Chandrasekhar Limit
The maximum mass of a stable white dwarf.
Formula
Variables
Example
A white dwarf heavier than ~1.44 suns collapses, triggering a supernova
How it works
The Chandrasekhar limit is the largest mass a white dwarf can have before electron degeneracy pressure can no longer support it against gravity. It comes from balancing gravity, which tries to compress the star, against quantum mechanical pressure from tightly packed electrons; as the star gets more massive, the electrons must move faster, and once they become highly relativistic, the supporting pressure no longer increases fast enough. That is why the limiting mass is about 1.44 times the mass of the Sun for an ideal carbon-oxygen white dwarf.
When to use it
Use this when you need to decide whether a compact stellar remnant can remain a white dwarf or must collapse further. It is especially relevant in stellar evolution, Type Ia supernova models, and problems involving degenerate matter in astrophysics.
Worked example, step by step
Suppose a white dwarf has a mass of 1.30 M_\odot. Step 1: Write the Chandrasekhar limit: M_{Ch} \approx 1.44 M_\odot Step 2: Compare the star’s mass to the limit: 1.30 M_\odot < 1.44 M_\odot Step 3: Find how much below the limit it is: 1.44 - 1.30 = 0.14 M_\odot Step 4: Conclusion: this white dwarf is stable against collapse by electron degeneracy pressure, since its mass is below the Chandrasekhar limit.
Common mistakes to avoid
- Thinking the limit applies to any star, instead of specifically to white dwarfs supported by electron degeneracy pressure
- Using the limit as an exact universal constant for all white dwarfs, when composition and rotation can shift the value slightly
- Confusing the Chandrasekhar limit with the point where a star becomes a neutron star, which is a later collapse stage after the white dwarf limit is exceeded
Did You Know?
Chandrasekhar worked this out at just 19 during his boat voyage to England; it earned him a Nobel Prize decades later in 1983.
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