Origins Seminar Series

Reliable detection of small long-period planets in Kepler data

January 12, 2026   |   12 pm noon (MST)   |   Hybrid (Steward N305 & zoom)

 Oryna Ivashtenko, Weizmann Institute of Science

ABSTRACT

The Kepler spacecraft provided unprecedented photometric precision, enabling the detection of Earth-like planets. However, the final Kepler catalog lacks sufficient reliability for small, long-period planets, complicating estimates of occurrence rates in this regime. A major source of this problem is the difficulty in distinguishing genuine but faint planetary signals from systematic false alarms—spurious detections caused by correlated, non-Gaussian noise.

We developed an independent search and vetting pipeline that addresses this noise structure using tailored statistical methods, providing a clean background distribution free from the false alarm tail. The pipeline was applied to the entire Kepler dataset, yielding a list of planetary candidates. For each candidate, we estimated its probability of being a real astrophysical periodic signal, using empirical per-target background estimation and injection-recovery campaign.

In this talk, I will explain the methodology behind this pipeline and present the planetary candidates that obtained a high probability of being real. I will demonstrate the pipeline reliability and its detection efficiency. Next, I will outline the future steps of the project and explain how these results will be used in the estimation of occurrence rates.

The formation and evolution of mature planetary systems

JANUARY 13, 2026   |   12 pm noon (MST)   |   hybrid (STEWARD N305 & zoom)

Joshua Lovell, harvard University

ABSTRACT

Planets and planetesimals form ubiquitously in extra-Solar planetary systems and are built from circumstellar material, present as leftover dust and gas from star-formation. The formation of these large planet/planetesimal bodies occurs primarily in gas-rich protoplanetary disks during the first few Myr of a star’s life, although many rocky planets must grow via constructive planetesimal collisions over 10s to 100s of Myr. Planetesimal collisions are also destructive, and produce dusty debris disks, structures that observable over Myr–Gyr timescales, evident by their presence around ~1 in every 4 main sequence stars. Planet-disk interactions can shape the morphologies of these debris disks dynamically, and give rise to distinct disk sub-structures dependent on planetary architectures and system-wide evolutionary processes. JWST, ALMA and other high angular resolution instruments are now resolving the morphologies and sub-structures of disks, and are thus providing critical data to understand how and where planets form, and how planetary systems evolve over their complete life cycles. Nevertheless, a number of core open questions remain: when do debris disks actually form, how early can we observe them, and with what substructures are they born? On what timescales do their substructures evolve, and under what conditions are planets uniquely responsible for these sub-structures? In this talk, I will outline my recent work in this area, including studies on the formation and evolution of planetesimal disks in nearby star forming regions, and high-resolution modelling studies to investigate how debris disk substructures are modified as these are warped by nearby planets.

Evolving Weather: Dynamics of Brown Dwarf Atmospheres Across Time

January 26, 2026   |   12 pm noon (MST)   |   Hybrid (Steward N305 & zoom)

Elena Manjavacas, Space Telescope Science Institute

ABSTRACT

More than three decades after their discovery, hundreds of brown dwarfs and planetary-mass objects have been monitored for photometric and spectroscopic variability showing in general some degree of rotational modulation—likely driven by patchy clouds, thermochemical instabilities, temperature contrasts, and localized hot spots in their atmospheres.

In this talk, I present a holistic analysis of all published brown dwarf light curves to date. By combining results across filters, surveys, and epochs, we explore how variability amplitudes and rotation periods depend on spectral type, age, and potential viewing angle, and how these signals evolve over time for objects observed in different epochs. This population-level study allows us to place individual variable brown dwarfs in a broader atmospheric and evolutionary context.

Finally, I will highlight how time-resolved JWST/NIRSpec spectroscopy is allowing us to deeper understand brown dwarf variability and its causes. These observations allow us to probe atmospheric structure in three dimensions, constraining the physical mechanisms behind the observed variability and revealing the cloud architectures operating at different depths within brown dwarf atmospheres.

