Help editing my code, rigidbody attraction force

So I'm creating a simple game. I have a player ball which is travelling though space. I've created a script which creates an attraction force between the player and another object (planet). The planet is static, a force is exerted on the player which attracts it towards the planet. Heres the code:

 using UnityEngine;
 using System.Collections;
 
 public class Planet1GravPull : MonoBehaviour {
 
     public GameObject planet;
     public float gravityFactor = 1f;
     public Rigidbody rb;
 
     void Start ()
     {
         rb = GetComponent<Rigidbody> ();
     }
 
 
     void FixedUpdate() 
     {
         rb.AddForce ((planet.transform.position - transform.position).normalized * rb.mass * gravityFactor / (planet.transform.position - transform.position).sqrMagnitude);
 
     }
 }

So I only managed to get it to work if the script is placed on the player and I then add the planet into the game object variable.

The problem I'm having though is that I have multiple of these planets and with all the scripts on the player, I can't refer to specific scripts for triggers as they all have the same name. The only way I can see to overcome this is by creating separate scripts for each planet with different names however this is very messy and time consuming.

What I want to know is is there a way to differentiate the scripts or a way I can alter the attraction script so I can put it on the planets rather then the player.

Sorry if I'm missing something obvious, I've literally been using Unity for less then a week. Any help is welcome!

Thanks