Sunspots:

eHam.net News – Sunspots are dark areas on the surface of the Sun, formed where the magnetic field is particularly strong, blocking heat from rising to the surface. While the temperature of the Sun may be 6,000 degrees Celsius (about 11,000 degrees F), sunspots are about 1,500 degrees Celsius cooler. Sunspot activity may appear in 11-year cycles, and in some cases may be visible without the aid of telescopes.

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