Causing periodic storm events on a fictional planet

[Luno845]

Hi, I’m looking for ideas and guidance (maybe even formulas?) on making an on-planet situation match a hypothetical solar system. It’s for a fantasy role-playing, but the sentient species must necessarily care (and believably calculate) aspects about their solar system. (However, because it’s fantasy instead of science-fiction it doesn’t have to be ‘perfect’, but it would make the world more believable and, at least based on my limited astronomy knowledge (very limited!), I think it’s possible to achieve what I want with all the variables available for manipulation).

The set-up:

-earth-like planet (E) with a Moon-like moon (M)

-roughly every 24 years (give or take, depending on how the calculations work out) another planet (AP) nears enough to cause a period of intense (but not planetary extinction event level) storms (changing gravity force on tides, tsunamis, etc.) on E. (The storms last anywhere from a few weeks to a couple months, based on how long AP remains near… or after-effects from AP coming near)

-roughly every 1000 years, these storms are markedly more intense, as AP lines up with E and the system’s sun (but storm intensity is also periodic throughout month because of M’s Moon-like orbit); and partial eclipses affect surface light on E, temp, etc.

(I initially thought AP could be a second moon, but based on the once per 24 yrs and the once per 1000, I feel like that wouldn’t work now. Correct me if I’m wrong!)
First, is this possible? The planet ‘HR 5183 b’ makes me think the fictional AP could work, with its highly eccentric orbit, and that AP’s orbital path could cut inside that of E’s to allow for periodic solar eclipses (1 per 1000 yrs?) on E.

Then, these questions:

-What orbit angle to E’s ecliptic must / can AP have? (so sentients on E know where to look in sky for AP / to allow for once per 1000 yrs solar eclipse).

-what orbit period must / can AP have? (and I suppose the nearer to sun (nearer to E, looking at something like HR 5183 b) the faster it’d travel through E’s sky)

-Exactly how long would AP remain near E? (how long would storms last?)

-How big / near would AP be to be able to have storm-causing effects on E (without ripping surface completely apart)? From this, would E experience 1) full eclipse for multiple days vs 2) periods of eclipse each day (sun arc going through AP position); (also, I understand the eclipse part may not matter as much if everything on E is covered in storm clouds)

Am I asking all the questions I need to be? Am I way off on the possibility of this system? Is this way too complex (or simple)? I’d love any inputs! Eventually I hope to have some sort of excel formula to punch in numbers, like E orbital period = x, E ecliptic angle = 0 deg; Moon orbital period = x, … and how the AP variables would change, etc. But any suggestions are greatly appreciated! Thanks!

 

[anorlunda]

It reminds me of Isaac Asimov's Nightfall, a very famous SF story. He based the physics on a multi-star system. Whatever you choose, keep it simple with only one effect or a few, but not many.

In 1968, the Science Fiction Writers of America voted "Nightfall" the best science fiction short story written prior to the 1965 establishment of the Nebula Awards, and included it in The Science Fiction Hall of Fame Volume One, 1929-1964.

 

[BrassOctopus]

Do you really need that much detail in your RPG? I think your description is perfectly sufficient (and exciting, really), and in fact by leaving the precise rules in vague territory, can give you wiggle room when the various denizens offer up their own explanations and accounts, which probably should have mistakes (especially since there's a millennium event). You'll also have that much more to throw at the players at a moment's notice.

 

[member 656954]

My goto app for orbital mechanics questions like this is AstroGrav,@Luno845, you can create the solar system you're imagining and see how it works, including running an orrery simulation forward and backward in time, so your 1,000 year event can be visualized. By editing attributes of a planet you can see how stable an arrangement like yours would be.

Russell from AstroGrav is really helpful if you need advice or assistance. There are also a number of predefined exoplanetary systems you can download, such as Gliese 876, Kepler 9, and Tau Ceti which help visualize simpler configurations than our solar system.

