Two white dwarf stars are the same size, but one has a surface temperature twice as hot as the other. The hotter star will radiate
A)half as much energy per second as the cooler star.
B)the same amount of energy per second as the cooler star.
C)four times as much energy per second as the cooler star.
D)sixteen times as much energy per second as the cooler star.

Question

Quizplus · Accepted Answer

The luminosity (energy radiated per second) of a star is proportional to the fourth power of its temperature (Stefan-Boltzmann law). Therefore, if one star's surface temperature is twice that of another, it will radiate $2^4 = 16$ times as much energy per second.

Two White Dwarf Stars Are the Same Size, but One