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Physics Astrophysics Earth and Planetary Astrophysics

astro-ph.EP Watch Earth and Planetary Astrophysics

Friday 7 August

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

The Kepler and TESS Asteroseismic Consortia - A Historical Overview

Mikkel N. Lund and Tiago L. Campante

This overview is, in short, about people. About an idea that grew into a consortium, then a community, and finally a way of doing asteroseismology in the space era. The Kepler Asteroseismic Science Consortium (KASC) and later the TESS Asteroseismic Science Consortium (TASC) are not just organisational structures to access data. They became collaborative ecosystems in which students, postdocs, and senior scientists learned to work together across continents, time zones, and occasionally differing opinions about filters. The idea for this booklet did not emerge from a formal meeting or a funding call. It emerged-appropriately enough for an international collaboration-over a beer. More precisely, over a beer (truth be told, more than one) at Beer Lab University in Honolulu, during the TASC7/KASC14 Workshop in 2023. Google Maps now informs us that this particular Beer Lab location is "permanently closed", which seemed at first like an ominous metaphor for fading inspiration. Fortunately, we have since learned that Beer Lab simply moved across the street, proving that good ideas, like good consortia, tend to reinvent themselves rather than disappear entirely. Somewhere between discussions that night and many others over the years, we found ourselves revisiting stories we had long heard from our former supervisors and more senior colleagues; stories of how KASC was negotiated, how the first working groups were formed, how data were filtered (a saga in its own right!), and how trust was built. This book is therefore an attempt to capture some of that collective memory, while we still have access to the primary sources. It is timed to celebrate the return of the KASC/TASC Workshop Series to Aarhus in 2026, where the consortia's original framework was set in motion. There is something fitting about reflecting on the journey of KASC and TASC as the community gathers again where it all began.
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Earth and Planetary Astrophysics

An Observational Study of Systematics in Differential Transmission Spectroscopy Using HFOSC on the Himalayan Chandra Telescope

Manjunath Bestha, Athira Unni, T Sivarani et al. (+2 more)

Ground-based low-resolution transmission spectroscopy requires photometric precision of a few hundred parts per million, making it sensitive to instrumental and atmospheric systematics. This work studies the systematic effects affecting differential transmission spectroscopy using the Hanle Faint Object Spectrograph Camera (HFOSC) on the 2-m Himalayan Chandra Telescope (HCT). The study was motivated by an additional flux drop observed in the white-light curve of HAT-P-1 b. HAT-P-1 b is an ideal target for differential spectrophotometry because it has a visual binary companion with similar brightness at a suitable separation, allowing the companion star to be used as a reference. To investigate the origin of this feature, we analyzed several observational parameters, including FWHM variations, spectral trace motion, centroid drift, and spectral shifts. We also observed WASP-33 b in slitless mode to test whether differential slit losses could explain the observed systematic. In addition, observations of WASP-12 b were used to derive a broadband optical transmission spectrum using common-mode correction. The additional flux drop is unlikely to be caused only by differential slit losses, since similar differential centroid and spectral shifts are present in both slit and slitless observations. The results suggest that the observed systematic may be related to field-dependent distortions and pointing-dependent instrumental flexure, although its exact cause is still unknown. Overall, this work highlights the importance of understanding and reducing observational systematics in ground-based exoplanet transmission spectroscopy, especially for measurements that require photometric precision of a few hundred parts per million.
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All authors Manjunath Bestha, Athira Unni, T Sivarani, Parvathy M, Devika Divakar

Earth and Planetary Astrophysics · Cross-listed from astro-ph.HE

Probing Variations in Earth's Ionosphere Using Pulsars

Yanqing Cai, Ziwei Wu, Weiwei Zhu et al. (+24 more)

We present high cadence 10-minute rotation measure (RM) monitoring of PSR~J0814+7429 using the LOw-Frequency ARray, aiming to probe ionospheric variability along the pulsar line of sight (LoS). By separating the ionospheric contribution from the observed RM, we quantitatively reconstruct the diurnal variation of the ionospheric electron density along the pulsar LoS based on the World Magnetic Model. The derived variations exhibit clear solar-driven modulation, including the ionospheric noontime bite-out phenomenon, and show good agreement with the LoS total electron content reconstructed from independent global vertical total electron content maps. These results demonstrate the feasibility of using pulsars as probes of temporal variations in the electron density of the Earth's ionosphere.
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All authors Yanqing Cai, Ziwei Wu, Weiwei Zhu, Joris P. W. Verbiest, Ningbo Wang, Moochickal Ambalappat Krishnakumar, Lars Künkel, Jörn Künsemöller, Yulan Liu, Nataliya Porayko, Golam M. Shaifullah, Caterina Tiburzi, Marcus Brüggen, Ralf-Jürgen Dettmar, Ziyao Fang, Qiuyang Fu, Jiawei Jin, Caisong Liu, Lingqi Meng, Xueli Miao, Jiarui Niu, Dominik J. Schwarz, Christian Vocks, Mengyao Xue, Mao Yuan, Youling Yue, Zhen Zhang

Thursday 6 August

Earth and Planetary Astrophysics · Cross-listed from physics.ao-ph

The iSTORM Instrument for Airborne Measurements of Gamma-Ray Emissions from Thunderstorms

Daniel Shy, J. Eric Grove, Bernard Phlips et al. (+7 more)

The in-Situ Thunderstorm Observer for Radiation Mechanisms (iSTORM) is a gamma-ray spectrometer to study gamma-ray transients originating from thunderstorms, such as glows and terrestrial gamma-ray flashes (TGFs). It is designed and built by the U.S. Naval Research Laboratory for deployment aboard a NASA ER-2 aircraft. Using an array of 32 one-inch-diameter $\mathrm{CeBr}_3$ scintillators read out with silicon photomultipliers (SiPMs), the instrument achieves an energy range of $\sim 250 \ \mathrm{keV}$ to $5 \ \mathrm{MeV}$ under flight conditions, with a total geometrical area of $157 \ \mathrm{cm^2}$. One of two gamma-ray instruments in the ALOFT campaign, iSTORM recorded glows, terrestrial gamma-ray flashes (TGFs), and the newly discovered flickering gamma-ray flashes (FGFs).
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All authors Daniel Shy, J. Eric Grove, Bernard Phlips, Alena Schell, Mary Johnson-Rambert, Mason Quick, David Corredor, Scott Podgorny, Roy Salinas, Mitch Davis

Earth and Planetary Astrophysics

Multi-epoch ultraviolet observables for breaking the radius-albedo degeneracy in directly imaged exoplanets

