"Official" Astronomical Names
Astronomy is an old science. Its nomenclature is often derived from tradition and history (especially Greek/Roman mythology) rather than from what might today seem more sensible. The names of the objects in the solar system are particularly so. The International Astronomical Union (IAU) is officially in charge of assigning astronomical names and it is very sensitive to astronomical tradition.
PlanetsPlanets in our solar system get a name as soon as possible. There aren't likely to be any new ones until we see them around another star. Who knows what convention will be used then.
SatellitesSatellites of the planets are assigned a provisional designation (indicating year of discovery) by the Central Bureau for Astronomical Telegrams (CBAT) upon satisfactory demonstration of the existence of a new object. For example, when Voyager 2 found a bunch of new moons in its 1989 Neptune encounter, they were named S/1989 N 1, S/1989 N 2, etc. When the orbit of the new object is accurate enough to allow the prediction of future positions with reasonable precision, the object is assigned a Roman numeral (e.g. Neptune VIII), and the object may receive a name (e.g. Proteus). (The name is suggested by the discoverer(s), but following tradition is strongly encouraged; so if you want to name a planet or satellite, get out your books of mythology. Note also that the moons of Uranus are a special case -- they get literary instead of mythological names.) This process is currently underway for the new Uranian moons discovered recently.
AsteroidsAsteroids are at first given provisional numbers by the Minor Planet Center (MPC) indicating the year and month of discovery. The provisional designation is the year, followed by a letter that indicates the half-month during which the discovery occurred, followed by a letter that indicates sequence within the half-month. So 1982 DB was reported in the last half of February 1982, and it's the second asteroid discovered during that period. When their orbits are understood well enough that their future position can be predicted well, they are given a permanent number and name. "243 Ida" is the 243rd asteroid to be numbered (not necessarily the 243rd discovered). The name is again chosen by the discoverer, but there's much more latitude; asteroids can be named after a living person, or almost anything else (e.g. "2309 Mr. Spock"; several have been named for popular musicians). Final decisions are made by an IAU committee. For more information see "How Are Minor Planets Named?".
CometsIn the past, Comets were first given a provisional designation, consisting of the year and a lowercase letter indicating the order of discovery in the year (e.g., 1994a was the first comet discovered or recovered in 1994, 1994b the second, etc.). The name was also assigned at an early stage. Up to three (preferably independent) discoverers may have been attached to the comet. Some time later, the comets that had passed perihelion in a given year were assigned Roman numeral designations indicating the order of perihelion passage within the year. The Roman numeral designations for 1993 and 1994 are given in the Jan. 1995 batch of Minor Planet Circulars (MPCs).
Note that whole comet designation system was revamped starting in the beginning of 1995. The main points of the new scheme are:
Some examples of new comet designations:
C/1995 Q2 (Hartley-Drinkwater) P/1994 P1-A (Machholz 2) Fragment A of a split comet P/1996 A1 (Jedicke) New periodic comet 125P Routine observation of periodic cometHere is a copy of the official IAU resolution.
Surface FeaturesLandscape features on planets, satellites, and asteroids follow complicated conventions set by the IAU Nomenclature Committee. Among these are the restriction that a planetary feature may not bear the name of a living person or of a political or religious figure from the last 200 years. A good explanation of this may be found in *Planetary Mapping*, edited by Greeley & Batson Cambridge U.Press, 1990. (Gee, it's handy having Phil Stooke's Planetary Map FAQ lying around on my disk!)
[ Adapted from usenet postings by Bill Higgins and Gareth Williams but any errors are mine. ]
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Bill Arnett; last updated: 2000 Jan 14