- Planétarium
Astronomers from the Montréal Planétarium and the Trottier Institute for Research on Exoplanets (IREx) at the Université de Montréal have discovered a significant number of Jupiter-like objects drifting freely through space without a host star.
Although extremely difficult to detect, these objects can be studied in depth using instruments such as the James Webb Space Telescope. The absence of a nearby star makes it possible for astronomers to characterize their atmospheres in far greater detail than is currently possible for exoplanets orbiting a star. As a reminder, the prefix exo in exoplanet refers to a planet located outside our Solar System.
The research team made this discovery by conducting a comprehensive census of stellar families near the Sun, out to a distance of 1,500 light-years. By determining how long these “planets” have been cooling in space, scientists can estimate their mass and identify the most promising targets for future study that are similar in mass to giant gas planets such as Jupiter.
Exoplanets and planemos
The term “planemo” is short for “planetary-mass object.” Planemos have properties very similar to those of exoplanets, but they do not orbit a star.
The first planemos were discovered only about 20 years ago, and there is still no official definition for them. For this reason, they are sometimes referred to as “rogue planets.”
Scientists do not yet know how most planemos form. One possibility is that they form directly from cold clouds of gas, much like stars. Another is that some once orbited a star before being ejected into space.
The evolution and age of exoplanets
In addition to detecting new planemos, the study also made it possible to determine the precise age of about one hundred stars known to host exoplanets. This represents a significant increase in the number of exoplanets whose ages are known with such precision.
These planetary systems serve as a kind of collection of snapshots at different stages of evolution. By studying them, scientists can better understand how stellar activity, planetary orbits and atmospheres evolve over time.
The full scientific results of the study are presented in a paper accepted for publication in The Astrophysical Journal Supplement Series.
Scientists behind the study
Jonathan Gagné
Researcher and Scientific Advisor at the Planétarium, Jonathan Gagné is also an Associate Professor in the Department of Physics at the Université de Montréal and an Associate Member of IREx. His work focuses on the discovery and characterization of new young stellar associations, brown dwarfs, planemos and exoplanets.
Leslie Moranta
Doctoral student Leslie Moranta conducts her research at IREx and the Montréal Planétarium under the supervision of Jonathan Gagné. She developed an algorithm to identify new young stellar associations in the Sun’s neighbourhood—ideal environments for discovering exoplanets and planemos—using data from the Gaia mission.