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Domain 3: Atmospheres, surfaces, and interiors

Credit: ESO

The atmosphere of an exoplanet is a unique window to probe its chemistry, possibly its surface and interior conditions, and ultimately its potential for habitability (Seager 2014). In a complementary way, solar system planets and moons offer opportunities for learning about atmospheres, surfaces and interiors through probes and in-situ data. In the past several years, the study of exoplanetary atmospheres has come of age both on the observational and theoretical fronts (for reviews, see Burrows 2014, Heng & Showman 2015, and Deming & Seager 2017). It is firmly being established as a field of inquiry in its own right (Seager 2010; Heng 2017), distinct from the study of planetary atmospheres in the Solar System, while borrowing from and generalising the techniques of Earth and planetary scientists.

At the forefront of research on exoplanetary atmospheres is the use of current and next-generation facilities, both from space and from the ground, to detect and identify constituent atoms and molecules. The use of the HST (Hubble Space Telescope) and SST (Spitzer Space Telescope) to measure transmission spectra has matured (e.g., Sing et al. 2016), including the use of ultraviolet data to study the escape of the atmosphere from the gravitational well of the exoplanet (Ehrenreich et al. 2015). From the ground, the technique of using high-resolution spectroscopy has been honed to the point where the data quality rivals that of data obtained using the Hubble Space Telescope (Snellen et al. 2010; Wyttenbach et al. 2015). These observational efforts are matched by theoretical efforts to improve our interpretational techniques (e.g., Heng 2016) and advance our understanding of the physical and chemical mechanisms at work in these atmospheres (e.g., Guillot 2010; Madhusudhan 2012; Grimm & Heng 2015; Drummond et al. 2016). There have also been attempts to link the atmospheric composition to the formation history of the exoplanet (Oberg et al. 2011; Madhusudhan et al. 2014; Oberg & Bergin 2016, Mordasini et al. 2016). In parallel, attention has turned to scrutinising small, ultra-cool stars, which are the diminutive cousins of our Sun, for finding rocky exoplanets that are amenable to atmospheric characterisation (Gillon et al. 2016), including the SAINT-EX project led by Prof. Brice-Olivier Demory (SNF Professorship).

Switzerland developed strengths in the theoretical, observational and instrumentation-related aspects of atmospheres, surfaces and interiors. Domain 3 unifies, strengthens and innovates upon these strengths and activities, and makes a link with the Solar System. One of our goals is to develop within the NCCR the competences necessary to compete on the international stage in terms of procuring telescope time, securing membership on instrument-related consortia, and contributing to cutting-edge advancements in theoretical and observational techniques. Ultimately, the study of exoplanetary atmospheres and climates is geared towards the search for bio-signatures (e.g., Seager et al. 2013), an aspect we address in our bonus programme on habitability.
The research in Domain 3 will combine high-resolution spectroscopy of exoplanetary atmospheres, obtained either by direct imaging or transits, with theoretical models to interpret the data and translate them into constraints on atmospheric chemistry, temperature structure, and possibly even atmospheric escape. The long-term evolution of the atmosphere and its interaction with the interior will be studied by means of numerical modelling with solar system bodies to provide detailed benchmarks. Telltale signs of life, i.e., bio-signatures, will be sought for in the atmospheres of exoplanets using the same state-of-the-art observation techniques and theoretical models, while Mars will provide the Solar System perspective on such signatures. Finally, a virtual laboratory of exoplanetary atmospheres will be developed and used to place bio-signatures into the context of their environments.

Domain 3 includes externally funded projects.

Project 3.1: Theory and simulation of exoplanetary atmospheres
Project leader: Kevin Heng (UBE)
The rich diversity of exoplanetary atmospheres being detected and scrutinised motivates a broad theoretical approach that generalises beyond the techniques and thinking that have been developed for the solar system planets and moons. Specifically, rather than a focus on higherorder descriptions of niche areas, there is a need to develop a broad and holistic approach that combines first-order descriptions of fluid dynamics, radiative transfer and chemistry into falsifiable models that may be confronted by the astronomical data. State-of-the-art radiative transfer models will be developed jointly with project 1.2 (which considers radiative transfer in protoplanetary discs).

More information

More information is available on our dedicated website.

Team

Senior Researcher
+41 31 631 39 95
Project leader P3.1 / P3.8
+41 31 631 59 18
PhD Student
Associate
+41 31 631 36 87
PhD Student
Associate
+41 31 631 36 37

Project 3.2: Exoplanet atmospheres at high spectral resolution
Project leader: Christophe Lovis (UGE)
This project focuses on the observational study of exoplanet atmospheres by means of groundbased high-resolution spectroscopy. The goal is to probe the chemical composition and atmospheric structure of a variety of objects, ranging from hot Jupiters to temperate Earth-like planets. High-resolution spectroscopy circumvents the practical difficulties caused by Earth’s atmosphere and rivals space-based spectrophotometry in terms of exoplanet characterization potential. It reveals the physical properties of atmospheres by resolving spectral line profiles, which constrain chemical abundances, temperature profiles, global circulation patterns, and planet spin rate. Two main approaches will be pursued in this project: transmission spectroscopy of transiting exoplanets and spatially-resolved spectroscopy of very nearby (non-transiting) exoplanets using extreme adaptive optics (AO).

More information

More information is available on our dedicated website.

