Final answer:
Hydrostatic equilibrium is the critical state in stars such as the Sun, where internal pressures balance the inward gravitational pull, preventing the star from collapsing. This balance is achieved with a central temperature high enough to sustain nuclear fusion.
Step-by-step explanation:
The condition in a star or other fluid body where gravity's inward pull is exactly balanced by internal forces due to pressure is known as hydrostatic equilibrium. This balance ensures that the Sun, and any stable star, remains stable and does not collapse under its own gravity. The core of the Sun must remain at a high temperature of approximately 15 million K to exert sufficient pressure to counterbalance the gravitational force. This high temperature enables the fusion of protons, which is crucial for the Sun to continue shining without collapsing or expanding excessively.
The technical term hydrostatic equilibrium can also be likened to an inflated balloon that expands or contracts until equilibrium is reached between the air pressure inside and outside. The pressure at every internal point in stable stars equals the weight of the stellar layers above, creating a stable, balanced condition.