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.

2008 May 7
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

The Gegenschein Over Chile
Credit & Copyright: Yuri Beletsky (ESO)

Explanation: 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 millimetre sized splinters from asteroids and orbit in the ecliptic plane of the planets. Pictured above from last October is one of the most 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.

Tomorrow's picture: to the Dark Tower

< | Archive | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.