Naming of moons

Every human language has its own word for the Earth's Moon, and these words are the ones normally used in astronomical contexts. However, a number of fanciful or mythological names for the Moon have been used in the context of astronomy (an even larger number of lunar epithets have been used in non-astronomical contexts). In the 17th century, the Moon was sometimes referred to as Proserpina. More recently, especially in science-fiction content, the Moon has been called by the Latin name Luna, presumably on the analogy of the Latin names of the planets, or by association with the adjectival form lunar, or a need to differentiate it from other moons that may be present in a fictional setting. In technical terminology, the word-stems seleno- (from Greek selēnē "moon") and cynthi- (from Cynthia, an epithet of the goddess Artemis) are sometimes used to refer to the Moon, as in selenography, selenology, and pericynthion.

The moons of Mars (Phobos and Deimos) were named by Asaph Hall in 1878, soon after he discovered them. They are named after the sons of the god Ares (the Greek equivalent of the Roman god Mars).

The Galilean moons of Jupiter (Io, Europa, Ganymede and Callisto) were named by Simon Marius soon after their discovery in 1610. However, by the late 19th century these names had fallen out of favor, and for a long time it was most common to refer to them in the astronomical literature simply as "Jupiter I", "Jupiter II", etc., or as "the first satellite of Jupiter", "Jupiter's second satellite", etc.

By the first decade of the 20th century, the names Io, Europa, Ganymede, and Callisto had once again recovered popularity, but the later-discovered moons, numbered, usually in Roman numerals V (5) through XII (12), remained unnamed.[3] By a popular though unofficial convention, Jupiter V, discovered in 1892, was given the name Amalthea,[4] first used by the French astronomer Camille Flammarion.[5]

The other irregular satellites (discovered 1904 to 1951) were, in the overwhelming majority of astronomical literature, simply left nameless. No names were proposed until Brian G. Marsden suggested a nomenclature for these satellites in 1955.[6] Although the 1955 names met with immediate acceptance in some quarters (e.g. in science fiction[7] and popular science articles[8]), they were still rarely if ever met in astronomical literature until the 1970s.[9]

Two other proposals for naming the satellites were made between 1955 and 1975, both by Soviet astronomers, E. I. Nesterovich (in 1962) and Yu. A. Karpenko (in 1973).[10][11] These met no particularly enthusiastic reception.

In 1975, following Charles Kowal's discovery of the satellite Jupiter XIII in 1974, the IAU Task Group for Outer Solar System Nomenclature granted names to satellites V-XIII, and provided for a formal naming process for future satellites to be discovered. Under the new process, Jupiter V continued as Amalthea, Jupiter XIII was named Leda in accordance with a suggestion of Kowal's, and all previous proposals for the seven satellites VI-XII were abandoned in favor of new names, in accordance with a scheme suggested by the German philologist Jürgen Blunck where prograde moons received names ending in 'a' and retrograde moons received names ending in 'e'.[12]

The new names met considerable protest from some quarters. Kowal, despite suggesting a name for Jupiter XIII, was of the opinion that Jupiter's irregular satellites should not be named at all.[13] Carl Sagan noted that the names chosen were extraordinarily obscure (a fact that Tobias Owen, chair of the Task Group, admitted was intentional in a response to Sagan[10]) and suggested his own names in 1976;[14] these preserved some of the names from the 1955 proposal. Karpenko had noted the same in his 1981 book "The Names of the Starry Sky", along with stating that the names chosen for retrograde moons, and therefore the "e" ending, were not always the ones for which it was the more common one.[15]

The proposals are summarized in the table below (data from Icarus unless specified otherwise[10][14]):

Current practice is that newly discovered moons of Jupiter must be named after lovers or descendants of the mythological Jupiter (Zeus). Blunck's scheme for the outer moons was retained, with the addition that names ending in 'o' could also be used for prograde moons. At the IAU General Assembly in July 2004,[2] the WGPSN allowed Jovian satellites to be named for Zeus' descendants in addition to his lovers and favorites which were the previous source of names, due to the large number of new Jovian satellites that had then recently been discovered. All of Jupiter's satellites from XXXIV (Euporie) on were named for descendants of Zeus, until Jupiter LIII (Dia), named after another one of his lovers.

