Because of its proximity to us the sun is the only star that astronomers can observe and research in detail. The study of events on the surface of the sun has made possible advances in atomic, nuclear and plasma physics. Observations of the sun's surface, also called the photosphere, with special filters show an ever changing surface punctuated by the appearances of sunspots, faculae, flares and protuberances. The sun exhibits differing rotational periods of between 24 and 34 days depending on the solar latitude. All surface phenomena rotate accordingly.
Sunspots are cooler areas in the photosphere produced by local changes in the magnetic field.
Sunspots tend to occur in groups and are combined with other phenomena of solar activity such as faculae, filaments and flares. Although sunspots have an average temperature of 3700K they appear dark compared to the brighter surrounding regions which have an approx. The development of the different phenomena proceed at varing rates. Larger sunspot groups tend to consist of two larger magnetically linked spots surrounded by smaller spots. This is a typical 'bipolar' group.