Crescent Neptune and Triton
影像提供: Voyager 2, NASA
Explanation:
Gliding silently through the outer Solar System, the Voyager 2 spacecraft camera captured Neptune and Triton together in crescent phase in 1989. The above picture of the gas giant planet and its cloudy moon was taken from behind just after closest approach. It could not have been taken from Earth because Neptune never shows a crescent phase to sunward Earth. The unusual vantage point also robs Neptune of its familiar blue hue, as sunlight seen from here is scattered forward, and so is reddened like the setting Sun. Neptune is smaller but more massive than Uranus, has several dark rings, and emits more light than it receives from the Sun.
說明:
1989年，當航行家二號探測船靜靜地劃過太陽系外圍空間時，拍攝了上面這張彎如娥眉的海王星和海衛一影像。 拍攝這張照片時，航行家探測船剛通過最靠近海王星位置，繞到了這顆氣態巨行星和它雲霧瀰漫的衛星後方。 我們在地球看不到海王星的位相，因為地球較靠近太陽，從地球看出去，海王星永遠是全相。 從航行家特殊的拍照位置去看海王星，它熟悉的藍色色調不見了，因為陽光在透射過海王星的大氣時，藍光大多被散射掉了，透過來的只是會讓它看起來像是落日的紅光。 在太陽系的外行星中，海王星比天王星 小，不過質量反而比較大。海王星擁有數個暗黑色的行星環，另外，它輻射的熱量也比從太陽得到的要多。
資料來源: Scientific American
Department of Physics, NCKU
