the.com/sunspot

means A temporarily darker, cooler region on the sun's surface caused by intense magnetic activity that blocks heat from rising to the surface.

from Straightforward compound of 'sun' plus 'spot' — astronomers have watched these dark blemishes drift across the solar face since at least the early 1600s, when observers using the new telescope noticed them and tracked their movement to prove the sun itself rotates. The name is almost disappointingly literal: it's a spot, on the sun.