In 1847, the seven then known moons of Saturn were named by John Herschel. Herschel named Saturn's two innermost moons (Mimas and Enceladus) after the mythological Greek Giants, and the outer five after the Titans (Titan, Iapetus) and Titanesses (Tethys, Dione, Rhea) of the same mythology. Until then, Titan was known as the "Huygenian (or Huyghenian) satellite of Saturn" and the other moons had Roman numeral designations in order of their distance from Saturn. Subsequent discoverers of Saturnian moons followed Herschel's scheme: Hyperion was discovered soon after in 1848, and the ninth moon, Phoebe, was named by its discoverer in 1899 soon after its discovery; they were named for a Titan and a Titaness respectively. The name of Janus was suggested by its discoverer, Audouin Dollfus.

Current IAU practice for newly discovered inner moons is to continue with Herschel's system, naming them after Titans or their descendants. However, the increasing number of moons that were being discovered in the 21st century caused the IAU to draw up a new scheme for the outer moons. At the IAU General Assembly in July 2004,[2] the WGPSN allowed satellites of Saturn to have names of giants and monsters in mythologies other than the Greco-Roman. Since the outer moons fall naturally into three groups, one group is named after Norse giants, one after Gallic giants, and one after Inuit giants. The only moon that fails to fit this scheme is the Greek-named Phoebe, which is in the Norse group.

The Roman numbering scheme of Uranus' moons was in a state of flux for a considerable time. Sir William Herschel thought he had discovered up to six moons and maybe even a ring. For nearly fifty years, Herschel's instrument was the only one the moons had been seen with.[17] In the 1840s, better instruments and a more favourable position of Uranus in the sky led to sporadic indications of satellites additional to Titania and Oberon. Publications hesitated between William Herschel's designations (where Titania and Oberon are Uranus II and IV) and William Lassell's (where they are sometimes I and II).[18] With the confirmation of Ariel and Umbriel, Lassell numbered the moons I through IV from Uranus outward, and this finally stuck.[19]

The first two Uranian moons, discovered in 1787, did not receive names until 1852, a year after two more moons had been discovered. The responsibility for naming was taken by John Herschel, son of the discoverer of Uranus. Herschel, instead of assigning names from Greek mythology, named the moons after magical spirits in English literature: the fairies Oberon and Titania from William Shakespeare's A Midsummer Night's Dream, and the sylphs Ariel and Umbriel from Alexander Pope's The Rape of the Lock (Ariel is also a sprite in Shakespeare's The Tempest). The reasoning was presumably that Uranus, as god of the sky and air, would be attended by spirits of the air.

Subsequent names, rather than continuing the "airy spirits" theme (only Puck and Mab continuing the trend), have focused on Herschel's source material. In 1949, the fifth moon, Miranda, was named by its discoverer, Gerard Kuiper, after a thoroughly mortal character in Shakespeare's The Tempest. Current IAU practice is to name moons after characters from Shakespeare's plays and The Rape of the Lock (although at present only Ariel, Umbriel, and Belinda have names drawn from the latter poem, all the rest being from Shakespeare). All the retrograde irregular moons are named after characters from one play, The Tempest; the only prograde irregular moon, Margaret, is named from Much Ado About Nothing.

The one known moon (at the time) of Neptune was not named for many decades. Although the name Triton was suggested in 1880 by Camille Flammarion, it did not come into general use until the mid 20th-century, and for many years was considered "unofficial". In the astronomical literature it was simply referred to as "the satellite of Neptune". Later, the second known moon, Nereid, was named by its discoverer in 1949, Gerard P. Kuiper, soon after its discovery.

Current IAU practice for newly discovered Neptunian moons is to accord with these first two choices by naming them after Greek sea deities.

For the "normal" irregular satellites, the general convention is to use names ending in "a" for prograde satellites, names ending in "e" for retrograde satellites, and names ending in "o" for exceptionally inclined satellites, exactly like the convention for the moons of Jupiter.[20]

Pluto and its five moons.[21]

The name of Pluto's moon Charon was suggested by James W. Christy, its discoverer, soon after its discovery.

