visible public struct

I have following struct:

 public struct Luminary {
    public Transform transform;
    public maxLightBrightness;
    etc...
 }

in start method:

 public Luminary[] luminary;

now I want to access a value in it:

 luminary[i].transform.Rotate(new Vector3(1,0,0)*Time.deltaTime);

the only problem: I cant drag an drop my luminaries (suns) into the transform slot because the struct doenst show up in the viewer.

how can I solve this? thx in advance