Posted on November 2, 2022 by Marie-Eve Naud
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Antoine Darveau-Bernier, an iREx student at the Université de Montréal, presented his thesis in the fall of 2022. Here he summarizes the research projects he carried out as part of his Ph.D.
Studying the atmospheres of the hottest giant exoplanets, from Earth and from space
My PhD was aimed at developing data analysis techniques to study exoplanet atmospheres. I was then able to apply one of these methods to observe the second hottest exoplanet known to date, WASP-33 b. To do this, we used the SPIRou instrument located on the Canada-France-Hawaii Telescope. This planet, which is similar in size and mass to Jupiter, is so close to its star that it only takes 29 hours to orbit it! This proximity has the consequence of forcing WASP-33 ba to always show the same side of its star, a bit like the Moon with the Earth. This “dayside” is constantly irradiated by its star and can therefore reach extremely high temperatures (up to 3400°C!), approaching those of cooler stars. Our analysis has allowed us to measure for the first time the abundance of carbon monoxide present in the atmosphere of this planet, in addition to measuring the temperature present at different altitudes.
Artist’s rendering of the James Webb Space Telescope, which Antoine worked on during his Ph.D. credit NASA GSFC/CIL/Adriana Manrique Gutiérrez.
To achieve this, we had to apply a new method to distinguish the light emitted by the atmosphere of WASP-33 b, and that is buried in the signal of its star. By decomposing this light according to its different colors (wavelengths), it is possible to identify the signature of various molecules present in the atmosphere, such as carbon monoxide or water. In fact, each molecule absorbs light at specific wavelengths, giving a distinct signature that resembles a barcode. This signature is influenced by velocity variations due to the (very fast!) motion of the planet around its star. This is called the “Doppler effect”. The star also moves, but much more slowly; Therefore, it is possible to use this effect to distinguish the planet’s signal from the star’s.
I also had the opportunity to work on the development of an algorithm called ATOCA dedicated to the analysis of data from the NIRISS instrument, the Canadian contribution to the famous James Webb Space Telescope. ATOCA will make the most of the observations made by this instrument, in order to reveal the mysteries of the atmosphere of several exoplanets.
My thesis is therefore about perfecting the data analysis techniques applied to the atmosphere of exoplanets, both for observations made on Earth (with SPIRou) and from space (with JWST).
More information
Antoine completed his Ph.D. at the Université de Montréal between 2016 and 2022, under the supervision of Professor René Doyon and David Lafrenière. Your thesis will be available soon.
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