In a starry winter night of Sweden mountains near the border with Norway, an aurora streak appears in the northern sky near Ursa Major. Stars of the constellation Gemini and Orion rise on the other side but more special are passing Nacreous Clouds some 20 kilometers above the photographer. Polar stratospheric clouds, also known as nacreous clouds, form during the winter in the stratosphere above polar regions, at altitudes of 15 – 25 km. They are rare and appear bright with vivid and slowly shifting colors within two hours after sunset or before dawn. But here they are captured in the darkness of night when the clouds no longer receive direct sunlight but still detectable. Click on the second photo to see a closer view of Orion and Taurus over this beautiful winter landscape. © P-M Heden



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