Provisional designation

Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calculated. In the case of more than 700,000 minor planets, approximately a third remains provisionally designated, as hundreds of thousands have been discovered in the last two decades.

The current system of provisional designation of minor planets (asteroids, centaurs and trans-Neptunian objects) has been in place since 1925, and superseded several previous conventions, each of which was rendered obsolete by the increasing numbers of minor planet discoveries. A modern or new-style provisional designation consists of the year of discovery, followed by two letters and, optionally, a suffixed number.

For example, the provisional designation 2016 EK156 stands for the 3910th body identified during 1–15 March 2016:

Minor planets discovered during the Palomar–Leiden survey including three subsequent Trojan-campaigns, which altogether discovered more than 4,000 asteroids and Jupiter trojans between 1960 and 1977, have a custom designations that consist of a number (order in the survey) followed by a space and one of the following identifiers:

For example, the asteroid 6344 P-L is the 6344th minor planet in the original Palomar-Leiden survey, while the asteroid 4835 T-1 was discovered during the first Trojan-campaign. The majority of these bodies have since been assigned a number and many are already named.

The first four minor planets were discovered in the early 19th century, after which there was a lengthy gap before the discovery of the fifth. Astronomers initially had no reason to believe that there would be countless thousands of minor planets, and strove to assign a symbol to each new discovery, in the tradition of the symbols used for the major planets. For example, 1 Ceres was assigned a stylized sickle (⚳) 2 Pallas a lozenge with a crossed handle (⚴) 3 Juno a Venus mirror crowned by a star (, later became a star with a crossed handle, ⚵) and 4 Vesta a sacred fire altar ().

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