The hotter something is glowing the more white/blue it appears. A dying medium sized star expands, cools and becomes a red giant for a while, but eventually it is going to gravitationally collapse (once enough Iron (Fe) is accumulated in the core). Then it blows the outer layers away and what is left collapses into a white dwarf.
What makes the dwarf shine? and why is it white?
Does the luminosity decreases as the object cools down, or is there some other reaction that keeps it glowing for a long time?
Can a white dwarf turn brown or black never to be seen again?
Do all white dwarfs turn into Neutron stars eventually?
Answer
White dwarf stars used to be the interior of a star, which was the hottest part of the star. They shine white because they are still very hot from this past part of their history. As they age, they will cool, and as they cool, they will lose temperature, and their blackbody profile will shift to redder and redder colors, and eventually into the infared and radio ranges where they won't seem to shine at all to the naked eye.
And yes, a white dwarf state is a stable final state of a star, so long as it does not interact further with any matter. If that happens, it is possible to have a White Dwarf supernova
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