Isotopic and Elemental Abundances in Stars and Planets

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Precise elemental and isotopic abundance measurements provide some of the strongest constraints on the formation and evolution of planets, stars, and galaxies. In the coming decades they will also inform the search for extrasolar biosignatures. This team will determine abundances of Sun-like stars, lower-mass red dwarf stars, substellar objects (brown dwarfs), and exoplanet atmospheres. The team will use this sample to provide insights on planetary evolution, stellar ages, brown dwarf interior modeling, planet and star formation, and models of galactic chemical evolution. They will further develop a craft-based outreach program to build representations of planets using origami, and they will contribute to regional science education by developing a traveling planetarium that will visit communities in rural Kansas. The team uses the iSHELL spectrograph on the 3.5m IRTF telescope to measure elemental abundances of up to 13 elements for each target, including C, O, Mg and Si. In addition, the team has pioneered the use of this instrument to measure abundances of 13CO and C18O (as well as 12C16O), thus providing isotopic abundances of C and O in stellar atmospheres for the first time. These isotopic measurements have been done for two M dwarfs; the objective of this project is to extend these measurements to a variety of other objects that have already been observed, and furthermore to make similar observations for more objects. As a galaxy ages, nucleosynthesis in massive stars and in energetic events will lead to subsequent generations of stars having more of the heavier isotopes of common elements such as C and O than their predecessors. With a galactic chemical evolution model better understood through these measurements, the team will be able to independently infer stellar ages from these isotopic abundances, as well as planetary ages from Mg, Si and other elements that are commonly found on rocky bodies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.