A Habitable, Terrestrial World

The dominant race is going to arise with the S-type star system I created earlier.   The planet in question will be a bit larger than Earth, and possess a higher but still human-tolerable gravity.  It’s less dense than earth, however, which implies that it either has less iron or more water / ice in its makeup.

It will be orbiting the primary star of the system, and as I calculated earlier, it will be orbiting a star 1.2 times the mass of ours at 1.59 AU.  That puts it at the fifth rock from the sun, assuming I decide to use all the orbits.

Property Calculation Full Calculation Unit
Radius 1.49 9,492.790 Kilometers
Mass 3 1.792E+25 Kilograms
Gravity 1.351 13.252 Meters/Second^2
Density 0.907 4.671 Grams/Centimeter^3
Escape Velocity 1.419 15.892 Kilometers/Second
Circumference 9.362 59,644.959 Kilometers
Surface Area 27.899 1.13E+09 Kilometers^2
Volume 13.856 3.58E+12 Kilometers^3

As you can see, that 50% increase in the planet’s radius gave us a much bigger surface to work with than is possessed by Earth, even if we do dedicate a lot of that to oceans.

All we know about the planet at this point is that it’s big and wet.  Yay?  However, we can extrapolate a few things.  This is the home planet of our dominant race, thus it will have possessed resources sufficient to have developed a space-faring culture.  The world will be very highly developed, perhaps at this point in its history it is getting low on natural resources and must import.  Or perhaps the culture upon it strives to preserve its homeworld, and thus conducts most of dirty industry on bases on the neighboring planets or its moon.

Speaking of which, since this is a stable, habitable planet, it needs a moon.  Rings would be cool, but rings make heading into space difficult.  A single large moon will be sufficient.  However, I’m going to make this moon different from Earth’s by messing with its makeup a bit.  It has a solid iron core, but much like it’s planet, it also has a lot of water for a moon.  Thus, it is actually slightly less dense than its host.

Composition Percent Density Calculation Unit
Silicate Rock 70% 3.25               2.28 g/cm^3
Water Ice 12% 0.93               0.11 g/cm^3
Iron 18% 7.87               1.42 g/cm^3
Total               3.80 g/cm^3

For the record, the moon has about 70% the density of Earth, and the planet about 90%.   It’s a good sized moon, bigger than our own and possessing a higher gravity.  As the moon does have a lot of water, it will also look different in the sky.  It may even have a bit of atmosphere.

Property Calculation Unit
Mass 0.020 Earth Mass
Radius 0.300 Earth Radius
Gravity 0.222

Time to figure out the orbit of our moon.   We need the sun’s mass (1.21 solar masses) and the planet’s mass (3 earth masses) as well as the semi-major axis of the planet’s orbit (1.59 AU).  With those numbers, we can calculate the Hill Sphere and the Roche Limit.  Drop in on Artifexian if you need an explanation for those numbers.

Hill Sphere 505.72
Roche Limit 2.25

So the moon must orbit between 2.25 and 505.72 planetary radii from the planet.  I’ll also need to know the inclination and the eccentricity.   I want the orbit fairly circular, so I’m going with a low eccentricity.  Since I also want the moon to stay near the equator, I’m going with a small incline.  Yes, boring.

Orbit 112 Earth Radius
Inclination 2 Degrees
Eccentricity 0.002
Orbital Period 40.11

However, this gives us fairly close to a nice, even, 40 day orbit.  Perhaps 40 is a superstitious number then, to this race.  I’m going to do some work on the planet’s orbit while I’m here.  I am leaving out some data because it isn’t as important and is somewhat arbitrary.

Property Calculation Value Notes
Mass 3.00 Solar Mass (in Solar Masses)
Semi-Major Axis 1.59
Eccentricity 0.03
Orbital Period 1.16 422.50 Earth days
Orbital Velocity 1.37 40.91 kilometers/second
Inclination 0.02
Axial Tilt 20.00
Tropic 20.00
Arctic 70.00

The eccentricity makes the orbit around the sun closer to the circular side, and the low axial tilt also serves to make the planet’s seasons stable.  These guys have it pretty good.

