On The History and Future of Cosmic Planet Formation
  We combine constraints on galaxy formation histories with planet formation
models, yielding the Earth-like and giant planet formation histories of the
Milky Way and the Universe as a whole. In the Hubble Volume (10^13 Mpc^3), we
expect there to be ~10^20 Earth-like and ~10^20 giant planets; our own galaxy
is expected to host ~10^9 and ~10^10 Earth-like and giant planets,
respectively. Proposed metallicity thresholds for planet formation do not
significantly affect these numbers. However, the metallicity dependence for
giant planets results in later typical formation times and larger host galaxies
than for Earth-like planets. The Solar System formed at the median age for
existing giant planets in the Milky Way, and consistent with past estimates,
formed after 80% of Earth-like planets. However, if existing gas within
virialised dark matter haloes continues to collapse and form stars and planets,
the Universe will form over 10 times more planets than currently exist. We show
that this would imply at least a 92% chance that we are not the only
civilisation the Universe will ever have, independent of arguments involving
the Drake Equation.
