Passionate about young stars and exoplanets, Dr. Jonathan Gagné, astrophysicist and scientific adviser at the Planétarium, probes the Galaxy for a better understanding of the objects that inhabit the suburbs of our Sun.
Developing research at the Planétarium
Director Olivier Hernandez, hired in 2018, was given the task of developing research at the Planétarium. That was why Jonathan Gagné, a prolific young Québec researcher, was recruited in the spring of 2020. His role as scientific adviser consists in directing and developing astrophysics research at the Planétarium.
In his doctoral and postdoctoral studies, Jonathan focused on the celestial bodies that populate the area surrounding our Sun. Part of his work was devoted to young stars that may hide in their orbits exoplanets (planets outside our solar system) at the nascent stage.
Clusters of young stars
Jonathan was able to identify new clusters of young stars still unknown in our neighborhood. Those clusters are very interesting because they bring together hundreds of stars of the same age. This allows us to combine a number of methods to obtain their precise age, a measure difficult to estimate for an individual star. The age of a star gives us a lot of information about its properties, which evolve over time, as well as about the exoplanets orbiting that star, in addition to a better understanding of these unusual worlds and their very beginnings.
Studying brown dwarfs
In studying our stellar neighborhood, Jonathan also focused on another class of intriguing objects: brown dwarfs. These bodies are more massive than giant planets like Jupiter, but not massive enough to be a star. They make up the missing link between stars and planets. These objects, whose temperature can reach roughly 3,000°C at the start of their lives for the most massive of them, cool down over time.
It’s possible to find a large number of brown dwarfs that don’t orbit stars because, like stars, they can be born directly inside a molecular cloud. These isolated brown dwarfs have the advantage of not being drowned in the light of a star. They can therefore be easily observed, and studying their characteristics enables us to better understand how gaseous atmospheres behave at very low temperatures (temperatures below 0°C!).
Locating planemos in the sky
Certain isolated celestial bodies were recently discovered whose properties (mass, temperature, size) are very similar to those of giant exoplanets. We still don’t know whether these are exoplanets that were expelled from their solar systems, or whether they’re similar objects to brown dwarfs, which formed just like stars. These planemos, as they’re called, are very difficult to spot in the sky, because they’re often quite dim. As they age, planemos get cooler and become even less bright. Although hard to identify, these planemos represent a rare opportunity to study an atmosphere similar to that of exoplanets without interference by the light from a bright star. In studying planemos, astronomers also want to expand their knowledge about exoplanets.
Thanks to these studies, astronomers hope ultimately to identify planets similar to the Earth and characterize their atmospheres.
Training the next generation in astrophysics
Despite recent advances in these fields of research, much remains to be done and discovered. Jonathan Gagné is recognized around the world as a specialist in young-star associations, brown dwarfs and planemos – which led to his being awarded a grant from the Natural Sciences and Engineering Research Council of Canada (NSERC) in the “Early Career Researcher” category. That grant will permit him to continue his research and to hire trainees and students to help him in his work, and to guide future astrophysicists.
There’s no doubt that in the years ahead we’ll be hearing about the work and discoveries of Dr. Jonathan Gagné.