Editing Octans

{{Short description|Constellation in the southern celestial hemisphere, containing the south celestial pole}}
{{Infobox constellation
| name = Octans
| abbreviation = Oct<ref name=boundary>{{Cite journal | title=Octans, Constellation Boundary | journal=The Constellations | publisher=International Astronomical Union | url=https://www.iau.org/public/themes/constellations/#oct | access-date=10 Mar 2023}}</ref>
| genitive = Octantis
| pronounce = {{IPAc-en|ˈ|ɒ|k|t|æ|n|z}}, genitive {{IPAc-en|ɒ|k|ˈ|t|æ|n|t|ɪ|s}}
| symbolism = the [[Octant (instrument)|Octant]]
| RA = {{RA|00}} to {{RA|24}}<ref name=boundary/>
| dec= {{DEC|-74.30}} to {{DEC|−90}}<ref name=boundary/>
| family = [[La Caille Family|La Caille]]
| quadrant = SQ4
| areatotal = 291
| arearank = 50th
| numbermainstars = 3
| numberbfstars = 27
| numberstarsplanets = 3
| numberbrightstars = 0
| numbernearbystars = 1
| brighteststarname = [[Nu Octantis|ν Oct]]
| starmagnitude = 3.73
| neareststarname = [[LHS 531]]
| stardistancely = 28.11
| stardistancepc = 8.62
| numbermessierobjects = 0
| meteorshowers = 0
| bordering = [[Tucana]]<br />[[Indus (constellation)|Indus]]<br />[[Pavo (constellation)|Pavo]]<br />[[Apus]]<br />[[Chamaeleon]]<br />[[Mensa (constellation)|Mensa]]<br />[[Hydrus]]
| latmax = [[Equator|0]]
| latmin = [[South Pole|90]]
| month = October
| notes=Circumpolar
}}

'''Octans''' is a faint [[constellation]] located in the deep [[southern celestial hemisphere|Southern Sky]]. Its name is [[Latin]] for the eighth part of a circle, but it is named after the [[octant (instrument)|octant]], a [[navigational instrument]]. Devised by [[kingdom of France|French]] [[astronomer]] [[Nicolas Louis de Lacaille]] in 1752, Octans remains one of the [[IAU designated constellations|88 modern constellations]]. The southern [[celestial pole]] is located within the boundaries of Octans.

==History and mythology==
Octans was one of 14 constellations created by French astronomer [[Nicolas Louis de Lacaille]] during his expedition to the [[Cape of Good Hope]], and was originally named ''l’Octans de Reflexion'' (“the reflecting octant”) in 1752, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the [[Cape of Good Hope]]. He devised fourteen new constellations in uncharted regions of the [[Southern Celestial Hemisphere]] not visible from Europe. All but one honoured instruments that symbolised the [[Age of Enlightenment]].{{efn|1=The exception is [[Mensa (constellation)|Mensa]], named for the [[Table Mountain]]. The other thirteen (alongside Horologium) are [[Antlia]], [[Caelum]], [[Circinus]], [[Fornax]], [[Horologium (constellation)|Horologium]], [[Microscopium]], [[Norma (constellation)|Norma]], [[Pictor]], [[Pyxis]], [[Reticulum]], [[Sculptor (constellation)|Sculptor]] and [[Telescopium]].<ref name=wagman>{{cite book |last=Wagman |first=Morton |date=2003 |title=Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others |publisher=The McDonald & Woodward Publishing Company |location=Blacksburg, Virginia |isbn=978-0-939923-78-6 |pages=6–7}}</ref>}}<ref name=wagman/>

It was part of his catalogue of the southern sky, the ''Coelum Australe Stelliferum'', which was published posthumously in 1763. In Europe, it became more widely known as ''Octans Hadleianus'', in honor of [[England|English]] mathematician [[John Hadley]], who invented the octant in 1730. There is no real mythology related to Octans, partially due to its faintness and relative recentness, but mostly because of its extreme southerly latitude.{{sfn|Staal|1988|p=257}}

==Notable features==

=== Stars ===
{{see also|List of stars in Octans}}

[[Image:Constellation Octans.jpg|thumb|left|200px|The constellation Octans as it can be seen by the [[naked eye]].]]

