A third magnitude star is three times brighter than a first magnitude star.

Question

Quizplus · Accepted Answer

Magnitude is a measure of a star's brightness, but it is not proportional in the sense that a 3rd magnitude star is three times brighter than a 1st magnitude star. In fact, the magnitude system is logarithmic, so a 1st magnitude star is about 2.5 times brighter than a 2nd magnitude star, and a 2nd magnitude star is about 2.5 times brighter than a 3rd magnitude star. Therefore, a 3rd magnitude star is actually about 15 times fainter than a 1st magnitude star.

A Third Magnitude Star Is Three Times Brighter Than a First