Star trails. Time exposure photograph of star trails in the southern night sky. Star trails are lines of light made by the relative movement of the stars through the night sky as the Earth rotates. The trails reveal the variety of colours and brightnesses of the stars in the sky. In the southern hemisphere the star trails form concentric circles centred on the South Celestial Pole, the point in the sky which lies directly above South Pole. Photographed over Lake Titicaca in South America, during June.