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JWST Thermal Emission Spectroscopy of the Super-Earth 55 Cnc e

Presentation #410.03 in the session Exoplanet Atmospheres: Terrestrial Planets (Oral Presentation)

Published onOct 23, 2023
JWST Thermal Emission Spectroscopy of the Super-Earth 55 Cnc e

JWST enables the measurements of the thermal emission spectra of small exoplanets to characterize their atmospheres and surfaces. Such measurements open up a new way to test models of atmospheric evolution and retention. We present the first JWST thermal emission spectrum of a potentially rocky exoplanet, the planet 55 Cnc e, covering the wavelength range from 4 to 12 microns through two transit observations using the NIRCam/F444W and MIRI/LRS modes. Prior observations with Spitzer photometry showed that the planet must have either a thick volatile-rich atmosphere, or a molten lava surface shrouded by a mineral atmosphere while rotating at an asynchronous rate. Potential scenarios for the volatile-rich atmosphere include an O2 atmosphere formed by the loss of hydrogen from a primordial water world, or an N2 atmosphere with varied abundances of CO2, CO, and HCN resulting from the accretion of rocky materials. The mineral atmosphere would otherwise be dominated by Na, O, K, Fe, and SiO. The JWST observations have the sensitivity to distinguish the thick atmosphere scenarios versus the mineral atmosphere scenario via spectral features of H2O, CO, CO2, and SiO, providing one of the first direct detections of a non-H2-dominated atmosphere on an exoplanet. We will also discuss the challenges and mitigations for observing very bright stars such as 55 Cnc using JWST.

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