What external occurrences can act as triggers to initiate gravitational instability in a molecular cloud?

Answer

Shockwaves from a nearby supernova explosion.

Star formation often begins when external disturbances compress regions within a turbulent molecular cloud, increasing local density enough to overcome thermal pressure, such as those generated by nearby supernovae.

What external occurrences can act as triggers to initiate gravitational instability in a molecular cloud?

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