Two PhD project places are available to start in October 2023. These projects will focus on exoplanets in the Neptunian Desert. The desert is a region of parameter space next to the host star, where planets have very short orbital periods and receive high levels of irradiation. Planets in this regions have been discovered, but typically have Earth or Jupiter-like sizes, with a lack of planets near the size and mass of Neptune. Current theory explains this with photoevaporation - the strong radiation evaporates planetary atmospheres, exposing bare cores with smaller size below the desert. Larger planets are tidally disrupted, ripped apart by the host star.

Despite this relatively clean picture, several Neptune-size planets have recently been discovered in the desert. These are outliers, potentially extreme outcomes of the planetary formation process. We do not know how they reached their current positions, and how they avoid the processes which sculpted the desert in the first place. Several of these planets are very dense, in some cases denser than the Earth despite having many tens of Earth masses. These pose challenges to planet formation theory.

The goals of these PhD projects are to build a statistical population of desert planets, with well determined radii, masses, and densities, and to investigate the planet's internal structure. With accurate distributions of desert planet properties, we can begin to understand where this population of planets came from and how they relate to wider planet formation.

The PhDs will be part of a team along with two postdoctoral researchers, working under a UKRI Frontier Grant. This grant means the PhDs are fully funded for four years, and have a more generous travel budget than typical. There will likely be opportunities to travel to observing facilities, as well as to national and international conferences, as part of the projects. Please contact me at d.j.armstrong@warwick.ac.uk for more information or if you have any questions.