Suniti Sanghavi, Robert A. West and Pin Chen

Direct imaging measures how bright a planet appears in reflected starlight, but brightness alone cannot tell whether the planet is large and dark or small and bright. This radius-albedo degeneracy limits the characterization of non-transiting exoplanets, including those targeted by the Habitable Worlds Observatory (HWO). From multi-epoch observations we construct ultraviolet observables that are independent of planetary radius: the normalized 400 nm lightcurve shape, the ultraviolet intensity and polarization colors, and the degree of linear polarization. In a clear 360-400 nm spectral window where Rayleigh scattering is strong and bright ultraviolet surfaces are nearly colorless, these observables constrain the atmospheric column, the surface reflectivity, and, when relevant, the observed phases before radius is inferred. Using the GPU accelerated vector radiative transfer model vSmartMOM, we test how uniquely these radius-free observables determine the scattering state at signal-to-noise ratios (SNRs) of 5, 20, and 100. For the chosen six phase sequence, spectropolarimetry gives median radius consequences of 9.5%, 3.3%, and 0.45% when the phases are known. If the phases are unknown, six distinct epochs keep the penalty modest at low SNR and negligible at moderate-high SNR, with median consequences of 14%, 3.2%, and 0.47%, respectively. Removing polarimetry degrades the result, especially in the HWO simulations where phase coverage is restricted by inner working angle. For solar twin systems at 6 and 12 parsecs, the required six-phase campaigns fall in the allotted range of a few hundred hours, making this a clear observing path to planetary radii from HWO's reflected-light detections.
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Earth and Planetary Astrophysics

Alkali Metallicity, Mineral Clouds, and Deep Atmospheric Variability on Jupiter

Xi Zhang, Jiheng Hu, Cheng Li et al. (+1 more)

The bulk elemental abundances of Jupiter provide critical insights into its formation history and interior structure. Recent observations by the Juno Microwave Radiometer (MWR) reveal a deep Jovian atmosphere significantly depleted in electrons, implying an alkali metal (Na, K) abundance of 10^-1 - 10^-5 times solar. This depletion stands in sharp contrast to the supersolar volatile enrichments measured by the Galileo probe. We propose that this apparent depletion arises from mineral cloud-induced processes deep in the atmosphere. We explore two physical mechanisms using thermochemical and microphysical modeling. In the "chemical sequestration" scenario, vigorous vertical mixing lofts deep refractory condensates (e.g., spinel) into the 1000-2000 bar region, where they react to form alkali feldspars (albite) and feldspathoids (leucite), efficiently sequestering gaseous Na and K. In the "dust-catalyzed recombination" scenario, the bulk alkali inventory remains gaseous, but the free electron density is suppressed by dust-plasma interactions. Thermally emitted alkali ions from the surfaces of micron-sized iron and silicate grains significantly increase the cation density, driving rapid recombination of free electrons. Both mechanisms allow for a bulk solar or even supersolar alkali inventory while suppressing the electron density to match Juno observations. Analyzing an extended dataset of MWR observations with 61 perijoves, we detect spatial variability in the deep atmosphere that suggests modulation by mineral clouds. Our findings challenge the traditional rainout framework, unveiling a deep "mineralogical zone" in Jupiter shaped by dynamics and heterogeneous chemistry, resembling the photospheres of hot exoplanets and brown dwarfs.
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All authors Xi Zhang, Jiheng Hu, Cheng Li, Quentin Williams

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Optomechanical Design of the MANTIS SmallSat: An Extreme-, Far- and Near-Ultraviolet Spectrograph for Exoplanet Host Stars

Brian Fleming, Briana Indahl, Dmitry Vorobiev et al. (+16 more)

The MANTIS (Monitoring Activity of Nearby sTars with uv Imaging and Spectroscopy) observatory is a compact, multi-instrument small satellite designed for simultaneous extreme- (EUV; 100 - 560 Angstrom), far- (FUV; 1150-1800 Angstrom) and near-ultraviolet/visible (NUV/VIS; 2000-6400 Angstrom) spectroscopy of low-mass stars. The EUV optical system consists of a first-of-its-kind Hettrick-Bowyer grazing incidence telescope contributed by the Italian National Institute for Astrophysics (INAF) feeding an advanced e-beam lithographic etched variable line spacing grating developed at Pennsylvania State University (PSU). The resulting low-resolution spectrum is imaged on an advanced microchannel plate detector with a potassium iodide (KI) photocathode for extremely low background noise, resulting in a limiting sensitivity for MANTIS that exceeds that of the last EUV-sensitive astrophysics point-source spectrograph, the Deep Survey/Spectrometer (DS/S) on EUVE. The FUV and NUV/Optical channels are fed by a compact rectangular telescope that focuses onto a series of point-source apertures. The diverging beam is refocused and the FUV band dispersed by a holographic grating, then folded back onto the same detector as the EUV channel by a toroidal fold mirror. The zero-order light is picked off by a flat NUV grating, with the NUV/Optical spectrum recorded on an e2v CCD 42-10 detector. The MANTIS spacecraft is a custom build that leverages the experience derived from prior University of Colorado - LASP SmallSats for avionics, power, communications, and mechanical structure. MANTIS is projected to be completed in 2027 with an anticipated 2028 launch as an ESPA-class payload on a rideshare opportunity.
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All authors Brian Fleming, Briana Indahl, Dmitry Vorobiev, Kristina Davis, Kevin France, David Wilson, Nicholas Kruczek, Timothy Hellickson, Emily Farr, Marta Civitani, Davide Sisana, Kotish Grover, Laura Proserpio, Stefano Basso, Vincenzo Cotroneo, Fabien Grise, Randall McEntaffer, Oswald Siegmund, Adrian Martin

Earth and Planetary Astrophysics

Juno Microwave Observations Reveal Jupiter's Deep Alkali-Chlorine Relation

Xi Zhang, Jiheng Hu, Cheng Li et al. (+2 more)