 

[DrStupid]

-roughly every 24 years (give or take, depending on how the calculations work out) another planet (AP) nears enough to cause a period of intense (but not planetary extinction event level) storms (changing gravity force on tides, tsunamis, etc.) on E. (The storms last anywhere from a few weeks to a couple months, based on how long AP remains near… or after-effects from AP coming near)

My best idea would be a horseshoe orbit with a heavy planet AP (maybe even a gas giant) and a small planet E almost in the same orbit. Everytime E approaches AP it will be pushed from a lower into a higher orbit or vice versa. During the encounter E would be affected by AP's tidal forces. As the change of the orbit will most likely result in a corresponding climate change, this could also explain the storms. But it would imply that the climate oscillates between hot and cold periods of around 24 years each.

An alternative explanation would be very different orbits of E and AP. But the close encounter of both planets would change their orbits. In order to get long-term stability the planets must be in an orbital resonance where this effect cancels out over time. I don't know if such a system is possible and if yes how to design it.

I have no idea for the 1000 year period. Maybe it is best to leave the reason unknown or just include some vague speculations. In a fantasy world I expect knowledge about the objects in the sky as seen from the ground but not about orbital mechanics. I would leave it at that. Associate the unusual tides and climate effects with visible astronomical features without too many details and mix it with the inevitable esoteric interpretations that are typical for ancient cultures.

 

[Luno845]

My best idea would be a horseshoe orbit with a heavy planet AP (maybe even a gas giant) and a small planet E almost in the same orbit. Everytime E approaches AP it will be pushed from a lower into a higher orbit or vice versa. During the encounter E would be affected by AP's tidal forces. As the change of the orbit will most likely result in a corresponding climate change, this could also explain the storms. But it would imply that the climate oscillates between hot and cold periods of around 24 years each.

An alternative explanation would be very different orbits of E and AP. But the close encounter of both planets would change their orbits. In order to get long-term stability the planets must be in an orbital resonance where this effect cancels out over time. I don't know if such a system is possible and if yes how to design it.

I have no idea for the 1000 year period. Maybe it is best to leave the reason unknown or just include some vague speculations. In a fantasy world I expect knowledge about the objects in the sky as seen from the ground but not about orbital mechanics. I would leave it at that. Associate the unusual tides and climate effects with visible astronomical features without too many details and mix it with the inevitable etoteric interpretations that are typical for ancient cultures.

thanks so much for the ideas!

 

[Luno845]

Do you really need that much detail in your RPG? I think your description is perfectly sufficient (and exciting, really), and in fact by leaving the precise rules in vague territory, can give you wiggle room when the various denizens offer up their own explanations and accounts, which probably should have mistakes (especially since there's a millennium event). You'll also have that much more to throw at the players at a moment's notice.

There will definitely be a range of understanding across different civilizations, based on which was toppled by the previous millennium event, which protected astronomical knowledge, etc. I wanted to explore more 'exact' numbers though because I'm really loving the world as I develop it and am wondering about writing some stories within it. Thanks for the thoughts!

 

[Luno845]

It reminds me of Isaac Asimov's Nightfall, a very famous SF story. He based the physics on a multi-star system. Whatever you choose, keep it simple with only one effect or a few, but not many.

thanks for the story suggestion! I found it in my library collection and hopefully will be able to check it out soon.

 

[Luno845]

My goto app for orbital mechanics questions like this is AstroGrav,@Luno845, you can create the solar system you're imagining and see how it works, including running an orrery simulation forward and backward in time, so your 1,000 year event can be visualized. By editing attributes of a planet you can see how stable an arrangement like yours would be.

Russell from AstroGrav is really helpful if you need advice or assistance. There are also a number of predefined exoplanetary systems you can download, such as Gliese 876, Kepler 9, and Tau Ceti which help visualize simpler configurations than our solar system.

Thanks for the link! I'm definitely down the rabbit hole now.

 

[DrStupid]

This is an example for a horseshoe orbit of a Jupiter-like planet AP and an Earth-like planet E with a Moon-like moon M at a distance of 1 AU from a Sun-like star S with around 24 years between each encounter:

https://tinyurl.com/y6j967xy