CAREER: How does external photoevaporation shape planets?

William Marsh Rice University, Houston TX

Investigators

Abstract

Observations have revealed a remarkable diversity of planets orbiting stars other than the Sun. Planets form in disks of gas and dust around newborn stars, but disks disappear as the stars age, limiting the opportunity for planets to form. Disks may spiral into the central star or evaporate from the inside-out via the newborn star’s photons. However, external photoevaporation from a nearby, much brighter star can destroy disks more quickly, reducing the time and materials to make planets. While this phenomenon has been observed in a few objects, this project will quantify whether such external photoevaporation is a major player in this story of planet formation. Leveraging a large dataset of young star clusters, Dr. Megan Reiter of Rice University and her research associates will measure the disks themselves, starlight impinging on them, and matter streaming away from them. In parallel, an educational program to encourage entrance and persistence in STEM fields will be implemented in two parts: an active-learning teacher training and astronomy-inspired curriculum for Houston K-12 schools, and foundational skills will be added to observational lab courses at Rice University; these interventions will preferentially help historically underrepresented groups. To quantify this environmental impact on planet formation, Dr. Reiter has secured more than 100 hours of telescope time using the integral field unit spectrograph MUSE on the European Southern Observatory's Very Large Telescope. The goal is to observe thousands of low-mass stars and their disks in high-mass star-forming regions of at least 1000 times the mass of the Sun – a sample 100 times larger than existing studies. These data cleanly separate stellar emission from the bright, variable nebular background. Spectral diagnostics indicate active external photoevaporation and quantify the mass-loss rate. A scaling relationship between incident UV flux and external disk photoevaporation will be derived, useful when theorists model the demographics of planets. The methods developed and astronomy professionals supported by this work will be in high demand when 30-meter class ground-based telescopes become available. The educational intervention will include value-engaged evaluation, a new way to test whether updated pedagogy improves retention in STEM courses at Rice and beyond. 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.