What physical condition must a localized region of gas achieve to begin gravitational collapse into a protostar?

Answer

Its mass must exceed the Jeans mass defined for its specific temperature and pressure.

Star formation initiation requires that a specific, dense pocket of gas accumulates enough mass relative to its size so that its self-gravity overcomes the outward thermal pressure, a threshold quantified as the Jeans mass.

What physical condition must a localized region of gas achieve to begin gravitational collapse into a protostar?
starscosmologynebulastar formationastrophysics