Square degree
A square degree (deg2) is a non-SI-compliant unit measure of solid angle. Other denotations include sq. deg. and (°)2. Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere. Analogous to one degree being equal to π/180 radians, a square degree is equal to (π/180)2, or about 1/3283 = 3.0462×10−4 steradians (0.30462 msr).
The number of square degrees in a whole sphere is approximately 41253 deg2. This is the total area of the 88 modern constellations in the sky.
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