Prior to its formation, the names of satellites have had varying histories. The choice of names is often determined by a satellite's discoverer; however, historically some satellites were not given names for many years after their discovery; for instance, Titan was discovered by Huygens in 1655, but was not named until 1847, almost two centuries later.
Before the IAU assumed responsibility for astronomical nomenclature, only twenty-five satellites had been given names that were in wide use and are still used. Since then, names have been given to 123 additional satellites: 44 satellites of Jupiter, 42 of Saturn, 22 of Uranus, 11 of Neptune, 3 of Pluto, and 1 of Eris. The number will continue to rise as current satellite discoveries are documented and new satellites are discovered.
At the IAU General Assembly in July 2004, the WGPSN suggested it may become advisable to not name small satellites, as CCD technology makes it possible to discover satellites as small as 1 km in diameter. To date, however, names have been applied to all moons discovered, regardless of size.
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. By a popular though unofficial convention, Jupiter V, discovered in 1892, was given the name Amalthea, first used by the French astronomer Camille Flammarion.
The other moons (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. Although the 1955 names met with immediate acceptance in some quarters (e.g. in science fiction and popular science articles), they were still rarely if ever met in astronomical literature until the 1970s.
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). These met with no very 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.
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. 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) and suggested his own names in 1976; these preserved some of the names from the 1955 proposal.
The proposals are summarized in the table below (data from Icarus)
|Number||1955 ProposalBrian Marsden||1962 ProposalE. I. Nesterovich||1973 ProposalYu. A. Karpenko||1975 ProposalIAU Committee|| 1976 Proposal|
|Jupiter VI||Hestia||Atlas||Adrastea||Himalia||Maia||Jupiter VII||Hera||Hercules||Ida||Elara||Hera||Jupiter VIII||Poseidon||Persephone||Helen||Pasiphaë||Alcmene||Jupiter IX||Hades||Cerberus||Leda||Sinope||Leto||Jupiter X||Demeter||Prometheus||Latona||Lysithea||Demeter||Jupiter XI||Pan||Dedalus||Danae||Carme||Semele||Jupiter XII||Adrastea||Hephaestus||Semele||Ananke||Danae|
Current practice is that newly discovered moons of Jupiter must be named after lovers of the mythological Jupiter (Zeus). A convention has also emerged among the outer moons, whereby prograde moons are given names ending in 'a' or 'o', and retrograde moons receive names ending in 'e'. In 2004, with new Jovian moons continuing to be discovered, these rules were found to be excessively restrictive. At the IAU General Assembly in July 2004, the WGPSN therefore allowed Jovian satellites to be named for Zeus' descendants in addition to his lovers and favorites which were the previous source of names. All of Jupiter's satellites from XXXIV (Euporie) on are named for daughters of Zeus.
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, 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 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). At first, the outermost moons were all named after characters from one play, The Tempest; but with Margaret being named from Much Ado About Nothing that trend has ended.
Current IAU practice for newly discovered Neptunian moons is to accord with these first two choices by naming them after Greek sea deities.
Charon, Hydra and Nix are all characters in Greek Mythology, with ties to Hades (the Greek equivalent of Pluto). Charon ferried the dead across the River Acheron, Hydra guarded the waters of the underworld, and Nix, mother of Charon, was the goddess of darkness and the night.
|Name of moon||Name of primary||Roman numeral|
Roman numerals are usually not assigned to satellites until they are named, so many satellites that have been discovered but only have provisional designations do not have Roman numerals assigned to them. (An exception is Saturn's moon Helene, which received the Roman numberal XII in 1982, but was not named until 1988.) Since the International Astronomical Union began assigning names to all satellites in 1975, the use of Roman numeral designations has diminished, and some are very rarely used; Phobos and Deimos are rarely referred to as Mars I and Mars II, and the Moon is never referred to as "Earth I".
