The small bright convection cells on the Sun’s surface are called granules. They form in the photosphere, the visible layer of the Sun, where hot plasma rises from below, spreads outward, cools, and sinks around the cell’s edges.
A granule typically measures about 1,500 kilometres across. Its center appears brighter because rising plasma is hotter, while the surrounding lanes look darker because cooler material is descending. Together, millions of these cells create the Sun’s grainy or mottled appearance, known as granulation.
Granules are temporary features rather than permanent markings. Most survive for roughly 8 to 20 minutes before breaking apart and being replaced by new cells. At any given time, the Sun’s surface is covered by approximately four million granules.
They are easily confused with sunspots, prominences, and filaments, but those features have different origins and appearances. Sunspots are darker, magnetically active regions; prominences are arcs of plasma extending into the atmosphere; and filaments are prominences seen against the solar disk. Granules are primarily visible signs of convection beneath the photosphere.