Sunspots appear where powerful magnetic fields breech the surface of the sun.
The presumed reason sunspots are cooler and darker than the rest of the Sun is because the magnetic field blocks the Sun's heat transport mechanism. If this is true the blocked heat must escape somewhere and theoretically should appear as a bright ring around the sunspot. Having not been previously observed, their absence has been explained by heat dispersal deep in the turbulent solar interior. Using the Precision Solar Photometric Telescope at the National Center for Atmospheric Research Mauna Loa Solar Observatory, researchers found bright rings around eight sunspots. Larger spots had hotter, brighter rings.