What is the temperature of a white dwarf star?
There is no set temperature
A white dwarf is a normal star that has collapsed upon itself when its fuel got burnet up, giving it a density of about 1000kg/cm³. A white dwarf has no fuel left so it doesn't produce any heat and is slowly cooling down untill it doesn't emit any visible light, making it a black dwarf. Thats why it's hard to set a temperature of white dwarfs in general because it depends of how long it has been without any fuel.
White dwarfs are between 6,000 and 30,000 degrees kelvin.
When a star of less that eight solar masses runs out of Hydrogen in its core, the mainly Helium core collapses and heats up. When the core gets hot enough, Helium fusion starts.
Once the supply of Helium is exhausted, the core is mainly Carbon and Oxygen. The core can't get hot enough to start Carbon fusion. At this stage the core collapses into a white dwarf.
Although there is no fusion taking place in a white dwarf it is still quite hot. White dwarfs range in temperature from
It is thought that after many billions of year a white dwarf will cool into a black dwarf. The universe isn't old enough for this to have happened yet.