Spacing of Kepler Planets: Sculpting by Dynamical Instability
156 citations recorded by the source corpus.
We study the orbital architecture of multi-planet systems detected by the Kepler transit mission using N-body simulations, focusing on the orbital spacing between adjacent planets in systems showing four or more transiting planets. We find that the observed spacings are tightly clustered around 12 mutual Hill radii, when transit geometry and sensitivity limits are accounted for. In comparison, dynamical integrations reveal that the minimum spacing required for systems of similar masses to survive dynamical instability for as long as a billion years is, ~10 if all orbits are circular and coplanar, and ~12 if planetary orbits have eccentricities ~0.02 (a value suggested by studies of planet transit-time-variations). This apparent coincidence, between the observed spacing and the theoretical stability threshold, leads us to propose that typical planetary systems were formed with even tighter spacing, but most, except for the widest ones, have undergone dynamical instability, and are pared down to a more anemic version of their former selves, with fewer planets and larger spacings. So while the high multiple systems (five or more transiting planets) are primordial systems that remain stable, the single or double planetary systems, abundantly discovered by the Kepler mission, may be the descendants of more closely packed high multiple systems. If this hypothesis is correct, we infer that the formation environment of Kepler systems should be different from that of the terrestrial planets.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/cd389139a7b404e3850bd15c059a0ce92868e1da
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In Astronomy and Astrophysics
Citations in the corpus
- The Evaporation Valley in the Kepler Planets (2017, background): “Orbital instabilities have been suggested to be common among Kepler systems (e.g., Pu & Wu 2015).”
- BREEDING SUPER-EARTHS AND BIRTHING SUPER-PUFFS IN TRANSITIONAL DISKS (2015, background): “…doubling, protocores are so widely spaced (the number of Hill-radius spacings k > 5) that the particle-in-a-box approximation (e.g., Safronov 1972, Goldreich et al. 2004) likely fails (Ford & Chiang 2007). k ' 14±3.4 (taken from the “intrinsic” k distribution of Pu & Wu 2015; see their Figure 7).”
- Breaking the chains: hot super-Earth systems from migration and disruption of compact resonant chains (2017, background): “(see also Pu & Wu 2015, who proposed that the Kepler systems were sculpted by instabilities but without starting from resonant chains.)”
- The Exoplanet Population Observation Simulator. I. The Inner Edges of Planetary Systems (2018, background): “These mechanisms include dynamical instabilities within systems (Pu & Wu 2015; Volk & Gladman 2015), external perturbations from giant planets or stars (Johansen et al. 2012; Hansen 2017; Izidoro et al. 2017; Lai & Pu 2017; Cai et al. 2018) and host star misalignment (Spalding & Batygin 2016).”
- The California-Kepler Survey. V. Peas in a Pod: Planets in a Kepler Multi-planet System Are Similar in Size and Regularly Spaced (2017, background): “Fang & Margot (2012), Pu & Wu (2015), and Dawson et al. (2016) have also estimated that the Kepler planets have a typical spacing of about 20 mutual Hill radii, but our updated planet radii and stellar masses allow more precise empirical estimates.”
- About 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of Their Intrinsic Architecture (2018, background): “From Pu & Wu (2015) the critical number of mutual Hill radii that a system can have is Kcrit = 2 + k + 27/5 × σi,k[3/(2q)]1/3, with q = Mp/M?.”
- Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1 (2017, unknown): “Using the masses and semi-major axes in Table 1, we calculated the separations between all adjacent pairs of planets in units of their mutual Hill spheres 58 .”