Are Planets Made of Star Stuff? The Diversity of Earth-Size Exoplanets and the Relationship to Host Star Abundances
Casey Brinkman
NSF Graduate Research Fellow
University of Hawaii
We have discovered hundreds of exoplanets between 1-1.5 times the size of the Earth, indicating that Earth-size planets may be common in our galaxy. However, these planets show such a diversity in density they require some planets to be made nearly entirely of iron yet others to be made with hardly any. To contextualize this diversity in exoplanet composition, we need to understand the primordial composition of that star system and compare the ratio of iron to rock building elements in the planet to those relative abundances in its host star. However, to define this relationship between planet and host star compositions we need a larger sample of super-Earth size planets with high precision density measurements. For my dissertation, I use multiple Maunakea spectrographs to measure precise masses for Earth-size exoplanets, and use Equation-of-state modeling to find the compositions consistent with mass measurements. So far, this has revealed that Earth-size planet compositions might be even more diverse than previously thought. We determined with 3 sigma significance that an Earth-size planet, TOI-561b, is so low in density it requires a high-mean-molecular weight atmosphere: the first super-Earth of its kind.
Hosted by Prof. Weiss
Email physics@nd.edu for the zoom link.