Facial Blemishes on the Sun

When the Sun is viewed through a solar telescope dark spots can be observed on the surface. These continuously changing dark regions are called Sunspots. The spots appear dark to the eye because they are cooler than the surrounding gas although they are still quite hot! The photosphere has a temperature of about 5800 degrees Kelvin and a typical Sunspot has a temperature about 3500 degrees Kelvin.

The inner part of a Sunspot is very dark and is called the umbra, the Greek word for shadow. The lighter region surrounding the umbra is known as the penumbra. A good view of the umbra and the penumbra can be seen in the granulation photo from the previous page.

A Sunspot's life can be as short as an hour or two or as long as several months. The number of Sunspots that can be seen on the surface of the Sun increases and decreases in a regular pattern, known as the solar cycle, with a maximum number of Sunspots occurring every 11 years.


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