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[Scoops Novel]

I am using this (http://www.orbitsimulator.com/gravity/articles/what.html god damn it how do i hyperlink i mean really) to simulate this lot of planetary bodies gravity and orbits. https://docs.google.com/document/d/1GVPb4gSUxZjHakDfzdwqEtGHFnoMH7uINYaK4H5KLA4/edit?pli=1. I'm running a Warhammer 40k game, so any eccentricities are to be expected, but nevertheless if i can manage it I'd like to have a cool spinning framework to go with the artwork for my group (as well as helping said artwork). It might give me ideas for the campaign, and will certainly piloting more interesting.

The main problem i have is both determining what all the ambiguous statements actually translate to in figures, and hopefully making their description (Ice world, Burning world, Hot world) believable, though i have options there of course. I'm looking for what can be considered a "large" rocky planet, the expected range of a Goldilocks zone for a class f star (or whatever is applicable to a white star that's going strong), and whether the listed orbit ranges are entirely unrealistic, and if they could be realistic how so. Basically everything to do with this The vague statements are as such, in a condensed version:

A bright white, Vigorous star

Inner Cauldron (inner orbit)

Large, arid "Normal"- roughly earth-standard gravity- Burning Inhospitable planet, with a Lesser Moon

Primary Biosphere (Goldilocks zone)

Small and Dense High Gravity Hot planet

Outer Reaches (outer orbit)

Gas Giant (Gas Dwarf), weak gravity for a Gas Giant

Large and Dense High Gravity Inhospitable Ice planet, orbited by a Large Moon with "Normal" gravity which is also a Cold World, and a Lesser moon

Vast High Gravity Inhospitable Ice planet, orbited by a Large Asteroid and a Lesser Moon


That's the system. Here are the relevant rulebooks descriptions for the mentioned sizes, which I'm sure they won't mind you having.

Small and Dense: The shrunken silhouette of this Planet belies the strength of its gravity well and the richness of
its crust.

Large: Worlds of this size can range across a vast spectrum of possible types.

Large and Dense: Though impressive in volume, the mass of this world is, in fact, compressed significantly.

Vast: Huge and voluminous, worlds of this type strain the upper edges of the possible size for a single world.

Gas Dwarf: Although much smaller than the typical world of this sort, a Gas Dwarf is still considerably more massive than
most rocky Planets.

I appreciate any and all advice and will try and answer query's. Then it's just the course charting .

[Il Palazzo]

Your request is a bit vague. Can you specify what is it that you need, exactly? Possible ranges of masses? Some orbital parametres(which?)?

[Scoops Novel]

Yes, that exactly. I'm looking for what can be considered a "large" rocky planet, the expected range of a Goldilocks zone for a class f star (or whatever is applicable to a white star that's going strong), and whether the listed orbit ranges are entirely unrealistic, and if they could be realistic how so. Basically everything to do with this. Editing into OP.

[Orb]

http://astro.unl.edu/naap/habitablezones/animations/stellarHabitableZone.html

This should probably be useful. Just find out the mass of a class f star, plug it in, and there you go.

For your "life" planet, it'd be more realistic for it to have a thicker atmosphere. The higher gravity would capture more gasses. It'd also need a thick atmosphere to protect the biosphere from the strong radiation being emitted from the star.

Also, we tend to think in earth units when describing planets. A hot planet is hotter than earth, a cold planet is colder than earth. Planets have thick atmospheres if they're thicker than ours, and the opposite is also true. Get the picture? So for a planet to be "large", make it bigger than the earth. Also note that if your large arid planet is close to the star, it'd likely have its atmosphere stripped off (see mercury). While you can have some leeway, you'd want to probably have it closer to the goldilocks zone rather than the star itself.

Disclaimer: I'm just an astronomy enthusiast. What I'm saying isn't expert advice. 

Edit: Didnt' see the ice planet and other things. One thing to note, having a large rocky planet forming past a gas giant is rare (or impossible). Gas giants form because when a star forms it "Blasts" all the gasses into deep space, while the solids travel out much more slowly. Rocky planets form close, and gas giants form out in deep space. After gas giants we get tiny rocky planets, because there's just not enough "stuff" to hold gasses to a body.

I would suggest having the ice worlds be large moons of the gas giant (since gas giants tend to just kidnap large rocky objects floating around in the solar system) or put the planets between your habitable planet and the gas giant. Of another note is the atmosphere. Once a planet gets cold enough gasses start to turn to liquids and then solids. If you want to really be realistic, make the atmospheric composition something with a low boiling point.

