PlanetSpawner.cs

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using Random = UnityEngine.Random;

public class PlanetSpawner : MonoBehaviour
{
    [SerializeField] List<GameObject> planets;
    [SerializeField] Vector3 spawnVolume;
    [SerializeField] int numberOfPlanets = 100;
    
    [SerializeField] GameObject spaceShip;
    
    void Start()
    {
        GeneratePlanets();
    }

    void GeneratePlanets()
    {
        print("hey");
        
        for(int i = 0; i < numberOfPlanets; i++)
        {
            GameObject go = Instantiate(GetRandomPlanet(), GetRandomPosition(), Quaternion.identity);
            go.transform.parent = transform;
        }
    }

    void Update()
    {
        float distance = Vector3.Distance(spaceShip.transform.position, transform.position);

        if (distance > 100)
        {
            transform.position = spaceShip.transform.position;
        }
    }


    Vector3 GetRandomPosition()
    {
        return new Vector3(Random.Range(-spawnVolume.x, spawnVolume.x), 
            Random.Range(-spawnVolume.y, spawnVolume.y), 
            Random.Range(-spawnVolume.z, spawnVolume.x));
    }
    
    public GameObject GetRandomPlanet()
    {
        return planets[Random.Range(0, planets.Count)];
    }
}