通过月食可视化地球的影子

探索宇宙（universe）！每天都会精选一张关于我们迷人宇宙的不同图像或照片，并附上一段由专业天文学家（astronomer）撰写的简短说明。

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

说明：是什么在太空中制造了这个巨大的洞？这不是一个黑洞（black hole）——而是一个影子。这是地球（Earth）的影子。至少从亚里士多德时代起，人们就注意到地球在月偏食（partial lunar eclipse）期间投射在月球（Moon）上的暗影是圆形的——尽管从未呈现为一个完整的圆。然而，利用现代数字技术，可以将多次月食（lunar eclipse）的图像结合起来，以展示地球完整的影子。这张精选的图像合成作品由一位执着的天文摄影师制作，汇集了22年来的月食影像。月球并非每月都会发生食（eclipse），因为月球轨道（moon's orbit）相对于地球轨道有轻微的倾斜。仔细观察一些月食图像，可以看到一条微弱的蓝波段（blue band），这是因为地球大气层过滤掉了比蓝色更多的红色阳光。本周晚些时候，将发生一次新的月食，在北美洲、南美洲、欧洲和非洲的部分地区观测效果最佳。

Explanation: What’s creating this giant hole in space? This is not a black hole — it’s a shadow. It’s Earth’s shadow. Since at least the time of Aristotle, people have noted that Earth's dark shadow on the Moon during a partial lunar eclipse is circular -- although never a whole circle. Using modern digital technology, though, the images of multiple lunar eclipses can be combined to show Earth's complete shadow. The featured image compilation by a perseistent astrophotographer is constructed from 22 years of lunar eclipses. The Moon is not eclipsed every month (moon-th) because the Moon's orbit is slightly tilted relative to Earth's orbit. Close inspection of some lunar eclipse images shows a faint blue band where Earth’s atmosphere filters out more red sunlight than blue. Later this week, a new lunar eclipse will occur and will be best visible in parts of North and South America, Europe, and Africa.