How Stars Die

A star's death depends on its mass.

Low-Mass Stars (Less than 8 Solar Masses)

When hydrogen fuel runs low, the core contracts and heats up while outer layers expand and cool:

• The star becomes a red giant - huge and luminous but with a cooler surface.
• Eventually the outer layers drift away as a planetary nebula.
• The exposed core becomes a white dwarf - Earth-sized but with the Sun's mass.

White dwarfs slowly cool over billions of years. They no longer fuse elements but shine from residual heat.

High-Mass Stars (More than 8 Solar Masses)

Massive stars live fast and die young:

• They become red supergiants and fuse increasingly heavy elements in their cores.
• When the core turns to iron, fusion stops - iron fusion consumes energy rather than releasing it.
• The core collapses in milliseconds, triggering a supernova explosion.
• The explosion outshines entire galaxies briefly and creates elements heavier than iron.

Neutron Stars and Black Holes

• Neutron stars - If the remaining core is 1.4-3 solar masses, it becomes a city-sized ball of neutrons.
• Black holes - If the core exceeds 3 solar masses, gravity overwhelms all forces, creating a singularity.