I was traveling back to the store that I work at coming back from a pizza delivery, around six o'clock in the evening, on Old Ashland City Road. I heard a military helicopter flying over. The helicopter was was very loud and low to the ground. So I looked up and beside the helicopter was a bright reddish orange ball of light. The Orb was about 20 to 30 feet to the side of the helicopter, it was not in the front,or in the rear, or on the belly side of the helicopter. Helicopters do not have lights to the side of the helicopter 20 to 30 feet the helicopter.The lights are usually on the bottom or on the front or in the back connected to it. This light was not connected at all. The orb stayed in pace with the military helicopter until they both flew out of site. The light that this orb was giving off was at least 10 times brighter than what the helicopter had , if not brighter. Some of the Ft Campbell helicopters fly low all the time. And I have seen many helicopters from the past 30 yrs I have lived here. This was an event that really made me stop my car to see what this was.