Possible number of planetary systems in the galaxy

A method for estimating the number of planets and planetary systems in the Galaxy is presented which takes multiple stellar systems into account. The effects of star mass, the presence of substars, and the degree of system multiplicity are analyzed in deriving expressions for the upper limit of the probability of planet formation around a given star. The quantitative evaluation of the equation parameters is discussed. For a model of the Galaxy containing 2 x 10 to the 11th stars in systems of not more than four stellar components, a planetary-formation probability of 0.23 and a total number of planetary systems of 4.6 x 10 to the 10th, (of which about 120-140 are within 10 pc) are estimated.