Schematic illustration showing the surface features and internal structure of the Sun. The Sun's interior consists of a core, a radioactive zone, a convective layer and, finally, the visible 'surface' - the photosphere. Many features are visible on the surface and in the solar atmosphere. Spicules are jet-like gas flows extending vertically upwards, all over the Sun. The photosphere is not smooth, but rather has a granulated appearance - the grains mark the boundaries of rising cells of gas, carrying heat to the surface by convection. Sunspots are also a prominent feature of the photosphere - they can be as big as the Earth (top left). Finally, flares (left) and prominences (right) are eruptions of gas related to magnetic activity