Maedhros said:[noob question] So, empty hexes on the star map are actually empty (i.e. contain nothing but empty space) rather than being occupied by a star that lacks a useable system of planets? That would make it so that every star in a sub-sector had planetary bodies, which is perhaps a bit of a stretch.[/noob question]
I'm not sure if it's ever been made explicit anywhere that empty hexes are indeed completely empty (I don't have my books on hand right now to check). I can't recall offhand what CT says when you're rolling for system presence - whether a failed roll means that nothing is there at all, or just that there's no system that anybody is interested in enough to put on the map.
But one of CT's quirks is that by default if it is determined that a system is present in a hex, then it MUST contain planets (unless later on the rolls make it so that it's a multiple system that's ejected all the planets, or you get some weird combination of empty orbits filling up every available orbit). But you can't roll up a system that contains just the star(s) and no planets (not in book 3 anyway).
When it comes to astronomy and astrography, this is by no means the only thing that could be considered a "stretch" - for example, the proportion of habitable planets generated in Traveller is undoubtedly way higher than reality (current evidence indicates that it's pretty unlikely to get a habitable planet in the right orbit around the right type of star with the right kind of lifespan, and then you have to worry about jovians migrating inwards and disrupting the orbits of rocky planets too - put that all together and you get significantly reduced probabilities of habitable worlds).