Getting started

Installation

Syzygy.jl is not a registered package, which means it can be installed using the link to this Github repo. To install it in the REPL, enter the Pkg mode with ] and just type

julia> ] # enter Pkg mode
pkg> add https://github.com/casparwb/Syzygy.jl

Alternatively, from your terminal run

> julia -e 'import Pkg;  Pkg.add(url="https://github.com/casparwb/Syzygy.jl")'

Or, if you want to make changes to the code, just clone the repo and do

julia> ]
pkg> dev path/to/Syzygy.jl

Quick-start guide

A system can be set up using the multibodysystem function, which takes a vector of masses as the first argument, followed by keyword argument specifying orbital and stellar properties. Parameters have to be specified using units from Unitful.jl, which are automatically imported when you load Syzygy.

binary = multibodysystem([2.0, 1.0]u"Msun", semi_major_axis=1.0u"AU", eccentricity=0.1)
triple = multibodysystem([2.0, 1.0, 3.0]u"Msun", a=[0.1, 1.0]u"AU", e=[0.1, 0.2])

Argument aliases

Many of the keyword arguments for multibodysystem have several alises. For example, for the semi-major axis, you can specify any of sma, a, semi_major_axis, semi_major_axes, semimajor_axis, or semimajor_axes. To see all the alises for all the parameters, call Syzygy.multibodysystem_parameter_aliases.

You can also specify a system using only masses, positions, and velocities as positional arguments, and stellar properties as keyword arguments.

three_body_system = multibodysystem([1.0, 1.0]u"kg", [rand(3), rand(3)]u"m", [rand(3), rand(3)]u"m/s", radii=[1.0, 1.0]u"m")

You can simulate the system by calling simulate.

res = simulate(binary, t_sim=1) # simulate for 1 period
res = simulate(binary, t_sim=1u"yr") # simulate for 1 year

Finally, you can postprocess the result to make it easier for further analysis by calling to_solution. This allows you to access the positions and velocities of each body using the fields r and v, in addition to other structural arguments.

sol = to_solution(res)
# r and v is stored as (N_dims, N_bodies, N_timesteps)
r1 = sol.r[:,1,:] # return an (N_dims, N_timesteps) matrix
r1 == sol.r[particle=1]

Syzygy.jl has a few plotting recipes for Plots.jl, which allows you to quickly look at orbits, energy evolution, accelerations, and others.

using Plots

orbitplot(sol) # plot all bodies at all timesteps
orbitplot(sol, dims=[1, 2]) # only plot the x-y coordinates
orbitplot(sol, tspan=(0.0, 1.0)u"d") # only plot the orbit in the given timespan
orbitplot(sol, bodies=[1, 3]) # only plot bodies 1 and 3

kozailidovplot(sol) # plot eccentricities and mutual inclination (only works for triples)