2017’s Noumenon is a standalone generation-ship epic from Marina J. Lostetter.
Reggie Straifer is twice lucky. First, he has boosted his career with his discovery of an enigmatic stellar object, one that is quite possibly artificial. Second, he has made his discovery at a time when humanity has both the means and the will to travel to that distant object.
There’s just one catch: the round trip will take two thousand years by Earth’s clocks and over two centuries by any traveller’s clock. Happily, the means and the will to deal with that issue also exist. Less happily, the means turns out to be inhumane.