Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while star B is magnitude +7.3. Which statement is true?
A) Star A is both 100× brighter and larger than star B.
B) Star B must be ten times more luminous.
C) Star A must be ten times closer.
D) Star A is both 100× brighter and more luminous than star B.
E) Nothing, since we do not know their absolute magnitudes.

Question

Quizplus · Accepted Answer

Star A's apparent magnitude is brighter than Star B's by 5 magnitudes, which means it is 100 times brighter. Since they have the same parallax, they are at the same distance, making Star A also more luminous by the same factor.

Two Stars Both Have Parallaxes of 0