CometLauncher.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CometLauncher : MonoBehaviour
{
        
    [Header("Specify the fixed star(ex: sun)")]
    public GameObject FixedStar;
    [Range(1,1.414f)]
    public float COMET_COEFFICIENT;
        
    [Space(25)]
    public UnivarsalGravitationController UG_Director;
    
    
    void Start() {

        Vector3 myVec = transform.position;
        Vector3 CentralVec = FixedStar.transform.position;
        
        // Calculate launch velocity
        var G = UG_Director.CONSTANT * UG_Director.COEFFICIENT;
        var M = FixedStar.GetComponent<Rigidbody>().mass;
        var r = Vector3.Distance(myVec, CentralVec);
        
        // Calculate launch velocity
        // Launch in a direction normal to the vector between the two points
        float initSpeed = (float)System.Math.Sqrt(G * M / r);
        
        Vector3 initVelocity = 
            Quaternion.Euler(0, 90, 0) * (CentralVec - myVec).normalized * initSpeed * COMET_COEFFICIENT;

        GetComponent<Rigidbody>().velocity = initVelocity;
    }
}