You have to understand that there's just blanks in what can be known. You can make some guesses about how the system may have been sparsely populated, besides the main colony, based on how the Tiger's Claw was not hearing from anyone there, but even that can't be known for sure (communications could have been destroyed/jammed).
As part of any artistic story process, the author makes references to things. So the colony was on the second or third planet in the Goddard System - there should be no expectation that we know details about the other planets. In many cases we do know those kinds of things, but in most cases we don't.