The longest-wavelength channel of the Juno Microwave Radiometer (MWR) probes Jupiter's kilobar atmosphere through free electrons produced by sodium and potassium ionization. Under equilibrium chemistry the electron abundance is the small residual of the charge balance between alkali cations and the anions Cl- and HS-. Chlorine is not directly measurable in Jupiter's deep atmosphere because gaseous HCl is removed from the observable atmosphere by NH4Cl condensation, whereas sulfur has been measured by the Galileo probe. The MWR-derived electron measurement therefore constrains the alkali-to-chlorine ratio rather than the alkali abundance alone. We combine the MWR observations with equilibrium chemistry and microwave radiative transfer in a Bayesian framework, finding that the deep gas-phase elemental alkali-to-chlorine abundance ratio is (Na+K)/Cl = 0.05 over 0.3-5 times solar in chlorine, about 180 times below the protosolar ratio of 8.7. At 3 times solar chlorine, the inferred alkali metallicity is 1.6 x 10^-2 times solar (1 sigma: 1.2 x 10^-2 - 2.7 x 10^-2 times solar), while at low chlorine abundance HS- sets an alkali floor near 10^-3 times solar. The inferred gas-phase alkali abundance exceeds the ~10^-5 times solar threshold by more than two orders of magnitude and rules out the long-proposed global kilobar radiative zone. Because sodium and potassium are refractory whereas chlorine is volatile, the inferred ratio provides a new diagnostic of the rock-to-ice balance in the solids accreted by Jupiter. This compositional interpretation assumes equilibrium chemistry; if lofted mineral clouds instead control the electron abundance under disequilibrium conditions, the inferred alkali-chlorine relationship need not hold.
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All authors Xi Zhang, Jiheng Hu, Cheng Li, Louis Siebenaler, Yury Aglyamov

Earth and Planetary Astrophysics

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems VIII: patchy forsterite and enstatite clouds in the atmosphere of VHS 1256 b, retrieval lessons learned and outlook to the future

Niall Whiteford, Jacqueline K. Faherty, Ben Burningham et al. (+123 more)

JWST defines a new era for the data-driven approach of retrieval modelling, which has become a cornerstone tool for the statistical inference of exoplanetary and brown dwarf properties. The Early Release Science program #1386 observations of VHS 1256 b represent a huge jump in data quality, data quantity and spectral coverage for such objects. VHS 1256 b is a young, planetary mass and extremely variable companion that populates the enigmatic L/T cohort of substellar atmospheres. In this first retrieval analysis of the full 1 - 18 micron dataset, we apply the Brewster retrieval framework to the NIRSpec and MIRI spectroscopic observations of VHS 1256 b, exploring a variety of cloud species and structures. Using Delta(BIC) we find that the data is best described by a forsterite (Mg$_{2}$SiO$_{4}$) and enstatite (MgSiO$_{3}$) cloud combination. Our analysis shows a strong preference for patchy silicate cloud coverage, which aligns with VHS 1256 b's extensive and well documented spectral variability. Our retrieval is able to place constraints on the abundances of H$_{2}$O, CO, CO$_{2}$, CH$_{4}$ as well as NH$_{3}$. We also show that the retrieved parameters are sensitive to the data used and the relative signal-to-noise ratios between data from different instruments. We conclude with the next steps for the wider retrieval community to better understand young and cloudy exoplanetary atmospheres.
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All authors Niall Whiteford, Jacqueline K. Faherty, Ben Burningham, Johanna M. Vos, Simon Petrus, Polychronis Patapis, Beth A. Biller, Andrew Skemer, Sasha Hinkley, Emily Calamari, Genaro Suárez, Kelle L. Cruz, Brittany E. Miles, Aarynn L. Carter, Francisco A. Martinez, Melanie J. Rowland, Olivier Absil, Arthur D. Adams, William O. Balmer, Anthony Boccaletti, Mariangela Bonavita, Mickaël Bonnefoy, Mark Booth, Brendan P. Bowler, Zackery W. Briesemeister, Marta L. Bryan, Per Calissendorff, Faustine Cantalloube, Benjamin Charnay, Gaël Chauvin, Christine H. Chen, Elodie Choquet, Valentin Christiaens, Gabriele Cugno, Thayne Currie, Camilla Danielski, Matthew De Furio, Trent J. Dupuy, Samuel M. Factor, Michael P. Fitzgerald, Jonathan J. Fortney, Kyle Franson, Julien H. Girard, Eileen C. Gonzales, Carol A. Grady, Thomas Henning, Dean C. Hines, Callie E. Hood, Kielan K. W. Hoch, Alex R. Howe, Markus Janson, Paul Kalas, Jens Kammerer, Grant M. Kennedy, Pierre Kervella, Minjae Kim, Daniel Kitzmann, Adam L. Kraus, Masayuki Kuzuhara, Pierre-Olivier Lagage, Anne-Marie Lagrange, Kellen Lawson, Cecilia Lazzoni, Jarron M. Leisenring, Ben W. P. Lew, Michael C. Liu, Pengyu Liu, Jorge Llop-Sayson, James P. Lloyd, Anna Lueber, Bruce Macintosh, Mathilde Mâlin, Elena Manjavacas, Sebastián Marino, Mark S. Marley, Christian Marois, Raquel A. Martinez, Elisabeth C. Matthews, Brenda C. Matthews, Dimitri Mawet, Johan Mazoyer, Michael W. McElwain, Stanimir Metchev, Michael R. Meyer, Maxwell A. Millar-Blanchaer, Paul Mollière, Sarah E. Moran, Caroline V. Morley, Sagnick Mukherjee, Paulina Palma-Bifani, Eric Pantin, Marshall D. Perrin, Laurent Pueyo, Sascha P. Quanz, Andreas Quirrenbach, Shrishmoy Ray, Isabel Rebollido, Jea Adams Redai, Bin B. Ren, Emily Rickman, Steph Sallum, Matthias Samland, Benjamin Sargent, Joshua E. Schlieder, Karl R. Stapelfeldt, Jordan M. Stone, Ben J. Sutlieff, Motohide Tamura, Xianyu Tan, Christopher A. Theissen, Pascal Tremblin, Taichi Uyama, Malavika Vasist, Arthur Vigan, Kevin Wagner, Jason J. Wang, Kimberly Ward-Duong, Schuyler G. Wolff, Kadin Worthen, Mark C. Wyatt, Marie Ygouf, Alice Zurlo, Xi Zhang, Keming Zhang, Zhoujian Zhang, Yifan Zhou

Earth and Planetary Astrophysics

Estimating Harmonic Coefficients of Asteroids through LiAISON Navigation

Jun Maruyama and Simone Servadio

This paper evaluates the Linked Autonomous Interplanetary Satellite Orbit Navigation (LiAISON) method in near two-body asteroid systems. While LiAISON's usefulness has been proven in multibody environments such as the cislunar region, the application of a two-body system with gravity perturbations has not been sufficiently demonstrated. Vesta and Ceres are good candidates to test LiAISON, because the asteroids have sufficiently strong perturbations to use LiAISON method. The study utilizes a Multi-Model Adaptive Estimation (MMAE) framework integrated with Unscented Kalman Filters (UKF) to estimate the spacecraft states and perturbations using only range and range rate measurements. Results from the Monte Carlo analysis indicate that the proposed framework makes accurate and consistent estimates of position, velocity, and the perturbations for cases of Ceres and Vesta.
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Earth and Planetary Astrophysics · Cross-listed from hep-ex

