Studies of Super-Earth and Terrestrial Planet Atmospheres with JWST Eliza Kempton (Formerly: Miller-Ricci) Assistant Professor of Physics Grinnell College + University of Maryland, College Park Image Credit: Zach Berta
Atmospheric characterization provides a window into the diverse bulk properties of low-mass exoplanets Hadden & Lithwick, AJ, 2017
Secondary Atmospheres Imagine the Possibilities... PLANET FORMATION EQUILIBRIUM CHEMISTRY OUTGASSING OF VOLATILES PHOTOCHEMISTRY MASS LOSS COOLING HISTORY CLUSTER ENVIRONMENT PARENT STAR SPECTRUM PLANET LOCATION PLANET TEMPERATURE PLANET SURFACE GRAVITY PLATE TECTONICS PLANET MAGNETIC FIELD
Secondary Atmospheres Imagine the Possibilities... PLANET FORMATION EQUILIBRIUM CHEMISTRY OUTGASSING OF VOLATILES PHOTOCHEMISTRY MASS LOSS COOLING HISTORY CLUSTER ENVIRONMENT PARENT STAR SPECTRUM PLANET LOCATION PLANET TEMPERATURE PLANET SURFACE GRAVITY PLATE TECTONICS PLANET MAGNETIC FIELD
Observational Results: GJ 1214b GJ 1214 system to scale GJ 1214b 1.4% transit depth GJ 1214b H 2 Planet is too big to be explained without the presence of a significant atmosphere! Lissauer et al., Nature, 2011 (modified c/o E. Lopez)
Observational Results: GJ 1214b Solar 30 x Solar 50 x Solar H 2O H2O - CO2 CO2 Transit Depth (%) No atmosphere Wavelength (microns) Miller-Ricci (Kempton) & Fortney, ApJL 2010 1. Mini-Neptune Scenario: Rock / ice interior + hydrogen-dominated atmosphere (mostly H2+ trace H2O, CH4, etc.) 2. Water World Scenario: Mostly H2O - ice/fluid interior + steam atmosphere (i.e. Rogers & Seager, ApJ, 2010 + Nettelmann et al. 2011)
Observational Results: GJ 1214b Featureless spectrum aerosols! Kreidberg et al., Nature 2014 Berta et al., ApJ 2012
Observational Results: HD 97658b M pl = 7.9 M R pl = 2.3 R ρ = 3.4 g/cm P = 9.49 days T eq 700 K 3 Inconsistent w/ H2-rich cloud-free composition Knutson et al., ApJ, 2014
Observational Results: 55 Cnc e Spitzer phase curve Spitzer secondary eclipse Demory et al., Nature, 2016 Demory et al., ApJL, 2012 variability in dayside emission? Demory et al., MNRAS, 2016
Observational Results: TRAPPIST-1 Wang et al., ApJ, submitted DeWit et al., Nature, 2016
TESS yields: 100s of potential targets for JWST Sullivan et al., ApJ, 2015
Mass measurements are a necessity! Volatile-rich water world, water-rich atmosphere Rocky planet, outgassed H2-rich atmosphere R pl = 1.5 R T obs = 200 hr M4.5 host star (T = 3,000 K, R = 0.2 R ) J = 8 Natasha Batalha, Kempton, & Mbarek, ApJL, 2017
Wish List for Super-Earth and Terrestrial Planet Science w/ JWST
Identify the division between terrestrial planets and mini-neptunes, as it relates to planet formation and atmospheric evolution (i.e. mass loss) Evaporation valley Lack of Neptune-size planets 0-10 d 10-20 20-40 40-100 Lopez, Fortney, & Miller, ApJ, 2012 Owen & Wu, ApJ, submitted
Gain a deeper understanding of aerosols in the lowmass planet regime H:O = 1.39 C:O = 0.18 H:O = 2.77 C:O = 0.66 Cloud composition in outgassed super-earth atmospheres H:O = 0.21 C:O = 0.41 H:O = 0.45 C:O = 0.87 Carbon-rich GJ 1214b analogs may host graphite clouds. Mbarek & Kempton, ApJ, 2016
Gain a deeper understanding of aerosols in the lowmass planet regime Carbon-Bearing Species CH4 photolysis formation of complex hydrocarbons hydrocarbon haze + sulfur hazes? (e.g. Zahnle et al. (2016), Gao et al. (2017)) Miller-Ricci Kempton, Zahnle, Fortney, ApJ 2012 - - - - Equilibrium Abundances Photochemical Abundances
Measure water abundances and tie this to planet formation and the frequency of water-worlds Water-rich super-earths Raymond et al., Icarus, 2006
Classify new types of exotic low-mass planets (i.e. lava worlds) Diversity of outgassed atmospheres Schaefer & Fegley, Icarus, 2009 Elkins-Tanton & Seager, ApJ, 2008
Classify new types of exotic low-mass planets (i.e. lava worlds) He-dominated atmospheres from diffusion-limited escape Hu et al., ApJ, 2015 Composition of lava-planet atmospheres Ito et al., ApJ, 2015
Earth-Sun system Biosignatures?? TRAPPIST planets 1 ppm 0 ppm O3 Kaltenegger et al., IJAsBio, 2012 Proxima Cen b 60 days co-added observations CH4 O3 JWST NIRSpec + MIRI JWST MIRI Kreidberg & Loeb., ApJL, 2016 Barstow et al., MNRAS, 2016
Wish List for Super-Earth and Terrestrial Planet Science w/ JWST Identify the division between terrestrial planets and mini-neptunes, as it relates to planet formation and atmospheric evolution (i.e. mass loss) Gain a deeper understanding of aerosols in the lowmass planet regime Measure water abundances and tie this to planet formation and the frequency of water-worlds Classify new types of exotic low-mass planets (i.e. lava worlds) Biosignatures??