Planetary Systems Associated with Main-Sequence Stars.

The luminosity function is used to estimate the number of invisible planet-like objects in the neighborhood of the sun, taking into account the likely chemical composition of planets in relation to the composition of main-sequence stars. There may be about 60 objects more massive than Mars for every visible star. An attempt is made to estimate the distribution of these planet-like cold bodies in relation to stars. It is suggested that stars, together with cold objects, were formed in clusters of bodies of random size distribution. Clusters averaging about 50 bodies each account for the observed distribution of frequencies of double and triple star systems relative to single stars. On this basis, virtually every star should have a planetary system associated with it. As a corollary, systems of cold bodies in which there are no luminous stars should be abundant. The possible distribution of planets around such stars has been studied, making use of the observed orbital characteristics of double star systems. It is concluded that favorable conditions for life processes may be far more abundant than has generally been thought possible.