Surveying the atmospheres of TESS planets at high spectral resolution

The astonishing diversity of the thousands of exoplanets currently known naturally leads us to question the unicity of our planet and our solar system. Answering these questions ultimately requires probing the atmospheres of alien planets. Their chemical make up and physical parameters reveal clues about the true nature of an exoplanet, for instance whether it is gaseous or terrestrial. Atmospheres ultimately determine whether the surface conditions of a planet are suitable for life.

Thanks to recent technological advances in instrumentation and observational techniques, we are now ready to move from studies of very hot, gas giants (hot Jupiters), which are the easiest targets, to smaller and cooler planets. In this context, this project is focussing on a novel observational method based on very high resolution spectroscopy with ground-based telescopes. It aims at targeting the best exoplanets found by the upcoming TESS mission, which is just about to launch. It will look for new transiting exoplanets significantly smaller than previous discoveries, but still orbiting bright stars, so that following up part of these planets will become feasible. This is the first chance to fill the gap towards Earth-like planets, and what we will learn from TESS planets will be the foundation of our future hunt for signatures of life.

The technique that will be used in this project relies on comparing very high resolution spectra to models of planetary atmospheres through a process called cross correlation.
This essentially measures the match between the observed spectra and the theoretical model, similarly to matching a fingerprint. Since these planets have never been observed before at such high spectral resolution, it will also be necessary to compute a library of spectra, that will then be made available to the community.

Studying the atmosphere of TESS planets will reveal important clues about the transition between gaseous and rocky exoplanet, and the role of clouds in shaping their transmission spectrum.

Another important achievement of the project is the combination of observations from space and from the ground. So far these have always proceeded independently, however they contain highly complementary information that could be combined to improve our inference on the atmospheric properties. This project will show for the first time a systematic application of this new approach and set the foundation for a true synergy between the best observatories in space (HST and soon JWST) and on the ground (VLT and, in the next decade, the ELT).

In line with the last Consolidating Grant of Warwick Astronomy, this project will have a strong Inspirational impact. The level of engagement of the general public with exoplanet science, and in particular the quest for an Earth analogue, has risen considerably in the past decade. Arguably this is due to the fact that exoplanet science is addressing questions of great philosophical appeal, such as the unicity of life in the universe.

To ensure that this project will contribute to Inspirational Impact, we will both use existing social media channels, such as Twitter, that is already extensively utilised by the department of Physics. In addition, we foresee the possibility of launching a website aimed at the general public where the aims of the project and its relevance for future knowledge is explained in simple terms. We will adopt the model of the ongoing "Pale Red Dot" campaign, where people engage with the public through a catchy and easy-to-follow website. We will also make sure to publish regular press releases highlighting the achievements of the project, and utilised the Traveling Planetarium initiative to enhance the exoplanet-related content.

More on the long term, we foresee some potential for technology transfer and economic impact. Artificial intelligence algorithms aimed at recognising patterns, currently in development for several commercial applications, could be used to extract the signal of exoplanet atmospheres from the data that will be produced through this project. This because time resolution makes the signal appear as a coherent trail of positive cross-correlation, which is a pattern. Tuning commercial algorithms on astrophysical data, which arguably requires better precision and accuracy, would both improve the quality of commercial application, with positive impact on the experience of customers, and speed up the analysis of scientific data.