(a) An astronomer obtains the spectrum of a white dwarf star, and determines that it peaks in the ultraviolet at λ = 150 nm, similar to the spectra of very luminous main-sequence stars. What is the surface temperature of the white dwarf?
(b) At the same time, the astronomer determines that the intrinsic luminosity of the white dwarf is only LW D = 0.01L? (i.e. 1% of the luminosity of the Sun). As discussed in class, the luminosity and temperature of a star can be used to infer its radius. What is the radius of the white dwarf star? Express your answer in terms of the radius of the Sun, R?, and the radius of the earth, R⊕. (i.e., how many solar [Earth] radii is this? Or, on the other hand, what fraction of the solar [Earth] radius is this?)