Posters

Direct detection of older, colder, closer, and smaller planets than currently accessible is the next frontier of exoplanet science. While JWST is making inroads in detection of cold planets via thermal emission, the first direct detection of exoplanets in reflected light is on the horizon with upcoming space- and ground based facilities. These platforms will use indirectly detected planets as campaign targets, however translating orbital elements, with large uncertainties, into prediction of planet location in the sky plane is challenging for planning these observations. I will present a tool I created called `projecc`, to help examine orbit solutions, identify targets and optimal observing times, and help the community decide where to allocate resources for improving orbit solutions as we prepare for reflected light detection campaigns.

During the late stages of giant planet formation, protoplanets are surrounded by a circumplanetary disk and an infalling envelope of gas and dust. For systems with sufficient cooling, material entering the sphere of influence of the planet falls inward and approaches ballistic conditions. Due to conservation of angular momentum, most of the incoming material falls onto the disk rather than directly onto the planet. Here, we investigate the structure and radiative signatures of these circumplanetary systems. A self-consistent numerical model of the temperature and density structure of the circumplanetary environment reveals that circumplanetary disks are thick and hot, with aspect ratios as large as $H/R\sim0.25$ and temperatures that can be comparable to that of the central planet. Comparing the emergent spectral energy distributions with previous semi-analytic models of these systems shows that the disk geometry has a significant impact on the radiative signatures and must be accounted for when modeling these systems. Although observing forming planets will be challenging, our results show how the observational signatures depend on the underlying properties of the planet/disk/envelope system. These models will allow future observations to constrain the physical properties of accreting protoplanets and the structure of the circumplanetary environment.

Temperate sub-Neptunes like K2-18 b are promising targets for habitability studies. JWST spectroscopy reveals a hydrogen-rich atmosphere with methane and carbon dioxide, but little water vapor. This CH4 and CO2 chemistry suggests a water-rich envelope, while the absence of H2O implies condensation below the JWST probe region. Using radiative transfer and photochemical kinetics-transport modeling, we introduce a novel framework linking the observed CO2 to CH4 ratio to the deep H2O to H2 ratio, with broad applications across sub-Neptune atmospheres. Applied to K2-18 b and TOI-270 d, our model suggests both possess water-rich interiors with approximately up to 30 percent water by volume. Tentative detection of dimethyl sulfide (CH3SCH3) or methyl mercaptan (CH3SH) is reported; our photochemical model shows these organosulfur compounds can form abiotically, challenging recent claims of biogenic origin. We also identify sulfur species such as SO2 and OCS as potential tracers of interior water content in temperate sub-Neptunes.

Transmission spectroscopy during exoplanet transits provides critical insights into atmospheric composition, temperature structure, and the presence of clouds or hazes. Integral Field Spectrographs (IFS), which offer simultaneous spatial and spectral information, are particularly well-suited for time-series observations and will play a key role in upcoming small space telescopes (~3 m class), extending observational capabilities beyond those of JWST and ARIEL. This study presents a simulation framework to evaluate the science yield of IFS-based transmission and emission spectroscopy. Starting from synthetic model spectra matched to target system parameters, we simulate observed spectra by applying instrument-specific noise using SlicerSim, and rebinning to improve signal-to-noise. Atmospheric retrievals performed with tools such as petitRADTRANS are then used to assess the precision with which molecular abundances, cloud properties, and thermal profiles can be constrained. Results indicate that IFS observations can effectively recover key atmospheric features for a range of planetary sizes and system configurations. This pipeline enables predictive assessments of instrument performance and target suitability, supporting the planning and optimization of future IFS-enabled exoplanet surveys.

Recent advances in exoplanet research underscore the importance of atmospheric studies for understanding their chemical composition and dynamics. Analyzing the light from these planets, particularly during transits, allows astronomers to detect atmospheric gases via spectral lines and measure Doppler shifts caused by winds and motion. High spectral resolution enables precise velocity measurements, while low resolution blurs these signals, limiting our ability to study atmospheric dynamics.
In this project, I analyze simulated exoplanet spectra at varying resolutions to examine how Doppler shift retrieval changes with resolution. I compare models with and without magnetic fields to assess their impact on measured velocities, applying cross-correlation techniques across orbital phases. Preliminary results indicate that magnetic fields produce measurable differences in Doppler velocities, which I am further examining as a function of spectral resolution. This work will help clarify how spectral resolution shapes the interpretation of exoplanet atmospheres.
Currently, I am adding features to the Scope package, developed by Arjun Savel at the University of Maryland. The package incorporates realistic effects such as stellar and planetary Doppler shifts, blaze functions, and signal-to-noise ratios into simulated spectra. However, generating high-SNR spectra is computationally intensive. To address this, I am developing a function that interpolates exposures between the first and last spectra, producing evenly spaced high-exposure data for analysis. Using Scope, I am investigating how initial model resolution influences retrieved Doppler shifts, with future work aimed at comparing results from 3D and 1D models. This work will provide insight into phase-resolved Doppler shifts in high-resolution exoplanet spectra.

