Closeup of a Sunspot, taken by Inouye Solar Telescope
The smallest features are about 20km in size, and the darkest area is cooler than the surrounding surface, but at 4,150′c still incredibly hot.
Sunspots occur when the magnetic fields of the sun become twisted and contorted causing knots that hold back the upwelling of plasma below it, reducing the surface temperature below them temporarily.
The sun isn’t alone in this phenomena, “Star Spots” are common and have been observed by Kepler telescope occurring on other stars. Red Dwarfs and Red Giant stars are particularly partial to them, making the star what is termed “Variable” in some cases, as much as 40% of the total brightness of the star is lost to these huge magnetic fields occurring on the star.
Source : http://www.sci-news.com/astronomy/inouye-solar-telescope-first-image-sunspot-09125.html