Team

PhD Student
+41 22 379 22 64
Research associate
+41 22 379 22 81
Assistant Professor
+41 22 379 24 44
Senior Researcher
+41 22 379 24 63
PhD Student
Associate
+41 22 379 24 64
PostDoc
Associate
+41 22 379 24 06
Project Leader P3.2
+41 22 379 24 07
Platform Leader Technology Transfer
+41 22 379 23 96

Project 3.3: Direct imaging and spectral characterisation of ultra-cool companions to nearby stars
Project leader: Damien Ségransan (UGE)
Most of the directly imaged exoplanets today are very young and warm with spectral types ranging from L to T – corresponding to effective temperatures (Teff) higher than 700 K. In most cases, the age estimate of the parent stars combined to giant planets evolutionary models bring some constraints on the mass of the discovered planets, but large uncertainties remain (Moya et al. 2010). Indeed, the evolution of massive giant planets (mass, radius, luminosity, chemical composition, Teff) is a challenging task that is mainly unconstrained. The recent discovery of the ultra-cool companion (Teff ~ 500 K) to the old main-sequence G dwarf HD4113A (Cheetham et al. 2016) with SPHERE identifies strong discrepancies between several predicted and observed planet parameters (mainly on Teff, luminosity, and mass). This study shows that deriving dynamical masses of such cool objects is critical to better understand the physics of ultracool brown dwarfs and giant planets for which almost no constraint exists beside our own Solar System. Following the work on HD4113, this project aims at identifying and studying the physics (chemical composition, evolution, mass determination) of all ultra-cool companions to nearby main-sequence stars in the separation range of 10–50 AU. Such a challenging feat is now possible thanks to: (1) a unique sample of nearby stars with promising low-mass companion candidates derived from 20 years of precise RV measurements with CORALIE/HARPS and close to five years of astrometric measurements with GAIA and (2) state-of-the-art high-contrast imaging and spectroscopic instruments installed on both ground (SPHERE/GPI) and space (JWST) facilities that allow to detect and characterise faint companions with contrasts as high as 300 000 ( Δ mag=13.5-14) in the near infrared.

More information

More information is available on our dedicated website.

Team

PostDoc / SNSF Ambizione Fellow
Associate
+41 22 379 24 76
Project Leader P3.3 / Platform Leader DACE
+41 22 379 24 79
Project 3.4: Remote-sensing of primitive objects and potential habitats in our and other solar systemsProject leader: Nicolas Thomas (UBE)
The aim of the project is to expand further our understanding of primitive solar system bodies through remote-sensing of dynamic phenomena using in situ spacecraft and to continue developing remote-sensing tools for the investigation of H2O-rich surfaces.

More information

More information is available on our dedicated website.

Team

PostDoc
Associate
+41 31 631 48 88
Project Leader P3.4 / Platform Co-Leader Technology Transfer
+41 31 631 44 06

Project 3.5: Search And characterIsatioN of Transiting EXoplanets (SAINT-EX)
Project leader: Brice-Olivier Demory (UBE)
Project leader: Brice-Olivier Demory (UBE)
This project is funded through Prof. Brice-Olivier Demory’s SNF Professorship (PP00P2_163967), independently from the NCCR PlanetS.

Links with other PlanetS projects

Project 3.5 shares a postdoc position with Project 3.1 (100% NCCR funded through Project 3.1) about the characterisation of exoplanets using phase-curve photometry with the upcoming JWST and the ESA small class mission CHEOPS.

More information

More information is available on our dedicated website.

Team

PhD Student
Associate
+41 31 631 45 35

Project 3.6: Future of upper atmospheric characterisation of exoplanets with spectroscopy (FOUR ACES)
Project leader: David Ehrenreich (UGE)
This project is funded through Prof. David Ehrenreich’s ERC Consolidator Grant (ERC-2016-COG: 724427), independently from the NCCR PlanetS.

Links with other NCCR projects
Project 3.6 is linked with the following projects within PlanetS: Project 3.1 (WP1) and Project 3.2 (WP1) for the development of ground-based high-resolution spectroscopy of exoplanetary atmospheres (shared postdoctoral position 100% NCCR funded through projects 3.1 and 3.2).

More information

More information is available on our dedicated website.


Project 3.7: PlanetsInTime: the history of planets from their origins to present day
Project leader: Christoph Mordasini (UBE)
This project is funded mostly through Prof. Christoph Mordasini’s SNF Starting Grant (BSSGI0_155816) and is hence widely independent from the NCCR PlanetS in financial respect; part of his salary is covered from SFH UBE in-kind funding though.

Links with other NCCR projects

Project 3.7 is linked with the following projects within PlanetS: Project 3.7 will work together with Project 3.1 (WP2) on the project Bern Exoplanet Tracks and comparison with observations (BEX). In this project, a self-consistent coupling is made of the atmospheric models developed in Project 3.1 with planet evolution models. The results will be compared with observations from Project 3.3. It will be developed by a NCCR PhD funded through Project 3.1 and working shared between the PlanetsInTime team (Project 3.7), Project 3.1, and Project 3.3.

More information

More information is available on our dedicated website.

Team


Project 3.8: The climates and habitability of small exoplanets around red stars (EXOKLEIN)
Project leader: Kevin Heng (UBE)
This project is funded through Prof. Kevin Heng’s ERC Consolidator Grant (CoG-771620-EXOKLEIN), independently from the NCCR PlanetS.

Links with other NCCR projects

This project is linked with project 3.1

More information

More information is available on our dedicated website.

Team

 

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