Estimating the sensitivity of the IceCube Upgrade to probe the interior of the Earth using atmospheric neutrino oscillations

The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams et al. (+420 more)

The IceCube Upgrade is a densely instrumented central region of the IceCube Neutrino Observatory, deployed during the 2025-26 polar season. It will reduce the detector's energy threshold and improve overall reconstruction capabilities for multi-GeV atmospheric neutrinos, which in turn enhance their sensitivity to Earth matter effects as they traverse through the deep Earth. In this study, we describe the potential of the IceCube Upgrade to observe Earth matter effects on atmospheric neutrinos and estimate the detector's sensitivity to probe key features of the Preliminary Reference Earth Model by utilizing these observations. We highlight the IceCube Upgrade's capability to estimate the mass of the Earth and verify the non-homogeneous distribution of matter density within the Earth. We also estimate the IceCube Upgrade sensitivity to measure the correlated densities of the Earth layers while incorporating constraints from the mass and moment of inertia of the Earth. Neutrino-based results would be independent and complementary to the seismic and gravitational measurements.
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All authors The IceCube Collaboration: R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, M. Shin, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, A. K. Upadhyay, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Earth and Planetary Astrophysics

Asteroid Disruption and Deflection Simulations for Multi-Modal Planetary Defense

Alexander N. Cohen, Philip Lubin, Darrel Robertson et al. (+7 more)

Planetary defense from asteroids via deflective means alone does not offer viable solutions in terminal scenarios where there is little warning time before impact. The PI method of planetary defense enables operation in terminal interdiction modes where there is little warning time prior to impact, but can also operate in the same extended time scale interdiction modes as made possible by traditional deflection techniques, which results in a versatile, multi-modal planetary defense capability. The method is also practical and cost-effective since it relies solely on launch vehicles and penetrator materials already available today, and thus presents itself as a logical and competitive option for planetary defense. As per the PI method, we investigate the effectiveness of rubble pile asteroid disruption and deflection via hypervelocity impacts with 10:1 aspect ratio cylindrical tungsten penetrators. We present the results of an ongoing simulation campaign dedicated to investigating the PI method, using the Lawrence Livermore National Laboratory (LLNL) arbitrary Lagrangian-Eulerian (ALE) hydrodynamics code ALE3D run with the High-End Computing Capability (HECC) at NASA Ames Research Center. We model heterogeneous rubble pile asteroids with a distribution of spherical boulders of varying initial yield strengths set within a weak binder material. We find that rubble pile asteroids of this type in the 20 - 100 meter-class can be effectively mitigated via 20 km/s impacts with 100 - 1000 kg penetrators via the coupling of the penetrator kinetic energy into the bulk material of the asteroid.
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All authors Alexander N. Cohen, Philip Lubin, Darrel Robertson, Mark Boslough, Sasha Egan, Brin Bailey, Angela M. Stickle, Elizabeth A. Silber, Peter Meinhold, Dharv Patel

Earth and Planetary Astrophysics

Effect of lunar rotation on antipodal ejecta deposition

Shigeru Wakita and Brandon C. Johnson

The Moon's crust exhibits strong magnetic anomalies that likely record ancient magnetic fields produced by a core dynamo. Lunar materials have low magnetic susceptibility, but impactor material with high susceptibility may record the Moon's ancient dynamo. Some magnetic anomalies are antipodal to lunar basins and it is hypothesized that the impact ejecta accumulates at the basin antipode and records the ancient lunar magnetic field. Previous impact simulations, which ignored the rotation of the Moon, support this hypothesis. Here, we reevaluate the deposition of antipodal ejecta by considering the rotation of the Moon. Assuming that the rotational period of the Moon is the same as the current day, we find that the rotation of the Moon does not strongly affect the deposition of the antipodal ejecta if impacts occur near the poles. In contrast, rotation has a considerable effect on antipodal deposits for impacts occurring near the equator. An eastward impact at a 45 degree incidence angle results in almost no antipodal ejecta, however, an eastward impact with a 30 degree incidence angle accumulates more antipodal ejecta than the non-rotating case. It is hard to determine the impactor's direction and location, for basins without an ellipsoidal shape and/or an asymmetric ejecta blanket. Nevertheless, our work demonstrates that care must be taken in interpreting the magnetic anomalies antipodal to lunar basins and that the effect of rotation should not be ignored.
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Earth and Planetary Astrophysics

The False Spin of an Exo-Venus

Stephen R. Kane

Direct imaging of terrestrial exoplanets will enable rotational and atmospheric characterization through time-resolved photometry and high-dispersion spectroscopy. However, the velocity field inferred from reflected light does not necessarily correspond to the rotation of the solid planet, but rather to the motion of the layer from which the photons emerge. Venus provides a crucial Solar System example of this ambiguity: the solid planet rotates slowly, whereas the cloud-level atmosphere exhibits superrotation with a period of only several days. Here we investigate the observational degeneracy between rapid planetary rotation and atmospheric superrotation. We construct a disk-integrated reflected-light velocity model that includes solid-body rotation, zonal winds, and phase-dependent illumination. We show that, for a single spectral tracer probing a narrow range of pressures, a zonal wind field whose latitude dependence is similar to solid-body rotation can exactly mimic the line profile of a rapidly rotating planet. The degeneracy can be broken by measuring the apparent rotational velocity as a function of wavelength or line formation pressure. For a Venus-like wind profile, the apparent period can vary from hundreds of days in the lower atmosphere to $\sim$4–5~days at the cloud deck. We estimate the resolving power and signal-to-noise ratio required to measure this vertical shear. The most robust diagnostic of atmospheric superrotation is not a single value of $v \sin i$, but an altitude-dependent “false spin” signature across multiple spectral tracers. These results have direct implications for interpreting rotational measurements of Venus-like worlds with the Habitable Worlds Observatory and complementary high-dispersion facilities.
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Earth and Planetary Astrophysics

