Editing Apsis (section)

==Terminology==
The words "pericenter" and "apocenter" are often seen, although periapsis/apoapsis are preferred in technical usage.
* For generic situations where the primary is not specified, the terms ''pericenter'' and ''apocenter'' are used for naming the extreme points of orbits (see table, top figure);  ''periapsis'' and ''apoapsis'' (or ''apapsis'') are equivalent alternatives, but these terms also frequently refer to distances—that is, the smallest and largest distances between the orbiter and its host body (see second figure).
* For a body orbiting the [[Sun]], the point of least distance is the ''perihelion'' ({{IPAc-en|ˌ|p|ɛr|ᵻ|ˈ|h|i:|l|i|ə|n}}), and the point of greatest distance is the ''aphelion'' ({{IPAc-en|æ|p|ˈ|h|i:|l|i|ə|n}});<ref name="Sun">Since the Sun, Ἥλιος in Greek, begins with a vowel (H is the long ē vowel in Greek), the final o in "apo" is omitted from the prefix. =The pronunciation "Ap-helion" is given in many dictionaries [https://www.oxforddictionaries.com/definition/english/aphelion] {{Webarchive|url=https://web.archive.org/web/20151222075218/https://www.oxforddictionaries.com/definition/english/aphelion|date=December 22, 2015}}, pronouncing the "p" and "h" in separate syllables. However, the pronunciation {{IPAc-en|ə|ˈ|f|iː|l|i|ə|n}} [http://www.dictionary.com/browse/aphelion] {{Webarchive|url=https://web.archive.org/web/20170729001850/http://www.dictionary.com/browse/aphelion|date=July 29, 2017}} is also common (''e.g.,'' ''McGraw Hill Dictionary of Scientific and Technical Terms,'' 5th edition, 1994, p. 114), since in late Greek, 'p' from ἀπό followed by the 'h' from ἥλιος becomes phi; thus, the Greek word is αφήλιον. (see, for example, Walker, John, ''A Key to the Classical Pronunciation of Greek, Latin, and Scripture Proper Names'', Townsend Young 1859 [https://play.google.com/store/books/details?id=LuF-9HKGbl4C&rdid=book-LuF-9HKGbl4C&rdot=1] {{Webarchive|url=https://web.archive.org/web/20190921013331/https://play.google.com/store/books/details?id=LuF-9HKGbl4C&rdid=book-LuF-9HKGbl4C&rdot=1|date=September 21, 2019}}, page 26.) Many [https://www.merriam-webster.com/dictionary/aphelion]  dictionaries give both pronunciations</ref> when discussing orbits around other stars the terms become ''periastron'' and ''apastron''.
* When discussing a satellite of [[Earth]], including the [[Moon]], the point of least distance is the ''perigee'' ({{IPAc-en|ˈ|p|ɛr|ᵻ|dʒ|i:}}), and of greatest distance, the ''apogee'' (from [[Ancient Greek]]: Γῆ (''Gē''), "land" or "earth").<ref>{{cite EB1911 |wstitle=Perigee |volume=21 |page=149}}</ref>
* For objects in [[lunar orbit]], the point of least distance are called the ''pericynthion'' ({{IPAc-en|ˌ|p|ɛr|ɪ|ˈ|s|ɪ|n|θ|i|ə|n}}) and the greatest distance the ''apocynthion'' ({{IPAc-en|ˌ|æ|p|ə|ˈ|s|ɪ|n|θ|i|ə|n}}). The terms ''perilune'' and ''apolune'', as well as ''periselene'' and ''aposelene'' are also used.<ref name="nasaglossary">{{cite web|url=https://solarsystem.nasa.gov/basics/glossary|title=Basics of Space Flight|publisher=NASA|access-date=May 30, 2017|archive-date=September 30, 2019|archive-url=https://web.archive.org/web/20190930063643/https://solarsystem.nasa.gov/basics/glossary/|url-status=live}}</ref> Since the Moon has no natural satellites this only applies to man-made objects.

===Etymology===
The words ''perihelion'' and ''aphelion'' were coined by [[Johannes Kepler]]<ref>Klein, Ernest, ''A Comprehensive Etymological Dictionary of the English Language'', Elsevier, Amsterdam, 1965.  ([https://archive.org/stream/AComprehensiveEtymologicalDictionaryOfTheEnglishLanguageByErnestKlein/A%20Comprehensive%20Etymological%20Dictionary%20of%20the%20English%20Language%20by%20Ernest%20Klein_djvu.txt Archived version])</ref> to describe the orbital motions of the planets around the Sun.
The words are formed from the prefixes ''peri-'' (Greek: ''περί'', near)  and ''apo-'' (Greek: ''ἀπό'', away from), affixed to the Greek word for the Sun, (''ἥλιος'', or ''hēlíos'').<ref name=Sun/>

Various related terms are used for other [[Celestial body|celestial objects]]. The suffixes ''-gee'', ''-helion'', ''-astron'' and ''-galacticon'' are frequently used in the astronomical literature when referring to the Earth, Sun, stars, and the [[Galactic Center]] respectively.  The suffix ''-jove'' is occasionally used for Jupiter, but ''-saturnium'' has very rarely been used in the last 50 years for Saturn. The ''-gee'' form is also used as a generic closest-approach-to "any planet" term—instead of applying it only to Earth.

