What is the primary mechanism that allows gravitational instability to set in locally within a larger, seemingly stable cloud?

Answer

Small, dense pockets are individually massive enough to exceed their local Jeans mass.

Gravitational instability is often local; a massive cloud can host smaller regions that are dense enough that their individual mass surpasses the local Jeans mass threshold, initiating independent collapse even if the average cloud structure is stable.

What is the primary mechanism that allows gravitational instability to set in locally within a larger, seemingly stable cloud?
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