Interstellar meteors from the tidal disruption of rocky planets on eccentric orbits around M dwarfs^★

Institute for Theory and Computation, Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
e-mail: morgan.macleod@cfa.harvard.edu; aloeb@cfa.harvard.edu

Received: 16 January 2024
Accepted: 6 February 2024

Abstract

Context. Low-mass stars appear to frequently host planetary systems. When these rocky planets develop high eccentricities as a result of secular torques or dynamical scatterings, they occasionally pass close to the host star. In these close passages, the planets can be tidally disrupted, and sheared into bound and unbound debris tails. To suffer such a disruption, the stellar density must be higher than the planetary density.

Aims. This condition is met for the most common star and planet systems, M dwarf stars hosting rocky planets. We describe the dynamics of a tidal disruption, and estimate the typical velocities of unbound ejecta.

Methods. We simulate the gas dynamics of a planetary tidal disruption, and show that disruptions preserve the layered structure of a rocky body, with the outermost layers flung into interstellar space with the highest velocities.

Results. We compare these properties to those of the candidate interstellar meteoroid CNEOS-2014-01-08 (IM1). IM1's approximately 60 km s⁻¹ excess speed relative to the local standard of rest is naturally reproduced by the unbound debris of the disruption of an Earth-like planet around an M dwarf star. We suggest that such an encounter might explain the interstellar kinematics of IM1, and its unusual composition, especially if it originated in the fastest-expelled crust of a differentiated rocky planet. Finally, we estimate that the disruption of ~10 M_⊕ reservoirs of rocky planets per M dwarf are needed to reproduce the inferred rate of IM1-like objects.