White dwarf in the galactic halo. Artwork of a white dwarf star (yellow, lower right) in the halo of our Milky Way Galaxy. White dwarf stars are the remnants of stars that were born many billions of years ago. The galactic halo is a spherical shell of older stars that formed before the spiral disk of the Milky Way. A survey in March 2001, by Ben Oppenheimer et al, reported that there could be as many as 200 billion white dwarf stars in the galactic halo. This could account for up to 35% of the mass of the galactic halo, and make up part of the dark matter of the Milky Way. This dark matter makes up 90% of the mass of the galaxy. Visible stars only account for 10% of the galactic mass.