Errata for Core Rulebook

[zanwot]

Solar Systems for Dummies.

some quick details:
* The possible atmospheres are a function of size or more precisely planetary mass (the smaller planets do not have enough gravitationnal attraction to keep the mollecules of the atmo, small planets can only have atmos of heavy stuff such as methane, no hydrogen atmo for them), temperature (high temperature can do more or less the same effect as reducing the planetary gravity on the atmo), and maybe more or less evironmental influences (a moon could loose it's atmo because of tidal effects, another popular idea, though I am uncertain, is that if too close to sun the solar wind can blow atmo away).
* There cannot be in theory too many (3 or more) large objects of similar mass (3 similar stars, 3 large gas giants) as these cause chaotic orbits.

 

[lastbesthope]

* There cannot be in theory too many (3 or more) large objects of similar mass (3 similar stars, 3 large gas giants) as these cause chaotic orbits.

Depends on the relative placemnt and orbital path/period.

LBH

 

[klingsor]

I'm feeling quite pleased - the basic atmosphere bits I knew. The moon bit is interesting - and I suspect that a moon is very useful for allowing marine life to colonise the land more quickly than it might otherwise - that vital intertidal zone. The planetary dynamics bit is beyond me - but rather important.

 

[EDG]

Now I am curious about the real world subject, does anyone know a good book on modern - planetology? What is the topic to look for on the index card? What I really want is I suppose Solar Systems for Dummies.

Funnily enough, this is a book I want to write

 

[EDG]

* The possible atmospheres are a function of size or more precisely planetary mass (the smaller planets do not have enough gravitationnal attraction to keep the mollecules of the atmo, small planets can only have atmos of heavy stuff such as methane, no hydrogen atmo for them)

Methane isn't heavy (1 carbon + 4 hydrogens is less heavy than a nitrogen molecule). CO2 on the other hand is what one might term "heavy" (mmw of 44).

 

[zanwot]

Methane isn't heavy (1 carbon + 4 hydrogens is less heavy than a nitrogen molecule). CO2 on the other hand is what one might term "heavy" (mmw of 44).

Ah of course, yes. I just mentionned methane off the bat.

 

[zanwot]

Oh and by the way, when I say "chaotic orbit" I mean in a mere *insert number which seems big by human standards but is tiny in terms of age of a solar system* years, the orbits would become variable and eventually one of the 3 objects would get flung away from the system (becoming an isolated brown dwarf or something).

* There cannot be in theory too many (3 or more) large objects of similar mass (3 similar stars, 3 large gas giants) as these cause chaotic orbits.

Depends on the relative placemnt and orbital path/period.
LBH

Yeah, but IIRC they have to be really quite far appart and/or on special (as in improbable enough to be impossible) orbits to not have a problem.

@all: That actually can give a plot hook by the way; Players explore a system where there are 3 (ort more) big similar gas giants, in close orbits, but in the one very *lucky* stable orbit given their proximity (finding this out is fairly easy with decent sensors and a computer), or maybe even given their orbit they *should* have gone "chaotic" by now (this second possibility is a little more technical than the first, maybe not the best for non scientific GMs). Is it just a freak event, or some ancient planetary engeneering?

 

[Rikki Tikki Traveller]

The Three-Body-Limit fails the reality test though.

There are MANY known star systems with 4+ stars in them. They usually form as groups of 2 with a wide separation, but there is nothing inherently limiting about 3 bodies.

 

[EDG]

Oh and by the way, when I say "chaotic orbit" I mean in a mere *insert number which seems big by human standards but is tiny in terms of age of a solar system* years, the orbits would become variable and eventually one of the 3 objects would get flung away from the system (becoming an isolated brown dwarf or something).

...

Yeah, but IIRC they have to be really quite far appart and/or on special (as in improbable enough to be impossible) orbits to not have a problem.

As others have pointed out, it depends on the exact orbital placement and masses. "Three of each" isn't a real limit of anything - you can have as many gas giants or stars as you like, so long as they don't get in the way of anything else. It all depends on how things start off.

There's nothing particularly improbable or special about systems with more than three stars or GGs though.

 

[zanwot]

Arg, people, don't miss quote me! did mention similar masses. (and i should have mentionned similar orbits) Of course you have quadruple systems, with like two close primary stars and far away smallers stars and such. You just don't get triple stars within similar distances and masses, not in stable close orbits. And, suposedly, you should not be able to get get three jupiter sized planets in a system (but you can get multiple gas giants, don't get me wrong again). Anyway...

 

[EDG]

I'm not misquoting you:

* There cannot be in theory too many (3 or more) large objects of similar mass (3 similar stars, 3 large gas giants) as these cause chaotic orbits.

I'm just pointing out that you've got the wrong impression about this (or you're possibly misphrasing something that you're trying to say). Yes, big masses will screw up eachother's orbits, but there's no reason why 3 or more objects of similar large mass can't be in a system if they're far enough apart from eachother.

 

[zanwot]

Arr, forum too limited to have a detailed discussion here. Sorry got carried away. We mostly agree anyway I believe.

 

[Rikki Tikki Traveller]

Got to be careful around us science/engineer types, we take things at face value.

OK, back to your original intent.

YES, you are correct, 3 bodies of approximately equal mass at approximately equal distances (ie similar orbits) are not stable over stellar time periods.

Ok, we are in agreement there.