Minor-planet designation

A formal minor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid, centaur, trans-Neptunian object and dwarf planet but not comet). Such designation always features a leading number (catalog or IAU number) assigned to a body once its orbital path is sufficiently secured (so-called "numbering"). The formal designation is based on the minor planet's provisional designation, which was previously assigned automatically when it had been observed for the first time. Later on, the provisional part of the formal designation may be replaced with a name (so-called "naming"). Both formal and provisional designations are overseen by the Minor Planet Center (MPC), a branch of the International Astronomical Union.^[1]

Currently, a number is assigned only after the orbit has been secured by four well-observed oppositions.^[2] For unusual objects, such as near-Earth asteroids, numbering might already occur after three, maybe even only two, oppositions.^[2] Among more than half a million minor planets that received a number,^[3] only about 20 thousand (or 4%) have received a name. In addition, approximately 700,000 minor planets have not been numbered, as of November 2023.^[3]

The convention for satellites of minor planets, such as the formal designation (87) Sylvia I Romulus for the asteroid moon Romulus, is an extension of the Roman numeral convention that had been used, on and off, for the moons of the planets since Galileo's time. Comets are also managed by the MPC, but use a different cataloguing system.