[SPACE 4e] System Design help? (star systems that is...)

[Jon F. Zeigler]

I'd go with a wide binary star system, in which both stars are about the same mass and age, and are reasonably Sol-like. It's unlikely but feasible to get two worlds in the habitable zone of a single star. Three is really stretching it, but the third one can orbit the companion star.

This is, oddly enough, exactly the arrangement of the Manticore system from David Weber's "Honor Harrington" novels. If I remember correctly, Manticore (the planet) and Sphinx orbit the star Manticore-A, while Gryphon orbits Manticore-B. Manticore is pleasantly Earthlike, Sphinx is further out and has very severe winters, and Gryphon has high axial tilt yielding very strong seasonal variations. Weber may have borrowed a little too enthusiastically from Napoleonic history, but his worldbuilding is fairly plausible.

[Ze'Manel Cunha]

Originally Posted by copeab

I'd go for three very large moons around a very large gas giant that's in the habitable zone.

I've used that model, it's a valid idea, and its unlikeliness can be waved off with enough possibilities.


The other model I've used, though possibly even less likely, is a double planet* along with a third planet within the habitable zone.



*The double planet setup simply requires the equivalent of an Earth-Moon system on a greater scale, the planets would be further apart, but the tides would still be greater than ours.

[Qoltar]

Holy *BLEEP*!,
The Author of the book himself replied. Wow!! Well, I will have to give your advice and suggestion a little more weight.

Looks like time to get out out the notepaper pad, a few pens and work all this out. I'm meeting with the player in question this Saturday afternoon.
If anyone has any more suggestions - I will look forward to reading them.

- Edmund W. Charlton

[Captain-Captain]

Originally Posted by abatishko

Unfortunately, that's not what causes summers to be warmer than winters. Witness the fact that our world has summers at opposite times of the year depending on whether you are in the northern or southern hemisphere. This would be impossible if it was caused by proximity to the sun, because you can be closest to the sun at two times during the year no matter what your orbit looks like.

However... he's got the right concept. Give your innermost planet an axial tilt of 0. Then you won't have any seasonal effects. Technically this only shifts the problem from a seasonal one to a latitude one. The equator would be too hot. But, the temperate and polar zones might just be ok.

And conveniently you could have the two poles being near centers to two supercontinents so most of the living space on the planet is away from the equator.

[Qoltar]

Had lunch with the player in question. She gave me more parameters - but does not actually care how "perfect" the Astrophysics winds up being.

So I can fudge it if I have to .

As she described it to me ...none of the three are "HellHoles" or variations of "Hell-like".

There are 3 planets in this system. We'll refer to them by number(letter) combinations - okay?

1(Bt)
The closest in to the system's star is 1(B) That planet is the "capital" in this system. It has quite a bit of trade, High-tech, ARTS & Literature, Museums, parklands and such. The Weather there is closest to that of Central Italy - Mild winters and such. There IS a little bit of Ice and Snow at the poles.

2(Gl)
The "middle" planet for placement purposes is 2(G) . This planet's climate and weather is mostly like that of the Mediterranean in the Northern part of the world...but more Desert-like in the southern plart of the planet . (Think of an Israel-like "Desert")

3(Sh)
Third planet out from the Main Star that is habitable we'll refer to as 3(Sh) That one is the "home planet" of the player's character. Its terrain is dominated by a Red Desert, stony - some sandy areas...evidence of volcanic activity in the past (i.e. colored sand; multi-color rocks) The culture there is mostly Fighters, Shepherds; agriculture. Only recently have they started to go "high-Tech" (within the past 60 years before the game starts. )
This planet's Poles only get as cold as the Mediterranean at its coldest.

So with all that in mind - what orbits, and other things could or would accomodate the above?

- E.W. Charlton

[balzacq]

Originally Posted by Jon F. Zeigler

I'd go with a wide binary star system, in which both stars are about the same mass and age,

Does this mean that the several stars of a multiple star system can have different ages, notwithstanding the rules stating that age is determined per system? Or should there be one age for the system but possibly a different age for Distant companions (drawing from the Proxima Centauri example)?

While we're at it, in a system with the Eccentric Gas Giant arrangement, should there be a roll for the eccentricity, and would it sweep out a forbidden zone much like a companion star (but smaller, presumably)? Or instead would the next orbit in/next orbit out be determined from the initial gas giant's periastron/apastron instead of its mean orbital radius?

For that matter, should there be a roll on the Eccentricity table for regular planets, and what would be the mod?

