Magnitude (mag or m)
A measurement of the brightness of a star or other celestial object. On the magnitude scale, the lowest numbers refer to objects of greatest brightness. A difference in magnitude of 5 corresponds to a brightness ratio of 100:1. Therefore, if two stars differ by one magnitude their brightnesses differ by a factor equal to the fifth root of 100, that is, 2.512. The brightness of a star as observed from the Earth (its apparent magnitude) depends on its intrinsic magnitude, its distance from us, and the extinction in between. The absolute magnitude is a measure of intrinsic luminosity on the magnitude scale, defined as the apparent magnitude an object would have at the distance of ten parsecs.