Origins Seminar Series

Origins Seminar series

The Origins Seminar series aims to bring together ISM, star and planet formation people, exoplanets experts, planetary scientists and astrobiologists including topics from molecular clouds through star and planet formation to exoplanets detection and characterization and astrobiology.

The seminar series is organized by Serena Kim (SO), Sebastiaan Haffert (SO), Sarah Moran (LPL), Allison Towner (SO), and Shuo Kong (SO) from Steward Observatory(SO)/Dept. of Astronomy and Dept. of Planetary Sciences (LPL) at the University of Arizona. The Origins Seminar series is partly supported by the Earths in Other Solar Systems NExSS team.

During regular semesters, talks are generally from 12pm – 1:00pm (MST) on Mondays. 12PM Arizona Time (MST) = 12pm PDT = 3pm EDT = 7pm UTC. If you want to receive weekly updates and advertisements for talks, please subscribe to the mailing list (click this link).  If you are interested in presenting your work during one of the open slots (see below), feel free to contact the organizers: serena00 at arizona.edu, shaffert at arizona.edu, sarahemoran at arizona.edu, towner at arizona.edu.  

The Origins seminar meeting is given in Hybrid format (in-person and via zoom). The Zoom information is sent via email, and the Origins seminar talks are recorded. The talk videos can be viewed from the Origins youtube channel.  Please subscribe to the mailing list to receive announcement emails about the Origins seminar talks.  

Visit the Origins Seminars YouTube Channel to watch past talks!

2024 – spring 

Recent Results on Inner Disk Chemistry from the JDISCS Team

january 22, 2024   |   12 pm noon (MST)   |   Hybrid (Kuiper 309 & Zoom)
 Colette salyk,   vassar college
ABSTRACT
While the solar system provides us some information about how planetary characteristics depend on distance from the sun, many other dimensions of planet formation remain to be understood. The many dimensions of planet formation are beginning to be explored with JWST, especially using MIRI-MRS, which provides chemical information from planet-forming environments on few AU scales.  I will highlight recent results using MIRI-MRS from the JWST Disks Infrared Spectral Chemistry Survey (JDISCS) Team including: greatly improved calibration of MIRI-MRS spectra and the beautiful spectra it produces, evidence for icy pebble drift, and investigations into how stellar mass affects chemistry.  I’ll also provide a few glimpses of work in progress, and discuss how our field as a whole is moving towards probing the multiple dimensions of planet formation in future years.

Short informal talks

january 29, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Yancy shirley, shuo kong, dominia itrich, mathew murphy, kevin hardegree-ullman, serena kim

Unveiling the asymmetry of the lagrange points

february 5, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 augustín Alejandro heron rivas,   Pontificia Universidad Católica de Chile
ABSTRACT

In celestial mechanics, Lagrange points appear naturally in the context of the well-studied Restricted Three-Body Problem (RTBP). In particular, they are gravitational equilibrium points where the influences of two massive objects create stable regions in space. Among these points, L4 and L5, located at the vertices of equilateral triangles formed by the primary and secondary masses, have been of particular interest. These correspond to the stable Lagrange points that are expected to trap the same amount of material in their co-orbital positions in the context of planetary systems. However, both recent observations and numerical simulations have revealed a striking asymmetry between the material surrounding L4 and L5. Therefore, the goal of this talk is to present some of the physical mechanisms responsible for these interesting features. By understanding this asymmetric phenomenon, we will be able to reveal some of the key features within protoplanetary disks. For example, we could infer the presence of planets, how migration affects the evolution of planets, or the thermodynamic properties of the disk. Furthermore, these processes will be characterized by both N-body and high-resolution hydrodynamical simulations.

Substructures in protoplanetary disk imprinted by multiple-planets and the case of HD 163296: The importance of multiple dust species in hydrodynamics

 

february 12, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 juan garrido-deutelmoser,   steward observatory

ABSTRACT

The Atacama Large Millimeter Array observations of the disk around HD 163296 have resolved a crescent-shape substructure at around 55 au. We propose that both the crescent and the dust rings are caused by a compact pair (period ratio ≃4:3) of sub-Saturn-mass planets inside the gap, with the crescent corresponding to dust trapped at the L5 Lagrange point of the outer planet. This interpretation also reproduces well the gap in the gas recently measured from the CO observations, which is shallower than what is expected in a model where the gap is carved by a single planet. The global model of the disk with four planets may fall into a long resonant chain, with the outer three planets in a 1:2:4 Laplace resonance. This configuration is not only an expected outcome from disk-planet interaction in this system, but it can also help constrain the radial and angular position of the planet candidates using three-body resonances. This numerical simulation includes the evolution of multiple dust species, and we highlight its importance presenting MDIRK: a Multifluid second-order Diagonally-Implicit Runge-Kutta method to study momentum transfer between gas and an arbitrary number (N) of dust species. In particular, admits a simple analytical solution that can be evaluated with O(N) operations, instead of standard matrix inversion, which is O(N)3. Therefore, the analytical solution significantly reduces the computational cost of the multifluid method, making it suitable for studying the dynamics of systems with particle-size distributions.  The simplicity of MDIRK lays the groundwork to build fast high-order asymptotically stable multifluid methods.

Demystifying the Sub-Neptune Frontier with JWST

february 19, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 anjali piette,   carnegie INstitution for science
ABSTRACT
The most common type of exoplanet detected to date lies between the sizes of Earth and Neptune – but with no solar system analogue, these ‘sub-Neptunes’ remain mysterious. Their masses and radii can be explained by a range of structures, including rocky interiors with hydrogen-rich atmospheres, water-rich magma oceans, and thick hydrospheres. Sub-Neptunes therefore provide an excellent opportunity to constrain new regimes of planetary science, and the James Webb Space Telescope (JWST) in particular is already beginning to provide new insights into these exotic planets. In this talk, I will discuss different ways in which JWST can constrain the properties of sub-Neptunes. For example, ‘lava worlds’ with dayside temperatures exceeding ~2000 K are expected to have atmospheres consisting of evaporated surface material. I will show that atmospheric observations with JWST have the power to constrain the chemical composition of this material, and discuss upcoming observations which will search for these chemical signatures. Meanwhile, JWST has already observed larger sub-Neptunes such as the hazy planet GJ 1214 b. I will discuss new constraints which we have placed on the atmospheric properties of this planet, paving the way for future studies of the sub-Neptune regime. Both current and future observatories will continue to uncover the diversity of planetary physics occurring in these enigmatic, yet common, exoplanets.

Illuminating protoplanetary disk sub-structure and their effects on exoplanets

february 26, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 taylor kutra,   lowell observatory
ABSTRACT

Of all the areas of astrophysics, the scales involved in forming planets span the most orders of magnitude. Everything from sub-micron sized dust grains that are responsible for passively heating a protoplanetary disk, to centimeter sized pebbles which accrete to form planets, or stellar companions with separations of tens of AU, can effect the planets that eventually form. In this talk, I will describe physical processes which act on all three of these scales and describe the implications for planet formation. This includes a novel steady state for irradiated protoplanetary disks with long lived pressure bumps which may a range of implications for disk evolution and planet formation.

Discovery of a spatially resolved disk wind and mid-IR variability: T Cha caught at the end of its evolution by JWST

march 04, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 naman bajaj (LPL ,U Arizona), andrew Sellek (Leiden observatory), chengyan xie (LPL, U Arizona)
ABSTRACT

Circumstellar disk dispersal is a brief, yet critical, end stage of disk evolution, dictating the end of planet formation and migration. Thermal winds powered by high-energy stellar photons have long been theorized to drive disk dispersal. However, evidence for these winds is currently based only on small (~3-6 km/s) blue-shifts in [Ne II] 12.81 um lines, which does not exclude MHD winds. We report JWST MIRI MRS spectro-imaging of T Cha, a disk with a large dust gap (~20 au in radius) and known blue-shifted [Ne II] emission. We detect four forbidden noble gas lines, [Ar II], [Ar III], [Ne II], and [Ne III], of which [Ar III] is the first detection in any protoplanetary disk. After performing continuum and PSF subtraction, we discover a spatial extension in the [Ne II] emission off the disk continuum emission, consistent with a disk wind. In contrast, we also find compact [Ar II] emission. – Naman Bajaj

We then show how by applying photoionization radiation transfer to simple hydrodynamic wind models we can predict the extent and luminosity of the Ne and Ar line emissions. Along with the low degree of ionization implied by the line ratios, we find that the relative compactness of [Ar II] compared to [Ne II] implies a dense wind such that soft X-rays and EUV only reach the inner parts of the wind while harder X-rays ionize the wind to larger radii. This requires high mass-loss rates (~10^-8 Msun/yr) and small wind launch radii (~1 au), that are consistent with the properties of X-ray-driven photoevaporation. – Andrew Sellek

We also have an unexpected discovery that the JWST continuum of T Cha is significantly different from the Spitzer data (up to 3 times lower in shorter wavelengths and 3 times higher in longer wavelengths) despite only ~17 years separating the observations. This change is highly likely to be non-periodic and can be caused by the asymmetric inner disk of T Cha that has significantly decreased in mass over human timescale. In combination with the observed disk dispersal, this inner disk evolution suggests that we might be witnessing the last stage T Cha’s disk evolution. – Chengyan Xie

Thermal Properties of the Hot Core Population in Sagittarius B2 Deep South 

march 11, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 Desmond Jeff,   university of Florida
ABSTRACT

Hot molecular cores are thought to represent a key phase of protostellar evolution and the evolution of the ISM, as the antecedents to ultra-compact HII regions and formation sites of complex organic molecules. However, owing to the complex interplay between gas-phase and grain-surface chemistry in pre and protostellar cores, the temporal and physical evolution of hot cores is still not well understood. The evolution of hot cores is further unexplored in the Milky Way’s Central Molecular Zone (CMZ) where, owing to the CMZ’s peculiarly low star formation rate, there are few examples of ongoing star formation. We report the discovery of 9 new hot molecular cores in the Deep South region of Sagittarius B2 (Sgr B2) using ALMA Band 6 observations. LTE modeling of methanol (CH3OH) lines reveals the cores’ resolved temperature and column density structure, which we use to derive the structural properties of the cores. We further perform comparisons of these properties to a sample of hot cores elsewhere in Sgr B2 and in the Galactic disk, providing hints on the relative onset of star formation in different regions of Sgr B2, new formation pathways for CH3OH in warm (> 250 K) ISM conditions, and the impact of the CMZ’s environment on massive star formation.

from the data to knowledge: a detailed investigation of recent findings of wasp-39b using jwst ers era

march 18, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 anna lüber,   Ludwig Maximilian University (LMU) University of Bern
ABSTRACT

The era of JWST transmission spectroscopy of exoplanetary atmospheres commenced with studying the Saturn-mass gas giant WASP-39b as part of the Early Release Science (ERS) program. WASP-39b was observed using four individual JWST instrument modes (NIRCam, NIRISS, NIRSpec G395H, and NIRSpec PRISM), with the resulting spectra detailed in a series of publications by the ERS team. In this presentation, we delve into assessing the information content of these spectra measured using the different instrument modes, focusing on the complexity of the temperature-pressure and chemical abundance profiles warranted by the data. We examine the detectability of molecules in each mode and discuss the fidelity of the results obtained from atmospheric retrievals. Two Bayesian inference methods are used to perform atmospheric retrievals: the standard nested sampling method and the supervised machine learning method of the random forest (trained on the model grid of Crossfield 2023). For nested sampling, Bayesian model comparison is used to identify the set of models with the required complexity to explain the data.

Feeling the Heat: testing external photoevaporation through optical forbidden lines in Orion

march 25, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 karina mauco,   European Southern Observatory
ABSTRACT

Most planetary systems, including our Solar System, form in massive star clusters, where external photoevaporation by UV radiation from OB stars profoundly influences the evolution of protoplanetary disks. The Orion star-forming region is a unique laboratory to study this process, mainly because it is the closest (~400 pc) star-forming region containing OB massive stars. 

In this talk, I will show the results of the first large-scale survey of the mid-age (~3-5 Myr) σ Orionis cluster, combining UV-IR spectroscopy and mm-continuum observations. By analyzing high-resolution optical spectra, we explore wind diagnostics through the characterization of forbidden lines, particularly the [OI] 6300 Å line. A compelling case is made for external photoevaporation mostly affecting the innermost regions, where disks exhibit remarkably low masses. 

