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 Post subject: multi-star systems
PostPosted: Thu Mar 19, 2020 8:29 pm 
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I've been working on and off with a python script for generating star systems. So far it does planets and moons for single or binary systems, but I'd like to try and expand it a bit.

The easiest approach, I think, is to do something like this. Let me know what you think.

  1. Generate primary star
  2. Does this star have a very-close companion? If yes, then planets must be circumbinary
    1. figure out eccentricity and variable luminosity
    2. adjust inner limits for planetary orbits
  3. Does this star have a near-ish companion? (e.g. Alpha Centauri A/B) If yes, then distance and eccentricity will cap max orbit for each. I'm not sure if a star would have both a very close companion and a near companion, so 2 and 3 might be exclusive.
    1. maybe there could be a planet that orbits a star and a near-ish companion? Most likely it'd be Pluto-cold. This one feels slightly headachey to me in terms of doing the python math
  4. Does this star or binary pair have a distant companion?
    1. If yes, then does this star have a close or near companion?

That gets me up to four stars in a system, and I might be okay with that, since it looks like 5-star systems are pretty uncommon.


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 Post subject: Re: multi-star systems
PostPosted: Thu Apr 02, 2020 9:05 pm 
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Looking at the near star data, I think a trinary system with a Close Binary pair and a Near companion is not that uncommon. I think it might make habitable planets almost impossible, but the star formation itself isn't that uncommon.

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 Post subject: Re: multi-star systems
PostPosted: Thu Apr 02, 2020 9:34 pm 
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Cyborg IM1 wrote:
Looking at the near star data, I think a trinary system with a Close Binary pair and a Near companion is not that uncommon. I think it might make habitable planets almost impossible, but the star formation itself isn't that uncommon.


I took the stance that due to the difficulty of even approximating where orbits might lie, only multiple star systems with huge orbits would have planets, anything else I hand waved as having ejected planets from the system.

I don't have a solid number for how distant stars need to be to retain planets, I just winged it based on whether or not the game was served by the presence of planets or not.


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 Post subject: Re: multi-star systems
PostPosted: Fri Apr 03, 2020 8:44 am 
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I'm still planning to write a Firefly-like game set in a 5-star system. Huge orbits will just mean faster handwave drives, so I'd be okay with that. Still wouldn't be fast enough for manned interstellar travel.

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 Post subject: Re: multi-star systems
PostPosted: Fri Apr 03, 2020 4:05 pm 
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The Traveller way of doing it wasn't too bad (IIRC that was planets can orbit individual stars within 1/5 of the stars' separation, and can orbit pairs of stars beyond 3 times their separation). Reality is a bit more complex than that as it depends on their mass ratios though.

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 Post subject: Re: multi-star systems
PostPosted: Fri Apr 03, 2020 6:45 pm 
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Alpha Centauri throws your assumptions out though. There are known planets around all three stars. AB are NEAR (planets around each) and Proxima is FAR - also with planets.

AB orbits from 11-33 AU, right in the middle of the outer planets of the Sol System. :(

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 Post subject: Re: multi-star systems
PostPosted: Fri Apr 03, 2020 6:52 pm 
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Proxima has a confirmed planet, Alpha Centauri doesn't (there was a possibly discovery of a planet around Alpha Centauri B but it was ruled out).

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 Post subject: Re: multi-star systems
PostPosted: Fri Apr 03, 2020 6:53 pm 
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Cyborg IM1 wrote:
Alpha Centauri throws your assumptions out though. There are known planets around all three stars. AB are NEAR (planets around each) and Proxima is FAR - also with planets.

AB orbits from 11-33 AU, right in the middle of the outer planets of the Sol System. :(


Have we an idea of the size and atmosphere of the planets around AB? How eccentric are their orbits?

ETA: My post crossed EDGs.


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