What mechanism causes thermal pressure to dramatically slow gravitational contraction in a dense core?

Answer

The interior becoming opaque, trapping thermal energy and causing pressure to surge.

As the cloud fragment compresses, it becomes opaque to its own generated photons. This trapping of gravitational energy converted to heat causes the internal temperature and resulting thermal pressure to surge, directly opposing gravity.

What mechanism causes thermal pressure to dramatically slow gravitational contraction in a dense core?
gravitystar formationpressurecollapseinterstellar cloud