User:Erdnase

Hey John,

Okay, I did a little bit of research and cribbed some stuff from real life and scientific examples, etc. and came up with something we can at least start with that shouldn't raise too many eyebrows. IE: what I describe here sort of works in one sense or another, although I am taking pretty big liberties and ignoring some complex calculations.

First off, this would be a very special two star system. It could exist (and given the size of the universe, you could say the odds were in its favor) but, in particular the system with three earth type planets showed up for every half million random viable systems this guy online generated. Still not bad, and let's face it -- if you're going colonizing, you're going to do your homework first.

First some general notes:

In 1986, Dvorak designated three categories of traditional binary system orbits.

P-type : the planets orbit the center mass of both stars.

S-type : the planets orbit close to one o the stars and the second is considered a perturber.

Third type: orbits near the Langrangian (L4 or L5) points (also called Trojan points). These planets are stable in orbit around BOTH stars simultaneously. L4 and L5 are very special positions for NASA -- they use them to place crafts in orbits around planets with moons and both Jupiter and Saturn have natural satellites in their L positions.

So, what we are looking for is to have two S-type systems with a potential for bodies at L4 and L5.

I was pleasantly surprised to discover that over 50% of the star systems in the universe are thought to be binary or higher!

Distance Between Stars

How far apart is far enough? Anywhere from a hundred AU to 10,000 AU. Any higher, the gravitational perturbations from other nearby stars will disrupt the orbit. There are many of these observed from Earth. It takes from thousands up to several million years for the stars to complete one orbit.

1 AU = Distance from our sun to our Earth.

If the stars are close, the periodic approach of second stars will cause extremely hot seasons.

For example, a fictional usage of this appears in Brian W. Adliss's Helliconia series -- two stars have a highly elliptical orbit with a period of 2582 years, and an Earthlike planet orbits one star in 480 days. This superimposes a "Great Year" on the ordinary cycle of seasons: when the stars are near pericentron, a global summer lasting centuries ensues.

So, if we keep the stars far enough apart, the second star will appear like a bright star in the sky from the other solar system and have no real super complex effect on things yet still give us proximity that allows realistic travel.

Another reason to not put them too close together is that at moderate separate orbits (less than 100 AUs) there is some speculation as to whether or not planets will be able to form at all. <100. The disk they accrete from would be roiled to much that you would just get asteroid belts, like what happened between Jupiter and our own sun.

The orbits in binary systems are generally markedly elliptical, like squashed footballs. The planets orbit much closer to the sun at times during the year than at others.

Spectral types of stars

G - our sun is a type G, so for simplicity I am going with that.

All right, still with me? Okay. You know me. I like to get things actually solid on paper as soon as possible. We can fuck with it all we want once it's there, but until then, we have nothing. So, in that spirit, for shits and giggles I came up with the following. Remember, I kept this as simple as possible:

Two stars, 200 AUs apart.

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Star 1: Spectral type: 	G Mass:			1 M (the mass of our own sun) Age			10^8 years

Star 2: Spectral type:		G Mass			0.87 M Age			10^8 years

Note, I have both these stars the same age. I doubt that is reasonable, but I haven't yet found much information on it. Nor do I think it really matters. What, if anything, would matter would be the age of the system being entwined. So let's say that is what is I am designating here.

Planetary System around S1:

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P1 	Rock Tidally locked, no atmosphere Distance from S1:	.305 AU	Mass:			.137 EM	Surface gravity:	0.51 EG

Normal Temperature range (Celsius): Min: -192.9 	Max: 435.7

Length of year:	61.66	Earth days (1 local day) Length of day:		1479.88 hours

P2	Rock Tidally locked, no atmosphere Distance from S1:	.404 AU	Mass:			0.046 EM	Surface gravity:	0.35 EG

Normal Temperature range (Celsius): Min: -211.0 	Max: 357.1

Length of year:	93.69 Earth days (1 local day) Length of day:		2248.50 hours

P3	Terrestrial Thin atmosphere (N2, O2 - breathable) Distance from S1:	.988 AU	Mass:			.651 EM	Surface gravity:	.86 EG	Temperature range (Celsius): Min: -25.0 	Max: 49.7 Length of year:	358.46 Earth days (503.26 local days) Length of day:		17.09 hours

P4 	Terrestrial Thick atmosphere (N2, O2 - breathable) Distance from S1:	1.079 AU	Mass:			1.467 EM	Surface gravity:	1.14 EG	Normal Temperature range (Celsius): Min: -4.3 	Max: 34.1 Length of year:	409.19 Earth days (678.89 local days) Length of day:		14.47 hours

P5	Terrestrial Cold, few clouds (N2, O2 - breathable) Distance from S1:	1.148 AU	Mass:			1.037 EM	Surface gravity:	1.01 EG	Normal Temperature range (Celsius): Min: -19.5 	Max: 34.5 Length of year:	449.54 Earth days (702.38 local days) Length of day:		15.36 hours

Planetary System around S2:

