Hang on, that's not Andromeda...
...THIS is Andromeda - http://serialy.mirekholy.net/data/andromeda/wallpapery/lexa%20doig/Lexa%20Doig%20%28Andromeda%29%20-%20Wallpaper%20-%20IronFin%20Studios.jpg
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The European Space Agency (ESA) has released an impressive composite snap of the closest spiral galaxy to the Milky Way – an infrared and X-ray mélange showing Andromeda in all its glory: ESA's composite image of Andromeda The Herschel space telescope captured the infrared component of the image (shown in red/orange), while …
Assuming we leave this system anyway, but I'd always understood that on an individual star system level, they actually were not likely to collide with anything, may be alter their galactic orbit, but not a lot else.
To quote "Space is big. Really big. You just won't believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space, listen" the likelihood of two solar systems in an obscure spiral are hitting each other are infinitesimally small.
Wouldn't want to hang out in the galactic cores though, whoops there goes another billion year old sun.
It's not healthy for our sort of life to be within a hundred light-years of a supernova. When galaxies collide, it triggers the formation of new stars. The heavy ones live fast and exit as a supernova. This might well matter a lot to our distant descendants ... or more realistically, mean that our sort of life on dry land is unlikely to evolve or survive in a cosmologically-recently-collided galaxy.
Betelgeuse, the red giant in Orion, is just about far enough away to be safe (~400 light years). Good thing too, since there is a fair chance it'll go supernova within a few thousand years. Statistically, the incidence of mass extinction events in the fossil record and the probable incidence of dangerously close supernovae are similar.
If you think supernovae are bad, read up about gamma-ray bursters, and pray that whatever gives rise to these events, there isn't one of it it about to go bang in this galaxy!
It's not likely.
These events seem to occur only earlier in the universe and are probably first-generation stars signing off.
And even then, they are unlikely to be unidirectional. You need to be in the beam path to get a good dusting.
And they have to be "relatively" close, too:
http://researchnews.osu.edu/archive/gammaray.htm