The Gegenschein Over Chile
			
		
		
			Image Credit & Copyright:  
Yuri Beletsky
(ESO)
		
		
			Is the night sky darkest in the direction opposite the Sun?
No.  In fact, a rarely discernable faint glow known as 
the gegenschein (German for "counter glow") can be seen 180 
degrees around from the Sun in an extremely dark sky.
The gegenschein is sunlight back-scattered off small interplanetary
dust particles.  
These dust particles are millimeter sized splinters from 
asteroids and orbit in the 
ecliptic plane of the planets. 
Pictured above from 2008 October is one of the more spectacular pictures of 
the gegenschein yet taken.
Here a deep exposure of an extremely dark sky over 
Paranal Observatory in 
Chile shows 
the gegenschein so clearly that even a surrounding glow is visible.   
In the foreground are several of the 
European Southern Observatory's
Very Large Telescopes, 
while notable background objects include the 
Andromeda galaxy toward the lower left and the 
Pleiades star cluster just above the horizon.  
The gegenschein 
is distinguished from zodiacal light near the Sun by the 
high angle of reflection.  
During the day, a phenomenon similar to 
the gegenschein called the glory can 
be seen in reflecting air or clouds opposite the Sun from an airplane.