Gegenschein (German for counterglow) is a faint brightening of the night sky in the region of the zodiac directly opposite the Sun caused by reflection of sunlight by small dust particles that lie in the plane of the Solar system. It appears as a softly glowing oval region a few degrees wide and 10-15° in length, oriented along the plane of the ecliptic. It is so faint that it cannot be seen if there is any moonlight or if it falls in the vicinity of the Milky Way.
The gegenschein was discovered in 1854 by the Danish astronomer Theodor Brorsen.
The gegenschein is one of several skyglows that also include the zodiacal light and the zodiacal band .
See Optical phenomenon.