During the [[Apollo program]], the terms ''pericynthion'' and ''apocynthion'' were used when referring to [[lunar orbit|orbiting the Moon]];  they reference Cynthia, an alternative name for the Greek Moon goddess [[Artemis]].<ref>{{cite web | title = Apollo 15 Mission Report | work = Glossary | url = https://history.nasa.gov/alsj/a15/a15mr-f.htm | access-date = October 16, 2009 | archive-date = March 19, 2010 | archive-url = https://web.archive.org/web/20100319081116/http://history.nasa.gov/alsj/a15/a15mr-f.htm | url-status = live }}</ref> More recently, during the [[Artemis program]], the terms ''perilune'' and ''apolune'' have been used.<ref>{{cite conference |author=R. Dendy |author2=D. Zeleznikar |author3=M. Zemba | title = NASA Lunar Exploration – Gateway's Power and Propulsion Element Communications Links | conference = 38th International Communications Satellite Systems Conference (ICSSC) | date = September 27, 2021 | location = Arlington, VA | url = https://ntrs.nasa.gov/citations/20210019019 | access-date = July 18, 2022 | archive-date = Mar 29, 2022 | archive-url=https://web.archive.org/web/20220329140256/https://ntrs.nasa.gov/citations/20210019019 | url-status = live }}</ref>

Regarding black holes, the term peribothron was first used in a 1976 paper by J. Frank and M. J. Rees,<ref>{{cite journal |author1=Frank, J. |author2=Rees, M.J. |title=Effects of massive black holes on dense stellar systems. |journal=MNRAS |volume=176 |pages=633–646 |date=September 1, 1976 |issue=6908 |doi=10.1093/mnras/176.3.633|bibcode=1976MNRAS.176..633F|doi-access=free }}</ref> who credit W. R. Stoeger for suggesting creating a term using the greek word for pit: "bothron".

The terms ''perimelasma'' and ''apomelasma'' (from a Greek root) were used by physicist and science-fiction author [[Geoffrey A. Landis]] in a story published in 1998,<ref name="Asimov's">[http://www.infinityplus.co.uk/stories/perimelasma.htm ''Perimelasma''] {{Webarchive|url=https://web.archive.org/web/20190225210759/http://www.infinityplus.co.uk/stories/perimelasma.htm |date=February 25, 2019 }}, by Geoffrey Landis, first published in ''[[Asimov's Science Fiction]]'', January 1998, republished at ''[[Infinity Plus]]''</ref> thus appearing before ''perinigricon'' and ''aponigricon'' (from Latin) in the scientific literature in 2002.<ref>{{cite journal |author=R. Schödel |author2=T. Ott |author3=R. Genzel |author4=R. Hofmann |author5=M. Lehnert |author6=A. Eckart |author7=N. Mouawad |author8=T. Alexander |author9=M. J. Reid |author10=R. Lenzen |author11=M. Hartung |author12=F. Lacombe |author13=D. Rouan |author14=E. Gendron |author15=G. Rousset |author16=A.-M. Lagrange |author17=W. Brandner |author18=N. Ageorges |author19=C. Lidman |author20=A. F. M. Moorwood |author21=J. Spyromilio |author22=N. Hubin |author23=K. M. Menten |title=A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way |journal=Nature |volume=419 |pages=694–696 |date=October 17, 2002 |issue=6908 |doi=10.1038/nature01121|arxiv=astro-ph/0210426 |bibcode=2002Natur.419..694S |pmid=12384690|s2cid=4302128 }}</ref>

