At approximately what core temperature, supported by degeneracy pressure, does helium fusion ignite explosively in a Sun-like star?
Answer
About 100 million Kelvin
The initiation of helium fusion marks a highly specific, critical threshold in the evolution of a Sun-like star. While the core is supported by electron degeneracy pressure, it continues to contract and heat up dramatically under gravity, even though it cannot expand to self-regulate the temperature. When the core finally attains a temperature of approximately 100 million Kelvin, the kinetic energy of the helium nuclei is sufficient to overcome the repulsive barrier, leading to the sudden ignition of helium into carbon and oxygen. This temperature landmark is precisely what dictates the timing of the dramatic event known as the Helium Flash.
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