Final answer:
Absolute magnitude (M) is a measure of a star's intrinsic brightness at a standard distance of 10 parsecs, while luminosity (L) is the amount of light energy a star emits. The more luminous a star, the lower its absolute magnitude. These concepts are related through a logarithmic formula that allows comparison of stellar brightness.
Step-by-step explanation:
The question of how absolute magnitude (M) is compared to luminosity (L) falls within the realm of astronomy, a subfield of physics. Absolute magnitude is a measure of the intrinsic brightness of a celestial object, such as a star, as it would appear at a standardized distance of 10 parsecs (32.6 light-years) from the observer. On the other hand, luminosity refers to the actual amount of light energy a star emits from its surface. The two concepts are related in that the luminosity determines the absolute magnitude; the more luminous a star is, the lower (or more negative) its absolute magnitude will be.
For example, if two stars have the same luminosity, they will have the same absolute magnitude, regardless of their distance from Earth. However, if one is more luminous than the other, it will have a lower absolute magnitude, appearing brighter even if it were at the standard distance of 10 parsecs. Absolute magnitude allows astronomers to compare the brightness of celestial objects without the ambiguity caused by distance.
To formalize the relationship, we use the formula:
where M0 is the zero point for absolute magnitude and L0 is a reference luminosity. The logarithmic nature of the formula indicates a multiplicative relationship between luminosity and absolute magnitude, with the brightest stars having high luminosity and low (negative) absolute magnitude figures.