I know next to nothing about the sun but I think the article implies that it’s because of convection currents—closer to the center, plasma heats up and expands, rises, cools off, and falls back in. The picture looks vaguely like a Voronoi diagram too, which sort of fits as the plasma has to spread out of its own hot plume before sinking.
Close. The Sun is not a fully convective star. Convection only occurs in the outer 30% or so. The inner part is called the radiation zone [1] and it is here that energy from fusion in the core makes its way out by radiative transfer as well as conduction. This is a very slow process compared to convection, taking more than 170,000 years for the photos produced by fusion to reach the convection zone.
Wouldn’t we be observing the outer 30% (or 1%) though? From the diagram on the page you linked it seems that the granules in the photo exist in the photosphere, where convection is the dominant mode of energy transfer. That said, none of the conduction could happen without radiation further inside.
Yeah, we’re seeing the convection from the outer 30%, bubbling up on the surface of the photosphere. All of the fusion takes place down in the core though. It’s very difficult to fuse hydrogen and so it can only occur at the extreme pressures in the middle of the sun.
