Question

At which phase of its evolutionary life is a white dwarf star?

A) post-supernova phase, the central remnant of the explosion
B) just at main-sequence, or hydrogen-fusion, phase
C) very late for small-mass stars, in the dying phase
D) in its early phases, soon after formation

Answer 1

A white dwarf star is in the post-supernova phase, the central remnant of the explosion. It is composed mostly of carbon, oxygen, and neon. Over time, it cools off and becomes a black dwarf.

Step-by-step explanation:

A white dwarf star is in the post-supernova phase, which is the central remnant of the explosion. After the star consumes the little hydrogen remaining in its outer layers, nuclear fusion in its interior ceases, leading to the formation of a white dwarf. The white dwarf is composed mostly of carbon, oxygen, and neon, which are the products of the most advanced fusion reactions the star was capable of. Over time, the white dwarf cools off and becomes a black dwarf, a cold stellar corpse composed mainly of carbon, oxygen, and neon.