White dwarf stars

Abstract

White dwarf stars were first discovered only fifty years ago, when the science of astrophysics was in its infancy. The original discovery appears to have been made by Russell (l). He had just found from his work on trigonometrical parallaxes that all intrinsically faint stars were of spectral type M and then learnt that 40 Eri B was both intrinsically faint and hot. Slightly later Adams (2) gave the spectrum of Sirius B as A or early F and van Maanen (3) described the spectrum, of van Maanen 2. These three stars were soon realised to be the prototype members of a class of stars of very small radius and high temperature which consequently became known as the white dwarfs. The small radius and high temperature of these stars implied a high density. The mass of Sirius B was known from its double star orbit with Sirius A and its parallax and apparent magnitude were also known. Adams’ spectra implied a temperature of 10,000°K. This temperature and the absolute magnitude implied a radius of about 19,000 km and this, combined with the mass of between 0.75 and 0.95 solar masses, gives a mean density of about 60,000 gm/cm3. Show more