My Thesis in 400 Words: Luc Bazinet

Luc Bazinet, a MSc student at IREx, recently completed his degree at the Université de Montréal. Here, he summarizes his research project

Hot Jupiters are planets similar in size to Jupiter, but with temperatures exceeding 1000°C. Their large size and extended atmosphere make them ideal targets for atmospheric characterization. The extreme temperature in the atmosphere of these planets leads to physical and chemical processes that are absent in the Solar System planets.

There are telescopes both on the ground and in space. Ground-based telescopes can be larger than space telescopes, enabling them to gather more light in a given time. Since they don’t need to go through a rocket launch, the instruments aboard terrestrial telescopes can be more massive and fragile. Among these instruments are high-resolution spectrographs. These spectrographs break light down into its different colours, or wavelengths, with unrivalled efficiency.

In my thesis, I investigate the atmospheres of two hot Jupiters, HIP 65 A b and WASP-121 b, utilizing data from high-resolution spectrographs. My thesis presents the first atmospheric study of HIP 65 A b. We detect water vapour and carbon monoxide in the planet’s atmosphere and determine the concentration of these gases. We then infer the scenario of the planet’s formation. The most likely scenario is that the planet formed further from its star than it is now and then migrated to its current position.

The planet WASP-121 b is an ultra-hot Jupiter, meaning it has a temperature of over 2000°C. Water vapour, which is usually present in significant quantities in the colder hot Jupiter, is partially dissociated into its constituents. One of these products is neutral hydroxyl (OH). We detect hydroxide and water in the atmosphere of WASP-121 b. We quantify the fraction of dissociated water and compare it with the prediction of an atmospheric model. Our results agree with those of the model. We also compare dissociation on WASP-121 b with other ultra-hot Jupiters and find a preliminary trend that hotter planets undergo more dissociation.

These two studies tell us more about the composition and formation of the entire population of giant planets. This includes Jupiter and Saturn, which played a crucial role in the formation of the Solar System.

More information

Luc completed his MSc degree between 2023 and 2025, under the supervision of IREx professor Björn Benneke. His thesis is available on Papyrus.