03/05/2021
By Joanne Gagnon-Ketchen

Physics colloquium, Wednesday, March 10, 2021 at 4  to 5 p.m.
Roundtable conversation with speaker: 5 to 5:30 p.m.
Location: To join contact Joanne Gagnon-Ketchen for the link. 

“Habitable Planets Orbiting Red Dwarfs: Stellar Drivers for Atmospheric Chemistry and Stability,“ Kevin France, Assistant Professor, University of Colorado Boulder 

Abstract: High-energy photons and particles from stars regulate the atmospheric temperature structure and photochemistry on orbiting planets, influencing the long-term stability of planetary atmospheres and the production of potential “biomarker” gases. Rocky planets orbiting low-mass stars (M dwarfs) will likely be the first exoplanets directly probed for signs of life, however, relatively few observational and theoretical constraints exist on the high-energy irradiance from typical (i.e., weakly active) M dwarf exoplanet host stars. 

In this talk, I will describe results from an ongoing panchromatic survey (Chandra/XMM/Hubble/ground) of M and K dwarf exoplanet hosts. The MUSCLES* Treasury Survey combines UV, X-ray, and optical observations, reconstructed Lyman-alpha and EUV (10-90 nm) radiation, and next-generation stellar atmosphere models to provide realistic inputs for modeling the stability and climate on potentially habitable planets around red dwarfs. I will present an overview of stellar impacts on planets orbiting M dwarfs and focus on three main results – 1) the evolution of the high-energy spectral energy distribution as a star’s habitable zone moves inward from 1 to 0.1 AU, including implications for the possible abiotic production of the suggested biomarkers O2 and O3, 2) characterization of the high-energy variability on active and inactive M dwarfs, with an emphasis on the potential for these impulsive events to drive large-scale atmospheric mass loss, and 3) a summary of our prospects to complete the stellar census at EUV wavelengths and spectroscopically characterize the atmospheres of potentially inhabited planets around M dwarfs in the next ~20 years. * Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems 

Bio: Kevin France graduated from Boston University with a BA in Physics and Astronomy in 2000. He has a PhD in Astrophysics from John Hopkins University (2006). He joined the Center for Astrophysics and Space Astronomy at the University of Colorado Boulder as a research associate and fellow in 2007. He was awarded the NASA Nancy Grace Roman Technology fellowship in 2012. 

In 2015 he was appointed Assistant Professor in the Department of Astrophysical and Planetary Sciences & LASP at the University of Colorado Boulder. France's research focuses on exoplanets and their host stars, protoplanetary disks, and the development of instrumentation for ultraviolet astrophysics. France was a member of the HST-COS instrument and science teams, is a regular guest observer with Hubble and ground-based telescopes, is a member of NASA's LUVOIR Science and Technology Definition Team and is the PI of a NASA-supported sounding rocket program to develop and flight test critical path hardware for a future UV/optical astrophysics and planetary science missions.