CRA Cosmic Coffee: Billy Quarles

Title: Obliquity Evolution of Earthlike planets in α Centauri AB

Abstract: Changes in planetary obliquity, or axial tilt, influence the climatic conditions on a potentially habitable planet, where orbital perturbations from a binary star companion can drive these changes to extremes. We study the evolution of planetary obliquity for an Earthlike planet in the habitable zones of α Centauri AB, our nearest stellar neighbor, through numerical simulations. Additionally, we explore the effects on the spin precession due to terrestrial neighbors and the presence of a moon. From our simulations, we uncover low variability regions of phase space that depend on the secular orbital precession as well as starting values for the mutual inclination relative to the binary planet, the spin longitude, and the initial obliquity. Moreover, we find that the added precession from a large moon typically destabilizes the host planet’s obliquity allowing up to 40° of variation. The consequences for climate on such worlds will be influenced by orbital, flux, and obliquity variations, where we will discuss and compare the variations on an Earthlike planet in α Centauri AB with those in the solar system.