white-dwarfs

When the Sun dies, it will leave behind a white dwarf — a city-sized object containing half the Sun's mass, supported not by nuclear fusion but by quantum mechanics. White dwarfs are already the most common stellar remnants in the galaxy, and every star you see in the night sky under 8 solar masses will eventually become one. Some will detonate as the universe's most reliable distance markers. Others will crystallize into diamond-like spheres and cool for trillions of years.

The Chandrasekhar limit, about 1.44 solar masses, is the heaviest a white dwarf can be before electron degeneracy pressure fails. It shapes Type Ia supernovae, cosmic distance measurements, and which stellar remnants become white dwarfs, neutron stars, or black holes.

Cataclysmic variables are close binary stars in which a white dwarf pulls gas off a companion. The result is outbursts that range from dwarf novae flaring every few weeks to classical novae that brighten by up to a million times. This article explains the physics, the period gap, and the famous systems.

Stars don't burn out quietly. Depending on their mass, they end their lives as cooling embers, supernova explosions, neutron stars, or black holes. Here's what actually happens.