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Dix Planetary Science Seminar

Tuesday, November 5, 2019
4:00pm to 5:00pm
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South Mudd 365
"The Evolution of Gas in Planet-forming Disks"
Keri Hoadley, David and Ellen Lee Postdoctoral Scholar in Physics, Space Astrophysics, Caltech,


The evolution of protoplanetary disks from primordial gas- and dust-rich environments to their dispersed, debris disk state has become one of the leading topics in planet formation studies. The evolution of gas and dust through the lifetimes of these disks direct impacts their ability to form planetary systems. Understanding the driving dispersal mechanisms and their connection to the timescales for gas and dust dissipation is, therefore, critical for inferring the timescales over which planets form and evolve.

I will introduce a unique way to observe the warmest molecular gas reservoir in protoplanetary disks –molecular hydrogen (H2) ubiquitously sampled throughout the far-ultraviolet (UV-H2) – and how we sensitively probe the evolution of molecular gas over a disk's lifetime. I will discuss UV-H2 trends and results that point to a molecular-to-atomic transition of disk gas as dust is cleared from the innermost regions. I will then talk about an ongoing multi-wavelength investigation that is exploring the mechanisms that we think drive the dispersal of protoplanetary disks, by tying together the behavior of UV-H2 with IR-CO. Finally, I will touch on how future UV observatories (like Hyperion and LUVOIR) will continue to answer outstanding questions about the nature and role of UV-H2 in understanding the dispersal mechanisms and timescales in planet-forming disks.

For more information, please contact Shreyas Vissapragada by email at