What external events often serve as triggers for compressing diffuse gas into star-forming molecular clouds?

Answer

Shock waves generated by supernovae explosions or passing spiral density waves.

Compression of the diffuse interstellar medium, leading to cloud formation, is often initiated by external dynamic events, such as shock fronts from massive star deaths or density waves moving through the galactic disk.

What external events often serve as triggers for compressing diffuse gas into star-forming molecular clouds?
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