Milankovitch Cycles for Potential Earth-analogs in Alpha Cen AB


The axial tilt of an Earthlike world influences its yearly-averaged radiative flux can vary for a given latitude. Such variations were realized nearly a century ago through Milankovitch Cycles that describe the frequency and extent of Earth’s ice ages in response to the orbital evolution of the solar system. We examine the global ice distribution for Earthlike worlds in Alpha Centauri AB (and similar binaries) and how such worlds would experience Milankovitch Cycles induced by orbital perturbations from a stellar binary using an energy balance climate model that incorporates ice growth and retreat. An Earth-analog whose orbit is inclined relative to the binary plane can transition between several global ice distribution states similar to Milankovitch Cycles, but there is also a risk for runaway glaciation when ice forms at both poles and the equator. This risk depends on the initial planetary orbit, obliquity, spin precession, binary orbit, and the luminosity of the host star. We conclude that the potential habitability of planets in binary systems require more than an estimation of the radiative flux as determined by previous studies due to the complex gravitational interactions.

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