Updates on Pandora: Launch, Commissioning, and Science

february 2, 2026   |   12 pm noon (MST)   |   hybrid (Kuiper 309 & zoom)

Daniel Apai, University of Arizona (Steward/Lunar & Planetary Laboratory)

Constraints on the Fomalhaut Main Belt Planetesimal Population from Observed Collisional Remnants

february 2, 2026   |   12 pm noon (MST)   |   hybrid (Kuiper 309 & zoom)

Arin Avsar, University of Arizona (Steward/Lunar & Planetary Laboratory)

Low mass binaries are bound from birth and other insights from simulations of star formation

february 9, 2026   |   12 pm noon (MST)   |   Hybrid (STEWARD N305 & zoom)

Aleksey Generozov, The University of Texas at Austin

ABSTRACT

Resolving the earliest stages of star and multiple formation is observationally challenging. I will show how detailed simulations of star forming regions can give insight into these processes. For example, I will discuss how multiple star systems form and evolve in simulations of star cluster formation representative of typical Milky Way conditions that include all key physics and stellar feedback mechanisms. In particular, I will show ~70-80% of binaries form as bound systems, rather than from capture of initially unbound stars.

Testing Twelve Beliefs on the Origin of Life

february 11, 2026   |   11 AM (MST)   |   hybrid (STEWARD N305 & zoom)

Dieter Braun, LMU Munich

ABSTRACT

The experimental lessons that we have learned in recent years are grouped along preconceptions in the field of the origin of life. Testing these preconceptions experimentally will advance the field and enable a simpler, more geologically compatible RNA world hypothesis. I would like to discuss experiments tackling the following preconceptions: • Life emerged in the liquid state • Activation is at the 5’ end of RNA • Life emerged at pH 7 • RNA is unstable and does not hybridize at high pH • Amino acids to not play an early role • RNA is only catalytic in the form of Ribozymes • Activated molecules are enough to drive the system • Life needs cells • Evolution needs continuous molecule synthesis • Early life required autotrophy • Molecules of Life are single sided • Origin of Life is slow.

Above experiments led us to a series of experiments that tested and allow to falsify a growing hypothesis on how life could have emerged. The outline of the hypothesis can be summarized as follows: The accumulation of polymerising molecules is exponentially amplified by various geological flow non-equilibria inside microscale porous rock matrices. The polymerisation of 2′,3′-cyclic nucleobases at a pH of 9–10 that is geologically common will form autocatalytic replication networks by ligation. These networks should grow and recycle in wet-dry cycles between day and night. Replication is faster when the RNA oligomers are pinned, fed, and selected for length and replication speed by local geological flows. RNA self-purifies by dry polymerization and wet templated ligation into both left- and right-handed homochiral strands. The right-handed strands are likely selected by evolution much later. The geological flow settings can localize and feed modern biochemistry without the need for cells, demonstrating a long-term habitat for evolution. At heated gas bubbles, the local molecule population can accumulate in the presence of lipids into giant vesicles, initially only for lateral gene transfer, but creating a continuous environment for the evolution of cells. Cells, like ships, could the spread life across oceans and deserts to fully populate early Earth.

Externally irradiated protoplanetary discs in high UV environments

february 16, 2026   |   12 pm noon (MST)   |   Hybrid (Kuiper 309 & zoom)

Tyger Peake, Queen Mary University of London

ABSTRACT

External photoevaporation of protoplanetary discs, by massive O stars in stellar clusters, is thought to be a significant process in the evolution of a disc. It has been shown to result in significant mass loss and disc truncation, ultimately reducing the disc lifetime, and possibly affecting potential planet populations. It is a well-studied process in the Orion Nebula Cluster (ONC) where the cometary morphology, giving them the name proplyds, is spatially resolvable due to its proximity to Earth. However, we need a technique to identify external photoevaporation in distant massive clusters, which are more representative of the typical stellar environment, and where proplyds are spatially unresolvable.
The first part of this talk will be on a new technique of identifying regions of ongoing spatially unresolvable external photoevaporation using emission line ratios. While the second part is an interpretation of new JWST observations of potential proplyds in the more distant cluster Trumpler 14.

