March 20, 2007
The cosmos has been expanding since the beginning of time, making room for galaxies, for stars, for planets — and ultimately, for you.
A Blue Crescent Moon from Space
Birthday · March 20, 2007
A little universe, just for you
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APOD published March 20, 2007. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
What's happening to the Moon? Drifting around the Earth in 2006 July, astronauts from the International Space Station (ISS) captured a crescent Moon floating far beyond the horizon. The captured above image is interesting because part of the Moon appears blue, and because part of the moon appears missing. Both effects are created by the Earth's atmosphere. Air molecules more efficiently scatter increasingly blue light, making the clear day sky blue for ground observers, and the horizon blue for astronauts. Besides reflecting sunlight, these atmospheric molecules also deflect moonlight, making the lower part of the moon appear to fade away. As one looks higher in the photograph, the increasingly thin atmosphere appears to fade to black.