Terrestrial Circumbinary Planet Formation

We examine the late stage of terrestrial circumbinary planet formation in circumbinary disks that are initially inclined coplanar, polar, or misaligned to the binary orbital plane. While such small planets around binaries have yet to be observed, this is likely due to observational bias. Motivated by recent observations of highly misaligned circumbinary gas disks, we perform a suite of n-body studies to understand the properties of terrestrial planetary systems around various binary systems. In a polar alignment, a circumbinary disk is inclined by 90° relative to the binary orbital plane. First, we find that terrestrial planet formation in a polar configuration may be as efficient as in a coplanar alignment. Secondly, we find that terrestrial planets form only coplanar or polar to the binary even if the initial particle disk is misaligned. Mergers during the formation process lead on average to smaller misalignments from coplanar or polar. These findings have implications for how to tailor future observation campaigns focused on detecting terrestrial planets. If highly misaligned terrestrial circumbinary planets are observed in the future, formation mechanisms other than core accretion in a gas-free environment will need to be considered.