Audio Guide：

Brightness and luminosity are two completely different concepts. Brightness refers to the brightness of an astronomical object that we have observed, which can be expressed by "apparent magnitude." Brightness is related to distance. The farther a star, the lower its brightness. On the other hand, luminosity refers to the total energy radiated from a star. Luminosity is related to the astronomical object itself, not distance. “Absolute Magnitude” is the brightness of a star at a presupposed distance of 32.6 light years.