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How are sunspots formed?

Why are sunspots created? What is the reason behind them?

Sunspots appear darker than the rest of the surface of the Sun because they are cooler. The center of a sunspot (called the umbra) has a temperature of around 3700 Kelvin while the surrounding photosphere has a temperature of 5800 Kelvin. Sunspots are also regions of strong magnetic fields (thousands times stronger than the Earth's field) and usually occur in pairs (one being a north pole and the other being a south pole).

Why certain regions on the Sun's surface are cooler than others is not well understood. One theory is that the strong magnetic fields in these spots inhibit convection below the surface. (Convection is the transfer of heat from a hot location to a cold one.)

April 2006, Sabrina Stierwalt (more by Sabrina Stierwalt) (Like this Answer)

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