Octans is a generally inconspicuous constellation with only one star brighter than magnitude 4; its brightest member is [[Nu Octantis]], a [[Stellar classification|spectral class]] K1&nbsp;III [[giant star]] with an [[apparent magnitude]]&nbsp;3.73. It is 63.3 ± 0.8 [[light-year]]s distant from Earth.<ref name=Gaia-DR2nu>{{cite DR2|6356375508717699584}}</ref>

[[Beta Octantis]] is the second brightest star in the constellation.

[[Sigma Octantis|Polaris Australis (Sigma Octantis)]], the southern [[pole star]], is a magnitude&nbsp;5.4 star just over 1&nbsp;degree away from the true south celestial pole. Its relative faintness means that it is not practical for navigation.{{sfn|Staal|1988|p=258}}

[[BQ Octantis]] is a fainter, magnitude 6.82 star located much closer to the South Pole (at less than a degree) than Sigma.

In addition to having the current southern pole star of Earth, Octans also contains the southern pole star of the planet [[Saturn]], which is the magnitude&nbsp;4.3 [[Delta Octantis]].

The [[Astronomical Society of Southern Africa]] in 2003 reported that observations of the [[Mira variable]] stars [[R Octantis|R]] and [[T Octantis]] were urgently needed.<ref name=cooper>{{cite journal|last=Cooper|first=Tim|date=2003|title=Presidential address: Amateur Observations – Successes and Opportunities|journal=Monthly Notes of the Astronomical Society of Southern Africa|volume=62|pages=234–240|bibcode=2003MNSSA..62..234C}}</ref>

Four star systems are known to have planets. [[Mu2 Octantis|Mu<sup>2</sup> Octantis]] is a binary star system, the brighter component of which has a planet. [[Nu Octantis]] A also has a planet orbiting. [[HD 142022]] is a binary system, a component of which is a sunlike star with a massive planet with an orbital period of 1928 ± 46 days. [[HD 212301]] is a yellow-white main sequence star with a [[hot jupiter]] that completes an orbit every 2.2 days.

{{clear|left}}

===Deep sky objects===
[[File:NGC 7098 ESO.jpg|thumb|right|[[NGC 7098]]]]
[[NGC 2573]] (also known as Polarissima Australis) is a faint [[barred spiral galaxy]] that happens to be the closest [[NGC object]] to the [[south celestial pole]]. [[NGC 7095]] and [[NGC 7098]] are two barred spiral galaxies that are 115 million and 95 million light-years distant from Earth respectively. The sparse [[open cluster]] [[Collinder catalogue|Collinder 411]] is also located in the constellation.

==Namesakes==
{{USS|Octans|AF-26}} was a [[stores ship]] used by the [[United States Navy]] during [[World War II]].

==See also==
* [[Octans (Chinese astronomy)]]

== Notes ==
{{notelist}}

==References==
;Citations
{{reflist}}

;References
{{refbegin}}
* {{citation |first1 = Ian |last1 = Ridpath |first2=  Wil |last2 = Tirion |year = 2017 |title = Stars and Planets Guide |publisher = Princeton University Press |isbn = 978-0-691-17788-5}}
* {{citation |first = Julius D.W. |last = Staal |title = The New Patterns in the Sky: Myths and Legends of the Stars |publisher = The McDonald and Woodward Publishing Company |year = 1988 |isbn = 0-939923-04-1}}
{{refend}}

== External links ==
* [http://www.allthesky.com/constellations/apus/constell.html The Deep Photographic Guide to the Constellations: Octans]
* [http://astrojan.nhely.hu/octans.htm The clickable Octans]
* [http://www.starrynightphotos.com/constellations/octans.htm Starry Night Photography : Octans]
* [http://www.ianridpath.com/startales/octans.html Star Tales – Octans]

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[[Category:Octans| ]]
[[Category:Southern constellations]]
[[Category:Constellations listed by Lacaille]]