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S-Type Binary Star System

A P-type binary star system has two stars that orbit close to each other, and the system orbits around that.  An S-type system, on the other hand, is two stars that orbit at some distance from each other, and thus may each have their own system.  I’m going to place such a system in my world, each with it’s own set of planets.

Unlike in the P-type system, where you calculate the stars as though they were one entity, in the S-type you treat them separately.  Thus, my results:

Primary Star Secondary Star
Property Calculation Calculation
Mass 1.21 0.75
Luminosity 1.95 0.37
Diameter 0.90 0.56
Surface Temperature 1.10 0.86
Lifetime 0.62 2.05
Distance to Barycenter 153.06 246.94
Eccentricity 0.40 0.50
Maximum Separation from Barycenter 560.00 600.00
Minimum Separation from Barycenter 240.00 200.00
System
Maximum Separation 1,160.00
Minimum Separation 440.00
Inner Limit 0.12 0.08
Outer Limit 48.40 30.00
Frost Line 6.77 2.93
Habitable Zone 1.40 0.60
Minimum Habitable Zone 1.33 0.57
Maximum Habitable Zone 1.91 0.83
Forbidden Zone Edge 146.67

The forbidden zone edge is important.  The outer limits of each system need to fall well inside the forbidden zone to prevent the stars from interfering in each other’s system.  Looks like we are good there, with stars still close enough to be significant in each other’s sky.

We can then lay out the first system like so:

Primary System Orbit In Kilometers
Orbit 1 0.17 24928024.98
Orbit 2 0.29 44122604.21
Orbit 3 0.58 86921530.29
Orbit 4 0.86 128643864.8
Habitable Planet 1.59 237991149.9
Orbit 6 2.37 354606813.4
Orbit 7 4.53 677299013.6
Biggest Gas Giant 7.38 1103997392
Orbit 9 12.32 1843675645
Orbit 10 17.87 2673329685
Orbit 11 29.49 4410993980
Orbit 12 47.18 7057590369

And the second system as:

Secondary System Orbit In Kilometers
Orbit 1 0.10 14766732.9
Orbit 2 0.14 21559430.04
Orbit 3 0.20 30614390.66
Orbit 4 0.39 59085773.97
Habitable Planet 0.72 108126966.4
Orbit 6 1.08 161109179.9
Orbit 7 1.76 262607963.2
Biggest Gas Giant 2.93 438555298.6
Orbit 9 5.39 806941749.3
Orbit 10 8.20 1226551459
Orbit 11 16.15 2416306374
Orbit 12 25.36 3793601008

This system is actually going to form the core of the worlds controlled by the dominant system race.  While humans will exist in this setting, they will not be the dominant race and will, in fact, not be native to this section of the galaxy.  The dominant race originated on the habitable planet in the primary system, and later spread through that system and into the secondary system, where they encountered the much less developed race on the habitable planet there and promptly enslaved them.

P-Type Binary Star System

One of the systems in this little section of the universe will be a binary star system.  Why?  Because it’s cool.  Do I need really need more reason than that?  However, this does affect the calculations a bit, and there are now several other factors to consider.  The two suns combine to give off more light, and also interact with each other to create gravitational fluctuations.  There will also be the cultural considerations having twin suns will mean for the inhabitants of this system.

Again, I’m using Artifexian to provide inspiration. Continue reading P-Type Binary Star System

Creating the Universe

There is a science fiction story that has been kicking around in my head for a while.  I’ve created a rough outline, but I’d like to get some of the science part right.  Now, it’s possible none of this will actually be referenced in the book, but having it on hand helps keep me from making dumb mistakes like two planets being too close together, or a planet being outside the habitable zone, so on and so forth.  I intend to set several stories within this universe, thus it behooves me to make it as accurate as possible.  Plus, this gives me something to focus on right now and I kind of need that.

Continue reading Creating the Universe