In more hostile environments, such as the Orion Nebular Cluster, protoplanetary disks display striking teardrop-shaped clouds of ionized gas as massive stars irradiate the disk material. These objects, known as proplyds, are prime targets for studying the ionized structure of these systems. I will show the first spatially and spectrally resolved observations of 12 proplyds, taken with MUSE on the VLT. I will show striking images of the Orion proplyds, revealing their morphology across seven emission lines, and describe how the sizes of the ionization fronts and the mass-loss rates estimated for these sources confirmed the short lifetimes of the proplyds, which poses challenges for planet formation in clustered environments.

CO line emission supports large protoplanetary disk masses

april 01, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 dingshan deng, LPL, university of arizona
ABSTRACT

Carbon monoxide (CO) is one of the most abundant molecules in protoplanetary disks, and optically thin emission from its isotopologues has been detected in many disks. Surprisingly, the protoplanetary disk masses derived from CO line emission have been notably low and were inconsistent with the masses derived from other tracers. In this talk, I will discuss a new, comprehensive model that addresses the critical attributes related to CO: (a) isotope-selective chemistry, (b) freeze-out considering the grain-surface chemistry, and (c) gas density and temperature structures that are both consistent with the thermal pressure gradient. From this model, the CO line emission supports large masses in Myr-old disks. I will also present a simplified model that is capable of detailed modeling of individual targets, and its application to the disk of RU Lup. We find a disk mass larger than the Minimum Mass Solar Nebula, whereas previous estimates were around a Jupiter mass. An open-source Python-Fortran code DiskMINT (Disk Model for INdividual Targets) has also been released so that the community can extend this approach to any other disks. 

 

TBA

april 08, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 weicheng zang,   cfa
ABSTRACT

TBA

april 15, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 sarah moran,   lpl, University of arizona
ABSTRACT

 

 

TBA

april 22, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 justin hom,   steward observatory, university of arizona
ABSTRACT

TBA

april 29, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 sebastiaan haffert,   steward observatory, University of arizona
ABSTRACT

 

 

 

TBA

may 06, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 dominika itrich,   alien earths team, university of arizona
ABSTRACT

 

 

 

TBA

may 13, 2024   |   12 pm noon (MST)   |   Hybrid (kuiper 309 & Zoom)
 jessica barnes,   LPL, university of arizona
ABSTRACT

 

TBA

may 20, 2024   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 leonardo krapp, university of arizona
ABSTRACT

 

previous talks

2023 – FALL 

Dust Evolution in the Dense Infrared-Dark Clouds

august 28, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 wanggi lim,   IPAC
ABSTRACT
We introduce and present the techniques and results of Mid- and Far-Infrared extinction (MIREX/FIREX) mapping methods of Milky Way infrared-dark clouds (IRDCs) that enable construction of the deepest extinction maps. IRDCs are promising sources to search for massive molecular cores which are assumed to be progenitors of high-mass protoclusters. Understanding dust grain properties in IRDCs is important to determine the initial condition of massive star cluster formation since the density structure of the molecular clouds can only be estimated in terms of absorption opacities and emissivities of dust grains at very cold temperature. In this study, we measure the spectral energy distribution of Galactic background and foreground interstellar medium of the target IRDCs and utilize the information to construct the multiband MIREX/FIREX maps. The maps allow us to investigate dust opacity variation along MIR – FIR wavelength regime where the opacity trends are sensitive to the chemical composition and size distribution of the dust grains. The comparison of the observed dust opacity trend to theoretical models constrains the best assumption of ice mantle formation and dust coagulation in each pixel position of the extinction maps. After cross-checking the trends with other physical properties, we have found evidence of dust grain growth through ice mantle formation and dust coagulation as we traverse denser and colder regions within the IRDCs. The results also indicate that the densest regions in the earliest stage of high-mass star cluster formation potentially have equivalent dust properties with inner protoplanetary disks. We will explore the implication and potential application of the results.

NO TALK

september 4, 2023   |   12 pm noon (MST)   |   —-
LABOR DAY
 

Probing Young Planet Population with 3D Self-Consistent Thermodynamics 

september 11, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
shangjia zhang,  university of nevada
ABSTRACT

Protoplanetary disks are the birthplaces of planets. Over the past decade, there have been significant advancements in disk observations thanks to the Atacama Large Millimeter Array (ALMA) and extreme adaptive optics (ExAOs). Hundreds of disks have been observed at high angular resolutions, revealing rich substructures (e.g., gaps/rings) at various layers, some of which are perturbed by planets. A better understanding of disk physics holds great potential for unveiling more young planets within these substructures and distinguishing them from non-planet origins.

In this presentation, I will discuss how we can constrain the young planet population using statistical and machine learning techniques applied to these substructures. Additionally, I will explain the critical role of self-consistent dust and thermal structures in shaping disk morphology and kinematics, as well as why state-of-the-art radiation-hydrodynamic simulations are crucial for understanding substructures, planet formation, and the precise prediction of young planets.

NASA’s Europa Clipper mission to study the habitability of Europa  

september 18, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Alfred mcewen,  LPL, Planetary Image Research Lab
UNiversity of arizona
ABSTRACT

With launch planned in October 2024, NASA’s Europa Clipper will explore the habitability of Jupiter’s moon Europa. Arriving at Jupiter in 2030, the spacecraft will orbit Jupiter, flying by Europa more than 40 times over a four-year period to observe this moon’s ice shell and ocean, study its composition, investigate its geology, and search for and characterize any current activity. The mission’s science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft’s telecommunication system.  The spacecraft and payload are currently nearly complete, and system testing is underway. The Jupiter tour is complete, and work is beginning on detailed science planning to achieve the science objectives, which require multiple science instruments.  The project has a “one science team” philosophy, which will be an interesting experiment for this type of mission.  There are extensive plans for inclusion of a diverse community.  

A multiwavelength perspective on planet formation conditions

 

september 25, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
catherine espaillat, Boston University
ABSTRACT

We know that protoplanetary disks surround many pre-main-sequence stars, but how these systems evolve into planetary systems is a fundamental question in astronomy. Multiwavelength studies of these variable young stars can provide insight into the star-disk connection and the conditions under which planets form. This talk will review key observations of protoplanetary disks and their young stars, focusing on multiwavelength observations and variability. I will discuss variable high-energy radiation fields generated by the accretion process (traced in the UV and optical) and disk masses and structures observed at longer wavelengths (in the IR and mm).  To conclude, I will discuss possibilities for future progress in multiwavelength time-domain studies of these young systems. 

Talk 1: Observations of Exoplanet Atmospheres, from the Ground and from Space

Talk 2: Bioverse and the Prospects for Observing Biosignatures

 

october 02 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Alien earths team,   university of Arizona

 Megan Mansfield (U Arizona/Steward Obs) & Kevin Hardegree-Ullman (U Arizona/Steward Obs)

ABSTRACT1
In this talk, I will review recent developments in observational characterization of exoplanet atmospheres using both ground-based and space-based observations. I will present some results from the JWST Transiting Exoplanet Early Release Science program, and I will discuss the recent development of the technique of spectroscopic eclipse mapping. I will also discuss recent advances in measuring atmospheric compositions using ground-based, high-resolution instruments, including how these observations are giving us new ways to probe planetary formation pathways. Finally, I will discuss future possibilities for studying exoplanet atmospheres with the next-generation Extremely Large Telescopes.
ABSTRACT2

 

New and upcoming space and ground-based facilities aim to deliver the first true measurements of biosignatures on rocky habitable zone planets. Recent studies have concluded JWST should be able to detect certain biosignatures such as CO2 and CH4 under the right exoplanet atmospheric conditions, but key biosignatures such as O2 will not be detectable. The collecting area, sensitivity, and wavelength coverage afforded by the ELTs make them the perfect platform to complement observations with space telescopes and can significantly increase our ability to detect biosignatures. We developed Bioverse, an open-source modular framework to simulate surveys, test hypotheses, and perform trade studies to assess the capabilities of upcoming and future facilities to detect exoplanet features such as biosignatures and address population-level questions. Our recent Bioverse simulations with the ELTs go beyond previous studies and account for constraints such as planet occurrence rates, relative system velocities, and target observability. I will present our new simulations, which predict whether or not Earth-like levels of O2 could be probed on Earth-sized exoplanets within 20 pc of the Sun, including the TRAPPIST-1 system. Bioverse, and the new capabilities added by our project, now enables realistic, systematic assessment of which hypotheses about habitable exoplanet atmospheres will be testable by joint constraints from the ELTs and new space facilities.

The ongoing hunt to detect the radio emissions of exoplanets 

october 09, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)

jake turner ,  cornell university

 

ABSTARCT

One of the most important properties of exoplanets has not yet been directly detected despite decades of searching: the presence of a magnetic field. Observations of an exoplanet’s magnetic field would yield constraints on its planetary properties that are difficult to study, such as its interior structure, atmospheric escape and dynamics, and any star-planet interactions. The presence of magnetic fields on gas giants also affects the understanding of their origins and evolution. Additionally, magnetic fields may contribute to the habitability of terrestrial exoplanets. Observing planetary auroral radio emission is the most promising method to detect exoplanetary magnetic fields. 

In this talk, I will present our recent study of the Tau Bootis exoplanetary system where we have the first possible detection of an exoplanet in the radio using LOFAR (Turner et al. 2021).  Assuming the emission is from the planet, we derived a maximum surface polar magnetic field for tau Boo b between ~5-11 G. The magnetic field and emission strengths we derived are consistent with theoretical predictions, and if this detection is confirmed it will place important constraints on dynamo theory, comparative planetology, and exoplanetary science in general. Additionally, I will present the first results of an extensive multi-site follow-up campaign to confirm the radio detection of tau Boo b. Our first observing campaign consists of low-frequency radio data taken simultaneously from NenuFAR and LOFAR. Preliminary analysis of this data show no signs of emission. Therefore, the original signal may have been caused by an unknown systemic or we are observing variability in the planetary radio flux due to observing at different parts of the stellar magnetic cycle. Our second follow-up observing campaign is designed to test the latter conclusion. We have coordinated observations of the magnetic maps of the host star alongside many months of intensive radio monitoring by NenuFAR. Preliminary results on the second campaign will be presented. Finally, I will briefly highlight the promising landscape of studying exoplanetary magnetic fields in the coming decades with future ground- and space-based radio telescopes

The Value of a Gibbous Asteroid: Connections between Phase Curves and Asteroid Taxonomy

october 16, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Zachary Murry,  harvard university
ABSTRACT

The relationship of an asteroid’s magnitude to its phase has a long history of study including efforts to study the correlation between these parameters and spectral type. However, these efforts often suffer from the inclusion of only a few asteroids, missing phase curve data, uncorrected rotational or apparitional aberrations, and other issues. We take a closer look at the problem and figure out how much information about an asteroid’s spectral type is contained in its phase curve.

Characterizing the climates of temperate rocky exoplanets in the era of JWST

october 23, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Tad Komacek,  university of maryland
ABSTRACT

The advent of JWST has enabled the first broadband spectroscopic studies of rocky exoplanets orbiting nearby stars. JWST will provide an opportunity to potentially constrain the atmospheric composition of rocky exoplanets that lie within the habitable zones of low-mass stars. However, such observational characterization via transmission spectroscopy may be formidable due to challenges associated with stellar activity, atmospheric loss, and high-altitude clouds and hazes. In this talk, I will discuss recent efforts to determine the extent that clouds and time-variability impact the transmission spectra of temperate rocky exoplanets orbiting M dwarf stars. To simulate the impact of clouds on the climate state and observable properties of rocky exoplanets, we use the ExoCAM GCM post-processed with the Planetary Spectrum Generator (PSG) Global Emission Spectra (GlobES) radiative transfer code. I will present simulations of 3D climate, atmospheric variability, and transmission spectra both for idealized systems of rocky exoplanets orbiting M dwarf stars, as well as the best habitable zone candidate for observational characterization, TRAPPIST-1e. By applying a novel dynamical systems framework, we find that many properties of the climate dynamics of TRAPPIST-1e are analogous to that of Earth, but the planet is strongly discrepant to Earth in its extreme climate behavior. We find that TRAPPIST-1e both undergoes amplification of nightside temperature (similar to polar amplification on Earth) and increasing high-altitude variability with increasing greenhouse gas complement. We also find that cloud coverage does not prevent detection of both the key habitability indicator water vapor as well as the potential carbon dioxide-methane biosignature pair in the atmosphere of TRAPPIST-1e over the nominal lifetime of JWST. This implies that searching for disequilibrium biosignature pairs in the atmospheres of temperate rocky planets orbiting nearby low-mass stars may be feasible in the coming decade.

