Page "Flux" Paragraph 22

# Radiative flux, the amount of energy transferred in the form of photons at a certain distance from the source per steradian per second ( J · m < sup >− 2 </ sup >· s < sup >− 1 </ sup >).

Used in astronomy to determine the magnitude and spectral class of a star.

Also acts as a generalization of heat flux, which is equal to the radiative flux when restricted to the infrared spectrum.