Stability of Stars

Hydrostatic Equilibrium: A star remains stable in its main sequence phase due to a condition known as hydrostatic equilibrium. This is a balance between two main forces:
- Gravitational Force is an inward pull caused by the mass of the star compressing it towards its centre.
- Radiation Pressure is an outward push resulting from the energy produced in the core of the star due to nuclear fusion.
Energy Source: The main source of a star’s energy is from nuclear fusion that occurs in the core. The most common fusion process is the conversion of hydrogen into helium.
The Role of Fusion: The fusion process releases a huge amount of energy in the form of radiation pressure, countering the force of gravity. This prevents the star from collapsing under its own weight.
Change in Equilibrium: As a star exhausts its hydrogen fuel, the equilibrium is altered. This leads to different stages in the star’s life cycle such as red giant or supernova phases, depending on the star’s mass.
End of Stability: Once a star has exhausted all of its nuclear fuel, it cannot maintain its equilibrium. This results in collapse; small stars will often form a white dwarf, while larger stars may produce a neutron star or black hole.