Geometry of dust rings in protoplanetary disks: the case of LkCa 15

Yansong Qian and Yanqin Wu

Dust properties in proto-planetary disks shape the pathways for planet formation. Here, we present a method to measure these properties in moderately inclined dust rings. Our method exploits the simple geometric fact that, for such a ring, its ansae appear brighter because our line of sight traverses a longer path through the ring material, and appear broader because the minor axis are foreshortened by projection. The resultant patterns of apparent brightness and width can used to constrain three parameters: the intrinsic ring width, its vertical thickness and its optical depth. We apply this method to ALMA archival images of the LkCa 15 disk, in Bands 7, 6 and 3. We find that the optical depth of its main ring drops from 1.6 at 0.89mm to 0.4 at 3mm. Simultaneously, both the ring width and the ring height decrease from about two to one gas scale heights. Such wavelength-dependent morphology can only be explained by the presence of multiple grain populations. If we adopt a simple two-size model, we infer that the ring contains a massive population of small grains (size < 20 micron; total mass ~ 100 earth masses) that are broadly distributed, and a less massive population of large grains (size > 200 micron) that are more spatially concentrated. This large surplus of small grains is not predicted by models of dust coagulation, but it naturally explains the fluffy ring in LkCa 15, and possibly rings in other disks.
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Earth and Planetary Astrophysics

The Sonora Substellar Atmosphere Models. VII. Flame Skimmer: Cloud-free Atmospheric and Evolutionary Models for the Coldest Substellar Objects

James Mang, Yayaati Chachan, Caroline V. Morley et al. (+7 more)

JWST has provided unprecedented access to ultra-cool brown dwarfs and has pushed the boundaries of directly imaging temperate giant planets. As we continue to push toward detecting sub-Saturn and Neptune-like planets, it is crucial to develop atmospheric and evolutionary models that better capture the complexity and diversity of planetary atmospheres similar to the gas and ice giants in our Solar System. We present Sonora Flame Skimmer, the next suite of cloud-free 1D atmospheric and evolutionary models in chemical equilibrium and disequilibrium probing colder temperatures (down to 50 K), smaller objects (down to log(g) = 2), and a wide range of metallicities (10x sub-solar to 100x super-solar) and C/O ratios (solar to 2.5x solar). Beyond expanding the physical parameter space of previous Sonora models, we update the opacities and evolutionary model framework from Sonora Bobcat, as well as the chemical treatment of volatiles (H$_2$O, CH$_4$, NH$_3$) and carbon species such as CO$_2$ from Sonora Elf Owl. For the evolution of these substellar objects, we find that high-metallicity atmospheres lead to slower cooling compared to solar metallicity, while the strength of vertical mixing ($K_{\rm zz}$) has a negligible impact on the evolutionary tracks. At the highest metallicity explored here (100$\times$ solar), the deuterium-burning and hydrogen-burning minimum masses fall to 5.39 and 45.03 $M_{\rm J}$, respectively. All the models presented here, including the atmospheric structure, chemical profiles, spectra, synthetic photometry, and evolutionary models, are publicly available.
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All authors James Mang, Yayaati Chachan, Caroline V. Morley, Natasha E. Batalha, Nicholas F. Wogan, Sagnick Mukherjee, Jonathan J. Fortney, Mark S. Marley, Channon Visscher, Ehsan Gharib-Nezhad

Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

Atmospheric Light Pollution by Proposed Reflect Orbital Space Mirrors

Miroslav Kocifaj, Gáspár Bakos and František Kundracik

ReflectOrbital is planning to launch a $18\times18$\,m mirror in space at a $\sim$600\,km altitude to illuminate a $2.5$\,km radius circular patch on Earth. The pilot satellite, called EARENDIL-1, is a pathfinder for a constellation of $\sim$50,000 larger mirrors, each with $54\times54$\,m in diameter, with the explicit goal to provide space-borne illumination on Earth. We calculate the sky brightness caused by the Rayleigh scattering and aerosol scattering of the incoming beam from one such satellite and by the light reflected back by the illuminated patch, for various atmospheric properties and ground albedos under cloud-free conditions. We demonstrate that the light pollution caused by one of these satellites is very significant, altering the nighttime environment up to distances of $\sim$30\,kms. The results show that for an observer within the beam of a single 54\,m satellite, the mirror will appear as a $-16.7$\,mag point-like source, i.e.~about 4 magnitudes brighter than the full moon. The diffuse sky background will be similar to the dusk sky shortly after sunset; too bright to see even the brightest stars. From a distance of 14\,km, the glow from a single mirror will exceed the luminance of the full moon sky for majority of the sky. From a distance of 34\,km the sky will still appear brighter than the moon-lit sky in the direction of the beam. If 400 such mirrors illuminate the same patch simultaneously, the glow will be obvious from 80\,kms.
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Earth and Planetary Astrophysics · Cross-listed from astro-ph.IM

The Early Career Astrobiology Workforce Under Strain Survey Evidence from 2025-2026

Katherine Dzurilla, Gabby Rizzo, Perianne Johnson et al. (+3 more)

A survey of self identified early career astrobiologists was organized by the NOW early career group FLOW and the Scientific Society of Astrobiology. During November 2025 to February 2026, 165 responses were collected to gain insight into the state of early career communities the impacts of federal grant delays on early career astrobiologists and the future of astrobiology. Results indicated that a majority of surveyed ECRs are concerned about their future careers (90 percent). Funding delays have affected 89 percent of ECRs future career paths, with open responses indicating that the lack of available funding resources, and employment opportunities limit their ability to see a future in the field. Most ECRs are unsure about staying in academia with over 50 percent of Ph.D. students, postdocs, and Junior scientists unsure or not planning to stay in academia. However Junior Faculty are largely planning to remain in academia.
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All authors Katherine Dzurilla, Gabby Rizzo, Perianne Johnson, Patrick Monreal, Ilankuzhali Elavarasan, Elizabeth Spiers

Earth and Planetary Astrophysics

A Streamer Driving Misalignment in the Circumtriple Disk of GW Ori

Maria Galloway-Sprietsma, Jaehan Bae, Toni Phillips et al. (+5 more)

