Published online by Cambridge University Press: 25 April 2016
A white dwarf is a body of stellar mass, but of planetary dimensions. It is self luminous with a surface temperature that has been observed as high as 70,000 K or as low as 4,000 K. Because of its low surface area the star is far fainter than a main sequence star of the same colour; equally the light it emits is bluer than that from a main sequence star of similar luminosity. Figure 1 is the HR diagram from data obtained by the US Naval Observatory showing the dwarf and white dwarf sequences.