I was riding my dirt bike when I saw an unusually wide contrail in the distance.I then stopped to study it.It was a black saucer shaped object with a white exterior light on the bottom.It moved about the speed of an airplane at about 30,000 feet up in the sky.It stayed in the same direction of east north east making a turn that was hardly noticable.I followed it for about 7 minutes, and then went inside and checked flight aware live flight activity near Joliet Illinois.There only one airplane in the area,a Southwest Airlines Boeing 737-700 desending at 5000 feet,going in for a landing at Chicago Midway International Airport,which is only about 32 miles away.I know that an airplane must be 16,500 feet up to produce a contrail,so it was the object was not an airplane.I felt very nervous at the time I saw the object. That is the reason I quickly rode home and checked flight aware.I lost sight of the object when it went out of my viewing distance.