The sun has five distinct layers: the core, solar envelope, photosphere, chromosphere and corona. Unlike the Earth, the sun has no solid features, as it is too hot for them to persist. All of the sun's layers are either in the gaseous or plasma state.
The core of the sun is the hottest part, and it is what provides the power for the star. Inside the core, a massive fusion reaction is taking place. The reaction smashes hydrogen atoms together and converts them into helium. This type of reaction can only happen at great temperatures and pressures, and the core of the sun is approximately 27 million degrees Fahrenheit. Such pressures are provided by the solar envelope, which surrounds the core. However, the solar envelope is much cooler than the core and averages about 7 million degrees Fahrenheit. Outside of the solar envelope, which is very large and contains about 90 percent of the sun’s volume, the photosphere is a much thinner layer. The photosphere is the part of the sun that produces the visible light. Immediately outside the photosphere, the chromosphere is full of hydrogen and imparts the red color during eclipses. Finally, the corona is the outer layer, which is only visible during eclipses. The corona sometimes reaches 3 million degrees Fahrenheit.