Binary Gravitational Perturbations and Their Influence on the Habitability of Circumstellar Planets

Elke Pilat-Lohinger,Ákos Bazsó

doi:10.3389/fspas.2021.625552

Elke Pilat-Lohinger, Ákos Bazsó

Open Access

https://doi.org/10.3389/fspas.2021.625552

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Abstract

In order to assess the habitability of planets in binary star systems, not only astrophysical considerations regarding stellar and atmospheric conditions are needed, but orbital dynamics and the architecture of the system also play an important role. Due to the strong gravitational perturbations caused by the presence of the second star, the study of planetary orbits in double star systems requires special attention. In this context, we show the important role of the main gravitational perturbations (resonances) and review our recently developed methods which allow a quick determination of locations of secular resonances (SRs) in binary stars for circumstellar planetary motion where a giant planet has to move exterior to the habitable zone (HZ). These methods provide the basis for our online-tool ShaDoS which allows a quick check of circumstellar HZs regarding secular perturbations. It is important to know the locations of SRs since they can push a dynamically quiet HZ into a high-eccentricity state which will change the conditions for habitability significantly. Applications of SHaDoS to the wide binary star HD106515 AB and the tight system HD41004 AB reveal a quiet HZ for both systems. However, the study of these systems indicates only for the tight binary star a possible change of the HZ's dynamical state if the orbital parameters change due to new observational data.

Highlights

Since the discovery of 51 Peg b (Mayor and Queloz, 1995) thousands of exoplanets have been detected so far [see the Extrasolar Planet Encyclopedia1 Schneider et al (2011) or the NASA Exoplanet archive2]
It can be expected that such a configuration has a less violent terrestrial planet formation process than a planetary system where the giant planet is closer to the host-star than the habitable zone (HZ)
We presented recently developed methods to determine the location of secular perturbations for circumstellar planetary motion in binary stars with a special emphasis to planets in the cirumstellar HZ in such systems

Summary

Introduction

Since the discovery of 51 Peg b (Mayor and Queloz, 1995) thousands of exoplanets have been detected so far [see the Extrasolar Planet Encyclopedia Schneider et al (2011) or the NASA Exoplanet archive2]. Of the nearly 3,500 planetary systems none harbors a habitable world similar to planet Earth. This fact raises the question if Earth-like habitability requires a certain planetary system architecture where e.g., giant planets are orbiting the host-star exterior to the habitable zone (HZ). It can be expected that such a configuration has a less violent terrestrial planet formation process than a planetary system where the giant planet is closer to the host-star than the HZ. The giant planet formed probably at a larger distance to the star and migrated inwards by crossing the HZ which could cause problems for the terrestrial planet formation in the HZ.

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