sunspots
Original archive entry. The text, images and links below are kept as they were written.
Dark, irregular areas on the solar surface with strong magnetic fields (1000 to 2000 Gauss) surrounded by gray zones (penumbra). Sunspots occur mostly in pairs, with opposite magnetic polarity; they persist for periods of days, weeks, or months. Their temperatures are about 2000 K lower than the temperature of the surrounding photosphere (5780° K). The frequency of sunspots follows an eleven-year cycle.