03-25-2013, 01:09 PM | #11 | |
Computer Scientist
Join Date: Aug 2004
Location: Dallas, Texas
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Re: [Space] Multiple/Lots of Stars in one system
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Yes, sorry, I was thinking about the wrong sort of Zones. :( |
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03-25-2013, 02:42 PM | #12 |
Join Date: Mar 2013
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Re: [Space] Multiple/Lots of Stars in one system
OK, somebody asked for numbers on the system, so here they are
The system is 3.7 billion years old with a F5V primary of 1.35 solar masses Code:
Star Mass Type Average Orbital Radius Eccentricity Value Minimum Separation Maximum Separation 2 1.1 G0 550 .1 495 605 3 .95 G4 1000 .3 700 1300 4 .75 K2 300 .3 210 390 5 .85 G8 350 .3 245 455 6 .5 M0 As for why there are so many distant companions, there's two predesigned habitable worlds in the system (+8 to the roll) and I see the -6 for sub-companions cancelling out the +6 Trianry stars get |
03-25-2013, 03:08 PM | #13 |
Join Date: Mar 2013
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Re: [Space] Multiple/Lots of Stars in one system
This star system is not likely be stable long term, given how severely the orbits of the subcompanion stars overlap. The orbits of 4 and 5 should be adjusted so that their maximum separation is less than 90 AU and preferably about thirty. Alternatively, move Star 3's orbit out by 500 to 1000 AU if you want to keep the subcompanions where they are.
Or take a third option and make a plot point of the instability of this star system. EDIT: More specifically, it would take active means for this configuration to be maintained. Who or what is responsible for this would be up to the GM. The +4 modifier for having a garden world should probably applied only once, as the description for the modifier only makes reference to 'a' garden world. As for the trinary modifier, it only applies to the second companion in a trinary system. As for the rest, see my earlier remarks in this thread. Last edited by Nemoricus; 03-25-2013 at 06:13 PM. |
03-25-2013, 03:42 PM | #14 |
Join Date: May 2005
Location: Oz
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Re: [Space] Multiple/Lots of Stars in one system
Multiple systems are structured as strictly binary trees, with a star at each leaf, and a joint centre of mass at each branching. The orbital separations get a lot smaller, smaller by at least a factor of three, as you go down each layer. And all this is because it makes the orbital systems stable: a reasonably close approximations to a series of nested two-body problems—stable solutions to the three-body problem are unlikely to be struck by chance. Step 19 on page 105 will produce a simple such structure provided that that you do not forget the +6 modifier for a second companion and the -6 modifier to a sub-companion to rolls on the orbital separation table.
In any sub-system of such a system, a pair of stars jointly orbiting a third object create a single forbidden zone, not two. That is because their orbit around each other makes the less massive of them beat out the entire band from their close approach to the third body minus their separation from each other to their distant departure from the third body plus their separation. There is no possible orbit for a planet between their two separate orbits. The GURPS Space 4th system generation sequence treats each pair of objects in orbit to be an ordered pair, with one main object and the other its companion or subcompanion. The main object is always at least equally massive to the companion, and objects orbiting the pair are generated as objects orbiting the main object. Consider the system as a binary tree with the main object on the left and the companion on the right. The most complicated system the sequence can produce is this: Code:
NOT TO SCALE 4 / \ / 5 / / \ 2 c f / \ / \ 1 3 / \ / \ a d b e Letters represent stars. Numbers represent empty centres-of-mass. You proceed by starting with the bottom-left star, which is the main star of the system. Each node above it produces one forbidden zone. When you are generating the systems of companions and subcompanions you proceed only as far out as brings you to a forbidden zone that has already had objects outside it generated. Those were generated as orbiting the system on the left, but they are in joint orbit of the whole system you're working on now. So when you are working on the main star of a system you calculate all its forbidden zones, and then you start at the usual place and work first inwards then outwards. When come to a forbidden zone you skip over it, and start again at its next edge inwards or outwards (as you were going) unless that puts you inside the inner limit or outside the outer limit of the system you are working on. When you are working on a companion of subcompanion you do the same, except that when you go past a forbidden zone onto a link of the graph that has already been done you terminate. The diagram above shows a star a with a near companion b and a distant companion c, where a has a sub-companion d, c has sub-companion e, and c has sub-companion f. It can't get more complicated than that. The order of steps implied by the sequence (in which a is treated as a main star with two companions, and all the rest as companions or subcompanions, is as follows.
In a computer program that treats this as on system rather than six, you might prefer a recursive depth-first approach.
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03-25-2013, 03:48 PM | #15 | |
Join Date: May 2005
Location: Oz
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Re: [Space] Multiple/Lots of Stars in one system
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You take a main star A with two companions, and you roll the orbit of the first companion B with no modifier and the second companion C with a +6. Then each star gets a sub-companion.
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Decay is inherent in all composite things. Nod head. Get treat. Last edited by Agemegos; 03-25-2013 at 03:56 PM. |
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03-25-2013, 03:52 PM | #16 | |||
Join Date: Mar 2013
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Re: [Space] Multiple/Lots of Stars in one system
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Was going to do something like that, a plot point was that Star 3 is going to be the closest it's going for a long time and Star 2 will very close to it at the time, perfect for a slowboat colony trip (Setting is TL 7) Quote:
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03-25-2013, 04:21 PM | #17 | ||
Join Date: May 2005
Location: Oz
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Re: [Space] Multiple/Lots of Stars in one system
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03-25-2013, 04:37 PM | #18 | ||||
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Re: [Space] Multiple/Lots of Stars in one system
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Of course, there is nothing wrong with not caring about that. Just be aware that when you do that sort of thing and then ask SF fans for advice they are going to tell you about it. Quote:
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Decay is inherent in all composite things. Nod head. Get treat. Last edited by Agemegos; 03-25-2013 at 04:47 PM. |
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03-25-2013, 04:48 PM | #19 | |
Join Date: Mar 2013
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Re: [Space] Multiple/Lots of Stars in one system
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03-25-2013, 05:19 PM | #20 | |
Join Date: May 2005
Location: Oz
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Re: [Space] Multiple/Lots of Stars in one system
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There are other solutions to the equations involving rosettes and so forth, but such systems are are never observed in Nature.
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space, system generation |
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