Object Type Definition¶
The Minor Planet Center defines some broad classes of objects.
These classes are encoded in the object_type field of the MPCORB format and the object_type property of the MPC_ORB JSON format.
The following table lists the object types and their assigned numbers.
Object Type Classification¶
| Object Type | Assigned Number | Definition |
|---|---|---|
| Minor Planet | 0 | Object in orbit around the Sun that is exclusively classified as neither a planet nor a comet. Includes asteroids, Mars-crossers, main-belt asteroids, Jupiter trojans, centaurs, and trans-Neptunian objects. |
| Minor Planet (Binary) | 1 | System of two asteroids orbiting their common barycenter. |
| Past Impactor | 6 | Object that has impacted with the Earth and that has been identified before the impact, e.g. 2014 AA. |
| Comet | 10 | Body made of rock and ice, typically a few kilometres in diameter, which orbits the Sun. |
| Comet (Fragment) | 11 | Piece of comet that has broken off from the main body. |
| Comet Without Orbit | 12 | Comet for which the MPC does not have sufficient observations to determine an orbit (mostly coming from literature, e.g. X/-233 B1). |
| Disintegrated Comet | 13 | Comet that has been observed to disintegrate (e.g. 3D/Biela). |
| Dual Status (Minor Planet and Comet) | 20 | Object with both minor planet and cometary designation; initially classified as a minor planet but showing cometary activity. |
| Irregular Natural Satellite (of planet) | 30 | Object well within the Hill sphere of a planet and appears gravitationally bound. An irregular satellite is a satellite of a major planet that follows an orbit that is irregular in some of the following ways: distant; inclined; highly elliptical; retrograde. |
| Regular Natural Satellite (of planet) | 31 | Object well within the Hill sphere of a planet and appears gravitationally bound. A regular satellite is a natural satellite that orbits close to its parent planet, typically in a prograde motion (same direction as the planet's rotation) and within the equatorial plane. |
| Natural Satellite (of minor planet) | 40 | Object that has been measured to orbit around another minor planet or the center of mass of a minor planet system. |
| Interstellar Object | 50 | Object that originates from outside the solar system and is not gravitationally bound to the Sun. |