What is the critical event that initiates the runaway gravitational collapse within a nebula?
Answer
The action of gravity successfully dominating the internal pressure within a slightly denser region
The process of star formation hinges on overcoming the initial near-equilibrium of the nebula. This is achieved not by a massive external event, but by exploiting pre-existing internal imperfections. Within the vast cloud, there are always small, random fluctuations in density—clumps that already possess slightly more mass concentrated locally. When gravity within one of these slightly over-dense regions becomes strong enough to overpower the weak outward pressure maintained by the sparse heat, it initiates a runaway contraction. This success marks the critical trigger for the entire collapse mechanism.
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