As an expert in astrophysics, I can explain the process of how a white dwarf evolves into a black dwarf.

A white dwarf is the remnant of a low- to medium-mass star that has exhausted its nuclear fuel and shed its outer layers, leaving behind a dense core composed mostly of carbon and oxygen. This core is incredibly dense, with a mass comparable to that of the Sun but a volume similar to that of Earth. White dwarfs are very hot when they first form, with surface temperatures reaching up to 100,000 Kelvin, and they emit most of their energy in the form of ultraviolet light.

Over time, white dwarfs cool down as they radiate their residual heat into space. This cooling process is extremely slow, taking billions of years. As the white dwarf cools, its temperature decreases, and it eventually becomes too cold to emit significant amounts of light. At this point, the white dwarf will have transitioned into a black dwarf.

A black dwarf is a theoretical celestial object that has not yet been observed because the universe is not old enough for any white dwarf to have cooled to that state. The transition from a white dwarf to a black dwarf is a gradual process with no distinct event marking the change. It is simply the end state of a white dwarf's long cooling period.

It's important to note that white dwarfs can undergo a process called a type Ia supernova if they accrete enough mass from a companion star. This is a catastrophic event that completely destroys the white dwarf and does not lead to the formation of a black dwarf.

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Eventually��over tens or even hundreds of billions of years��a white dwarf cools until it becomes a black dwarf, which emits no energy. Because the universe's oldest stars are only 10 billion to 20 billion years old there are no known black dwarfs��yet. ... Stars like our sun fuse hydrogen in their cores into helium.read more >>