I stepped outside of the restaurant where I had just eaten dinner and looked up into the sky. At about 40 degress above the western horizon I saw a brilliant white light. It was "pure" white, it didn't appear to radiate light nor glow, but it was very bright itself. It was moving in a west to east direction. It's altitude could not be determined. My friend suggested that maybe it was the space station, or a satellite, both of which I have seen through binoculars in the past. This object was far, far, too large to be either of those. It appeared to be about equal to 1/3 the diameter of a U.S. dime held at arm's length. It traveled silently from about 40 or 50 degrees above the west horizon, to about 50-60 degrees above the eastern horizon, and then, it instantly disappeared! The actual disappearance was so fast that my mind seemed a bit confused and delivered two simultaneous interpretations of what had just happened. One interpretation was that the object had "turned off" much like a light bulb does when it loses power. But, at the very same instant I thought I registered an extremely faint brownish-thin line projected tangentially from the object's last fully-illuminated position, off into the distance from the object, running for a length that seemed to be 20 to 30 times the width of the object. The object's "disappearance" was confusing because, as I indicated, at the same instant my mind registered the object "switching off" and becoming a speck of brown light that lasted only a millisecond or so, at the very same instant, there was the registering of an extremely thin brownish line running tangentially off into space. That line also lasted a very very short time. (It was kind of like the "trail" a sparkler leaves when quickly run across your field of vision, but thin, like a laser is thin.) I also would mention, that during the 2-3 minutes of this observation, there were aircraft approaching the nearby Portland International Airport and in holding patters with external lights and landing lights on. This object was clearly NOT an approaching nor a landing aircraft. And, I have also watched head-on-approaching, landing approach, landing-lights-on, aircraft, many times, and this object was not one of those. And, also during the time this object was visible, there was an intercontinental jet at cruise altitude directly above us, and this object was certainly not one of those either. There were no visible lights (or anything similar to aircraft lights) on this aircraft. In addition to me, my friend saw the object in the sky (I summoned him from inside the restaurant), however, he did not see the actual "disappearance" occur, but did confirm he didn't see it after I watched it "blink out". I swear this report is accurate and true.