E.Object3D();
  moonOrbit.position.x = 2;
  earthOrbit.add(moonOrbit);

  const moonMaterial = new THREE.MeshPhongMaterial({color: 0x888888, emissive: 0x222222});
  const moonMesh = new THREE.Mesh(sphereGeometry, moonMaterial);
  moonMesh.scale.set(.5, .5, .5);
  moonOrbit.add(moonMesh);
  objects.push(moonMesh);

  // add an AxesHelper to each node
  objects.forEach((node) => {
    const axes = new THREE.AxesHelper();
    axes.material.depthTest = false;
    axes.renderOrder = 1;
    node.add(axes);
  });
