Rossiter–McLaughlin effect

The Rossiter–McLaughlin effect is an astrophysical phenomenon observed during transits of exoplanets, specifically when a planet passes in front of its host star from our viewpoint. This effect occurs because the planet partially blocks the star's light and causes a distortion in the Doppler shift of the star's light as seen from Earth. When a planet transits, it blocks different parts of the star's surface as it moves across it.