Tracking Hydrates In Refined Sub-neptunes to Tackle their Emergence and Evolution

Description du projet

À la recherche d’eau sur les sous-Neptune

Les sous-Neptune sont une catégorie de planètes dont la masse et la taille se situent entre celles de la Terre et de Neptune. Bien qu’elles soient parmi les planètes les plus courantes de la galaxie, des questions fondamentales sur leurs caractéristiques et leur origine demeurent sans réponse. La théorie la plus répandue est qu’il s’agit de naines gazeuses dotées d’un noyau rocheux et d’une exosphère gazeuse. De récentes données semblent cependant indiquer qu’il pourrait s’agir de mondes aquatiques constituées de roches, de glace et d’océans. Le projet THIRSTEE, financé par le CER entend répondre à des questions cruciales concernant la formation et l’évolution des sous-Neptune, ainsi que leurs atmosphères et leurs propriétés démographiques. S’appuyant sur des installations d’observation de pointe, le projet fera appel à diverses approches qui combinent les données de transit, de vitesse radiale et de caractérisation atmosphérique dans un nouveau cadre statistique.

Objectif

"THIRSTEE is a ground-breaking project focusing on sub-Neptunes, a class of planets with masses and radii between those of Earth and Neptune. These planets are the most common in the Galaxy, especially around Sun-like stars, but the most basic questions about their origin and nature remain unanswered. Are sub-Neptunes ""gas dwarfs"" (Earth-like cores surrounded by large hydrogen-rich envelopes formed near their observed close-in locations) or ""water worlds"" (planets formed beyond the snow line composed of a 1:1 mixture of ice and rock)? If the latter exist, what are their demographic and individual properties and how do they depend on stellar host type? Do any of them harbour liquid water oceans below their atmospheres?

The gas dwarf hypothesis has the most traction in the field, but recent evidence suggests the existence of water worlds. The observations, however, can be explained by both scenarios due to the modelling degeneracies that surround these planets. THIRSTEE aims to solve this debate using a multi-technique approach combining transit, radial velocity and atmospheric characterization data with a novel statistical framework that accounts for observational biases. This dataset constitutes a valuable addition to the community, enlarging the known sample into unexplored regions of the parameter space and enabling a direct comparison with synthetic planet populations.

THIRSTEE is designed to mitigate all the shortcomings that have prevented previous studies from reaching conclusive results about this enigmatic population. For the first time, such an ambitious program can be pursued thanks to the simultaneous operation of state-of-the-art observational facilities. The project seeks to answer key questions about sub-Neptune formation and evolution, their atmospheres, and their demographic properties. Thanks to its unique approach, THIRSTEE will revolutionize our understanding of sub-Neptunes and their potential significance in the search for life beyond Earth."