I did some math and I think that the closest star is at 1,25 AU from the star. Assuming I got the math right and that all stars are spread out evenly.
That is still pretty far. There are no impacts on the climate at least that is sure.
Interesting enough, they may be in a cluster but when you are inside, you have no idea of this until you have more advanced technology.

The link to the script is on the first page of the tutorial.