as "D/", "C/", and "P/", used for comets. The designation "R/" is used for planetary rings. These designations are sometimes written like "S/2003 S1", dropping the second space. The letter following the category and year identifies the planet (Jupiter, Saturn, Uranus, Neptune; although no occurrence of the other planets is expected, Mars and Mercury are disambiguated through the use of Hermes for the latter). Pluto was designated by P prior to its recategorization as a dwarf planet. When the object is found around a minor planet, the identifier used is the latter's number in parentheses. Thus, Dactyl, the moon of 243 Ida, was at first designated "S/1993 (243) 1". Once confirmed and named, it became (243) Ida I Dactyl. Similarly, the fourth satellite of Pluto, Kerberos, discovered after Pluto was categorized as a dwarf planet and assigned a minor planet number, was designated S/2011 (134340) 1 rather than S/2011 P 1, though the New Horizons team, who maintained that dwarf planets were planets, used the latter. H = Mercury (Hermes) V = Venus E = Earth M = Mars J = Jupiter S = Saturn U = Uranus N = Neptune Note: The assignation of "H" for Mercury is specified by the USGS Gazetteer of Planetary Nomenclature; since they usually follow IAU guidelines closely, this is very likely the IAU convention, but confirmation is needed: there have been no moons found to be orbiting Mercury as of yet. After a few months or years, when a newly discovered satellite's existence has been confirmed and its orbit computed, a permanent name is chosen, which replaces the "S/" provisional designation. However, in the past, some satellites remained unnamed for surprisingly long periods after their discovery. Timeline The timeline only includes moons of the planets and the more likely dwarf planets. (no moons), , , , , , , , and (no moons) are generally agreed among astronomers to be dwarf planets. and are more controversial. Pre-IAU names The following names were adopted by informal processes preceding the assumption by the IAU of control over the assignment of satellite nomenclature in 1973. IAU names 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. 20th century 21st century For completeness, moons that were left unnamed upon their official numbering have also been included. Other references Astronomical Headlines