Research in astrophysics at the Planétarium: Part 2 – Making instruments for discovering the secrets of the Universe

The SPIRou spectrometer.
Credit: Équipe SPIRou / S Chastanet (CNRS / OMP)
Le spectromètre SPIRou.
  • Le spectromètre SPIRou.
  • Test cryogénique du spectromètre SPIRou en salle blanche. On aperçoit Olivier Hernandez en avant plan, ainsi que, de gauche à droite : Loïc Albert et Philippe Vallée.
  • Le spectromètre SPIRou installé au télescope Canada-France-Hawaï.
  • L'équipe canadienne termine la mise au point du spectromètre NIRPS dans les laboratoires de l'Université Laval.
  • L’observatoire du télescope de 3,6 m de l’ESO à La Silla au Chili.
Research in astrophysics at the Planétarium: Part 2 – Making instruments for discovering the secrets of the Universe

The wonderful writings of astrophysicist Hubert Reeves were an inspiration for Planétarium director Olivier Hernandez. In the course of his career, he’s participated in the development of sophisticated instruments that contribute to the operation of the world’s largest telescopes.

A passion for optics

Very early in his academic career, Olivier became interested in optical physics, and enrolled at École centrale de Marseille, France, for engineering studies. But astronomy and the wide-open spaces were a great attraction, and led to his settling in Canada and doing graduate studies in astrophysics at Université de Montréal.

After his doctorate, which focused on the kinematics and dynamics of spiral galaxies, Olivier returned to his initial passion: the design of astronomical instruments.

The SPIRou spectrometer

He first occupied the position of operations director at the Mont-Mégantic Observatory (OMM). He was also one of the founders of Université de Montréal’s Institute for Research on Exoplanets (iREx).

Following that experience, Olivier was recruited to work on the SPIRou infrared spectrometer. He was project manager, and thus directed the Montreal team that developed the camera with its infrared sensor. That instrument was installed in 2018 on the telescope at the Canada-France-Hawaii Observatory at the top of Mauna Kea on the Big Island of Hawaii. It makes studying exoplanets possible, those planets that rotate around other stars.

Studying exoplanets

When an exoplanet orbits a star, the latter oscillates slightly in the sky. By measuring the periodic change in the star’s speed with a spectrometer, we can estimate the exoplanet’s mass.

The spectrometer also allows us to break down the light of a star into its different wavelength components – or colors, if you prefer. When an exoplanet passes before its star, we can deduce the chemical composition of its atmosphere.

Astronomers are primarily interested in the Earth-like exoplanets that are located a good distance from their stars so that liquid water can be revealed on the surface. These exoplanets are more readily detectable around low-mass stars.

Unfortunately, those stars and their exoplanets mostly emit their light in infrared. That type of light is largely absorbed by the Earth’s atmosphere, but a brief window is accessible from our planet. The spectrometer makes it possible to probe those exoplanets.

The NIRPS spectrometer

Olivier next directed a large-scale international project: the NIRPS (Near Infra-Red Planet Searcher) spectrometer. That instrument, which resembles SPIRou, is in the process of being installed on the 3.6-meter telescope of the European Southern Observatory (ESO) in La Silla, Chile. Designed to function in infrared, it will complete the research carried out with the HARPS spectrometer installed on the same telescope, but which functions in visible light. NIRPS should be operational by the end of 2022.

Working on the James Webb Space Telescope

The best way to observe in infrared is to get free of the Earth’s atmosphere by placing a telescope in space. That’s what the James Webb Space Telescope will do. Canada contributed to the project by designing two instruments, including an infrared imaging spectrometer (NIRISS) intended for the study of exoplanets. The very high resolution of the Webb telescope will allow for detailed study of the exoplanets discovered by SPIRou and NIRPS. Olivier was the manager of the Université de Montréal and Mont-Mégantic Observatory engineering team for the design of that instrument.

Seeing bigger with a 39-meter telescope

Olivier remains involved in the design of new instruments. He serves as consultant with the OMM and iREx teams on the ANDES project. This involves a high-resolution spectrometer that will observe in visible and infrared light simultaneously. It’s to be installed on the future telescope, which will be 39 meters in diameter: the Extremely Large Telescope (ELT), currently being built in Chile by the ESO. That project, still in its infancy, will require much more work before the ELT goes into operation in 2027.

The instruments that Olivier Hernandez develops enable astrophysicists like Jonathan Gagné to study exoplanets. The ultimate goal is to one day find a new habitable Earth.


Read also:

Research in astrophysics at the Planétarium: Part 1 - Discovering the neighborhood of the Sun

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