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Does the Sun’s Rotation Speed Dictate the Orbital Speed of the Planets?

-- | August 8, 2015

Question: Are the planets orbiting the sun at the same speed as the sun revolves on its axis? Or are some planets moving slower or faster than the sun spins, of course the position in the solar system dictates how long it takes to complete one full orbit, but say they were all in the same position close to the sun are they moving at the same speed as the sun spins? When the solar system formed surely the sun dictated the speed at which the dust cloud revolved, so unless objects got bumped to move faster or slower they should all be revolving roughly the same yes?? — Sammy

Answer: The Sun takes about 26 days (at its equator) to 34 days (at its poles) to rotate on its axis at its equator, which is much faster than all of the planets orbit about the Sun. In fact, the orbits of the planets are dictated (mostly) by the Sun’s gravity and their distance from the Sun. Also, the speed at which the dust cloud from which the Sun and planets formed was determined by the mass and angular momentum of the cloud itself, as it was much more massive than the Sun and planets.

Jeff Mangum

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