Photosphere

The photosphere is the visible surface of a star (optical wavelengths), and in particular the Sun.

The solar photosphere, located above the convection zone and below the chromosphere, emits most of the solar radiation. It is a layer about 300 km thick at a temperature of the order of 5800 K, which rotates in a complex way.

Sunspots and faculae (hot bright regions) are phenomena that can be observed on the photosphere. The sunspots appear dark because they are cooler than their environment on the photosphere. They are the sites of intense magnetic fields. The convection motion of rising hot gas and falling cool gas causes a network of small cells (granules) to form, each of a size of the order of a thousand kilometres. The photosphere sometimes emits spicules, thin jets of gas that rise up into the solar chromosphere for a few minutes, following the lines of force of the magnetic field.

During eclipses the photosphere is occulted, and the corona can be observed.