Currently comets are not seen on the star system map unless you've discovered it or bought the discovery from someone else. To discover a comet you'll need to be within one square of it when you perform a scan.
I'm toying with the idea of having comets also provide small amounts of He3 along with magnetic monopoles. This will make them a bit more interesting.
I'm really toying with an idea of having comets have periods in which they disappear and reappear from the system map. I need to game that idea out some more and see how it's going to work. Currently I don't have ships orbit a comet to interact with it, but may consider changing that. My only issue there is that it may give ships a sort of hidden base to orbit where other ships can't see them.
