A formalminor-planet designation is, in its final form, a number–name combination given to a minor planet (asteroid,centaur,trans-Neptunian object anddwarf planet but notcomet). 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'sprovisional 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 theMinor Planet Center (MPC), a branch of theInternational Astronomical Union.[1]
Currently, a number is assigned only after the orbit has been secured by four well-observedoppositions.[2] For unusual objects, such asnear-Earth asteroids, numbering might already occur after three, maybe even only two, oppositions.[2] Among more thanhalf a million minor planets that received a number,[3] only about 20 thousand (or 4%) havereceived a name. In addition, approximately 700,000 minor planets havenot been numbered, as of November 2023.[3]
The convention forsatellites of minor planets, such as the formal designation (87) Sylvia I Romulus for the asteroid moonRomulus, is an extension of theRoman numeral convention that had been used, on and off, for the moons of the planets sinceGalileo's time. Comets are also managed by the MPC, but usea different cataloguing system.
A formal designation consists of two parts: a catalognumber, historically assigned in approximate order of discovery, and either aname, typically assigned by the discoverer, or, the minor planet'sprovisional designation.[1]
The permanent syntax is:
(number)Provisional designation(number) Name; with or without parenthesesFor example, the unnamed minor planet(388188) 2006 DP14 has its number always written in parentheses, while for named minor planets such as (274301) Wikipedia, the parentheses may be dropped as in274301 Wikipedia. Parentheses are now often omitted in prominent databases such as theJPL Small-Body Database.
Since minor-planet designations change over time, different versions may be used inastronomy journals. When the main-belt asteroid 274301 Wikipedia was discovered in August 2008, it was provisionally designated2008 QH24, before it received a number and was then written as(274301) 2008 QH24. On 27 January 2013, it was namedWikipedia after being published in theMinor Planet Circulars.[4][5]
According to the preference of the astronomer and publishing date of the journal, 274301 Wikipedia may be referred to as2008 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. SoPluto is rarely written as 134340 Pluto, and2002 TX300 is more commonly used than the longer version(55636) 2002 TX300.
By 1851 there were 15 known asteroids, all but one with their ownsymbol. The symbols grew increasingly complex as the number of objects grew, and, as they had to be drawn by hand, astronomers found some of them difficult. This difficulty was addressed byBenjamin Apthorp Gould in 1851, who suggested numbering asteroids in their order of discovery, and placing this number in a circle as the symbol for the asteroid, such as ④ for the fourth asteroid,Vesta. This practice was soon coupled with the name itself into an official number–name designation, "④ Vesta", as the number of minor planets increased. By the late 1850s, the circle had been simplified to parentheses, "(4)" and "(4) Vesta", which was easier to typeset. Other punctuation such as "4) Vesta" and "4, Vesta" was also used, but had more or less completely died out by 1949.[6]
The modern system of provisional designations first appeared in the journalAstronomische Nachrichten in 1892.[7][8]
The major exception to the convention that the number tracks the order of discovery or determination of orbit is the case of Pluto. Since Pluto was initially classified as a planet, it was not given a number until a 2006 redefinition of "planet" that excluded it. At that point, Pluto was given the formal designation (134340) Pluto.
