what is used to calculate the absolute magnitude of a star?
If the star was at 10 parsecs distance from us, then its apparent magnitude would be equal to its absolute magnitude. The absolute magnitude is a measure of the star's luminosity---the total amount of energy radiated by the star every second. If you measure a star's apparent magnitude and know its absolute magnitude, you can find the star's distance (using the inverse square law of light brightness). If you know a star's apparent magnitude and distance, you can find the star's luminosity (see the table below).