[ndkid]

There are a number of different games out there that have stellar generation as part of what they do. Various versions of Traveller, for example. One that I know I came across recently that might have enough for your needs and was available online was a portion of Battletech's Interstellar Operations sourcebook, which has been in development hell for years.

http://bg.battletech.com/?p=4445
I'd definitely recommend looking at the forums noted in there as well, since the discussion forum had a lot of stuff about making the RAW more realistic, and I don't know if those were edited back in or not.

[Il Palazzo]

Another habitable zone calculator:
http://depts.washington.edu/naivpl/sites/default/files/HZ_Calc.html
Includes nice informative pictures, although it's not as interactive as Orb's.
The inner limit is for minimal greenhouse effect, the outer conversely. This means that you wouldn't have an ice planet at the outer limit.
The calculations used do not factor cloud cover effects, which act to stabilise the temperature, so you may actually make the planets a bit closer than the inner limit.
Everything else should be self-explanatory, but by all means let us know if something's unclear.
The accompanying paper:
http://arxiv.org/abs/1301.6674
A good read, if you like the guts of science. If nothing else, read the conclusions and graphs.

Rocky planets are considered to have up to 10 Earth masses. The transition to a gaseous planet is not a sharp one, but 10 E_m is a good rule of thumb to go by.
Remember that volume is proportional to the third power of the radius, so 10 E_m corresponds to barely above 2 Earth radii, assuming constant density.
As for the density itself, there appears to be a relationship with radius, where smaller planets are generally more dense.
This article http://arxiv.org/pdf/1307.1649v1.pdf (it's not a very good one, but it's the only one I've found on short notice) analyses this kind of relationships. Fig.4 graphs radius-density.

A bright white, Vigorous star

Class FV, ~7500K surface temperature. Say, 4 times as luminous as the Sun.
You could use an AV star, as they are much more white and hot, but the calculator might be off for values above F class stars. Also, A stars die fast, meaning no native life forms.

Inner Cauldron (inner orbit)
Primary Biosphere (Goldilocks zone)
Outer Reaches (outer orbit)

The calc will give you ~1.5-3 AU as the habitability zone. Place the planets accordingly.

Large, arid "Normal"- roughly earth-standard gravity- Burning Inhospitable planet, with a Lesser Moon
Small and Dense High Gravity Hot planet

Use the simple relationship between size, gravity and density: g~ρ*R
so half the radius means half the gravity, unless it's twice the density(use Earth as the baseline). Watch out with the densities, so that you don't set them too high. A small, mostly nickel-iron planet seems perfectly feasible, but a huge globe of palladium or gold - much less so.

Gas Giant (Gas Dwarf), weak gravity for a Gas Giant

Make it somewhere between 5 and 10 Earth radii, as these planets appear to have low densities(the second paper, fig.4).
For comparison, Uranus is 4 E_radii, Saturn is 10. Again, keep in mind the relationship above.

Large and Dense High Gravity Inhospitable Ice planet, orbited by a Large Moon with "Normal" gravity which is also a Cold World, and a Lesser moon
Vast High Gravity Inhospitable Ice planet, orbited by a Large Asteroid and a Lesser Moon

Place these farther than the habitable zone, or at the outer edge of it, as without greenhouse effects they would become ice worlds there too.
As mentioned by Orb, outer edges of a stellar systems are thought to breed larger(so, gaseous) planets. Don't place them too far. Some outward migration can be plausible, but don't go overboard.


This topic is an active field of research, so you can both expect older references to be out of date, and a bit of leeway as to what is actually possible.

[Scoops Novel]

Thanks for the help. I'm basing my figures on what you've said so far, the required ones being Mass, Size, Diameter, Eccentricity, Inclination, Longitude of the ascending node, Argument of Perifocus, and Mean anomaly. If anyone wants a look the tutorial with attached screenshots is here, though it doesn't explain the concepts. http://orbitsimulator.com/gravity/tutorials/tutorials.html#mnueditobject.

I'm curious as to the age of Class F stars, bearing in mind that this one is supposed to be going strong. It should give me a better idea of the habitable zone alongside possible other factors. Additionally, you've likely noted the moons and lesser moons prevalent on a couple of planets, as well as a large asteroid at that. I have little to no idea what constitutes a reasonably sized or "lesser" moon, and the starting conditions that would draw them to the planet, which I'd likely need if i wished to determine their orbit.

If anyone has a easier to use gravity simulator which still allows for some manipulation I'd very much appreciate a link.

