The outermost layer of the Sun is called the Corona. The Corona is the outermost part of the Sun`s atmosphere and is characterized by its extremely high temperature and low density. It is visible during a total solar eclipse as a faint, white, halo-like outer ring surrounding the darkened disc of the Moon. The Chromosphere, on the other hand, is the layer above the Photosphere and is characterized by its reddish glow during a solar eclipse. The Photosphere is the visible surface of the Sun and is the layer from which light is emitted. The Lithosphere, on the other hand, is not a part of the Sun but refers to the solid, outermost layer of rocky planets like Earth.