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.

2000 April 9
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

Mysterious Pluto and Charon
Credit: . W. Buie (Lowell Observatory), D. J. Tholen (U. Hawaii), and K. Horne (St. Andrews)

Explanation: Pluto is the only planet in our Solar System remaining unphotographed by a passing spacecraft. Distant Pluto and its moon Charon therefore remain somewhat mysterious. In addition to direct imaging by the Hubble Space Telescope, careful tracking of brightness changes that occur as each object eclipses the other have allowed astronomers to build up the above black & white surface maps. These maps depict the face of Pluto (left) that always faces Charon, and the face of Charon that always faces away from Pluto. The rectangular pixels are an artifact of the mapping software. The Pluto-Kuiper Express mission is tentatively planned for launch in 2004 and might encounter Pluto as early as 2012.

Tomorrow's picture: An Unusual Aurora

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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.