GW Orionis is a triple stellar system with a disk featuring three misaligned dust rings. We present ALMA molecular line data of CO isotopologues, revealing a streamer feeding the disk in $^{12}$CO and $^{13}$CO. Through multi-pointing observations, we find the streamer extends to $\sim30''$ on-sky ($\sim12,000$~AU) and estimate a mass of 1.6 M$_{\rm Jup}$ using $^{13}$CO. Fitting the morphology and kinematics of the streamer, we estimate the mass infall timescale of 0.04 Myrs and a mass infall rate of $3.6\times10^{-8}$~M$_{\odot}$~yr$^{-1}$, approximately an order of magnitude lower than the stellar accretion rate. Our best-fit trajectory shows that the streamer meets the disk at the outermost dust ring and that the streamer's angular momentum vector is closely aligned with this outermost ring within $\approx3^\circ$, in contrast to the $\approx32^\circ$ misalignment with the innermost ring, suggesting the streamer is the likely cause of the misalignment. However, the total angular momentum of the streamer is smaller than that of GW Ori's disk; this, together with the low accretion rate, indicates that we are probably witnessing the end stages of infall. Total Power observations reveal bright emission connecting the streamer to the surrounding star-forming region, with a projected distance falling well within the Bondi-Hoyle radius, implying the streamer could have originated through Bondi-Hoyle accretion as GW Ori moves through its natal cloud. Together, these results suggest that GW Ori remains dynamically linked to its parental cloud through ongoing accretion, with the streamer serving as the likely driver of its misaligned disk structure.
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All authors Maria Galloway-Sprietsma, Jaehan Bae, Toni Phillips, Jane Huang, Myriam Benisty, Matthew Porter, Christian Ginski, Andrew Winter

Earth and Planetary Astrophysics

Veiled in Starlight: Impacts of Stellar Contamination on Retrievals of TRAPPIST-1f's Atmospheric Composition

Harper Rosenthal, Lisa Kaltenegger, Ryan J. MacDonald et al. (+2 more)

The TRAPPIST-1 system offers seven terrestrial exoplanets with tight orbits and large radii ratios to the host star. If an atmosphere exists, transmission spectroscopy can be used to detect specific atmospheric features. Predictions of the atmospheric detectability of the TRAPPIST-1 planets prior to the launch of JWST assumed pristine stellar surfaces. However, initial JWST observations of the TRAPPIST-1 planets demonstrate that stellar contamination from unocculted active regions imparts significantly stronger spectral features than any planetary atmospheres. Here, we evaluate the atmospheric detectability of the habitable zone planet TRAPPIST-1f using atmospheric retrievals accounting for stellar contamination. We model a transmission spectrum given a CO$_2$-rich, habitable atmospheric model, and we include a "worst case" stellar contamination spectrum. We then perform atmospheric retrievals on simulated JWST observations with MIRI LRS (5-15 \micron) and NIRSpec PRISM (0.6-5.3 \micron), assuming accurate starspot spectral models. We find that NIRSpec observations alone achieve similar results as MIRI and NIRSpec together. We find $\sim$10 transits obtains strong evidence ($B>150$) for CO$_2$, and $\sim$50 transits finds weak evidence ($B>3$) for CH$_4$. We could not retrieve evidence of H$_2$O with up to 100 simulated transits with both instruments. Many challenges remain to accurately account for stellar contamination for ultra-cool M-dwarfs in atmospheric retrievals, and our results show that, while evidence for a CO$_2$-rich atmosphere around TRAPPIST-1f can be found with a short JWST program, other prominent atmospheric signatures can only be disentangled from strong stellar features with more observation time than previous studies have indicated.
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All authors Harper Rosenthal, Lisa Kaltenegger, Ryan J. MacDonald, Rebecca Payne, Elijah Mullens

Earth and Planetary Astrophysics

The Lunar Polar Icy Regolith and Possible Moonflows

Nick Gorkavyi, Oreste Reale and Harrison Schmitt

The Lunar CRater Observation and Sensing Satellite (LCROSS) experiment, which created a crater 27 meters in size, showed that up to 6 percent water appear to be present in the permanently shadowed region (PSR) of Cabeus crater. Past independent theoretical analyses have concluded that some water molecules released elsewhere on the lunar surface can migrate to permanently shadowed areas. The estimated amount of ice, ice fragments, and other volatiles located in the polar regions in and beneath the regolith at depths of several meters may be still affected by significant uncertainties. Data from the Kaguya mission provide strong evidence for active plumes of water vapor erupting from polar regions outside the PSRs to heights of several km. These plumes appear to originate from subsurface ice located beneath the regolith surface at depths of approximately 20 cm. On the other hand, the polar highlands exhibit a relative deficit of craters larger than 25 meters, which may be caused by impact-melted ice lubricating regolith that flowed into initial crater depressions. At both the north and south poles of the Moon, signs of possible short-lived flows of liquid water-bearing material "moonflows" are presented in this work. Limited hydrous alteration of regolith ultra-fines to phyllosilicates may have occurred as these moonflows cooled.
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Earth and Planetary Astrophysics · Cross-listed from physics.flu-dyn

Magnetic Dynamo Driven by Inertial Waves

A. Mishra, G. Mamatsashvili, M. Le Bars et al. (+2 more)

We demonstrate, by studying precession-driven flows, that inertial wave hydrodynamic turbulence can drive a robust magnetic dynamo action. Motivated by the stronger damping of large-scale geostrophic vortices in rapidly rotating planetary and stellar interiors, we introduce a controlled damping of the vortices, which usually accompany inertial wave turbulence and feed on wave energy. It is shown that even a small vortex damping results in a significant increase of the growth rate of the dynamo due to inertial waves in the kinematic regime, allowing it to persist for magnetic Prandtl numbers as low as $Pm \sim 10^{-3}$ and Poincaré numbers $Po\sim 0.025$. These critical values of $Po$ and $Pm$ for the dynamo onset decrease with increasing Reynolds number. The onset and growth of the dynamo appear to correlate with the coherent fluctuations of kinetic helicity. Spectral analysis shows that magnetic energy growth is primarily due to inertial-wave-induced induction over a broad range of scales. These results establish inertial waves as an efficient mechanism for magnetic field amplification in rapidly rotating low-$Pm$ flows relevant to planetary and stellar interiors.
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All authors A. Mishra, G. Mamatsashvili, M. Le Bars, A. J. Barker, F. Stefani

Earth and Planetary Astrophysics

The SPACE Program II: No discernible spectral features in the transmission spectrum of the sub-Neptune HD 191939 b observed with HST/WFC3

Cyril Gapp, Lorena Acuña-Aguirre, Reza Ashtari et al. (+17 more)

