Date: Monday 02-Dec-2024
Time: 11:15 am - 12:15 pm
Location: ATL 1250 and Zoom (contact host Matt Nixon for link)
Speaker: Mans Holmberg (Space Telescope Science Institute)
Title: Atmospheric characterisation of temperate sub-Neptunes in the JWST era
Abstract: Recent JWST detections of carbon-bearing species in the habitable-zone sub-Neptune K2-18 b have opened a new era in the study of low-mass exoplanets. With radii between 1-4 times that of Earth, sub-Neptunes dominate the known exoplanet population and exhibit a diverse range of possible interior compositions not witnessed in the solar system, including mini-Neptunes, gas dwarfs, and water worlds. Detailed atmospheric characterisation is the key to distinguishing between these different scenarios. In this talk, I will present recent JWST observations of TOI-270 d, a candidate Hycean world, using NIRSpec G395H (2.8-5.2 μm), combined with previous observations with HST WFC3 (1.1-1.6 μm). The transmission spectrum reveals strong signatures of CH4 and CO2, some evidence for CS2 and H2O, and no detection of NH3. The retrieved atmospheric composition supports the interpretation of TOI-270 d having a shallow H2-rich atmosphere over a planet-wide ocean — rather than a deep H2-rich atmosphere. Additionally, I will present an integrated interior-atmosphere modelling framework to investigate the feasibility of a gas-dwarf scenario for temperate sub-Neptune planets, using K2-18 b as a case study.
If you have any questions, contact the PALS hosts: Benjamin Sharkey (small bodies) and Matt Nixon (exoplanets).
SPECIAL ACCOMMODATIONS:Special accommodations for individuals with disabilities can be made by calling (301) 405-3001. It would be appreciated if we are notified at least one week in advance.
ATL 1250 is a flat, carpeted conference room that can accommodate approximately 20-30 people at large tables. The closest wheelchair accessible entry to this room in the Atlantic building is the white stone entrance at 224 Stadium Drive.