The other four moons are named Hydra, Nix, Kerberos, and Styx.

Charon, Hydra, Nix, and Kerberos are all characters in Greek mythology, with ties to Hades (the Greek equivalent of Pluto). Charon ferries the dead across the River Acheron, Hydra guards the waters of the underworld, and Nix (a respelling of Nyx), mother of Charon, is the goddess of darkness and the night. Kerberos is a giant three-headed dog who guards the entrance to the underworld. The fifth moon is named for the river Styx that forms the boundary between the worlds of the living and the dead.

The name of Eris's moon Dysnomia was suggested by its discoverer Michael E. Brown, who also suggested the name of the dwarf planet. The name has two meanings: in mythology Dysnomia (lawlessness) is the daughter of Eris (chaos). However, the name is also an intentional reference to the actor Lucy Lawless who plays the character Xena. The background for this is that during the long period when Eris had no formal name, the name 'Xena' – originally Brown's nickname for his discovery – spread and became popular. When the name 'Eris' was chosen, Brown suggested Dysnomia (which until then had been referred to as Gabrielle) as a reference to this.[22] Hence, Dysnomia is the only moon which could be said to be named after an actor. The names Eris and Dysnomia were accepted by the IAU on 14 September 2006.

The name of Haumea and its moons were suggested by David L. Rabinowitz of Caltech and refer to the mother goddess and her daughters in Hawaiian mythology.

When the discoverers of Gonggong proposed choices for a public vote on its name, they chose figures that had associates that could provide a name for the satellite.[23] Xiangliu's name was chosen by its discovery team led by Csaba Kiss.[24]

Quaoar was named after the creator god of the Tongva tribe. Brown, who had co-discovered both Quaoar and its moon, left the name of the moon up to the Tongva. The Tongva chose the sky god Weywot, son of Quaoar.[25]

On 23 March 2009, Brown asked readers of his weekly column to suggest possible names for the satellite of Orcus which he had codiscovered, with the best one to be submitted to the International Astronomical Union (IAU) on 5 April.[26] The name Vanth, the winged Etruscan psychopomp who guides the souls of the dead to the underworld, was chosen from among a large pool of submissions. Vanth was the only suggestion that was purely Etruscan in origin. It was the most popular submission, first suggested by Sonya Taaffe.[27]

The Etruscan Vanth is frequently portrayed in the company of Charun (Charon), and so as the name of the moon of Orcus (nicknamed the "anti-Pluto" because resonance with Neptune keeps it on the opposite side of the Sun from Pluto), it is an allusion to the parallels between Orcus and Pluto. Brown quoted Taaffe as saying that if Vanth "accompanies dead souls from the moment of death to the underworld itself, then of course her face is turned always toward Orcus", a reference to the likely synchronous orbit of Vanth about Orcus.[27]

Unlike the planets and dwarf planets, relatively few moons orbiting asteroids have been named. Among them are the following:

The following names were adopted by informal processes preceding the assumption by the IAU of control over the assignment of satellite nomenclature in 1973.

