This means that the spectrum of the photosphere will be an absorption-line spectrum . In the photosphere, we find granules . These are dark light spots with dark rims that are about the size of Texas. They are caused by convection in the sun s atmosphere. Convection is what happens to boiling water in a pot on the stove.
Water heated by the burner rises to the surface of the water, then cools and falls.
The reason that the middle is brighter than the edge is that the middle is hotter and therefore emits more strongly. We also see sunspots, or dark spots on the photosphere. These are quite cool compared to the sun s surface. We will talk about them more when we talk about solar activity. The Chromosphere is the thin layer of hot gas between the photosphere and the corona.