A Giant Starspot on HD 12545 . ... Credit Copyright: K. Strassmeier ( U. Wien ), Coude Feed Telescope , AURA , NOAO , NSF Explanation: What could cause a star to have such a large spot? Our Sun itself frequently has sunspots , relatively cool dark magnetic depressions that move across its surface. ... The starspot is thought to be caused by large magnetic fields that inhibit hot matter from flowing to the surface. ... NASA Web Site Statements, Warnings, and Disclaimers . ...