What physical condition defines the threshold for gravitational dominance and subsequent collapse in a molecular cloud region?
Answer
When a region's mass is greater than its local Jeans mass
The initial phase of star formation hinges on overcoming the internal forces resisting collapse, such as gas pressure and turbulence. This critical threshold condition is quantitatively defined by the Jeans mass. If a specific region within the molecular cloud possesses a total mass that exceeds its local Jeans mass threshold, the overwhelming force of gravity will inevitably dominate the existing outward pressures. This dominance ensures that the clump begins a rapid contraction, initiating the pathway toward becoming a star. If the mass remains below this critical value, the internal pressure and turbulence are sufficient to keep the gas dispersed.
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