Lists of Minor Planets - Numbering and Naming Conventions

Numbering and Naming Conventions

After discovery, asteroids generally receive a provisional designation (such as "1989 AC"), then a number (such as 4179), and finally (optionally) a name (such as "Toutatis"), in that order.

In modern times, an asteroid receives a sequential number only after its orbit is precisely known. Asteroids whose orbits are not (yet) precisely known are known by their provisional designation. This rule was not necessarily followed in earlier times, and some asteroids received a number but were subsequently "lost". All of these have now been recovered; the last "lost" numbered asteroid was 719 Albert.

Only after a number is assigned is the asteroid eligible to receive a name. Usually the discoverer has up to 10 years to pick a name; some asteroids remain unnamed. Especially towards the end of the twentieth century, with large-scale automated asteroid discovery programs such as LINEAR, the pace of discoveries has increased so much that it seems likely that the vast majority of minor planets will never receive names.

For the reasons mentioned above, the sequence of numbers only approximately matches the timeline of discovery. In extreme cases, such as "lost" asteroids, there may be a considerable mismatch: for instance the high-numbered 69230 Hermes was originally discovered in 1937, but it was a lost asteroid until 2003. Only after it was rediscovered could its orbit be established and a number assigned.