Julien de Wit

Research Interests

My research begins with a data-driven curiosity about newly accessible pieces of reality: how far can we reliably push observations and modeling to reveal the nature of worlds we have never seen? This approach underpins my broader question: Where can we reliably find habitats in the Milky Way? As new facilities open windows onto distant planetary systems, humanity is entering a defining moment in which we can study extrasolar climates with increasing clarity.

Over the past fifteen years, I have worked to build the empirical, modeling, and community foundations needed for this progress—bringing math, physics, and data science together to transform exoplanet spectroscopy from a simple tool for molecular detection into a science for exploring planetary environments. Because today’s most detailed observations come from transit spectroscopy of Earth-sized planets around ultracool dwarf stars, my group develops methods to interpret these faint signals reliably, addressing challenges such as incomplete opacity data, complex stellar surfaces, and the need to derive atmospheric properties and planetary masses directly from spectra.

This data-first philosophy also drives our work closer to home: we use the same precision techniques to detect and characterize small solar-system bodies, reveal new asteroid populations, and demonstrate JWST’s growing role in planetary defense.

Topics I investigate:

• Atmospheric characterization and climate inference for terrestrial exoplanets (e.g., TRAPPIST-1)
• Physics- and sata-based solutions to the opacity and stellar contamination challenges in exoplanet spectroscopy
• New spectroscopic techniques to derive planetary masses, properties, and (in)habitability
• Discovery and population studies of small exoplanets and substellar companions around small stars (red and white dwarfs)
• Planet–star coevolution: tidal asteroseismology, stellar activity, and radiative/tidal interactions
• Mapping and dynamical characterization of exoplanet atmospheres from time-resolved data
• High-precision detection and physical interpretation of small bodies, including JWST-enabled planetary defense (e.g., 2024 YR4)

Biographic Sketch

Julien de Wit’s primary interest and expertise lie in data science, where math and science are brought together to make sense of newly accessible aspects of reality. He holds a bachelor’s degree in physics and mechanics (2008) and a master’s in aerospace engineering (2011) from the Université de Liège. Previously, in 2010, he completed a master’s in aeronautic engineering from the Institut Supérieur de l’Aéronautique et de l’Espace (ISAE), concurrent with master’s studies in astrophysics, planetology, and space systems science at ISAE and the Université de Toulouse. De Wit went on to pursue doctoral and postdoctoral studies in the Department of Earth, Atmospheric and Planetary Sciences (EAPS) at MIT, earning his PhD in 2014 before joining the EAPS faculty in 2018.

In 2017, de Wit was part of an international team, including astronomers from MIT and the University of Liège (Belgium), that announced the discovery of seven temperate, rocky planets orbiting the ultracool dwarf, TRAPPIST-1. Since then, de Wit has initiated atmospheric exploration of the TRAPPIST system with the Hubble Space Telescope and spearheaded the continued search for more terrestrial planets circling faint, nearby stars by expanding the SPECULOOS telescope network into the northern hemisphere with the installation of MIT’s Artemis telescope at the Teide Observatory (Tenerife, Spain). Ushering in the era of terrestrial exoplanet atmospheric surveys, de Wit has developed and applied new analysis techniques to map exoplanet atmospheres, study the radiative and tidal planet-star interactions in eccentric planetary systems, constrain the atmospheric properties and mass of exoplanets from transmission spectroscopy, and reveal the smallest main-belt asteroids to inform our understanding of meteorites.