Bright white orb moving silently across the sky.

While standing outside on our back porch (second floor of an apartment), a bright light which initially appeared to be a bright star, began to move east across the sky in straight line.  It was somewhat overcast at the time of the sighting.  We know it wasn't a satellite as it was below the cloud  cover.  
Additionally, the object remained a constant white light as it moved, with no flashing lights. 
Planes often fly over our house and this object did not have any of the characteristic features typically seen.  The object was also completely silent as it moved across the sky. 
Before the object left our line of sight the brightness gradually faded until it was no longer visible.  The object seemed to remain moving at a constant speed from the beginning of the sighting to the end.