White Dwarfs are degenerate stars. They are created when the
host star has exhausted it's supply of hydrogen. Its luminosity
comes from the emission of stored thermal energy, it has no other
means of energy as all fusion has ceased nor can it generate any
energy from gravitational collapse.
A white dwarf is very hot when it is formed, but as it has no source of energy, it will gradually cool down. This means that in time it will lessen and redden with time and eventually cool to become a black dwarf.