For star formation to occur, gravity must successfully overcome which combination of resistive forces?
Thermal pressure, rotational inertia, turbulent motion, and magnetic field tension.
Star formation requires a localized region of gas and dust to become dense enough to form a star, which means gravity must ultimately dominate the local dynamics. This dominance is only achieved when the inward gravitational attraction successfully overwhelms the sum of all opposing physical mechanisms acting within the cloud core. These resisting forces include the outward push from the kinetic energy of particles (thermal pressure), the outward counter-force generated by rotation (rotational inertia/centrifugal effects), the dynamic pressure exerted by chaotic internal flows (turbulence), and the elastic tension provided by compressed magnetic field lines (magnetic field tension). The successful overcoming of this combined resistance establishes the Jeans instability.
