Planet

An opaque celestial body which receives its light from the sun, and around which it revolves. The eight principal planets are the following, which are named in the order of their distances from the sun: Mercury (nearest to the sun), Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Near the sun is a small planet named Vulcan.

Inferior Planets. The planets whose orbits are within that of the earth--Vulcan, Mercury and Venus.

Minor Planets. A name given to the small planets collectively.

Primary Planets. Planets which revolve only about the sun.

Secondary Planets. Satellites which revolve also about their primaries.

Superior Planets. The planets whose orbits are without that of the earth--Mars, Jupiter, Saturn, Uranus and Neptune.