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Definition of GEGENSCHEIN
: a faint light about 20° across on the celestial sphere opposite the sun probably caused by backscatter of sunlight by solar-system dust
Origin of GEGENSCHEIN
German, from gegen against, counter- + Schein shine
First Known Use: 1877
Oval patch of faint light exactly opposite the Sun in the night sky, so faint it can be seen only in the absence of moonlight, away from city lights, with the eyes adapted to darkness. It is lost in the light of the Milky Way except in February, March, April, August, September, and October. The gegenschein and the zodiacal light form the most notable parts of a band of very faint light along the ecliptic. Both phenomena are thought to be the result of the reflection of sunlight from interplanetary dust grains.