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What colour will planetary rings made up of dust and rock (not ice) appear to be? Would there be a difference looking from space and from the surface?

More importantly, how will the rings affect the colour of the sky? Eg during sunrise, sunset, sun behind or reflecting off the rings.

I'm asking for an

  • earth sized planet, with a similar oxygen rich atmosphere. Ie in goldilocks zone
  • Rings would be made up of dust and rock particles, not ice. Ie Not a gas giant with rings made up of ice and dust.
  • Yellow to orange sun.

I believe the sky will normally be in the shades of blue/indigo/purple due to scattering light. But I'm wondering what shades the sky will go when the rings interact with the light.

If this all 'depends', is there any method of working it out for each situation?

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  • $\begingroup$ Just wondering, but why don't they contain any ice? Or do you simply mean miniscule amounts compared to anything else? $\endgroup$ – dot_Sp0T Sep 26 '16 at 11:59
  • $\begingroup$ Too close to the sun. If there is any ice, it's only in the shadow of the planet...or as you said, miniscule amounts when compared to a scaled down version of Saturn's rings. $\endgroup$ – EveryBitHelps Sep 26 '16 at 12:00
  • $\begingroup$ There is beatiful link to help you visualize it. $\endgroup$ – Mustafa Yılmaz Sep 26 '16 at 12:05
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You are correct that the answer is "it depends", what I can tell you though is what it depends on.

The first thing to consider is your atmosphere. What light frequencies (colours) does it reflect? Which ones get through to the surface? Our atmosphere lets visible light through, which is one reason our eyes are tuned to those frequencies, but the scattering of blue light is why the sky appears blue. Note though that over time your vision would adjust to any ambient shading of the light though and adjust for it until it seemed normal.

The second thing to consider is the materials making up the ring and how they are arranged. If the ring is mostly iron oxide then it might be red, sulfurous compounds yellow. Ice might be white, or blue, or any other colour. But those are wide generalizations, just find out what colour the material reflects and you have it.

The final thing is the colour of the star. A red giant will naturally colour everything red, while a brighter blue star will shift things the other way.

So now combine those two effects, and you have the colour of your rings:

  • In space you will see the reflected colour of the material as modified by the light the sun is putting out.
  • From the planet additionally you will have the absorption and scattering effect of the atmosphere.

At night the rings would act a little like the moon, in that you would see the rings glowing to both the east and the west (although once in the shadow of the planet the glow would stop). During sunrise and sunset the illuminated part of the rings would be on the opposite side of the sky from the sun. Looking towards the sun it would potentially only be visible as a darker band if it moves in front of the sun.

The rings would be very useful for navigation, telling position and direction would be much simpler than on earth.

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  • $\begingroup$ I'm confused about your second to last paragraph. You said that during sunrise/sunset, the opposite side of the sky would have the illuminated rings... why? It seems to me that the rings would be illuminated on the same side as the sun, and in fact start glowing long before the sun starts coming up, as the sun's rays will strike them first. $\endgroup$ – Thomas Myron Feb 28 '18 at 16:02
  • $\begingroup$ @ThomasMyron I guess that depends on the optical properties of the ring. In general though if the ring is between you and the sun then you would expect it to be dark as you are looking at the "night" side of the ring. If you and the sun are on the same side you are looking at the "day" side. $\endgroup$ – Tim B Feb 28 '18 at 16:24

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