The lower plot shows the number of sunspots as a function of time - they peak about every 11 years or so. In the last 100 years the period of rise has ranged between 3.3 and 5.0 years and the period of fall between 5.7 and 8.3 years, so it is difficult to make predictions over any length of time. These disturbed regions are seen as dark markings on the Sun's surface. The life of a sunspot can be as short as a few hours or as long as several months. Some are seen over several revolutions of the Sun about its axis and in such cases are actually observed for only about half their duration, because for 13 or 14 days of the 27 day revolution they are on the hemisphere facing away from the Earth.
Sunspots can occur singly and in groups and they can be of very different sizes.
Large sunspots are sometimes visible to the naked eye when seen through fog or when the Sun is dim and red at sunrise or sunset. At other times the disk is too bright to be looked at directly. Sunspots with areas of only one millionth represent the other end of the scale. The Photosphere, Chromosphere and Corona. The apparent disk of the Sun is called the photosphere .