Solar radius

Unit of measurement

A solar radius is a unit of distance, commonly understood as 695,700 km and expressed as R ⊙ {\displaystyle R_{\odot }} , used mostly to express the size of an astronomical objects relative to that of the Sun, or their distance from it. This length is also called the nominal solar radius. The sun's actual radius, from which the unit of measurement is derived, is usually calculated as the radius from the sun's center out to the layer in the Sun's photosphere where the optical depth equals 2/3.

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