Gravitational collapse revisited

february 23, 2026   |   12 pm noon (MST)   |   hybrid (STEWARD N305 & zoom)

Enrique Vázquez-Semadeni, IRyA-UNAM Morelia

ABSTRACT

Classical Newtonian gravitational collapse is often envisioned as a spherical, homologous contraction that happens locally, all at once, and in isolation. However, this is an extremely unrealistic picture. Here I review the main features of realistic collapse: 1. Spherical collapse is non-homologous. This implies that the collapse does not occur at once, but rather develops a continuous accretion flow from low to high densities. 2. The collapse consists of a pre-singularity (prestellar) stage and a post-singularity (protostellar) one, each characterized by different density profiles and accretion regimes. 3. The prestellar stage occurs from the outside-in on scales smaller than the initial Jeans length. 4. At early times or large radii, the radial profile of the accretion rate depends on that of the density. The r^{-2} radial density profile is an attractor, and corresponds to a radius-independent accretion rate. Shallower density profiles imply an inwards-decreasing accretion rate, and therefore an increasing gas mass. We refer to this process as “gravitational choking”. 5. Non-spherical collapse amplifies anisotropies, and therefore generates a directional accretion flow, which produces a hierarchy of roundish, flattened and filamentary structures. Thus, filamentary accretion can be a signature of large-scale, gravity-driven accretion flow. 6. In the presence of initial turbulent density fluctuations, high-mass fluctuations of typical amplitude initiate their collapse earlier, but take longer times to conclude it than low-mass ones, so that the latter culminate their collapse first. This implies that, at early times, the small-scale regions in multi-center collapse flows appear super-virial, and later appear virialized.

Multi-Dimensional Gas+Dust Modeling of Protoplanetary Disks and Supply for Planet Formation

MARCH 2, 2026   |   12 pm noon (MST)   |   Hybrid (Steward N305 & zoom)

Hui Li, Los Alamos National Laboratory

ABSTRACT

Observations of protoplanetary disks (PPDs) and direct imaging of giant planets with spectra are providing increasingly strong constraints on the dust and gas properties in PPDs during planet formation. Meanwhile, large-scale numerical modeling of the joint dynamics of gas and dust in such disks has shown great progress over the past decade. In this talk, we will describe the new challenges emerging from observations and present the recent numerical studies in 3D global gas+dust two-fluid PPD simulations. We will use several examples to show how the interplay between disk global+local instabilities and the dust size evolution can impact the dust prosperities and distribution, both for interpreting observations, and ultimately, for understanding the planet formation.

A Tale of Two Ice-Giants: Ring-Moons as Tracers of the Formation and Divergent Evolution of the Uranian and Neptunian Satellite Systems

MARCH 16, 2026   |   12 pm noon (MST)   |   hybrid (KUIPER 309 & zoom)

Ryleigh Davis, Caltech

ABSTRACT

Can the smallest satellites in the outer Solar System record how entire planetary systems formed and evolved? Despite their similar sizes and locations, Uranus and Neptune host satellite systems with markedly different structures and evolutionary pathways. Their small ring-moons may represent the most direct surviving record of satellite formation in these systems. Yet, these moons orbit very close to their host planets making them difficult to observe and leaving their compositions—and therefore their origins—poorly constrained. Competing formation scenarios range from in situ accretion within circumplanetary disks to accretion from impact-generated debris following giant collisions with their host planet, tidal disruption of Kuiper belt objects, or catastrophic disruption and reassembly from earlier satellite generations. In this talk, I present the first near-infrared spectra of the Uranian and Neptunian ring-moons, obtained with JWST/NIRSpec (Program 4645), and explore what these observations reveal about the formation and evolution of the ice giant satellite systems.

Uranus’ ring-moons exhibit spectra consistent with water-ice-rich Kuiper belt objects, supporting models in which they formed from material largely decoupled from the planet—such as re-accretion from a tidally shredded KBO. In stark contrast, Neptune’s ring-moons display compositions unlike those of Uranus or any other small icy bodies observed to date. Despite minimal evidence for CO₂ or water ice, these moons exhibit a strong ~3 μm OH absorption and Larissa, Galatea, and the rings show an additional 2.72 μm band diagnostic of magnesium-rich phyllosilicates—minerals produced through extensive aqueous alteration and commonly associated with the interiors of differentiated planetesimals. These signatures suggest that Neptune’s present day ring-moons re-accreted from material originating deep within primordial satellites destroyed during Triton’s capture, providing rare observational access to the interior compositions of icy outer Solar System bodies. Together, these results reveal fundamentally different origins for the Uranian and Neptunian ring-moon systems and highlight how JWST spectroscopy of the smallest satellites can help illuminate the formation environments and subsequent evolution of the giant planet satellite systems.

