The physics of white dwarfs

White dwarfs are the final remnants of low- and intermediate-mass stars. Th eir evolution is essentially a cooling process that lasts for similar to 10 Ga (I Ga = 1 x 10(9) years) and allows one to obtain information about the age of the Galaxy as well as about the past stellar formation rate in the solar neighbourhood. Therefore, it is important to identify all of the rele vant sources of energy as well as the mechanisms that control its flow to t he space. We show in this paper that the inclusion of a detailed treatment of phase transitions in Coulomb plasmas made up of a mixture of different c hemical species is crucial, since their redistribution can keep the white d warf warm for 0.5 to 9 Ga depending on the chemical composition and physica l assumptions adopted.