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Aurora borealis. Aurora borealis (northern lights) appearing over a frozen waterfall on Kirkjufell mountain, Iceland. The aurora borealis is a coloured light display that is visible in the night sky at high latitudes. It occurs when charged and energetic particles from the Sun (the solar wind) are drawn by Earth's magnetic field to the polar regions. Hundreds of kilometres up, they collide with gas molecules and atoms, causing them to emit light. Photographed on the Snaefellsnes peninsula, Iceland. (KEYSTONE/SCIENCE PHOTO LIBRARY/BABAK TAFRESHI/SCIENCE PHOTO LIBRARY)