Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2023 December 30
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The Persistence of Moonlight
Image Credit & Copyright: Giacomo Venturin

Explanation: Known to some in the northern hemisphere as December's Cold Moon or the Long Night Moon, the last full moon of 2023 is rising in this surreal mountain and skyscape. The Daliesque scene was captured in a single exposure with a camera and long telephoto lens near Monte Grappa, Italy. The full moon is not melting, though. Its stretched and distorted appearance near the horizon is caused as refraction along the line of sight changes and creates shifting images or mirages of the bright lunar disk. The changes in atmospheric refraction correspond to atmospheric layers with sharply different temperatures and densities. Other effects of atmospheric refraction produced by the long sight-line to this full moon rising include the thin red rim seen faintly on the distorted lower edge of the Moon and a thin green rim along the top.

Tomorrow's picture: Illustris

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