Final answer:
Hydrostatic equilibrium in stars refers to the balance of temperature and pressure. In the Sun, this balance prevents collapse and maintains stability. Fusion reactions occur in the core due to the high temperature and pressure.
Step-by-step explanation:
Hydrostatic equilibrium refers to the balance of temperature and pressure in a star. In the case of the Sun, the inward force of gravity is balanced at each point by the outward force of gas pressure, which creates a state of equilibrium. This balance prevents the star from collapsing or expanding.
An example of hydrostatic equilibrium can be seen in the Sun's core, where the high temperature and pressure allow hydrogen atoms to undergo fusion and release energy.