Aupes

After a global chemical war most of humanity has perished. Those who remain exist in isolated communities, not knowing if any other such communities survive. But the situation is getting worse: in one community its leaders know that if they don't leave they'll all be dead in a few years.
There is a planet eleven light years away that might support life. If they can build a ship to get there, and if it is sufficiently Earth-like, and if there isn't a hostile civilisation living there already,...