SPS Seminar - Uncovering the Compositions of Sub-Neptune Exoplanets with JWST

When:   Thursday 5 October at 14.00

Where:  Robert Hooke/Teams Online

Speaker:  Anjali Piette – Carnegie Institute for Science

Hosted by: Jo Barstow

Abstract:

With no Solar System analogue, exoplanets larger than Earth but smaller than Neptune remain mysterious. The masses and radii of these 'sub-Neptunes' can be explained by a range of structures, from rocky interiors with hydrogen-rich atmospheres to water-rich planets. Atmospheric observations with JWST have the power to break this degeneracy by providing complementary compositional constraints. The archetypal sub-Neptune GJ1214b has recently been observed with JWST MIRI. I will present an analysis of its dayside and nightside MIRI LRS thermal emission spectra, using atmospheric retrievals to place unprecedented constraints on its atmospheric composition and aerosol properties. I will discuss these results in the context of sub-Neptune interior compositions, and will motivate future JWST observations which will allow multi-faceted constraints on this enigmatic population. In particular, sub-Neptunes which are smaller and much hotter (>2000K) than GJ1214b act as unique observational windows into the interiors of this population. With dayside temperatures above ~2000 K, these ‘lava worlds’ are expected to have atmospheres consisting of evaporated surface material. I will present new atmospheric models of these exciting targets,and discuss their observability with JWST. Current and future observations of exoplanets across the sub-Neptune regime have the potential to uncover the true natures of these exotic planets.

BIO:

Anjali did her PhD at the Cambridge Institute of Astronomy on exoplanet atmospheres with Nikku Madhusudhan before moving to the Carnegie Institute. She is interested in using exoplanet atmospheres as a probe of the diversity of exoplanet interior conditions and formation mechanisms, and values working with people from different disciplines (e.g. geophysics) to better understand exoplanets.