Effects of Orbital and Continental Configurations on the Terrestrial Habitability of Earth-like Exoplanets

Jonathan Jernigan, Émilie Laflèche, Ashika Capirala, Stephanie Olson

Planetary obliquity modulates climate through its influence on the spatiotemporal distribution of incoming stellar radiation and atmospheric dynamics. The implications for planetary climate and the stability of liquid water have been thoroughly investigated in the past but their overall consequences for planetary habitability are less clear. In particular, the effects of the extreme seasonality generated by high obliquity could affect the survival of complex organisms, especially on land where seasonal temperature variations are large. The habitability of terrestrial environments will also be modulated by the spatial position and distribution of continents, as the position and shape of a landmass will strongly determine its climate and, at high obliquity, the magnitude of seasonal climate variability. Previous work has not systematically investigated the effects of obliquity and continental configuration in tandem.

To address this gap, we use cGENIE-PlaSim [1], a 3D biogeochemical model coupled to an atmospheric general circulation model, to simulate the climates of Earth-like exoplanets for various obliquities and continental configurations. This presentation will identify the obliquity and continental scenarios most favorable to terrestrial vegetation, which is a uniquely detectable form of life on Earth and the base of Earth’s global ecosystem. We will then discuss the implications of our work for the detectability of surface biosignatures on Earth-like exoplanets.

[1] Holden, P. B. et al. (2016) GMD, 9, 3347–3361.

JWST has revealed sulfur chemistry in the atmospheres of gas
giant exoplanets. Molecules such as SO2 may be sensitive tracers
of high-altitude photochemistry, atmospheric metallicity, and of
planet formation & migration. To ascertain the conditions that
determine whether (or how much) SO2 , H2 S, and other
sulfur-bearing species are present in exoplanet atmospheres, we
present a series of model grids of planetary atmospheres covering
metallicities from 0.3–1000× Solar and temperatures from 250–2050
K. With these models we map out the “SO2 shoreline,” the region
of metallicity and irradiation for which SO2 (the most easily
detected sulfur tracer) may be sufficiently abundant to be
detectable. A key conclusion is that for a given temperature, SO2
abundance is an extremely sensitive indicator of
metallicity (robust to all the other factors; mixing, plausible
C/O ratios, UV irradiation). Expected SO2 abundances also depend
strongly on overall temperature and C/O ratio; the SO2 abundance
depends surprisingly weakly on XUV irradiation, also weakly on
Kzz (for Teq ≳ 600 K), and is essentially independent of internal
temperature. Despite its detection in a growing number of giant
planets, SO2 is never the dominant sulfur-bearing molecule:
depending on temperature and metallicity, H2S, S2 , NS, SO, SH,
and even S8 or atomic S are frequently as common (or more so) as
SO2 . Nonetheless SO2 remains the most easily detectable
sulfur-bearing species, followed by H2 S, though perhaps SO and
SH could be detectable in some gas giants. Aside from a pressing
need for additional observational constraints on sulfur, we also
identify the need for future work to account for the effects of
clouds and hazes, fully self-consistent atmospheric models, 2D
and 3D models, a wider range of planetary masses and radii, and
studies to measure and refine reaction rates and molecular
opacities of sulfur-bearing species.

Eta Earth (η⊕) is one of the crucial concepts in the study of Earth’s prevalence, planetary formation, and the diversity of planetary systems. Precise estimates of η⊕ guide future space missions like the Habitable World Observatory (HWO) for biosignature detection and the broader search for life beyond Earth. While NASA’s Kepler mission broadened our understanding of exoplanets, the failure of one reaction wheel limited its capability, leaving us with a small sample of Habitable Zone (HZ) exoplanets and resulting in broad uncertainties in η⊕ estimates. Better stellar and planetary characterization leads to more accurate classification of planets as “Earth-like” and truly within the HZ. To improve η⊕ estimates, we are reanalyzing 144 Kepler confirmed and candidate planets in the HZ orbiting main-sequence FGK stars with effective temperature (Teff) between 4900K and 7000K. We present revised planet parameters using the most updated stellar data with a Python-based tool, STERNA (Synthetic Transit Lightcurve HarvestER for Exoplanet Science Cases). Statistical validation is done with TRICERATOPS. This refinement will help to reduce misclassification, eliminate false positives and remove inherent biases in η⊕ estimates. Our work will also prioritize targets for future space missions like JWST or upcoming Nancy Grace Roman Space Telescope.

