How does a black dwarf star form?

Answer 1

A white dwarf is the last stage of a low mass stars life. After a red giant is done fusing helium to carbon and oxygen, the star will collapse to a white swarf. White dwarves are usually between 15,000-6,000 kelvins.
A white dwarf is formed when a small or medium-sized star runs out of fuel in its core. The star becomes a red giant and later blow off the shell into the interstellar space. The remaining core becomes a white dwarf.

Answer 2

A white dwarf star is the last stretch of a star's life.

At this point it's shrunk back from a red giant, and it's giving off less light and warmth than ever.

A white dwarf star is often quite small compared to other stars, hence the dwarf part and due to it giving up little heat and light it looks white, as the white half of it's name shows.

Answer 3

The black dwarf star forms by following a later stage via evolution from a "white dwarf."

Answer 4

when a small star dies