Rocky histories: The effect of high excitations on the formation of rocky planets

Abstract

Rocky planets both in and outside of our solar system are observed to have a range of core-mass fractions (CMFs). Imperfect collisions can preferentially strip mantle material from a planet, changing its CMF, and are therefore thought to be the most likely cause of this observed CMF variation. However, previous work that implements these collisions into N-body simulations of planet formation has struggled to reliably form high CMF super-Earths. In this work, we specify our initial conditions and simulation parameters to maximize the prevalence of high-energy, CMF-changing collisions in order to form planets with highly diverse CMFs. High-energy collisions have a large $v_{imp}/v_{esc}$ ratio, so we maximize this ratio by starting simulations with high-eccentricity and inclination disks to increase the difference in their orbital velocities, maximizing $v_{imp}$. Additionally, we minimize $v_{esc}$ by starting with small embryos. The final planets undergo more high-energy, debris-producing collisions, and experience significant CMF change over their formation. However, we find that a number of processes work together to average out the CMF of a planet over time, therefore we do not consistently form high-CMF, high mass planets. We do form high-CMF planets below 0.5 $M_{\oplus }$. Additionally, we find in these highly eccentric environments, loss of debris mass due to collisional grinding has a significant effect on final planet masses and CMFs, resulting in smaller planets and a higher average planet CMF. This work highlights the importance of improving measurements of high-density planets to better constrain their CMFs.

arXiv comment19 pages. This paper has been accepted to ApJ

References in corpus (39)

• Astropy: A Community Python Package for Astronomy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• A low mass for Mars from Jupiter's early gas-driven migration
• The false positive rate of Kepler and the occurrence of planets
• Most 1.6 Earth-Radius Planets are not Rocky
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
• False positive probabilties for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
• Collisions between Gravity-Dominated Bodies: 2. The Diversity of Impact Outcomes during the End Stage of Planet Formation
• Collisions Between Gravity-Dominated Bodies: 1. Outcome Regimes and Scaling Laws
• A New Family of Planets ? "Ocean Planets"
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• A Framework for Quantifying the Degeneracies of Exoplanet Interior Compositions
• Formation of the Terrestrial Planets from a Narrow Annulus
• The orbital eccentricity of small planet systems
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• Radius and Structure models for the First Super-Earth Planet
• Kepler Planet Masses and Eccentricities from TTV Analysis
• The Super Earth-Cold Jupiter Relations
• Merging Criteria for Giant Impacts of Protoplanets
• Differentiation of Vesta: Implications for a shallow magma ocean
• Secure TTV Mass Measurements: Ten Kepler Exoplanets between 3 and 8 Earth Masses with Diverse Densities and Incident Fluxes
• Debris from terrestrial planet formation: the Moon-forming collision
• Collisional Stripping and Disruption of Super-Earths
• Chemical Fingerprints of Formation in Rocky Super-Earths' Data
• The Fragility of the Terrestrial Planets During a Giant Planet Instability
• GJ 367b: A dense ultra-short period sub-Earth planet transiting a nearby red dwarf star
• CKS VIII: Eccentricities of Kepler Planets and Tentative Evidence of a High Metallicity Preference for Small Eccentric Planets
• Chemical Diversity of Super-Earths As a Consequence of Formation
• Nucleation and growth of iron pebbles explains the formation of iron-rich planets akin to Mercury
• Rocklines as Cradles for Refractory Solids in the Protosolar Nebula
• Simulating the M-R Relation from APF follow up of TESS targets: Survey design and strategies for overcoming mass biases
• Characterization of the K2-38 planetary system. Unraveling one of the densest planets known to date
• Formation of compact systems of super-Earths via dynamical instabilities and giant impacts
• Host-star and exoplanet compositions: a pilot study usinga wide binary with a polluted white dwarf
• Evidence for differentiation of the most primitive small bodies
• Forming Iron-rich Planets with Giant Impacts
• The "Breaking The Chains" migration model for super-Earths formation: the effect of collisional fragmentation
• The Effect of Inefficient Accretion on Planetary Differentiation

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