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]

Nowadays a number is assigned only after the orbit has been secured by 4 well-observed oppositions.[2] For unusual objects, such as near-Earth asteroids (NEAs), numbering might already occur after three, maybe even only two, oppositions.[2] Among the nearly half a million minor planets that received a number,[3] only about 20 thousand (or 4%) have received a name. In addition, more than 200,000 minor planets have not even been numbered.[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.


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).[1]

The permanent syntax is:

For example, the unnamed minor planet 14 has its number always written in parentheses, while for named minor planets such as (274301) Wikipedia, the parentheses may be dropped as in 274301 Wikipedia. Parentheses are now often omitted in prominent databases such as the SBDB. (Note: on English Wikipedia, named minor planets never use parentheses in their designations. However, redirects from parenthetical versions exist for most lower-numbered and well-known objects.)

Since minor planet designations change over time, different versions may be used in astronomy journals. When the main-belt asteroid 274301 Wikipedia was discovered in August 2008, it was provisionally designated 24, before it received a number and was then written as 24. On 27 January 2013, it was named Wikipedia after being published in the Minor Planet Circulars.[4][5]

According to the preference of the astronomer and publishing date of the journal, 274301 Wikipedia may be referred to as 2008 QH24, or simply as (274301). In practice, for any reasonably well-known object the number is mostly a catalogue entry, and the name or provisional designation is generally used in place of the formal designation. So Pluto is rarely written as 134340 Pluto, and 300 is more commonly used than the longer version 300.

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