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.

2024 January 2
A rocket is pictured ascending during launch. 
A nearly full moon is behind it. The rocket exhaust,
itself visible, causes the bottom of the Moon to appear
unusually rippled.
Please see the explanation for more detailed information.

Rocket Transits Rippling Moon
Image Credit & Copyright: Steven Madow

Explanation: Can a rocket make the Moon ripple? No, but it can make a background moon appear wavy. The rocket, in this case, was a SpaceX Falcon Heavy that blasted off from NASA's Kennedy Space Center last week. In the featured launch picture, the rocket's exhaust plume glows beyond its projection onto the distant, rising, and nearly full moon. Oddly, the Moon's lower edge shows unusual drip-like ripples. The Moon itself, far in the distance, was really unchanged. The physical cause of these apparent ripples was pockets of relatively hot or rarefied air deflecting moonlight less strongly than pockets of relatively cool or compressed air: refraction. Although the shot was planned, the timing of the launch had to be just right for the rocket to be transiting the Moon during this single exposure.

Tomorrow's picture: red sky arc

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