What asteroseismology can do for exoplanets: the formation and evolution of small planets

Tuesday 3 July, 10:30

Almost everything we know about exoplanets has been inferred indirectly through their host stars, making it crucial to understand stars if one hopes to learn about planetary systems. Asteroseismology provides the current gold standard of stellar characterization. In this talk, I explain how asteroseismic studies provide important new insights into the formation and evolution of small close-in planets, which the TESS survey is expected to discover in large numbers.

I show how asteroseismology can be used to detect and investigate the radius gap, which separates super-Earths and sub-Neptunes, with greater clarity than any other method - even allowing the determination of the exact location of the radius gap as a function of orbital period. This new measurement provides several key physical insights: 1) the slope of the radius gap is inconsistent with late gas-poor formation, but matches photo-evaporation models; 2) the complete lack of secure planet detections inside the gap is a result of homegeneous planet core compositions; and 3) these cores have a terrestrial composition, implying in situ formation rather than planet migration from beyond the ice line. 

I further explain how asteroseismology can be used to measure orbital eccentricities of small planets. Systems with a single transiting planet have significantly higher eccentricities than flat, multi-planet systems. I relate these findings to obliquity measurements for multi- and single-planet systems, and compare various planet formation and evolution models that can potentially explain this, and how the TESS mission can help distinguish them.

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