The Sun and Stars
The Sun is a star around which the Earth and other planets of the Solar System orbit. Like any star, the Sun is a glowing ball of hot ionised gas or plasma. The light and heat the Sun generates comes from nuclear reactions inside the Sun’s core. These reactions mainly involve the fusion of hydrogen into helium. As a result the Sun generates a tremendous outward pressure that is balanced by the inward pull of the Sun’s gravity, holding the star in a near spherical shape. This state is known as ‘hydrostatic equilibrium’ and stars spend most of their lives in this state.