def new_solar_system_for_mercury():
"""
Create initial conditions for the symplectic integrator Mercury, describing
the solar system. Returns a tuple consisting of two particle sets. The first
set contains the central particle (sun) and the second contains the planets
and Pluto (the 'orbiters'). The positions and velocities are in heliocentric
coordinates.
Defined attributes sun:
name, mass, radius, j2, j4, j6, Lx, Ly, Lz
Defined attributes orbiters:
name, mass, radius, density, x, y, z, vx, vy, vz, Lx, Ly, Lz, celimit
"""
planets = _planets_only(define_mercury_attributes = True)
centre = Particles(1)
centre.name = 'SUN'
centre.mass = 1.0 | units.MSun
centre.radius = 0.0000001 | units.AU
centre.j2 = .0001|units.AU**2
centre.j4 = .0|units.AU**4
centre.j6 = .0|units.AU**6
centre.angularmomentum = [0.0, 0.0, 0.0] | units.MSun * units.AU**2/units.day
return centre, planets