The atmospheres of sub-Neptunes provide a window into their internal structure and history, shedding light on the origin of this common, but enigmatic, class of exoplanets. However, the physical and chemical processes that shape sub-Neptunes' transmission spectra, in particular cloud and haze formation, are not well understood. To identify possible correlations between transmission spectra and UV irradiation, the SPACE (Sub-neptune Planetary Atmosphere Characterization Experiment) Program observed an array of sub-Neptunes and their host stars using the Hubble Space Telescope (HST), measuring the planets' transmission spectra between $1.1\,\mu$m and $1.7\,\mu$m with the Wide Field Camera 3 (WFC3) and the stars' UV spectra with the Space Telescope Imaging Spectrograph (STIS). Here, we present the observations of HD 191939 b carried out as part of the SPACE Program, which reveal no significant spectral features in the transmission spectrum. The data deliver moderate evidence at significance levels between $2.0\,\sigma$ and $3.2\,\sigma$ against a cloud-free atmosphere with solar metallicity, rendering this scenario unlikely, but still possible. A super-solar metallicity of HD 191939 b might be consistent with the known trend of increasing atmospheric metallicity with decreasing planet mass. Both hydrocarbon haze formation and cloud condensation can be efficient at HD 191939 b's zero-albedo equilibrium temperature of $(880\pm 20)\,$K, particularly in atmospheres with super-solar metallicity, possibly additionally muting absorption features.
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All authors Cyril Gapp, Lorena Acuña-Aguirre, Reza Ashtari, Mario Damiano, Thomas M. Evans-Soma, David J. Wilson, Kevin France, Laura Kreidberg, Drake Deming, Qiushi Chris Tian, Seth Redfield, Ian J.M. Crossfield, K. Angelique Kahle, Tansu Daylan, Kevin Heng, Bertram Bitsch, James S. Jenkins, Keivan G. Stassun, Antonio García Muñoz, Ludmila Carone

Earth and Planetary Astrophysics

Exploration of Exoplanet Atmospheres with the James Webb Space Telescope

Sasha Hinkley and David K. Sing

The James Webb Space Telescope (JWST) is providing transformative characterization capabilities for the study of both transiting and directly imaged extrasolar planets. Observations deep into the infrared in the form of both spectroscopy and coronagraphic imaging means that JWST is uniquely sensitive to most of the physical processes that dictate the properties of exoplanetary atmospheres. The observatory's thermal and pointing stability directly translates into the extreme photometric precision needed for exquisite transiting exoplanet photometry, as well as highly sensitive coronagraphic observations. Over the mission's 20-25 year lifetime, roughly 10$^4$ hours will be dedicated to observations of exoplanet atmospheres, providing a legacy data archive that will allow population-level characterization of exoplanet atmospheres spanning terrestrial planets, sub-Neptunes and gas giants. This effort will also assess the prevalence of atmospheres of rocky planets and thus the degree to which such planets may have conditions conducive to habitability.
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2608.05885 · 6 Aug · Review article for Contemporary Physics (in press) on JWST's characterization of exoplanets. 48 pages, 11 figures, 350 references. This article may be especially useful for researchers new to JWST, especially the tables listing transiting and directly imaged exoplanets observed so far with JWST. Updated with a few additional references and to address some community feedback. Comments welcome

Abstract PDF $EXOP ×4$PLNT ×4$TSCP ×2

Earth and Planetary Astrophysics

Dust transport in envelopes of disk-embedded planets: II. Fully convective envelopes

Ayumu Kuwahara and Michiel Lambrechts

We perform 3D multifluid simulations of gas and dust to quantify how convection reshapes the spatial distribution of dust grains inside the envelopes of disk-embedded planets. Building on the first paper of this series, which explored convectively stable envelopes, we here consider envelopes in which convection is sustained by the accretion luminosity. The dust-to-gas ratio inside the planetary envelope is set primarily by the degree of dynamical isolation from the surrounding disk. When convection extends beyond the Bondi radius, the envelope remains connected to the disk flow and maintains a dust-rich state through continuous material exchange. Conversely, when an inner convective layer is separated from an outer recycling layer, the recycling flow filters incoming solids. The dust distribution inside the convective layer is then controlled by the competition between convective stirring and gravitational settling. This yields two regimes: a settling-dominated regime, in which large grains (typically $s\gtrsim0.1$ cm) fall at the terminal velocity and the envelope becomes dust depleted, and a convection-dominated regime, in which smaller grains are trapped in convective circulation and the envelope retains its dust. The delivery and release of volatile species from accreting solids at the envelope sublimation front, together with the efficiency of convective mixing, determine how this material is distributed between the core and envelope. Our findings imply that super-Earths and mini-Neptunes inside the water snowline have volatile-depleted cores and volatile-rich envelopes, while planets at wider orbits can have a wide diversity of envelope compositions from depleted to enriched. This compositional diversity for planetary envelopes appears to be consistent with the large diversity in observed atmospheric compositions of mini-Neptunes.
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Earth and Planetary Astrophysics

Dust transport in envelopes of disk-embedded planets: I. Convectively stable envelopes

Ayumu Kuwahara and Michiel Lambrechts

Planets embedded in protoplanetary disks accrete solids through their gaseous envelopes. The spatial distribution of these dust particles inside the envelopes of disk-embedded planets is poorly known. We present high-resolution two- and three-dimensional multifluid simulations that follow the dynamics of gas and dust around planets similar in mass to Earth. Our simulations resolve an outer recycling flow and an inner convectively stable envelope that is shielded from the recycling flow. We identify strongly dust-depleted envelopes: the dust-to-gas ratio decreases radially inward and is reduced by more than two to four orders of magnitude in the deep interior ($<0.1\,R_{\rm B}$; Bondi radius) compared to its value at the outer edge of the envelope. Small grains, with a dimensionless stopping time ${\rm St}\lesssim10^{-3}$, remain entrained in the recycling flow and do not enter the envelope, whereas large grains (${\rm St}\gtrsim10^{-2}$) penetrate the envelope but settle rapidly onto the core along the midplane. The resulting dust depletion in convectively-stable envelopes implies a substantial reduction in dust opacity throughout much of the envelope, facilitating cooling and a more rapid transition to runaway gas accretion. These results further suggest that enriching the deep envelope ($<0.1\,R_{\rm B}$) with dust or volatiles requires their delivery through large pebbles that then subsequently disintegrate, or sublimate, from their host grains in the deep envelope interior.
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Earth and Planetary Astrophysics

Beyond Point Masses. VI. Spin-Orbit Evolution of the Centaur Binary Typhon-Echidna