[Delta Foxtrot]

I am using this (http://www.orbitsimulator.com/gravity/articles/what.html god damn it how do i hyperlink i mean really)

Behold:

Code: [Select]

[url=http://www.orbitsimulator.com/gravity/articles/what.html]OrbitSim[/url]OrbitSim

[Scoops Novel]

I am using this (http://www.orbitsimulator.com/gravity/articles/what.html god damn it how do i hyperlink i mean really)

Behold:

Code: [Select]

[url=http://www.orbitsimulator.com/gravity/articles/what.html]OrbitSim[/url]OrbitSim

It's- wonderful.

[Il Palazzo]

Thanks for the help. I'm basing my figures on what you've said so far, the required ones being Mass, Size, Diameter, Eccentricity, Inclination, Longitude of the ascending node, Argument of Perifocus, and Mean anomaly.

You should be able to set the masses and sizes(planetary radii, I presume?), as well as diametres(or rather, semimajor axes) based on the earlier posts. Eccentricity should be lower the closer to the star a planet is, as tidal forces tend to circularise the orbit, unless it's in some sort of orbital resonance(as is the case with Mercury). If I were you, I'd simply make all the orbits within 10% of being circular, with random spread of eccentricities, tending to lower near the star.
Inclinations need to follow similar rules, unless it's a captured rogue planet(unlikely, at best). Keep them within a few percent of being coplanar and you're set.

As for the remaining orbital parametres, what do you need these for? For a project like this, there's little physics to justify the preference of some particular value over the other. They can be treated as fully random values(within the ranges specified, so 0-360 deg.).

I'm curious as to the age of Class F stars, bearing in mind that this one is supposed to be going strong. It should give me a better idea of the habitable zone alongside possible other factors.

Use Orb's calculator, and set the mass to 1.5. This roughly corresponds to a hot F star. The predicted lifetime on the main sequence is in the viciniy of 2.5 billion years. Note the difference in luminosity by the later stages of its life.

Additionally, you've likely noted the moons and lesser moons prevalent on a couple of planets, as well as a large asteroid at that. I have little to no idea what constitutes a reasonably sized or "lesser" moon, and the starting conditions that would draw them to the planet, which I'd likely need if i wished to determine their orbit.

Let the Solar System inform you as to the sizes. Large moon can be the size of Ganymede(or, conceivably, even Earth), small ones can be anything you want, but remember that it has to be over 1000km in diametre(iirc) to be spherical.
If you want to be anal about moon placement, read the wikipedia articles on Roche Limit and Hill Sphere. The first is the minimum orbit a body can have before the central body's tidal forces tear it apart(roughly 200'000 km for a Saturn-sized central body). The Hill Sphere is the volume around a body dominated by its gravity, so you ought not have moons beyond it.
The calculations for both are pretty straightforward, depending only on the masses and semimajor axis of the orbit.

If anyone has a easier to use gravity simulator which still allows for some manipulation I'd very much appreciate a link.

Finally, I need to ask you what is your goal here? Gravity Simulator is a numerical integration tool, which means that you plug in some parametres and it'll show you how the system evolves over time, so you can experiment with the parametres to find a stable system. For example, it'll solve the Hill Sphere problem by itself - if you set the satellite's orbit too high, it'll float away from the parent planet. What I'm saying, it's great for analysing various configurations, but as a pure visualisation tool it's a bit of an overkill.

If all you need is to visualise the system, without much care for accurate gravitational interactions, I'd recommend using Celestia(http://www.shatters.net/celestia/), and mod in your own system with the parametres that you want.
The modding guide is here:
http://www.lns.cornell.edu/~seb/celestia/addon-intro.html
and the easiest way to go about it is to copy the solar system and alter what you need.

[Scoops Novel]

Thank you! This is the fruit's of my efforts so far:

Spoiler (click to show/hide)

However, the orbit of this model is not stable (on a 1000 year scale), and I'd appreciate being told how wrong that looks. I'm going the anal route of simulation because I'm hoping that i can set up some inconvenient (and easily displayed) piloting hijinks (as well as for the astronomy knowledge lols). If anyone want's figures I'll give them, and I'm afraid i hadn't taken your eccentricity advice when i took that.

[Il Palazzo]

It's difficult to see what's wrong just by looking at the picture. Show us a screenshot of the orbital parametres, or better yet, upload the GSim stellar sytem file, and we'll see what's wrong.

[Scoops Novel]

Oh good. I thought you might be averse to viruses and otherwise downloads, for whichever foolish reasons.

Link to save

[Il Palazzo]

Give us a day or two to play with it.

[Scoops Novel]

Thank you very much all. I look forward to what you come up with, and in the meantime I'll scheme on piloting challenges.