Times |date=9 December 1973 |location=New York |page=594 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233607/https://www.nytimes.com/1973/12/09/archives/travel-notes-survey-of-restrictions-on-driving-in-europe-worlds.html |url-status=live }}</ref> Planetariums throughout the U.S. launched comet-centered events and established [[hotline]]s offering information regarding Kohoutek.<ref name="BensonCompton1981" /> The [[William Miller Sperry Observatory]] at [[Union County College]] and the observatory on the roof of Boyden Hall at [[Rutgers University–Newark]]{{snd}}both in [[New Jersey]]{{snd}}made their facilities accessible to the public interested in the comet, with the former maintaining a phone line for updates on the comet.<ref name="CollegesAid">{{cite news |title=Colleges Aid Comet Watchers |url=https://www.nytimes.com/1973/12/16/archives/colleges-aid-comet-watchers.html |access-date=14 July 2022 |work=The New York Times |date=16 December 1973 |location=New York |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233604/https://www.nytimes.com/1973/12/16/archives/colleges-aid-comet-watchers.html |url-status=live }}</ref>

{{clear}}

== Cultural impact ==
[[File:Elihu Vedder - Star of Bethlehem - 1879-80.jpg|thumb|Kohoutek's anticipated brightness and apparition around Christmas was a spiritual significance in some religious fundamentalist circles.|alt=Painting of a scene including the Star of Bethlehem]]
{{Blockquote
|text=It is among nonpatients that I have seen the most interest in the comet; in some instances the impact has already been profound. Many Christians have seen an umistakable link between the fact of Kohoutek's December 28 perihelion [...] and the Christmas observance. Some individuals have seemed to downplay the signifiance the event has for reasons of propriety or in the interest of appearing sensible. [...] A fair number of young adults have taken the comet to be some kind of sign, the significance to each individual varying with his specific religious or general spiritual outlook.
|author=Lawrence Weiner
|title=letter to the editor
|source=''[[American Journal of Psychiatry]]'' (March 1974)<ref name="Weiner1974">{{cite journal |last1=Weiner |first1=Lawrence |title=On the Comet Kohoutek |journal=American Journal of Psychiatry |date=March 1974 |volume=131 |issue=3 |pages=331–c–332 |doi=10.1176/ajp.131.3.331-c |pmid=26951657 |pmc=4812706}}</ref>
}}

With predictions of Kohoutek's exceptional brightness being well-circulated, the comet became a cultural and media phenomenon by mid-summer 1973, leading to widespread cometary paraphernalia, apparel, and accessories.<ref name="Rao2020" /> Sales of telescopes rose sharply leading up to the comet's anticipated appearance. [[Edmund Scientific Corporation]] reported a 200&nbsp;percent increase in its sale of telescopes in 1973 relative to 1972.<ref name="Time" />{{rp|2}} Sales for telescopes and binoculars quadrupled at [[Macy's]] after the company ran a seven-column ad in the ''New York Times''. Interest in popular astronomy books also increased as the comet neared. Pinnacle Books published and quickly sold 750,000 copies of astrologer Joseph Goodavage's book "The Comet Kohoutek", which described the comet as a "harbinger of God".<ref name="BusinessBoomlet" /><ref name="Perlman1974">{{cite journal |last1=Perlman |first1=David |title=Science and the Mas Media |journal=Daedalus |date=1974 |volume=103 |issue=3 |pages=207–222|jstor=20024229}}</ref> Astronomers appeared more frequently on television talk shows and were in greater demand as lecturers to speak on comets;<ref name="BusinessBoomlet">{{cite news |last1=Carlinsky |first1=Dan |title=Business Boomlet Trailing Kohoutek |url=https://www.nytimes.com/1973/12/26/archives/business-boomlet-trailing-kohoutek-telescope-sales-up-300.html |access-date=14 July 2022 |work=The New York Times |date=26 December 1973 |page=65 |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233602/https://www.nytimes.com/1973/12/26/archives/business-boomlet-trailing-kohoutek-telescope-sales-up-300.html |url-status=live }}</ref> Carl Sagan appeared on ''[[The Tonight Show Starring Johnny Carson]]'' to discuss the comet.<ref name="Eicher2013">{{cite book |last1=Eicher |first1=David J. |title=Comets!: Visitors from Deep Space |date=2013 |publisher=Cambridge University Press |location=New York |isbn=9781107513501}}</ref>{{rp|6}}

