White giant stars are rare, they tend to be classified as Blue Giant Star. Thuban, the brightest star in the constellation of Draco, the Dragon is sometimes seen as a White Giant star, other times its blue. Thuban was once the Pole Star before Polaris received the title.
Giant White Stars will have a Spectral type of A rather than D. White Giants tend to be at the hotter end of the star spectrum. The opposite end are red, brown and black stars.
The Sun although it is a G Type star, a yellow star is actually a white star when looked at from space. The atmosphere causes the star to appear yellow. the Sun has been referred to as a Yellow dwarf star because it is smaller than the larger supergiant yellow stars such as V766 Centauri. It is incorrect to refer to it as a White Dwarf Star therefore.
When a star dies, it will either become a neutron star, black hole if it has high mass otherwise a nebula. At the heart of the nebula will be a neutron or a white dwarf star. What dictates how a star will become either a white dwarf or a neutron is the following :-
A white dwarf will exist for many more years as a white dwarf than as it did as a main sequence star. After an unimaginably long time, it will turn into a black dwarf having run out of energy to shine. Whilst no black dwarf exists yet, there are a number of white dwarf stars out there, the nearest being a mere 8.6 light years away as the companion star to Sirius.
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