merge_recipes.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Recipes for merging particles to form new or bigger stars
"""

from amuse.datamodel import Particle, Particles
from amuse.units import units


def merge_two_stars(primary, secondary):
    "Merge two colliding stars into one new one"
    colliders = Particles()
    colliders.add_particle(primary)
    colliders.add_particle(secondary)
    new_particle = Particle()
    new_particle.mass = colliders.mass.sum()
    new_particle.position = colliders.center_of_mass()
    new_particle.velocity = colliders.center_of_mass_velocity()

    return new_particle


def form_new_star(
        densest_gas_particle,
        gas_particles,
        # density_threshold=
):
    """
    Forms a new star by merging all gas particles within a Jeans radius of the
    densest particle. Returns the new star and all particles used to make it.
    """
    new_star = Particle()
    gas_copy = gas_particles.copy()

    # densest_gas_particle = gas_copy.sorted_by_attribute("density")[0]
    jeans_radius = 0.025 | units.parsec  # 100 | units.AU
    gas_copy.position -= densest_gas_particle.position
    gas_copy.distance_to_core = gas_copy.position.lengths()
    dense_gas = gas_copy.select(
        lambda x:
        x < jeans_radius,
        ["distance_to_core"]
    )
    new_star.mass = dense_gas.mass.sum()
    new_star.position = (
        dense_gas.center_of_mass()
        + densest_gas_particle.position
    )
    new_star.velocity = dense_gas.center_of_mass_velocity()
    new_star.radius = jeans_radius
    absorbed_gas = dense_gas

    return new_star, absorbed_gas