The Radius Valley as a by-product of Planet Formation: Observational Signatures of the Core-Powered Mass-Loss Mechanism

Observations have revealed a lack of planets of sizes ~1.5-2.0 Earth radii, i.e. a radius ‘valley’ or ‘gap’ in the size distribution of small, short-period exoplanets. This observation has been typically attributed to atmospheric mass-loss due to photoevaporation. However, in recent work, Ginzburg et al. (2018) and Gupta and Schlichting (2019, 2020) have demonstrated that atmospheric mass-loss, powered by the cooling luminosity of a planet and its host star’s bolometric luminosity, can also explain the origin of this radius valley, even in the absence of photoevaporation or any other process. In my talk, I will describe the key physical processes that drive this core-powered mass-loss mechanism followed by a comparison of our results with observations and the testable predictions we can make for the distribution of planets as a function of planet and host star properties. Finally, I will discuss our latest work where we present lists of planets that could be undergoing considerable atmospheric mass-loss or that might harbor secondary atmospheres abundant with high-molecular weight species, low-density interiors or both, if their evolution is indeed primarily dictated by core-powered mass-loss.