Dr Johanna Vos

Principal Investigator

Dr Johanna Vos is an Associate Professor in Astrophysics and a Royal Society - Research Ireland University Research Fellow at Trinity College Dublin. She obtained her undergraduate degree from Trinity College Dublin before moving to the University of Edinburgh to carry out a PhD in Astronomy. She then spent the next 5 years as a Postdoctoral Fellow at the American Museum of Natural History in New York City. In 2022, she was awarded a Royal Society University Research Fellowship to build a research group in Ireland. In 2025 she received an ERC Starting Grant to lead a group studying extrasolar atmospheres with the James Webb Space Telescope.

Her publications are listed via ADS and Google Scholar

Dr Evert Nasedkin

Postdoctoral Fellow

Dr. Evert Nasedkin studies the atmospheres of giant extrasolar worlds. As a co-developer of petitRADTRANS, he primarily focusses on using atmospheric retrieval methods do determine the composition, clouds, and thermal state of brown dwarfs and young, directly imaged exoplanets, with a particular interest in understanding how these properties evolve over time. He has extensive experience with high-contrast imaging techniques using both ground-based and space-based observatories, and is currently using the NIRSpec and MIRI instruments aboard JWST to observe the weather of variable brown dwarfs.

Dr Samuel Beiler

Postdoctoral Fellow

Dr. Samuel Beiler studies the fundamental properties and atmosphere of the coldest brown dwarfs, primarily using JWST spectroscopy. This has included the first precision luminosity measurements of Y dwarfs, and quantitative analysis of carbon dioxide and phosphine abundances using modified forward models. His current work aims to use atmospheric retrievals and forward models to determine how the fundamental parameters and chemistry evolve over short and long timescales in these dynamic objects.

Cian O'Toole

PhD Student

Cian is a third year PhD student in Johanna Vos' group. Cian’s current research looks at the atmospheric variability of three early L-dwarfs using simultaneous observations from the Hubble Space Telescope in the near-infrared and the Very Large Array in the radio. Using these observations, he hopes to discern what is causing variability in these objects, whether they be due to clouds, aurora, or magnetic spots.

Maddie Lam

PhD Student

Maddie is a second year PhD student in Johanna’s group. Maddie is working on characterising the atmospheres of brown dwarfs and determining if there are any equator-to-pole variations. They are working with JWST NIRSpec and MIRI spectra of six brown dwarf objects, each with a different viewing angle. They are using atmospheric retrievals to extract atmospheric parameters, including the complex cloud structure as seen on many extrasolar worlds.

Merle Schrader

PhD Student

Merle is a second year PhD student in Johanna's group. They are working on characterising the vertical structure of brown dwarf atmospheres. To do this, they are developing a parallel pipeline that is optimised to reduce JWST NIRSpec PRISM time-resolved spectroscopic data. They are also using PCA analysis to investigate the change of the atmospheric chemistry of brown dwarfs over time.

Barry O Donovan

PhD Student

Barry is a first-year PhD student in Johanna’s group. His research focuses on characterising the atmospheres of young brown dwarfs using atmospheric retrievals. He is working with JWST NIRSpec, MIRI LRS, and MIRI MRS data to measure isotopologue ratios and extract key atmospheric parameters, including chemical abundances and cloud structure. His work aims to link atmospheric composition to formation history, providing insights into the shared origins of brown dwarfs and giant exoplanets.