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MARCH 23, 2026   |   12 pm noon (MST)   |   Hybrid (STEWARD N305 & zoom)

Rachel Bowens-Rubin, UMich

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MARCH 30, 2026   |   12 pm noon (MST)   |   hybrid (KUIPER 309 & zoom)

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april 6, 2026   |   12 pm noon (MST)   |   Hybrid (STEWARD N305 & zoom)

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APRIL 13, 2026   |   12 pm noon (MST)   |   hybrid (KUIPER 309 & zoom)

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april 20, 2026   |   12 pm noon (MST)   |   Hybrid (STEWARD N305 & zoom)

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APRIL 27, 2026   |   12 pm noon (MST)   |   hybrid (KUIPER 309 & zoom)

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MAY 4, 2026   |   12 pm noon (MST)   |   Hybrid (STEWARD N305 & zoom)

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MAY 11, 2026   |   12 pm noon (MST)   |   hybrid (KUIPER 309 & zoom)

Logan Pearce, UMich

ABSTRACT

Quantifying Habitability: A Terminology and Quantitative Framework for Solar System and Extraterrestrial Worlds

September 08, 2025   |   12 pm noon (MST)   |   Hybrid (Steward N305 & zoom)

 Daniel Apai, University of Arizona (Steward/Lunar & Planetary Laboratory)

ABSTRACT

The search for extraterrestrial life in the Solar System and beyond is a key science driver in astrobiology, planetary science, and astrophysics. A critical step is the identification and characterization of potential habitats, both to guide the search and to interpret its results. However, a well-accepted, self-consistent, flexible, and quantitative terminology and method of assessment of habitability is lacking.

I will report on a four year-long study and a framework developed by the NASA NExSS Quantitative Habitability Science Working Group. Through the work of this group, we developed the quantitative habitability assessment framework (QHF) that enables self-consistent, probabilistic assessment of habitability. We provide an open-source implementation and demonstrate that QHF can self-consistently inform astrobiology research over a very broad range of questions. I will show how QHF provides a basis for a uniform, quantitative assessment of habitability, a core concept that underpins the next decades of research in astrobiology and extrasolar planets. Finally, I will discuss how QHF can support the development of astrobiology missions and serve as a hub for multi-disciplinary collaborations.

Exploring self-consistent habitable Venus scenarios using a novel spin-climate evolution model

September 15, 2025   |   12 pm noon (MST)   |   hybrid (Kuiper 309 & zoom)

 Andrea Salazar, harvard University

ABSTRACT

Venus could have been habitable with surface liquid water for up to four billion years if it always had a slow rotation that promoted strong cloud cover. The slow, retrograde rotation of modern Venus is an equilibrium state of two opposing tidal torques: the gravitational and the atmospheric thermal tide. As the atmospheric tide depends strongly on the atmospheric state, past habitable periods would generate a different spin equilibrium from the state we observe today. The coupling between climate and rotation rate via the atmospheric thermal tide has not been considered in previous studies of Venus’s habitability history. Here we show using a coupled atmospheric tide and spin evolution model that the strong atmospheric thermal tide generated from a habitable atmosphere pushes the planet into a rapidly rotating regime. This terminates the habitable state rapidly, with a maximum duration of 700 million years if Venus’s initial rotation rate was slow and the habitable period began soon after formation. More recent habitable states are even shorter due to the brightening Sun. Only planets with initial rotation periods longer than 4 days reached a modern Venus spin state within the age of the Solar System, potentially necessitating a giant impact during Venus’s formation. This work suggests that if Venus had a habitable state, it was early in its history and short-lived. It also implies that Venus-like exoplanets around Sun-like stars are unlikely to be observed in a habitable state.

Discovery of the Halpha Protoplanet WISPIT 2b: Results of the Maxprotoplanet Survey for Protoplanets with MagAO-X

September 22, 2025   |   12 pm noon (MST)   |   Hybrid (Steward N305 & Zoom)

Laird Close, University of Arizona (Steward)

