User:Kienkua

Direct motion is the motion of a planetary body in a direction similar to that of other bodies within its system, and is sometimes called prograde motion. Retrograde motion is motion in the contrary direction. In the case of celestial bodies, such motion may be real, defined by the inherent rotation or orbit of the body, or apparent, as seen in the skies from Earth.

While the terms direct and prograde are equivalent in this context, the former is the traditional term in astronomy. Prograde was first seen in an abstract of an astronomy-related professional article in 1963 (J. Geophys. Res. 68, 4979