ReadMe File for PlanWin Terrestrial Planet Simulator ver. 1.1 created by Kevin Sagarsee, March 1997 for Windows 3.1 Disclaimer: This is my first attempt at writing a program for Windows. I make no guarantees that there are no problems that may effect your machine. Use at your own risk. I. Introduction: The purpose of this program is to simulate the late stages of terrestrial planet formation from several small planetesimals into a few planets. For those who have seen my previous DOS version this program is more versatile, capable of multiple runs and variable inputs. These input parameters will be explained below. II. Checks and problems of Interest: I have fixed the control problem that existed in the 1.0 version. The current run can be ended by selecting New System or Exit under the File menu. Then selecting Exit again will end the program. Or you can select New System and start a new run. The program sometimes gives an error when the CANCEL button is hit in the Jovian or Stellar Characteristics window. Closing it out and rerunning the program usually clears it up. The program also supports an array up to 420 planetesimals. If the total of initial bodies and fragmentation add up to greater than this that run is terminated. I have added the option of saving or discarding these results. Previously they were discarded. III. The program screens: A. Initial Screen There is only one pull down menu from it can be selected New System which starts a new simulation, Exit which exits the program and About PlanWin which gives some info on the program. B. Save Under Screen Number of Runs allows you to select how many runs the program will make with the data you enter. From 1 to 100 runs can be made on a single set. Save As selects the location where the data will be stored. The final path will be displayed after you select OK. If it isn't correct hit CANCEL in the next screen and try again. The final filename where data will be stored must be less than 5 characters long. The program appends the run number to the filename for each save. This adds up to 3 characters bringing up the total to 8 characters for the filename. Data for individual runs will be stored as [filename]###.txt. In addition a comma separated file is created that has the data from all the runs made in a format of: run#, dist, eccen, inclin(degrees), mass, radius stored under [filename].csv. Two radio button controls give the option of saving the data from a run that results in runaway fragmentation exceeding the array. The default is to discard these runs. C. Initial Mass Distribution There are four radio buttons from which can be selected the relationship between the initial surface density of solids and distance from the sun. Uniform means that the surface density is the same at any distance. [1/a^1/2] means that the surface density decreases as the inverse of the square root of the distance. [1/a] means that the surface density falls as the inverse of the distance. [1/a^3/2] means that the surface density falls as the inverse of the square root of the distance cubed. Surface Density sets the value for a distance of one astronomical unit(the distance from the earth to the sun). Values between 0 and 1000 g/cm^2 are allowed. Planetesimal Density sets the uncompressed density for the planetesimals. The value must be between 0 and 10. A value of 3.8 is typical. It is modified for compression due to a planet's mass in the program. The earth's uncompressed density is ~4.2 and its compressed density is ~5.5. D. Initial Parameters Initial Time will set when you want the program to start counting. Mass of Central Star sets the star's mass. Values between 0.08 and 5.0 solar masses are acceptable. Region of Runaway influence sets in multiples of hill radii the range from which the initial runaway body collects its mass. Larger values mean larger and fewer initial bodies. Values must be between 1.0 and 10.0. The initial separation between adjacent bodies will be twice the multiple of hill radii inputted here. A value of 2.0 is usually good. Very large values lose their credibility. Min. Orbit Dist. sets the distance of the closest initial body. It must be greater than 0.10 au's. Max. Orbit Dist. sets the distance of the farthest initial body. It must be greater than the minimum. Fraction of Overlap sets the ratio between the periapsis of the outer body to the apoapsis of its inner neighbor. Values between 0.0 and 1.0 can be used. The smaller the value the greater the degree of overlap and the more interaction there is. E. Companion Selection The radio buttons here select the type of companion object there might be orbiting the central star. Jovians include anything up to 0.05 solar masses (~50 times the mass of Jupiter). Stellars include anything above that value. A cutoff distance will be calculated from the parameters of your Jovian or stellar companions. Any planetesimal whose orbit extends beyond this distance is assumed to fall under the influence of the companion and is removed as an escaping object. The companion must be beyond the terrestrial planets you are simulating. E1. Jovian Characteristics Formation time sets when you want the effect of your Jovian planet to start at. Orbit Distance sets the semi-major axis of the Jovian planet. It must be > 0.05 au's. Eccentricity sets the eccentricity of the Jovian's orbit. Mass sets the Jovian planet's mass in solar units. To help out the mass of Jupiter is about 0.001 solar masses. The default values are for Jupiter forming at 5 million years. E2. Stellar Characteristics Orbit Distance sets the semi-major axis of the star. It must be > 0.05 au's. Eccentricity sets the eccentricity of the star's orbit. Mass sets the star's mass in solar units. It must be between 0.05 and 10.0 solar masses and can be greater than the central star's mass. The default values are for alpha Centauri B. If you want alpha Centauri A as your central star set the Central Star Mass under Initial parameters to 1.088. F. Running Screen When the program runs various values are displayed. cutoff distance: the value in au's beyond which planetesimals are removed due to influence of the companion. If No Companion was selected the cutoff distance is set at 0.0 but has no effect. No.Plan.: the number of remaining planetesimals No.Col.: the number of collisions that have occurred. No.Frag.: the number of additional bodies added due to fragmentation. Each fragmentation event results in four bodies of equal mass. Two are stored in the array positions to the original two colliders. The other two are added as new bodies. So No.Frag. increases by two with each fragmentation. No.Esc.: the number of bodies that have escaped from the system. This can occur in two ways. An encounter can result in an hyperbolic orbit or the body may be perturbed so its orbit enters the cutoff distance of a companion. The latter is the most common escape method. No.Lost.: the number of bodies removed due to either fragmentation into pieces less than 0.0001 earth masses or perturbation onto an orbit with periapsis less than 0.005 au's. No. of planets w mass > Mars: the number of bodies whose mass exceed 0.1 earth masses (Mars is 0.1074). secondary resonance for: the planetesimals semi- major axis is within 0.02 au's of a resonance distance with a companion, i.e. it's orbital period is a ratio of the companion's like 4:1, 3:1, 5:2,7:3 or 2:1. Its eccentricity is increased due to the effect of the companion. IV. Output: The program ends each run when the remaining planets are no longer on intersecting orbits. The output for each run includes a section of data on the system as well as the orbit and physical parameters of the final planets. In addition a simple stability criteria developed by Birn is given between each body. Values for this less than one imply that further orbit evolution could occur between the two planets. The criteria is given as: delta = gap/{2.4*R*[(m1+m2)/mstar]^1/3} where gap = difference between the periapsis of the outer planet and apoapsis of the inner planet. R = distance to the middle of the gap m1,m2,mstar are the masses of the planets and the central star. V. Future Plans: In future versions I hope to track the axial tilts and rotation periods of the planetesimals. VI. Conclusion: Please let me know via e-mail of any serious problems you find. I don't guarantee I'll be able to fix them but it will help me out. If there are any questions about the program I'll be happy to answer them by e-mail as well. Kevin Sagarsee ksagars@netusa1.net March 01, 1997 homepage at http://www.netusa1.net/~ksagars