and out of the ~200,000,000,000 visible galaxies there are on average ~600,000,000,000 stars in each galaxy, with a 50-70% chance that around 90% of those stars harbor planets, the total stars in the universe being 1.2x10^23 and using the previous percentages we can conclude that there are 1.0x10^23 stars possible for planets with a 50-70% chance of those to harbor planters so we can take 60% of that and come out out 6.48x10^22 solar systems in the universe. Then you can take those and say on average there are 3 planets (usually only 1 visible in recent findings from kepler mission, though many more planets are estimated to be possible up to 30 orbiting one star.) so we can say that there are roughly 2.0x10^23 planets in the universe. Now out of those planets that are possible, there is a rough percentage of them located in the Goldilocks zone, 5%. That leaves 8.0x10^20 planets with the possibility of life. take the right time of civilization evolution and the right conditions on what we know for the characteristics of life on earth, and that is .001 of the planets which leaves us with an astonishing number of 8.0x10^17 planets with 100% chance for life. This is revolutionary! Though contact with most of these places are nearly impossible. We have only talked about Planets harboring life, we have not spoken about the possibility of lunar life in the universe which is a whole different story, because an estamate of the total moons in the universe is 3.4x10^24.
Also:
where:
N = the number of
civilizations in our galaxy with which communication might be possible;
and
R* = the average rate of
star formation per year in
our galaxy
fp = the fraction of those stars that have
planets
ne = the average number of planets that can potentially support
life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop
intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space.
