Most of the exoplanets have been detected via indirect methods around main-sequence solar-type stars. These techniques are limited to the study of the innermost regions of planetary systems where it is challenging to detect the atmosphere of the planets. Direct imaging is the technique used by Julien Rameau. It is the only technique able to study the outer part of planetary systems, to have direct access to the light emitted by the planet itself and to study their properties right after their formation, while they are young and thus hot and luminous. Direct imaging also enables to study the interactions between giant planets and their environment (asteroid belts).
Julien Rameau earned his PhD in astrophysics at the University of Grenoble in 2014. His project consisted in the characterization of the population of giant planets on wide-orbits. Observations by adaptive optic assisted direct imaging with the NaCo instrument at the VLT led him to discover a low-mass giant planet around a young star that also hosts asteroid belts, HD 95086. The planet HD 95086 b has peculiar atmospheric properties that make it an important object to understand the physics in the atmosphere of giant planets. He also led a large-scale survey to study the statistical properties of wide-orbit giant planets in order to infer their occurrence and how they compare to the population issued from formation models. Julien Rameau is also interested by the in-depth analysis of complex observing modes for a full and non-biased exploitation of the data.
At the University of Montréal as a post-doctoral researcher, Julien Rameau is working on the exploitation of the new generation instrument, GPI, on Gemini South, including the observations, the data reduction and the global survey analysis. Thanks to improved performances in terms of angular separation and contrast, GPI is able to explore the inner part of planetary systems to detect new exoplanets. Its performances, namely the low-resolution spectroscopy in the near infrared, also enable to characterize their atmospheric properties. GPI opens an era with an increasing number of detections and an improvement of our knowledge on their physicochemical properties. It will thus become possible to perform large-scale statistical analysis to constrain the global properties of the population of giant planets in order to understand how they form and evolve.
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