What fundamental difference distinguishes the initiating force of a Type Ia event from a Type II event?

Answer

Thermonuclear runaway versus gravitational collapse

Type Ia events are initiated by a thermonuclear runaway in the white dwarf core, whereas Type II events are initiated by a catastrophic gravitational collapse of an iron core.

What fundamental difference distinguishes the initiating force of a Type Ia event from a Type II event?
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