What force pushes outward from a star's core to precisely match the inward squeeze of its own gravity, keeping the star stable?

The force pushing outward from a star's core that precisely matches the inward squeeze of its own gravity is hydrostatic pressure. This pressure is generated by the extreme thermal energy produced by nuclear fusion reactions occurring deep within the star's core. Hydrostatic pressure is the outward force exerted by the hot gas and plasma within the star. Imagine countless particles, like atoms and electrons, moving at incredibly high speeds due to intense heat. As these rapidly moving particles collide with each other and push outward against their surroundings, they create this pressure. The source of this extreme thermal energy is nuclear fusion. In the star's core, under immense temperature and pressure, light atomic nuclei, primarily hydrogen, fuse together to form heavier nuclei, such as helium. This fusion process converts a small amount of mass into a tremendous amount of energy. This released energy intensely heats the core material, causing the particles within it to move with high kinetic energy. This vigorous motion of particles generates the significant outward hydrostatic pressure. This outward pressure then acts to counteract the relentless inward pull of the star's immense gravity. The precise balance between this outward hydrostatic pressure and the inward gravitational force is known as hydrostatic equilibrium, which is the condition that keeps a star stable and prevents it from either collapsing further or expanding indefinitely.