Question

A white dwarf star is supported from collapse under gravity by

A) pressure of the gas heated by nuclear fusion reactions in its core.
B) centrifugal force due to rapid rotation.
C) degenerate-electron pressure in the compact interior.
D) pressure of the gas heated by nuclear fusion reactions in a shell around its core.

Answer 1

A white dwarf star is supported by degenerate-electron pressure, not by nuclear fusion or rotation. This electron pressure is a result of the Pauli exclusion principle, counteracting the gravitational collapse until it cools into a black dwarf after many billions of years.

Step-by-step explanation:

A white dwarf star is supported from collapse under gravity by degenerate-electron pressure in the compact interior. This pressure arises because the electrons in a white dwarf resist being compressed into the same quantum state, in accordance with the Pauli exclusion principle. White dwarfs are the remaining cores of low-mass stars that have exhausted their nuclear fuel and have shed their outer layers. Although they can no longer produce energy through fusion in the core, some fusion may still occur in the surrounding shells until it ceases completely.

The dense core of the white dwarf is made up of a degenerate gas mostly consisting of carbon, oxygen, and neon. This core no longer supports fusion reactions but is instead stabilized by the pressure created by the degenerate electrons. As the white dwarf cools over billions of years, it will eventually become a black dwarf, a cold, dark stellar remnant.

Answer 2

A white dwarf is supported by degenerate-electron pressure in its compact interior. As a star exhausts nuclear fuel, gravity compresses it, but electron degeneracy pressure resists further collapse, providing stability without nuclear fusion or centrifugal force from rapid rotation. The correct option is C) degenerate-electron pressure in the compact interior.

Step-by-step explanation:

A white dwarf star is an endpoint in the life cycle of a star, primarily composed of electron-degenerate matter. As a massive star exhausts its nuclear fuel, it undergoes gravitational collapse.

The electrons in the star become degenerate, meaning they resist further compression due to the Pauli exclusion principle. This electron degeneracy pressure counteracts the gravitational force, preventing complete collapse.

Options A and D are not applicable to white dwarfs, as they pertain to different stages of stellar evolution, involving nuclear fusion reactions in the core or shell, which are not characteristic of white dwarfs. Option B is also not relevant, as rapid rotation isn't a primary factor in supporting white dwarfs against gravitational collapse.