Why do sunspots appear dark?

Sunspots are actually several thousand degrees cooler than the 5,770 K (5496.8 °C) surface of the Sun, and contain gases at temperature of 3000 to 4000 K (2726.9 - 3726.8 °C). They are dark only by contrast with the much hotter solar surface. read more

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes. read more

Typical sunspots have a dark region (umbra) surrounded by a lighter region, the penumbra. While sunspots have a temperature of about 6300 °F (3482.2 °C), the surface of the sun which surrounds it has a temperature of 10,000 °F (5537.8 °C). read more

Once formed, the sunspots may last as briefly as a few hours or as long as a few months. Sunspots typically fluctuate through an 11-year cycle. Even though sunspots appear dark against the surface of the sun, the areas are still almost as bright as the full moon, and if moved away from the sun, they would be luminous. read more