Continua & Observability for Measurements of Telluric Exoplanets (M/F)

Job Description

Thesis Subject

During the next decade, a new generation of instruments (e.g. ANDES@ELT in 2032, PCS@ELT in 2040+) will enable high-resolution spectra to obtain reflected light from the atmospheres of terrestrial exoplanets in the visible and near-infrared regions. The creation of synthetic observables is essential for 1) instrumental preparation and data analysis for these future instruments, and 2) predicting the potential observability of these planets to refine the definition of scientific cases. In order to create high-quality observables, it is essential to have a robust radiative transfer model based on precise opacity data. However, absorption continua (and their temperature dependence) are key to the creation of opacity data, and they have yet to be fully characterised.

The student will carry out the first part of their thesis within the LAME team at LIPhy, which has recognised expertise in experimental spectroscopy (the MT_CKD reference model for the water vapour continuum is partly based on measurements produced by this team). The aim of this part of the research project is to characterise the temperature dependence of the pure CO₂ and CO₂+H₂O continua in the laboratory, via new low-temperature measurements (ranging from -30 to +80 °C, depending on the gas mixture under consideration), in order to test the various existing continua models. These two continua are extremely relevant for modelling CO2-rich planets (e.g. Mars and Venus) and for the study of temperate terrestrial exoplanets, which are priority targets for the instruments of the Extremely Large Telescope (ELT), currently under construction in Chile.

In the second part of the thesis, carried out within the IPAG exoplanet team, the continuum model, validated by these measurements, will enable the creation of new high-resolution opacity data (across the spectral ranges of the instruments of interest), which are essential for numerical climate and radiative transfer models. To this end, the student will use SpeCT, developed by G. Chaverot (Chaverot et al, 2025), to create k-correlate tables that will feed into a national database currently under construction. This is a highly advanced 3D climate model, taking into account the full range of atmospheric physics, including clouds and global dynamics. These advanced climate structures are essential for producing realistic exoplanetary atmospheric observables. The student will use Pytmoph3r (developed by J. Leconte, LAB), a radiative transfer code dedicated to the creation of synthetic observables, to produce phase curves for terrestrial planets with varied climates. The observables, produced in the form of albedo spectra at different planetary orbital positions and for various relevant atmospheric compositions, provide key information for our instrument scientists working on the finalisation of ELT instruments such as ANDES and PCS.

Your Work Environment

This PhD project is highly interdisciplinary and will be carried out across two laboratories: IPAG and LIPhy. The PhD student will undertake the first part of their research within the LAME team at LIPhy, which has recognised expertise in experimental spectroscopy. The second part of the thesis will take place within the Exoplanets team at IPAG, which is internationally recognised for its work in both the detection and the characterisation and modelling of exoplanets.

The Institut de Planétologie et d'Astrophysique de Grenoble (IPAG) is a joint research unit (UMR 5274) of the CNRS and the Université Grenoble Alpes. Around 170 people work at this laboratory, including 60 researchers and research lecturers, 30 engineers, technicians and administrative staff, and 80 contract staff, comprising 20 postdocs, 40 PhD students and 20 engineers or apprentices on fixed-term contracts. IPAG's research focuses in particular on stellar and planetary formation, the formation of planets and their characterisation.

LIPhy is also a joint research unit (UMR) of UGA and the CNRS. It now brings together an interdisciplinary community comprising 70 researchers and research lecturers, around sixty PhD students and postdoctoral researchers from a wide variety of backgrounds, supported by thirty engineers and technicians. LIPhy has established itself as a leading centre for interdisciplinary physics within the scientific and international community and focuses on the interfaces between physics and other disciplines, in particular the life sciences and environmental sciences, mechanics and applied mathematics.

This PhD project will significantly strengthen the collaboration that has only recently begun between these two laboratories. This jointly supervised PhD between the LAME and Exoplanètes teams therefore combines laboratory physics measurements, atmospheric modelling and planetary climatology, as well as simulations of astrophysical signals.

Constraints and risks

For the part taking place at LIPhy: use of Class 3 lasers and pressurised gases.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions