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Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or nutation of an object's rotational axis .
The retrograde motion of a hypothetical extremely distant (and nearly non-moving) planet would take place during a half-year, with the planet's apparent yearly motion being reduced to a parallax ellipse. The center of the retrograde motion occurs at the planet's opposition which is when the planet is exactly opposite the Sun.
The Sun-centered positions displayed a cyclical motion with respect to time but without retrograde loops in the case of the outer planets. [dubious – discuss] In principle, the heliocentric motion was simpler but with new subtleties due to the yet-to-be-discovered elliptical shape of the orbits. Another complication was caused by a problem ...
This is called "apparent direct" motion. A satellite in a direct orbit with an orbital period greater than one day will tend to move from east to west along its ground track, in what is called "apparent retrograde" motion. This effect occurs because the satellite orbits more slowly than the speed at which the Earth rotates beneath it.
Planets moving in direct motion, aka non-retrograde planets, act in a very predictable way without much fuss or fanfare. Most of the time, planets move in this forward motion, and things carry on ...
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Here are the dates for Mercury retrograde, Venus retrograde, Saturn retrograde, Neptune retrograde, Pluto retrograde and more. ... When in forward motion, Saturn teaches us lessons and motivates ...
Retrograde motion, an orbit in the opposite direction of the rotation of the central mass or most other satellites; Retrograde signaling, the process where a signal travels backwards from a target source to its original source; Apparent retrograde motion, the apparent motion of planets as observed from a particular vantage point