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), Allison Towner (SO), Zarah Brown (LPL), Dingshan Deng (LPL), 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, towner at arizona.edu, zbrown at lpl.arizona.edu, dingshandeng at arizona.edu, shuokong 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!

Fall 2024

OSIRIS-REx: Insights from the Asteroid Bennu and Initial Analysis of the Returned Samples

August 26, 2024 | 12 pm noon (MST) | Hybrid (Kuiper 309 & Zoom)

Dante Lauretta, University of Arizona (LPL)

ABSTRACT

The OSIRIS-REx mission has been a pivotal step in our understanding of near-Earth asteroids and the early solar system. This presentation will delve into the mission’s journey to Bennu, the challenges faced in collecting samples, and the wealth of data returned. It will highlight key findings from the initial analysis of the samples, offering insights into Bennu’s composition and its implications for theories on the formation of the solar system and the origins of life.

OSIRIS-REx Project: https://osirisrex.arizona.edu/

TBD

November 25, 2024 | 12 pm noon (MST) | Hybrid (SO N305 & Zoom)

Arvind Gupta, NOIRLab

ABSTRACT

TBD

December 02, 2024 | 12 pm noon (MST) | Hybrid (Kuiper 309 & Zoom)

Tatsuya Akiba, University of Colorado Boulder

ABSTRACT

TBD

December 9, 2024 | 12 pm noon (MST) | Hybrid (SO N305 & Zoom)

Gabriel Weible, University of Arizona

ABSTRACT

Previous Talks

Spring 2024

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.

Super-Earths are Common in Jupiter-like Orbits

april 09, 2024 (TUESDAY) | 12 pm noon (MST) | Hybrid (SO 550 & Zoom)

weicheng zang, cfa

ABSTRACT

Super-Earths and mini-Neptunes are absent in the relatively planet-rich Solar System, but the transit and radial velocity methods have demonstrated that they are common in short-period orbits. The standard core accretion planet formation theory predicts numerous “failed gas giant cores” in the wide orbits (>~ 1 AU), with masses of Super-Earth/mini-Neptune masses. The gravitational microlensing technique is currently the only method that can probe low-mass wide-orbit planets, but before 2020 such planets were barely detected, indicating a paucity of “failed gas giant cores”. Since 2020, I have been leading two projects to capture “failed gas giant cores”, which detected about 10 planets smaller than the detection record by 2020, suggesting that “failed gas giant cores” are common (about 1 per star). I will also introduce the statistical result from the largest microlensing planetary sample, from Earths to super-Jupiters, and the future missions for microlensing planets.

REscheduled

april 15, 2024 | 12 pm noon (MST) | Hybrid (kuiper 309 & Zoom)

sarah moran, lpl, University of arizona

ABSTRACT

Fall 2023

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

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

finding atmospheres on m dwarf terrestrial planets with jwst

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

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

march 27, 2023 | 12 pm noon (MST) | Hybrid (SO N305 & Zoom)

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

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

(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 NASA’s 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 observatory’s time—which 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 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.

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.

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.

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:

What was the level of ⁶⁰Fe (t_1/2 = 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.
Was ²⁶Al (t_1/2 = 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.
Was ¹⁰Be (t_1/2 = 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!

Zoom link

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.

Zoom link

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

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.

Talk video

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..

Zoom link

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:

https://docs.google.com/forms/d/e/1FAIpQLSd36f3fD8W6FPslhhIciYm3bMX8KlO-4w-cOWQM0ngfxXpHDw/viewform?usp=sf_link

Zoom link

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.

Talk video

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.

Talk Video

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.

Zoom link