You observe a red star and a blue star and are able to determine that they are the same size. Which star is hotter, and which star is more luminous?
A) The red star is hotter and more luminous.
B) The red star is hotter, and the blue star is more luminous.
C) The blue star is hotter and more luminous.
D) The blue star is hotter, and the red star is more luminous.
E) They have the same luminosities and temperatures.

Question

Quizplus · Accepted Answer

The color of a star is directly related to its temperature. Blue stars are hotter than red stars. Since the two stars are the same size, we can compare their luminosities by comparing their brightness. The brighter star has a higher luminosity. Therefore, since the blue star is hotter and appears brighter than the red star, it is also more luminous.

You Observe a Red Star and a Blue Star and Are