The Prevalence of Resonance Among Young, Closein Planets
Abstract
Multiple planets undergoing disk migration may be captured into a chain of meanmotion resonances with the innermost planet parked near the disk's inner edge. Subsequent dynamical evolution may disrupt these resonances, leading to the nonresonant configurations typically observed among {\it Kepler} planets that are Gyrs old. In this scenario, resonant configurations are expected to be more common in younger systems. This prediction can now be tested, thanks to recent discoveries of young planets, particularly those in stellar clusters, by NASA's {\it TESS} mission. We divided the known planetary systems into three age groups: young ($<$100Myrold), adolescent (0.11Gyrold), and mature ($>1$Gyrold). The fraction of neighboring planet pairs having period ratios within a few percent of a firstorder commensurability (e.g.~4:3, 3:2, or 2:1) is 70$\pm$15\% for young pairs, 24$\pm$8\% for adolescent pairs, and 15$\pm$2\% for mature pairs. The fraction of systems with at least one nearly commensurable pair (either first or secondorder) is 86$\pm13$\% among young systems, 38$\pm12$\% for adolescent systems, and 23$\pm3$\% for mature systems. Firstorder commensurabilities prevail across all age groups, with an admixture of secondorder commensurabilities. Commensurabilities are more common in systems with high planet multiplicity and low mutual inclinations. Observed period ratios often deviate from perfect commensurability by $\sim$1\% even among young planets, too large to be explained by resonant repulsion with equilibrium eccentricity tides. We also find that superEarths in the radius gap ($1.51.9R_\oplus$) are less likely to be nearresonant (11.9$\pm2.0\%$) compared to Earthsized planets ($R_p<1R_\oplus$; 25.3$\pm4.4\%$) or miniNeptunes ($1.9R_\oplus \leq R_p<2.5R_\oplus$; 14.4$\pm1.8\%$).
 Publication:

arXiv eprints
 Pub Date:
 June 2024
 DOI:
 10.48550/arXiv.2406.06885
 arXiv:
 arXiv:2406.06885
 Bibcode:
 2024arXiv240606885D
 Keywords:

 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 17 pages, 9 figures, accepted to AAS