Bright light drifts past window and lights up whole room.

I was lying in bed late at night in the summertime when an oval shaped ,very bright light slowly drifted past my window.  It was so bright it lit the entire room.  I was just a child and was paralyzed with fear and could not move for a few minutes.  I got up and looked out my window and could see nothing but a typical summer night.
I went downstairs where my parent's were playing cards with friends to tell my Mother.  She told me it was the tooth fairy, to go back to bed.  I couldn't sleep for quite sometime. 
I never forgot this incident and always wondered what it was.
Witness indicates that the date of the sighting in 1966 is approximate.  PD