def _planets_only(define_mercury_attributes = False):
data = numpy.array([tuple(entry) for entry in _solsysdat], dtype=[('name','S10'),
('mass','<f8'), ('celimit','<f8'), ('density','<f8'),
('x','<f8'), ('y','<f8'), ('z','<f8'),
('vx','<f8'), ('vy','<f8'), ('vz','<f8'),
('Lx','<f8'), ('Ly','<f8'), ('Lz','<f8')])
planets = Particles(len(_solsysdat))
planets.name = list(data['name'])
print planets.name.dtype
planets.mass = units.MSun.new_quantity(data['mass'])
density = (units.g/units.cm**3).new_quantity(data['density'])
planets.radius = ((planets.mass/density) ** (1/3.0)).as_quantity_in(units.km)
for attribute in ['x', 'y', 'z']:
setattr(planets, attribute, units.AU.new_quantity(data[attribute]))
for attribute in ['vx', 'vy', 'vz']:
setattr(planets, attribute, units.AUd.new_quantity(data[attribute]).as_quantity_in(units.km / units.s))
if define_mercury_attributes:
planets.density = density
angular_momentum_unit = units.MSun * units.AU**2/units.day
for attribute in ['Lx', 'Ly', 'Lz']:
setattr(planets, attribute, angular_momentum_unit.new_quantity(data[attribute]).as_quantity_in(units.J * units.s))
planets.celimit = units.none.new_quantity(data['celimit'])
return planets
