luminosity

n. quality or condition of being luminous, brightness; something which emits light; strength of light emitted from a light source

Luminosity has different meanings in several different fields of science.
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Noun
1. the quality of being luminous; emitting or reflecting light; "its luminosity is measured relative to that of our sun"
(synonym) brightness, brightness level, luminance, luminousness, light
(hypernym) physical property
(hyponym) illuminance, illumination
(attribute) bright

(n.)
The quality or state of being luminous; luminousness.
  

The total energy radiated into space every second by a celestial object such as a star.