 

JWST as a Linchpin for Circumstellar Disk Science

october 30, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Schuyler Wolff,  steward observatory, university of arizona
ABSTRACT

Since the discovery of the “Vega Phenomenon” with IRAS, circumstellar disks have been a growing field of study for their ability to serve as signposts for both stellar and planetary system evolution. The infrared is ideally suited to observe these systems where thermal emission from the dust peaks and solid state spectral features can elucidate the dust properties. JWST allows for unprecedented spatial and spectral resolution in the near to mid-IR and has already changed our view of several archetypal disk systems. I will present results from several disk-focused JWST GTO programs using both scattered light observations with NIRCam coronagraphy and thermal emission with MIRI. In a broader context, I will discuss the potential impact of JWST on our understanding of circumstellar disk physics and how it complements past and future observatories. 

AI4Astro: Exploting star formation and ISM through artificial intellicence

november 06, 2023   |   12 pm noon (MST)   |   Hybrid (So n305 & Zoom)
duo xu,  university of virginia
ABSTRACT

TBAMachine learning, particularly deep learning, is transforming astronomy by enabling efficient processing of large datasets. Deep learning surpasses human capabilities in rapidly and accurately analyzing complex data such as images and data cubes in the field of the interstellar medium and star formation. Denoising diffusion probabilistic models (DDPMs) are machine learning algorithms inspired by diffusion thermodynamics, demonstrating state-of-the-art performance in various domains. DDPMs offer several advantages as tools for inferring physical quantities in astronomy, including stable training, robust performance, interpretability, and alignment with the inherent nature of scientific problems. In this talk, I will introduce applications of DDPMs to infer intrinsic physical quantities, such as volume density and interstellar radiation field, from observational data. I will also introduce how DDPMs can be used for segmentation tasks, such as segmenting filaments from dust emission.

Gas-Rich Debris Disks’ Origins in Slow Photoevaporation Around Intermediate-Mass Stars

november 08, 2023 (WEDNESDAY SPECIAL TALK)   |   12 pm noon (MST)   |   Hybrid (TBA & Zoom)
Ryohei nakatani,  NASA/JPL
ABSTRACT
In the study of planet formation, a key goal is understanding how protoplanetary disks (PPDs) evolve into systems of planets and debris.  Traditionally, PPDs are thought to last no more than 10 million years (Myr), as inferred from infrared, Hα, and UV observations.  This age marks the transition from gas-rich PPDs to gas-free debris disks.  However, recent observations have revealed about 20 debris disks harboring gas, despite ages exceeding 10 Myr.  These gas-rich debris disks are found most often around A-type stars up to 50 Myr old.
Our new radiation hydrodynamics simulations demonstrate that PPDs’ gas can persist beyond 10 Myr around A stars if the disks become depleted of small grains compared to the interstellar medium.  In such cases, photoevaporation operates slowly due to inefficient photoelectric heating and the host stars’ weak EUV and X-ray emissions.  The model also predicts disk lifetimes that align with the observed incidence of gas-rich debris disks versus host star mass.  These results suggest many of the gas-rich debris disks are long-lived protoplanetary disks, contradicting the common wisdom that the gas was released much more recently from asteroids or comets.
Apart from our new study above, I will also additionally talk about molecular photoevaporative winds observed in the self-consistent radiation hydrodynamics simulations of my previous studies.  

A MANATEE Dive into Hot Jupiters with JWST

november 13, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Everett Schlawin,  steward observatory, University of arizona
ABSTRACT

Transmission and emission spectra give insights into the composition, temperature structure, aerosols and formation of giant planets. The MANATEE survey probes the atmospheres of giant planets and extends from warm planets, where methane is expected to be a significant carbon reservoir to hot planets where carbon monoxide is a significant carbon reservoir, permitting study of the chemistry and physics of these planets. We will focus on two hot Jupiters: WASP-80 b, which has methane throughout its atmosphere and WASP-69 b, for which obtain new view of the dayside with a JWST emission spectrum to 2.1 to 11 microns. WASP-69 b’s atmosphere is enriched in heavy elements compared to solar composition, as evidenced by its carbon dioxide, carbon monoxide and water vapor content. We also find an unexpectedly high planet-to-star flux ratio at short wavelengths, indicating a possible influence of clouds either by reflecting light or modifying the temperature structure. These JWST spectra open a new window into hot Jupiter atmospheres in the sub-1000 K temperature regime where chemical transitions and aerosol formation can occur.

constraining the physical properties and volatile contents of the original planetesimals

november 20, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
bryce bolin,  NASA GSFC

ABSTRACT
Small solar system bodies can be broadly separated into two groups: a.) those that accrete directly from the protoplanetary disk and b.) those that are fragments produced by the collisional disruption of a larger parent body. Fragments in the solar system’s Main Belt fragments disperse in physical space over time due to secular gravitational and non-gravitational effects, however, remain linked by their orbital and physical parameters. We have developed a technique with the capability of identifying a group of asteroids as collisional fragments based on correlations between their physical and orbital parameters. This technique was used to discover >4 Ga-old asteroid families in the inner MB revealing asteroids with D > 35 km that do not belong to any asteroid family implying that they originally accreted from the protoplanetary disk and support recent theories on the formation of planetesimals. In addition, we study the volatile contents of a ~140 km diameter comet, C/2014 UN271, large enough that it could be an intact example of a planetesimal that formed in the protoplanetary disk. UN271 is on its first inward journey into the solar system’s planetary region from the Oort cloud implying that its volatile contents may be preserved since the accretion of the parent body in the protoplanetary disk. We present JWST/NIRSpec prism IFU observations of UN271 between 0.6-5.3 microns providing coverage of cometary ice and gas features and their production rates. We will discuss the implications for the timing of the formation of the original planetesimals as well as UN271’s formation environment within the protoplanetary disk.

Atmospheric Chemical Reaction Network Topology as a Potential Biosignature for Exoplanets

november 27, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Theresa Fisher , Alien earths team,  EEB, University of arizona

ABSTRACT

With the ability to potentially observe the atmospheres of exoplanets via transit spectroscopy on the near-term horizon, the possibility of atmospheric biosignatures has received considerable attention into astrobiology. While traditionally the field was focused on biologically relevant trace gases such as O2 and CH4, this approach has raised the specter of false positives. Therefore, to address these shortcomings, a new set of methods is required to provide higher confidence in life detection. 

One possible approach is measuring the topology of atmospheric chemical reaction networks (CRNs). To assess the use of CRNs as biosignatures, a large number of  terrestrial worlds were modeled, divided into two categories: Anoxic Archean Earth-like planets that varied in terms of methane surface flux (featuring either biotic or abiotic sources), and modern Earth-like planets with and without a surface flux of CFC-12 (to represent the presence of industrial civilizations). Atmospheric CRNs were constructed from the converged models and analyzed their topology, finding that network metrics provided greater constraints on the presence of life or technology, particularly in the case of the Archean Earth models. These results suggest that atmospheric CRN topology can provide a lower risk of false positives in detecting exoplanet biosignatures.

Decoding Exoplanet Atmospheres: The Revolutionary Role of JWST

december 04, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Luis Welbanks, arizona state university 
ABSTRACT

The 2020s and beyond will be the era of spectroscopy of exoplanet atmospheres. In just 2 years, our field has made dramatic advancements, moving from having very limited wavelength coverage and precision data from the Hubble Space Telescope (HST), to having high-precision spectroscopy over a wide wavelength range (~0.4 to 20μm) with the James Webb Space Telescope (JWST). These exquisite observations come with the opportunity to perform detailed reconnaissance of exoplanet atmospheres, explore their chemical and physical properties, and perform population-level studies to test our hypotheses for planet formation and evolution.

In this talk, I will share with you the advancements ushered by the era of JWST, allowing us to answer not only what exoplanet atmospheres are made of, but also which data drive our inferences and how reliable these inferences are. I will present the results from several programs with JWST. In these programs, we detect and constrain several chemical species that were previously elusive in exoplanetary atmospheres, including methane (CH4), ammonia (NH3), sulfur dioxide (SO2), carbon monoxide (CO), and carbon dioxide (CO2), alongside several precise water (H2O) measurements. The atmospheric retrievals performed on these data provide insights into the dynamics, chemistry, and climatic conditions of these distant worlds, as well as their metallicities. They also provide the relative elemental ratios (C/O, N/O, N/S) necessary to better understand the formation and evolution pathways of planetary systems.

I will present our progress in robustly and accurately processing JWST Time-Series Observations data. Additionally, I’ll discuss modeling advancements and our methods for reliably inferring the complete chemical inventory of our diverse exoplanet sample. Our findings underscore the transformative power of JWST and pave the way for future, in-depth atmospheric investigations of a larger exoplanet population.

TBA

december 11, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
OPEN

ABSTRACT

TBA

 

2023 – Spring 

finding atmospheres on m dwarf terrestrial planets with jwst

january 23, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
megan mansfield,  
alien earths team, Steward observatory, U Arizona
ABSTRACT

The launch of JWST in December 2021 opened up a new realm of transiting planets to atmospheric characterization. For the first time, we will have the necessary sensitivity to study detailed spectra of terrestrial planet atmospheres and begin to search for gases that could indicate a planet suitable for life. However, there remain several unknowns about terrestrial planets orbiting M dwarfs. A first order question in our search for habitable exoplanets is whether M dwarf planets hit with intense stellar radiation could hold onto atmospheres long enough to develop life. In this talk, I will first give a broad overview of the first exoplanet results from JWST and its expected capabilities for characterizing terrestrial planets. I will then present a method of using JWST to quickly determine which M dwarf planets host atmospheres by measuring secondary eclipse photometry with the Mid-Infrared Instrument (MIRI). Finally, I will discuss how this method will be applied in JWST programs later this year.

HALPHA: an HST search for accreting protoplanets in transition disk gaps

january 30, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 Yifan zhou,   University of texas, Austin
ABSTRACT
The direct-imaging detections of accreting young planets open up a new era of planet formation studies. These observations allow us to witness how planets assemble, constrain planets’ mass accretion processes, and understand the interactions between planets and their natal environment. Hubble Space Telescope (HST) naturally obtains high-Strehl-ratio images over a broad wavelength range, particularly the optical and ultra-violet (UV) bands where planetary spectra show accretion signatures. This capability offers exciting opportunities to discover and characterize accreting planets. Recently, we embarked on the Hubble Accreting Luminous Protoplanets in H-Alpha (HALPHA) Survey to search for accreting planets in gaps of transition disks. I will present the survey’s motivation, design, and early results. I will also describe the follow-up effort in validating the protoplanet candidate AB Aur b. The exquisite high-contrast images collected by our survey create numerous collaboration opportunities for investigating the formation and evolution of giant planets.

Atmosphere of an Accreting planet in Realistic Global Disk Models

february 6, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 leonardo krapp,  Steward observatory, U arizona
ABSTRACT

Giant planet formation leads to two distinct classes of planets: gas giants like Jupiter whose mass is dominated by their gaseous envelope and ice giants where a much smaller envelope overlays a rocky or icy core of several Earth masses. What process halts the growth of ice giants and determines their final mass and composition is currently under hot debate. In this talk, I will present 3D multi-fluid hydrodynamics simulations of a planet embedded in a disk. I will focus on realistic cooling calculations with opacity based on self-consistent dust dynamics. In particular, I will showcase the regimes where the opacity of the planet envelope deviates from spherical symmetry, and therefore it may not be trivially cast in 1D models. This is critical to assess the scope of the leading core accretion theory and explain the exoplanets demographics.

Constraining the Evolution of Protoplanetary Disks in Clustered Star-formation Environments

february 13, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Ryan boyden,  alien earths team,Steward observatory, U arizona
ABSTRACT

Protoplanetary disks are the birthplaces of planetary systems, and obtaining a complete picture of how planets form hinges on an understanding of how disks evolve throughout the Galaxy. The Atacama Large Millimeter Array (ALMA) and Karl G. Jansky Very Large Array (VLA) provide the sensitivity and resolution needed to detect large samples of protoplanetary disks in young stellar clusters, the most common sites of star formation in our Galaxy. In this talk, I will present the analysis of deep, high-resolution ALMA CO(3-2) and HCO+(4-3) observations covering a large sample of disks in the Orion Nebula Cluster (ONC). I first introduce the sample of disks that are detected in the observations, and then outline a novel procedure that utilizes thermochemical and line radiative transfer modeling to constrain the total disk masses, gas-to-dust ratios, and central stellar masses of the detected sources. I find that the ONC disks are massive and compact, with typical radii <100 AU, gas masses >1 Jupiter mass, and gas-to-dust ratios >=100. The ISM-like gas-to-dust ratios derived from thermochemical modeling suggest that compact disks in the ONC are less prone to gas-phase CO depletion than the massive, extended disks that are commonly found in lower-mass star-forming regions. The presence of massive gas disks indicates that a subset of disks in the ONC still have plenty of material to form giant planets, despite ongoing environmental effects. Finally, I will discuss my recent work with the VLA to constrain the free-free emission spectra and complete the census of ‘proplyds’ towards young stellar objects in the Orion NGC 1977 and NGC 2024 clusters.

