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Looking for a close by triple star system (Read 5799 times)
Basilisk
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Looking for a close by triple star system
10/13/12 at 15:01:54
 
I need help from you, astrophysics gurus and stargazers.
Basically, I am looking for a triple star system that lies in the close vicinity of our sol system.
Something up to 100 light years would be awesome.
That should be some easy task, but I need this system to have a couple of specific characteristics.
 
1st, system must be comprised of two yellow dwarfs (or orange or red dwarfs, if they comply with the HZ needs) that orbit each other in a very close orbit. Orbiting them (or being orbited by them) I need a yellow giant. The main thing here is that the HZs of both the giant star and the two dwarf stars must intertwine. That way, a planet or planets, in the habitable zone of the giant star, will also be in the HZ of the  dwarfs.
 
2nd, that is the hardest physics part, I need at least one planet in that common HZ to be tidally locked to the dwarfs center of mass (that shall be easy, most of the planets on dwarfs' HZs are tidally locked), BUT, also, that planet MUST be in a 1:1 resonance with the giant star orbit around the dwarfs. So, that way, I will have both sides of the planet PERMANENTLY lighted, one heavily lighted (even not so, as the dwarfs won't have enough heat to make it a hell), and the other one dimly lighted.
 
I thought of a couple of solutions for balancing that system, some worked for a couple days simulation, others not.
Here they go:
 
1) If I can have a giant jovian planet that will orbit closer to the dwarfs that may serve two purposes: first, provide gravitational balance so the tidally locked planet can have a, pretty much, circular orbit. And, second, the jovian planet would, somehow, eclipse the light from the dwarfs from time to time, reducing the light/heat reaching the tidally locked planet, so enabling short periods of cooler seasons to happen on that planet's hemisphere facing the dwarfs.
 
2) Another smaller jovian planet in the orbit immediately after the tidally locked super earth may provide for a couple of habitable Earth or Mars sized moons that will float within the HZs of the stars, and will have mostly regular Terran like seasons. (a slower period habitable moon can have something like the long seasons in the ASOIAF story, as, when the jovian planet is in the aphelion the summers and winters in its moons will be cooler, and when the jovian planet is in the perihelion, the seasons will be warmer)
 
3) One (or two) giant jovian planet on the farther orbit from the dwarfs would provide for the space dust cushions that will shield the inner planets moons from asteroids, astray comets and other large evil outer space dust that could destroy the planets, while balancing and straightening the orbits of good space dust, like comets that could carry water to the inner planets/moons during their formative age (the same way Jupiter and Saturn did for our Earth).
 
I am attaching a rough drawing I made with what I tried to explain above.
 

 
So, mainly, if you help me, first, to build that specific system in GravSim, so I can get year periods, seasons (short and long, like Earth's winter/spring/summer/autumn and Ice/Warm age cycles) , precessions and long range planetary bodies interactions in the system (like, when the jovian planets are closer to the inner planets, or the giant star is closer to the dwarfs planetary system, and their gravitational pulls will influence tides, heat cycles, winds and so). I will need your help a second time to fit that fictional system in one of the triple star systems available on that vicinity of our solar system (around 100 light years radius, as I said above).
 
Sorry for the long post, and let me explain, really quick, why I need this specific system. I work with a team of other writers and we do screenwriting, as a third party, for a couple many different TV series. Pretty much, we do the bulk writing, developing the main ideas the authors send to us. That saves their time to imagine and get better ideas, while we deal with the more practical side of make their ideas work on TV. But, we also have our own projects, and for one of those we have been working in this fantasy/sci-fi/steampunk (well, it is coming to that...) universe, which first stories are happening in this planet that got no real night (the tidally locked planet! ta-dah!). In the beginning its mostly medieval/magic fantasy, but we are deriving to something that will involve Newtonian Physics based spacefaring/space fighting, in a close future.
Also, stars and star-navigation are very important to our universe, so would be better to fit our planetary system in some real star system so we can use Celestia to build a star chart of how the skies look for people living on that planet (and now the habitable moons of the jovian planets too).
We been working hard to build a pilot, and it is coming out really good so far. We already promised to send that pilot episode script to one of our friends that is a TV executive, as he loved the idea so far. If the studio likes the pilot, they can budget it, and we will have a shot at their TV series grid/lineup. So, that is a whole bunch of awesomeness in that thing just waiting to happen.
 