ABSTRACT

During this talk I’ll highlight how state-of-art visible wavelength ExAO can open new discovery space for protoplanets (exoplanets that are still accreting material). First the talk will focus on our recent discovery of the WISPIT 2b planet. Excellent (<25 mas) Ha images of the star TYC 5709-354-1 led to the discovery of a rare Ha protoplanet (Close et al. 2025b). This star was discovered by the WISPIT survey to have a large multi-ring transitional disk, and is hereafter WISPIT 2. Our Ha images of 2025, April 13 and April 16 discovered an accreting (Ha in emission) protoplanet: WISPIT 2b (r=309.43±1.56mas; (~54au deprojected) , PA=242.21±0.41o) likely clearing a dust-free gap between the two brightest dust rings in the transitional disk. Our SNR=12.5 detection gave an Ha ASDI contrast of (6.5±0.5)x10-4 and a Ha line flux of (1.29±0.28)x10-15 erg/s/cm2. We also present L’ photometry from LBT/LMIRcam of the planet (L’=15.30±0.05 mag) which, when coupled with an age of 5.1+2.4-1.3 Myr, yields a planet mass estimate of 5.3±1.0 Mjup from the DUSTY evolutionary models. WISPIT 2b is accreting at 2.25-0.17+3.75×10-12 Msun/yr. WISPIT 2b is very similar to the other Ha protoplanets in terms of mass, age, flux, and accretion rate. The inclination of the system (i=44o) is also, surprisingly, very similar to the other known Ha protoplanet systems which all cluster from 37≤i≤52o. We argue this clustering has only a ~1.0% (2.6s) probability of occurring randomly, and so we speculate that magnetospherical accretion might have a preferred inclination range (~37-52o) for the direct (cloud free, low extinction) line of sight to the Ha line formation/shock region. We also find at 110mas (~15au deprojected) a close companion candidate (CC1) which may be consistent with an inner dusty 9±4 Mjup planet. I will also talk about our discovery of variable accretion onto PDS 70 b and c as well (Close et al. 2025a).

Gravity or turbulence? Energy budget of molecular clouds

September 29, 2025   |   12 pm noon (MST)   |   Hybrid (Kuiper 309 & Zoom)

Javier Ballesteros-Paredes, IRyA – UNAM, México

ABSTRACT

In this talk I will discuss the pros and cons of the collapse and the turbulent model of molecular cloud dynamics and star formation, and what exactly the molecular clouds’ energy budget tells us; whether gravitational forces dominate over other sources of momentum, and what are the implications of the energy budget on the efficiency and rate of star formation. I will also show that the low values and the constancy of the “efficiency per free-fall time” arise naturally when clouds collapse. Our results imply that stellar feedback is the crucial ingredient to halt star formation, keeping the gas depletion time low on galactic levels. I will also show that the kinematic properties of young stars observed with Gaia are consistent with them being born from collapsing clouds rather than clouds supported by turbulence.

Missing TESS Objects of Interests Around Active M dwarfs

october 6, 2025   |   12 pm noon (MST)   |   hybrid (Steward N305 & Zoom)

Aylin Garcia Soto, Dartmouth College

ABSTRACT

The Kepler and TESS missions have revolutionized exoplanet discovery, with TESS expanding the discoveries around short orbital periods and M dwarfs. M dwarfs are small, cooler, redder than solar type stars and thus present the most favorable conditions for detecting transiting planets. However, their strong magnetic activity can mask planetary signals in both transits and transmission in the form of spots and flares. Several studies have worked to mitigate these effects by mapping their surface features based stellar signatures in spectroscopy and photometry. These stellar signatures also affect other studies, such as the derivation of stellar obliquities: the angle between a star’s spin axis and its planet’s orbital axis. This angle provides statistical insight into planetary system architectures and evolution. Mazeh et al. (2015) used Kepler photometric amplitudes to demonstrate that stars below 6000 K tend to have aligned systems, while hotter stars are more misaligned. However, they noted a selection bias for stars hotter than 6000 K, where higher activity in stars with larger amplitudes slightly altered the result. This bias was not accounted for in cooler M dwarfs. In this work, we revise the analysis of Mazeh et al. (2015) using data from Santos et al. (2019, 2021) and extend it down to 3000 K with TESS. We identify a similar selection bias in TESS data and explore its implications for quantifying potentially missing planets around active M dwarfs in the TOI lists.

