Silent orb passed nearly directly overhead in the pre-dawn morning.

It was such a warm summer morning, so I stepped out into my backyard with a cup of coffee and took a moment to few the stars.  Nearly directly overhead a saw a light in the sky that I thought was an airplane coming into Denver Airport.  It was tracking the same flight path as most flights coming in from the west do.  Something was a little different this time.  What I first thought were landing lights were not.  It was the glow of the craft itself that I saw.  I looked for flashing beacon lights on the wings but there were none.  In fact, I could now tell there were no wings.  It was a simple orb.  It was traveling east northeast.  It was headed in the direction of DIA.
As I continued to watch, it made a gentle turn to the southeast.  That is when I realized it was silent.  I said to myself "What am I watching?"  As it moved away from me, I was completely convinced that this was not a plane.  If it were a plane and with it past me now the landing lights would no longer be visible.  The orb was still just as bright as ever as it moved further and further away from me.  Finally it vanished beyond the trees.
((
ISS.  Please see: 
http://heavens-above.com/PassSummary.aspx?satid=25544⪫=39.6133&lng=-105.0166&loc=Littleton&alt=1631&tz=MST
PD))