"Most of my ship's missions so far have been surveys and mapping, but there are quite a few species in the Federation, if you wanna know about aliens." Sure, he could tell her about Nibiru and the primitive civilization there, but he'd rather not open the can of worms that was that clusterfuck of a mission. And if she's preparing to take notes, he hardly wants to tell her anything that might reflect badly on himself or Starfleet.