Talk is CANCELLED 

 

february 20, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
logan pearce,  steward observatory, U arizona
ABSTRACT
I will present an overview of several observational projects using high contrast imaging to probe planetary regimes of stars, particularly those with wide stellar companions.  I will describe the unique utility of wide binaries in direct imaging observations and data reduction through the Binary Differential Imaging technique (BDI), and a new stellar binary discovered using BDI and astrometry with MagAO and MagAO-X.  I will briefly discuss the MagAO-X extreme adaptive optics instrument, its current status and science goals, and two new direct imaging surveys I am conducting with MagAO-X: a white dwarf-main sequence binary survey and an accelerating stars survey.  Finally I will discuss the follow-on instrument GMagAO-X for the Giant Magellan Telescope and a project I am beginning with collaborators at NASA Ames on modeling planets in reflected light imaging with GMagAO-X.

Revealing the population of forming giant planets (special talk)

 

february 22, 2023   |   12 pm noon (MST)   |   Hybrid (SO 550 & Zoom)
Gabriele Cugno, University of Michigan
ABSTRACT

During the last years (sub-)mm and high contrast imaging observations have targeted dozens of circumstellar disks, revealing a breathtaking diversity in substructures like gaps, spirals, etc. It is thought that at least some of the observed structures are related to the formation of protoplanets. To test this hypothesis, in the past years the NaCo-ISPY large program collected deep high-contrast imaging data of more than 50 young protoplanetary disks. This is the largest existing survey uniquely focused on this type of objects and it provides a great opportunity to reveal young objects embedded in disks and statistically characterize their population.  In this talk, I will present the newest results from the ISPY protoplanetary disks survey, including the detection of known and new companions and disks. In addition, detection limits were obtained, providing strong constraints on which planet architectures could exist and on the overall giant planet population around young stars. 

Characterizing Brown Dwarfs and Exoplanets in the Mid-Infrared

february 27, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
brittany miles,  steward observatory, U Arizona
ABSTRACT

Brown dwarfs are high-quality testing grounds for atmospheric models and optimizing requirements for exoplanet-focused instrumentation. Brown dwarfs have similar atmospheric physics and chemistry to gas giant exoplanets, but are much easier to observe because they do not suffer from host star obscuration. I will discuss observational projects to characterize disequilibrium chemistry and cloud properties in the atmospheres of brown dwarfs in different effective temperature ranges. First, I took 3 – 4 micron spectra of VHS 1256b and PSO 318.5, two analogs of the HR 8799 planets using Keck/NIRSPEC. We detected depleted methane features, providing evidence of atmospheric disequilibrium chemistry. For my second project, we acquired Gemini/GNIRS 4.5 – 5 micron spectra of four ultra-cool brown dwarfs. Combined with previously existing mid-infrared spectra of four additional brown dwarfs I show that brown dwarfs 700 K and below have disequilibrium carbon monoxide absorption. Lastly, I will share the results of the JWST Early Release Science observations of VHS 1256b which cover 1 to 20 microns at medium resolution and show detections of water, methane, carbon monoxide and silicate cloud features. 

No Talk

march 6, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)

University of Arizona Spring Recess

Revealing Atmospheric Trends on Irradiated Brown Dwarfs with Phase-resolved HST/WFC3 Spectroscopy

march 13, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Rachael amaro,  steward observatory, u arizona
ABSTRACT

Brown dwarfs in tidally-locked orbits around white dwarfs offer an exciting opportunity to explore properties of irradiated atmospheres. These highly irradiated brown dwarfs have ultrashort rotation periods (<2 hours), weak to strong internal heat flux, and intense external irradiation, making them an ideal testbed for investigating the importance of these parameters on key atmospheric processes. In this talk, we will present high-quality, phase-resolved HST/WFC3 spectroscopy from 1.1 to 1.7 microns of the binary system NLTT5306, a ~1700 K brown dwarf in a ~102 minute orbit around a white dwarf. With this brown dwarf, our team addressed two key questions driving atmospheric studies: (1) understanding the structure and formation/disruption of clouds under the presence of intense, tidally-locked irradiation, and (2) characterizing the efficiency of day-to-night heat redistribution. Finally, we end with an overview of the constraints on cloud cover and atmospheric dynamics in four irradiated brown dwarfs, exploring trends with irradiation level, temperature, and rotation period.

Prebiotic Chemistry in Hydrothermal Systems on Early Earth and Ocean Worlds

march 20, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Laurie Barge,  JPL
ABSTRACT

It is theorized that life on Earth could have begun at seafloor hydrothermal vents – if so, this also provides a possible way for life to emerge on ocean worlds such as Saturn’s moon Enceladus which may host hydrothermal systems. However, hydrothermal vents on Earth host a variety of chemical conditions, which can result in different outcomes of prebiotic organic reactions. In this talk I will discuss our group’s work on simulating prebiotic hydrothermal chimneys and sediments, and the organic chemistry that can occur within. Particularly I will present results from our recent studies investigating how changing geochemical conditions can lead to different prebiotic reactions, and discuss different types of vents in which these conditions may be found. Our origin of life investigations aim to bridge the gap between geochemistry and biochemistry in an early Earth context, as well as to inform the search for life and its origin on other planets.

 

Coupling interior, atmosphere and microbial growth models to assess habitability and predict biosignatures

march 27, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Antonin Affholder
alien earths team, steward observatory, u arizona
ABSTRACT

What constitutes evidence that an extraterrestrial environment could be habitable to certain organisms? What constitutes a clue that a biosphere might exist on a planet or a moon?

To tackle those questions, one must lay out the theoretical basis that can (i) assess whether certain conditions permit viability of a population of given organisms and (ii) couple the dynamics of such a population to geochemical processes that together shape the value of quantities measurable remotely: observables.In this Origins Seminar, I will describe how we modeled a hypothetical population of methanogens at Enceladus’s seafloor to assess the habitability and biosignatures of the icy Saturnian moon. Next, I describe how ongoing work aims to port this inference approach to assessment of habitability and biosignatures of terrestrial exoplanets using atmospheric spectrum. 

Radio Perspectives on Star-Planet Interactions

april 3, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
melodie m. kao,  UC Santa cruz, ASu
ABSTRACT

Planetary magnetic fields influence atmospheric evaporation from space weather, yield insights into planet interiors, and are essential for producing aurorae. The most direct way of measuring magnetic fields on exoplanets and their brown dwarf cousins is by observing their magnetospheric radio emission.  Low-frequency radio arrays will soon be sensitive to exoplanet radio emission and provide a new means of exoplanet detection and characterization. Now is a critical time to prepare for these upcoming searches by harnessing detailed studies of radio emission on observationally accessible exoplanet analogs: planetary-mass and cold brown dwarfs. I will synthesize the state of the art for radio star-planet interactions as well as brown dwarf magnetospheric radio studies, discuss implications for exoplanet magnetism, and highlight opportunities for the next generation of ground- and space-based radio facilities.

Life in the Light: Photochemical Insights Towards Life as a Planetary Phenomenon

april 10, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
sukrit ranjan,  LPL, University of arizona
ABSTRACT

Advances in origins-of-life chemistry are transforming our understanding of how life emerged on Earth, while upcoming space missions offer the prospect of detecting life on other worlds. Fundamental to both quests is interaction of UV radiation with molecular systems (photochemistry). Photochemistry controls the chemical context for the origin of life on Earth and influences the molecular signposts with which we hope to detect life elsewhere. I will share photochemical work which refines our understanding of early Earth environments, and demonstrate how such understanding enables assessment and improvement of theories of origins-of-life chemistry. I will discuss photochemical efforts to elucidate potential atmospheric biosignatures of life on other worlds, and show how the search for life on other worlds may enable tests of theories of the origin of life. In sum, I will review theoretical, experimental, and observational work towards understanding the origin and distribution of life in the universe through the lens of photochemistry.

Using ancient meteorite inclusions to constrain dynamics in the protoplanetary disk

april 17, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
emilie dunham,  ucla

ABSTRACT

Ancient particles found in meteorites called calcium-aluminum-rich inclusions (CAIs) were the first-formed solids in the hot inner region of the Solar System and can be used as tracers of movement in the solar nebula disk. Carbonaceous chondrites (CCs) contain abundant CAIs but are thought to have accreted in the outer Solar System, requiring that CAIs must have been transported outward. Curiously, CAIs are rare in ordinary, enstatite, and rumuruti chondrites, non-carbonaceous chondrites (NCs), that likely formed in the inner Solar System. In this presentation, I will address whether the hypothesis of an early-formed proto-Jupiter “opening a gap” in the disk can explain the dichotomy in the relative abundance of CAIs in CC and NC chondrites. To do this, I will explore the abundance, size, and mineralogy of 232 new NC CAIs as well as Al-Mg and oxygen isotope systematics of a subset of these. We find that, though NC CAIs are less abundant (0.01 area%), smaller, and have less melilite than CC CAIs, both NC and CC CAIs have similar isotopic characteristics. Together, this suggests that NC and CC CAIs formed in the same environment over a ~400,000 year time period, that CAIs were transported outwards by disk diffusion, and that the proto-Jupiter gap trapped CAIs in the outer Solar System. 

 

Nearby young moving groups: improvement on membership evaluation and the age of the beta-Pictoris moving group

april 24, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
jinhee lee,  kasi, Korea  & steward observatory (KASI-arizona fellow)

ABSTRACT

Nearby, young moving groups (NYMGs) are loose stellar associations with mean distances of smaller than 100 pc from the Sun. The proximity and youth of the NYMGs have placed the NYMGs a unique position in studies of stellar, substellar, and exoplanet astrophysics. For example, the NYMG members have been prime targets for the direct imaging of exoplanets. To fully take advantage of the usefulness of these NYMGs, the properties of NYMGs should be well defined. Numerous searches to NYMG members increase the number of identified members, and there are heterogeneities in member selection criteria that may cause confusion in membership status. It links to the properties of NYMGs and related studies such as planet mass estimation from direct imaging. In this talk, I will introduce an NYMG membership calculation tool BAMG (Bayesian Analysis of Moving Groups) developed by our research group. I will also present an age estimation study of the beta-Pictoris moving group using traceback methods. Finally, I will introduce our project of exoplanet survey using Gemini/IGRINS and a planned project of target preparation for direct exoplanet imaging survey preparing the GMT era.

The distribution of volatile elements during rocky planet formation, a laboratory perspective

may 1, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Terry-Ann Suer, 
Laboratory For Laser Energetics, University of Rochester and Steward Observatory. 
ABSTRACT

Understanding the accretion and distribution of highly volatiles elements (HVEs: H, C, N, S) during planet formation is crucial for studies of habitability. With the recent expansion in the inventory of rocky planets by exoplanetary surveys, much effort is going into modeling planet formation and evolution with particular emphasis on atmospheres. In addition to being major atmospheric components, volatile elements can also get sequestered into metallic cores and silicate mantles during differentiation. Distribution coefficients and solubilities of volatile elements between major planet forming reservoirs are therefore key inputs for the models being used to connect the astrophysical observables with surface and interior processes. Recent works have focused on investigating the effects of pressure, temperature and redox on the metal-silicate and magma-gas exchange coefficients for the HVEs. I will present major recent results from these laboratory works and theirapplication to quantifying distribution of HVEs in bodies of sizes from planetesimals to the Earth. The limitation of the current dataset for modeling bodies larger than the Earth will be discussed. I will also present preliminary experimental results on the effects of deep terrestrial magma ocean conditions on the interpretation of geochemical signatures, particularly those relevant to volatile accretion chronology.

The Quest for Exoplanet Oxygen with Extremely Large Telescopes

may 8, 2023   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Kevin Hardegree-Ullman,  
alien earths team, steward observatory, u ariozna

ABSTRACT

Molecular oxygen is a strong indicator of life on Earth and may indicate biological processes on exoplanets too. Recent studies proposed that Earth-like O2 levels might be detectable on nearby exoplanets using high-resolution spectrographs on future extremely large telescopes (ELTs). However, these studies did not consider constraints like relative velocities, planet occurrence rates, and target observability. I will discuss our new comprehensive calculations accounting for these additional constraints. We updated and used the Bioverse framework to simulate a survey of M dwarfs within 20 pc to determine if it will be practically feasible to probe for Earth-like O2 levels on transiting habitable zone Earth analogs via transmission spectroscopy with the ELTs.

