My time at IREx: Charles Cadieux

Charles Cadieux joined IREx in 2018 as a Master’s student. After completing his doctoral studies, he remained a part of our team as a postdoctoral researcher for six months at the Université de Montréal, working with JWST data. Since October 2025, he has been a postdoctoral research at the University of Geneva, where he still collaborates with the IREx team. Here, she answers some of our questions about his postdoctoral fellowship at IREx.

IREx: What did you like most about your time in Montreal?
Charles: I was already very familiar with the IREx group, having completed my PhD studies in Montreal. I am very grateful for the opportunity to see my exceptional colleagues at IREx daily and to continue the many collaborations we had built over the past few years.

IREx: What was the most important project(s) you led at iREx?
Charles: During my short six-month stay as a postdoctoral fellow at IREx, I worked on numerous projects, the most important of which was the development of data analysis tools for the James Webb Space Telescope.

IREx: What question(s) were you trying to answer in this project?
Charles: At IREx, several of us use the Webb Telescope to study the atmospheres of exoplanets. We use a high precision technique called transmission spectroscopy, which involves filtering and analyzing the light that passes through an exoplanet’s atmosphere as it transits in front of its star. The analysis tools I have worked on not only determine whether an exoplanet has a gaseous envelope, but can also deduce its chemical composition. Although other similar tools exist, we have made an effort to make ours easily accessible, especially for new James Webb users who want to familiarize themselves with this type of spectroscopic analysis.

IREx: What did you discover?
Charles: I worked on transit observations of the hot Jupiter WASP-127 b with the NIRISS instrument on Webb. This exoplanet is a gas giant slightly less massive than Saturn, but it orbits its star in just four days! It is composed mainly of a thick atmosphere of hydrogen and helium, but also of various other molecules whose chemical inventory can be determined with the James Webb. We have discovered an extremely detailed spectrum, potentially one of the richest observed to date with Webb. However, the analysis is still ongoing, so I can’t say anything else at this stage!

IREx: What motivates you in exoplanet research
Charles: This year marks the 30th anniversary of the discovery of the first exoplanet. The beginning of operations of the Webb Space in 2022 has completely revolutionized this relatively young research field. It’s very easy to stay motivated, because every week brings new discoveries, each more intriguing than the last. It really feels like we are living in a golden age of exoplanet research.

IREx: Why do you think people should be interested in this kind of work
Charles: Our universe is so vast and filled with planets similar to Earth, whose surface conditions could be conducive to the development of life as we know it. We are only at the very beginning of exploring these potentially habitable worlds. We could be the first humans to answer the famous question, “Is there life beyond Earth?” which, in my opinion, is reason enough to spark the curiosity and interest of the general public.

IREx: How will your time with us help you in your new job?
Charles: I recently started a new position on October 1st as a postdoctoral researcher at the University of Geneva. My doctoral studies and subsequent time at IREx have strengthened my ability to conduct research independently, a skill that is essential in my new role.

Read Charles’ researcher profile at the University of Geneva.