As an expert in astrophysics, I can tell you that the process of a white dwarf evolving into a black dwarf is a very long one, involving billions of years. White dwarfs are the remnants of stars that have exhausted their nuclear fuel and shed their outer layers. They are incredibly dense and hot, but they no longer undergo fusion reactions. Over time, they cool down and radiate their residual heat into space.

The cooling process for a white dwarf is extremely slow. It's estimated that it takes billions of years for a white dwarf to cool enough to become a black dwarf, which is essentially a cold, dark, and no longer luminous stellar remnant. At this point, the black dwarf would no longer emit significant amounts of energy and would be very difficult to detect.

It's important to note that the age of the universe is currently around 13.8 billion years, which means that **no white dwarfs have had time to cool down to become black dwarfs yet**. The oldest white dwarfs are still in the process of cooling and are not yet black dwarfs.

In summary, while the theoretical concept of a black dwarf is well-established in astrophysics, we do not currently have any observed examples of such objects because the timescales involved are so vast.

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The universe is only 13.7 billion years old, so even a white dwarf formed 13 billion years ago (unlikely; the stars which become white dwarfs take a billion years, or so, to do so) it would still have a temperature of a few thousand degrees.read more >>