Retrograde and direct motion
Overview
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
ary body in a direction opposite to that of other bodies within its system as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies.
While the terms direct and prograde are equivalent in this context, the former is the traditional term in astronomy.
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