The Size (Radius) of a Star
We already know: flux increases with surface temperature (~ T4); hotter stars are brighter.
But brightness also increases with size:
A
B
Star B will be brighter than star A.
Absolute brightness is proportional to radius squared, L ~ R2.
Quantitatively:      L = 4 p R2 s T4
Surface area of the star
Surface flux due to a blackbody spectrum
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