luminance ( def. 2 ) .

the quality of being intellectually brilliant, enlightened, inspired, etc.

The luminosity of his poetry is unequaled.

something luminous.

Astronomy . the brightness of a star in comparison with that of the sun

the luminosity of Sirius expressed as 23 indicates an intrinsic brightness 23 times as great as that of the sun.

Also called luminosity factor. Optics . the brightness of a light source of a certain wavelength as it appears to the eye, measured as the ratio of luminous flux to radiant flux at that wavelength.

noun

brilliance , brilliancy , radiance