John Evershed discovered that the light coming from one side of sunspot penumbrae is shifted to the blue, whereas the light from the opposide side is shifted to the red. This phenomenon is known as the Evershed effect.
Don't miss the story of the Eversheds at Kodaikanal Solar Observatory in the third episode of the cartoons video series: "The QuEST for Sunspot Dynamics"
See https://tinyurl.com/TheQuESTseries for more information.
