>>11820367based on Drake's equation and what we learned about stars and exoplanets since he came up with it, there could be 30 planets with aliens in our galaxy
that is, assuming life actually develops on all planets that are habitable and then won't get extinct again before developing further
but if we assume life develops only on 1 in 100 and intelligent on 1 in 10, it could also be 1 civilization per 300 galaxies
and I think that's pretty optimistic - I mean this had to spontaneously come into being by chance
http://biochemical-pathways.com/#/map/1 
