inferior planet, planet whose orbit lies inside that of the earth. There are two inferior planets, Mercury and Venus. They always seem to be close to the sun in the sky; the greatest elongation of Mercury is 28°, and that of Venus, 47°. For this reason, neither can be seen for more than two or three hours after sunset or before sunrise.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
More on inferior planet from Fact Monster:
See more Encyclopedia articles on: Astronomy: General