The timing of Kohoutek's visible apparition around [[Christmastide]] was of spiritual significance to fundamentalist Christians; in some circles, Kohoutek became known as the "Christmas comet". It renewed interest in the nature of the [[Star of Bethlehem]], including the idea that the event may have been a comet. Some fundamentalist [[Protestantism|Protestants]] interpreted the comet as a harbinger of the [[Second Coming]]. Radio preacher [[Carl McIntire]] stated that the comet was "so beyond anything men have ever seen before" and that "only the [[Bible|Holy Scripture]] [offered] anything to explain it."<ref name="FundamentalistsChristmasComet">{{cite news |last1=Fiske |first1=Edward B. |title=Fundamentalists View 'Christmas Comet' as a Sign |url=https://www.nytimes.com/1973/12/24/archives/fundamentalists-view-christmas-comet-as-a-sign-conjunction-theory.html |access-date=14 July 2022 |work=The New York Times |date=24 December 1973 |location=New York |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233609/https://www.nytimes.com/1973/12/24/archives/fundamentalists-view-christmas-comet-as-a-sign-conjunction-theory.html |url-status=live }}</ref> Kohoutek also took on spiritual significance in the [[New Age]] movement and other followers of [[Western esotericism]].<ref name="Stoyan2015" /> One view was that the comet heralded a new cosmic age{{snd}}the "age of Kohoutek". Proponents of this view organized the Kohoutek Celebration of Consciousness at the [[Bill Graham Civic Auditorium]] in [[San Francisco]] in January 1974.<ref name="AgeOfKohoutek">{{cite news |title=Welcoming 'the age of Kohoutek' |url=https://www.newspapers.com/clip/105665300/ |via=Newspapers.com |access-date=15 July 2022 |work=San Francisco Examiner |issue=4 |volume=1974 |date=27 January 1974 |page=3 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013926/https://www.newspapers.com/clip/105665300/the-san-francisco-examiner/ |url-status=live }} {{free access}}</ref> For some, the comet's arrival was a portent of disaster.<ref name="Hoopes2011">{{cite journal |last1=Hoopes |first1=John W. |title=A critical history of 2012 mythology |journal=Proceedings of the International Astronomical Union |date=January 2011 |volume=7 |issue=S278 |pages=240–248 |doi=10.1017/S174392131101266X|bibcode=2011IAUS..278..240H |s2cid=194041975 |doi-access=free }}</ref> In 1973, [[David Berg]], founder of the [[Children of God (cult)|Children of God]], predicted that Comet Kohoutek foretold a colossal [[doomsday event]] in the United States by the end of January 1974 because of [[divine judgment]] and "America's wickedness". Some of the movement's followers intended to leave the U.S. in response to the impending comet.<ref name="FundamentalistsChristmasComet" /> There were other circulated fringe claims predicting that the comet would cause mass hysteria or spell death for humanity by igniting the global oil supply.<ref name="Time" />{{rp|2}}

Because Kohoutek fell far short of expectations, its name became synonymous with spectacular disappointment.<ref name="MayBeFlop">{{cite news |last1=MacPherson |first1=Les |title=Comet's arrival may be a flop |url=https://www.pressreader.com/canada/regina-leader-post/20130104/281608122776055 |access-date=14 July 2022 |work=Regina Leader-Post |date=4 January 2013 |location=Regina, Saskatchewan |archive-date=14 July 2022 |archive-url=https://web.archive.org/web/20220714233519/https://www.pressreader.com/canada/regina-leader-post/20130104/281608122776055 |url-status=live }}</ref><ref name="Evans2012">{{cite book |last1=Evans |first1=Ben |title=At Home in Space: The Late Seventies into the Eighties |date=2012 |publisher=Springer Science+Business Media, LLC |location=New York |isbn=9781441988102}}</ref>{{rp|199}} [[Russell Baker]] described the comet as "the biggest flopperoo since '[[Kelly (musical)|Kelly]]' hit [[Broadway theatre|Broadway]]" and "the [[Edsel]] of the firmament", among other witty metaphors.<ref name="CosmicFlopperoo">{{cite news |last1=Baker |first1=Russell |title=The Cosmic Flopperoo |url=https://www.nytimes.com/1974/01/15/archives/the-cosmic-flopperoo-observer.html |access-date=15 July 2022 |work=The New York Times |date=15 January 1974 |location=New York |page=37 |archive-date=15 July 2022 |archive-url=https://web.archive.org/web/20220715043243/https://www.nytimes.com/1974/01/15/archives/the-cosmic-flopperoo-observer.html |url-status=live }}</ref> While newspapers had been touting the comet's brightness for the latter half of 1973, the anticlimactic display led to satirical and parodical reporting following Kohoutek's passage. For instance, the ''[[Chicago Tribune]]'' featured a satirical article linking the optimistic brightness predictions to an effort to distract the public from the [[Watergate scandal]] or to a conspiracy to boost telescope sales.<ref name="BensonCompton1981" /> The widely circulated inaccurate projections came during a time of increasing distrust of the sciences that ''Time'' termed a "deepening disillusionment".<ref name="Caroll1990">{{cite book |last1=Carroll |first1=Peter N. |title=It Seemed Like Nothing Happened: America in the 1970s |date=1990 |publisher=Rutgers University Press |location=New Brunswick, New Jersey |isbn=9780813515380 |pages=13–14 |chapter="To Heal the Fragmentations": Redefining Authority at Mid-Decade}}</ref> Mainstream media shied away from extensive coverage of comets following Kohoutek; despite [[Comet West]] becoming bright enough to be visible in daylight in March 1976, West received little attention from the press compared to the media frenzy that preceded Kohoutek.<ref name="Rao2020" /> Though astronomers and the sciences received backlash due to the comet's underwhelming performance, much of the general public's disdain was also directed towards astrologers and cultists who ascribed a transcendental significance to the comet's apparition.<ref name="Perlman1974" />

