Sphere covered by a blueish flame, traveling north to south, 500 to 700 kts at an altitude around 1500 ft AGL.

I was around seven years old at the time, however to this day I can still remember what I saw. I was sitting outside with some friends at around 2000 enjoying the summer weather. As I sat there I noticed what appeared to be a sphere covered by a coat of fire traveling from north to south. As the object passed I was amazed at how well it held it's course and altitude. It did not appear to be producing any type of trail in the sky, we followed it with our eyes until it was not visible. I would have to say that it was at an altitude of about 1500 ft AGL, traveling between 500 and 700 kts. I've always loved flying and currently work in aviation and to this day I know that it was no aircraft. My brother still remembers me running to his room to tell him about what we saw. I whish that I could remember the exact year and date.
Date is approximate.  PD