| Sunspots appear darker than the rest of the visible
solar surface because they are cooler. Most of the visible surface
of our Sun has a temperature of about 5400 C, but in a large sunspot
the temperature can drop to about 4000 C. They usually come in sizes between
about 2500 km and about 50,000 km. The temperature of the visible
surface of Etoile has been calculated to be approximately 3000 C.
The larger sunspots there may have a temperature of 2000 to 2500
C.
Approximate temperature (for Sun):
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