The number of sunspots increases until it reaches its maximum amount, which occurs every half of a solar cycle or eleven years. Sunspots usually have a dark central region called the umbra. This is the coolest area of the sunspot. The umbra is surrounded by a slightly lighter area referred to as the penumbra. Small sunspots are known as pores.
Some pores have an umbra but no penumbra.
The umbra can be from three to ten times darker than the sun's surface. The umbra may be up to 3,600 degrees Fahrenheit cooler than the sun itself.