Collaborative Proposal: Measuring the Composition and Structure of Rocky Extrasolar Bodies

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White dwarf stars collected leftover rocky material from planetary systems that orbited their host stars until the stars reached their end of life and caused their planets to break apart. These "polluted" white dwarf stars can be studied using telescopes that measure their light broken down into different wavelengths. The signatures of different chemical elements appear at different wavelengths. The chemical elements found telescopically give information about the bulk chemical composition of rocky material in those disintegrating planets. The types of rocks present in the planets can be reconstructed from the bulk chemical composition. The scientists propose studies that will use spectral observations to find more polluted white dwarf stars and assess the water and rocky content of the planetary bodies that orbited the white dwarf stars, looking for signs of earth-like plate tectonics in the planetary bodies, and studying pathways for material to travel from the planetary bodies to the host stars. This project supports the mission of the NSF by promoting our understanding of the composition of planets orbiting other stars. The investigators will include students who participate in the UC San Diego STARS program and other institutional initiatives aimed at underrepresented groups in their research efforts.The investigators will continue spectroscopic observations of candidate white dwarf stars to identify those that are most heavily polluted. Estimates of the water content for all parent bodies polluting white dwarfs will be made in combination with an assessment of the water content in white dwarfs being polluted by substantial quantities of hydrogen. From a sample of nearly 100 white dwarfs, they will estimate the occurrence rate for water-rich rocky bodies in other planetary systems. For the subset of white dwarf stars that are being polluted by rocky crust and mantle material, they will conduct a deep search for the chemical signature of plate tectonics. Detections or deep limits on Ba and Sr will inform the possibility of plate tectonics for massive differentiated rocky bodies outside the Solar System. Dynamical simulations will examine the ability of collisional processes to strip massive differentiated rocky bodies of their outermost crust and mantle layers, and then track this ejecta and the body it originated from to explore how white dwarfs get polluted by material from specific regions of a rocky body.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.