Bioverse and the habitable zone hypothesis

may 15, 2023   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
Martin Schlecker,  
alien earths team, steward observatory, u arizona

ABSTRACT

The study of planetary habitability has become a major emerging research area, with critical implications for the future of exoplanet exploration and ambitious ground- and space-based telescope missions. Yet, habitability remains challenging to determine for individual planets. My talk focuses on comparative planetology as a means to overcome some of these challenges. I will discuss comparisons of planet population syntheses with exoplanet demographics that illuminate the requirements for habitable terrestrial planets, including the role of giant planets for their water inventory. I will further present Bioverse, a quantitative framework for assessing the diagnostic power of next-generation exoplanet surveys, and its application in testing the habitable zone hypothesis. Specifically, we explored the requirements for a mission to probe and characterize its inner edge: the runaway greenhouse transition. It appears that this first empirical test of the habitable zone concept may be imminent. It will help to guide the search for extraterrestrial life in the Universe.

 

2022 – Fall 

Volatile chemistry in planet-forming disks

august 29, 2022   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
 jennifer bergner,   Alien earths team, University of Chicago
ABSTRACT

Planets form within disks composed of gas, ice, and dust in orbit around young stars. The distribution of volatiles (gas+ice) within these disks profoundly impacts both the chemical and physical outcomes of planet formation– including the delivery of prebiotic building blocks to new worlds.  In this talk, I will highlight our recent advances in disentangling how organic complexity is built up during the star and planet formation sequence, the role of interstellar inheritance in setting disk volatile compositions, and the distinctive volatile chemistry at play during the planet formation epoch.  These insights are gained by combining telescope observations, ice chemistry experiments, and disk simulations, each of which contributes an indispensable piece of the puzzle.  Taken together, we are assembling a more complete picture of the chemical environment which regulates the formation, composition, and potential habitability of planetesimals and planets 

lfast, the large fiber array spectroscopic telescope

september 06, 2022 (TUESDAY)   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
roger angel,   Steward observatory, U Arizona
ABSTRACT

The LFAST concept is to use thousands of small telescopes combined by fibers for high resolution spectroscopy (R=100,000 – 150,000), in a way that will realize large cost savings and lead ultimately  to an affordable ($1B) aperture of 20,000 m2. Such large aperture is needed, for example, to make a comprehensive search for biosignatures in the atmospheres of transiting exoplanets.

Each unit telescope of 0.76 m aperture (0.43 m2) will focus the image of a single star onto a fused silica fiber, subtending 1.32 arcsec. Our telescope design calls for a spherical mirror, with a 4-lens assembly at prime focus that corrects not only for spherical aberration, but also for atmospheric dispersion down to 30° elevation and for rapid image motion caused by seeing or wind jitter. A method for rapid production of such mirrors has been tested, in which a disc of borosilicate float glass is slumped over a high-precision polished mandrel to an accuracy that greatly reduces subsequent optical finishing time. For the first LFAST array, 1,200 m2 in collecting area, the telescopes will be mounted in the open in groups of 20 located 12 m apart., some 150 m in diameter, with a total of 132 mounts and 2,640 mirrors. The light from all the fibers will be combined at two central echelle spectrographs. Together, these cover simultaneously the spectral range 390 nm – 1700 nm. The targeted cost for this first installed LFAST telescope and fiber array is $60M.

Probing protoplanetary disk evolution using multi-wavelengths observations

september 12, 2022   |   12 pm noon (MST)   |   Hybrid (LPL 309 & Zoom)
marion Villenave,   JPL 
ABSTRACT

To form giant planets during protoplanetary disk lifetime, small micron sized particles must grow rapidly to larger grains. A full understanding of that process requires a detailed characterization of the radial and vertical structure of the gas-rich disks associated with young pre-main sequence stars. Multi-wavelengths observations of protoplanetary disks, for example in the millimeter and near-infrared, allow to probe two widely separated grain sizes that are differently affected by evolutionary mechanisms such as radial drift and vertical settling. In this talk, I will present constraints on both mechanisms using multi wavelengths observations, with a longer focus on disks seen edge-on. Highly inclined disks are of particular interest because they provide a unique point of view to unambiguously disentangle their vertical and radial dimensions. The modeling of multi-wavelength observations of such disks allows to identify high density regions, favorable for grain growth and planet formation, and to study the efficiency of planet formation in protoplanetary disks.

JWST’s First Stares at Transiting Exoplanet System

september 19, 2022   |   12 pm noon (MST)   |   Hybrid (SO 305 & Zoom)
everett schlawin,   steward observatory, u arizona
ABSTRACT

JWST is now peering into the atmospheres of planets and providing new insights about their composition with its unprecedented precision and window into the near-infrared and mid infrared. I will discuss our very first looks at the Universe from NASA’s premier space observatory, our initial performance tests as they relate to transiting planet science, what we learned about photometric stability from JWST’s first lightcurves of a transiting planet (HAT-P-14 b) and the systematic errors to look out for. I also will also share the first robust unambiguous detection of carbon dioxide in an exoplanet atmosphere (WASP-39 b) as part of a community Early Release Science program.

“Adding Insult to Injury” – The discovery of the Nadir impact crater

september 26, 2022   |   12 pm noon (MST)   |   Hybrid (LPL room 330Zoom)
 veronica bray,   LPL, U Arizona
ABSTRACT

Evidence of marine target impacts, binary impact craters, or impact clusters are rare on Earth. Seismic reflection data from the Guinea Plateau, West Africa, reveal a ≥8.5-km-wide structure buried below ~300 to 400 m of Paleogene sediment with characteristics consistent with a complex impact crater. These include an elevated rim above a terraced crater floor, a pronounced central uplift, and extensive subsurface deformation. Numerical simulations of crater formation indicate a marine target (~800-m water depth) impact of a ≥400-m asteroid, resulting in a train of large tsunami waves and the potential release of substantial quantities of greenhouse gases from shallow buried black shale deposits. Our stratigraphic framework suggests that the crater formed at or near the Cretaceous-Paleogene boundary (~66 million years ago), approximately the same age as the Chicxulub impact crater. We hypothesize that this formed as part of a closely timed impact cluster or by breakup of a common parent asteroid.

The Gaia and Extreme AO Revolution: Discovering, Weighing, and Characterizing Exoplanets and Brown Dwarfs

october 3, 2022   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Timothy brandt,   UC Santa barbara
ABSTRACT

While thousands of exoplanets and brown dwarfs are known, the theoretical models that allow us to interpret their spectra and luminosities are anchored by just a few with independently measured masses, ages (from their host stars), and atmospheric properties (inferred from spectra). I will present a combination of three observational techniques–astrometry, radial velocity, and imaging–to discover, weigh, and characterize massive exoplanets and brown dwarfs. Advances in adaptive optics and infrared instrumentation now enable us to see young exoplanets millions of times fainter than their host stars. Despite huge gains in sensitivity, however, high-contrast imaging surveys remain plagued by a lack of discoveries. I have calibrated a huge data set of stellar reflex motions; it can identify unseen planets and brown dwarfs by the gravitational tugs they exert on their host stars, and enable us to measure their masses and orbits. We have already begun to discover and weigh new substellar companions by targeting accelerating stars. With masses, orbits, and spectra of a growing sample of planets and brown dwarfs, we can finally test models of substellar formation and evolution.

Complex Organic Molecules in the ISM: Methanol, Fullerenes, and Carbon Nanotubes

october 10, 2022   |   12 pm noon (MST)  |   Hybrid (LPL 309 & Zoom)
 jacob bernal 
alien earths team,  LPL, U Arizona
ABSTRACT

The detection of Complex Organic Molecules (COMs) such as methanol and the fullerenes C60 /C70 in the interstellar medium (ISM) has transformed our understanding of chemistry in space, and have also raised the possibility for the presence of even larger molecules in astrophysical environments. In this talk I will highlight the recent mm-wave detection of methanol in cold molecular clouds at the edge of the Milky Way Galaxy. I will also discuss in situ heating of analog silicon carbide (SiC) presolar grains using transmission electron microscopy (TEM), designed to simulate shocks occurring in post-AGB stellar envelopes. These experimental findings reveal that heating the analog SiC grains yields C60-sized nanostructures, which later transform into multi-walled carbon nanotubes (MWCNTs). These MWCNTs are larger than any of the currently observed interstellar fullerene species, both in overall size and number of C atoms. The implications for both these findings on the interstellar chemical scenario will be discussed.

From the galactic to atomic scale: understanding planet formation and evolution 

october 17, 2022   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
 akash gupta,   uCLA
ABSTRACT
One of the most profound findings from NASA’s Kepler mission is the unexpected dearth of close-in exoplanets of sizes 1.5 to 2.0 Earth radii, i.e., a radius valley. This valley divides the population of the most abundant class of planets yet known, those between the sizes of Earth and Neptune, into small planets with Earth-like compositions and large planets with hydrogen-rich atmospheres or ice-rich interiors. Recently, we demonstrated that atmospheric mass-loss driven by the cooling luminosity of a planet and its host star’s bolometric luminosity can explain this observation, even in the absence of any other process. In this talk, I will describe the key physical processes that drive this core-powered mass-loss mechanism. I will present how our results compare with observations, the insights they give us and the testable predictions we make as a function of planet and host-star properties. This will include sharing our latest work on the characteristics of the radius valley around M dwarfs.

 

One of our significant findings is that most observed exoplanets have hydrogen atmospheres interacting with molten or super-critical interiors for millions to billions of years. In our Solar system, we see this for planets such as Jupiter and Neptune. Studies show that such interactions can have far-reaching implications for an atmosphere’s composition, structure, and evolution. However, we hardly understand these interactions, and studying them in a laboratory is difficult. I will discuss how we address this problem using quantum mechanical molecular dynamics. Specifically, I will share the findings of our upcoming work on the solubility of a planet’s hydrogen atmosphere in its super-critical water interior and their implications for planets and exoplanets such as Neptune.

TITLE: The ALMA-IMF Large Program: SiO Gas at Low and High Velocities, and First Results from CMF Analyses

october 24, 2022   |   12 pm noon  (mst) |   Hybrid (lpl 309 & Zoom)
 allison towner,   University of florida
ABSTRACT
The ALMA-IMF Large Program seeks to understand the origins of the stellar IMF by studying the distribution of masses of pre- and protostellar cores (the Core Mass Function, or CMF) in 15 high-mass star-forming regions (protoclusters) in the Milky Way. The origin of the stellar IMF at the high-mass end remains a matter of some debate, with some studies suggesting that high-mass cores mirror the Salpeter slope and others suggesting that the CMF is top-heavy compared to the IMF. In this talk, I will present first results from CMF studies of protoclusters in the ALMA-IMF sample, including how the CMF may vary with a protocluster’s evolutionary state or even vary locally within a single protocluster. I will also discuss a census of the SiO gas in the full sample, including 1) our full catalog of 319 protostellar outflow candidates, the outflow properties, and their connections to global properties within each protocluster, and 2) low-velocity, narrow, non-asymmetric SiO emission which is ubiquitous in our sample and may trace relic shocks or purely low-velocity processes. I will also discuss how these two types of emission relate to the overall evolutionary state of each protocluster.

 

Characterizing 3D Magnetic Fields in star-forming regions

october 31, 2022   |   12 pm noon (MST)  |   Hybrid (SO N305 & Zoom)
 yue hu,   universitiy of wisconsin-madison
ABSTRACT

Magnetic field, turbulence, and self-gravity are important in understanding star formation. However, 3D magnetic field orientation and strength were barely accessed. Based on our recently understanding of dust polarization and anisotropic MHD turbulence, I will present two novel methods, i.e., polarization fraction analysis (PFA) and velocity gradient technique (VGT), in tracing the 3D magnetic field orientation. By combing with the Davis–Chandrasekhar-Fermi method or the Differential Measure Analysis, I will show that the 3D magnetic field distribution, including both orientation and strength, is successfully recovered in the low-mass star-forming region L1688. The second method VGT employs spectroscopic emission lines to derive the magnetic field. I will show that VGT-measurement advantageously gets rid of the contribution from the cloud’s foreground/background. By using multiple molecular tracers, VGT reveals the magnetic field’s variation in different volume density regimes. I will discuss gravitational collapse’s effects on velocity gradient and briefly present VGT’s application of tracing magnetic fields in nearby galaxies.

