Astronomy Colloquium Series

From Star to Stone: Characterizing Exoplanets by Studying Their Host Stars

While the number of observed small/rocky exoplanets continues to grow, our knowledge of their composition, and thus their real diversity, is still limited. Even for the small planets with measured bulk densities, these measurements often have significant errors, and degeneracies between models can cause large uncertainties in interior structure models. Host star abundances can serve as an approximation of the primordial planet-making material in the protoplanetary disk; for example, for many elements there is agreement between solar and chondritic abundances. Particularly interesting is the relative importance of C, O, Mg, and Si – the ratios of these elements in terrestrial planets control their interior structure and mineralogy, and can thus affect habitability. In this talk I will discuss how high resolution spectroscopy of host stars is helping to characterize the compositions of exoplanets, and the plans we have at Carnegie to continue investigating the Galactic diversity of planets in the era of TESS.