Why does helium ignition cause an explosive Helium Flash in low-mass stars?

Answer

Because the pressure is independent of temperature, fusion surges without immediate cooling regulation.

Since pressure in a degenerate core does not depend on temperature, the sudden surge in energy from fusion causes a runaway reaction that only moderates once enough heat is generated for thermal pressure to eventually overcome degeneracy.

Why does helium ignition cause an explosive Helium Flash in low-mass stars?

#Videos

Chaos in the Cosmos: How Stars Burn Helium and Evolve - YouTube

Ask John: How do stars burn? - YouTube

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