In response to the disappointing display from the comet, students at [[Pitzer College]] organized the Kohoutek Music and Arts Festival in January&nbsp;1974,<ref name="KohoutekPlanningPitzer">{{cite news |last1=Greenberg |first1=Annie |title=Kohoutek Planning Commences |url=https://www.pitzer.edu/archives/wp-content/uploads/sites/34/2016/06/ToS_1989.03.01.pdf |access-date=15 July 2022 |work=The Other Side |issue=2 |volume=14 |location=Claremont, California |pages=1–3 |archive-date=20 September 2022 |archive-url=https://web.archive.org/web/20220920013924/https://www.pitzer.edu/archives/wp-content/uploads/sites/34/2016/06/ToS_1989.03.01.pdf |url-status=live }}</ref> which became an annual event featuring various musical artists.<ref name="KohoutekGZA">{{cite news |last1=Rojas |first1=Luca |title=Kohoutek Music Festival Goes Big with GZA |url=https://tsl.news/life-style1504/ |access-date=15 July 2022 |work=The Student Life |date=30 April 2010 |archive-date=27 July 2021 |archive-url=https://web.archive.org/web/20210727213057/https://tsl.news/life-style1504/ |url-status=live }}</ref> Several music albums and songs released in the 1970s and 1980s were dedicated to or named after Kohoutek, such as "Kohoutek" from [[Journey (band)|Journey]]'s [[Journey (Journey album)|eponymous debut album]] (released in 1975).<ref name="Dick2015">{{cite book |last1=Bainbridge |first1=William Sins |editor1-last=Dick |editor1-first=Steven J. |title=Historical Studies in the Societal Impact of Spaceflight |date=2015 |publisher=NASA |location=Washington, D.C. |page=21 |url=https://www.nasa.gov/sites/default/files/atoms/files/historical-studies-societal-impact-spaceflight-ebook_tagged.pdf |access-date=15 July 2022 |chapter=The Impact of Space Exploration on Public Opinions, Attitudes, and Beliefs |archive-date=1 October 2020 |archive-url=https://web.archive.org/web/20201001015436/https://www.nasa.gov/sites/default/files/atoms/files/historical-studies-societal-impact-spaceflight-ebook_tagged.pdf |url-status=live }}</ref><ref name="Karam2017">{{cite book |last1=Karam |first1=P. Andrew |title=Comets: nature and culture |date=2017 |publisher=Reaktion Books |location=London |isbn=9781780238586}}</ref> [[Sun Ra]] played a concert at [[The Town Hall (New York City)|The Town Hall]] in New York dedicated to Kohoutek's arrival on 22 December 1973.<ref name="HegartyHalliwell2011">{{cite book |last1=Hegarty |first1=Paul |last2=Halliwell |first2=Martin |title=Beyond and Before: Progressive Rock Since the 1960s |date=2011 |publisher=Bloomsbury Publishing |location=New York |isbn=9780826423320 |page=115 |chapter=Progressive Fusion}}</ref> Other musical groups with works influenced by the comet included [[Kraftwerk]], [[Pink Floyd]], [[Argent]], [[R.E.M.]], and [[Weather Report Girl]].<ref name="Eicher2013" />{{rp|7}} References to Kohoutek permeated other forms of popular media, such as in the comic strip ''[[Peanuts]]'' over a week-long period,<ref name="Eicher2013" />{{rp|7}} in the sitcom ''[[El Chavo del Ocho]]'', and a poem by [[Jaime Sabines]].<ref name="Madrid2015">{{cite book |last1=Madrid |first1=Alejandro L. |title=In Search of Julián Carrillo and Sonido 13 |date=2015 |publisher=Oxford University Press |location=New York |isbn=9780190215781 |page=223 |chapter=Experimentalism, Mythology}}</ref>

In ''[[The Defenders (comics)|The Defenders]]'' #15 (September 1974), the Comet Kohoutek is mentioned as having freed Magneto from imprisonment within the Earth's core.<ref>''The Defenders'' #15 (September 1974), Marvel Comics</ref>
{{clear}}

== See also ==
* [[Comet ISON]]&nbsp;– [[sungrazing comet]] that disintegrated upon passing close to the Sun
* [[C/1989 X1 (Austin)]]&nbsp;– fell short of brightness predictions in spring 1990
* [[Comet Ikeya–Seki]]&nbsp;– one of the brightest comets on record
* [[Oort cloud]]
* [[Interstellar object]]

== Notes ==
{{notelist}}

== References ==
{{reflist}}

== External links ==
* {{JPL small body|name=C/1973 E1}}

{{Commons category|Comet Kohoutek}}

{{Comets}}
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[[Category:Non-periodic comets]]
[[Category:The Family International]]
[[Category:Prophecy in Christianity]]
[[Category:Astronomical objects discovered in 1973|19730307]]
[[Category:Great comets]]
[[Category:Discoveries by Luboš Kohoutek]]
[[Category:1973 in science]]
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