def make_binary_star(mprim, msec, semimajor_axis, eccentricity):
double_star = Particle()
double_star.is_binary = True
double_star.mass = mprim + msec
double_star.semimajor_axis = semimajor_axis
double_star.eccentricity = eccentricity
period = (2 * numpy.pi *
(semimajor_axis * semimajor_axis * semimajor_axis /
(constants.G * double_star.mass)).sqrt())
print("Period =", period.as_string_in(units.yr))
stars = new_binary_from_orbital_elements(mprim,
msec,
semimajor_axis,
eccentricity,
G=constants.G)
stars.is_binary = False
double_star.child1 = stars[0]
double_star.child1.name = "primary"
double_star.child2 = stars[1]
double_star.child2.name = "secondary"
for star in stars:
star.radius = (star.mass.value_in(units.MSun)**0.8) | units.RSun
return double_star, stars