Pre-IAU Names

Date	Namer	Name	Image	Planet/Number Designation	Discovery date	References/Notes
17th century
1614	Simon Marius	Io		Jupiter I	1610	Marius (Simon Mayr), in his book Mundus Iovialis anno M.DC.IX Detectus Ope Perspicilli Belgici, names the Galilean moons, and attributes the suggestion to Johannes Kepler.
		Europa		Jupiter II
		Ganymede		Jupiter III
		Callisto		Jupiter IV
19th century
1847	John Herschel	Mimas		Saturn I	1789	Herschel named the seven known satellites of Saturn in his book Results of Astronomical Observations made at the Cape of Good Hope, as reported by William Lassell, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 3, pp. 42–43 January 14, 1848
		Enceladus		Saturn II
		Tethys		Saturn III	1684
		Dione		Saturn IV
		Rhea		Saturn V	1672
		Titan		Saturn VI	1655
		Iapetus		Saturn VIII	1671
1848	William Lassell	Hyperion		Saturn VII	1847	Lassell, following John Herschel's suggested scheme, names Hyperion Discovery of a New Satellite of Saturn, Monthly Notices of the Royal Astronomical Society, Vol. 8, No. 9, pp. 195–197.
1852	John Herschel	Ariel		Uranus I	1851	Herschel named the four known satellites of Uranus in Astronomische Nachrichten, Vol. 34, No. 812, pp. 325/326, 21 June 1852 (communication dated 26 May 1852.)
		Umbriel		Uranus II
		Titania		Uranus III	1787
		Oberon		Uranus IV
1878	Asaph Hall	Phobos		Mars I	1877	Hall named his two newly discovered satellites of Mars Phobus and Deimus: Astronomische Nachrichten, Vol. 92, No. 2187, pp. 47/48 14 March 1878 (signed 7 February 1878). The names were subsequently amended to Phobos and Deimos.
		Deimos		Mars II
1880	Camille Flammarion	Triton		Neptune I	1846	Flammarion suggested the name Triton in his 1880 book Astronomie populaire, p. 591. The name was considered unofficial for decades afterwards.
c. 1893	Camille Flammarion	Amalthea		Jupiter V	1892	Flammarion suggested the name Amalthea in correspondence with discoverer E. E. Barnard. Barnard declined to propose any name, however, and Amalthea remained an unofficial name until its adoption by the IAU in 1975.
April 1899	William Henry Pickering	Phoebe		Saturn IX	1899	Pickering suggested the name Phoebe in A New Satellite of Saturn, Astrophysical Journal, Vol. 9, No. 4, pp. 274–276, April 1899, by his brother Edward C. Pickering.
20th century
April 1939	Seth Barnes Nicholson declines to name satellites of Jupiter he has discovered (Publications of the Astronomical Society of the Pacific, Vol. 51, No. 300, pp. 85–94, signed March 1939)
June 1949	Gerard P. Kuiper	Miranda		Uranus V	1948	Kuiper proposed the name Miranda in his report of the discovery, The Fifth Satellite of Uranus, Publications of the Astronomical Society of the Pacific, Vol. 61, No. 360, p. 129, June 1949.
August 1949	Gerard P. Kuiper	Nereid		Neptune II	1949	Kuiper proposed the name Nereid in his report of the discovery, The second satellite of Neptune, Publications of the Astronomical Society of the Pacific, Vol. 61, No. 361, pp. 175–176, August 1949.
1 February 1967	Audouin Dollfus	Janus		Saturn X	1966	Dollfus named Janus in a report of 1 February 1967 relating to its discovery (IAUC 1995: Saturn X (Janus)).

The following names were selected through a formal process controlled by the IAU. Only in a few cases is the person who chose the name identified.

For completeness, moons that were left unnamed upon their official numbering have also been included.