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P1	Rock Tidally locked, no atmosphere Distance from S2:	0.325 AU	Mass:			0.092 EM	Surface gravity:	0.44 EG

Normal Temperature range (Celsius): Min: -203.1 	Max: 380.1

Length of year:	72.39	Earth days (1 local day) Length of day:		1737.44 hours

P2	Rock Tidally locked, no atmosphere Distance from S2:	0.495 AU	Mass:			0.008 EM	Surface gravity:	0.19 EG

Normal Temperature range (Celsius): Min: -224.9 	Max: 274.4

Length of year:	136.42	Earth days (1 local day) Length of day:		3274.02 hours

P3	Rock Resonant spin locked, no atmosphere Distance from S2:	0.597 AU	Mass:			0.186 EM	Surface gravity:	0.56 EG

Normal Temperature range (Celsius): Min: -229.4 	Max: 233.3

Length of year:	180.71	Earth days (1.23 local day) Length of day:		3526.56 hours

P4	Water Warm, cloudy, thick atmosphere (N2, O2 - breathable) Distance from S2:	0.873 AU	Mass:			1.564 EM	Surface gravity:	1.17 EG

Normal Temperature range (Celsius): Min: -2.1 	Max: 36.0

Length of year:	319.45	Earth days (514.67 local day) Length of day:		14.90 hours

P5	Martian Cold, Icy, Arid, Few clouds, Thick atmosphere (He - unbreathable) Distance from S2:	1.307 AU	Mass:			1.844 EM	Surface gravity:	1.24 EG

Normal Temperature range (Celsius): Min: -23.8 	Max: 7,1

Length of year:	585.21	Earth days (1017.97 local days) Length of day:		13.80 hours

P6	Ice Cold, Icy, Arid, Cloudless, Thick atmosphere Distance from S2:	2.479 AU	Mass:			1.388 EM	Surface gravity:	1.12 EG

Normal Temperature range (Celsius): Min: -140.1 	Max: -112.4

Length of year:	1528.88	Earth days (2538.56 local days) Length of day:		14.45 hours

P7	Jovian Distance from S2:	4.130 AU	Mass:			460.615 EM 				35.787 EM dust 424.829 EM gas

Exospheric temperature:	61.94 K (-1211.06 C)

Length of year:	3284.34 Earth days (11500.01 local days) Length of day:		6.85 hours

P8	Martian Cold, Icy, Arid, Cloudless, Normal atmosphere Distance from S2:	6.940 AU	Mass:			1.026 EM	Surface gravity:	0.57 EG

Normal Temperature range (Celsius): Min: -192.4 	Max: -156.2

Length of year:	7159.33 Earth days (8470.08 local days) Length of day:		20.29 hours

P9 	Jovian Distance from S2:	14.009 AU	Mass:			411.457 EM				24.783 EM dust 386.675 EM gas

Exospheric temperature:	5.38 K (-1267.62 C)

Length of year:	20517.39 Earth days (63380.93 local day) Length of day:		7.77 hours

P10	Sub-Jovian Distance from S2:	32.213 AU	Mass:			6.657 EM				1.750 EM dust 4.908 EM gas

Exospheric temperature:	1.02 K	(-1271.98 C)

Length of year:	71592.83 Earth days (87385.89 local days) Length of day:		19.66 hours

P11	Rock Cold, no atmosphere Tidally locked, no atmosphere Distance from S2:	43.665 AU	Mass:			0.096 EM	Surface gravity:	0.25 EG

Normal Temperature range (Celsius): Min: -251.1 	Max: -219.4

Length of year:	112987.73 Earth days (88840.25 local days) Length of day:		30.52 hours

Both of these planetary systems would be stable on their own. The stars are far enough apart that the planets aren't going to collide, but I am not taking into account any gravitational affects of the secondary systems. We may not need to. I mean, we don't ever have to say exactly how far anything really is from anything else. We can use this to compute roughly how far things are from each other at any given time.

The only big thing I haven't included here (there are tons of little things of course) is the rate of rotation the two stars circle about each other. If we decide on this, we can also decide on where they currently are in their cycle and get some idea of how far individual planetary bodies in each system are from each other throughout the yearly cycle of the planets.

Also, we can use the Langrange points L4 and L5 of the binary system to either put another potential stable planet in orbit or (and I like this a LOT better) have something in orbit like a space station that THEY put there. Probably best to only use one of the L points. Two would be tricky, from what I have been reading.

This would allow us to have a man-made base of sorts that was accessible to each system without too much traveling involved.

I suggest we put most of our Elysium Corp happy and stable worlds around S1. S2 should be the volatile system being fought over and resource harvested. I especially like the water planet with the breathable atmosphere. So many ideas come to mind for stories involving it.

All of these planets were formed naturally. IE: This is before any terra-forming. Obviously some of them, the ice and Martian worlds, should be able to be modified to support at least minimal life.

Does this at least give us somewhere to start? Can you possibly bounce this off your astronomer friend, or do you think this is asking a little much?

Michael.