  Recent studies of Galactic evolution revealed that the dynamics of the
stellar component might be one of the key factors when considering galactic
habitability. We run an N-body simulation model of the Milky Way, which we
evolve for 10 Gyr, to study the secular evolution of stellar orbits and the
resulting galactic habitability-related properties, i.e., the density of the
stellar component and close stellar encounters. The results indicate that
radial migrations are not negligible, even in a simple axisymmetric model with
mild levels of dynamical heating, and that the net outward diffusion of the
stellar component can populate galactic outskirts with habitable systems.
Habitable environment is also likely even at sub-Solar galactocentric radii,
because the rate of close encounters should not significantly degrade
habitability. Stars that evolve from non-circular to stable nearly-circular
orbits typically migrate outwards, settling down in a broad Solar neighborhood.
The region between $R \approx 3$ kpc and $R \approx 12$ kpc represents the zone
of radial mixing, which can blur the boundaries of the Galactic Habitable Zone,
as it has been conventionally understood. The present-day stable population of
the stars in the Solar neighborhood originates from this radial mixing zone,
with most of the stars coming from the inner regions. The Solar system can be
considered as a typical Milky Way habitable system because it migrated outwards
from the metal-rich inner regions of the Disk and has a circular orbit in the
present epoch. We conclude that the boundaries of the Galactic Habitable Zone
cannot be sharply confined for a given epoch because of the mixing caused by
the stellar migrations and secular evolution of stellar orbits.