Target Selection and Science Case Simulation for the Habitable Worlds Observatory

october 13, 2025   |   12 pm noon (MST)   |   Kuiper 309 & Zoom

 Noah Tuchow, University of Arizona (Steward)

ABSTRACT

NASA’s upcoming Habitable Worlds Observatory (HWO) aims to directly image Earth-sized planets in the habitable zones of Sun-like stars. Because of the extreme requirements for detecting exoEarths (planet-star contrasts of 10^-10 and angular separations on the order of 10-100 mas), only a limited sample of stars are suitable targets for a search for exoEarths. We constructed the HWO Preliminary Input Catalog of potential target stars for use in trade studies and yield calculations. As part of a large community effort to characterize HWO’s stellar targets, we developed a prioritization scheme for stars in our input catalog, identifying the population of stars that HWO is most likely to observe. We apply this input catalog to an example trade study, characterizing the ability of HWO to empirically constrain the boundaries of the habitable zone. Using the theoretical prediction that planets in the habitable zone will have lower albedos than those outside, we model the ability of HWO to recover trends in the underlying planetary albedo distribution. We calculate the required sample size and trend strength required to detect this relation with high confidence and determine that this science case is on the edge of feasibility with HWO.

Starless Core Evolution in the Barnard 10 Region of the Taurus Molecular Cloud

october 20, 2025   |   12 pm noon (MST)   |   Hybrid (Steward N305 & Zoom)

 Yancy Shirley, University of Arizona (Steward), Lucy Steffes, University of Arizona, & Hanga Andras-Letanovszky, University of Arizona

ABSTRACT

Starless and bound, collapsing prestellar cores are the earliest stage of star and planet formation where the initial physical and chemical conditions of the future protoplanetary disk are set. In this talk, we shall synthesize a series of projects to understand starless and prestellar core evolution by studying the complete core population of the Barnard 10 region (B10) of the Taurus Molecular Cloud. B10 contains a dozen starless cores that embedded within filamentary structure. With no embedded protostars, B10 is a pristine environment to study starless core evolution with minimal feedback from protostars. Using 3D radiative transfer modeling of (sub)millimeter continuum emission, we have constructed physical models of the cores. Mapping observations of the dense gas tracer NH3, analyzed with a new multi-velocity component Bayesian decomposition, probe the viral stability and kinematics of the filaments and cores. Using optically the thick tracers HCN and HCO+ 1-0, we search for signatures of core infall. We characterize the chemical evolution of the cores with surveys of deuteration (CH2DOH, HDCO, pD2CO, DNC, N2D+, NH2D, c-C3HD). By combining the information from these different surveys and comparing our results with MHD simulations of core evolution, we constrain their physical and chemical evolution, including evidence for differential evolution rates of the cores and the filaments within which they are embedded.

The Role of Protostellar Variability in Stellar Mass Assembly

october 27, 2025   |   12 pm noon (MST)   | Hybrid (steward 305 & Zoom)

 Greg Herczeg, KIAA, Peking University

ABSTRACT

Young stellar objects are notoriously variable. The largest amplitudes are seen on FU Ori objects, bursts of a factor of ~1000 in accretion rate that may last for centuries. However, the importance of such large bursts in stellar assembly remains uncertain. In this talk, I will discuss the role that variability plays at the different stages of evolution of young stellar objects and consequences for planet formation. I will highlight the JCMT Transient Program, the first dedicated sub-mm monitoring program, to measure the role of bursts in the earliest stages of stellar assembly, and discuss future prospects for protostellar monitoring.

Protoplanetary Disk Evolution in the ALMA–JWST Era

November 3, 2025   |   12 pm noon (MST)   | Hybrid (Steward N305 & Zoom)

 Ilaria Pascucci, University of Arizona (Lunar & Planetary Laboratory)

ABSTRACT

A key question in protoplanetary disk evolution is how disk gas sheds angular momentum to accrete onto the star. I will present results from the ALMA Large Program AGE-PRO showing that wind-driven accretion provides a better match to observed accretion rates and gas disk masses than traditional turbulent-driven models. I will also highlight new JWST/NIRSpec spectro–imaging that offers direct evidence for magneto-hydrodynamic disk winds capable of driving accretion. I will conclude by outlining upcoming work and discussing the broader implications of wind-driven accretion for planet formation and evolution.

