Well the universe is filled with stars including the sun which is also considered a star. So Astronaut the term the US and some other countries use seems to apply well and Cosmonaut which is the term the Russians use also applies but not quite as well in my mind.
They come from different countries, so there's no point in arguing.
In terms of scope, the cold reality is that nobody is leaving our solar system if we don't crack faster than light travel, which is more than likely not possible to do.
Given that both nations (Russia and the US) are actually doing nothing more than polluting outer space with their useless rockets and not going to any star for the next millenia, I would say that cosmonaut is the most appropriate for what those nations are doing right now. I know it will displease the US but that it is a fact.
For we who grew up believing that the USSR was our enemy, you can't remove this meaning from those two words. It doesn't really matter what astro and cosmo mean in any other context.
In practical use it seems that "astronauts" purpose was studying stars constellations etc. whereas cosomology was often reserved as the term that would have been almost synonymous with god. It still carries a slightly mystical connotation at least it seemed to until the Soviet Union launched the first dog into space. Very lovely lips
Because stars are mainly just balls of gas, it is really difficult to explore them, so cosmonaut (discovering the universe) seems more in-touch with what people who explore space are actually doing.
I selected "either if fine" but my personal preference is "astronaut" because I like the idea of "reach for the stars". Doesn't sound as good when you say "reach for the universe."
Either is fine. Essentially, unless we're able to get out of our own solar system or make colonies on the moon and Mars, we might have nowhere to go after we screw up the Earth.
