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orbital period

The time taken for a body to go once around a closed orbit. The orbital period of a planet is its "year".

For a body in an elliptical orbit of semimajor axis a about a much more massive body of mass M the orbital period P is given by

P = (2πa3/2) / √(gM).

This is the mathematical formulation of the third of Kepler's laws of planetary motion.

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