Thermodynamic origins of primordial soups under asteroidal setting

November 10, 2025   |   12 pm noon (MST)   |   Hybrid (Kuiper 309 & Zoom)

Venkat Manga, University of Arizona (Lunar & Planetary Laboratory)

ABSTRACT

The OSIRIS-REx samples of Bennu with distinctive features of aqueous thermochemistry of small bodies and with significant abundances of amino acids, reignites an important question about the origins of primordial soups that synthesize building blocks of life. Furthermore, the unique mesoscale fabric of mineral assemblages in the samples demanded a thermodynamic setting, which is in odds with the existing asteroid geophysical model of carbonaceous type (e.g., mudball model). In this work, a hypothesized aqueous multiphase model that is developed to describe the thermochemical evolution of Bennu on its parent body also predicts a spontaneous formation of aqueous soups that are enriched in otherwise the dilute concentrations of elements of life. The mechanism of elemental partitioning within the immiscible fluid system towards the formation of primordial soup(s) under the asteroidal setting is discussed.

Investigating Star Formation through the End of the IMF and Stellar and Sub-stellar Multiplicity

November 17, 2025   |   12 pm noon (MST)   | Hybrid (Steward N305 & Zoom)

 Matthew De Furio, University of Texas at Austin

ABSTRACT

A successful theory of star formation should predict the number of objects as a function of their mass produced through star-forming events, as well as the frequency and properties of multiple systems. Previous studies in star-forming regions and the solar neighborhood have identified a mass function increasing in linear space down to 10 times the mass of Jupiter (MJ). Theory predicts a limit to the fragmentation process, the opacity limit, where a core becomes opaque to its own cooling radiation, providing a natural turnover in the mass function. Other studies of multiplicity in the Galactic field and stellar populations have shown that the frequency, mass ratios, and separations of multiple systems highly depend on primary mass with some indication of environmental effects. In this talk, I will present the first identification of a turnover in the initial mass function within a stellar population to date from deep JWST/NIRCam imaging in NGC 2024, a young star-forming region, suggesting the fundamental limit of turbulent fragmentation near 3 MJ. I will also explore the role of birth environment on the formation of multiple systems for brown dwarf to solar-type primaries through several ground and space-based surveys across varying stellar density from OB associations to a high density bound cluster. Lastly, I will detail my probe of multiplicity approaching the low-mass limit of turbulent fragmentation with JWST targeting the coldest brown dwarfs (Y-dwarfs, Teff < 500K) in the Galactic field.

Architectures of Exoplanetary Systems: A Multi-planet Model for Reproducing the Radius Valley and Intra-system Size Similarity of the Kepler Planets

November 24, 2025   |   12 pm noon (MST)   | hybrid (Kuiper 309 & Zoom)

 Matthias He, NASA Ames Research Center (ARC)

ABSTRACT

The single and multi-planet systems discovered by NASA’s Kepler mission provide crucial insights into the architectures and correlations within planetary systems, which in turn offer clues into their formation and evolution histories. The observed distribution of planet sizes from the Kepler planet catalog have revealed two distinct patterns: (1) a radius valley separating super-Earths and sub-Neptunes and (2) a preference for intra-system size similarity. I will present a new model for the exoplanet population observed by Kepler, which combines a multi-planet model in which the orbital architectures are set by the angular momentum deficit (AMD) stability with a joint mass-radius-period model involving envelope mass-loss driven by photo-evaporation. This “hybrid” model is capable of reproducing the observed radius valley given appropriate choices of the model parameters. The models that produce the deepest radius valleys have a primordial population of planets with initial radii peaking at ~2.1 Earth radii, which is subsequently sculpted by photo-evaporation into a bimodal distribution of final planet radii. I will show that the hybrid model requires strongly clustered initial planet masses in order to match the observed distributions of the size similarity metrics from Kepler’s multi-planet systems. Thus, the preference for correlated planet radii within the same system is well explained by a clustering in the primordial mass distribution. I will also show that the hybrid model naturally reproduces the “radius cliff” (the steep drop-off beyond ~2.5 Earth radii). This hybrid model is the first multi-planet model capable of simultaneously reproducing the observed radius valley and the intra-system size similarity patterns. Finally, I will discuss the model predictions for the occurrence rates of various types of planets, including Venus and Earth-sized analogs.

