A typical white dwarf has a surface temperature about four times that of the Sun and a radius about 1% that of the Sun.What can you determine about the luminosity of a typical white dwarf from this information?
A) The white dwarf will be less luminous than the Sun.
B) The white dwarf and the Sun will have about the same luminosity.
C) The white dwarf will be more luminous than the Sun.
D) Nothing can be concluded about the relative luminosities from this information.

Question

Quizplus · Accepted Answer

The luminosity of a star depends on both its surface temperature and its radius. The white dwarf has a much smaller radius (1% of the Sun's) but a higher surface temperature (four times that of the Sun). The increase in temperature increases luminosity, but the much smaller radius decreases it significantly. Overall, the decrease in radius has a larger effect, making the white dwarf less luminous than the Sun.

A Typical White Dwarf Has a Surface Temperature About Four