In stars similar to the Sun, what specific event characterizes the onset of stable core helium fusion?

Answer

A helium flash due to the core being degenerate

For stars like the Sun, the dense, degenerate helium core ignites explosively in what is termed a helium flash because pressure does not immediately respond to the rising temperature.

In stars similar to the Sun, what specific event characterizes the onset of stable core helium fusion?
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