Understanding cloud formation in planetary atmospheres requires accurate treatment of microphysical processes, particularly the interactions between aerosols and volatile gases. However, many current models, such as the Community Aerosol and Radiation Model for Atmospheres (CARMA), do not account for these interactions, potentially misrepresenting cloud structure, particle growth, and radiative properties. As such, we investigate the role of hygroscopic salts, such as potassium chloride (KCl), in shaping cloud properties in Y-dwarf and exoplanetary atmospheres. In this talk we will present laboratory experiments aimed at quantifying the interaction of KCl particles with water vapor under simulated Y-dwarf conditions. Using a Spherical Void Electrodynamic Levitator (SVEL), we suspend individual KCl particles and expose them to controlled amounts of water vapor across a previously unexplored temperature regime (300–450 K), representative of Y-dwarf atmospheric conditions. This setup allows for the direct observation and measurement of deliquescence and particle growth in real time, providing critical constraints to the rate of water uptake and onset of heterogeneous nucleation. Complementary experiments using differential scanning calorimetry (DSC) used to investigate latent heat release and freezing-point depressions for KCl–H₂O mixtures may also be presented. These experimental results enable us to map the thermodynamic pathways of cloud evolution and will be used to inform future updates to CARMA while more broadly highlighting the importance of incorporating salt–vapor interactions into planetary atmospheric models. By grounding our understanding in laboratory data, we aim to improve predictions of cloud formation and radiative behavior in Y-dwarfs and other salt-rich planetary atmospheres.

The Roman Space Telescope Galactic Bulge Time Domain Survey (GBTDS) is expected to detect ∼10^5 transiting planets. Many of these planets will have short orbital periods and are thus susceptible to tidal decay. We use a catalog of simulated transiting planet detections to predict the yield of orbital decay detections in the Roman GBTDS. Assuming a constant stellar tidal dissipation factor, Q, of 10^6, we predict ∼5–10 detections. We additionally consider an empirical period-dependent parameterization and find a substantially suppressed yield. We conclude that Roman will provide constraints on the rate of planet engulfment in the Galaxy and probe the physics of tidal dissipation in stars.

Around 1-10% of Sun-like stars will engulf a Jupiter-size-or-larger planet as they expand during their post-main sequence evolution, causing the planet to lose orbital energy and spiral in toward its host star’s core. These “engulfment” events may be the precursors of recently-discovered white dwarf (WD) systems that host giant planets on very small (P ~ 1 day) orbits; furthermore, the analogous process may explain recently-discovered, short-period WD-brown dwarf (BD) systems. However, the physics of engulfment is not fully understood. In this work, we simulate planet and BD engulfments with the 1D stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), expanding upon the parameter space of previous work. We also characterize the main physical processes at play, including the scaling relation between drag rate and orbital separation and the propagation of energy to the star’s surface. Our ultimate goal is to derive a general, semi-analytic formalism that predicts the end result of an engulfment, allowing for robust comparison with observed systems.

Are we alone in the universe? This is one of the most important questions we strive to answer. A new collaborative group at the University of Wisconsin–Madison is attempting to address this question. The Wisconsin Center for Origins Research (WiCOR) is an interdisciplinary group that brings together scientists from six departments to study the origins of life throughout the universe. Our first project aims to assess the habitability of Hycean worlds, which are planets that are in the super-Earth/sub-Neptune regime and composed of a hydrogen atmosphere and a water ocean surface. In this project, we are modeling the chemistry and physical conditions of protoplanetary disks that could form these Hycean planets, modeling the chemistry in the atmosphere, ocean, and core of such a planet after its formation, searching for new Hycean exoplanet targets, and characterizing their mass, density, age, and atmospheric composition. We employ a combination of laboratory studies, computer models, and telescope observations to explore the habitability of Hycean worlds. This presentation will give an overview of the project, along with results that focus on the physical conditions and chemistry used in the protoplanetary disk formation stage and after the planet is formed.

