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Mean radius
A measure for the size of planets and other Solar System objects / From Wikipedia, the free encyclopedia
The mean radius (or sometimes the volumetric mean radius) in astronomy is a measure for the size of planets and small Solar System bodies. Alternatively, the closely related mean diameter (), which is twice the mean radius, is also used. For a non-spherical object, the mean radius (denoted
or
) is defined as the radius of the sphere that would enclose the same volume as the object.[1] In the case of a sphere, the mean radius is equal to the radius.
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For any irregularly shaped rigid body, there is a unique ellipsoid with the same volume and moments of inertia.[2] The dimensions of the object are the principal axes of that special ellipsoid.[3]