Ultra-wide-orbit exoplanets set new limits on primordial power spectrum amplitude at small scales
The arXiv analysis proposes ultra-wide exoplanets as sensitive probes of small-scale primordial perturbations via minihalo-induced perturbations. It derives new limits on injection scale and amplitude that complement existing dynamical constraints and improve with future surveys. Characteristic signatures in orbital distributions could trace a dark matter population back to inflation.
The paper derives encounter rates and impulse approximations for a Galactic population of minihalos with masses 10^-10 to 10^-3 solar masses, mapping injection scale k_inj and amplitude A to survival fractions of loosely bound planets at 100-1000 AU. Orbital integrations demonstrate that even rare encounters produce detectable eccentricity jumps or ejections within 10 Gyr, directly tracing deviations from near-scale-invariant P(k) at wavenumbers inaccessible to CMB experiments.
Existing dynamical bounds from stellar streams and wide binaries are weaker at these mass scales because minihalos are baryon-free and diffuse. Exoplanet systems add leverage through their extreme binding energies and the statistical power of future catalogs from Roman, Euclid, and Gaia DR4, which are projected to discover hundreds of ultra-wide giants.
The approach links inflation model-building directly to observable exoplanet architectures, a cross-scale connection rarely quantified. A key limitation is the assumed minihalo density profile and Galactic number density; tighter priors from N-body simulations would strengthen the mapping from perturbation parameters to exoplanet statistics.
Upcoming wide-field microlensing and astrometric surveys can falsify or tighten the derived exclusion regions within five years by increasing the sample of intact ultra-wide systems.
Lavalle: Roman Space Telescope's first two years of microlensing data will exclude A>5e-4 at k_inj>3e5 Mpc^-1 if fewer than 3% of detected wide-orbit giants show anomalous eccentricities.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2606.14827)
- [2]Supporting Source(https://arxiv.org/abs/2006.09387)