White dwarf

The dying remains of a giant star that has blown away its outer layers to leave an extremely hot core. Only the youngest white dwarfs are really white; after billions of years they cool down slowly and change colour, going from yellow to orange (in fact the coldest white dwarfs are seen as blue because the compressed hydrogen atmosphere surrounding them filters out the red light). These stars will end up as black dwarfs, completely dead; however, because the universe is less than 15 billion years old, none have yet arrived at this stage. They are classified as type D.