Speaker:    Dr. Kielan Hoch, Giacconi Fellow, Space Telescope Science Institute, Towson Universityu Alumnus

Abstract:     The James Webb Space Telescope (JWST) has opened the door to spectroscopy of directly imaged exoplanets beyond 3 microns, offering a new landscape for measuring their fundamental and atmospheric properties. Directly imaged planets are in a stage of early evolution and are undergoing atmospheric processes that are critical for understanding planetary atmospheric evolution and formation. These planets, with masses of ~2-14MJup and temperatures of ~500-2000 K, remain a mystery for planet formation models—core accretion and gravitational instability. Observations that probe elemental abundances in their atmospheres can shed light on their formation. Here I present JWST Cycle 1 programs that have pioneered the use of JWST’s NIRSpec IFU to obtain spectra of substellar companions close to sunlike stars.  For HD 19467 B, NIRSpec spectra show detections of CO, CO2, CH4, and H2O. We forward model the R~2,700 spectra using custom PHOENIX atmospheric model grids to constrain the abundances of these molecules, the C/O ratio, and non-equilibrium chemistry. These results highlight a need for revisions of disequilibrium chemistry models to vary the CO2 abundance with the new spectral information provided by NIRSpec. For the multi planet system YSES-1, my team obtained one of the most comprehensive datasets of a multi-planet system with spectral coverage from 1-12 microns using NIRSpec and MIRI. The spectra allow direct spectral comparison of sibling planets in unprecedented detail with spectra that show the first direct detection of silicate clouds in an exoplanet YSES-1 c and the detection of a circumplanetary disk around YSES-1 b with olivine emission that could be caused by formation of larger bodies such as moons.