Galaxy

        float x;
        float z;
        float theta = 0;
        float r = 4;
        float rIncrement = 1;
        List<Planet> planets = new List<Planet>();
        do
        {
            if(Random.Range(0,10) <= 7)
            {
                float t = Mathf.Deg2Rad*theta;
                Transform planet = Transform.Instantiate(PlanetPrefab) as Transform;
                x = Mathf.Sin(t)*r;
                z = Mathf.Cos(t)*r;
                planets.Add (p);

            }
            theta += Random.Range(18, 36*5);
            if(theta >= Mathf.PI)
            {
                theta-=Mathf.PI;
                r+=rIncrement;
                if(r >= 50)
                    rIncrement = -1;
                if(r <= 5)
                    rIncrement = +1;

            }
        }while(planets.Count < 50);