The Naming of Asteroids

How do asteroids get their names?

By: Professor David Rothery (Department of Physical Sciences)

  • Duration 5 mins
  • Updated Wednesday 4th August 2004
  • Introductory level
  • Posted under Astronomy
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The first asteroids to be discovered were given names from classical mythology, such as Ceres, Juno, Pallas and Vesta. The International Astronomical Union (IAU) now regulates the naming of asteroids. Names are no longer restricted to mythological characters, but must be inoffensive and not connected with recent political or military activity.

However, no asteroid is awarded a name until it has been observed long enough for its orbit to be determined with a fair degree of precision. This may take several years, but when it is achieved the body is awarded a “permanent designation” (a number issued in strict numerical sequence) and the discoverer is invited to suggest a name for approval by a special committee of the International Astronomical Union.

Strictly speaking, Ceres, the first known asteroid, is known as (1) Ceres. Examples of more unusual or whimsical names include (7758) Poulanderson (named after a science fiction author), (8749) Beatles (named after the 1960s pop group), and (5460) Tsenaat'a'i (which means “flying rock” in the Navaho language).

The prize for the most imaginative name goes to (2037) Tripaxeptalis. The name is pure invention but sounds like “triPax-septAlice”, which reflects the fact that its permanent designation is three times that of (679) Pax and seven times that of (291) Alice.

Until its orbit has been sufficiently well-documented, each new discovery is known only by a “provisional designation” consisting of the year of discovery followed by two letters and, if necessary, numbers that relate more precisely to the date and sequence of discovery.

For example, the asteroid (4179) Toutatis was discovered in early January 1989 and initially had the provisional designation 1989 AC, in which the first letter (A) signifies that it was discovered during the period January 1-15 and the second letter (C) shows that it was the third discovery during that period. The letter I is not used in this convention, so the remaining 25 letters of the alphabet enable 25 asteroids to be designated during each half-month period. When this number is exceeded, the letter code sequence is repeated as any times as necessary with a numerical subscript that is incremented every 25 discoveries (so that 1989 AC1 would indicate the 28th discovery during the first half of January 1989).

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