What state is achieved when outward energy pressure counteracts the inward crush of gravity?
Answer
Hydrostatic equilibrium
The hallmark of a stable, adult star residing on the main sequence is the delicate balance between the forces trying to compress it and the forces trying to expand it. Once nuclear fusion successfully ignites in the core, the resulting outpouring of energy generates a tremendous outward pressure. When this outward pressure perfectly balances the continuous, immense inward gravitational force exerted by the star's enormous mass, the star stops contracting. This state of perfect balance is known as hydrostatic equilibrium, signifying that the object has settled into a stable, constant size, ready to spend billions of years in its main sequence phase.
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