Rotate One Object Around Another

Hello, this has been bothering me really bad for the past hour and i still cant figure it out. Im trying to get one Sphere to rotate around another Sphere. This is my code:

 using UnityEngine;
 using System.Collections;

 public class Shooting : MonoBehaviour {

 public Transform player;

 void Update () {
         transform.RotateAround (player.position, Vector3.up, 20 * Time.deltaTime);
     }

 }

Ive tried so many things to try to get this to work and there has been absolutely no progress, also to be quiet honest i usually dont have these kind of simple problems haha.

Thanks for the help