What external forces can initiate the gravitational collapse of a giant molecular cloud?

Answer

Shockwave from a nearby supernova explosion

The initial triggering event for star formation involves an external force, such as the shockwave from a supernova or pressure from nearby massive stars, overcoming the cloud's internal thermal pressure.

What external forces can initiate the gravitational collapse of a giant molecular cloud?
protostarstellar evolutionstar formationastrophysics