Why does sun glow?

SCIENCE FACTS(Sun)

The Sun is the star at the center of the Solar System and composed of helium and hydrogen.Sunlight is the main source of energy for life on earth.Nuclear fusion at the core of the Sun produces an appreciable amount of thermal energy that makes the Sun glow.The interior of the Sun is radiative and nuclear fusion in the inner portions of the Sun has modified the composition by converting hydrogen into helium.The reactive core zone where hydrogen is converted into helium, is starting to surround the core of helium ash.This will continue and cause the sun to become red giant.This nuclear fusions produce thermal energy and that same energy reaches us as heat and light.Sunlight is mainly composed of infrared light,visible light and ultraviolet light.