===Terminology summary===
The suffixes shown below may be added to prefixes ''peri-'' or ''apo-'' to form unique names of apsides for the orbiting bodies of the indicated host/[[primary (astronomy)|(primary)]] system. However, only for the Earth, Moon and Sun systems are the unique suffixes commonly used. [[Exoplanet]] studies commonly use ''-astron'', but typically, for other host systems the generic suffix, ''-apsis'', is used instead.<ref>{{cite web |url=http://lasp.colorado.edu/home/maven/science/science-orbit/|title=MAVEN » Science Orbit|access-date=November 7, 2018|archive-date=November 8, 2018|archive-url=https://web.archive.org/web/20181108025706/http://lasp.colorado.edu/home/maven/science/science-orbit/|url-status=live}}</ref>{{Failed verification|date=January 2019| reason=Reference is simply one example of the use of -apsis for an orbit around Mars}}
<!-- Note that, due to some unfortunate citogenesis, sources must pre-date 2005-->
{|class="wikitable"
|+ Host objects in the Solar System with named/nameable apsides
|-
! [[Astronomical object|Astronomical<br/>host object]]
! Suffix
! Origin<br />of the name
|-
| [[Sun]]
| {{nobr|-helion}}
| [[Helios]]
|-
| [[Mercury (planet)|Mercury]]
| {{nobr|-hermion}}
| [[Hermes]]
|-
| [[Venus]]
| {{nobr|-cythe}}{{nobr|-cytherion}}
| [[Cytherean]]
|-
| [[Earth]]
| {{nobr|-gee}}
| [[Gaia (mythology)|Gaia]]
|-
| [[Moon]]
| {{nobr|-lune}}<ref name="nasaglossary"/><br />{{nobr|-cynthion}}<br />{{nobr|-selene}}<ref name="nasaglossary"/>
| [[Luna (goddess)|Luna]]<br />[[Artemis|Cynthia]]<br />[[Selene]]
|-
| [[Mars]]
| {{nobr|-areion}}
| [[Ares]]
|-
| [[Ceres (dwarf planet)|Ceres]]
| {{nobr|-demeter}}<ref>{{cite web|url=http://www.planetary.org/blogs/guest-blogs/marc-rayman/20181019-dawn-journal-11-years-in-space.html|title=Dawn Journal: 11 Years in Space|website=www.planetary.org|access-date=October 24, 2018|archive-date=October 24, 2018|archive-url=https://web.archive.org/web/20181024152511/http://www.planetary.org/blogs/guest-blogs/marc-rayman/20181019-dawn-journal-11-years-in-space.html|url-status=live}}</ref>
| [[Demeter]]
|-
| [[Jupiter]]
| {{nobr|-jove}}
| [[Zeus]]<br />[[Jupiter]]
|-
| [[Saturn]]
| {{nobr|-chron}}<ref name="nasaglossary"/><br />{{nobr|-kronos}}<br />{{nobr|-saturnium}}<br />{{nobr|-krone}}<ref>{{Cite journal|url=https://ui.adsabs.harvard.edu/abs/2009JGRA..114.3215C/abstract|title=Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver| first1=B.|last1=Cecconi| first2=L.|last2=Lamy| first3=P.|last3=Zarka| first4=R.|last4=Prangé| first5=W. S.|last5=Kurth| first6=P.|last6=Louarn|date=March 4, 2009|journal= Journal of Geophysical Research: Space Physics| volume=114| issue=A3| pages=A03215| via=ui.adsabs.harvard.edu| doi=10.1029/2008JA013830| bibcode=2009JGRA..114.3215C| access-date=December 9, 2019|archive-date=December 9, 2019|archive-url=https://web.archive.org/web/20191209095159/https://ui.adsabs.harvard.edu/abs/2009JGRA..114.3215C/abstract|url-status=live}}</ref>
| [[Cronus|Cronos]]<br />[[Saturn]]
|-
| [[Uranus]]
|{{nobr|-uranion}}
| [[Uranus]]
|-
| [[Neptune]]
|{{nobr|-poseideum}}<ref name="McKevitt Bulla Dixon Criscola 2021">Example of use: {{cite journal | last1=McKevitt | first1=James | last2=Bulla | first2=Sophie | last3=Dixon | first3=Tom | last4=Criscola | first4=Franco | last5=Parkinson-Swift | first5=Jonathan | last6=Bornberg | first6=Christina | last7=Singh | first7=Jaspreet | last8=Patel | first8=Kuren | last9=Laad | first9=Aryan | last10=Forder | first10=Ethan | last11=Ayin-Walsh | first11=Louis | last12=Beegadhur | first12=Shayne | last13=Wedde | first13=Paul | last14=Pappula | first14=Bharath Simha Reddy | last15=McDougall | first15=Thomas | last16=Foghis | first16=Madalin | last17=Kent | first17=Jack | last18=Morgan | first18=James | last19=Raj | first19=Utkarsh | last20=Heinreichsberger | first20=Carina | title=An L-class Multirole Observatory and Science Platform for Neptune|journal=2021 Global Space Exploration Conference Proceedings| date=18 June 2021 | arxiv=2106.09409 }}</ref><br/>{{nobr|-poseidion}}
| [[Poseidon]]
|}

{|class="wikitable"
|+Other host objects with named/nameable apsides
|-
! Astronomical<br /> host object
! Suffix
! Origin<br />of the name
|-
| [[Star]]
| -astron
| [[Ad astra (phrase)|Lat: astra]]; ''stars''
|-
| [[Galaxy]]
| -galacticon
| Gr: [[galaxy|galaxias; ''galaxy'']]
|-
| [[Barycenter]]
| -center<br />-focus<br />-apsis
|
|-
| [[Black hole]]
| -melasma<br />-bothron<br />-nigricon
| Gr: melos; ''black''<br />Gr: [[bothros]]; ''hole''<br />Lat: {{lang|la|niger}}; ''black''
|}