The Signature of Planet Nine in Earth’s Orbital Elements

An outstanding mystery in the outer solar system is the origin of the unexpected orbital clustering of extreme trans-Neptunian objects observed with semi-major axes in excess of 250 AU. One proposed hypothesis for this alignment is the gravitational influence of a distant, undiscovered solar system planet known as Planet Nine. In this work, we apply the REBOUND orbital integrator to quantify the gravitational influence of the proposed Planet Nine on Earth’s orbital evolution. In particular, we demonstrate the effects of a ninth planet as compared with analogous perturbations induced by relativistic effects, potential stellar flybys, and measurement uncertainties in the Earth’s orbital ephemerides. By examining the collective effect of Planet Nine on Earth’s orbit over Myr timescales, we demonstrate the regions of parameter space in which a Planet Nine could feasibly be ruled out based on the absence of detected perturbations to Earth’s orbit.