In astronomy, values for luminosity are often given in the terms of the luminosity of the Sun, L ⊙. In SI units, luminosity is measured in joules per second, or watts. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a star, galaxy, or other astronomical objects. Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. A star with four times the radiative power of the Sun has a luminosity of 4 L ⊙. In astronomy, this amount is equal to one solar luminosity, represented by the symbol L ⊙.
The Sun has an intrinsic luminosity of 3.83 ×10 26 watts. For other uses, see Luminosity (disambiguation).
