hottest part of the Sun is its core. The surface of the Sun is a mere 5,800 Kelvin, while the center of the Sun is around 15 million Kelvin. That's hot. Although the surface of the Sun is relatively cool, the corona can get much hotter
The core, or middle, of the Sun is the hottest part. Hot gasses bubble up from the core to the surface of the Sun. When the gasses burn, heat and light are produced.
