52.5 MB (10.4 MB compressed)
3770 x 4866 pixels
32.0 x 41.1 cm ⏐ 12.6 x 16.2 in (300dpi)
CHRIS MADELEY / SCIENCE PHOTO LIBRARY CHRIS MADELEY / SCIENCE PHOTO LIBRARY
Aurora borealis over a cabin. This coloured light display, also called the northern lights, is observed in the night sky at high latitudes. It occurs when charged and highly-energetic particles from the Sun (the solar wind) are drawn by Earth's magnetic field to the northern and southern polar regions. Hundreds of kilometres up, they collide with the upper atmosphere, causing the excitation of atoms and molecules which leads to the emission of light. Oxygen atoms (rather than molecules) are the most abundant components of the atmosphere at these heights. It is their excitation that results in green light. Photographed in March 2001, near Yellowknife, Northwestern Territories, Canada.
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