Cool Worlds Podcast #28 Néstor Espinoza - JWST, Exoplanet Atmospheres, Molecule Detection
Dec 5, 2025
Néstor Espinoza, an associate astronomer and mission scientist at the Space Telescope Science Institute, dives into the fascinating world of exoplanet atmospheres. He shares insights on various techniques like transmission spectroscopy and secondary eclipses for probing atmospheric composition. Néstor contrasts findings from JWST with earlier Hubble observations, highlighting unexpected discoveries such as CO2. He discusses the challenges of detecting thermal signatures and how JWST's instruments help unravel the mysteries of distant worlds, all while reflecting on the societal value of exoplanet science.
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Transmission Signals Favor Small Stars
- Transmission spectroscopy measures the apparent planet size versus wavelength as the atmosphere absorbs starlight during transit.
- Signals scale steeply with host-star radius, so small stars dramatically boost detectability for rocky planets.
Wider Wavelengths Reveal New Chemistry
- Hubble found many water features but lacked wavelength coverage to detect molecules like CO2.
- James Webb expands coverage to ~0.6–28 microns, unlocking new molecular fingerprints and surprises.
WASP-39b Surprise: Photochemical SO2
- Early JWST observations of WASP-39b revealed an unexpected spectral wiggle later identified as photochemical sulfur dioxide.
- That detection highlighted JWST's ability to find unmodeled chemical products beyond predictions.