If a star was the same size as our Sun, but was 81 times more luminous, it must be
A) twice as hot as our Sun.
B) three times hotter than the Sun.
C) four times hotter than the Sun.
D) nine times hotter than the Sun.
E) 81 times hotter than the Sun.

Question

Quizplus · Accepted Answer

The luminosity of a star is proportional to the fourth power of its temperature (L ∝ T^4). If the star is 81 times more luminous, then (T_star/T_sun)^4 = 81, so T_star/T_sun = 3.

If a Star Was the Same Size as Our Sun