 

(small) ground-based telescopes are crucial for spaced-based observatories

november 7, 2022   |   12 pm noon  (MST) = 11 Am PST  |   Hybrid (LPL 309 & Zoom)

NOTE: TIME CHANGE 

 robert zellem, JPL
ABSTRACT

Due to the efforts by numerous ground-based surveys and NASAs Kepler and Transiting Exoplanet Survey Satellite (TESS), there will be hundreds, if not thousands, of transiting exoplanets ideal for atmospheric characterization via spectroscopy with large platforms such as James Webb Space Telescope and ARIEL. However their next predicted mid-transit time could become so increasingly uncertain over time that significant overhead would be required to ensure the detection of the entire transit. As a result, follow-up observations to characterize these exoplanetary atmospheres would require less-efficient use of an observatorys timewhich is an issue for large platforms where minimizing observing overheads is a necessity. Here we demonstrate the power of citizen scientists operating smaller observatories (~1 m) to keep ephemerides fresh, defined here as when the 1σ uncertainty in the mid-transit time is less than half the transit duration. Here we describe Exoplanet Watch, a community-wide effort to perform ephemeris maintenance on transiting exoplanets by citizen scientists. Such observations can be conducted with even a 6 inch telescope, which has the potential to save up to 10,000 days for a 1000-planet survey.

MIRAC-5 and METIS: near and long-term prospects of ground-based MID-IR Astronomy

november 8, 2022 (TUESDAY)   |   12 pm MST = 11AM PST  |   Hybrid (SO N305 & Zoom)
 Rory bowens, university of michigan
ABSTRACT

Mid-infrared astronomy is a critical wavelength regime for the study of targets from planets to galaxies. Paired with direct imaging, we can unveil knowledge of planet luminosities, temperatures, and atmospheric compositions. In this talk, I will discuss near and long-term advancements in the field of ground-based mid-IR imaging. First, I will present the fifth incarnation of the Mid-Infrared Array Camera (MIRAC-5) instrument which will use a new GeoSnap (3 – 13 microns) detector. As one of the only 3 – 13 micron cameras used in tandem with adaptive optics (AO), MIRAC-5 will be complementary to the James Webb Space Telescope (JWST) and capable of characterizing gas giant exoplanets and imaging forming protoplanets (helping to characterize their circumplanetary disks). I will describe key features of the MIRAC-5 GeoSnap detector and summarize MIRAC-5’s important science capabilities, including prospects for obtaining the first continuum mid-infrared measurements for several gas giants and the first 10.2-10.8 micron NH3 detection in the atmosphere of the warm companion GJ 504b (Teff ~ 550 K) within 8 hours of observing time. MIRAC-5 will be commissioned on the MMT utilizing the new MAPS AO system in 2023. I will then discuss long-term plans for mid-IR direct imaging in the era of 30 m class telescopes which will have the angular resolution and sensitivity to directly image planets with R < 4 R⊕ around the very nearest stars. I predict yields from a direct imaging survey of a volume-limited sample of Sun-like stars with the Mid-Infrared ELT Imager and Spectrograph (METIS) instrument, planned for the 39 m European Southern Observatory Extremely Large Telescope (ELT). Using Kepler occurrence rates, a sample of stars with spectral types A-K within 6.5 pc, and simulated contrast curves based on an advanced model of what is achievable from coronagraphic imaging with adaptive optics, I estimate the expected yield from METIS using Monte Carlo simulations. I find the METIS expected yield of planets in the N2 band (10.10−12.40 μm) is 1.14 planets and also determined a 24.6% chance of detecting at least one Jovian planet in the background limited regime assuming a 1 h integration. I will conclude with an observing strategy aimed to maximize the possible yield for limited telescope time, resulting in 1.48 expected planets in the N2 band.

revealing Atmospheric Trends on Irradiated Brown Dwarfs with Phase-resolved HST/WFC3 Spectroscopy

november 14, 2022   |   12 pm noon  (MST) |   Hybrid (SO N305 & Zoom)
 rachael amaro,  
alien earths team, steward observatoryu arizona
ABSTRACT
Brown dwarfs in tidally-locked orbits around white dwarfs offer an exciting opportunity to explore properties of irradiated atmospheres. These highly irradiated brown dwarfs have ultrashort rotation periods (<2 hours), weak to strong internal heat flux, and intense external irradiation, making them an ideal testbed for investigating the importance of these parameters on key atmospheric processes. In this talk, we will present high-quality, phase-resolved HST/WFC3 spectroscopy from 1.1 to 1.7 microns of the binary system NLTT5306, a ~1700 K brown dwarf in a ~102 minute orbit around a white dwarf. With this brown dwarf, our team addressed two key questions driving atmospheric studies: (1) understanding the structure and formation/disruption of clouds under the presence of intense, tidally-locked irradiation, and (2) characterizing the efficiency of day-to-night heat redistribution. Finally, we end with an overview of the constraints on cloud cover and atmospheric dynamics in four irradiated brown dwarfs, exploring trends with irradiation level, temperature, and rotation period.

 

Complex organic molecules around low- and high-mass protostars

november 21, 2022   |   12 pm noon (MST)   |   Hybrid (lpl 309 & Zoom)
Pooneh Nazari,   leiden observatory
ABSTRACT

Planet cores are thought to start forming around protostars where many complex organic molecules are detected. Therefore, understanding the chemistry of these species helps us understand the chemistry of the forming planets. There are already high-sensitivity studies of complex chemistry toward single sources. However, a high-sensitivity statistical analysis of complex organics toward low- and high-mass protostars is missing. I will show results from observations of these species around ~40 high-mass protostars. Moreover, I will discuss how physical conditions can affect the observations of complex organics and our interpretation of the chemistry using radiative transfer models.

Inheritance of the Sun’s Short-Lived Radionuclides and Statistical Chronometry

november 28, 2022   |   12 pm noon  (MST) |   Hybrid (SO N305 & Zoom)
 steve desch,   arizona state university
ABSTRACT
At the Origins Seminar in April, Sasha Krot and I debated the origins of the short-lived radionuclides (SLRs) like 26Al and 10Be in the early Solar System. I argued that they were almost entirely inherited from the Sun’s molecular cloud. One line of evidence was the uniformity of 10Be/9Be ratios in all the calcium-rich, aluminum-rich inclusions (CAIs) that faithfully record the value they formed with in the solar nebula; this precludes irradiation in the disk as a significant source of SLRs (except for 36Cl). Another line of evidence was the low value 60Fe/56Fe ~ 10^-8 in all meteoritic samples, which obviates the need for late injection from supernovas as a source of SLRs. A third line of evidence was the concordance of ages derived using Pb-Pb, Al-Mg, Mn-Cr, and Hf-W chronometry, which implies uniformity of the SLRs 26Al, 53Mn, and 182Hf in the solar nebula. In this talk I will expand on this third line of evidence.
We have developed a mathematical framework we call “statistical chronometry” that allows us to find the optimal values of four parameters—(53Mn/55Mn)SS, (182Hf/180Hf)SS, the 53Mn half-life, and the Pb-Pb age of t=0—that maximize the concordance of the different radiometric dating systems, assuming the SLRs were uniformly distributed. We show that the rapidly cooled achondrites that must be concordant, are indeed concordant, strongly suggesting homogeneity of the SLRs. The Pb-Pb age of t=0 is 4568.6 Myr, 1.4 Myr older than is commonly reported for CAIs; we demonstrate that it is likely that the U-Pb system was disturbed in CAIs after they formed. There remains some evidence for 26Al heterogeneity in certain rare, small inclusions; but we show that these are all dominated by corundum or hibonite, indicating a chemical heterogeneity, not a spatial or temporal one. We discuss how this might have occurred. The picture that emerges is that the Sun formed in a spiral arm in the Galaxy, in a region with high star-formation rate, and inherited almost all of its SLRs from the molecular cloud, contaminated by supernovas but especially Wolf-Rayet stars.
Many of these ideas are also explored in the upcoming book chapter by Desch, Young, Dunham, Fujimoto & Dunlap for the Protostars and Planets VII conference:  https://arxiv.org/abs/2203.11169

Rotational evolution of young stars

december 5, 2022   |   12 pm noon (MST)  |   Hybrid (lpl 309 & Zoom)
Marina Kounkel, Vanderbilt University
ABSTRACT

In the recent years, with advancements of large surveys such as Gaia and TESS, the ability to measure ages of stars has significantly improved. Current census of stars with know ages exceeds a million stars, and it may soon increase by an order of magnitude. Through measuring rotational periods of variable stars with known ages, we develop an empirical gyrochronology relation of angular momentum evolution that is valid for slowly stars with ages up to 1 Gyr, with the typical precision of ~0.2-0.3 dex. Rapid rotators on the other hand appear to be associated with binary systems with intermediate range of separations, having been sped up following their loss of protoplanetary disks. These data enable detailed characterization of the early evolution of the fundamental properties of stars, and also reveal biases in our observations of the youngest stars.

The mysteries of gaps and pile-ups at planetary resonances

december 12, 2022   |   12 pm noon (MST)   |   Hybrid (SO N305 & Zoom)
Renu Malhotra,  
alien earths team, lpl, U Arizona
ABSTRACT

The orbital spacings of planets, the locations of planetesimal belts, the dynamical transport of planetary impactors, and the long term stability of planetary systems are all mostly controlled by orbital resonances. Orbital resonances also have practical applications, such as estimating exo-planet masses and designing low-thrust spacecraft trajectories. But orbital resonances are paradoxical, presenting the potential for enhanced stability as well as enhanced instability. In this pre-holiday edition of the Origins seminar I will attempt to explain some of the mysteries of gaps and pile-ups that are observed at planetary resonances.

2022 – Summer 

planet formation across different stellar evolutions

august 1, 2022   |   12 pm noon   |   Hybrid (SO N305 & Zoom)
Nicolas Kurtovic, MPIA Heidelberg
ABSTRACT

Planet formation seems to be ubiquitous around young stellar objects. In this talk I will explore the conditions for planet formation across different stellar masses, disk ages, and stellar multiplicity, through the scope of ALMA observations. My work focuses on describing the finest details in the disks emission, to obtain insight into how their future planetary architectures will look like. More about my work in www.nicolaskurtovic.com. 

2022 – Spring

The architectures of planetary systems: population synthesis meets observations

january 24, 2022   |   12 pm noon   |   Zoom

Martin schlecker, steward observatory, University of arizona
ABSTRACT

Exoplanets are now routinely detected and their properties, such as their mass and orbital periods, can be constrained to high precision. While it is widely recognized that multiple planets per system are common, their mutual relationships are still largely unexplored. By confronting simulated planet populations with observed exoplanets, I will show that planetary properties and the architectures of their host planetary systems are related, and, more specifically, that observables of small planets on short orbits might be used to infer the existence of additional planetary companions. I will discuss how a solidification of this prediction has the power to constrain central open questions in contemporary planet formation theory, ranging from the efficiency of pebble accretion to planet migration.

 

Contextualising Planetary Systems Through Galactic Archaeology Surveys

 

january 31, 2022   |   12 pm noon   |   Zoom
jake clark, Fulbright Future Scholar, University of Southern Queensland
ABSTRACT

There is an ever growing abundance of stellar surveys exploring the formation and evolution of our galaxy. These surveys collect and derive the properties for 100,000s of stars, which can also be used to better understand the properties of planet-hosts across the Milky Way.

My talk will showcase how valuable such surveys can be to the exoplanet community through my dissertation work using the galactic archaeology survey known as GALAH. I have been able to use GALAH, along with other surveys to better characterise both the chemical and physical properties of stars observed by the TESS mission. This has led to learning more about the stellar populations of planet-hosts across the Galaxy to uncovering clues towards the formation mechanisms of ultra-short period planets. I will also show how my work is useful for exogeologists in calculating the potential compositions of newly found worlds, to better understand their potential habitability.

