Minor planets were initially identified by a female classical name and abbreviated with an associated graphic symbol, as was (and still is) the practice for the major planets. By 1851 there were fifteen known asteroids, all with
their own symbol (though some symbols were published as only a verbal description): . The symbols grew increasingly complex as the number of objects grew, and publishers found typesetting them increasingly difficult. This difficulty was addressed by
Benjamin Apthorp Gould in 1851, who suggested numbering asteroids in their order of discovery (initially starting with the fifth asteroid,
Astraea, but within a year reseting to
(1) Ceres), and placing this number in a circle (a planetary disk) as the symbol for the asteroid – for example
④ as the symbol of the fourth asteroid,
Vesta. This numerical symbol was increasingly coupled with the name, e.g.
④ Vesta, for clarity 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. Another nine graphic symbols were devised through 1855, at which point the tradition ceased completely. None of the graphic symbols after the first four saw any notable use after the 19th century, and little within it. More reduced punctuation soon developed, such as
4) Vesta,
4, Vesta and
4 Vesta, but the
4) and
4, formats had more or less completely died out by 1949, leaving just the current
(4) and
4. The precursor to the modern system of provisional designations first appeared in the journal
Astronomische Nachrichten in 1892, and the current format has been in place since 1925. There were some later exceptions, such as the
Palomar–Leiden survey designations that were assigned between 1960 and 1977, but today all minor planets with elliptical orbits are assigned provisional designations following the MPC convention. A notable outlier to the pattern that the permanent designation reflects the order of discovery (or these days securing the orbit) is the case of
(134 340) Pluto. Since Pluto was initially classified as a planet, it was not given a minor-planet number until after a
2006 redefinition of "planet" that excluded it. A proposal a few years earlier to reserve the number (100 000) for Pluto, paralleling other round numbers that had been assigned out of sequence for the notable objects
(20 000) Varuna and
(50 000) Quaoar, was not acted on in the debate over whether a number should be assigned at all. Pluto's minor-planet number is largely a formality, and is rarely used in practice. == See also ==