IAU Names - 21st century
Date	Name	Image	Planet/Number Designation	Discovery date	References/Notes
22 October 2002	Callirrhoe		Jupiter XVII	1999	IAUC 7998: Satellites of Jupiter
	Themisto		Jupiter XVIII	2000
	Megaclite		Jupiter XIX	2001	Spelled "Magaclite" in IAUC 7998; corrected 29 November 2002 in IAUC 8023: Satellites of Jupiter.
	Taygete		Jupiter XX		IAUC 7998: Satellites of Jupiter
	Chaldene		Jupiter XXI
	Harpalyke		Jupiter XXII	2000
	Kalyke		Jupiter XXIII	2001
	Iocaste		Jupiter XXIV
	Erinome		Jupiter XXV
	Isonoe		Jupiter XXVI
	Praxidike		Jupiter XXVII
8 August 2003	Autonoe		Jupiter XXVIII	2002	IAUC 8177: Satellites of Jupiter, Saturn, Uranus
	Thyone		Jupiter XXIX
	Hermippe		Jupiter XXX
	Aitne		Jupiter XXXI
	Eurydome		Jupiter XXXII
	Euanthe		Jupiter XXXIII
	Euporie		Jupiter XXXIV
	Orthosie		Jupiter XXXV
	Sponde		Jupiter XXXVI
	Kale		Jupiter XXXVII
	Pasithee		Jupiter XXXVIII
8 August 2003	Ymir		Saturn XIX	2000	IAUC 8177: Satellites of Jupiter, Saturn, Uranus
	Paaliaq		Saturn XX
	Tarvos		Saturn XXI
	Ijiraq		Saturn XXII
	Suttungr		Saturn XXIII		Spelled "Suttung" in IAUC 8177; emended on 21 January 2005 in IAUC 8471: Satellites of Saturn.
	Kiviuq		Saturn XXIV		IAUC 8177: Satellites of Jupiter, Saturn, Uranus
	Mundilfari		Saturn XXV
	Albiorix		Saturn XXVI
	Skathi		Saturn XXVII		Spelled "Skadi" in IAUC 8177; emended on 21 January 2005 in IAUC 8471: Satellites of Saturn.
	Erriapus		Saturn XXVIII		Spelled "Erriapo" in IAUC 8177; corrected on 14 December 2007 (USGS)
	Siarnaq		Saturn XXIX		IAUC 8177: Satellites of Jupiter, Saturn, Uranus
	Thrymr		Saturn XXX		Spelled "Thrym" in IAUC 8177; emended on 21 January 2005 in IAUC 8471: Satellites of Saturn.
8 August 2003	Trinculo		Uranus XXI	2002	IAUC 8177: Satellites of Jupiter, Saturn, Uranus
21 January 2005	Narvi		Saturn XXXI	2003	IAUC 8471: Satellites of Saturn
	Methone		Saturn XXXII	2004
	Pallene		Saturn XXXIII
	Polydeuces		Saturn XXXIV
30 March 2005	Hegemone		Jupiter XXXIX	2003	IAUC 8502: Satellites of Jupiter
	Mneme		Jupiter XL
	Aoede		Jupiter XLI
	Thelxinoe		Jupiter XLII
	Arche		Jupiter XLIII	2002
	Kallichore		Jupiter XLIV	2003
	Helike		Jupiter XLV
	Carpo		Jupiter XLVI
	Eukelade		Jupiter XLVII
	Cyllene		Jupiter XLVIII
29 December 2005	Francisco		Uranus XXII	2006	IAUC 8648: Satellites of Uranus
	Margaret		Uranus XXIII
	Ferdinand		Uranus XXIV
	Perdita		Uranus XXV
	Mab		Uranus XXVI
	Cupid		Uranus XXVII
21 June 2006	Nix		Pluto II	2005	IAUC 8723: Satellites of Pluto
	Hydra		Pluto III
17 July 2006	Daphnis		Saturn XXXV	2005	IAUC 8730: Saturn XXXV (Daphnis) = S/2005 S 1
13 September 2006	Dysnomia		Eris I	2005	IAUC 8747: (134340) Pluto, (136199) Eris, and (136199) Eris I (Dysnomia)
3 February 2007	Halimede		Neptune IX	2002	IAUC 8802: Satellites of Neptune
	Psamathe		Neptune X	2003
	Sao		Neptune XI	2002
	Laomedeia		Neptune XII
	Neso		Neptune XIII
5 April 2007	Kore		Jupiter XLIX	2003	IAUC 8826: Satellites of Jupiter and Saturn
5 April 2007	Aegir		Saturn XXXVI	2004	IAUC 8826: Satellites of Jupiter and Saturn
	Bebhionn		Saturn XXXVII
	Bergelmir		Saturn XXXVIII
	Bestla		Saturn XXXIX
	Farbauti		Saturn XL
	Fenrir		Saturn XLI
	Fornjot		Saturn XLII
