Sunspots are dark, planet-sized regions that appear on the 'surface' of the sun . Sunspots are dark because they are colder than the areas around them.A large sunspot might have a temperature of about 4000K ( 3700 C ) ,This is much lower than the 5500 C temperature of the bright photosphere that surrounds the sunspots.
The largest sunspots observed have had diameters of about 60000 km, which makes them large enough to be seen with the naked eye. Sunspots often come in groups with as many as 100 in a group, though sunspot groups with more than about 10 are relatively rare. There are well established methods for measuring the number of sunspots.
Sunspots are only dark in contrast to the bright face of the sun. If you could cut an average sunspot out of the sun and place it in the night sky, it would be about as bright as a full moon. Sunspots have a lighter outer section called the penumbra, and a darker middle region named the umbra.
Sunspots are caused by the Sun's magnetic field welling up to the photosphere, the Sun's visible "Surface" The powerful magnetic fields around sunspots produce active region on the Sun., which often lead to solar flares and Coronal Mass Ejections. the solar activity of flares and Coronal Mass Ejections are called " solar storms"
Our sun is not the only star with spots. astronomers have been able to detect " starspots" , " sunspots" on other stars.
sunspots are observed with land-based and Earth-orbiting solar telescopes. These telescopes use filtration and projection techniques for direct observation, in addition various types of filtered cameras. Specialized tools such as spectroscopes and spectrohelioscopes are used to examine sunspots and sunspot areas. Artificial eclipses allow viewing of the circumference of the sun as sunspots rotate through the horizon.
