Astronomy Picture of the Day

Explanation: Neptune, the Solar System's outermost gas giant planet, is 30 times further from the Sun than Earth. Twelve years after a 1977 launch, Voyager 2 flew by Neptune and found surprising activity on a planet that receives only 3 percent as much sunlight as Jupiter. In its brief but tantalizing close-up glimpse of this dim and distant world, the robot spacecraft recorded pulses of radio emission, zonal cloud bands, and large scale storm systems with up to 1500 mile per hour winds - the strongest measured on any planet. This mosaic of 5 Voyager images shows Neptune's Southern Hemisphere. Cloud bands and the Earth-sized, late "Great Dark Spot" with trailing white clouds located at about 22 degrees southern latitude are clearly visible. The distance from the Great Dark Spot feature to Neptune's South Pole (image center) is about 17,000 miles.

海王星是太陽系最外圍的氣態巨行星，與太陽的距離是地球的30倍之多。 在1977年發射的12年後，旅行者2號飛越了海王星，並在這顆接收到的陽光只有木星的3%之行星上，發現了令人驚訝的活動。 在它在對這個昏暗且遙遠的世界，短暫而誘人的近距離一瞥之中，這艘無人太空船記錄到無線電脈衝、雲帶及風速高達每小時2400公里的大型的風暴系統--這是在任何行星上測到的最強風速。 這幅由5張旅行者照片併接而成的影像，呈現了海王星的南半球。 在其中，雲帶和位於南緯22度附近、大小的地球相近、目前已消失的 "大暗斑 "，以及拖曳在後方的白雲皆清晰可見。 從大暗斑到海王星南極（影像中心）的距離，大約有27,000公里。