2025年2月1日
Nacreous Clouds over Sweden
Image Credit & Copyright: Vojan Höfer
Explanation: Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from northern Sweden. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured in this snapshot on January 12 with the Sun just below the local horizon. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds diffract the sunlight even when the Sun itself is hidden from direct view.
Tomorrow’s picture: comet disintegrates
瑞典上空的夜光云
影像提供与版权: Vojan Höfer
说明: 鲜艳色彩夺目的波状虹彩云，漂流在瑞典北部的天空中。这种名为夜光云或贝母云的高层云，相当罕见。然而，这幅1月12日拍摄时，太阳已位于当地的地平线下方的影像，就记录了它们令人难以忘怀的绚丽身影。夜光云是一种极地平流层云，其成因通常是在无云的天空中，下平流层里的水汽因异常低温而形成冰晶所致。因此，緃然太阳已然隐没在地平线下方，而高悬在约15至25公里高空的夜光云，仍然在衍射阳光。
明日的图片: comet disintegrates
