Associated with strong magnetic fields, they are 1500 Kelvin cooler than the surrounding photosphere.
Johannes Fabricius was the first to publish a book on these entities, which are caused by strong radial vortical fields. Rudolf Wolf is the namesake of a quantity that measures the number of these objects. The periodic variation of their positions is given by Sp?rer's law, according to which they follow an 11-year cycle. There was a low number of them between 1645 and 1715, which is referred to as the Maunder Minimum. Associated with strong magnetic fields, they are 1500 Kelvin cooler than the surrounding photosphere. FTP, name these dark patches that appear on the surface of the sun.
Johannes Fabricius was the first to publish a book on these entities, which are caused by strong radial vortical fields.
sunspots