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Milky Way and night sky on a perfectly clear night, July 25, 2017, on the Canadian Prairies at Writing-on-Stone Provincial Park in Alberta, near the border looking south to the Sweetgrass Hills (West Butte) of Montana, USA. The Milk River, which flows into the Missouri River, winds below. The site is sacred to the Blackoot First Nations. The wooden buildings below are replicas of the late 1800s North West Mounted Police outpost in Police Coulee. Sagittarius and Scorpius are on the southern horizon, and Saturn is the bright object in the Dark Horse right of centre. The galactic centre is amid the bright star clouds above the horizon. The sky at left is green with natural airglow. The ground is illuminated only by starlight and airglow. (KEYSTONE/SCIENCE PHOTO LIBRARY/Alan Dyer/VWPics/SCIENCE PHOTO LIBRARY)