Last modified: Wed 4/16/97 0200 PDT
 Canon Terms |
Object | Classes | StellarSatellite; Planet; Moon; Asteroid; Meteoroid; Meteor; Meteorite; Comet |
| Instances | (none) | ||
| Event | Classes | (none) | |
| Instances | (none) |
A stellar satellite is a Physical Agent in the extraterrestrial universe (with the single exception of Earth itself, by definition) which is in orbit around a star but which is not itself a star. Material making up the solid outer parts of a stellar satellite is usually referred to as rock.
A planet is a stellar satellite which is large enough to have a significant gravitational field (near the orders of magnitude of the solar planets,until recently the only known planets).
A moon is a stellar satellite which orbits a planet directly (and a star only indirectly, by virtue of the planet's orbit).
The moons of the solar planets are the only known moons.
An asteroid is a stellar satellite which is similar to a planet except that it is too small to have a significant gravitational field. An asteroid orbits its star mostly within the general region delimited by the orbits of the star's planets. Asteroids are sometimes called planetoids or minor planets. An asteroid whose projected trajectory intersects that of Earth is referred to as a meteoroid. When a meteoroid strikes the Earth atmosphere, producing a streak of light (a "falling star" or "shooting star"), it is referred to as a meteor. If material survives incineration in the atmosphere and falls to the surface, it is referred to as a meteorite.
The solar asteroids are the only known asteroids.
A comet is a stellar satellite which is similar to an asteroid except that it has a very elliptical orbit around its star which brings the satellite both very close to the star and into deep space beyond the orbits of the star's planets.
The solar comets are the only known comets.