Another stellar navigation question:

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Old School
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Another stellar navigation question:

Postby Old School » Mon Jan 14, 2019 11:09 pm

The Mongoose supplement for the Inurin system describes it as a trinary system, with a yellow-white main sequence star orbited by two red dwarfs, with each star having it's own orbiting bodies. Most of the system's planets orbit the main star, but one of the dwarves also has an inhabited planet, and both have rock balls and asteroid belts viable for mining.

Any of our astronomers want to make a stab at how far apart these dwarves would have to be from the larger star for this system to work, i.e. for each to have its own stable planetary system?
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Re: Another stellar navigation question:

Postby paltrysum » Tue Jan 15, 2019 12:24 am

I was just reading a paper on the subject of trinary star systems:

I don't normally read stuff quite this techy, but red dwarves and multiple-star systems fascinate me since they are so abundant.
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Re: Another stellar navigation question:

Postby Condottiere » Thu Jan 17, 2019 10:23 am

As I understand this stuff, if the orbits have stabilized, more or less, over the course of hundreds of millions of years, some form of equilibrium was worked out by all existing gravitational wells.

The orbits may be decaying, as all things do, but not a factor within the span of humanity's existence.
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Re: Another stellar navigation question:

Postby phavoc » Thu Jan 17, 2019 6:56 pm

Well, 'stable' is a variable term in this case. Look at Alpha centauri/Proxima centauri. It's a trinary system, but the two Alpha stars, both yellow dwarves, have an eccentric orbit, and they pass anywhere from 11 to 30 AU from each other. And Proxima is way the hell out there at 15,000 AU.

The orbits of the stars are relatively stable and they each have their own solar system. We've spotted some planets in both.

It's hard to answer your question since the orbital mechanics can be tricky. If the orbits are matched well enough a planet might never go between two stars. Then again, if a planet orbiting star A only gets 11AU from the secondary star (and depending out the stellar sequence), it may barely register the effects of said star on it's biosphere. Mars is 1.5 AU away from the sun, to give an example. At 10AU the solar output of our sun is relatively small, especially if you want to consider it for a life-bearing planet.
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Re: Another stellar navigation question:

Postby ShawnDriscoll » Thu Jan 17, 2019 8:05 pm

Stick one planet where Earth is. Stick one red dwarf where Saturn is. And stick the other red dwarf where Neptune is. Treat the orbiting stuff around the red dwarves as rings and moons.

Anything more "realistic" than that, the players won't give any "F"s about.
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Re: Another stellar navigation question:

Postby Rikki Tikki Traveller » Mon Jan 21, 2019 5:22 pm

Rule of 3s

A planet must be closer than 1/3 of the distance between stars or more than 3 times the difference between them.

Red dwarfs tend to have VERY close planets, so two red dwarfs separated by 2-3 AU (Mars to Belt) is plenty of room for many planets around each star.

Put the Yellow star about 20 AU away (Neptune) and you have plenty of room for quite a few planets. The yellow star could have planets out to Jupiter (using our solar system and orbits) without any problem.

Very doable.
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