A Granule

Linguistically

2. A tiny grain, a small particle.
3. (biology) A small structure in a cell.
4. (geology) A particle from 2 to 4 mm in diameter, following the Wentworth scale
5. (astronomy) a small mark in the photosphere of the sun caused by convection currents.

Astrophysics:

Granules

In solar astronomy, a granule refers to a small, cellular-like structure found on the Sun’s photosphere. Granules characterized by bright centers and darker boundaries. These features are associated with convective cells of hot, rising material (bright centers) surrounded by cooler, descending material (darker boundaries).

Granules are a manifestation of the Sun's convective activity, where hot plasma rises from the solar interior, reaches the surface, cools down, and then descends again. The constant motion of material in these convective cells creates the observable pattern of granules on the solar surface. Studying granules provides insights into the dynamics and structure of the Sun's outer layers.

Supergranules:

A supergranule is a large-scale pattern of solar convection cells on the surface of the Sun. It is an arrangement of granules, which are smaller convective cells, forming a network across the solar surface. Supergranules typically significantly larger than individual granules.

Similar to granules, supergranules are associated with the Sun's convective activity. The motion of hot, rising material in the center of the supergranules is surrounded by cooler, descending material at the edges. This convective flow contributes to the overall transport of energy from the Sun's interior to its outer layers.

The study of supergranules provides valuable information about the Sun's surface dynamics and plays a role in understanding the processes that govern solar activity and energy transport. Observations of supergranules are often made using techniques like Doppler imaging, which allows scientists to track the motion of material on the solar surface.