Amadeo Castro
Centro de Astrobiología, CSIC-INTA, Madrid, Spain

Abstract
Small planets located at the lower mode of the bimodal radius distribution are considered to be composed of iron and silicates in a proportion similar to that of the Earth (33% Fe, and 67% MgSiO3 in mass). However, recent discoveries are revealing a new group of light planets that are inconsistent with that description. Their low densities could be explained either by a scarcity of iron on their cores or by the presence of a significant amount of volatile elements, although both effects are not exclusive. In this seminar, I will present the discovery an characterization of the GJ 1018 planetary system based on ESPRESSO and TESS data. GJ 1018 hosts a low-density super-Earth, which turns out to be in a very unusual region of the mass-radius diagram. Based on the atmospheric composition of the host star, we estimated the iron-to-silicate mass fraction in the original proto-planetary disk, finding that although TOI-244 b could have a scarcity of iron in its interior, this effect would not be enough to explain its low density.
Instead, it should be explained by the presence of a significant amount of volatile elements, which might form an extensive secondary atmosphere. I will also discuss possible emerging trends in the new population of low-density planets, whose confirmation will require a larger sample of precisely characterized planets and hosts in this region of the parameter space.

2023 March 17, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto