Filaments, vivid string-like regions, and sunspots, large blotches on the solar surface, appear dark. Filaments are common sources of eruptions. Filaments on the solar limb appear bright against the blackness of space and are called prominences. Dark splotches on the sun are sunspots. They are almost always seen in pairs and in groups of pairs.
Sunspots are dark because they are the coolest places on the sun.
The number of sunspots on the sun at any given time varies in an ll-year cycle as does the number and severity of disturbances in space weather. Constantly monitoring the development of sunspot groups is one important job of spaceweather forecasters. Prominences and filaments are really the same thing, but they look bright or dark depending on what is in the picture's background. The part on the face of the Sun is dark, those parts of the filament that show beyond the edge of the sun are bright. Filaments last for a few weeks or months.