Luminosity
WordNet
noun
(1) The quality of being luminous; emitting or reflecting light
"Its luminosity is measured relative to that of our sun"
WiktionaryText
Noun
- the state of being luminous, or a luminous object; brilliance or radiance
- the ratio of luminous flux to radiant flux at the same wavelength; the luminosity factor
- the rate at which a star radiates energy in all directions