This image may not be used by or to promote the arms, nuclear power or tobacco industries or any religious organisation, or in any discriminatory way, or to imply the endorsement by ESO of any product, service or activity Illustration showing a comparison between sunspots on the Sun (left) and spots on extreme horizontal branch stars (right). Both sunspots and spots on extreme horizontal branch stars are caused by magnetic fields. However, the spots on extreme horizontal branch stars are brighter than their surrounding stellar surface whilst sunspots are cooler than their surroundings. The spots on the extreme horizontal branch stars are much brighter and larger than sunspots. Sunspots are approximately 3000 times smaller than giant spots on extreme horizontal branch stars.