An astronomer is measuring the electromagnetic radiation emitted by two stars, both of which are assumed to be perfect blackbody emitters. For each star she makes a plot of the radiation intensity per unit wavelength as a function of wavelength. She notices that the curve for star A has a maximum that occurs at a shorter wavelength than does the curve for star B. What can she conclude about the surface temperatures of the two stars?

a. Star A has the greater surface temperature.
b. There is not enough information to draw a conclusion about the temperatures.
c. Star B has the greater surface temperature.
d. Both stars, being perfect blackbody emitters, have the same surface temperature.