How could I calculate the distance to recieve the nearest object to the player?

 using System.Collections.Generic;
 using UnityEngine;
 
 public class FindNearestPlanet : MonoBehaviour
 {
     // You need to store a list of all of the planets
     // If you add them procedurally, you need to update this list each time to add or remove a planet
     private List<Transform> planetTransforms; 
     private Transform targetPlanetTransform; // The current planet we are moving to if we find one
     private Transform playerTransform;
     private float minDistance = 10f;
     private float flyingSpeed = 5f;
 
     // State of player
     private bool onPlanet = false;
     private bool flying = false;
     private bool foundPlanet = false;
 
     private void Update()
     {
         if ( onPlanet )
         {
             // You would put the code to rotate the player with the planet in here, ok?
             // If you are setting the planet as parent of ship, the ship SHOULD rotate with the planet,
             // If the planet is rotating
 
             if ( Input.GetKeyDown( KeyCode.Space ) )
             {
                 // Change state of player
                 onPlanet = false;
                 flying = true;
 
                 // Detach from the planet
                 playerTransform.parent = null;
             }
         }
         else if ( flying )
         {
             if ( !foundPlanet )
             {
                 // If the player is flying but not found a planet, move the ship
                 // Again, you would have to calculate the x and y speeds based on the angle of your ship when it left the planet
                 // So this line is just example
                 playerTransform.Translate( new Vector3( flyingSpeed , flyingSpeed , 0 ) );
 
                 // Then we check for the nearest planet
                 int closestIndex = 0; // Keep track of index in the list of planetTransforms
                 float shortestDistance = 100; // Used to compare each distance, I put it at 100 to start for simplicity
                 float currentDistance = 0;
 
                 // Loop through the list
                 for ( int i = 0; i < planetTransforms.Count; i++ )
                 {
                     currentDistance = Vector3.Distance( playerTransform.position , planetTransforms[ i ].position );
 
                     if ( currentDistance < minDistance && currentDistance < shortestDistance )
                     {
                         // if the distance to the current planet in the list is closer than the previous shortestDistance, store the list info
                         closestIndex = i;
                         shortestDistance = currentDistance;
 
                         // So once we find it we arent checking distance every frame
                         foundPlanet = true;
                     }
                 }
 
                 // Once we are done looping, we have the index of the transform with the clostest distance, so we set that
                 // So our ship can move to that location (targetPlanetTransform)
                 targetPlanetTransform = planetTransforms[ closestIndex ];
             }
             else // Otherwise if we found a planet, move the player towards it
             {
                 playerTransform.position = Vector3.Lerp( playerTransform.position , targetPlanetTransform.position , 0.125f );
 
                 float distanceToPlanet = Vector3.Distance( playerTransform.position , targetPlanetTransform.position );
 
                 // Or whetever distance u like,
                 // You may have to do a little calculation if you want the ship to go right on the edge of the planet
                 if ( distanceToPlanet < 0.1f )
                 {
                     Vector3 direction = Vector3.Normalize( playerTransform.position - targetPlanetTransform.position );
                     float radius = targetPlanetTransform.localScale.x / 2;
                     Vector3 edgeOfCircle = targetPlanetTransform.position + ( direction * radius );
 
                     playerTransform.position = edgeOfCircle;
                     playerTransform.SetParent( targetPlanetTransform );
 
                     // Set state
                     flying = false;
                     onPlanet = true;
                 }
             }
         }
     }
 }

Thank you very very much, but i'm too inexperienced to adjust the script (to my scene). I'm really new at Unity. I´ve uploudet the project in a zip file: http://www.mediafire.com/file/d5kp6bsy636g3oo/SUNRUN.zip/file.

best regards