# Luminosity

Basic property used to characterize stars, luminosity is defined as the total energy radiated by a star each second. An object’s luminosity is often compared to that of the Sun (Lsun = 4 × 1033 ergs/s = 3.9 × 1026 Watts). Luminosity has the same units as power (energy per second). Luminosity can be related to the absolute magnitude, MV, by the equation:

Where, L* is the luminosity of the object in question and Lstd is a reference luminosity (often the luminosity of a ‘standard’ star such as Vega). Luminosity can be quoted for the energy emitted within a finite waveband (e.g. optical luminosity), or for the energy emitted across the whole electromagnetic spectrum (“bolometric” luminosity). Note that measurement of the luminosity requires an object’s apparent magnitude and the distance to the object. Thus, estimates of luminosity rely on accurate distance measurements.

Some or all content above used with permission from J. H. Wittke.

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