Minor-planet designation

Formal minor planet designations are number–name combinations overseen by the Minor Planet Center, a branch of the IAU. They are used for dwarf planets and small Solar System bodies such as asteroids, but not comets. They are assigned to a body once its orbit is secured, and are unrelated to provisional designations, which are automatically assigned when an object is discovered.

A formal designation consists of two parts: a catalog number, historically assigned in approximate order of discovery, and either a name, typically assigned by the discoverer, or, the minor planet's provisional designation (see details in § Syntax).:

Nowadays a number is assigned only after the orbit has been secured by 4 well-observed oppositions. For unusual objects, such as near-Earth asteroids (NEAs), numbering might already occur after three, maybe even only two, oppositions. Among the nearly half a million minor planets that received a number, only about 20 thousand (or 4%) have received a name. In addition, more than 200,000 minor planets have not even been numbered.

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 Minor Planet Center, but use a different cataloguing system.

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