  The characteristic orbital period of the inner-most objects within the
galactic census of planetary and satellite systems appears to be nearly
universal, with $P$ on the order of a few days. This paper presents a
theoretical framework that provides a simple explanation for this phenomenon.
By considering the interplay between disk accretion, magnetic field generation
by convective dynamos, and Kelvin-Helmholtz contraction, we derive an
expression for the magnetospheric truncation radius in astrophysical disks, and
find that the corresponding orbital frequency is independent of the mass of the
host body. Our analysis demonstrates that this characteristic frequency
corresponds to a period of $P\sim3$ days, although intrinsic variations in
system parameters are expected to introduce a factor of $\sim2-3$ spread in
this result. Standard theory of orbital migration further suggests that planets
should stabilize at an orbital period that exceeds disk truncation by a small
margin. Cumulatively, our findings predict that the periods of close-in bodies
should span $P\sim2-12$ days - a range that is consistent with observations.
