天王星上的极端天气（图）

When NASA's Voyager 2 probe flew past Uranus in 1986, the seventh planet looked like a featureless blue-green ball. But new images from the W. M. Keck Observatory in Hawaii reveal Uranus as a stormy, dynamic world. The false-color infrared shots above capture Uranus’s -360-degree Fahrenheit cloud tops over consecutive nights in July, with brighter colors representing higher-altitude methane clouds. 

These are the most detailed views of Uranus ever taken from Earth. Astronomers are puzzled by the scalloped band of low-lying clouds (left of the planet’s center) and the small storms (bright blotches at right) dotting the northern polar region. Further observations at Keck should help explain why the weather on Uranus is so active even though the sunlight there is just 1/900th as strong as on Earth.

 这些是从地球拍摄的最为详细的天王星图片。天文学家们对于扇贝纹形的低云层区（该行星中部左侧）和点缀在北极区域的小型风暴带（右侧的亮斑）感到迷惑不解。尽管天王星上的阳光强度仅为地球上的1/900，但是凯克天文台的进一步观测应该有助于解释为什么那里的天气如此活跃。