Exoplanet Classification and Yield Estimates for Direct Imaging Missions

2018/02/26 by Ravi kumar Kopparapu, Ravi Kumar Kopparapu, Eric Hebrard +8 · 85 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Circumstellar habitable zone #Direct imaging #Exoplanet #Light curve #Planet #Planetary habitability #Planetary system #Stellar, planetary, and galactic studies #Terrestrial planet #astro-ph.EP

paper · pdf · doi:10.3847/1538-4357/aab205

published in The Astrophysical Journal 856(2), 122 (IOP Publishing) · Accepted to Astrophysical Journal. 30 pages, 4 tables. Online tool for classification boundaries can be found at: http://www3.geosc.psu.edu/~ruk15/planets/

arxiv created 2018/02/26 · openalex created_date 2018/03/06 · openalex publication_date 2018/03/30 · arxiv updated 2018/04/11 · openalex updated_date 2026/08/06

Abstract

Abstract Future NASA concept missions that are currently under study, like the Habitable Exoplanet Imaging Mission (HabEx) and the Large Ultra-violet Optical Infra Red Surveyor, could discover a large diversity of exoplanets. We propose here a classification scheme that distinguishes exoplanets into different categories based on their size and incident stellar flux, for the purpose of providing the expected number of exoplanets observed (yield) with direct imaging missions. The boundaries of this classification can be computed using the known chemical behavior of gases and condensates at different pressures and temperatures in a planetary atmosphere. In this study, we initially focus on condensation curves for sphalerite ZnS, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:mi mathvariant="normal">O</mml:mi> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>CO</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math> , and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>CH</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:math> . The order in which these species condense in a planetary atmosphere define the boundaries between different classes of planets. Broadly, the planets are divided into rocky planets (0.5–1.0 R ⊕ ), super-Earths (1.0–1.75 R ⊕ ), sub-Neptunes (1.75–3.5 R ⊕ ), sub-Jovians (3.5–6.0 R ⊕ ), and Jovians (6–14.3 R ⊕ ) based on their planet sizes, and “hot,” “warm,” and “cold” based on the incident stellar flux. We then calculate planet occurrence rates within these boundaries for different kinds of exoplanets, η planet , using the community coordinated results of NASA’s Exoplanet Program Analysis Group’s Science Analysis Group-13 (SAG-13). These occurrence rate estimates are in turn used to estimate the expected exoplanet yields for direct imaging missions of different telescope diameters.

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