I go outside every night before I go to bed. Last night at about 9:15 pm I was outside facing South looking up in the sky. It was just past dusk so it was what I consider dark outside and there were a few low clouds above me at that time. I gazed to the WSW and noticed an unusually bright white-bluish light traveling Eastward. It was NOT a Plane of any kind, or a helicopter or blimp. It was not a balloon, It was its own light source. It made NO noise. I followed it as it skimmed a cloud, it was very slightly obscured but it did not have any directional beam of light. What I mean is when airline lights hit clouds or fog, you can see the beam of the light. With this object there was no beam visible. There were NO other visible lights and NO blinking lights. The object did not change shape as it passed over. It was simply a very very bright whitish blue light flying below the cloud ceiling silently from west to east and I watched it until it went behind the tree line out of my line of vision. I Do live in flight paths of commercial , Oregon Air Guard, and private small aircraft. I live east of the Portland International Airport (PDX) and east of the Troutdale airport for many years and I am very familiar with the aircraft and air traffic patterns in my area and this was out of the norm of anything I am used to hearing or seeing. I have never seen anything like it in my life. It was not a celestial event or anomaly either. The speed was fairly slow I cannot even guess how fast it was flying, and I do not know if anyone else witnessed either. From when I first saw the object it was the same and did not change, the light remained constant. I could not distinguish any shape. This object was brighter than anything else I have ever seen in the sky. It was NOT a flare of any kind. It was its brightness and the color of the light that made me notice it, it stuck out and immediately I knew it was something unusual that I had never seen before. My feelings and thoughts were,"[cms/tg/pd], What is that?! Figure's no one is here to examine it with me and my camera is in the house. This all happened in about 35 to 50 seconds.