Solar-system-nbody is a n body simulation written in python. It includes a GUI which enables the user to add a limited number of configurations, however the core code can work for as many objects as needed, they just have to be initialised first. The code as it is computes the position data for the planets initialised and then procedes to analyse the data by plotting a number of graphs including the 2D orbit, KE, PE and Momentum of the system. The code uses scipy.integrate.solve_ivp which is a nifty integrator that automatically detects the time steps at which to compute the integration. However all important aspects of the integrator can be changed in the GUI such as the time step (max_steps) and the tolerances (r_tol & a_tol). The objective of Solar_system_nbody is to produce an accurate simulation of the solar system, ideally at quick speeds. In addition to the simulation there is also a plotting of the effective potential and the lagrange points which can be run.

Firstly, check that you have these Python libraries: TKinter, NumPy, Matplotlib. If you have not installed python, I recommend using the Anaconda enviroment with Visual Studio Code as an IDE. Although spyder is typically the main IDE, I find that compatability with spyder and tkinter on MacOSX unreliable at times.

After downloading the code folder the program can be started by running Simulation (GUI).py in the main directory. This will launch the GUI from which you will be able to change a number of variables. The GUI will look like the image given below.

1. Choose what planets / configuration you want to simulate. Either individual planets can be added or specific configurations, otherwise the simulation will not operate as expected. The planets you cann add are ones that resuide in our solar system with the addition of pluto (no longer a planet) and an additional star. For the configurations, these are mainly made up of know analytical soliutions the initial conditions of which are listed below.
2. The type of ODE integrator used can also be changed. Any questions about the differences can be found here.
3. The final edits you can make to this simulation in the GUI are constansts such a G, time period, number of time periods, atol, rtol and interations per time period. All these configurations will be passed through and applied to the script giving you quite a lot of contorl over the simulation.

If nothing is passed into the GUI, the defult simulatiuon will run being that of the Solar System over a 100 period using RK45 as the ODE integrator.

There are 6 scripts. Objects.py, init_objects.py, solar.py, n_body_app.py, Simulation (GUI).py

Contains the class Objects which allows variables such as KE, PE and momenta to be saved to very planet in the system. init_objects uses this class to initialise every planet which could possibly be used in the simulation, this ensure that the user can chose any combination of planets or set configuratioins.

Contains all the functions used for calculating the new positions and energies. The two important functions, one which computes Newtons Laws to feed into the numerical integrator and the second GetEnergies which finds the energies of every particle at every time period.

Initilaises the GUI and enables the user to input the desired inital conditions

This is the script that needs to be run. Once run the GUI will pop up and many steps will be printed in the console telling you whats happening with the script.

• This script calculates and plots the Lagrange points for a two body system. Mu is the relative mass : mu = mass[1]/(mass[0]+mass[1])
• If mu = 0.5, masses are same size. The value of mu can be changed by just editting the value of mu_ratio at top of script

• Repo

• Python

• Improved GUI
• Plotting with Pygame for better visualisation
• Add more unique orbits
• Have plots which lines vary with velocity gradient
• Monitor Evolution of star clusters
• Link the Langrange script with the simulation

Harry Spratt

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