Sunspot and Solar "granules" (detail mgnf)

Caption NASA originale:"Sometimes, small regions of the Sun appear unusually dark. Visible above is a close-up picture of a sunspot, a depression on the Sun's face that is slightly cooler and less luminous than the rest of the Sun. Sunspots can be larger than the Earth and usually last for only a few days. As you can see, the Sun's face is a bubbling sea of separate cells of hot gas. These cells are known as "granules" and a solar "granule" is about 1000 Km across and "lives" for + or - 10 minutes, then explodes".