Thousands of exoplanets have been discovered in the recent decades. However, to date, only one planet in the Universe is known to contain life: Earth. To determine whether other habitable worlds exist, it is helpful to determine the physical conditions required for life on a planet. One such physical condition is the planetary magnetic field (PMF); among other processes, the PMF influences habitability by reducing atmospheric mass loss rates via photoevaporation by redirecting ions back towards the planetary surface. Over Gyr timescales, radioisotopes such as 40K, 232Th, 238U, and 235U in a planet’s core and mantle modulate magnetic field strength by changing the interior heat gradient that drives the dynamo via convective motions. The abundance of radioisotopes within a planet’s interior is expected to vary by stellar chemical composition; thus, for given a stellar system configuration, it is helpful to know what abundances of radioisotopes in a planet’s interior favor habitable conditions with respect to magnetic evolution. In this work, we consider three configurations of stellar systems, each with a single Earth-like planet orbiting in the habitable zone of a M-dwarf, K-dwarf, or G-dwarf star. Per configuration, we ran numerical simulations which varied the radioisotopic abundances of uranium, thorium, and potassium; the range of abundances were selected from observed distributions of stellar elemental abundances in the Milky Way. Our results map combinations of radiogenic element abundances to atmospheric mass losses for each configuration.

A growing set of “super-puffs”, or sub-giant planets with abnormally low densities, challenge our understanding of mass-radius relations and planetary formation. We investigate the properties required to produce physically sound structural models which match observed super-puff parameters. We select a sample of super-Earth to Neptune sized super-puff-like planets from the IPAC Exoplanet Archive database. Interior structure models are computed for each planet’s observed mass considering a range of core mass fractions (f_{core}), atmospheric specific entropy (K), and atmospheric metallicity (Z) to determine the maximum f_{core} which reproduces observed radii. We find that for a significant portion of our sample, a physically reasonable f_{core} can only reproduce the observed parameters if K is significantly enhanced. Using thermal evolution models, we investigate if enhanced radiogenic heating, irradiation, or giant impacts can account for the increased K result.

Recent JWST observations suggest that the thermal emissions of some rocky exoplanets exceed expectations from stellar irradiation alone, implying internal heat sources. Valdés et al. (2025) found that the dayside emission temperature of TOI-1468 b, while consistent with an airless bare rock, is marginally higher than the maximum temperature assuming zero albedo and no heat redistribution. Bello-Arufe et al. (2025) reported possible volcanic atmosphere on L 98-59 b, potentially due to runaway tidal heating that creates a deep subsurface magma ocean. In this study, we propose a systematic search for thermal excess in archival observations of rocky exoplanets to identify and characterize possible internal heat sources. The internal energy sources of rocky planets are closely related to their formation, evolution, composition, and physical interactions with the host star and companion planets, if in a multiplanet system. We focus on the following internal energy sources: (i) residual heat from primordial accretion and/or giant impacts, maintained by a recently lost atmosphere; (ii) tidal heating, which is important for planets with high eccentricities, potentially maintained by mean motion resonance with companion planets; (iii) induction heating due to magnetic interactions with the host star. We compile a list of candidate planets based on physical and orbital characteristics that favor thermal excess and evaluate their potential of producing thermal excess. This work aims to improve our understanding of the interior thermal processes in rocky planets and their observational signatures, contributing to the interpretation of data from the upcoming JWST Rocky Worlds DDT program.

Mie approximations fail to accurately represent the non-spherical particles that make up mineral clouds within hot Jupiter atmospheres. This necessitates laboratory measurements of cloud species’ optical properties to give insight into their chemical composition, morphology, and particle size distribution. These measurements will help deepen our observational understanding of hot Jupiter atmospheres and provide needed information for radiative balance and exoplanet atmospheric models.
Here, I present scattering and polarization data for ensembles of particles collected using the Exoplanet Cloud Ensemble Scattering System (ExCESS). Magnesium orthosilicate (Mg2SiO4) particles in the submicron to <10 micron size range serve as a starting point for laboratory analogs of hot Jupiter clouds. Particles are dry generated, and sizes measured using an optical particle sizer. A 532 nm (green) laser is passed through a polarizer and an electro optic modulator to set the polarization state before entering the scattering chamber within ExCESS. Scattering and polarization data are then collected using a photomultiplier tube jogged at 5° intervals from 20-169° on the plane of illumination. With known polarization input and measured output, full characterization of how hot Jupiter clouds interact with radiation from their host stars is possible.
Future work will include, but is not limited to, measurements of TiO2 and Al2SiO3 particles at expanded wavelengths from 405 nm (violet) to near-IR. This will allow for characterization of particle behaviors across composition, morphology, and wavelength with the goal of measurements being cataloged and openly available for use in modelling and observational studies of exoplanets and their atmospheres.

