What bets explains why the sun maintains its size and shape?

The sun maintains its size and shape due to a balance between gravitational forces and the pressure generated by nuclear fusion in its core. Gravitational forces pull the sun's mass inward, while the energy produced from nuclear fusion reactions converts hydrogen into helium, creating outward pressure that counteracts gravity. This equilibrium, known as hydrostatic equilibrium, ensures that the sun remains stable in size and shape over long periods. If either force were to change significantly, the sun would undergo structural changes, such as swelling into a red giant or collapsing into a denser state.