Stop being so critical about what is "real" and what is not. It's a game, get over it. Whether it's green/purple stars or sound you could also argue light/warp speed. There are many things that are not possible as currently known, are any of these game breaking, no as if they were, I hope your not science fiction fans of Star Trek, Star Wars, Stargate, or most other sci-fy movies.
This is a rather hostile response to a simple request to not have sound effects that are non-sensical or outright bad. My point was that there should simply be a way to implement sounds in space battles that didn't seem so awkward or misplaced. Yea, you can play with the sound off - but when the game is designed in such a way that sound is a dominant indicator for the player as to what's going on, it crimps the game.
I wasn't suggesting that the game should be played in an absolutely dark room, wearing ear plugs with the AC on full blast so it "feels" more like space, and that stardock should make a hyper-realistic space simulator... I was merely suggesting that the sound effects for space ships better represent space ships, rather than sounding like a bunch of tanks, mechs, seagoing vessles, etc. Don't you think that you'd be annoyed if you were playing a submarine warfare game, and there were tank-track noises every time your sub repositioned? or torpedo-like sounds every time you airplane dropped a bomb? Yea, I would too - so why should this be any different in this situation?
To get to your other points, It's my understanding that stars produce all kinds of EMR, but am not an expert on specific predominant wavelengths of different star types - so I won't comment on the green/purple star issue...
We haven't developed FTL travel yet, although if you follow the human speed trajectory we theoretically should by ~2038 (not that you'll be on a spaceship doing this by 2038, just that we will have developed the technology and demonstrated the ability to do so - see the numerous writings of Ray Kurzweil as a reference). There are 3 dominant theories on mechanisms for FTL travel - wormholes, warping space, and somehow utilizing the casimir effect (this remains poorly understood currently) - there are also some fringe ideas that are less likely to work on relativistic scales such as quantum tunneling, quantum teleportation... anyway, the point is that just because we cannot do these things at the current time, doesn't mean that we never will be, or they don't fit into a futuristic game. If you really wanted to get serious about these types of things, you could make the argument that most of space is actually empty, and the vast majority of it is intergalactic space, which is so far away from everything that you would have no way of knowing which direction to travel to leave it (photons from the nearest galaxy generally would not reach you). But alas, GC is predicated on exploration and discovery, and I like the game predicated on exploration and discovery as opposed to a game bogged down 99% of the time by being lost in intergalactic darkness. The game, however, is not predicated on bad sound - nowhere have I ever seen any indication that the GC outline/story involves poor audio effects. Seriously, go back and play GC2 - the combat sounds are bad dude. It's really not too much to ask that they not be bad, is it?
I personally hate Star Trek (call me a heretic), not because of the sound effects (apparently this is a reason not to like the whole franchise?), mostly because of the weak plot outlines, the exceptionally weak moral outlines, and the exceptionally unoriginal depiction of a universe that's supposedly teeming with life and technology. Yea, I like Star Wars, it's a human drama and a human story, I was disappointed by the directing of EP 1-3 - but who wasn't? SG I don't recall much of, I watched the movie a really long time ago, seemed alright. Personally, I really like the depiction of space in Firefly (a bunch of hicks in space, can't go wrong), and Alien(s). If anything, the depiction of space being cold, harsh and unforgiving enhances the experience of watching these movies/shows, as opposed to detracting from it...
So I guess I wasn't looking for a flame war, or pissing contest, I was merely observing that "space sounds" could be done a lot better. I don't really see why this is so debatable (or turns into a debate of "no sounds" vs "status quo space sounds").