Without knowing the mass of a terrestrial exoplanet, our understanding of it will be very limited. This makes accurately measuring the radial velocity (RV) of its host star crucial. One issue with accomplishing this is that stars generate other sources of RV, such as RV signals induced by starspots. Fortunately, if we can identify and map these starspots photometrically, then we can account for their added signals and remove them from our measurements. But, on every star there exists patterns that contribute no photometric signal in stellar rotation curves called the null space. We have determined that these “unspottable” patterns do induce RV signals, much like starspots, meaning the null space could add another complicating factor to exoplanet mass measurements. We are searching for the significance of these invisible signals by creating a mathematical framework that identifies spatial patterns that can exist in a star’s null space. Using these patterns as “null space” maps, we calculate the RV signals they induce for physically reasonable flux variations on the stellar surface. We will present our results from these models and discuss the future impacts that the null space will have on detecting exoplanets using RV.

Multiplanet systems are expected to form in resonant chains as a result of disk-driven migration. Recent observational evidence suggests that young (1 Gyr) multiplanet systems tend to have fallen out of resonance. In this work, we study resonant chains breaking as a result of gravitational scattering of planetesimals and planetary embryos leftover from planet formation processes. We find that scattering resulting from planetesimals comprising ~1-2% of the total mass of a resonant chain of cold Neptunes can break the resonance and destabilize the chain in timescales on the order of 100 Myr. Notably, such Neptunes approach the inner 0.1 AU in most systems, destabilizing inner resonance chains. Given the relative prevalence of cold Neptunes as compared to Jupiter-mass perturbers, such a mechanism could provide a novel explanation for the observed lack of resonances in mature systems. Neptunes may therefore have a significant impact in shaping system architectures—in particular with respect to breaking resonances—but to date have been largely overlooked.

The discovery of exoplanets orbiting white dwarfs provides unique insights into the evolution of planetary systems in post-main-sequence stellar environments. While WD 1856-b remains the only confirmed exoplanet orbiting a white dwarf, the transit method remains a promising method for exoplanetary detection. However, the low sample size (n = 1) of confirmed planets transiting white dwarfs makes it challenging to characterize their occurrence rate. We develop a pipeline for detecting white dwarf exoplanetary transits, processing TESS photometric light curves, and applying the Box Least Squares (BLS) algorithm to identify transit signals. We focus on periodic transits with orbital periods ranging from 0.1 to 15 days and transit durations between 0.01 and 0.1 days, characteristic of short-period planets potentially orbiting compact stellar remnants. The pipeline also incorporates a pre-processing module for noise reduction and detrending, ideally optimizing the BLS algorithm’s sensitivity to subtle transit events in white dwarf light curves. While the pipeline is still in progress, we currently reach a 90% recall with a precision of 47.7% using an RMSE filter, and a precision of 51.6% using a correlation filter. This work contributes to the search for white dwarf exoplanets and provides a template for future investigations utilizing space-based photometry.

Hot Jupiter (HJ) formation remains to this day a topic of debate, with no clear or convincing argument for which of the current formation theories may be dominant. And despite the growing pool of over 500 discovered transiting HJs, the observational evidence produced from these discoveries have yet to lead to a clear path of formation. This conundrum is mainly due to issues stemming from differing discovery methods that hinder the interpretation of gathered data as a whole. To remedy this issue, this work seeks to aid the efforts of the Migration and Evolution of giant ExoPlanets (MEEP) survey in the hopes of discovering most of the remaining HJs that reside in orbits around stars brighter than a Gaia G-band magnitude of 12.5, utilizing homogenous techniques and assumptions consistent with MEEP. Furthermore, this work aims to analyze binaries with transiting HJs to characterize these constituents to search for evidence of kodai-lidov interactions that may indicate high eccentricity tidal migration (HETM). With this work, we present the most recent discoveries and characterizations of two HJ systems and one warm Jupiter (WJ) system, and discuss how the discovery of nearby stellar companions in some of these systems can provide insight into understanding how some of these systems may have formed. The WJ system in this work, TOI-4132, is a particularly peculiar system in which it hosts a WJ that showcases significant eccentricity, suggesting that this system may still be in the process of HETM.