 

Alien Earths: The Search for Habitable Worlds around Nearby Stars

february 7, 2022   |   12 pm noon   |   Zoom
dániel apai, university of arizona (Steward observatory and  LPL, University of Arizona)
ABSTRACT
With the number of extrasolar planet discoveries increasing rapidly, a key emerging frontier of exoplanet research is the search for potentially habitable planets around nearby stars. It is these relatively nearby planets that we may hope to survey in the near future for potential atmospheric signatures of life. However, due to the challenging nature of exoplanet observations, the majority of nearby planets remain undiscovered. In addition, the nature of many known, nearby planets remains still poorly understood due to the lack of data on their fundamental properties.
In this talk, I will present our large, NASA ICAR interdisciplinary project Alien Earths which aims to address these challenges. Our Alien Earths team works toward developing a comprehensive, integrative framework to study and characterize nearby planetary systems to determine which of them are more likely to harbor habitable worlds. In this talk, I will also show examples of how the architectures and the presence of planets in nearby planetary systems can be successfully predicted by combining system-specific but incomplete information with robust, population-level, statistical constraints. I will also describe how Alien Earths combines multiple lines of evidence to characterize nearby planetary systems and support target selection and the interpretation of observations of future missions that search for life on other worlds.

Water planet thresholds: The topographic scope for land atop a stagnant lid

february 14, 2022   |   12 pm noon   |   Zoom
Claire Guimond, University  of Cambridge, Dept. of Earth Science
ABSTRACT

Small water budgets produce desert worlds and large ones produce water worlds, but there is a narrow range of water budgets that would grant a marbled surface to a rocky planet. A planet’s topography can delimit this range in that it controls how much water could rest on the surface before flooding it. Thus we take a step in quantifying water world limits by estimating how minimum surface elevation differences scale with planetary bulk properties. Our model does not require the presence of plate tectonics, an assumption which has constricted the scope of previous studies on exoplanet land fractions. We focus on the amplitudes of dynamic topography created by rising and sinking mantle plumesobtained directly from models of mantle convectionbut also explore rough limits to topography by other means. Rocky planets several times more massive than Earth can support much less topographic variation due to their stronger surface gravity and hotter interiors; these planets’ increased surface area is not enough to make up for low topography, so ocean basin capacities decrease with mass. In cooler thermal states, dynamically-supported topography alone could maintain subaerial land on Earth-size stagnant lid planets with surface water inventories of up to approximately 100 ppm of their mass (or half Earth’s ocean mass fraction). Considering the overall cap to topography on such planets would probably raise this threshold ocean mass fraction by an order of magnitude.

 

Molten exoplanets as a window into the earliest Earth

february 21, 2022   |   12 pm noon   |   Zoom

Tim Lichtenberg, university of oxford (Alien earths team)
ABSTRACT

Due to the absence of a reliable rock record from the Hadean eon, our understanding of the planetary environment that gave rise to life on the earliest Earth is clouded. Upcoming exoplanet surveys, however, will significantly expand our view of the distribution and variability of rocky planets and their chemical inventories, giving opportunity to test scenarios of early planetary evolution. I will describe recent efforts to establish a comprehensive theoretical framework to simulate the coupled evolution of solidifying planetary mantles and their outgassing atmospheres on young rocky worlds for a wide range of instellation, mass, and composition. The presence or absence of magma oceans on short-period exoplanets can alter the observationally inferred bulk water abundance by up to one order of magnitude, motivating reassessments of previous escape studies including volatile locking in the planetary interior. Alternating cooling trajectories during primary envelope loss on sub-Neptunes can quench metal core formation and thus induce a qualitative change in mantle redox state, which alters the expected compositions of secondary atmospheres on super-Earths. Both of these effects are within the currently observationally accessible limits for individual exoplanetary systems and will be statistically testable with next-generation transit surveys. Increasing reconnaissance of high-temperature super-Earths will enable us to infer the early climatic and geodynamic evolution of temperate rocky worlds, and thus provide crucial information on the environmental context of the origins of life on Earth.

TITLE: The Roaring 20s: The Coming Revolution in Exoplanet Atmospheres

february 28, 2022   |   12 pm noon   |   Zoom

Thomas Beatty, steward observatory, university of arizona
ABSTRACT

It is now clear that exoplanets are ubiquitous in the galaxy. Though our understanding of exoplanet demographics has dramatically expanded over the last quarter-century, many fundamental questions about their origins and physical properties remain. For example, we lack a complete understanding of the chemical and physical processes shaping exoplanet atmospheres, including a full description of their clouds, the abundances of specific species, and the role of disequilibrium chemistry. We also do not well understand what makes a terrestrial planet habitable, with conditions conducive to life, rather than a dead planet. The atmospheric characterization of exoplanets plays a key role in helping us answer these questions, and with successful launch of JWST and the construction of new ground-based facilities, we are poised at the start of a new era of exoplanet observations. I will discuss what atmospheric characterization observations have shown us, and what we can expect to see in the next few years, about planet formation pathways and evaluating the potential habitability of exoplanets.

TITLE: Providing new constraints on the surface composition of Europa

march 14, 2022   |   12 pm noon   |   Zoom

 Ishan Mishra, cornell university
ABSTRACT

Composition of Europa’s surface remains our best window into the composition of its subsurface ocean, and spectroscopy is our primary tool for characterizing its surface’s composition. Of special interest are trace species like organics and oxides, whose presence and abundance distributions can provide valuable insights into the potential habitability of the subsurface ocean. I will present a data analysis framework for reflectance data, based in Bayesian statistics, that specializes in picking out trace signals in spectroscopic data. This Bayesian framework can quantify confidence in the presence of a given species, constrain its parameters like abundance and average grain size with confidence intervals, and explore solution degeneracies. I will show examples of its application to Europan data from Juno and Galileo missions in my recently published works. I will also talk about my current project of using this framework to assess the feasibility of detection and characterization of organics on Europa with current and upcoming instruments

TITLE: the ancient solar system revealed by lkunar exploration and impact cratering 

march 21, 2022   |   12 pm noon   |   Zoom

 Sam Cabot, yale university
ABSTRACT
Imminent Lunar exploration missions will provide opportunities to analyze the Moon’s regolith and resolve fundamental questions about the ancient Solar System. We discuss specific examples of ancient impact cratering processes that may have their signatures preserved in the Lunar regolith. First, we demonstrate that if Venus’ atmosphere was at any point thin and similar to Earth’s, then asteroid impacts transferred detectable amounts of lightly-shocked, Venusian surface material to the Moon’s surface. These rocks are well-preserved on the Moon, which lacks an atmosphere and significant geological activity. An ancient Venusian rock could constrain Venus’ history, and reveal the past existence of oceans. Second, we discuss how impact cratering may reveal the compositions and dynamical histories of Interstellar Objects (ISOs). At present, no theory satisfies both observational constraints and physical limitations imposed by formation processes. We show that impacts on Kuiper Belt analogues do not generate the sufficient quantity of large, nitrogen ice fragments necessary to explain ‘Oumuamua’s detection. We gauge the feasibility of identifying Lunar craters formed by anomalously fast (100 km/s) ISO impacts. While such craters should be extremely rare, melt volume and high-pressure petrology in Lunar craters may be diagnostic features once large volumes of material can be analyzed in situ. 

TITLE: A Hydrodynamic study of the escape of metal species and excited hydrogen in the atmosphere of the hot jupiter WASP-121B 

march 28, 2022   |   12 pm noon   | hybrid (zoom + SO N305)

Chenliang Huang, LPL, University of Arizona

ABSTRACT

Imminent The heating by photoionization in the thermosphere of short-period exoplanets can drive hydrodynamic escape, which is key to understanding the evolution of planetary atmospheres and explaining transit observations.  Besides powering atmospheric escape, the energy deposited by extreme UV photons from the host star can also be radiated away through collisionally excited atomic spectral lines.  In addition, metals and excited-state hydrogen, which have lower ionization potentials than 13.6 eV, can absorb the longer wavelength photons in the stellar spectrum.  These two factors, in addition to Roche lobe overflow, can cause the mass loss rate to exceed the traditional energy-limited value.  In the near UV and optical transmission spectrum of the hot Jupiter WASP-121b, recent observations have detected strong absorption features of Mg, Fe, Ca, and Hα, extending outside the planet’s Roche lobe.  Studying these atomic signatures can directly trace the escaping atmosphere and constrain the thermal processes in the upper atmosphere. To understand these features, we construct a sophisticated forward model by expanding the capability of the exoplanet hydrodynamic atmosphere code introduced in Koskinen et al. 2013, to include important processes of atomic metal species and excited hydrogen.  Using this model, we can reproduce and interpret detected atomic features in the transmission spectrum of WASP-121b self-consistently.

TITLE: Peering at Hazy Worlds Near and Far Through Laboratory Experiments

april 4, 2022   |   12 pm noon   |   hybrid (zoom + SO N305)

sarah moran, university of arizona (LPL)
ABSTRACT

Photochemical hazes are found across the Solar System and in exoplanetary atmospheres, with important effects on atmospheric chemistry and subsequent possible impacts on observations. These affect current observations from Hubble, future observations from JWST, as well as potential upcoming planetary missions. I will present results of the composition of haze particles produced from exoplanet and Triton laboratory studies in the JHU PHAZER laboratory. With high resolution mass spectrometry, we detected many complex molecular species in the haze particles, including those with prebiotic applications. We also measured the haze particles’ spectra with visible-infrared spectroscopy. Our experimental exoplanetary haze analogues exhibit diverse physical properties, which may help us understand their role as potential cloud condensation nuclei and their role in subsequent atmospheric evolution. The Triton experiments reveal the unexpected role of carbon monoxide and its effect on haze formation in Triton’s atmosphere and beyond. Finally, I will discuss how we can apply what we’ve learned from the laboratory into atmospheric models for existing and future observations of sub-Neptune-sized exoplanets as well as Neptune’s moon, Triton.

Towards Quantifying Habitability: Progress Update from the NExSS QuantHabitability Science Working Group

april 11, 2022   |   12 pm noon   |   Zoom

Dániel Apai, University of Arizona, NExSS/Alien Earths Team
ABSTRACT
Exoplanet habitability plays a central role in the future of exoplanet exploration and the science cases for ambitious ground- and space-based telescopes. As habitability depends on many factors – some of which are observable, while others are not – establishing the likelihood of a given’s planet habitability based on remote sensing data remains challenging. At the same time, there is an increasing urgency for a self-consistent framework that provides a quantitative approach to habitability, to inform trades and strategies for possible future mission concepts. The NASA Nexus for Exoplanet System Science (NExSS) Research Coordination Network launched a science working group to integrate community input and work toward developing a quantitative framework for habitability. In this talk, I will present an overview of the QuantHab SWG’s work and review its plans for the next year. Following the presentation, we will discuss the context and challenges of assessing habitability and considerations for a quantitative framework.

Exploring the chemical diversity of sub-Neptune planets

april 18, 2022   |   12 pm noon   |   Zoom

andrea guzman mesa, University of bern

 

ABSTRACT
The atmospheres of sub-Neptunes are expected to exhibit considerable chemical diversity, beyond what is anticipated for gas-giant exoplanets. In my talk, we explore self-consistent atmosphere-interior models of sub-Neptunes to explore this chemical diversity and apply this knowledge to the available atmospheric data of GJ 436b and link it with the corresponding plausible internal structures a presented in Guzmán-Mesa et al 2022. 

 

DEBATE: WHAT DO SHORT-LIVED RADIONUCLIDES TELL US ABOUT THE BIRTH OF THE SUN?

april 25, 2022   |   12 pm noon   |   Zoom

Steve Desch (ASU) & Sasha krot (univ of hawaii)

ABSTRACT

Meteoritic data is an exquisite tool for probing the conditions and events surrounding the early Solar System. An especially important clue to the Sun’s astronomical birth environment is the inference from meteorites that a dozen or more short-lived radionuclides (SLRs), with half-lives ~0.1-10 Myr, existed in the early Solar System. The discovery (Lee et al. 1976) of 26Al in the solar nebula immediately spawned theories (Cameron & Truran 1977) that the Sun had to have formed near a supernova. That image, though inaccurate, remains embedded in astronomers’ minds. But how should we interpret the meteoritic data?

Astrophysical models for the Sun’s formation today tend to fall into three camps. In “inheritance” models, the SLRs were all inherited from the Sun’s molecular cloud, which was likely enriched in SLRs by multiple generations of ‘nearby’ massive stars (supernovae, and especially Wolf-Rayet winds). In “injection” models, at least some SLRs were injected late into the collapsing molecular cloud, or even protoplanetary disk, by a single massive star (supernova or Wolf-Rayet wind). In “irradiation” models, at least some SLRs were created in the protoplanetary disk, by nuclear reactions involving Solar Energetic Particles.  

These models predict different outcomes for the SLRs in meteorites. In “inheritance” models, all SLRs were present from the earliest times in the solar nebula, and spatially uniform. The abundances of SLRs in meteoritic components should reflect their time of formation. In “injection” models, temporal and possibly spatial heterogeneities in injected SLRs are predicted, with some isotopes (26Al and 60Fe) present before the injection but absent before. High abundances of 60Fe would demand such models.  In “irradiation” models, SLR abundances, especially that of 10Be, should be higher near the Sun and likely decrease in time. 

