Astronomy Picture of the Day - Rainbow Airglow over the Azores

APOD.NASA.gov ^ | 18 Apr, 2021 | Image Credit & Copyright: Miguel Claro (TWAN); Rollover Annotation: Judy Schmidt

[MtnClimber]

Explanation: Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water. The long-duration exposure nearly along the vertical walls of airglow likely made the undulating structure particularly visible. OK, but where do the colors originate? The deep red glow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun. The orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up. The featured image was captured during a climb up Mount Pico in the Azores of Portugal. Ground lights originate from the island of Faial in the Atlantic Ocean. A spectacular sky is visible through this banded airglow, with the central band of our Milky Way Galaxy running up the image center, and M31, the Andromeda Galaxy, visible near the top left.

[MtnClimber]

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[MtnClimber]

[MtnClimber]

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[MtnClimber]

Pinging the APOD list.

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Roll your cursor over the image at the link for graphics identifying features in the image.

[Ken522]

So gravity waves are running perpendicular to the axis of the Milky Way?? Does that follow the right-hand rule?

[MtnClimber]

I don’t know who wrote that. Gravity waves? It is atmospheric pressure waves.

[steve86]

“Gravity waves”? Those are the province of LIGO.

[MtnClimber]

Yep!

[dayglored]

Just want to say "Thank You!" for these marvelous APOD threads. As an amateur astronomy fan for the past 60+ years, I find them to be such a treat and an uplifting source of joy at the wonders of God's Creation.

I don't comment on them often, but rest assured I see every one. Have a great evening and God Bless.

[MtnClimber]

Thank you for your kind words. I learn too.

God bless.

[Verginius Rufus]

Behind him lay the gray Azores,
Behind the Gates of Hercules;
Before him not the ghost of shores,
Before him only shoreless seas.
The good mate said: "Now we must pray,
For lo! the very stars are gone.
Brave Adm'r'l speak; what shall I say?"
"Why, say: 'Sail on! sail on! and on!'"

Joaquin Miller, "Columbus"

(Perhaps the good mate misunderstood the admiral--maybe he was saying "Ceylon! Ceylon!")

[DannyTN]

The pot if gold at the end of that must be spectacular!

[dsrtsage]

“ I don’t know who wrote that. Gravity waves? It is atmospheric pressure waves.”

That was a joke

[BradyLS]

“From Ushant to Chantilly is thirty-five leagues...”