Why is the sun a mass of incandescent gas?

The sun is a mass of incandescent gas primarily because it is composed mostly of hydrogen and helium, which exist in a plasma state due to the extreme temperatures and pressures in its core. This process of nuclear fusion converts hydrogen into helium, releasing vast amounts of energy that heats the outer layers, causing them to glow incandescently. The intense energy and heat result in the sun's characteristic brightness and the emission of light across the electromagnetic spectrum.