My wife and I were on a cruise through the Alaskan Inside Passage aboard the MS Norwegian Pearl. It was approximately 9:30pm PDST. The night sky was clear with no mist, fog or clouds anywhere in sight. The seas were calm. Our position which I checked via GPS after the incident and then factored in the time and distance traveled subsequently was about 51���02.23' N 128���38.26' W.Our stateroom was an outside cabin on the port side towards the bow of the ship. We went out on the balcony to view the stars and the water. No moon was visible and the staterooms to either side of us had no outer lights on so visibility was excellent. According to the ship's GPS broadcasts over the stateroom TV the ship was traveling at 22 knots with a compass bearing of about 338 degrees.Ahead of the ship and about 10 - 20 degrees off her port bow and above us I noticed a bright light heading in a straight line along the side of the ship at about 11 o'clock. It was coming directly towards the ship but on a parallel, not an intercept course. The light was brighter than any star, and brighter than Venus on a clear night. It was also more of a dingy, yellowish white rather than the white or bluish light of stars and planets. There was no flicker to it nor was there any changing of color.I directed my wife's attention to the object and noted that it was approaching the ship but only very slowly; far less than the speed at which an approaching aircraft would have been moving. We both looked for any sign of flashing strobes or of the standard red/green lights lights on conventional aircraft but there were none. If I had held a new pencil out at arms' length the eraser would have just been big enough to cover the object, but just barely so.The object passed above and along the length of the ship and passed by our position over a period lasting about 5 minutes. Both my wife and I continued to look carefully for any signs of a strobe or navigation lights but there were none, not when it was in front of the ship, not when it was directly perpendicular to our position and not after it has passed us by. We also listened closely for any sounds of engines. There were none. As the seas were very calm and any wind consisted mainly of that generated by our ship's own forward motion, noise levels were very low. We would easily have been able to hear a plane or helicopter engine. Since there was no cloud cover at all we had no way to accurately determine the object's altitude. I think it was probably no less than 1000 feet and probably no more than 3000, but that's a very subject estimation. The object did not pass near enough to any bright stars for us to detect whether there was a greater bulk behind the bright light or not. After about 5 minutes the object simply faded from view over the course of less than 10 seconds. One moment it was very bright, then next it was fading, fading, fading, gone. As it faded out there was no deviation in any direction from its original course. We looked carefully to see if there might have been some very nebulous, low-lying clouds it could have ducked behind, but we could still clearly see faint stars in the same area the object had disappeared in. They were faint, but not obscured by clouds. The object simply disappeared.My wife and I stood discussing what we had just seen and kicking around all of the possibilities. We were confident it had not been an aircraft in any conventional sense. It was completely silent and had none of the normal running lights required. We considered whether or not it could have been some sort of balloon. The fact that we were approaching it at 22 knots and yet it took about 5 minutes to travel such a short distance to get past us suggested it may have been moving in the same direction our ship was traveling only at a slower speed. Still, we thought, if we had grossly misjudged its altitude, perhaps it was some type of balloon and the slowness of its approach had been due to its extreme height.We chewed things over like this for about another 5 minutes when all of the sudden the object reappeared in its full brightness at about the same position relative to the ship it had vanished at. This time it kept exact pace with the ship and fell no further behind. It was, however, now moving on an intercept course perpendicular to the ship. It took about 2 minutes to traverse a distance equal to the length of my thumb held out at arms' length at which point it made a course deviation back up to the north and then reversed course away from the ship before correcting once again in the opposite way so that it was again approaching. Both my wife and I noted this course change at the same time so it was not a trick of the eyes. It was clear an unambiguous.There was still no sound and still no other lights of any kind associated with it. Once again it began to fade from view only this time the fade was slower. It took nearly a full minute for the object to fade to the brightness of a very dim star but it was clearly visible the whole time. Once it had reached this level of brightness it continued to move towards the ship for another 2 to 3 minutes, very slowly and visible at all times. When it had traveled about twice the distance of my thumb again it disappeared entirely.We waited for several more minutes on the balcony to see if it would reappear. It did not. However, it seemed to us highly unlikely that any type of balloon would have drifted at high altitude past the ship then held position and followed the ship while executing first a 90 degree turn so as to head towards the Pearl, then a letter S type maneuver, then headed back towards the ship again while keeping pace with it. So we ruled out the balloon hypothesis. We couldn't come up with any other plausible explanations. The ship never deviated from its course the whole time so were were not being fooled by apparent motion of the object. There was no sound, no other lights, and no flickering or twinkling of the object's light. We ruled out all the things we're sure it was not. We just couldn't come to any firm conclusion as to what it actually was.