A growing, lengthening shaft of light, that appeared to be going up in the sky (as opposed to the way a meteor moves).

Husband and wife out walking the dog at 6:24pm on 12/19/23. Avid skywatchers, we were looking up at the clear sky, when we spotted a smallish light in the western sky that looked “different”. We watched it lengthen - to give an idea of its width, from our perspective, it looked like a short pencil line. It looked almost like an ASCENDING fireball - definitely going up, not down! It appeared to be at the same altitude as planes flying overhead - 30,000 - 40,000 feet. Both have experience as trained observers, and after decades of sky watching, have not seen anything like this before. Checked flight app on phone, nothing. Checked with Starlink launches, etc., and that didn’t appear to fit either, although there was a Starlink launch the night before, in Cape Canaveral (2000 miles south of us). Having seen Starlink in the past, it looked nothing like that to us. AND, Starlink didn’t just “disappear” the way this one did.
Unfortunately, being nighttime, the video doesn’t give a good perspective for the viewer to judge distance, altitude, etc.. The surrounding land is wooded and sparsely populated. After zooming in a few seconds into the video, we attempted to keep the camera as steady as possible, to show the movement of the object. (We are including the second video, attempting to photograph the object disappearing. It shows up on the phone, not so much when it’s translated to this computer.). Its trajectory was “straight up”, or appeared to be, from where we were standing (on a mountain in the midcoast region of Maine). After observing for about 1-1.5 minutes, the object seemed to “fade out” and disappear. There was very slight cloudiness here and there in the sky, however, if this object had gone behind a cloud, it theoretically would have emerged at some point. We stood outside for several minutes after the sighting, until it was apparent that it was not going to reemerge.