July 4, 2016, 10:37 PM MDTLocation: Worland, Wyoming, 44n 108WI am located about 6 miles out of town and was at my neighbor's house enjoying the fireworks around the valley. At 10:37 PM, a bright light, white in color, caught my attention overhead. The sky was clear with possibly a very thin overcast and stars clearly shining through and no moon. My first thought was it might be fireworks but there was no trail and explosion and it was way too high. The object was about as bright as Venus at its brightest and several times larger. It moved slowly from due south to north covering approximately 20 degrees of arc. Next I thought it might a satellite or the ISS but unless they changed its orbit, the ISS doesn't fly a polar orbit. This was definitely a polar orbital flight path. What makes me think there was a thin overcast is the light plumed. The object itself got very bright and a halo effect surrounded it opening to about 1 degree or a little more than the diameter of a full Moon would appear on the horizon. The halo looked like it might be the exhaust of a rocket going away from me and after perhaps 10 - 15 seconds the object dimmed to a star point and disappeared. As for its location in the sky, it traversed roughly 15 - 20 degrees of arc 3 - 5 degrees west of celestial zenith and 5 south of zenith to about 15 degrees north of zenith.I tried finding information about any NASA launches but nothing came up for this timeframe. I Googled "space launches July 4 2016" but nothing showed. Might this have been a vehicle launch into a higher orbit or something else along that line? What I do know is it was definitely not a meteor, comet, fireball or the infamous "swamp gas" of Michigan. There was no sound except from people around the valley firing off fireworks and by that hour only a few people were doing so anyway. Please let me know what you figure out. I am curious as to what we saw. I might have to invest in a "smart phone" because taking video with my "dumb phone" takes too many steps and I didn't want to miss observing this thing; whatever it was.On a personal note, I am retired Air Force and an Air Force Navigator/Electronic Warfare Officer as well as a private pilot. I am also an amateur astronomer. Thank YouCapt. Gene Leone (Ret) USAF