Firstly, I know none of you (save herr Kerm) know me. But I have a project (one of far too many) which I am working on. This project involves the designing of a Solar system.

While at first glance this would be an easy thing to do seeing how we live in one, naturally I do not want to create something so mundane. It should be noted that this system is for a Role-Playing game and while the reality of this system being created by natural rules is not necessary to be followed, I would like to at least have the system be stable once in place.

The goal is this, to create a habitable, earth-like (in gravity and composition) planet which is in orbit around either one or both stars in a Binary configuration.

The current design calls for 2 stars, one of the approximate size and mass of the Sun, and one the approximate size and mass of Arcturus. As these two stars have very similar Masses (estimates vary between 1.1 and 1.5 solar masses for Arcturus). These stars do have very different Radii as Arcturus is about 25.7 times the radius of the sun.

So, the help I am seeking is this:

1) What would be a stable mutual orbit in order to have either one or both stars have planets (with moons)?

2) Where would the habitable zone around these stars be located?

3) What would the temperatures be like on the planet when between the two stars?

4) What would the Orbit of the Habitable planet be like?

As a side question, using any sized stars needed, would be be possible to have a habitable planet in oscillatory motion between the stars? (likely tracing out an arc rather than an elliptical orbit or a straight line)


Any comments or suggestions would be nice. Thank you.


Miscellaneous information:

Mass of...
Earth: ~6x10^24 kg
Sun: ~2x10^30 kg
Arcturus: ~2x10^30 kg - 3x10^30 kg

Radius of...
Earth: ~65,000km
Sun: ~695,000km
Arcturus: ~17,900,000km

Radius of orbit of... (at aphelion)
Mercury: ~46,000,000km
Venus: ~107,000,000km
Earth: ~149,000,000km
Mars: ~206,000,000km
Jupiter: ~740,000,000km

I'm pretty sure you'd be better off faking it or making something up. i know I wouldn't be able to tell the difference that's for sure.

I would fake it, but extraordinary systems need extra-ordinary work to scientifically support its theoretical existence. Unfortunately, the friend who is assisting me in this design is a former Physics major, and we are both sticklers for detail in things like this. Unfortunately, neither of us are versed enough to figure this out with what we have found. We are stumped.

That would depend on how you want to position your stars. Are the relatively close? Far away? etc... A rough diagram would be very helpful in this regard (including suns and ideas for planet orbits).



If the stars are relatively close and the planet is orbiting around both, my guess would be roughly twice as far away from the center as earth is from the sun, assuming that both stars are producing relatively equal amounts of radiation. If the planet is to move into a position of mostly equidistant from both, I'm not sure it would be habitable as you would have a *huge* temperature shift in seasons not to mention a season of near permanent day light.



See #1



Again, depends on #1.



I don't think so.

Why aren't you modeling this with a software simulation? First step would be positioning the stars so that they have a stable orbit around each other, then start firing planets into different orbitals to find places where the planet will even trace out some kind of reasonable orbit between the two, and THEN start tweaking the parameters to make it habitable for life, looking at temperature estimates, day/night cycles, and possible tidal stresses (though my guess is that these won't be an issue in an orbit that fits the temperature criteria).

I don't know if you've ever played Enigmo 2, but the orbital mechanics of this strike me as being very similar to its game-play. Getting a stable figure-eight orbit between 2 gravitational bodies can be frustrating, but my guess is that it would be a lot less frustrating if you're dragging things around with a mouse than if you're trying to crunch the numbers on your own to come up with an estimate.

The simulation software I have found to date is remarkably wanting. It either has an inability to specify anything with precision, or has an interface that is worse than a GUI created by a middle-school student using BASIC (I am being kind here).

As for Figure 8 orbits, they have been more or less proven unstable without the orbiting object expending energy to alter course.

The idea I have in my head is this:

Star 2: Sun-like with a planetary system similar to ours.

Star 2: Some distance away and in a binary orbit with Star 1. May or may not have planets.

What I need to know basically, is how close the second star can be without destabilizing the system. I do not need brinkmanship, but I would like an idea. My severely rounded calculations suggest that a 2nd star with a mass of the Sun could be located as near at Neptune, but I do not know If this is accurate, or, how that would change the zone of habitability. Similarly, If the mass was greater than the sun, how much further away would that star need to be?



As for simulation software, If anyone knows of any, please point me to it. Preferably something that allows precision placing of objects and does not have an interface that is illegal according to the 8th amendment to the US constitution.

I was thinking more along the lines of writing one yourself. PyOpenGL


Ok, so you're looking not for stars with a shared planetary system, but for 2 stars to be in relatively close orbit of other and each have their own planetary systems......something more along the lines of Lucifer + Sol in Arthur C. Clarke's Odyssey series.

I have a super-old TI program I made somewhere on my profile, but as I recall the precision was on the low side:

[will look and edit later]

(An added bonus, the microscopic implementation of the same for EM fields and particles: http://www.ticalc.org/archives/files/fileinfo/394/39496.html )

Edit: To my great surprise I found I actually never released this anyway, perhaps to improve the accuracy? I'll take a look at it

I would think that Maple would be your friend for something like this. I used it earlier this semester for my Kepler lab in Calc III.

I see your Maple and raise you Matlab.

I raise you one Abacus.

No, the theme was *better* tools for the job, not *worse*. Come to think of it, Nick, I think I wouldn't mind making a Matlab planetary simulator for fun.

Have you ever SEEN an Abacus user? They dominate.

Probably quite far if you want it to be habitable. A stable orbit is going to be relatively easy to achieve even with two stars close together. The problem is going to come in that the amount of light reaching the planet when it is between the two stars must differ in only the tiniest of amounts from when it is on the opposite side of the sun it is orbiting.

In other words, for the planet to be habitable in the system you are describing sun 2 must appear as more or less a normal star in the night sky.

So I randomly came across these calculators: http://www.bumply.com/astro.html#3

Thougths? Do the seem accurate?

I ran a few calculations using very round numbers, and the outputs seemed reasonable, at least for two Sol planets. I'd say try it out and see what it gets you, since you were finding that other equation to believe Earth to be too hot for life

http://blogs.discovermagazine.com/badastronomy/2010/10/22/exoplanets-survive-their-stars-fiery-death-or-were-they-born-from-it/

I saw this article and instantly thought of this topic.

That's a great read, thanks for sharing the article! Very vivid descriptions there in my opinion.

I thought it was very cool that a planetary system existed at all around a binary star.

Definitely, and especially one in such extreme conditions.