View source for Comet West

{{short description|Great Comet of 1976}}
{{use dmy dates|date=April 2025}}
{{Infobox comet
| name            = C/1975 V1 (West)<br>(Great Comet of 1976)
| image           = C-west-1976-ps.jpg
| caption         = Comet West photographed from the [[European Southern Observatory]] on 9 March 1976
| discoverer      = [[Richard M. West]]
| discovery_site  = [[European Southern Observatory]]
| discovery_date  = 10 August 1975
| designations    = 1976 VI, 1975n
| orbit_ref       = {{r|jpl1}}
| epoch           = 10 May 1976 ([[Julian day|JD]] 2442908.5)
| observation_arc = 199 days
| obs             = 113
| perihelion      = 0.197 AU
| aphelion        = 1,500 AU (inbound)
| semimajor       = 
| eccentricity    = 0.99997
| period          = ~558,000 years
| inclination     = 43.074°
| asc_node        = 118.92°
| arg_peri        = 358.43°
| mean            = 
| tjup            = 0.402
| Earth_moid      = 0.555 AU
| Jupiter_moid    = 1.194 AU
| physical_ref    = {{r|Kronk}}
| M1              = 4.4
| M2              = 
| magnitude       = –3.0<br>{{small|(1976 apparition)}}
| last_p          = 25 February 1976
| next_p          = 
}}

'''Comet West''', formally designated as '''C/1975 V1''', '''1976 VI''', and '''1975n''', was a [[comet]] described as one of the brightest objects to pass through the inner [[Solar System]] in 1976. It is often described as a "[[great comet]]."{{r|jpl2}}

== History ==
[[File:Animation of C／1975 V1 orbit around Sun.gif|280px|thumb|left|Animation of C/1975 V1 orbit around Sun<br>{{legend2|magenta|C/1975 V1}}{{·}}{{legend2|Yellow|Sun}}{{·}}{{legend2| Lime |Mercury }}{{·}}{{legend2|gold|Venus}}{{·}}{{legend2|Royalblue|Earth}} {{·}}{{legend2|OrangeRed|Mars}}]]

It was discovered photographically by [[Richard M. West]], of the [[European Southern Observatory]], on 10 August 1975. The comet came to [[perihelion]] (closest approach to the Sun) on 25 February 1976.{{r|jpl1}} During perihelion the comet had a minimum solar elongation of 6.4° and as a result of [[forward scatter]]ing reached a peak [[apparent magnitude]] of −3.{{r|Kronk}} From 25 to 27 February, observers reported that the comet was bright enough to study during full daylight.{{r|Kronk}}

Despite its brightness, Comet West went largely unreported in the popular media. This was partly due to the relatively disappointing display of [[Comet Kohoutek]] in 1973, which had been widely predicted to become extremely prominent: scientists were wary of making predictions that might raise public expectations.{{r|Burnham_2000}}

''[[The New York Times]]'', however, reported this about Comet West on 2 March 1976:{{r|NYT-19760302}}
{{Blockquote
| text= From tomorrow until Sunday a comet that may prove one of the brightest in this decade is expected to reach maximum visibility in the eastern sky before sunrise. ... By Wednesday, [[Brian G. Marsden|Dr. Marsden]] believes, it will be far enough from the sun to be visible to the unaided eye
| author= Walter Sullivan
| source= ''[[The New York Times]]'' (2 March 1976)}}

== Period ==
[[File:Comet_West_skypath.png|thumb|left|Sky path for Comet West, with 7 day motion. The retrograde loops are caused by parallax from Earth's annual motion around the Sun. The most movement occurs when the comet is closest to Earth.]]

With a nearly [[parabolic trajectory]], estimates for the [[orbital period]] of this comet have varied from 254,000{{r|Kronk}} to 558,000 years.{{r|Coffey_2009}} Computing the [[curve fitting|best-fit]] orbit for this long-period comet is made more difficult since it underwent a [[Comet nucleus#Splitting|splitting event]] which may have caused a non-gravitational [[Perturbation (astronomy)|perturbation]] of the orbit. The 2008 [[Smithsonian Astrophysical Observatory|SAO]] Catalog of Cometary Orbits shows 195 observations for C/1975 V1 and 135 for C/1975 V1-A, for a combined total of 330 (218 observations were used in the fit).

== Breakup ==
[[File:C-west-mar1976-ps.jpg|right|thumb|Comet West in March 1976, around peak brightness.]]

