Question

How does a white dwarf generate its energy?

A) It no longer generates energy but is slowly cooling as it radiates away its heat.
B) Nuclear fusion of hydrogen into helium is producing energy in its core.
C) Nuclear fission of heavy elements in the central core is releasing energy.
D) Gravitational potential energy is released as the star slowly contracts.

Answer 1

A white dwarf no longer generates energy and slowly cools as it radiates away its stored heat, eventually becoming a black dwarf, a cold, non-luminous stellar remnant.

Step-by-step explanation:

The correct answer to the question is A) It no longer generates energy but is slowly cooling as it radiates away its heat. Since a stable white dwarf can no longer contract or produce energy through fusion, its only energy source is the heat represented by the motions of the atomic nuclei in its interior. The light it emits comes from this internal stored heat, which is substantial. Gradually, however, the white dwarf radiates away all its heat into space.

After many billions of years, the nuclei will be moving much more slowly, and the white dwarf will no longer shine. It will then be a black dwarf-a cold stellar corpse with the mass of a star and the size of a planet, composed mostly of carbon, oxygen, and neon, the products of the most advanced fusion reactions of which the star was capable.