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"Star trails around the North Star. The point of light at the centre of the image is Polaris, also known as the North Star or alpha Ursa Minoris. The rotation of the Earth about an axis toward Polaris has caused these star trails to record during a 15-minute exposure time. The further the star is from Polaris in the sky, the longer the trail it describes. Different colourations of the stars show up best toward the edges of the frame; red stars and blue stars are clearly visible. Polaris itself is a pale yellow supergiant, about 200 parsecs (650 light years) from Earth. As it is located about one degree from the north celestial pole, all the other stars appear to circle it." (KEYSTONE/SCIENCE PHOTO LIBRARY/JOHN SANFORD)