The Sun Is a Giant Ball of Fire

Nothing on the Sun is burning, because burning is a chemical reaction that needs oxygen, and space has essentially none. The Sun shines through nuclear fusion: in its core, under crushing pressure and temperatures around 15 million degrees Celsius, hydrogen nuclei are squeezed together to form helium, and that reaction releases staggering amounts of energy. It is the same basic process as a hydrogen bomb, running continuously and held together by the Sun's own gravity, not a campfire scaled up. The distinction matters because fire and fusion are completely different beasts. A fire consumes fuel and oxygen and makes ash. Fusion converts a tiny bit of mass directly into energy and could keep the Sun going for billions of years. So it is not burning. It is a controlled, gravity-bound nuclear furnace pretending, very convincingly, to be a fireball.