[Side idea: What would you think of a generation system whereby the planets were generated as for a Main Sequence star of the star's original mass, and then evolved (read: mostly destroyed) if the star were old enough to be a subgiant, giant, or white dwarf? I'm aware that most inner planets would be swallowed and destroyed in a star's giant phase, but would gas giants have their atmospheres reduced (blown away) and ice planets melted either in the giant phase or in the stellar shell ejection?]

(I'm writing a php script and eventually an Astrosynthesis plugin to generate systems, so saying "pick it yourself to taste" won't actually be helpful. :-)

Thanks,

[Pomphis]

Originally Posted by balzacq

[Side idea: What would you think of a generation system whereby the planets were generated as for a Main Sequence star of the star's original mass, and then evolved (read: mostly destroyed) if the star were old enough to be a subgiant, giant, or white dwarf? I'm aware that most inner planets would be swallowed and destroyed in a star's giant phase, but would gas giants have their atmospheres reduced (blown away) and ice planets melted either in the giant phase or in the stellar shell ejection?]

I would love to see that. I just started to do it for a subgiant system. I first rolled up the original system, and then I redid all planetary classifications based on the new blackbody temperature.
In my case, the GGs kept their atmospheres (but look probably a lot larger), but some terrestrials were changed a lot.

Another thing I would be interested in is temperature variations for eccentrity.
I believe that planets warm and cool quite slowly, so even noticable eccentrity wouldn´t necessarily create seasons of its own. But I have no idea
how much eccentrity I can safely ignore, and where it might become an issue.
And also no idea how important atmospheres or oceans are for this.

[Jon F. Zeigler]

Originally Posted by balzacq

Does this mean that the several stars of a multiple star system can have different ages, notwithstanding the rules stating that age is determined per system? Or should there be one age for the system but possibly a different age for Distant companions (drawing from the Proxima Centauri example)?

Don't read too much into my slip of the tongue :-). Yes, in general, you can assume that all of the components of a multiple star system formed at the same time and are the same age, hence the rule as written. I could see a Distant companion being of a different age, as you suggest, if it were formed at a different time but was eventually captured into the system (or if it just happens to be wandering by).

While we're at it, in a system with the Eccentric Gas Giant arrangement, should there be a roll for the eccentricity, and would it sweep out a forbidden zone much like a companion star (but smaller, presumably)? Or instead would the next orbit in/next orbit out be determined from the initial gas giant's periastron/apastron instead of its mean orbital radius?

Both of those would be reasonable extensions - I considered adding them to the original rules set, but eventually decided they would add too much complication for a special case. One could also make the case that an epistellar gas giant would prevent the formation of planets anywhere between its final position and the snow line . . . eating the protoplanets for breakfast as it spiraled inward to its final position.

For that matter, should there be a roll on the Eccentricity table for regular planets, and what would be the mod?

Hmmm? Not quite understanding your question here.

[Side idea: What would you think of a generation system whereby the planets were generated as for a Main Sequence star of the star's original mass, and then evolved (read: mostly destroyed) if the star were old enough to be a subgiant, giant, or white dwarf? I'm aware that most inner planets would be swallowed and destroyed in a star's giant phase, but would gas giants have their atmospheres reduced (blown away) and ice planets melted either in the giant phase or in the stellar shell ejection?]

Again, that's a reasonable extension to the system.

[balzacq]

Originally Posted by Jon F. Zeigler

One could also make the case that an epistellar gas giant would prevent the formation of planets anywhere between its final position and the snow line . . . eating the protoplanets for breakfast as it spiraled inward to its final position.

Makes sense. Would an eccentric GG do the same?

Originally Posted by Jon F. Zeigler

Hmmm? Not quite understanding your question here.

Well, planetary orbits in the Sol system arent' circular -- I was wondering if you'd contemplated generating this on the Eccentricity table. No worries -- I'll just make something up.

Originally Posted by Jon F. Zeigler

Again, that's a reasonable extension to the system.

Cool. I'll give it a shot, once I do a little more research.

Thanks!

[Jon F. Zeigler]

Originally Posted by balzacq

Makes sense. Would an eccentric GG do the same?

Probably. The model seems to be the same for both, except that the physical processes that cause the epistellar gas giant to spiral all the way inward don't work as effectively (or as completely) for the eccentric gas giant.

Well, planetary orbits in the Sol system aren't circular -- I was wondering if you'd contemplated generating this on the Eccentricity table.

Hmmm. I don't have my author's copy in front of me, but I could have sworn I had some provision for the eccentricity of planetary orbits in there. Let me get back to you after I've had a chance to review the text.