Naming of natural satellites

From Academic Kids

The naming of natural satellites has been the responsibility of the IAU's committee for Planetary System Nomenclature since 1973. That committee is known today as the Working Group for Planetary System Nomenclature (WGPSN).

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 decades or even centuries after their discovery.



The moons of Mars (Phobos and Deimos) were named by Asaph Hall in 1878, soon after he discovered them.


See also Jupiter's natural satellites

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 (until the mid 20th century) 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.

The moons of Jupiter discovered between 1904 and 1951 were not named until 1975, being known until then simply by their Roman numeral designations (Jupiter VI through Jupiter XII). The moon Amalthea (Jupiter V), discovered in 1892, was unofficially named but its name was also not made official until 1975. Since the names of the Galilean satellites themselves had fallen out of favor, it is perhaps not unusual that the discoverers of the new smaller satellites did not see fit to name them either.

Most likely Charles Kowal's discovery of Leda (Jupiter XIII) in 1974 finally prompted the International Astronomical Union to establish a formal nomenclature process.

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, and so the IAU agreed to permit moons to be named after Zeus's descendants as well.


See also Saturn's natural satellites

The seven known moons (at the time) of Saturn were named in 1847 by John Herschel. Herschel's system was to name Saturn's moons after the mythological Greek Titans. 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; the ninth moon, Phoebe was named by its discoverer in 1899 soon after its discovery; and 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, which are named after giants in the mythologies of other cultures. 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.


See also Uranus' natural satellites

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 broke with tradition: instead of assigning names from Greek mythology, he named the moons after magical spirits in English literature: Oberon and Titania from William Shakespeare's A Midsummer Night's Dream, and Ariel and Umbriel from Alexander Pope's The Rape of the Lock.

Subsequent naming choices have accorded with Herschel's choices. In 1949, the fifth moon, Miranda, was named by its discoverer after a 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 the names from Shakespeare far outnumber those from Pope). At present, the outermost moons are all named after characters from one play, The Tempest.


See also Neptune's natural satellites

The one known moon (at the time) of Neptune was not named for many decades. Although the name Triton was suggested in 1880, it did not come into general use until the mid 20th-century. 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 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.


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

Recent developments

As of the IAU General Assembly in July 2004 [1] (, the WGPSN:

  • named 34 satellites of Jupiter and Saturn and one Uranus satellite, bringing the total number of known planetary satellites to 101, with over two dozen more awaiting recovery and naming;
  • suggested it may become advisable to not name small satellites (current CCD technology makes it possible to discover satellites as small as 1 km);
  • allowed Jovian satellites to be named for Zeus' descendants in addition to his lovers and favorites which were the previous source of names;
  • allowed satellites of Saturn to have names of giants and monsters in mythologies other than the Greco-Roman, including (so far) Gallic, Inuit and Norse.

See also


  • John Herschel names the seven known satellites of Saturn: MNRAS 8 (1848) 42 ( in his 1847 publication of Results of Astronomical Observations made at the Cape of Good Hope)
  • John Herschel names the four known satellites of Uranus: AN, 34 (1852) 325/326 ( in 1852
  • Asaph Hall names his two newly-discovered satellites of Mars: AN, 92 (1878) 47/48 ( in 1878.
  • Seth Barnes Nicholson declines to name satellites of Jupiter he has discovered: PASP 51 (1939) 93 (

Academic Kids Menu

  • Art and Cultures
    • Art (
    • Architecture (
    • Cultures (
    • Music (
    • Musical Instruments (
  • Biographies (
  • Clipart (
  • Geography (
    • Countries of the World (
    • Maps (
    • Flags (
    • Continents (
  • History (
    • Ancient Civilizations (
    • Industrial Revolution (
    • Middle Ages (
    • Prehistory (
    • Renaissance (
    • Timelines (
    • United States (
    • Wars (
    • World History (
  • Human Body (
  • Mathematics (
  • Reference (
  • Science (
    • Animals (
    • Aviation (
    • Dinosaurs (
    • Earth (
    • Inventions (
    • Physical Science (
    • Plants (
    • Scientists (
  • Social Studies (
    • Anthropology (
    • Economics (
    • Government (
    • Religion (
    • Holidays (
  • Space and Astronomy
    • Solar System (
    • Planets (
  • Sports (
  • Timelines (
  • Weather (
  • US States (


  • Home Page (
  • Contact Us (

  • Clip Art (
Personal tools