|Date||Namer||Name||Image||Planet/Number Designation||Discovery date||References/Notes|
|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.|
|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)|
|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.)|
|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.|
|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.|
|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)).|
|Date||Name||Image||Planet/Number Designation||Discovery date||References/Notes|
|7 October 1975||Himalia||Jupiter VI||1904||IAUC 2846: Satellites of Jupiter Also confirmed the name Amalthea.|
|1982||Epimetheus||Saturn XI||1980||Transactions of the International Astronomical Union, Vol. XVIIIA, 1982. Mentioned in IAUC 3872. Also confirmed the name Janus.|
|30 September 1983||Thebe||Jupiter XIV||1979||IAUC 3872: Satellites of Jupiter and Saturn|
|30 September 1983||Atlas||Saturn XV||1980||IAUC 3872: Satellites of Jupiter and Saturn|
|3 January 1986||Prometheus||Saturn XVI||IAUC 4157: Satellites of Saturn and Pluto|
|3 January 1986||Charon||Pluto I||1978||IAUC 4157: Satellites of Saturn and Pluto James W. Christy announced the name Charon shortly after his discovery of the satellite in 1978, but the name remained unofficial until its adoption by the IAU in 1986.|
|8 June 1988||Helene||Saturn XII||1980||IAUC 4609: Satellites of Saturn and Uranus|
|8 June 1988||Cordelia||Uranus VI||1986||IAUC 4609: Satellites of Saturn and Uranus|
|16 September 1991||Pan||Saturn XVIII||1990||IAUC 5347: Satellites of Saturn and Neptune|
|16 September 1991||Naiad||Neptune III||1989||IAUC 5347: Satellites of Saturn and Neptune|
|30 April 1998||Caliban||Uranus XVI||1997||B. J. Gladman, P. D. Nicholson, J. A. Burns, J. J. Kavelaars, B. G. Marsden, G. V. Williams and W. B. Offutt propose the names Caliban and Sycorax in their account of the discovery: Discovery of two distant irregular moons of Uranus, Nature, Vol. 392, pp. 897–899 (The IAU appears to have adopted these names prior to those reported in IAUC 7479.)|
|21 August 2000||Prospero||Uranus XVIII||1999||IAUC 7479: Satellites of Uranus|
|22 October 2002||Callirrhoë||Jupiter XVII||1999||IAUC 7998: Satellites of Jupiter|
|Megaclite||Jupiter XIX||2001||Spelled "Magaclite" in IAUC 7998; corrected 29 November 2002 in IAUC 8023: Satellites of Jupiter|
|Taÿgete||Jupiter XX||IAUC 7998: Satellites of Jupiter|
|8 August 2003||Autonoë||Jupiter XXVIII||2002||IAUC 8177: Satellites of Jupiter, Saturn, Uranus|
|8 August 2003||Ymir||Saturn XIX||2000||IAUC 8177: Satellites of Jupiter, Saturn, Uranus|
|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|
|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|
|30 March 2005||Hegemone||Jupiter XXXIX||2003||IAUC 8502: Satellites of Jupiter|
|29 December 2005||Francisco||Uranus XXII||2006||IAUC 8648: Satellites of Uranus|
|21 June 2006||Nix||Pluto II||2005||IAUC 8723: Satellites of Pluto|
|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 (subscription-only)|
|5 April 2007||Kore||Jupiter XLIX||2003||IAUC 8826: Satellites of Jupiter and Saturn (subscription-only)|
|5 April 2007||Ægir||Saturn XXXVI||2004||IAUC 8826: Satellites of Jupiter and Saturn (subscription-only)|
|Hyrrokkin||Saturn XLIV||Spelled "Hyrokkin" in IAUC 8826; corrected on 31 July 2007 in IAUC 8860: Saturn XLIV (Hyrrokkin) (subscription-only)|
|Kari||Saturn XLV||2006||IAUC 8826: Satellites of Jupiter and Saturn (subscription-only)|
|18 July 2007||Anthe||Saturn XLIX||2007||IAUC 8857: Saturn XLIX (Anthe) (subscription-only)|
|20 September 2007||Jarnsaxa||Saturn L||2006||IAUC 8873: Satellites of Saturn (subscription-only)|
|17 September 2008||Hiʻiaka||Haumea I||2005|