Before the [[perihelion]] passage, and using 28 positions obtained between 10 August 1975 and 27 January 1976, Comet West was estimated to have an orbital period of about 254,000 years.{{r|Kronk}} As the comet passed within 30 million km of the Sun, the nucleus was observed to split into four fragments.{{r|Eicher_2013}}

The first report of the split came around 7 March 1976 at 12:30 UTC, when reports were received that the comet had broken into two pieces. Astronomer Steven O'Meara, using the 9-inch Harvard Refractor, reported that two additional fragments had formed on the morning of 18 March.{{Citation needed|date = October 2016}}

The fragmentation of the nucleus was, at the time, one of very few comet breakups observed, one of the most notable previous examples being the [[Great Comet of 1882]], a member of the [[Kreutz Sungrazers|Kreutz Sungrazing]] 'family' of comets. More recently, comets [[Schwassmann-Wachmann-3]] (73P), [[C/1999 S4]] LINEAR, and [[57P/du Toit-Neujmin-Delporte]], have been observed to split or disintegrate during their passage close to the Sun.{{Citation needed|date = October 2016}}

The comet has been more than {{convert|50|AU|e9km|abbr=unit}} from the Sun since 2003.{{r|horizons}}

== Nomenclature ==
In the nomenclature of the time, it was known as ''Comet 1976 VI'' or ''Comet 1975n'', but the modern nomenclature is ''C/1975 V1''. (Note that "1976 VI" uses the Roman numeral VI = 6, while "C/1975 V1" is the letter V and the number 1).

== See also ==
* [[List of Solar System objects by greatest aphelion]]

== References ==
{{Reflist|refs=

<ref name="Burnham_2000">{{cite book
| author1= R. Burnham, Jr.
| author2= D. H. Levy
| title= Great Comets
| url= https://books.google.com/books?id=HkFKMksEwPcC&pg=PA73
| publisher= Cambridge University Press
| edition= 1st
| year= 2000
| page= 73
| isbn= 978-0-521-64600-0 }}
</ref>

<ref name="Coffey_2009">{{cite web
| author1= J. Coffey
| title= Comet West
| url= http://www.universetoday.com/40814/comet-west/
| website= Universe Today
| date= 21 September 2009
| access-date= 1 February 2011
| archive-url= https://web.archive.org/web/20120920222133/http://www.universetoday.com/40814/comet-west/
| archive-date= 20 September 2012
| url-status= dead }}
</ref>

<ref name="Eicher_2013">{{cite book
| author1= D. J. Eicher
| title= Comets! Visitors from Deep Space
| chapter-url= https://books.google.com/books?id=Ud2aAAAAQBAJ&pg=PA77
| publisher= Cambridge University Press
| year= 2013
| chapter= Comets of the Modern Era
| page= 77
| isbn= 978-1-107-62277-7 }}
</ref>

<ref name="horizons">{{cite web
| author1= [[JPL Horizons On-Line Ephemeris System|Horizons]] output
| url= http://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=1975V1
| title= Observer Table for Comet C/1975 V1-A (West)
| access-date= 25 February 2019 }} (Observer Location:@sun)
</ref>

<ref name="jpl1">{{cite web
| title= C/1975 V1-A (West) – JPL Small-Body Database Lookup
| url= https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=1975V1
| website= ssd.jpl.nasa.gov
| publisher= [[Jet Propulsion Laboratory]]
| access-date= 7 August 2011 }}
</ref>

<ref name="jpl2">{{cite web
| author1= D. K. Yeomans
| title= Great Comets in History
| url= https://ssd.jpl.nasa.gov/sb/great_comets.html
| website= ssd.jpl.nasa.gov
| publisher= [[Jet Propulsion Laboratory]]
| date= April 2007
| access-date= 28 December 2007 }}
</ref>

<ref name="Kronk">{{cite web
| author1= G. W. Kronk
| title= C/1975 V1 (West)
| website= Cometography.com
| url= http://cometography.com/lcomets/1975v1.html
| access-date= 1 February 2011 }}
</ref>

<ref name="NYT-19760302">{{cite web 
| author1= W. Sullivan
| title= Comet Expected in Sky for Week
| url= https://www.nytimes.com/1976/03/02/archives/comet-expected-in-sky-for-week-maximum-visibility-would-be-in-east.html
| newspaper= [[The New York Times]]
| page= 17
| date= 2 March 1976
| access-date= 16 November 2023 }}</ref>

}}

== External links ==
{{Commons category|Comet West (C/1975 V1)}}
* {{JPL Small Body|name=C/1975 V1|id=1001163}}

{{Comets}}
{{Authority control}}

{{DEFAULTSORT:West, 1975 V1}}
[[Category:Non-periodic comets]]
[[Category:Astronomical objects discovered in 1975|19750810]]
[[Category:Great comets]]
[[Category:Split comets]]