There are three ways to talk about a star’s brightness.
We can discuss the apparent magnitude of a star, or how bright it appears when we look at it.
We know, however, that stars nearer the earth appear brighter than faraway stars, even though they may not actually be brighter.
So, astronomers also talk about the absolute magnitude of stars, or the brightness of a star if the observer were 10 parsecs from it.
The third way to measure a star’s brightness is called luminosity.
Luminosity is a measure of how much energy a star puts out in comparison to our Sun.