Benjamin Charnay
LESIA, Observatoire de Paris, France

Abstract
Kepler transit surveys revealed that sub-Neptunes (planets with radii between 1.8 and 3 Earth) are very common, in our galaxy. These planets could be composed of a rocky core surrounded by a thick H2-dominated atmosphere or they could be waterworlds with a steam atmosphere. The atmospheric characterization of sub-Neptunes is a key to understand the nature of these objects and the transition between rocky planets and gaseous planets. Transit observations of the temperate sub-Neptune K2-18b revealed an absorption feature at 1.4 micron which was interpreted as water vapour, placing K2-18b as one of the best sub-Neptunes for atmospheric characterization. During this talk, I will present results from 1D atmospheric modelling of K2-18b which suggests that the observed feature is more likely due to methane. I will also discuss atmospheric dynamics and cloud formation based on 3D modelling. I will finish with perspectives for atmospheric characterization of temperate sub-Neptunes with the next generation of telescopes (JWST, ELT, ARIEL).

2020 December 04, 13:30

IA
Online broadcast (Zoom)