## luminosityThe total amount of energy that an object, such as a star, radiates into space every second. Luminosity depends on both the surface area and the surface temperature of an object, so that, for example, two stars with the same surface temperature but different luminosity must differ in size. Luminosity, L, is measured in watts (W) or in terms of solar luminosity
L_{sun} (3.9 × 10^{26} W) and is related to
bolometric magnitude (M_{bol})
by the formula: M_{bol} - 4.72 = -2.5 log (L/L_{sun})
For example, in the case of Sirius L/L_{sun} = 23,
so that M_{bol} (Sirius) = 4.72 - 2.5 log 23 = 1.32. The luminosity of a blackbody (which most stars closely approximate) of temperature T and radius R is
given by the Stefan-Boltzmann equation: L = 4πR^{2}σT^{4}
where σ is the Stefan-Boltzmann constant (5.67 × 10 ^{-8}
W/m^{2}/K^{4}). ## Related category• ASTRONOMICAL QUANTITIES | |||||

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