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PostPosted: Mon Apr 03, 2017 2:22 pm 
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Matt Wilson wrote:
"Near Binaries never have planets. "

2 April, 2017. The day EVIL Dr Ganymede murdered a billion people who only wanted to live in peace on Tirane.


There´s this model that states a binary companion has to be 3.5 times as far from the primary star as the planet - or vice versa - for the planet´s orbit to be stable, isn´t there?

So given the range of distances for Near Binaries (3-25 AU), it should be possible for planets to exist on orbits of less than about 7.15 AU or more than 10.5 AU from the primary, depending on the exact orbital radius of the primary. Even at the closest distance, and orbit of about 0.85 AU or less should be stable. Working within the framework of the Worldgen rules, I´d say we one could just as well replace "Near Binaries never have planets" with "Near Binaries only have planets in the Inner and Habitable zones".

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PostPosted: Mon Apr 03, 2017 3:50 pm 
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"Near Binaries" here are between 3-25 AU. I think I said that here just to make things simpler.

I think I also based that on an article that said something about how planet-forming discs weren't being detected around binary stars with that range of separations?

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PostPosted: Mon Apr 03, 2017 3:54 pm 
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I don't know what percentage of binaries form together versus those that are captured. In collating the data for a near star list (30 light years) I saw eccentric orbits for a lot of binaries. I am guessing they were captured but the math to calculate the orbits is way beyond me. The barycenter of a system with binaries on an eccentric orbit is going to push planets closer to one star or the other at some point and expel or draw them into the star.

With an eccentric orbit it's far far easier to make a sweeping statement like "no planets around binaries" than to calculate what if any, orbits are stable.

The good news is you get rogue planets to play with. They're gonna be chilly cos they're bombing thru space on their lonesome but, if you want a lair for your evil genius...


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PostPosted: Mon Apr 03, 2017 4:07 pm 
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Again, keep in mind this is somewhat simplified ;). It's basically designed to create the stars and the mainworld - you could potentially use it to generate other planets in the system if you knew what orbital zone they were in but you'll note there aren't any specifics like luminosity, orbital distance and eccentricity here.

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PostPosted: Mon Apr 03, 2017 5:20 pm 
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EDG wrote:
Again, keep in mind this is somewhat simplified ;). It's basically designed to create the stars and the mainworld - you could potentially use it to generate other planets in the system if you knew what orbital zone they were in but you'll note there aren't any specifics like luminosity, orbital distance and eccentricity here.


Yes, this is not so much a star system generator as a more realistic way to generate UWP data, including attendant info like star type, planetoid belt and gas giant presence.

And it does that very well, too!

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Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards. Sir Frederick Hoyle
Earth is the cradle of humanity, but one cannot live in a cradle forever. Konstantin Tsiolkovsky
Man has earned the right to hold this planet against all comers, by virtue of occasionally producing someone completely bat**** insane. xkcd #556
Just like people, stars can be very important without being terribly bright. Phil Plait, "Bad Astronomy"


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PostPosted: Mon Apr 03, 2017 5:38 pm 
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"Simplified?" I'm on to you Ganymede. You won't get away with this. The sons and daughters of Tirane will never forget.

Image <-- super judgy nemesis

All nonsense aside, I like the stuff about presence of GG and chance of planets around different types of stars. I remember reading something about GG tending toward smaller around M stars but don't remember where I saw that.

Also I guess the part about no hab-zone mainworlds around M5+ was put together before TRAPPIST-1 showed up and said "LOL surprise!" :)


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PostPosted: Mon Apr 03, 2017 6:41 pm 
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Oh, Colonel Young, you were such a pratt :P

Matt Wilson wrote:
Also I guess the part about no hab-zone mainworlds around M5+ was put together before TRAPPIST-1 showed up and said "LOL surprise!" :)


Yeah this is based on what I came up with for the original MGT playtest, so it comes from way before Trappist-1. Easily tweaked though, just say that stars up to M7 use the same modifier as the M2-M4 V (DM+5) on the Mainworld Orbital Zone.

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