This image compares the retrograde rotation of Venus to the direct rotation of Earth.
Click on image for full size
Windows original, courtesy of Nate Proulx
What are the retrograde motions of planets in the sky?
It depends on what kind of motion you are talking about. When seen from the north pole of the celestial sphere all planets orbit around the Sun in a counter-clockwise or direct path. Most planets also rotate on their axis counter-clockwise. A few, Venus, Uranus, and Pluto, rotate clockwise and this is known as retrograde motion.
Venus has a very slow rotation (117 Earth days) on top of being retrograde. Scientists think that Venus originally had direct rotation, but that some ancient collision or other phenomenon reversed the rotation. This could also account for why Venus rotates so slowly.
Scientist debate whether Uranus' orbit is retrograde or not. Uranus is tilted on its axis nearly 90 degrees. Either the axial inclination is a bit under 90 degrees and the rotation is retrograde or it is a bit over 90 degrees and Uranus has direct rotation.
Submitted by Kyle (age 13, Canada)
(June 17, 1999)
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