Magnitude is a logarithmic measure of the brightness of an astronomical object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths. An imprecise but systematic determination of the magnitude of objects was introduced by Hipparchus.

Scale of measureEdit

Astronomers observe apparent magnitudes and absolute magnitudes of celestial objects. The apparent magnitude (m, or vmag for the visible spectrum) is the brightness of an object as it appears in the night sky from Earth, while the absolute magnitude (Mv, V and H) describes the intrinsic brightness of an object as it would appear if it were placed at a certain distance from Earth, 10 parsecs for stars. A more complex definition of absolute magnitude is used for planets and small Solar System bodies, based on its brightness at one astronomical unit from the observer and from the sun.


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