The Photosphere

Granulation is an effect visible in the photosphere that is a result of convection cells rising out of the convection zone below. Granulation appears as a mixture of small light and dark spots. The above image clearly shows the granulation pattern, and in the bottom right points out a single granule and intergranular lane. As convection cells rise in the convection zone, they get smaller and smaller. At the edge of the convection zone, only very small convection cells are left- and where these tiny cells of hot gas break the surface (photosphere) we see a small bright dot. In areas around the cells, the gas has cooled and appears darker- giving rise to the granulation effect. Energy released in these bright granules originated in the core of the star from the fusion reaction, and may have taken tens of millions of years to escape to the surface where it can finally radiate out into space.

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