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New- And Old-Style Minor Planet Designations

This document describes the formats for both new-style provisionaldesignations for minor planets (as used from the start of 1925) andthe old-style designations (as used prior to 1925).

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New-Style Provisional Designations

The Minor Planet Center assigns new provisonaldesignations when it is in possession of at least two nights of observationsof an object that cannot be identified immediately with some alreadydesignated object.

The standard designation consists of thefollowing parts, all of which are related to the date of discoveryof the object: a 4-digit number indicating the year; a space; a letterto show the half-month; another letter to show the orderwithin the half-month; and an optional number to indicate the numberof times the second letter has been repeated in that half-month period.

The half-month of discovery is indicated using the following scheme:

  Letter     Dates             Letter      Dates    A      Jan. 1-15             B       Jan. 16-31    C      Feb. 1-15             D       Feb. 16-29    E      Mar. 1-15             F       Mar. 16-31    G      Apr. 1-15             H       Apr. 16-30    J      May  1-15             K       May  16-31    L      June 1-15             M       June 16-30    N      July 1-15             O       July 16-31    P      Aug. 1-15             Q       Aug. 16-31    R      Sept.1-15             S       Sept.16-30    T      Oct. 1-15             U       Oct. 16-31    V      Nov. 1-15             W       Nov. 16-30    X      Dec. 1-15             Y       Dec. 16-31             I is omitted and Z is unused

The order within the month is indicated using letters as follows:

    A = 1st     B = 2nd     C = 3rd     D = 4th     E = 5th    F = 6th     G = 7th     H = 8th     J = 9th     K = 10th    L = 11th    M = 12th    N = 13th    O = 14th    P = 15th    Q = 16th    R = 17th    S = 18th    T = 19th    U = 20th    V = 21st    W = 22nd    X = 23rd    Y = 24th    Z = 25th                        I is omitted

If there are more than 25 discoveries in any one half-month period, thesecond letter is recycled and a numeral `1' is added to the end of thedesignation. If more than 50 discoveries, the second-letter is againrecycled, with a numeral `2' appended after the second letter.Discoveries 76-100 have numeral `3' added, numbers 101-125 numeral `4', etc.When possible, these additional numbers should be indicated using subscriptcharacters.

Thus the order of assignment of designations in a particular half-monthperiod is as follows:1995 SA, 1995 SB, ..., 1995 SY, 1995 SZ,1995 SA1, ...,1995 SZ1, 1995 SA2, ..., 1995 SZ9,1995 SA10, etc.

This scheme has been extended to pre-1925 discoveries--such designationsare indicated by the replacement of the initial digit of the year bythe letter `A'. Thus,A904 OA is the first object designated that wasdiscovered in the second half of July 1904.

Survey Designations

Four special surveys, undertaken between 1960 and 1977, have designationsthat consist of a number (identifing the order within that survey), a spaceand a survey identifier. The survey identifiers are as follows:

   Survey                         Identifier   Palomar-Leiden (1960)             P-L   First Trojan Survey (1971)        T-1   Second Trojan Survey (1973)       T-2   Third Trojan Survey (1977)        T-3

Example designations are2040 P-L, 3138 T-1, 1010 T-2 and 4101 T-3.

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Old-Style Provisional Designations

In the first half of the 19th century, minor planets were referred tosimply by name. The assignment of ordinal numbers, ostensibly in orderof discovery, was introduced in the early 1850s. Initially, new numberswere assigned by the editors of theAstronomisches Nachrichten (AN)immediately upon receipt of the announcement of a new discoveryfrom an observer.

In 1892 a system of provisional designations was introduced by theAN.A definitive number was subsequently given by the editors of theBerliner Astronomisches Jahrbuch to those objects for which reasonableorbital elements had been computed. The provisional designation schemeconsisted initially of a year and a single letter: e.g., 1892 A, 1892 B, etc.,omitting the letter `I'.

In 1893, the 25 available letters proved to be insufficient and a seriesof double letter designations was introduced: e.g. 1893 AA, 1893 AB, etc.,omitting the letter `I'. The sequence of double letters was not restartedanew each year, so 1894 AQ followed 1893 AP (for example). In 1916, theletters reached ZZ and, rather than starting a series of triple-letterdesignations, the double-letter series was restarted with 1916 AA.

[NOTE: In old publications, it is common to see `J' as the omitted letterinstead of `I'--the sequence going 1892 H, 1892 I, 1892 K, etc. Modern usagewould consider 1892 I to be the same as 1892 J and it is this latterdesignation which is recorded.]

In the double-letter scheme it was not generally possible to insert newdiscoveries into the sequence once designations had been assigned ina subsquent year. The scheme used to get round thisproblem was rather clumsy and used a designation consisting of the yearand a lower-case letter in a manner similarto the old provisional-designation scheme for comets. For example,1915 a (note that there is a space between the year and the letter inorder to distinguish this designation from the old-style comet designation1915a), 1917 b. In 1914 designations of the form year plus Greek letterwere used in addition.

During World War I the active observers at Simëis in theCrimea, deprived of official designations for their discoveries,assigned their own. The designations came in two forms: year + Greekcapital sigma + letter(s); Greek capital sigma + number.The Greek capital sigma is indicated as SIGMA.

Other designation schemes used at Simëis and other observatoriesarelisted elsewhere.

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To summarise, the following forms of input are valid:

• Year + Single Letter:1892 A
• Year + Double Letter:1914 VV
• Year + letter:1913 a
• Year + Greek letter:1914 gamma
• Year + SIGMA + letter:1915 SIGMA r, 1916 SIGMA ci
• SIGMA + number:SIGMA 27

For the purposes of searching,SIGMA may be abbreviated toSIG and the year is optional on theyear+SIGMA+letter designations(i.e.,SIGMA ci is a shorthand form for1916 SIGMA ci).