Nature vs. nurture: a Bayesian framework for assessing apparent correlations between planetary orbital properties and stellar ages

Abstract

Many exoplanets have orbital characteristics quite different from those seen in our own solar system, including planets locked in orbital resonances and planets on orbits that are elliptical or highly inclined from their host star's spin axis. It is debated whether the wide variety in system architecture is primarily due to differences in formation conditions (nature) or due to evolution over time (nurture). Identifying trends between planetary and stellar properties, including stellar age, can help distinguish between these competing theories and offer insights as to how planets form and evolve. However, it can be challenging to determine whether observed trends between planetary properties and stellar age are driven by the age of the system -- pointing to evolution over time being an important factor -- or other parameters to which the age may be related, such as stellar mass or stellar temperature. The situation is complicated further by the possibilities of selection biases, small number statistics, uncertainties in stellar age, and orbital evolution timescales that are typically much shorter than the range of observed ages. Here we develop a Bayesian statistical framework to assess the robustness of such observed correlations and to determine whether they are indeed due to evolutionary processes, are more likely to reflect different formation scenarios, or are merely coincidental. We apply this framework to reported trends between stellar age and 2:1 orbital resonances, spin-orbit misalignments, and hot Jupiters' orbital eccentricities. We find strong support for the nurture hypothesis only in the final case.

Accepted by the Astronomical Journal

References in corpus (8)

• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Three regimes of extrasolar planets inferred from host star metallicities
• The Mass of KOI-94d and a Relation for Planet Radius, Mass, and Incident Flux
• Long Term Evolution of Close Planets Including the Effects of Secular Interactions
• From mean-motion resonances to scattered planets: Producing the Solar System, eccentric exoplanets and Late Heavy Bombardments
• The inclination of the planetary system relative to the solar equator may be explained by the presence of Planet 9
• Q in Other Solar Systems
• Mapping out the time-evolution of exoplanet processes

Cited by in corpus (6)

• Stellar obliquities in exoplanetary systems
• A Tendency Toward Alignment in Single-Star Warm Jupiter Systems
• A framework for the architecture of exoplanetary systems. I. Four classes of planetary system architecture
• Moderately misaligned orbit of the warm sub-Saturn HD 332231 b
• Nature vs. Nurture: Investigating the Effects of Measurement Uncertainties in the Assessment of Potential Trends Between Planetary and Stellar Properties
• Evidence for the Late Arrival of Hot Jupiters in Systems with High Host-star Obliquities