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.

I’ve been watching Artifexian’s videos.  His mathematical calculations aren’t perfect, but they’ll get me close enough for my purposes.   This story will require several planetary systems in fairly close proximity to each other.  Each system will be different, but for the sake of ease I’ve decided to start with the system closest to our own Sol.

The star will have a solar mass of 1.2 times our own sun.  This allows me to calculate the following:

Property Calculation Notes
Mass 1.200 Number Chosen by Me
Luminosity 1.728 Mass ^ 3
Diameter 0.888 Mass ^ 0 .74
Surface Temperature 1.096 Mass ^ 0.505
Lifetime 0.634 Mass ^ -2.5
Habitable Zone 1.315 Square Root of Luminosity
Minimum Habitable 1.249 95 % of the Habitable Zone Number
Maximum Habitable 1.801 137% of the Habitable Zone Number

There.  We have our sun.

Now, it’s time to find the boundaries of this system.   While yes, I’m aware I’m an American, I’m going to use kilometers for my math.  It’s a more sensible system anyway.  An astronomical unit is the distance between our sun and the earth, or 149,597,871 kilometers.  Memorize that number, it will probably pop up in some kind of trivia situation eventually.   The inner boundary is the distance at which the sun will simply eat the planet, and the outer boundary is the point at which the sun’s gravity is so weak any astral body can escape.  The frost line is that lovely point in which things like water, methane, ammonia, carbon dioxide, and carbine monoxide will all freeze into solid ice grains.

Property Calculation In Kilometers Notes
Inner Boundary 0.12 17,951,744 Mass x 0.1
Outer Boundary 48.00 7,180,697,808 Mass x 40
Frost Line 6.38 953,759,815 The square root of Luminosity x 4.85

Yay, we’ve established our boundaries.  Time to start putting things into them.  The biggest gas giant will form within 1 to 1.2 AU of the frost line.  Handy starting point for placing our planets.   Each planet’s distance from the star will be 1.4 to 2 times the distance of the previous planet’s distance from the sun.  No two planets will be within .15 astronomical units of each other.  For this, I used a handy random number generator.  That gave me the following list of orbits:

Planet Orbit In Kilometers Check <0.15 AU Apart
Orbit 1 0.18 27,088,207 0.15
Orbit 2 0.33 49,367,297 0.18
Orbit 3 0.51 76,294,914 0.23
Orbit 4 0.74 110,935,555 0.69
Habitable Planet 1.43 214,105,622 0.82
Orbit 6 2.25 336,145,827 1.55
Orbit 7 3.80 568,086,447 3.15
Biggest Gas Giant 6.95 1,039,598,199 4.17
Orbit 9 11.12 1,663,357,118 5.23
Orbit 10 16.34 2,445,134,964 9.15
Orbit 11 25.50 3,814,410,544 11.22
Orbit 12 36.72 5,492,751,184

Conveniently, it also generated a habitable planet without me having to fudge any numbers.  Yay.

It’s also conveniently given me a planet fairly close to the habitable range, for an astronomical definition of the word close.  Not inhabitable by itself, but perhaps a location the local species could establish some kind of presence.   The planet is on the warmer side of the habitable zone, which incidentally happens to be perfect for the creatures I have in mind to place there.

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