Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
A) The red star is more massive than the blue star.
B) The blue star is more massive than the red star.
C) The blue star is farther away than the red star.
D) The blue star has a hotter surface temperature than the red star.
E) The red star has a hotter surface temperature than the blue star.
Answer: D