Extreme Habitability: Formation of Habitable Planets in Systems with Close-in Giant Planets and/or Stellar Companions

TL;DR

Recent simulations demonstrate that habitable Earth-like planets can form and remain stable in systems with close-in giant planets or stellar companions, challenging previous beliefs about their inhospitability.

Contribution

This paper reviews simulation results showing the potential for terrestrial planet formation in extreme environments with close-in giants or binary stars.

Findings

Terrestrial planets can form in habitable zones despite disruptive giant planets.

Water-rich Earth-like planets are possible in these extreme systems.

Long-term stability of such planets is feasible in certain configurations.

Abstract

With more than 260 extrasolar planetary systems discovered to-date, the search for habitable planets has found new grounds. Unlike our solar system, the stars of many of these planets are hosts to eccentric or close-in giant bodies. Several of these stars are also members of moderately close ($<$40 AU) binary or multi-star systems. The formation of terrestrial objects in these "extreme" environments is strongly affected by the dynamics of their giant planets and/or their stellar companions. These objects have profound effects on the chemical structure of the disk of planetesimals and the radial mixing of these bodies in the terrestrial regions of their host stars. For many years, it was believed that such effects would be so destructive that binary stars and also systems with close-in giant planets would not be able to form and harbor habitable bodies. Recent simulations have, however, proven otherwise. I will review the results of the simulations of the formation and long-term stability of Earth-like objects in the habitable zones of such "extreme" planetary systems, and discuss the possibility of the formation of terrestrial planets, with significant amounts of water, in systems with hot Jupiters, and also around the primaries of moderately eccentric close binary stars.