Why do white dwarfs stay hot for so long after a star dies?
Quick Answer
White dwarfs have no active fusion, so they cool only slowly by radiating stored heat. Because they are very dense and small, it can take billions of years for them to fade significantly.
The Full Story
A white dwarf is the compact remnant left behind by many stars after they shed their outer layers. It no longer produces energy by nuclear fusion, but it contains enormous stored heat from the star’s earlier life and collapse. Its small surface area means it loses energy gradually rather than quickly. The first white dwarf identified, Sirius B, was confirmed in the 19th century, and white dwarfs can remain detectable for billions of years.
Key Facts
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