Hope you guys can help me (us), and I would love to have "Thanks to our friends in the GravSim forum" in our series credits/dedications.
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Re: Looking for a close by triple star system
Reply #1 - 10/21/12 at 09:48:04
 
Quote from Basilisk on 10/13/12 at 15:01:54:
I need help from you, astrophysics gurus and stargazers.
Basically, I am looking for a triple star system that lies in the close vicinity of our sol system.
Something up to 100 light years would be awesome.
That should be some easy task, but I need this system to have a couple of specific characteristics.

 
According to the nearby star list at Solstation.com, these are all triple star systems within 100ly of Sol (it's most likely not all of them though):
 
Alpha Centauri
40 Eridani
EZ Aquarii
Gliese 570
Gliese 667
44 Bootis
85 Pegasi
CM Draconis
16 Cygni
Algol
 
None of them match your needs though.
 
 
Quote:
1st, system must be comprised of two yellow dwarfs (or orange or red dwarfs, if they comply with the HZ needs) that orbit each other in a very close orbit. Orbiting them (or being orbited by them) I need a yellow giant. The main thing here is that the HZs of both the giant star and the two dwarf stars must intertwine. That way, a planet or planets, in the habitable zone of the giant star, will also be in the HZ of the  dwarfs.

2nd, that is the hardest physics part, I need at least one planet in that common HZ to be tidally locked to the dwarfs center of mass (that shall be easy, most of the planets on dwarfs' HZs are tidally locked), BUT, also, that planet MUST be in a 1:1 resonance with the giant star orbit around the dwarfs. So, that way, I will have both sides of the planet PERMANENTLY lighted, one heavily lighted (even not so, as the dwarfs won't have enough heat to make it a hell), and the other one dimly lighted.

 
As far as I can see, that simply isn't possible. You can have planets orbiting in the habitable zone of a close binary pair, that's not the problem. I suppose you can have a giant star in a more distant orbit, but it'd have to be far enough away to allow a planet to still exist in the circumbinary habitable zone... which may not necessarily be in the giant's habitable zone. The other problem with having a giant there is that it's an evolved star - and a yellow giant is a very brief (in astronomical terms) stage of evolution of a high mass star. High mass stars have much shorter lifespans, so if you say that this started off as a high mass star with a close binary of two G/K/M stars in a distant orbit around it then that implies that the whole system is young (less than a billion years old), which is far too short a timescale to have habitable planets in it. And also, it means that the giant's habitable zone wasn't always there - as the star brightens and expands into a giant, its habitable zone moves outwards quite significantly to how it was during its main sequence lifespan (if you want more info on stellar evolution and other useful worldbuilding stuff, you can check out the info on my Worldbuilding Page).  
 
Then there's the matter of a planet that's in the circumbinary and giant's habitable zones. First, you can't really keep the planet there. It's orbiting the binary pair, so it will enter and leave the giant's habitable zone over the course of its orbit around the binary, because the giant's orbit is much further out and will take longer to orbit the pair. It won't even work like that anyway since the giant and binary will orbit their common centre of mass, which will probably be more like halfway between them - you have to redraw all your orbits in your diagram (other than the two stars of the binary pair) to orbit around the centre of mass (CoM).  
 
However, if you're saying that your habitable planet is itself right on the centre of mass of the system... then that won't work either (I think). That's basically the L1 lagrange point between the binary and the giant, and AFAIK that isn't stable (particularly not with a binary involved, where the distances between the two stars in the binary and the CoM is changing slightly as they orbit eachother, which varies the gravitational tugs on the CoM). Any planet located there would move away from the CoM pretty rapidly and probably would end up in an unstable orbit.
 
Also, there's a problem in that even if you could have a planet just sitting there permanently in the two habitable zones, it would actually end up being rather uninhabitable because both the binary and the giant are keeping it hot. I don't think the temperature adds up linearly, I think it's goes more like the sum of the square root of the luminosities or something like that... but it still basically turns the planet into a furnace (plus there's the fact that there's no night side, which means there's nowhere for the planet to lose heat).
 
The other planets in the system would also have to be in allowable orbits (i.e. not get thrown out by gravitational interactions).  
 
And your diagram won't work anyway... the elliptical orbits aren't centred on the star like that - they would be shifted off to one side because the star would be located in one of the foci of the ellipse (see e.g. the diagram at the top right of wikipedia's Elliptical Orbit page)
 
So basically... your system can't work as described, unfortunately.  
 
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(formerly known as Mal)
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