Does the sun have a surface?
Nope….it’s like a big nuclear explosion being held together by it’s own gravity. But instead of splitting atoms like in nuclear weapons it is fusing them together to make heavier elements. The sun is about 75% hydrogen and about 24% helium with 1% of its mass comprising other gases. Four hydrogen atoms fuse together under intense heat and pressure to create 1 helium atom. Even if the core was a solid surface such as iron…then the nuclear fusion would stop and the sun would contract in to an extremely dense ball of gas. But the sun will never have a core of iron. The suns life will end after it fuses helium in to carbon and oxygen during it’s red giant stage. Then at this point the sun will contract to the size of the earth and become a white-dwarf. Radiating away intense heat but undergoing no fusion. Scientists know what matter makes up the sun with the use of a spectrometer. Basically what a spectrometer does is measures the wavelengths of light from the sun. And from this inform