Orbit Perturbations to Habitable Zone Planets from Massive Planets at the Snowline Around M Stars and G Stars

Massive planets may preferentially form just outside the water ice snowline in protoplanetary disks. Here we investigate how massive planets formed at this location would influence the orbits of Earth mass planets located in the habitable zone of Solar type (G) stars and M dwarfs. We performed dynamical simulations that tracked the orbit evolution of an Earth mass planet in the habitable zone and an outer massive planet placed at the system’s primordial water ice snowline. We considered cases with the Earth mass planet placed at different locations in the habitable zone and a Jupiter mass planet at the snowline around G star host stars and with a Neptune mass planet at the snowline around M star host stars. From these simulations, we analyzed the magnitude and timescales of variation in the orbit of the habitable zone planet in each scenario. The snowline is not as separated from the habitable zone around M dwarfs as for Solar type stars, so planets in the habitable zone of M dwarf stars are generally more strongly perturbed than planets in the habitable zone of G stars from massive planets located at the snowline. We found that the average eccentricity of the Earth mass planets is greater the lower the host star mass. The average change in the planet’s semimajor axis also increased with lower host star mass. We will discuss these orbit perturbations in context with the change in solar flux received by the habitable zone planet and implications for its climate.