The outermost layer of the Sun and many other stars: A corona of tenuous and hot gas (estimated to be approximately 2,000,000°C or 3,600,000°F) exists around the Sun, which boils from the surface.

The coroma of the Sun is visible at solar eclipses, or through a coronagraph, an instrument that blocks light from the Sun's brilliant disk.

Gas flows away from the corona to form the solar wind.