Abstract
Exploring the Impact of JWST Measurements on Characterizing Planetary Atmospheres
Joel C. Schwartz (McGill University)
Nicolas B. Cowan (McGill University)
Energy balance in planetary atmospheres describes the global absorption and transport of heat, key components for the climate and habitability of terrestrial worlds. With Spitzer and Hubble Space Telescope measurements, it is possible to constrain the day (Td) and night temperatures (Tn) of a Hot Jupiter to within ~2% and ~10%, respectively. These translate to ~10% uncertainties on Bond albedo (AB) and heat transport efficiency (ε). However, the best constraints require observations, including several phase curves, in ~10 distinct infrared wavebands, only available for select bright targets (e.g. HD 189733b). The James Webb Space Telescope (JWST) presents an opportunity to characterize at least an order of magnitude more short-period giants—and even some terrestrial planets. We explore what the precision of JWST spectroscopy and photometry can mean for describing atmospheres of transiting planets. For those with Td > 500 K, NIRSpec will allow one to model the peak of the planet's thermal SED more finely than with Hubble or Spitzer. Coverage by MIRI on the Rayleigh Jeans tail will also help one distinguish reflected light from thermal emission in the near-infrared. We show that precision of order 10-4 in just these measurements constrain Td and Tn of Hot Jupiters to within ~1%, giving better estimates of AB and ε than the best cases today. We further demonstrate that ~103 transiting planets with Rp ≤ 2R⊕ are warm enough to radiate in the JWST bands. For these and other worlds, we investigate the optimal instrument modes on JWST to observe different features in full-orbit light curves. In essence, energy balance on Hot Jupiters today is the prelude for discoveries on temperate terrestrial planets tomorrow.
Mode of presentation: poster