| apparent magnitude (symbol m) |
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A measure of the relative brightness of a star (or other celestial object) as perceived by an observer on Earth. Apparent magnitude depends on both the absolute amount of light energy emitted (or reflected) and the distance to the object. The smallest numbers correspond to the greatest brightness. To encompass very bright objects, the scale is extended to zero and on to negative numbers. For example, the apparent magnitude of the full Moon is -12.6 and that of the planet Venus at its brightest is -4.7. The term apparent magnitude, without further qualification, is usually taken to mean apparent visual magnitude, the relative brightness as seen over the visible part of the spectrum. See also: magnitude, absolute magnitude, photometry. |