An Etymological Dictionary of Astronomy and Astrophysics
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The fraction of the total light or other radiation which falls on a non-luminous body, such as a → planet, → satellite, or → asteroid, and which is reflected by it. Generally, the albedo is equal to the ratio between the light quantity reflected and the light quantity received. The albedo values range between 0.0 (0%), for a perfectly black area, which absorbs all incident light, and 1.0 (100%) for a perfect reflector. The planets or planetary satellites with dense atmospheres have greater albedos than those of transparent atmospheres or of no atmospheres. The albedo can vary from one surface point to another, so that a mean albedo is given for practical purposes. The natural surfaces reflect different light quantities in different directions and the albedo can be expressed in several ways, depending on the way in which the measurement was made: in one direction or, on the average, in all directions (M.S.: SDE). See also → Bond albedo, → geometric albedo.

Albedo, L. "whiteness," from albus "white," from PIE base *albho- "white". Compare with Gk. alphos "white leprosy," O.H.G. albig, O.E. elfet "swan, the white bird". The idea of whiteness derives from the fact that whiter bodies have a higher reflective power, while opaque objects are more absorptive.

Sepidâ, from sepid, →, white, + -â noun-forming prefix from certain adjectives.

The fraction of the total amount of electromagnetic radiation falling upon a non-luminous spherical body that is reflected in all directions by that body. The bond albedo takes into account all wavelengths at all → phase angles. Compare with → geometric albedo.

Named after the American astronomer George Phillips Bond (1825-1865), who proposed it; → albedo.

A measure of the → reflectivity of a surface, especially of the solar system bodies (planets, satellites or asteroids). It is the ratio of a body's brightness at zero → phase angle to the brightness of a perfectly diffusing disk with the same position and apparent size as the body. Geometric albedo depends on the radiation wavelength. The bolometric geometric albedo refers to reflectivity in all wavelengths. Compare with the → Bond albedo.

→ geometric; → albedo.