Final answer:
The absolute magnitude of a star is the brightness the star would appear to have if it were placed at a standard distance of 10 parsecs (32.6 light-years) from Earth. This allows astronomers to compare the true brightness of different stars.
Step-by-step explanation:
The absolute magnitude of a star is the brightness the star would appear to have if it were placed at a standard distance of 10 parsecs (32.6 light-years) from Earth. This standard distance allows astronomers to compare the true brightness of different stars. By knowing the absolute magnitude, we can determine the luminosity or total amount of energy a star emits.
For example, a star with an absolute magnitude of 0 would appear as bright as the Sun if it were placed at a distance of 10 parsecs from Earth. If a star has a higher absolute magnitude, it would appear brighter than the Sun at that same distance. If a star has a lower absolute magnitude, it would appear dimmer than the Sun at that distance.
Using the given options, the correct answer is c. 10 ly.