Starship Asterisk*

An Airglow Fan from Lake to Sky

Explanation: Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured last summer next to Bryce Canyon in Utah, USA. The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.

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That is so very cool!!!

Maybe a "fan" because of the wide angle???

Cool to see M31...just from a camera....

:---[===] *

Am I correct that this was taken with a wide angle lens?
So that the 'rim' of the 'fan' is the Milky Way?
And that in reality, this view would have looked completely different?

And, "gravity waves"? Obvioulsy not relativistic ones, or the photographer, Dave Lane, would be in line for a Nobel.
But atmospheric waves, the same as 'mountain waves' that generate the lenticular clouds that look like flying saucers, that have previously featured on APOD? Gravity atmospheric waves seem to be different in that they occur on in parallel, whereas mountain waves are linear.

Loads of pictures online, but usually over peaks, or as single clouds. You don't need a high mountain! In warm summer weather a north wind over the Cumbrian fells can set off squadrons of lenticulars over Morecambe Bay.

John

John,

Actually the image is 36 images stitched together from N-NW to S-SW. Its stitched in a 6x6 matrix with a 35mm lens. Its interesting to note that several other images taken that night with a main direction of south showed the banding horizontal (with some distortion) so a very strong correlation to east west banding. I've had two nights of very intense airglow both after storms left the area with a lot of lightning activity.

I am curious if this contributed to the strength of the airglow.

Dave

Thank you, Dave - the photographer, I take it?

Did it look like a fan that night? The lateral compression that has bent the Milky Way into a bow must have exagerrated that.
As to the effects that influenced the formation of the waves, how high up is the banding? The pressure will be at ground/sea level, but the chemoluminescece? Much, much higher, I suspect. Higher than storm clouds?

John, so ignorant as to be a speculator!

The coral waves like an Elkorn Fan from Sea to Sky too.
Beautiful APOD!!

JohnD

Yes I am the photographer thought I'd stop in and say hey! Plus if anyone has questions I'll be glad to answer them.

On the airglow, it's sad our eyes are not sensitive enough to see the great color. That night it looked like streams of really high faint clouds. I thought it was till I looked in the camera and went holy mother of god! On my Facebook page I dropped the brightness a bit (sort of like the overlay did) and the colors really popped then. In person it looked like an odd streaming mistiness.

I really thought it was left over clouds from the storm that had gone through.

Dave

JohnD wrote:And, "gravity waves"? Obvioulsy not relativistic ones, or the photographer, Dave Lane, would be in line for a Nobel.

Indeed, we have to be careful to distinguish between gravity waves typically observed in clouds and airglow, and gravitational waves produced by moving masses, and currently being searched for by LIGO and other sophisticated experiments. The similarity in terms is unfortunate.

If anyone has an interest in how the image was put together I put together a short timeline of the processing.
http://www.davelaneastrophotography.com/187-2/

drlane wrote:If anyone has an interest in how the image was put together I put together a short timeline of the processing.
http://www.davelaneastrophotography.com/187-2/

Very informative! Thanks!

It's fanning out because of the interaction with sunlight perhaps?

How long is an airglow visible for? As opposed to auroras only lasting a few seconds? Can airglows be seen anywhere? It's so pretty

hihadley wrote:It's fanning out because of the interaction with sunlight perhaps?

How long is an airglow visible for? As opposed to auroras only lasting a few seconds? Can airglows be seen anywhere? It's so pretty :shock:

The main reason it appears like a fan is because you are seeing a vanishing point. The actual structure consists of largely parallel bands. Airglow is present everywhere, all the time. It is usually uniform, and therefore goes unnoticed. When gravity waves provide contrast structure, it becomes more obvious. (Auroras are frequently visible for many minutes, even hours.)

How is it that the Milkyway Galaxy, which is a fairly flat disc, appears as an arc?

R Melton wrote:How is it that the Milkyway Galaxy, which is a fairly flat disc, appears as an arc?

Take a look at David's processing steps page:
http://www.davelaneastrophotography.com/187-2/

Note that before he straightens out the horizon, it's also arcing, and you know the horizon is flat. It's what happens when you take a wide field of view and try to turn it into a flat rectangle.

I rest my case! It is true, "that in reality, this view would have looked completely different". (My post above)
Our Galaxy is not a arc in the sky, but a straight band. When you are lucky enough to have Dark Skies.

With respect to Dave who is an artist holding up a mirror to reality, this distorting mirror has given us a beautiful image, but not one that he or anyone else saw. No bad thing - we can't see the colours of nebulae either.

John

JohnD wrote:I rest my case! It is true, "that in reality, this view would have looked completely different". (My post above)
Our Galaxy is not a arc in the sky, but a straight band. When you are lucky enough to have Dark Skies.

With respect to Dave who is an artist holding up a mirror to reality, this distorting mirror has given us a beautiful image, but not one that he or anyone else saw. No bad thing - we can't see the colours of nebulae either.

John

If humans were capable of seeing such a wide field of view, perhaps with eyes in the sides of our heads, we could indeed witness this view. As it is, we have to turn our heads to take it all in. It is not a distorted image. But an image with a straight galactic plane and a curved horizon isn't distorted either, in my opinion. There are many ways to look at the sky.

JohnD wrote:I rest my case! It is true, "that in reality, this view would have looked completely different". (My post above)
Our Galaxy is not a arc in the sky, but a straight band.

No, it isn't. Just standing outside under the Milky Way you are likely to see it as an arc, because our natural inclination is to interpret an outdoor view with a straight horizon (of course, it also forms an arc on our retina). When our brain normalizes the horizon to straight, it sees the Milky Way as curved. And even when the Milky Way is straight overhead, we view it by arcing our head from one horizon, over the zenith, to the opposite horizon, and our brain tells us that the Milky Way is a huge arch over our heads, not a straight band.

The projection required for a wide field image does, in fact, come close to capturing the projection used by our brain in viewing such a scene. The primary way that the image enhances the scene is by capturing more light than our eyes are capable of, bringing out contrast and color that would be lost to our eyes alone. Of course, virtually all astronomical images do just that- it's their purpose!

It's a gorgeous image. Where I am even on a clear night it can be hard to spot any more than the brightest of stars.

Thanks to Judy for the annotation . I must be getting good (award myself a smilie) as I managed to spot what I thought might be Andromeda before I saw the annotation!