What specific type of pressure eventually supports the contracting helium core of a Sun-like star before helium fusion ignites?
Answer
Electron degeneracy pressure
As the inert helium core contracts following hydrogen core exhaustion, gravity compresses the material intensely. Before the temperature is high enough for helium nuclei to overcome their mutual repulsion and begin fusing, the core becomes so incredibly dense that the atoms are packed tightly. At this point, the core's structure is maintained not by thermal pressure, but by electron degeneracy pressure. This is a quantum mechanical effect where electrons resist further compression, effectively providing a rigid, non-thermal scaffolding that supports the immense weight of the collapsing core until the critical ignition temperature for helium is finally reached.
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