[Astronomy help] Likelihood of discovery?

[Jareth Valar]

OK, I, at best have Quirk level "Interest in Astronomy", but no real skill or true knowledge, so...

In my game I am having a massive alien "world/generation" ship appear in system about 14-15 AU from Earth, kinda mid way between Jupiter and Saturn.

The "ship" is between SM +28 to SM+31 or so (if I calculated correctly between 56ish and 170ish miles long, not accounting for shape), still playing with Spaceships and campaign ideas, but I do want it "many miles long" type big. Solid TL11^ (same race that was involved in helping defend its hidden interests in my previous question. I'm thinking it does have some stealth from sensors, but given my understanding of the rules in Spaceships I don't really see any point.

My question is, would a TL9 Earth, at the early stages of solar exploration (near Earth mostly) be able to detect it? I know there's always that chance the someone just happens to point a telescope in the right direction at the right time, but what is the general likelihood it would be randomly detected?

I mean the powers-that-be on Earth are looking, but IIRC our own TL8 Earth didn't detect Oumuamua until it was about a quarter AU away or so, and it was moving (extremely fast as I recall), but they still are unsure of it's actual size (anywhere from 100 to 1000 meters or so).

With this "ship" it will be much farther, not within the orbit of a planetary body, so any gravitational affect it would have should be minimal (I think), it's not moving (it arrived via Hyperspace styled FTL drive), I wouldn't say the hull all that super reflective and minimal visible spectrum light (the race see's mainly in visible and UV spectrums (from a world that rarely gets brighter than dusk on Earth).

I'm asking because one or two of the player will likely end up helping in that department during my downtime/time jump. Just wondering if it's even something I should have them even roll for. It will get detected eventually, when it becomes story relevant, but I have no issue if it gets detected early. This is mostly a question for if the powers-that-be would have any real way of finding it before I'm ready, as the players probably wouldn't mention it even if they found it, LOL. They don't really trust those-in-charge.

Sorry for all the odd questions. I my brain needs guidelines and general benchmarks to work from. Like "if an average Soldier is X and an "average" Special Forces is Y, then if I want a character that is comparable or better (but not superhuman) I have something to compare. Just how my brain works, *shrug*.