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Since we just had an eclipse, I began to think: what would it look like if a planet had rings and two moons?

Now, there are two solar eclipses going on at the same time! What would the sky look like?

I saw in another question that the rings give off their own shadow as well, but regardless of that the question remains:

What would the sky look like if the planet had rings and was experiencing a double eclipse? It is experiencing two partial solar eclipses.

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  • $\begingroup$ When you say double eclipse, do you mean that the two moons are both partially blocking the sun at the same time (they appear very close in the sky)? $\endgroup$ – Monica Cellio Aug 24 '17 at 0:21
  • $\begingroup$ You are lacking a companion star... $\endgroup$ – user6760 Aug 24 '17 at 1:06
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The rings, in a stable system, will be on the same plane where the eclipsing moon is orbiting, so at least part of the rings will be in the shadow cone.

If eclipse is not projected in the above plane (i.e.: sun is not exactly on that plane, also), shadow cone will leave the rings and won't cut the whole rings but only make a dent in them, if the moon is farther then remotest ring effect may be null ("dent" may terminate before beginning of rings).

In any case you would see, more or less, what you see from Earth.

If the moon is really big (like ours or more) and the eclipse is total you could see the rings even by day, in spite of the refraction from the atmosphere.

You could be able to see a dent in the ring, but that would be doubly difficult because the gap would be exactly where the sun should be, so any glare and/or refraction will cover it making it impossible to discriminate.

The effect would be evident if observed from space, possibly from a point relatively far from orbital plane.

It is unclear to me what you mean, exactly, by "double eclipse", so I cannot answer that.

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    $\begingroup$ I think the rings HAVE to be in the shadow cone. For a stable system, the moon will orbit within the ring plane. The shadow line will lie on the intersection of the planets orbital plane with the ring plane. Minor variations and wobbles may throw the shadow high or low, but afaics the rings are very likely to be shadowed. Having the rings not shadowed is the special case, and I'm not sure it is valid in a stable, long-lasting system. $\endgroup$ – Innovine Aug 24 '17 at 11:29
  • $\begingroup$ @Innovine: you are right. I'll upgrade answer accordingly. $\endgroup$ – ZioByte Aug 24 '17 at 11:37
  • $\begingroup$ @Secespitus: are you mother tongue english? Your edits do not seem right to me, but I might be very wrong. Care to explain? Tkx! $\endgroup$ – ZioByte Aug 24 '17 at 13:05
  • $\begingroup$ @ZioByte I am not a native speaker, but my english is quite good. Interestingly you are the first person on this site to think that my edit was not good. At least you are the first one to ping me because of this. And I have edited 757 posts on this site that were not deleted. Thanks for mentioning if something doesn't feel right! You can always roll back an edit if you feel someone edited too much. $\endgroup$ – Secespitus Aug 24 '17 at 13:16
  • $\begingroup$ But in your case I think I am right: you are missing quite some articles. When referring to things you need an article. For example "the moon" as it is not our Earth related Moon, but a generic moon. Or "The rings" because you are referring to the rings mentioned in the question. Of course I might be wrong, too. $\endgroup$ – Secespitus Aug 24 '17 at 13:17
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There are many other factors determining how it looks which you haven't mentioned. The time of day, the axial tilt of the planet, the observers location, etc. Note that the moons will be orbiting within the ring plane, and so the shadow of the moon must lie along the intersection of the ring plane and the planets orbital plane.

In general, I think the most spectacular view would be that for an eclipse crossing the equator and directly overhead. In this case, the rings would appear to come out on opposite sides of the sun/moon, directly overhead, and those parts of the rings will be illuminated. The amount of bounced light and indirect illumination is debatable, as is indirect bounced light from the other moon, but it might be possible that the sky darkens as much as in our eclipses, with the rings being like a glowing thread stretching down to opposite sides of the horizon. It's also possible that the outer rings would be illuminated, but obscured by the dark inner rings, so that the entire ring structure would be invisible.

A little further away, to the north or south, the face of the rings would start to become visible. The sun will be illuminating the rings edge-on, and so indirect illumination on the ground should be minimal. This means the sky wouldn't be fully dark, but pretty dark, and the rings wouldn't be all that visible, but if they were, the shadow across the rings from the moon would make the rings look like they had a gap in them, to observers outside the eclipse zone. The observers in the eclipse zone probably are too edge-on to the rings to see much.

For eclipses occurring not on the equator, for an observer not on the ring plane, and assuming the planet has an axial tilt (seasons) then the eclipse could look like ours, but with the addition of rings, a bit like a thin or dim rainbow, with the outer ring illuminated on the sun side, and the inner rings mostly unlit.

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