Benjamin Proudfoot, Will Grundy and Darin Ragozzine

Only three binaries have been identified among the Centaur population. Because their perihelia are significantly closer than those of other trans-Neptunian binaries (TNBs), these systems allow a detailed look at tight binaries in the broader TNO population and provide critical insight into the disruption of binaries as they enter the Centaur population. Using recent and archival Hubble Space Telescope (HST) observations, along with Keck data, we present a spin-orbit study of Typhon-Echidna. We find that the binary's mutual orbit is inconsistent with a Keplerian orbit; more detailed non-Keplerian fits show that the mutual orbit is rapidly precessing. We measure Typhon's dynamical oblateness, $J_2$, at $\sim10\sigma$ confidence and find that Typhon's rotation pole is $\gtrsim20^\circ$ misaligned with the binary's mutual orbit. Assuming Typhon has a triaxial shape, our results, combined with rotational light curves and thermal measurements from the literature, suggest ellipsoidal semi-axes of $a=93^{+8}_{-6}$ km, $b=84^{+6}_{-6}$ km, and $c=65^{+9}_{-8}$ km. We further investigate the observational consequences of the complex spin-orbit dynamics, including light curve alteration by axial precession of Typhon and substantial changes to the system's mutual event season. Based on the system's dynamically excited state, we suggest a recent encounter with a giant planet may have substantially altered the system, potentially consistent with a binary in an early stage of disruption. This hypothesis can be tested with resolved photometric observations of the system. Our investigation highlights how non-Keplerian dynamics enhances our understanding of TNB systems and motivates ongoing observations of TNBs with astrometry, photometry, and stellar occultations.
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Earth and Planetary Astrophysics

The TASSIE Program. II: Three Close-In Companions Orbiting Sun-Like Stars

T. Plunkett, E. Thygesen, A. A. Cole et al. (+16 more)

We present three southern transiting giant planet candidates alerted by the Transiting Exoplanet Survey Satellite (TESS) mission and investigated at the University of Tasmania Greenhill Observatory (UTGO). The candidate planets are orbiting thin disk G-dwarf main-sequence stars with roughly solar metallicity, possessing orbital periods between 2.9 - 3.3 days and radii of 1.1 - 1.3 $R_{J}$. We performed ground-based follow-up photometry primarily with the UTGO Harlingten 50 cm, then gathered reconnaissance spectra, high angular resolution imaging and high-precision radial velocities to rule out false positive scenarios. We confirmed that two of these systems host true exoplanets and constrained their masses. TOI-3053b is a typical hot Jupiter, with $M_{3053b} = 0.85 \pm 0.12$ M$_{J}$ and a bulk density of $\rho_{3053b} = 0.64 \pm 0.10$ g cm$^{-3}$. TOI-3278b / HATS-78b is a hot Saturn-mass planet ($M_{3278b} = 0.30 \pm 0.07$ $M_{J}$) with a highly inflated atmosphere and a low density of $\rho_{3278b} = 0.21 \pm 0.05$ g cm$^{-3}$. The other candidate (TOI-3272.01) remains unconfirmed, but appears consistent with being a hot Jupiter. TOI-3272.01 is notable as a candidate planet orbiting a potentially young to intermediate age star, with a rotational analysis indicating an age estimate of $T_{3272} = 1.1 \pm 0.2$ Gyr. These systems add to a growing sample of hot giant planets from TESS that may provide constraints on the migration pathways and radius inflation of the broader close-in exoplanet population.
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All authors T. Plunkett, E. Thygesen, A. A. Cole, J. Schulte, J. E. Rodriguez, B. Emptage, J. P. Beaulieu, G. Bakos, J. Hartman, C. Ziegler, K. A. Collins, Z. Csubry, K. Penev, A. Jordán, R. Brahm, L. Mancini, T. Henning, D. J. Radford, P. Evans

Wednesday 5 August

Earth and Planetary Astrophysics

The forced orbital planes of the Plutinos and other resonant KBOs

Ian Matheson and Renu Malhotra

The forced plane of non-resonant minor planets has been understood to be well-estimated by the local Laplace plane given by linear Laplace-Lagrange secular perturbation theory, but there is no extant theory for the forced plane of resonant minor planets. With improved methodology, we revisit our previous measurement of the mean orbital plane of the observed Plutinos, a group of Kuiper belt objects locked in Neptune's 3:2 mean motion resonance. In the J2000 ecliptic-equinox reference frame, the measured mean plane has an inclination of 1.9 degrees and an ascending node at 46.8 degrees longitude, with a 95% confidence of 2 degrees in the plane position; it is well separated from the local Laplace plane but is indistinguishable from the solar system's invariable plane. We also show that, at high statistical confidence, the two dynamical subgroups, the doubly resonant Plutinos whose arguments of perihelion librate about +90 and -90 degrees, have different mean planes from each other. Additionally, we measure the mean planes of four other observed resonant groups in the Kuiper belt: the 5:3, 7:4, 2:1, and 5:2. Although these groups have substantial sample sizes (in the range 56-105), their mean planes are presently not statistically distinguishable from their local Laplace plane, Neptune's plane, and the invariable plane. For all five resonant groups, we also report the best-fit von Mises function for their inclinations. These empirical measurements underscore the need for theoretical analysis to understand the spatial dynamics of resonant populations of minor planets. Such analysis could potentially enable their use for uncovering unmodeled perturbations and/or undiscovered perturbers.
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Earth and Planetary Astrophysics

SMA 200-400 GHz Survey for 10 faint Class II Disks in the Taurus Molecular Cloud

Chia-Ying Chung, Hauyu Baobab Liu, Sean M. Andrews et al. (+3 more)

We have performed Submillimeter Array (SMA) observations of 198.0-407.5 GHz broadband spectra of 10 Class II protoplanetary disks in the Taurus-Auriga region. The 337 GHz flux densities ($F_{\rm 337 GHz}$) of these objects are in the range of 8.2-34 mJy. The median and standard deviation of the 198-358 GHz spectral indices ($\alpha_{198-358}$) of these 10 Class II disks are 1.9 and 0.3, respectively. Compared to the recent, similar SMA survey on another 47 Class II disks that are brighter at (sub)millimeter bands ($F_{\rm 337 GHz}\sim$20-730 mJy), there is no evidence that these newly observed 10 fainter Class II disks have systematically different $\alpha_{198-358}$ values. At $>$230 GHz frequencies, the optical depths of these 10 fainter Class II disks may be as high as those of the brighter sources, which may be $\gtrsim$5. In addition, the low ($<$2.0) values of $\alpha_{198-358}$ in some faint objects may be explained by the effect of dust self-scattering, with maximum dust grain size ($a_{\rm max}$) $\sim$ 100 $\mu$m, or by contamination by free-free emission.
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All authors Chia-Ying Chung, Hauyu Baobab Liu, Sean M. Andrews, Mark A. Gurwell, Melvyn Wright, Feng Long