	Hati		Saturn XLIII
	Hyrrokkin		Saturn XLIV		Spelled "Hyrokkin" in IAUC 8826; corrected on 31 July 2007 in IAUC 8860: Saturn XLIV (Hyrrokkin)
	Kari		Saturn XLV	2006	IAUC 8826: Satellites of Jupiter and Saturn
	Loge		Saturn XLVI
	Skoll		Saturn XLVII
	Surtur		Saturn XLVIII
20 September 2007	Anthe		Saturn XLIX	2007	IAUC 8873: Satellites of Saturn
	Jarnsaxa		Saturn L	2006
	Greip		Saturn LI
	Tarqeq		Saturn LII	2007
17 September 2008	Hiʻiaka		Haumea I	2005
	Namaka		Haumea II	2005
5 May 2009	Aegaeon		Saturn LIII	2009	IAUC 9041: New name/designation of satellite of Saturn (LIII), S/2008 S 1. (subscription only)
4 October 2009	Weywot		Quaoar I	2006	MPC 67220: New Names of Minor Planets
11 November 2009	Herse		Jupiter L	2003	IAUC 9094: Designation and name assigned to S/2003 J 17 (the 50th satellite of Jupiter to be so designated and named): Jupiter L (Herse). (subscription only)
30 March 2010	Vanth		Orcus I	2005	MPC 69496: New Names of Minor Planets
18 February 2011	Actaea		Salacia I	2006	MPC 73984: New Names of Minor Planets
2 July 2013	Kerberos		Pluto IV	2011	IAU1303 News Release
	Styx		Pluto V	2012
16 January 2014	Ilmarë		Varda I	2009	MPC 86715: New Names of Minor Planets
7 March 2015	(unnamed)		Jupiter LI	2010	CBET (Central Bureau Electronic Telegram) 4075: 20150307: Satellites of Jupiter, March 7, 2015 (subscription only)
			Jupiter LII	2010
	Dia		Jupiter LIII	2000
9 June 2017 (numbered) 19 August 2019 (named)	(unnamed)		Jupiter LIV	2016	MPC 105280: Numbering of Natural Satellites Names Approved for Five Jovian Satellites
			Jupiter LV	2003
			Jupiter LVI	2011
	Eirene		Jupiter LVII	2003
	Philophrosyne		Jupiter LVIII	2003
	(unnamed)		Jupiter LIX	2017
5 October 2017 (numbered) 19 August 2019 (named)	Eupheme		Jupiter LX	2003	MPC 106505: Numbering of a Natural Satellite Names Approved for Five Jovian Satellites
25 September 2018 (numbered) 3 October 2018 (named)	(unnamed)		Jupiter LXI	2003	MPC 111804: Numbering of Natural Satellites Name Approved for Jovian Satellite: Valetudo Names Approved for Five Jovian Satellites Name Approved for Neptunian Satellite: Hippocamp
	Valetudo		Jupiter LXII	2016
25 September 2018 (numbered) 19 August 2019 (named)	(unnamed)		Jupiter LXIII	2017
			Jupiter LXIV
	Pandia		Jupiter LXV
	(unnamed)		Jupiter LXVI
			Jupiter LXVII
			Jupiter LXVIII
			Jupiter LXIX
			Jupiter LXX
	Ersa		Jupiter LXXI	2018
	(unnamed)		Jupiter LXXII	2011
25 September 2018 (numbered) 20 February 2019 (named)	Hippocamp		Neptune XIV	2013
5 February 2020	Xiangliu		Gonggong I	2016	MPC 121135: New Names of Minor Planets
1 June 2021 (numbered) 24 August 2022 (named)	Gridr		Saturn LIV	2019	MPC 132212: Numbering of a Natural Satellite Names Approved for 10 Small Satellites of Saturn
10 August 2021 (numbered) 24 August 2022 (named)	Angrboda		Saturn LV		MPC 133821: Numbering of Natural Satellites Names Approved for 10 Small Satellites of Saturn
	Skrymir		Saturn LVI
	Gerd		Saturn LVII
	(unnamed)		Saturn LVIII
	Eggther		Saturn LIX
	(unnamed)		Saturn LX
	Beli		Saturn LXI
	Gunnlod		Saturn LXII
	Thiazzi		Saturn LXIII
	(unnamed)		Saturn LXIV
	Alvaldi		Saturn LXV
	Geirrod		Saturn LXVI