A cooled white dwarf is a black dwarf.
I think you are thinking of a neutron star which has nothing to do with a white dwarf.
In 5 billion years time, our Sun will turn into a white dwarf.
A white dwarf is much larger than a neutron star.
Once a medium sized star has consumed all it's fuel it becomes a White Dwarf star (just the extremely dense core of the original star remains composed mainly of carbon). A White Dwarf star will, however, eventually lose it's heat to become a Black Dwarf.
As a white dwarf loses energy and cools down, it eventually transitions into a black dwarf. A black dwarf is a hypothetical stellar remnant that has cooled to the point where it no longer emits heat or light. It is smaller and denser than a white dwarf.
The obvious reason is that the specific star has bigger density compared with the Sun. For example, that star could be a "white dwarf star". A white dwarf mostly contains "electron degenerate matter", which is very dense. A white dwarf is a small dense star.
In 5 billion years time, our Sun will turn into a white dwarf.
A white dwarf is typically about the size of Earth, but with a mass comparable to that of the Sun. This means it is extremely dense, packing a lot of mass into a small volume.
A black dwarf is a theoretical end-stage of a white dwarf star in the far future, after it has cooled down and no longer emits light. White dwarfs are hot, dense remnants of low to medium mass stars at the end of their evolution.
A white dwarf is the remains of an old star, but they still remain very hot and will continue to shine as a white dwarf for many millions of years until they gradually cool off to become black dwarfs. They are very dense.
White dwarf
A white dwarf is much larger than a neutron star.
White dwarf
Once a medium sized star has consumed all it's fuel it becomes a White Dwarf star (just the extremely dense core of the original star remains composed mainly of carbon). A White Dwarf star will, however, eventually lose it's heat to become a Black Dwarf.
When the outer envelope of a red giant recedes, the remaining carbon core is called a white dwarf. This core is extremely hot and dense, with no nuclear fusion taking place.
white dwarf
white dwarf
As a white dwarf loses energy and cools down, it eventually transitions into a black dwarf. A black dwarf is a hypothetical stellar remnant that has cooled to the point where it no longer emits heat or light. It is smaller and denser than a white dwarf.