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.

2001 August 27
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Artificial Night Sky Brightness
Credit & Copyright: P. Cinzano et al., DMSP Satellites, RAS

Explanation: Where have all the dim stars gone? From many places on the Earth including major cities, the night sky has been reduced from a fascinating display of hundreds of stars to a diffuse glow through which only a handful of stars are visible. The above map indicates the relative amount of light pollution that occurs across the Earth. The cause of the pollution is artificial light reflecting off molecules and aerosols in the atmosphere. Parts of the Eastern United States and Western Europe coloured red have an artificial night sky glow over nine times that of the natural sky. In any area marked orange or red, the central band of our Milky Way Galaxy is no longer visible. The International Dark Sky Association suggests common types of fixtures that provide relatively little amounts of light pollution.

Tomorrow's picture: The Jagged Hills of Callisto

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.