key=Some gameobject value=Mass product

gravity constant * mass of the current gameobject * mass of another gameobject

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

[System.Serializable]
[RequireComponent(typeof(Rigidbody))]
public class GravityComponent : MonoBehaviour
{
    public double gravitationalConstant = 6.674 * Mathf.Pow(10, -11);
    public Vector3 startingForce;

    private GameObject[] _bodies;
    private Dictionary<GameObject, double> _massProducts;
    private Rigidbody _bodyRigidbody;

    /// <summary>
    /// Initalize various private values and caches, like the
    /// cache of bodies, masses, etc.