What is a white dwarf?
Last updated Jun 24, 2026
Correct Answer:
Option A —
It is a stellar core which remains after the star has used up all of its nuclear fuel.
Understanding White DwarfsA White Dwarf represents one of the final stages of stellar evolution for stars that are not massive enough to become neutron stars or black holes (stars like our Sun).
Formation: When a medium-sized star exhausts its nuclear fuel (hydrogen and helium), it sheds its outer layers, creating a planetary nebula. The remaining hot, dense core is the white dwarf.
Composition: They are typically composed of carbon and oxygen. Because they are no longer performing nuclear fusion, they don't produce new heat; instead, they gradually cool down over billions of years.
Density: They are incredibly dense. A white dwarf has a mass comparable to the Sun but a volume comparable to Earth.
Support: They are prevented from collapsing further by electron degeneracy pressure, a quantum mechanical effect that prevents electrons from being squeezed into the same space.
Analysis of Other Options
B) Explosion of a star: This describes a Supernova.
C) Highly compact, magnetized, rotating stars: This describes Pulsars (a type of neutron star).
D) Extremely luminous active galactic nucleus: This describes a Quasar.
Answer verified by Quintessence Classes faculty — Karan Nagar, Srinagar.
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