Centaur A planetary body found in orbit around the Sun between the orbits of Neptune and Saturn, e.g., Chiron. These bodies typically display a variety of characteristics, ranging from asteroidal in appearance to cometlike. The nature of the Centaurs' orbits indicates relatively recent arrival at their present positions, leading scientists to theorize that Centaurs are migrated Kuiper Belt objects. The spherical envelope of gas and dust surrounding the nucleus of an active comet, created when the ambient heat causes the vaporization of comet material. Comet A volatile-rich body that develops a transient atmosphere, or coma, as it approaches the Sun.
Most observed comets have highly elliptical orbits, sometimes approaching parabolic.
The largest class of asteroids, grouped according to their spectral characteristics. In general they have low albedos and are believed to have significant mineralogical similarities to the carbonaceous chondrite meteorites. Declination Celestial latitude, measured in degrees north or south of the ecliptic. The process by which a planetary body becomes heterogeneously mixed, as heavier material sinks to its core and lighter materials float toward its surface. The plane of Earth's orbit around the Sun.