Two main-sequence stars have the same temperature. If star A is four times brighter than star B, then:
A) star B is two times farther away than star A
B) star B is four times farther away than star A
C) star B is eight times farther away than star A
D) star B and star A lie at the same distance from us
E) it is impossible to determine their relative distances from the information given

Question

Quizplus · Accepted Answer

The brightness of a star is inversely proportional to the square of its distance from the observer. If star A is four times brighter than star B, then star B must be at a distance that is the square root of 4 (i.e., 2) times farther away than star A.

Two Main-Sequence Stars Have the Same Temperature