InfiniteStarfield

using UnityEngine;
using System.Collections;

public class InfinteStarfield : MonoBehaviour {
    ParticleSystem.Particle[] points;

    public int starsMax = 100;
    public float starSize = 1;
    public float starDistance = 10;
    public float starClipDistance = 1;
    float starDistanceSqr;
    float starClipDistanceSqr;

    void Start () {
        starDistanceSqr = starDistance * starDistance;
        starClipDistanceSqr = starClipDistance * starClipDistance;
    }

    private void CreateStars() {
        points = new ParticleSystem.Particle[starsMax];
        for (int i = 0; i < starsMax; i++) {
            points[i].position = Random.insideUnitSphere * starDistance + transform.position;
            points[i].color = new Color(1,1,1, 1);
            points[i].size = starSize;
        }
    }

    void Update () {
        if ( points == null ) CreateStars();
        for (int i = 0; i < starsMax; i++) {
            if ((points[i].position - transform.position).sqrMagnitude > starDistanceSqr) {
                points[i].position = Random.insideUnitSphere.normalized * starDistance + transform.position;
            }

            if ((points[i].position - transform.position).sqrMagnitude <= starClipDistanceSqr) {
                float percent = (points[i].position - transform.position).sqrMagnitude / starClipDistanceSqr;
                points[i].color = new Color(1,1,1, percent);
                points[i].size = percent * starSize;
            }
        }
        GetComponent<ParticleSystem>().SetParticles ( points, points.Length );
    }
}