Determining which model(s) applies to the Solar System depends on answer three questions about three key SLRs in meteorites:

  1. What was the level of 60Fe (t1/2 = 2.6 Myr) in the early Solar System?  If closer to 60Fe/56Fe ~ 10-6, this would imply injection from a nearby supernova. A level closer to 60Fe/56Fe ~ 10-8, would be consistent with inheritance. 
  2. Was 26Al (t1/2 = 0.7 Myr) homogeneously distributed across time and space in the solar nebula? The existence of meteoritic components with very low 26Al/27Al, and/or big variations in different reservoirs, would appear more consistent with injection. 
  3. Was 10Be (t1/2 = 1.4 Myr) homogeneously distributed across time and space in the solar nebula? Variations would imply an important role for irradiation. 

 

Renowned meteoriticist Sasha Krot (U. Hawaii) and (mostly) astrophysicist Steve Desch (Arizona State) will offer different perspectives on the current answers to these questions.

Steve’s starting position is that the SLRs are overwhelmingly attributable to inheritance from the molecular cloud, with a very limited role for irradiation in the solar nebula, and essentially no role for injection. Previous inferences of a high abundance 60Fe/56Fe~10-6 were incorrect, and more recent inferences of 60Fe/56Fe~10-8 are correct. He would characterize the meteoritic components with low 26Al/27Al as being rare and in other ways atypical. The 10Be/9Be ratios in meteoritic components are not just predominantly uniform, but entirely consistent with a single homogeneous value, despite claims made about few inclusions. Steve would say the abundances of SLRs in the molecular cloud were set by a combination of Galactic Chemical Evolution plus self-enrichment by generations of previous massive stars in the same spiral arm, especially by Wolf-Rayet winds. The SLR abundances in different meteoritic components tend to comply with a single, consistent chronology. 

Sasha’s starting position is that SLRs may be mostly determined by inheritance, but that the molecular cloud had spatial and temporal variations of SLRs due to injection of material into it, translating into heterogeneities in the disk. He also would agree that inferences of 60Fe/56Fe ~ 10-8 are correct, making a Wolf-Rayet wind more likely than a supernova to be injecting material. But Sasha is more likely than Steve to interpret the refractory Ca,Al-rich inclusions (CAIs) lacking 26Al to be widespread (e.g., >85% of CH CAIs), reflecting a true temporal (or spatial) heterogeneity in the disk. Likewise, Sasha attaches more significance to the findings of heterogeneous 10Be/9Be in CAIs. Sasha therefore sees a potentially significant role for injection and irradiation in the solar nebula. 

Steve and Sasha may or may not come to an agreement on these issues, but the hope is that the audience walks away with a greater appreciation of the state of the field: what are the likely astrophysical models; how is meteoritic data collected and what are the current interpretations; and especially, what research in the near term could settle the debates

understanding the carbon inventory pf terrestrial planets: earth’s depletion and implications for habitable planets

may 2, 2022   |   12 pm noon   |  hybrid (zoom + SO N305)

fred ciesla (Alien earths team, University of Chicago)
ABSTRACT
The bulk composition of a planet, and the accessibility of key molecules and elements at its surface will be critical in determining whether a biosphere can develop and be maintained.  Water has long been recognized as an important ingredient for the formation and maintenance of life, and thus is the basis for defining the Habitable Zone for planets around a star.  However, life requires access to many other molecules and elements, and their abundances must also be factored in when determining whether a planet may be suitable for life.  The Bulk Silicate Earth (BSE) exhibits a clear elemental depletion trend, with the abundance an element decreasing with decreasing condensation temperature.  This holds for carbon, whose abundance is very low in the BSE.  In this talk, I’ll review Earth’s carbon deficit and discuss the processes that may have operated during planet formation to define it.  I will then discuss what this may mean for carbon inventories of other planets, particularly terrestrial planets which formed in the Habitable Zones of their host stars.  

Observational constraints on the chemical complexity and evolution of low mass starless and prestellar core

may 9, 2022   |   12 pm noon   |   hybrid (zoom + SO N305)

samantha Scibelli
steward observatory, University of arizona

ABSTRACT: 

Before a low-mass (M ≤ few solar masses) star like our Sun is formed, it is conceived inside a cold (~10 K) and dense (> 105 cm-3) region of gas and dust known as starless or dynamically evolved prestellar core. It is essential to study the chemical complexity and evolution of prestellar cores because they set the initial conditions of star and planet formation. Observations of complex organic molecules (COMs) in prestellar cores has sparked interest in the star formation community due to the astrochemical and astrobiological implications. I will discuss my observations and abundance measurements of COMs in prestellar and starless cores in the Taurus Molecular Cloud, the prevalence of which support the idea that some COMs are seeded early on before the formation of protostars and planets. I also will discuss my recent modeling efforts to pinpoint the exact evolutionary states of a subset of these cores. Outside of Taurus, it is still unclear how abundance and evolutionary trends hold for prestellar cores in different environments. I will present early results from a new COM survey in the Perseus and Aquila molecular clouds that targets more than 50 starless cores. I stress that studying the limits of chemical complexity in prestellar cores is crucial for tracing how COMs are inherited from a cold core to a planetary system.

A Bayesian, population level approach to constrain planet formation based on ALMA disk measurements

may 10, 2022 (special origins talk)   |   12 pm noon   |  hybrid (zoom + LPL309)

REmo burn, MPIA, heidelberg
 

ABSTRACT

A planet formation model can only be tested against observations if the initial properties of the protoplanetary disk are constrained. The most robust data is however obtained for evolved Class II objects with ages around 2 Myr. After a brief review of recent advances in population synthesis models, I focus on a Bayesian retrieval study of initial conditions and unknown parameters like the strength of viscous turbulence. We based the retrieval on observations of disks in young clusters on the ALMA continuum millimeter flux and accretion luminosity plane. As forward model, we use a neural net trained on 100’000 realizations of a viscous disk model including dust evolution and planetesimal formation. Within this framework, we find preliminary posterior distributions of key quantities describing the disks and can therefore constrain the stage for planet formation. Our Bayesian framework is well suited to produce distributions of parameters which can be used in future planet formation studies.

The Long and Short of It: the Population of Earths, from Short Periods to the Habitable Zone

may 16, 2022   |   12 pm noon   |   Zoom

Galen bergsten (LPL, Universit of Arizona, Alien earths)
ABSTRACT

The search for the “next Earth” requires an understanding of the frequency and distribution of Earth-sized extrasolar planets in the habitable zones of Sun-like stars. Yet a lack of reliable detections for such planets has forced many estimates to be based on extrapolations from the population of planets much closer to their stars. However, these close-in planets might lose their atmospheres due to irradiation from their host stars, causing their distributions to evolve differently than those of planets in the habitable zone. In this talk, I will first discuss the population-level atmospheric evolution of small short-period planets, and consider how this relates to observations of the present-day planet population. I will then introduce a framework which shows how the evolved distribution of these planets is linked to the mass of their host stars, which may provide insights into the dominant mechanism(s) of atmospheric loss. I will also discuss how this characterization of shorter-period planets can be used to constrain the abundance of planets in the longer-period habitable zone, and consider how new estimates might impact future missions to detect and characterize Earth-sized habitable exoplanets.

Postponed to Fall 2022 semester

——— 2022   |   12 pm noon   |   Zoom

NEID team
Postponed to Fall 2022

Previous talks in Spring 2021

Simulating Observations of Protoplanetary Disk Ices

April 12, 2021   |   12 pm noon   |   Zoom
Nick Ballering, University of Virginia

 

Ices play a crucial role in planet formation and the delivery of volatiles to terrestrial planets, yet direct observations of ices in protoplanetary disks have, to date, been limited. Upcoming observational facilities—including JWST, SPHEREx, new SOFIA instrumentation, and potentially OST—will greatly enhance our view of disk ices by measuring their infrared spectral features. I will present a suite of models designed to complement these upcoming observations. The models use a kinetics-based gas-grain chemical evolution code to simulate the distribution of ices in a disk, followed by radiative transfer code using a subset of key ice species to simulate the observations. I will discuss which ice species are readily detectable and how the observable features vary with disk inclination, initial chemical composition, and subsequent chemical evolution. I will also highlight the value of obtaining spatially resolved spectra of edge-on disks (possible with JWST’s integral field units) to constrain the vertical distribution of ices and isolate features from ices closer to the disk midplane.

Understanding Planetary System Formation Through Astrochemistry

April 12, 2021   |   12 pm noon   |   Zoom
ILSE Cleeves, University of Virginia

 

Historically, our understanding of planet formation and the origins of planets’ compositions has been largely informed by our Solar System. However, we are just one system, and now with facilities like NASA’s Kepler and TESS telescopes, we are discovering a wide variety of planet types and architectures, many of which are unlike our own. In the last five years, the Atacama Large Millimeter/Submillimeter Array has simultaneously revolutionized our understanding of planet formation by imaging disks around young stars at high resolution and with high sensitivity. In this presentation, I will discuss how observations of molecular spectral line emission in protoplanetary disks can shed light on 1) the compositions of future planets; and 2) the key physics governing disk evolution during the first few million years of evolution, to help us move toward a more general picture of planet formation, at home and abroad..

Debate: Direct versus Indirect Evidence: Where are the Planets?

April 26, 2021   |   12 pm noon   |   Zoom
During recent years, our field is being transformed by the advent of ALMA, and by the new generation of spectrographs and extreme adaptive optics systems. These instruments observe a rich variety of structure in protoplanetary disks, which are thought to be the birthplace of exoplanets. However, direct detections of young planets are rare. Do young planets exist within these gas rich disks? How common are they? How does the observed disk population relate to the observed exoplanet population around main sequence stars?
The next origins seminar will be an interactive debate where the first steps of planet formation will be discussed.
We will have short presentations by moderators and will spend most of the time for interactive discussions.
If you would like to add a question for the discussion, you can send us one at:

Molecules with ALMA on planet-forming scales

May 3, 2021   |   12 pm noon   |   Zoom
MAPS Collaboration
Speakers: Charles Law (Harvard),  Alice Booth (Leiden), Jenny Calahan (University of Michigan), and John Ilee (Leeds).                
Abstract:
Planets form in the dust and gas rich disks around young stars. Observations of molecular emission in these disks informs our understanding of the elemental composition of planets as well as the physical conditions in the planet forming environment. The ALMA Large Program Molecules with ALMA on Planet-forming Scales (MAPS) is designed to expand our understanding of chemistry during planet formation by exploring disk chemical structure down to 10 au scales. The program focuses on high spatial resolution observations of five disks – IM Lup, GM Aur, AS 209, HD 163296, and MWC 480, and targets over 40 molecular lines from 20 species. This seminar will highlight key results from MAPS, focusing on substructure in the gas, disk winds, physical and chemical disk modeling, and observations of organic molecules.

 

Visible high-contrast imaging of young stellar systems

May 10, 2021   |   12 pm noon   |   Zoom
Sebastian Haffert, University of Arizona
ABSTRACT: 
In the past decade multiple high-contrast imaging instruments have done surveys of stellar systems. Most of these observations have been targeting the (near) infrared wavelength range. Few observations have been done at optical wavelengths. The commissioning of the Laser Tomography Adaptive Optics (LTAO) system together with the integral-field spectrograph MUSE on the VLT enables novel observation of young stellar objects. In this talk I will give an overview of our recent results where we searched for accreting proto-planets in circum-stellar disks, characterized accreting sub-stellar companions and probe stellar outflows down to AU scales.

Me and my neighbors. Protoplanetary disk evolution with external disturbances

May 24, 2021   |   12 pm noon   |   Zoom
Carlo Manara, ESO

 

ABSTRACT: 

In the last years we have expanded our understanding of when, where, and how planets form. In particular, we are starting to constrain the timescale on which planets form, and to have a better understanding of the properties of their natal disks. Whether these properties of protoplanetary disks are similar in different stellar environments is still matter of debate. The mechanisms driving disk evolution, which are tested by combining spectroscopic and millimetre observations of disks and their stars, can be different in more massive clusters with respect to the nearby low-mass star-forming regions. In this talk I will focus on how we can test disk evolution in dense and massive environments by studying protoplanetary disks around multiple stellar systems with ALMA, the accretion rate to disk mass relation in regions with on-going external photoevaporation, and spatially resolved IFU VLT/MUSE data on proplyds in the Orion Nebula Cluster.