Does a planet's axial tilt and seasonal progression affect a planetary-ring system, as seen from the planet surface?

Question

Ok, so I have determined my world can keep it's planetary ring system. YAY! Now I just need to clarify once and for how it would look like from the planet surface. I think I have it worked out, but definitely need second and third opinions.

I curious to the impact of the planet's axial tilt and the progression of the seasons

NOTE: This is about the CHANGING 'look', based on known planetary positions with regards to the Sun throughout the year, and not about the impact on the climate (totally different question lined up for that one)!

ASSUME:

1) Single star system.

2) Earth-sized planet

3) Rings aligned with the planet's equator.

4) Similar Axial tilt to Earth.

5) You are looking at the rings from the exact same spot on your planet throughout the day, night and year (hopefully with a couple of beers in handy shady spot nearby).

6) You have enough to keep yourself occupied all year...

You can use this old, still amazing, youtube video by Roy Prol as a reference if you like.

What I would like to know is:

1) Would it appear to set and rise through the day taking into account the planet shadow on the ring surface? I am aware the rings will still shine at night due to reflections from the various light sources so I'm assuming it wouldn't disappear altogether during this 'setting' and 'rising' period. But would there be a noticeable difference in the arc brightness at any particular time? This part of my question actually seems to already be answered here! Onto the next conundrum.

2) Would you always see the same amount of ring width throughout the year or would this shift with the seasons? I'm thinking there would be something of a range between the equinoxes and solstices.

BONUS related question, would there be a corresponding effect on the width and 'intensity' of the ring shadow on the planet's surface?

3) Would the time of day you saw the rings differ with the seasons? for example, from your randomly chosen spot to sit for an entire year, would you have no visible rings during winter days but visible during winter nights; and vice versa, would they be visible during the summer days but not summer nights.

OR, Is all that I have imagined dependent on the ring system being on an ecliptic orbit? If so, great! (high five me!) Is it possible to have a stable ring system on an ecliptic orbit? (ah, man...back to the drawing board!)

Answer 1

I'm not an expert, but I did a little searching and this is how I believe that planetary rings act:

To start off, I believe that rings in general will be equatorially bound in general. Rings are formed when a moon or other small object (relative to the planet) gets orbits in too close and is utterly destroyed by the immense gravity of the planet. The plane boundary of no return for an object is based upon its composition. The denser the material (like iron) will be closer to the planet than less denser materials (water-ice). I am making a leap here in my assumption that that means that outer rings are formed from less dense materials than inner rings. As for why I believe they will be equatorially bound in general, if they weren't, we would see planets with disorganized clouds of dust otherwise or disordered rings that orbit in all different paths. In our solar system, our moon is somewhat equatorially bound as are the rings of Saturn and Uranus (my biggest piece of evidence since it is tipped at around 90%). I assume that in the formation of rings that a dust cloud of sorts develops first and that it eventually coleuses into a ring formation around the equator. Planets are slightly wider at their equator's due to the spin (like when a pizza chef spins the dough to flatten it out) which means that gravity is slightly stronger there (this extra gravity is what determines where the rings sit).

Now moving on to your actual questions...

Rings will always appear in the same location within the sky: day or night, winter or summer (relative to your location). For example, with the rings equatorially bound as I inferred above and you stated (this is why I went through all of that) the rings would move with the tilt of the axis so as to follow the pull of gravity and as such, everything would move as a single unit and would, relatively speaking, nothing would move with seasonal or day/night changes. If you were standing on the equator looking up, you would have a poor view. All you would see is a line stretching from east to west (or west to east if your planet spun that way - but most planets will spin along with the general spin of their host system's orbits unless acted upon by some outside force - Uranus). If you were in the Northern Hemisphere, you would have a view of the rings in the southern sky and the further you got north, the more spectacular the view. The reverse would be in effect in the Southern Hemisphere. As for the poles (north and south), one should be able to see the entire ring system as an extension of the horizon in all directions.

Don't misunderstand me, seasons do have a major impact on the view of the rings (SHADOWS!!!).

During an equinox, approximately a third of the ring system will be in the shadow on the dark side of the planet. When looking up into the sky, the shadowed ring segments will appear black as they would block out the stars too which could also be an interesting feature to the sky. Keep in mind that the reverse is happening too during an equinox as well: the ring segments on the far side of the planet are carving a shadow that falls along the equator. From the Equinox to the Northern Hemisphere's Winter Solstice, the shadow that falls on the equator will grow larger every day and farther north every day. The full extent of the shadow on the solstice will depend on the degree of tilt and the shear size of the rings. Keep in mind that if your tilt goes too high (like 45% I think which would be completely outrageous), the shadow will have reached the north pole and start being cast into the void of space above the pole (so the amount of the planet under the shadow will be reduced). As this is happening on the "day" side of the planet, the "night" side of the planet will see the shadowed segment grow smaller every night which would make for a better view on the Solstice at night. (the reverse of all of this is true as well)

I hope that this answers your questions. Looking at some pictures of Saturn might help you to visualize if you read along. Better yet might be to make a model of Saturn and go into a dark room with a flashlight on a table. With that setup, you could manipulate the model and see how the shadows react.

As a side note, also look up some pictures of rings that have had objects fly through them or the gravity of a moon disturbs them. I guess adding a moon might make it more complex (but Saturn has tons of them so idk on that). I saw some recent ones that show the effects and it appears that the rings have been smudged. According to the article I read, the ring repaired itself within 2 months. Here is a link:

http://www.businessinsider.com/a-mysterious-object-caused-a-disruption-in-one-of-saturns-rings-2016-6

Hope I wasn't too wordy and that this helps!!!

Answer 2

I had one major addition, related to seasons and tilt, that seems to have been (partially) overlooked, or at least not directly described. The rings can shadow themselves. They have a 'top' and 'bottom' (or north and south if that makes more sense to you), and the star will only shine directly on one side at a time, depending on the season. So an observer in the northern hemisphere, during a summer day, would see the complete ring, at its most reflective (but due to daylight washing it out, it would not seem to be the "brightest"), that same observer, late that night, would see the (apparent) brightest rings of the year, but with the shadow of the planet falling on them, so they would not appear 'complete' but would have the dark gap mentioned by the answer selected by the OP.

BUT

The same observer, in the same location, on a winter day, would not see the rings themselves, directly, but might see only their silhouette (like a ring eclipse), or possibly a strip of sky darker than the rest, depending on if they were directly in the shadow that the ring, or on the edge of the shadow, or not near the shadow. And at night in winter, they would see nothing of the ring at all, other than the black strip of missing stars.

From the spring equinox, the rings would slowly brighten until the summer solstice, and then start to fade again until the autumn equinox when their brightness is reduced to its lowest point, where it will remain until spring.