Astronomy Picture of the Day

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.

2023 October 25

Gone in 60 Seconds: A Green Flash Sunset
Video Credit & Copyright: Tengyu Cai

Explanation: In 60 seconds, this setting Sun will turn green. Actually, the top of the Sun already appears not only green, but wavey -- along with all of its edges. The Sun itself is unchanged -- both effects are caused by looking along hot and cold layers in Earth's atmosphere. The unusual color is known as a green flash and occurs because these atmospheric layers not only shift background images but disperse colors into slightly different directions, like a prism. The featured video was captured earlier this month off the coast of Hawaii, USA. After waiting those 60 seconds, at the video's end, the upper part of the Sun seems to hover alone in space, while turning not only green, but blue. Then suddenly, the Sun appears to shrink to nothing -- only to return tomorrow.

Tomorrow's picture: 1P/Halley


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