Date: Monday 16-Sep-2024
Speaker: Jeehyun Yang (NASA JPL)
Title: Cross-Disciplinary Characterization of Exoplanet Atmospheres: Observation, Theory, and Experiment
Abstract: With JWST’s arrival, the demand for detailed chemical models of exoplanet atmospheres has surged. We introduce an automated approach using a chemical network generator integrated with 1D photochemical modeling, applied to atmospheres from hot Jupiters to temperate sub-Neptunes. Our framework reveals that the CO2/CH4 ratio can indicate a planet's deep interior H2O/H2 ratio. For K2-18 b, we estimate a 50% water-rich interior, while TOI-270 d shows 25% water, consistent with high metallicity. Carbonyl sulfide (OCS) and sulfur dioxide (SO2) emerge as key indicators for water-rich sub-Neptunes. Future research will explore sulfur chemistry through ab-initio and experimental approaches.
Date: Monday 30-Sep-2024
Speaker: Nicole Wallack (Carnegie EPL)
Title: Results from the JWST COMPASS (Compositions of Mini-Planet Atmospheres for Statistical Study) Program
Abstract: The last decade of exoplanet exploration has revealed that planets between the sizes of the Earth and Neptune are the most common in the Galaxy, seemingly bridging the gap between the types of planets in our own Solar System. Therefore, it is of great interest to understand how these planets formed, which we can investigate via their present-day compositions. Now that we are firmly in the era of JWST, we can begin to measure, in more detail, the atmospheres of these planets to better understand their evolutionary trajectories. Motivated by this opportunity, we designed COMPASS (Compositions of Mini-Planet Atmospheres for Statistical Study), a JWST program to rigorously compare the presence and compositions of atmospheres for 12 of these small planets. I will present results from multiple planets observed as part of the COMPASS program, highlighting our carefully determined survey design, recent observations, and lessons learned.
Date: Monday 21-Oct-2024
Speaker: Marshall Johnson (Ohio State University)
Title: Reaching for Distant Worlds: Exoplanet Atmospheres at High Spectral Resolution
Abstract: The study of exoplanets has rapidly advanced over the last three decades, with thousands of planets now known. With newly-developed techniques and instrumentation, we can now perform more detailed characterization of a select few planets. The best cases are the ultra hot Jupiters (UHJs), short-period, massive planets which host the most extreme planetary environments, with atmospheric temperatures in excess of 2200 K. I will present PIRANGA, a survey of the population of UHJ atmospheres using the PEPSI spectrograph on the Large Binocular Telescope. With the high spectral resolution, high signal-to-noise ratio spectra produced by this facility, we can detect individual atomic and molecular species in the planetary atmospheres. Furthermore, we can use these detections to constrain the structure, dynamics, and time variability of the atmospheres, providing an unprecedented view of these distant worlds.
Date: Monday 28-Oct-2024
Speaker: Kiana McFadden (U. Arizona)
Title: TBA
Abstract: TBA
Date: Monday 04-Nov-2024
Speaker: Rohini Giles (SwRI)
Title: TBA
Abstract: TBA
Date: Monday 11-Nov-2024
Speaker: Shami Tsai (UC Riverside)
Title: New Horizons in Comparative Planetary Atmospheres
Abstract: Exoplanet science has made remarkable progress. With advancements in high-resolution spectroscopy and the launch of JWST, the field has transitioned from detection to detailed atmospheric characterization. The diversity of exoplanets presents intriguing puzzles that challenge our theoretical understanding. In this talk, I will review the first detection of photochemistry on an exoplanet and discuss its implications for understanding planet formation. I will highlight some recent JWST observations, including our progress in identifying compositional trends across a wide range of temperatures. As we start to probe global atmospheric properties, I will emphasize the need to go beyond 1D models. I will introduce a 2D modeling framework that bridges the gap between 1D and 3D models, demonstrating how global circulation shapes the atmospheric composition and affects limb asymmetries. Finally, I will explore the enigmatic nature of sub-Neptune planets and share insights from our recent study on probing microbial life on sub-Neptune waterworlds. The talk will conclude with key open questions in exoplanet characterization that are within reach of current capabilities.
