Astronomy Picture of the Day

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 2003 and should encounter Pluto around the year 2012.

冥王星是太陽系裡，唯一尚未由路過的太空船拍照之行星。 因此，遙遠的冥王星和其衛星冥衛一仍然頗為神秘。 除了哈伯太空望遠鏡的直接成像外，仔細跟踪它們彼此交食之時，所產生的亮度變化，讓天文學家得以建構出上面這種黑白表面圖。 這些地圖呈現冥王星始終面對冥衛一的正面（左），以及冥衛一始終背對冥王星的一面。 矩形的像素則是繪圖軟體的產物。 冥王星-柯伊伯帶快車號任務，暫訂於2003年發射，預計在2012年左右接近冥王星。