Wilson effect

In astronomy, the Wilson effect is the perceived depression of a sunspot's umbra, or center, in the Sun's photosphere. The magnitude of the depression for the umbra is between 500 and 1000 km, with an average of 600 km.

This article is about the Wilson effect in astronomy. For the unrelated effect in psychometrics research, see Heritability of IQ.

Sunspots result from the blockage of convective heat transport by intense magnetic fields. Sunspots are cooler than the rest of the photosphere, with effective temperatures of about 4,000°C (about 7,000°F). Sunspot occurrence follows an approximately 11-year period known as the solar cycle, discovered by Heinrich Schwabe in the 19th century.

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