text: Most observed white dwarfs have relatively high surface temperatures , between 8,000 K and 40,000 K. A white dwarf , though , spends more of its lifetime at cooler temperatures than at hotter temperatures , so we should expect that there are more cool white dwarfs than hot white dwarfs . Once we adjust for the selection effect that hotter , more luminous white dwarfs are easier to observe , we do find that decreasing the temperature range examined results in finding more white dwarfs .
simplified: Some white dwarfs are blue , instead of white .