Let's observe sunspots.

Most of the surface of the Sun has a temperature of about 5400 degrees C, but in a big sunspot the temperature can drop to about 4000 degrees C.

He also discovered sunspots, the dark areas of the Sun. He saw that the planet Venus has light and dark phases just like the Moon. These discoveries provided empirical information that proved that the Sun is at the center of the Solar System, as Nicholas Copernicus had predicted.

The sun is currently in a period of low activity but even so large sunspots occasionally appear.

Sunspots are regions of the Sun where the solar magnetic field is very strong.

Sunspots appear darker than their surroundings because they are a few thousand degrees cooler.