Answer:
Astronomers define star brightness in terms of apparent magnitude β how bright the star appears from Earth β and absolute magnitude β how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs. (A light-year is the distance light travels in one year β about 6 trillion miles, or 10 trillion kilometers.) Astronomers also measure luminosity β the amount of energy (light) that a star emits from its surface.
