Astronomy & Space
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Kepler Third Law (General)

Orbital period from semi-major axis.

Formula

T2=4π2GMa3T^2 = \frac{4\pi^2}{GM}a^3

Variables

aSemi-major axis
MCentral mass

Example

Farther planets orbit slower

Did You Know?

Kepler's third law ties a planet's year to its distance, which is why distant Neptune takes 165 Earth years to orbit.

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