Where to Find Habitable "Earths" in Circumbinary Systems

TL;DR

This study assesses the stability and detectability of Earth-mass planets in the habitable zones of five circumbinary systems, finding potential stability in some systems and proposing detection methods based on transit timing variations.

Contribution

It provides the first detailed stability analysis of Earth-like planets in these systems and evaluates their potential for detection via transit timing variations.

Findings

Kepler-16's habitable Earth is rarely stable.

Kepler-47 can host a stable Earth near habitable zone boundaries.

Kepler-34, 35, and 38 are likely to support stable habitable Earths.

Abstract

Hitherto, six P-type planets are found around five binary systems, i.e. Kepler-16 b, 34 b, 35 b, 38 b, 47 b, c, which are all Neptune or Jupiter-like planets. The stability of planets and the habitable zones are influenced by the gravitational and radiative perturbations of binary companions. In this Letter, we check the stability of an additional habitable Earth-mass planet in each system. Based on our simulations in 10 Myr, a habitable "Earth" is hardly stable in Kepler-16 while a stable "Earth" in Kepler-47 close to the boundaries of the habitable zone is possible. In contrast, Kepler-34, 35 and 38 seem to have high probabilities of being able to tolerate a stable "Earth" in their habitable zones. The affects of transit time variations are quite small due to the small mass of an undetected "Earth", except that of Kepler-16 b. With a time precision of 0.001 day(~ 88 s), an "Earth" in the corotational resonance with Kepler-16 b can be detected in 3 years, while habitable "Earths" in Kepler-34 and 38 systems can be detected in 10 years. Habitable "Earths" in Kepler-35 and 47 are not likely to be detected in 10 years under this precision.