Planets in habitable zones: A study of the binary Gamma Cephei

TL;DR

This study investigates the dynamical stability of potential habitable planets in the Gamma Cephei binary system, identifying a small stable region near 1 AU where Earth-like planets could exist.

Contribution

The paper provides the first detailed dynamical analysis of habitable zone stability in Gamma Cephei, combining numerical integrations and chaos indicators to identify stable orbital regions.

Findings

A stable orbital region exists near 1 AU around the primary star.

Stable orbits are possible for Earth-like planets up to 90 Earth masses.

A small window of stability is found on the inner edge of the habitable zone.

Abstract

The recently discovered planetary system in the binary GamCep was studied concerning its dynamical evolution. We confirm that the orbital parameters found by the observers are in a stable configuration. The primary aim of this study was to find stable planetary orbits in a habitable region in this system, which consists of a double star (a=21.36 AU) and a relatively close (a=2.15 AU) massive (1.7 Mjup sin i) planet. We did straightforward numerical integrations of the equations of motion in different dynamical models and determined the stability regions for a fictitious massless planet in the interval of the semimajor axis 0.5 AU < a < 1.85 AU around the more massive primary. To confirm the results we used the Fast Lyapunov Indicators (FLI) in separate computations, which are a common tool for determining the chaoticity of an orbit. Both results are in good agreement and unveiled a small island of stable motions close to 1 AU up to an inclination of about 15 deg (which corresponds to the 3:1 mean motion resonance between the two planets). Additionally we computed the orbits of earthlike planets (up to 90 earthmasses) in the small stable island and found out, that there exists a small window of stable orbits on the inner edge of the habitable zone in GamCep even for massive planets.