The dark spots on the sunīs surface are called sunspots.
In the wikipedia, a free web encyclopedia, sunspots are explained as folows:
"A sunspot is a region on the Sun's surface (photosphere) that is
marked by a lower temperature than its surroundings, and intense
magnetic activity. Although they are blindingly bright, at
temperatures of roughly 5000 K, the contrast with the surrounding
material at some 6000 K leaves them clearly visible as dark spots.
Interestingly, if they were isolated from the surrounding photosphere
they would be brighter than an electric arc."
( http://en.wikipedia.org/wiki/Sunspot )
The phenomenon has been discovered a long time ago by the chinese:
"Apparent references to sunspots were made by Chinese astronomers in
28 BC, who probably could see the largest spot groups when the sun's
glare was filtered by wind-borne dust from the various central Asian
( same source )
Sunspots show a structure and are divided into two parts:
"When viewed through a telescope, sunspots have a dark central region
known as the umbra, surrounded by a somewhat lighter region called the
( http://scienceworld.wolfram.com/astronomy/Sunspot.html )
I hope this helps to solve your problem.
- I visited of the wikipedia webpage and used the internal serach function there