irigi/accrete2

accrete2

This program is based on an article by Martyn Fogg in the Journal of the British Interplanetary Society (JBIS) called 'Extrasolar Planetary Systems: a Microcomputer Simulation'. In it, he described how to generate various sun-like solar systems randomly. Since he did a good job of listing references, I decided to implement it in Turbo Pascal on my PC.

Later, I translated it to C for portability, and the result is what you see in front of you. Because of my need to run this on an IBM-PC, there are two makefiles included with the program: 'Makefile' (for unix systems), and 'starform.mak' for MS-DOS systems. To create the executable on a unix system, type in 'make' alone; type 'make starform.mak' if you are on an MS-DOS machine and using Microsoft C.

Thanks go to Sean Malloy ([email protected]) for his help with the random number routines and to Marty Shannon ([email protected]) for the lisp-style output format, command-line flags, and various other pieces.

Enjoy, and if you find any glaring inconsistancies or interesting pieces to add to the simulation, let me know and I'll include it in any other distributions I send out.

Now for some references. These are not the only good references on this subject; only the most interesting of many that were listed in Fogg's article in vol 38 of JBIS:

For a good description of the entire program: "Extra-Solar Planetary Systems: A Microcomputer Simulation" Martyn J. Fogg, Journal of the British Interplanetary Society Vol 38, pp. 501 - 514, 1985

For the surface temperature/albedo iterative loop: "The Evolution of the Atmosphere of the Earth" Michael H. Hart, Icarus, Vol 33, pp. 23 - 39, 1978

For the determination of the radius of a terrestrial planet: "The Internal Constitution of the Planets" D. S. Kothari, Ph.D. , Mon. Not. Roy. Astr. Soc. Vol 96, pp. 833 - 843, 1936

For the planetary mass accretion algorithm: "Formation of Planetary Systems by Aggregation: A Computer Simulation" S. H. Dole, RAND paper no. P-4226, 1969

For the day length calculation: "Q in the Solar System" P. Goldreich and S. Soter, Icarus, Vol 5, pp. 375 - 389, 1966

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I can be reached at the email address burdick%[email protected]

Here is a sample solar system:

Accrete - V3.0; seed=0x00000005 SYSTEM CHARACTERISTICS Stellar mass: 1.00 solar masses Stellar luminosity: 0.99 Age: 4.429 billion years (5.628 billion left on main sequence) Habitable ecosphere radius: 0.996 AU

Planets present at: 1 0.341 AU 2 0.505 AU 3 0.877 AU 4 1.047 AU 5 1.793 AU 6 2.956 AU 7 5.160 AU 8 8.852 AU 9 13.121 AU 10 28.450 AU 11 46.864 AU

Planet 1 Planet is tidally locked with one face to star. Distance from primary star: 0.341 AU Mass: 0.220 Earth masses Surface gravity: 0.59 Earth gees Surface pressure: 0.000 Earth atmospheres Surface temperature: 193.31 degrees Celcius Equatorial radius: 3893.8 Km Density: 5.314 grams/cc Eccentricity of orbit: 0.092 Escape Velocity: 6.71 Km/sec Molecular weight retained: 17.63 and above Surface acceleration: 578.24 cm/sec2 Axial tilt: 22 degrees Planetary albedo: 0.081 Length of year: 72.89 days Length of day: 1749.33 hours Boiling point of water: -273.0 degrees Celcius Hydrosphere percentage: 0.00 Cloud cover percentage: 0.00 Ice cover percentage: 0.00

Planet 2 Planet is tidally locked with one face to star. Distance from primary star: 0.505 AU Mass: 0.202 Earth masses Surface gravity: 0.57 Earth gees Surface pressure: 0.000 Earth atmospheres Surface temperature: 112.78 degrees Celcius Equatorial radius: 3786.9 Km Density: 5.310 grams/cc Eccentricity of orbit: 0.091 Escape Velocity: 6.52 Km/sec Molecular weight retained: 18.65 and above Surface acceleration: 561.97 cm/sec2 Axial tilt: 28 degrees Planetary albedo: 0.060 Length of year: 130.99 days Length of day: 3143.70 hours Boiling point of water: -273.0 degrees Celcius Hydrosphere percentage: 0.00 Cloud cover percentage: 0.00 Ice cover percentage: 0.00

Planet 3 Distance from primary star: 0.877 AU Mass: 0.165 Earth masses Surface gravity: 0.53 Earth gees Surface pressure: 2.702 Earth atmospheres GREENHOUSE EFFECT Surface temperature: 45.57 degrees Celcius Equatorial radius: 3541.1 Km Density: 5.302 grams/cc Eccentricity of orbit: 0.015 Escape Velocity: 6.10 Km/sec Molecular weight retained: 21.36 and above Surface acceleration: 524.69 cm/sec2 Axial tilt: 29 degrees Planetary albedo: 0.038 Length of year: 300.44 days Length of day: 40.82 hours Boiling point of water: 129.5 degrees Celcius Hydrosphere percentage: 100.00 Cloud cover percentage: 0.00 Ice cover percentage: 0.00

