Author ORCID Identifier

https://orcid.org/0000-0001-7337-5936

Date of Award

Spring 4-17-2026

Document Type

Thesis (Ph.D.)

Department or Program

Physics and Astronomy

First Advisor

Elisabeth Newton

Abstract

From individual planetary systems to the Milky Way's structure, stars are the linchpin connecting astrophysical scales. Through three complementary projects, my thesis leverages these connections and large stellar surveys to offer insight into the Galaxy's dynamical and chemical history and its role in shaping planet formation and evolution. (I) I developed Protify, an automated pipeline to measure stellar rotation periods in TESS light curves, enabling rotation-based ages for thousands of stars. Applying it to overdensities of stars in eccentric Galactic orbits, thought to be post-resonant signatures of spiral arm passages, revealed unexpectedly young rotators in dynamically old populations. Because such stars could not have formed on these orbits, their 120--1250 Myr ages provide the first constraints on when spiral arms last passed through the solar neighborhood. (II) The Sun's depletion in refractory elements relative to its peers has long been attributed to either planet formation or Galactic chemical evolution. Using data-driven learning applied to Gaia RVS spectra, I inferred elemental abundances for 17,000 Sun-like stars and 50 planet hosts. The Sun remains refractory-depleted compared to both planet hosts and stars without detected planets, ruling out planet-driven explanations. I then modeled these stars' compositions as mixtures of core-collapse and Type Ia supernova contributions, which highlighted that the Sun is chemically ordinary once nucleosynthetic diversity from Galactic chemical evolution is considered. This result underscores how population-level chemical imprints of planet-related processes are often masked by Galactic-scale enrichment. (III) Finally, I re-examined reported excesses of hot Jupiters in clustered stellar environments, previously attributed to new planet formation channels. Using simulations and survey data, I showed that the giant planet-metallicity correlation manifests differently within the Galaxy's thin and thick-disk stellar populations, accounting for the observed excesses without invoking additional formation pathways. Together, this work demonstrates how disentangling stellar, Galactic, and planetary processes reshapes our understanding of each.

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