Probing the fate of large primordial perturbations with exoplanets

Abstract

We propose ultra-wide-orbit exoplanets as a novel probe of small-scale dark matter objects. These systems are highly sensitive to gravitational perturbations that could be induced by a Galactic population of compact baryon-free dark matter objects -- whether point-like or extended. Focusing on ultra-compact minihalos, which may arise from large primordial perturbations deviating from the canonical scale-invariant power spectrum, we derive new constraints on their injection scale and amplitude. These constraints complement existing dynamical limits and are expected to improve with upcoming exoplanet surveys. Furthermore, the detection of additional loosely bound exoplanets with these surveys could significantly tighten these constraints. Beyond constraints, we also identify characteristic observational signatures in these systems that could help trace a population of dark matter objects. All this strengthens the potential of exoplanetary science to probe the dark universe back to its very primordial properties.

Comments: V2: 21 pages, 11 figures, a few typos fixed, references added. Matches with the version submitted for peer review