The Challenges of Detecting Gases in Exoplanet Atmospheres

November 24, 2025   |   3:30 pm noon (MST)   | hybrid (kuiper 312 & zoom)

This presentation will be held jointly with the Theoretical Astrophysics Program (TAP)

Peter McGill, Lawrence Livermore National Laboratory

ABSTRACT

The field of exoplanet characterization is now answering fundamental questions on planetary climate, composition, and formation, providing context for understanding our own solar system. The unprecedented precision and spectral resolution of the James Webb Space Telescope have allowed for the characterization of the atmospheres of planets ranging from ultrahot Jupiters, to lukewarm Neptunes, to terrestrial-sized and potentially habitable worlds, transitioning the field from being data-limited to model-limited. As a result, apparent detections of trace gases risk being artifacts of incomplete modeling rather than robust identification of atmospheric constituents, especially in the low signal-to-noise regime. I will illustrate these challenges using the sub-Neptune K2-18b, and challenge the recent, astonishing claims of a potential biosignature in its atmosphere.

Characterizing the Star-Disk-Cloud Connection in Classical T Tauri Stars

December 1, 2025   |   12 pm noon (MST)   | Hybrid (Steward N305 & Zoom)

 Caeley Pittman, Boston University

ABSTRACT

The innermost regions of classical T Tauri stars are shaped by the star-disk interaction through magnetospheric accretion. Accretion drives mass and angular momentum transport and generates high-energy emission that irradiates the surrounding disk. In this talk, I will present the largest and most self-consistent characterization to date of T Tauri star accretion structures and stellar rotation, performed as part of the international ODYSSEUS collaboration. I will highlight our unexpected results for magnetosphere sizes, star-disk spin equilibrium, and “dipper” system configurations, as well as discuss implications for ultra-short-period planet formation, angular momentum loss mechanisms, and disk irradiation. Finally, I will report our recent discovery that accretion structures are not uniformly distributed between different systems, but rather show 3D spatial correlations indicative of a star-cloud connection that persists over Myr timescales.

Planet Formation in the Line of Fire: The Fate of Disks in Massive Clusters

December 8, 2025   |   12 pm noon (MST)   | Hybrid (Kuiper 309 & Zoom)

 Ryan Boyden, University of Virginia

ABSTRACT

Planets form in protoplanetary disks around young stars, and the properties of emerging planetary systems depend intimately on the structure, composition, and evolution of their natal disks. With the commissioning of high angular resolution radio interferometers like ALMA and the VLA, we can now probe the bulk dust and gas reservoirs of disks that reside in the most common sites of star formation: massive stellar clusters. This talk will present an overview of key ALMA and VLA programs that have characterized the demographics of disks in the nearest star-forming clusters. I will highlight my team’s recent discovery of hydrogen and helium radio recombination lines from photoevaporating “proplyd” disks in the Orion Nebula Cluster. I will then present new VLA observations revealing widespread disk photoevaporation in NGC 1977 and NGC 2024. Finally, I will conclude with a discussion on how JWST is transforming our understanding of planet formation in clustered star-forming environments. I will share recent MIRI/MRS observations from my Cycle 3 JWST program targeting planet-forming disks in NGC 1977, with an outlook towards upcoming Cycle 4 JWST observations of the Orion proplyds.

Precursor Prebiotic Chemistry at the Earliest Stage of Sun-like Star Formation

December 10, 2025   |   12 pm noon (MST)   | Hybrid (Steward N305 & Zoom)

Samantha Scibelli, National Radio Astronomy Observatory (NRAO)

ABSTRACT

Before low-mass (M ≤ few solar masses) stars like our Sun are born, they are conceived inside cold (~10 K) and dense (> 10^4 cm^-3) cocoons of gas and dust known as starless or dynamically evolved prestellar cores. These objects are budding chemical laboratories that set the initial conditions important for understanding the later stages in their evolution, i.e., protostars, protoplanetary disks, and comets. In this talk, I will discuss what we know about the increasing chemical complexity found in this early stage, specifically those interstellar molecules that are precursors to more biologically relevant species such as amino acids, DNA, and RNA. Observational results from my large (> 60 object) surveys with single-dish submillimeter radio observing facilities (ARO 12m, Yebes 40m, and IRAM 30m), reveal that gas-phase precursor prebiotic chemistry in starless and prestellar cores is more widespread than previously thought. And, early results from my new observing programs (with the GBT 100m and ALMA Band 1) probe deeper, at finer kinematic and spatial scales, to map for the first time the precise locations of these precursor prebiotic species in and around prestellar cores. These programs, along with complementary ice measurements from JWST, ongoing chemical modeling efforts and laboratory studies, are necessary for us to trace how this chemistry, which is important for life on Earth, might be incorporated into the next stages of star and planet formation.