Sunspots (Starspots)

Sunspots are cool, dark spots that appear on the sun's surface from time to time. Sunspots form in pairs that have opposite magnetic polarity and the areas where sunspots are most frequent are called active regions. The amount of acitivity that occurs varies from a solor minimum, at the beginning of a sunspot cycle, to a solar maxium around the five year mark. The size of a sunspot also varies because they expand and contract as they move across the sun's surface. Sunspots, however, are not just limited to the sun. Any star can develop these temporary spots on their surface.


History of Sunspots

The first surviving documented sunspot observations took place in China by an astronomer named Gan De in 364 BC. By 28 BC Chinese astronomers where keeping regular imperial records of sunspot cylces. The first mention of sunspots in Western literature was in 300 BC by

Theophrastus. Sunspots were mistaken for planetary transits until Galileo gave the proper explanation for the phenomenon in 1612.

Application of Sunspots

Since sunspots are related to other solar activites, the occurance of sunspots can help predict space weather, the state of the ionosphere, and because of that it can also help predict conditions of satellite communications.


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  3. Golub, Leon. Pasachoff, M. Jay. (2010) Sun. World Book Encyclopedia (Vol 18). Chicago: World Book, Inc.
  4. Picture from:
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