Understanding the Chandrasekhar Limit in Stars

The Chandrasekhar limit is the maximum mass a star can have at the end of its life to form a stable white dwarf. In simpler terms, it is a cosmic “weight limit” for stars.

The Cosmic Balance Act

Stars exist in a constant tug-of-war. Gravity pulls the star's matter inward, trying to collapse it, while energy from nuclear fusion pushes outward, resisting gravity. This balance keeps a star stable for the majority of its life.

The End of a Star's Life

When a star like our Sun exhausts its nuclear fuel, gravity takes over. The star sheds its outer layers, and its core collapses into a tiny, extremely dense object called a white dwarf. Without fusion pressure, a different force called electron degeneracy pressure prevents electrons from being squeezed too closely together — a quantum effect analogous to the “no two things can occupy the same space” principle.

The Tipping Point

The Chandrasekhar limit, approximately 1.4 times the mass of the Sun, represents the threshold where gravity becomes too strong for electron degeneracy pressure to resist.

• If the core's mass is below the limit: Electron degeneracy pressure is sufficient to resist gravity, and the star becomes a stable white dwarf.
• If the core's mass exceeds the limit: Gravity overpowers the electron degeneracy pressure, causing the white dwarf to collapse into a denser object, such as a neutron star or, in extreme cases, a black hole.

This principle is essential for understanding the final fate of stars and explains why not all dead stars end up as white dwarfs.