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SUMMARY:Exploring the atmospheric structure of water-rich sub-Neptunes - H
 amish Innes (Freie Universität - Berlin)
DTSTART:20240521T120000Z
DTEND:20240521T130000Z
UID:TALK215836@talks.cam.ac.uk
CONTACT:Dr Dolev Bashi
DESCRIPTION:Population studies and planetary formation models predict a cl
 ass of water-rich sub-Neptunes consisting of a rocky core overlain by a wa
 ter-rich envelope. Characterising such planets is difficult since differin
 g interior structures often lead to degenerate mass and radii. Recent JWST
  observations aim to break some of these degeneracies by retrieving atmosp
 heric composition\, however accurate atmospheric models are required to in
 terpret data. For example\, separate analyses of the JWST transmission spe
 ctrum of water world candidate TOI-270 d predicted different interior stru
 ctures - a “Hycean world” scenario with a liquid water surface and a 
 “miscible sub-Neptune” where the water in the envelope is in a supercr
 itical state. To distinguish these scenarios\, I have developed a radiativ
 e-convective model specifically designed to model water-rich sub-Neptunes.
  In particular\, the model accounts for the inhibition of convection due t
 o mean molecular weight gradients induced by the condensation of water vap
 our in a less dense background gas. I show that this can warm a liquid wat
 er surface significantly\, moving the traditional habitable zone of the pl
 anet outwards and disfavouring the presence of water oceans for sub-Neptun
 es with Earth-like instellations. Following on from this\, I will explore 
 the possible equilibrium states of a sub-Neptune with a supercritical wate
 r envelope. Lastly\, I will discuss attempts to decipher whether sub-Neptu
 nes have surfaces using atmospheric chemistry and the implications this ha
 s on interpreting present and future observations. 
LOCATION:Hoyle Committee Room + ONLINE - Details to be sent by email
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