Super-earths and mini-neptunes follow different orbital period-eccentricity relations
arXiv:2606.18410 · doi:10.1126/science.adu3916
Abstract
Many exoplanets have been observed with radius sizes between that of Earth and that of Neptune and are thus classified into two groups: super-earths (SEs) and mini-neptunes (MNs). There are no SEs and MNs in the Solar System, and the mechanisms responsible for their formation and evolution are debated. We investigate the relationships between the orbital period and eccentricity of SEs and MNs using both ensemble analyses and individual measurements. We found that MNs follow an anti-correlation between orbital period and eccentricity, but SEs follow a different relation, possibly in the opposite direction. These trends imply that MNs and SEs are dynamically distinct populations. We suggest that SEs have been more strongly influenced by violent processes such as gravitational scattering and giant impacts, whereas MNs predominantly experienced quiescent secular evolution.
This is the author's version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science on June 11th, 2026
References in corpus (25)
- The Gaia mission
- Gaia Data Release 3: Summary of the content and survey properties
- Dynamical Outcomes of Planet-Planet Scattering
- Growth Model Interpretation of Planet Size Distribution
- Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
- Tidal Evolution of Close-in Extra-Solar Planets
- Density, not radius, separates rocky and water-rich small planets orbiting M dwarf stars
- Revisited Mass-Radius relations for exoplanets below 120 Earth masses
- Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
- Atmospheric Mass Loss During Planet Formation: The Importance of Planetesimal Impacts
- The Gaia-Kepler Stellar Properties Catalog. II. Planet Radius Demographics as a Function of Stellar Mass and Age
- Habitable Climates: The Influence of Eccentricity
- Forward and Inverse Modeling of the Emission and Transmission Spectrum of GJ 436b: Investigating Metal Enrichment, Tidal Heating, and Clouds
- AMD-stability and the classification of planetary systems
- Characterizing the Orbital Eccentricities of Transiting Extrasolar Planets with Photometric Observations
- A Super-Solar Metallicity For Stars With Hot Rocky Exoplanets
- The Exoplanet Orbital Eccentricity - Multiplicity Relation and the Solar System
- Planetary Collisions outside the Solar System: Time Domain Characterization of Extreme Debris Disks
- CKS VIII: Eccentricities of Kepler Planets and Tentative Evidence of a High Metallicity Preference for Small Eccentric Planets
- Why do warm Neptunes present nonzero eccentricity?
- Mapping the exo-Neptunian landscape. A ridge between the desert and savanna
- Formation of Close-in Super-Earths by Giant Impacts: Effects of Initial Eccentricities and Inclinations of Protoplanets
- Proximity of exoplanets to first-order mean-motion resonances
- CKS IX: Revisiting the Minimum-Mass Extrasolar Nebula with Precise Stellar Parameters
- Planetary Orbit Eccentricity Trends (POET). I. The Eccentricity-Metallicity Trend for Small Planets Revealed by the LAMOST-Gaia-Kepler Sample