(mathematics) A unit of a solid angle equal to (π/180)2 steradian, or approximately 3.04617 × 10-4 steradian.
Square degree
| Sci-Tech Dictionary: square degree |
(′skwer di′grē)
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| Measures and Units: square degree |
solid angle. Symbols □° (°)2. The equivalent to the square of the ordinary planar degree, hence = ( π/180)2 steradian.
This simple-looking transformation is misleading, for the two degrees are in spatial dimensions 2 and 3 rather than 1 and 2, and the parameter π is not raised to a power for the steradians in a sphere. Since there are 4π steradians in the sphere, the square degree = π/129600 sphere.
| Wikipedia: Square degree |
A square degree is a non-SI unit measure of solid angle. It is denoted in various ways, including deg2, 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 steradian. The number of square degrees in a whole sphere is
or approximately 41,253 deg2. This is the total area of the 88 constellations in the list of constellations by area.
For example, observed from the surface of the Earth, the Moon has a diameter of approximately 0.5°, so it covers a solid angle of approximately 0.20 deg2, which is 4.8 × 10−6 of the total sky sphere.
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Mentioned in
- square grade (solid angle)
- symbols (mathematics, mathematics, sub-atomic physics, mass, sub-atomic physics, sub-atomic physics, electromagnetics, sub-atomic physics, mathematics, geology)
- Astronomical catalogs (astronomy)
- degree (length, plane angle, solid angle, mathematics, statistics, physics, hydrometry, viscometry, hardness of water, photography, geography, medicine)
