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ExoLunch - spring-2024

Addressing the challenges in understanding the nature of exoplanet atmospheres from their spectra

April 9, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Luis Welbanks - Arizona State University
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The 2020s and beyond will be the era of spectroscopy of exoplanet atmospheres. In just 3 years, our field has made dramatic advancements, moving from having very limited wavelength coverage and precision data from the Hubble Space Telescope (HST), to having high-precision spectroscopy over a wide wavelength range (~0.4 to 20μm) with the James Webb Space Telescope (JWST). These exquisite observations come with the opportunity to perform detailed reconnaissance of exoplanet atmospheres, explore their chemical and physical properties, and perform population-level studies to test our hypotheses for planet formation and planetary processes. Thanks to these advancements we could very well be the first generation in human history to answer whether we are alone in the universe. However, any interpretation is only as good as our understanding of the limits of the data and the model assumptions themselves, a point often overlooked. Whether exploring hot gas giants or temperate terrestrial exoplanets, the future of the field depends on our models' ability to interpret atmospheric properties from observed spectra. This new era in exoplanetary sciences invites us to overcome previous artificial boundaries between observers and theorist and merging both disciplines to fully exploit this wealth of data. In this talk, I will present my efforts to deliver a holistic view of exoplanet atmospheres, answering not only what exoplanet atmospheres are made of, but also which data drive our inferences, how reliable these inferences are, and their place within the larger astronomical context. I will present several early ground-breaking results from observations with JWST. From these observations we detect and constrain several chemical species that were previously elusive, including methane (CH4), ammonia (NH3), sulfur dioxide (SO2), carbon monoxide (CO), and carbon dioxide (CO2), alongside several precise water (H2O) measurements. I will discuss the challenges we are currently facing, and the advancements required for inferring the complete chemical inventory of our diverse exoplanet sample. Our findings underscore the transformative power of JWST and pave the way for future, in-depth atmospheric investigations of a larger exoplanet population.

A Comprehensive Framework for Modeling Photochemistry, Climate, and Habitability

April 16, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Shang- Min Tsai - UC Riverside
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Exoplanet science has rapidly progressed, transitioning from the stage of detection to atmospheric characterization. The diversity of exoplanets broadens our understanding of planetary science and provides a profound perspective on the evolution of our world. In this talk, I will give an overview of exoplanet characterization methods and the fundamental processes governing atmospheric composition. I will highlight recent JWST findings, including the first detection of photochemistry in an exoplanet atmosphere and its implications for understanding planet formation. I will address the necessity of moving beyond 1D modeling, to account for global and temporal properties. By employing a 2D—3D modeling framework, I reveal distinct spectral features and limb asymmetries relevant to transit and phase-curve observations. I will discuss the puzzles surrounding the most common class of planets, known as sub-Neptunes, which curiously find no analogues in our Solar System. I will demonstrate how studying their atmospheres can help break the internal structure degeneracies. Lastly, did JWST detect signs of life on the sub-Neptune exoplanet K2-18b? I will share our recent insights into probing microbial life on oceanic sub-Neptune exoplanets.