What is this rainbow ring?

[Nereid]

Today's Astronomy Picture of the Day (http://antwrp.gsfc.nasa.gov/apod/ap040913.html) is a photograph showing a rainbow ring, inside of which is a bright region. APOD also carries a challenge - what is the explanation for sequence of colours and the bright region?

Surprisingly, lots of bright students, knowledgable teachers - even the APOD editors - apparently haven't got it (yet).

[LURCH]

I have a challenge of my own; what is a picture of some wet pavement doing in the "Astronomy Picture of the Day" spot?

[sol2]

I have a challenge of my own; what is a picture of some wet pavement doing in the "Astronomy Picture of the Day" spot?

Probably trying to create the background :rofl:

[bino]

have you ever seen a rainbow ring around the moon?
it is pretty cool looking.

[BobG]

All rainbows are circles. You just can't see the bottom half when you're on the ground. You sometimes can from an airplane, however.

If you think about, it only makes sense that the proper angle for a rainbow would form a circle. The light's refraction into colors depends on the angle between the Sun, the water droplets, and you. Since the Sun is so far away and much bigger than the Earth, it's light comes from the same angle regardless (i.e. - the light rays are parallel). So the only variable is the angle between you and the water droplets in the air.

[chroot]

I have the distinct feeling this picture has something to do with a lunar or solar eclipse. I'm still trying to figure it out, though.

- Warren

[jcsd]

My guess is that it's the camera flash being refracted by the surface.

[cronxeh]

my guess is refraction due to difference in medium.. perhaps an oil spill there.. or just water or whatever.

Edit: in fact now that i think about it.. i think all the colors added up on the lenses and caused the white in the middle.. while the outer pattern is caused by refraction and red having the longest wavelenght is outside and blueish colors are inside the circle

Edit #2: aha i got it.. i think its a cloud! light refracted by a cloud :biggrin:


here is my own pictures of something nifty:

http://www.silentserenity.com/IMG_0001.jpg

http://www.silentserenity.com/IMG_0002.jpg

[BobG]

No it can't be the camera's flash.

No, because the person's shadow wouldn't block the camera's flash.

But, thinking about your answer does make me think the picture is of a wet wall instead of wet pavement. With the Sun behind you, you wouldn't see its reflection on the pavement in front of you.

Edit: In fact, it's not the Sun and the wall's not wet at all.

[sol2]

I thought it should be specifically about not how the rings are made in the photograph( it's used as a analogy) but of what they mean(the rings)?

I had a post up top that through better clarifcation supports my position, and considers Apod's current pictures. My journal spells this out, for further clarification.

Thanks for the space and time in this thread.......auf Wiedersehn :smile:

[LURCH]

No it can't be the camera's flash.

No, because the person's shadow wouldn't block the camera's flash.

But, thinking about your answer does make me think the picture is of a wet wall instead of wet pavement. With the Sun behind you, you wouldn't see its reflection on the pavement in front of you.

You do see a ring like that whenever you look at wet pavement or from a high mountaintop, look down at clouds with the Sun behind you. The effect when viewed by hikers in the mountains is called a "glory" (http://www.chemtrailcentral.com/ubb/Forum5/HTML/000309.html) and has been photographed from aircraft, (http://www.polarization.com/rainbow/glory.html) as well. I see it all the time when I walk alongside the river in my hometown (http://www.wordiq.com/definition/Image:Blue_Water_Bridge.jpg) .

[chroot]

I was thinking this was a glory -- I've seen them while flying, also -- but I couldn't figure out why the center was brighter than the rest. I still can't. Do all glories have bright centers?

- Warren