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Exploring Compositional Predictions for Super-Earth and Sub-Neptune Planets

Presentation #301.07 in the session Exoplanets Formation of Planets and Protoplanetary Disks — iPoster Session.

Published onJun 29, 2022
Exploring Compositional Predictions for Super-Earth and Sub-Neptune Planets

From the Kepler mission, we learned that small terrestrial planets 一 categorized as super-Earths (~1-1.6 R) and sub-Neptunes (~2-3 R) 一 are more abundant than large gas planets. Yet, our own solar system lacks planets of such size. Thus, it is of interest to study the similarities and differences in their formation in order to learn about the conditions that resulted in 1-3 R planets. To learn more about the planets’ characteristics, we measure the planets’ mass and radii. Those measurements then enable us to estimate the planets’ bulk density, which in-turn allows the estimation of the planet composition. In this study, we focus on two key samples 一 twenty-two planets in total 一 from Teske et al. (2021) and from JWST Cycle 1 GO Program 2512. These samples are important because they have or will have homogenous masses obtained from an observation program designed to minimize bias, and some planets will have atmospheric composition constraints from the JWST Cycle 1 observations. We utilize two publicly available codes 一 MDNexoplanets and ExoPlex 一 to estimate the interior composition of these planets. MDNexoplanets generates predictions of the planets’ gas, ice, mantle, and core densities. ExoPlex can return predictions of the planets’ mineral (Ca/Mg, Si/Mg, Al/Mg, and Fe/Mg) compositions. Studying the results of these models, we explore what factors might account for the density differences between the exoplanets in this dataset. From the codes’ predictions, we investigate trends between the planets’ density and temperature and also compare the results of the two codes by dividing the results into qualitative categories, e.g., planets with non-zero gas fraction probabilities (MDNexoplanets) and planets that cannot be matched with a rock-only model (ExoPlex). Further refinement in mass measurements and the upcoming atmospheric observations will allow us to test our predictions and validate any trends we find. This work contributes to a broader census of small planet compositions, which is important for understanding the uniqueness of our solar system’s characteristics and Earth’s habitability. Looking at the variation between the planets’ material composition will lead to a better understanding of the materials present during planetary formation and evolution.

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