Star-like object, 4 to 5 times bigger than Mars, with no sound, slowly travelling from over head to the south then slowly dimmed out

Witnessed an object passing slowly and directly above me (90 degrees up the horizon) that moved in a S to SSE direction.  This object took about 15 to 20 seconds to pass over then very slowly dimmed out when it was about 45 degrees up the horizon to the S or SSE.  
It was a solid white, bright object that did not flash like an aircraft (nor was there any sound; I can easily hear aircrafts when passing over).  It was much too big and bright to be a satellite, which I have seen many times.  It did not have a trail like a meteor, it simply looked like a very big, bright star that slowly moved.  
In the South Night Sky, Mars was visible slightly to the West of where this object disappeared and from my perspective this object was about 4 to 5 times larger and brighter than Mars.  
It was hard for me to tell if this object was something big and very close or smaller and further away, but my guess is that it was something many times bigger than an aircraft and at an elevation, maybe half that of the highest flying commercial jets