High Energy Astro Seminar - Julia Venturini (International Space Science Institute) - "Super-Earths, mini-Neptunes and the Radius Valley"

Thu, 14/01/2021 - 13:00 to 14:00

Title: Super-Earths, mini-Neptunes and the Radius Valley

Abstract: The existence of a Radius Valley in the Kepler size distribution, which separates super-Earths from mini-Neptunes, stands as one of the most important observational constraints to understand the origin and composition of exoplanets with radii between that of Earth and Neptune. In this seminar, I will revise the standard planet formation theory and provide insights into the existence of the Radius Valley from, first, a pure formation point of view, and second, a combined formation-evolution model. I will present results of  two works where we run global planet formation simulations including the evolution of dust by coagulation, drift and fragmentation; and the evolution of the gaseous disc by viscous accretion and photoevaporation. A planet grows from a moon-mass embryo by either silicate or icy pebble accretion, depending on its position with respect to the water ice line. We include gas accretion, type-I/II migration and photoevaporation driven mass-loss after formation. We perform an extensive parameter study evaluating a wide range in disc properties and embryo's initial location. We find that due to the change in dust properties at the water ice line, rocky cores form typically with ~3 ME and have a maximum mass of ~5 ME, while icy cores peak at ~10 ME, with masses lower than 5 ME being scarce. When neglecting the gaseous envelope, the formed rocky and icy cores account naturally for the two peaks of the Kepler size distribution. While the first peak of the Kepler size distribution is undoubtedly populated by bare rocky cores, the second peak can host half-rock/half-water planets with thin or non-existent H-He atmospheres. 
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Meeting ID: 891 0952 3146

Passcode: 485033