Galactic Imprints of AGB Outflows: Linking Second-Generation Planetesimal Formation to White Dwarf Pollution and Emergence of Interstellar Objects

California Institute Of Technology, Pasadena CA

Investigators

Abstract

The fate of many stars, such as our Sun, is to collapse to a small, but very hot, White Dwarf (WD) star. These WDs cease fusing light elements into heavy elements and slowly cool. Astronomers find a large abundance of heavy metals, like iron, in the atmospheres of many WDs. Theoretically, these elements should sink quickly in white dwarf atmospheres and disappear. This suggests that rocky material must fall onto the white dwarf surfaces continuously. Current understanding of this problem invokes the breakup of ancient asteroids, due to the gravity of large planets. This idea, however, is increasingly at odds with observations. The investigator proposes a new solution, that heavy elements come from collisions with the dusty outflows of dying stars. The study will explore how these planetesimals form, how their orbits change, and how they pollute white dwarfs. The research will give new insights into the final stages of planetary systems and the life cycles of stars. It will also support education and diversity through outreach programs with high school students and teachers. The project will be carried out in three main tasks. First, it will investigate how second-generation planetesimals form in the dusty outflows of asymptotic giant branch stars. Second, it will analyze the orbits of these planetesimal halos to see how much material stays bound to the white dwarfs versus how much is ejected into space. Third, it will model the process of white dwarf pollution through long-term simulations to understand how material moves to white dwarf surfaces and the dynamics within the planetesimal halos. By challenging current theories and proposing a new idea, this project aims to solve gaps in existing models of white dwarf pollution, using advanced computational tools to give new insights into the evolution of stars and planetary systems. 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.