APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 5431
Joined: Fri Dec 04, 2009 3:27 am

APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by APOD Robot » Tue Jan 02, 2024 5:05 am

Image Rocket Transits Rippling Moon

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.

<< Previous APOD This Day in APOD Next APOD >>

FLPhotoCatcher
Science Officer
Posts: 246
Joined: Wed Jul 18, 2012 6:51 am

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by FLPhotoCatcher » Tue Jan 02, 2024 6:31 am

I think the ripples are shock waves, and are not caused by "pockets of relatively hot or rarefied air deflecting moonlight less strongly than pockets of relatively cool or compressed air.."

Jim Leff
Science Officer
Posts: 193
Joined: Thu Dec 09, 2010 2:00 pm

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by Jim Leff » Tue Jan 02, 2024 11:34 am

Whether shock waves or heat, the unanswered question is whether it’s tied to the rocket launch, or some broader condition.

Lasse H
Ensign
Posts: 64
Joined: Mon Jul 30, 2007 4:11 pm
Location: Stockholm

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by Lasse H » Tue Jan 02, 2024 11:42 am

FLPhotoCatcher wrote: Tue Jan 02, 2024 6:31 am I think the ripples are shock waves, and are not caused by "pockets of relatively hot or rarefied air deflecting moonlight less strongly than pockets of relatively cool or compressed air.."
I agree. The given explanation sounds too fancifully conceived. What pockets? Where did they come from?

Elmar Schmidt

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by Elmar Schmidt » Tue Jan 02, 2024 2:42 pm

The moon also happens to show turquoise-green and reddish-orange rims, a known atmospheric phenomenon.

User avatar
johnnydeep
Commodore
Posts: 2980
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by johnnydeep » Tue Jan 02, 2024 2:57 pm

Right, the ultimate (distal) cause of the ripples is shockwaves from the exhaust, not hot or rarified air. The link from the text had this to say:
https://apod.nasa.gov/apod/ap221014.html wrote:Ripples and fringes along the edge of the lunar disk appear as supersonic shock waves generated by the rocket's passage change the atmosphere's index of refraction.
However, the shockwaves from the exhaust are just ripples of varying density in the air, which amounts to differences in the air's "rarifiedness", which is the proximate cause of the light's refraction, so I would argue that the text isn't entirely incorrect, just lacking in clarity.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

zendae1

Re: APOD: Rocket Transits Rippling Moon (2024 Jan 02)

Post by zendae1 » Tue Jan 02, 2024 10:19 pm

The spikiness on the left side starts at the 9:30, or 270+ position. I would hope the artificial explanations are being reviewed.