## The Project

Which molecules are present in the atmosphere of exoplanets? What are their mass, radius and age? Do they have clouds, convection (atmospheric turbulence), or a circulation induced by irradiation? These questions are fundamental in exoplanetology to better understand planet formation and exoplanet habitability with JWST.

« James Webb Space Telescope will tell us more about the atmospheres of extrasolar planets, and perhaps even find the building blocks of life elsewhere in the universe. »

This project aims at characterizing the impact of diabatic convection (i.e. with source terms) in the atmosphere of stars, brown dwarfs, and exoplanets and its interaction with the circulation in the case of irradiated planets. By developing innovative numerical models, we will characterize the effect of the diabatic instability induced by chemical transitions (e.g. CO/CH$$_4$$) with radiative transfer and its interaction with the global circulation in the atmosphere. We will then predict and interpret the mass, radius, and chemical composition of exoplanets that will be observed with future missions such as the James Webb Space Telescope (JWST).

## What is diabatic convection?

Thermo-compositional diabatic convection is a new concept proposed in Tremblin et al. 2019 that encompass several well known convective systems in which source terms are important (thermohaline convection in Earth oceans, fingering convection in stars, moist convection in Earth atmosphere, steam/liquid water convection in cooling systems, and CO/CH$$_4$$ radiative convection in the atmosphere of brown dwarfs and extrasolar giant exoplanets).

## News

### A general theory for adiabatic and diabatic thermo-compositional convection

By generalizing the theory of convection to any type of thermal and compositional source terms (diabatic processes), we show that thermohaline convection in Earth oceans, fingering convection in stellar atmospheres, and moist convection in Earth atmosphere are deriving from the same general diabatic convective instability. We show also that ”radiative convection” triggered by CO/CH4 transition …

### Pre-ERC result: Hubble Detects Exoplanet with Glowing Water Atmosphere

Image © NASA, ESA, and A. Feild (STSci) Exeter University Press release: Scientists have found unmistakable evidence for a stratosphere on an enormous planet outside our solar system, with an atmosphere hot enough to boil iron. An international team of researchers, led by the University of Exeter, made the new discovery by observing glowing water molecules in …

### Pre-ERC result: HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance

A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted in this Science paper, …

## Contact and Team

Contact

• Pascal Tremblin: Personal Website
• Phone: +33 1 69 08 59 67
• Email: pascal.tremblin[at]cea.fr

Team

• Felix Sainsbury-Martinez, Astrophysicist (Postdoc)
• Simon Daley-Yates, Astrophysicist (Postdoc)
• Solène Bulteau, Mathematician (Postdoc)
• Hélène Bloch, PhD student
• Mathilde Poveda, PhD student