2025年9月11日
The Umbra of Earth
Image Credit & Copyright: Wang Letian (Eyes at Night)
Explanation: The dark, inner shadow of planet Earth is called the umbra. Shaped like a cone extending into space, it has a circular cross section most easily seen during a lunar eclipse. And on the night of September 7/8 the Full Moon passed near the center of Earth’s umbral cone, entertaining eclipse watchers around much of our fair planet, including parts of Antarctica, Australia, Asia, Europe, and Africa. Recorded from Zhangjiakou City, China, this timelapse composite image uses successive pictures from the total lunar eclipse, progressing left to right, to reveal the curved cross-section of the umbral shadow sliding across the Moon. Sunlight scattered by the atmosphere into Earth’s umbra causes the lunar surface to appear reddened during totality. But close to the umbra’s edge, the limb of the eclipsed Moon shows a distinct blue hue. The blue eclipsed moonlight originates as rays of sunlight pass through layers high in the upper stratosphere, colored by ozone that scatters red light and transmits blue. In the total phase of this leisurely lunar eclipse, the Moon was completely within the Earth’s umbra for about 83 minutes.
Tomorrow’s picture: a tale of two hemispheres
地球的本影
影像提供与版权: Wang Letian (Eyes at Night)
说明: 地球黑暗的内影区被称为「本影」（umbra）。它呈现一个向太空延伸的圆锥状，其截面是圆形，最容易在月全蚀时被观察到。而在9月7日和8日的夜晚，满月正好通过地球本影锥的中心附近，为南极洲、澳洲、亚洲、欧洲与非洲等广大地区的观测者带来了一场精彩的天象。这张由中国张家口市拍摄的缩时合成影像，将月全蚀过程中连续的照片自左至右排列，清晰呈现出本影截面的弧形轮廓滑过月球的景象。当太阳光经由地球大气层散射后进入本影区，月球表面便在全蚀期间呈现暗红色。然而，在本影边缘附近，月球边缘则显露出明显的蓝色光晕。这股蓝色的蚀中月光，源自阳光穿过高层平流层时，臭氧对红光的散射与对蓝光的透射所造成的效果。在这次节奏悠缓的月全蚀中，月球完全位于地球本影之内的时间长达约83分钟。
明日的图片: a tale of two hemispheres