Planet 4 Distance from primary star: 1.047 AU Mass: 1.515 Earth masses Surface gravity: 1.15 Earth gees Surface pressure: 1.889 Earth atmospheres Surface temperature: 19.01 degrees Celcius Equatorial radius: 7328.1 Km Density: 5.494 grams/cc Eccentricity of orbit: 0.017 Escape Velocity: 12.84 Km/sec Molecular weight retained: 4.81 and above Surface acceleration: 1125.13 cm/sec2 Axial tilt: 22 degrees Planetary albedo: 0.297 Length of year: 391.74 days Length of day: 14.68 hours Boiling point of water: 118.4 degrees Celcius Hydrosphere percentage: 67.12 Cloud cover percentage: 61.38 Ice cover percentage: 1.06

Planet 5 gas giant Distance from primary star: 1.793 AU Mass: 6.262 Earth masses Equatorial radius: 18997.9 Km Density: 1.303 grams/cc Eccentricity of orbit: 0.002 Escape Velocity: 16.21 Km/sec Molecular weight retained: 3.02 and above Surface acceleration: 691.87 cm/sec2 Axial tilt: 29 degrees Planetary albedo: 0.500 Length of year: 877.67 days Length of day: 15.54 hours

Planet 6 Distance from primary star: 2.956 AU Mass: 0.453 Earth masses Surface gravity: 0.75 Earth gees Surface pressure: 0.207 Earth atmospheres Surface temperature: -136.53 degrees Celcius Equatorial radius: 4941.6 Km Density: 5.356 grams/cc Eccentricity of orbit: 0.140 Escape Velocity: 8.55 Km/sec Molecular weight retained: 10.86 and above Surface acceleration: 739.66 cm/sec2 Axial tilt: 18 degrees Planetary albedo: 0.634 Length of year: 1857.62 days Length of day: 17.62 hours Boiling point of water: 61.1 degrees Celcius Hydrosphere percentage: 0.00 Cloud cover percentage: 0.00 Ice cover percentage: 81.12

Planet 7 gas giant Distance from primary star: 5.160 AU Mass: 69.313 Earth masses Equatorial radius: 41830.7 Km Density: 1.351 grams/cc Eccentricity of orbit: 0.299 Escape Velocity: 36.35 Km/sec Molecular weight retained: 0.60 and above Surface acceleration: 1579.66 cm/sec2 Axial tilt: 42 degrees Planetary albedo: 0.512 Length of year: 4284.26 days Length of day: 10.28 hours

Planet 8 gas giant Distance from primary star: 8.852 AU Mass: 11.727 Earth masses Equatorial radius: 26059.7 Km Density: 0.946 grams/cc Eccentricity of orbit: 0.182 Escape Velocity: 18.95 Km/sec Molecular weight retained: 2.21 and above Surface acceleration: 688.64 cm/sec2 Axial tilt: 47 degrees Planetary albedo: 0.509 Length of year: 9626.17 days Length of day: 15.57 hours

Planet 9 gas giant Distance from primary star: 13.121 AU Mass: 557.816 Earth masses Equatorial radius: 83066.4 Km Density: 1.389 grams/cc Eccentricity of orbit: 0.083 Escape Velocity: 73.18 Km/sec Molecular weight retained: 0.15 and above Surface acceleration: 3223.89 cm/sec2 Axial tilt: 33 degrees Planetary albedo: 0.454 Length of year: 17357.91 days Length of day: 7.20 hours

Planet 10 Distance from primary star: 28.450 AU Mass: 0.372 Earth masses Surface gravity: 0.40 Earth gees Surface pressure: 0.000 Earth atmospheres Surface temperature: -222.05 degrees Celcius Equatorial radius: 6182.7 Km Density: 2.246 grams/cc Eccentricity of orbit: 0.000 Escape Velocity: 6.93 Km/sec Molecular weight retained: 16.54 and above Surface acceleration: 388.05 cm/sec2 Axial tilt: 57 degrees Planetary albedo: 0.149 Length of year: 55468.32 days Length of day: 24.33 hours Boiling point of water: -38.3 degrees Celcius Hydrosphere percentage: 0.00 Cloud cover percentage: 0.00 Ice cover percentage: 0.10

Planet 11 Distance from primary star: 46.864 AU Mass: 0.283 Earth masses Surface gravity: 0.36 Earth gees Surface pressure: 0.000 Earth atmospheres Surface temperature: -233.50 degrees Celcius Equatorial radius: 5653.0 Km Density: 2.236 grams/cc Eccentricity of orbit: 0.047 Escape Velocity: 6.32 Km/sec Molecular weight retained: 19.88 and above Surface acceleration: 353.22 cm/sec2 Axial tilt: 54 degrees Planetary albedo: 0.157 Length of year: 117268.25 days Length of day: 25.50 hours Boiling point of water: -45.5 degrees Celcius Hydrosphere percentage: 0.00 Cloud cover percentage: 0.00 Ice cover percentage: 0.08