Luminosity
![Image of galaxy NGC 4945 showing the huge luminosity of the central few star clusters, suggesting there is an AGN located in the center of the galaxy.](/Images/godic/202502/14/Phot-27e-074215.jpg")
![Hertzsprung–Russell diagram identifying stellar luminosity as a function of temperature for many stars in our solar neighborhood.](/Images/godic/202502/14/Hertzsprung-Russel_StarData4215.png")
![Artist impression of a transiting planet temporarily diminishing the star's brightness, leading to its discovery.[10]](/Images/godic/202502/14/Heic0612b_H4215.jpg")
![Point source S is radiating light equally in all directions. The amount passing through an area A varies with the distance of the surface from the light.](/Images/godic/202502/14/Inverse_square_law.svg4215.png")
In astronomy, luminosity is the total amount of energy emitted by a star, galaxy, or other astronomical object per unit time. It is related to the brightness, which is the luminosity of an object in a given spectral region.
In SI units luminosity is measured in joules per second or watts. Values for luminosity are often given in the terms of the luminosity of the Sun, which has a total power output of 3.846×10 W. The symbol for solar luminosity is L⊙. Luminosity can also be given in terms of magnitude. The absolute bolometric magnitude (Mbol) of an object is a logarithmic measure of its total energy emission.