Date: Monday 18-Nov-2024
Speaker: Yoni Brande (University of Kansas)
Title: Aerosols and Sub-Neptune Diversity
Abstract: Recent analyses of exoplanetary atmospheres have shown that the presence of high-altitude atmospheric aerosols appears to be linked to physical planetary parameters such as equilibrium temperature. However, small sample sizes and limited spectral sensitivity (primarily from the water vapor feature visible with 1-1.8 micron G141 grism on Hubble's WFC3) make these identified trends uncertain. Previous work has, out of necessity, grouped dissimilar planets (massive Hot Jupiters as well as smaller, cooler gaseous planets) together in order to compile samples large enough to draw inferences from, but it is unclear that these planets exhibit all the same atmospheric physics which could affect their observed atmospheric spectra. I present a re-analysis of a smaller, yet more consistent sample of Neptune-size exoplanet atmospheric spectra, across a range of temperatures, confirming previously identified quadratic trends in absorption feature amplitude with temperature, as well as characterizing the intrinsic scatter of these measurements. While this scatter may be indicative of some stochasticity in the planet formation process, current sub-Neptune atmospheric models can only coarsely characterize these planets as a population. Initial JWST results show that sub-Neptunes can look very different in broader spectroscopy compared to HST's WFC3/G141 instrument, and can need much more sophisticated models to properly understand their atmospheric physics. To remedy this in the era of rich JWST atmospheric spectra, I introduce ExoHaze, a streamlined Python implementation of the CARMA aerosol microphysics code, and discuss some new results applied to JWST data.
Date: Monday 02-Dec-2024
Speaker: Mans Holmberg (Space Telescope Science Institute)
Title: Atmospheric characterisation of temperate sub-Neptunes in the JWST era
Abstract: Recent JWST detections of carbon-bearing species in the habitable-zone sub-Neptune K2-18 b have opened a new era in the study of low-mass exoplanets. With radii between 1-4 times that of Earth, sub-Neptunes dominate the known exoplanet population and exhibit a diverse range of possible interior compositions not witnessed in the solar system, including mini-Neptunes, gas dwarfs, and water worlds. Detailed atmospheric characterisation is the key to distinguishing between these different scenarios. In this talk, I will present recent JWST observations of TOI-270 d, a candidate Hycean world, using NIRSpec G395H (2.8-5.2 μm), combined with previous observations with HST WFC3 (1.1-1.6 μm). The transmission spectrum reveals strong signatures of CH4 and CO2, some evidence for CS2 and H2O, and no detection of NH3. The retrieved atmospheric composition supports the interpretation of TOI-270 d having a shallow H2-rich atmosphere over a planet-wide ocean — rather than a deep H2-rich atmosphere. Additionally, I will present an integrated interior-atmosphere modelling framework to investigate the feasibility of a gas-dwarf scenario for temperate sub-Neptune planets, using K2-18 b as a case study.
Date: Monday 09-Dec-2024
Speaker: Helena Lecoq Molinos (Space Research Institute of the Austrian Academy of Sciences)
Title: From Molecules to Clouds: Metal Oxide Nucleation in Exoplanet Atmospheres
Abstract: Observations of numerous gaseous exoplanets have revealed the presence of clouds in their atmospheres. However, current cloud formation models have so far been unable to reproduce these observations. In this talk, I will focus on the first steps of cloud formation in gaseous atmospheres: the nucleation process. I will first introduce the quantum chemical methods I have used to obtain thermochemical and spectral data of several metal oxides believed to initiate cloud formation in hot Jupiters. Then, I will show how the quantum chemical data has allowed us to calculate non-classical nucleation rates, which are up to 15 orders of magnitude higher than classical nucleation rates. Finally, I will discuss the observability of the clusters with JWST/MIRI.
Date: Monday 16-Dec-2024
Speaker: Sebastien Besse (ESA)
Title: BepiColombo - Get ready - cruise to Mercury is about to end!
Abstract: The joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) for the exploration of Mercury, BepiColombo is closing on its 6th year of cruise. After another two flybys at Mercury in late 2024 and early 2025 BepiColombo with its state-of-the-art and very comprehensive payload will orbit the planet and perform measurements to increase our knowledge on the fundamental questions about Mercury's evolution, composition, interior, magnetosphere, and exosphere. BepiColombo consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). During the cruise, BepiColombo delivered important scientific results while flying by Venus and Mercury. Due to the stack configuration of the cruise phase, the payload is not fully operational and scientific discoveries have been focused on the dynamic processes of the magnetosphere and the compositional structure of the Hermean Exosphere. As BepiColombo is preparing for its orbit insertion in late 2026, it is time for the scientific community to prepare itself for an incredible and exhaustive science investigation of Mercury.
