The Chandrasekhar limit, approximately 1.4 times the mass of the Sun, is a fundamental threshold in stellar evolution that determines the ultimate fate of a dying star. It marks the maximum mass a white dwarf—the dense remnant of a star—can have while remaining stable.
When a star exhausts its nuclear fuel, it can no longer support itself against gravitational collapse through fusion. If the remaining core has a mass less than about 1.4 solar masses, electron degeneracy pressure (a quantum mechanical effect that arises due to the Pauli Exclusion Principle) is sufficient to hold up the star, and it becomes a white dwarf.
However, if the core’s mass exceeds the Chandrasekhar limit, electron degeneracy pressure is not enough to counteract gravity. In this case, the star continues to collapse:
- It may become a neutron star, supported by neutron degeneracy pressure, or
- If massive enough, collapse further into a black hole.
The limit was first calculated in 1930 by Subrahmanyan Chandrasekhar, an Indian astrophysicist, when he was just 19 years old. His groundbreaking work was initially controversial but later earned him the Nobel Prize in Physics in 1983.
Key implications of the Chandrasekhar limit:
- Defines the boundary between stable white dwarfs and more exotic remnants,
- Explains the cause of Type Ia supernovae, which occur when a white dwarf accretes mass beyond this limit,
- Plays a critical role in understanding the life cycles of stars and the chemical enrichment of galaxies.