Spring 2025 IfA Colloquia
Talks home
Date
Speaker
Affiliation
IfA Host
Title (click for abstract)
Jan 13 (M)
IfA Hilo
Momen Diab
University of Toronto
Magnier
Jan 22 (W)
1:45pm
Jan 22 (W)
IfA Hilo
Angelo Ricarte
Harvard University
Chun
Jan 27 (M)
Marta Bryan
University of Toronto
Huber
Jan 30 (Th)
Kartheik Iyer
Columbia University
Liu
Jan 31 (F)
Feb 6 (Th)
Rohan Naidu
MIT
Sanders
Feb 18 (Tu)
Max Goldberg
Observatoire de la Côte d’Azur
Magnier
Feb 20 (Th)
Vadim Semenov
Harvard University
Bresolin
Feb 24 (M)
Neige Frankel
CITA
Huber
Feb 25 (Tu)
Feb 27 (Th)
IfA Hilo
Michael Tucker
Ohio State University
Baranec
Mar 3 (M)
IfA Hilo
Nour Skaf
UC Santa Cruz
Chun
Mar 4 (Tu)
Apr 2 (W)
Songhu Wang
Indiana University
Dai
Apr 9 (W)
Peter Vereš
CfA | Harvard & Smithsonian
Jedicke
Apr 16 (W)
Jane Lixin Dai
University of Hong Kong
Shappee
Apr 23 (W)
Juraj Lorincik
BAERI
Reep
Apr 30 (W)
Yeimy Rivera
CfA | Harvard & Smithsonian
Reep
May 9 (F)
Branden Allen
UH SSEI
Simons
May 15 (Th)
Rohan Naidu
MIT
Huber
May 16 (F)
Sebastien Vievard
UH SSEI
Bottom
May 21 (W)
Rob Jedicke
UH IfA
Meech
Talks are held at 11:45am HST in the IfA Mānoa Auditorium (C-214) unless otherwise noted.
For additional information, please contact Dr. Fabio Bresolin.
The rise of astrophotonics: Integrated optics for stellar interferometry, spectroscopy, and adaptive optics
Momen Diab
Postdoctoral Fellow
University of Toronto
Website
Integrated astrophotonic devices offer solutions to the growing complexity challenges faced by conventional astronomical instrumentation, especially for the upcoming extremely large telescopes (ELTs) and dense optical arrays. Photonic spectrographs, integrated beam combiners, aperiodic Bragg grating filters, and other innovations have been developed to overcome the limitations of bulk optics. In this talk, I will tell the origin story of astrophotonics and showcase the state-of-the-art integrated instruments under research, including my contributions. I will conclude by outlining strategies to advance the readiness level of key technologies needed for realizing adaptive optics-assisted optical telescope arrays.
TBA
Momen Diab
Postdoctoral Fellow
University of Toronto
Website
Driven largely by advancements in the telecommunications industry, multiple platforms have been developed for light processing in miniaturized structures. Photonic integrated circuits, featuring waveguides and micrometer-scale components on chips, can transport, combine, filter, and disperse light with high stability, modularity, and replicability. Similarly, fiber-based devices, such as photonic lanterns, enable efficient light collection at the focal plane of telescopes and seamless integration with other integrated and bulk instruments. In this seminar, I will discuss the advantages these technologies present for astronomy and the challenges they must overcome before on-sky deployment. I will also provide insights into their design, fabrication, and testing processes.
Bridging the universe with stars
Kathryn Grasha
Research Fellow
Australian National University
Website
Massive stars within young star clusters underpin galaxy evolution physics. Massive stars shape their environments through mechanical feedback, ionisation, and heavy element enrichment of the interstellar medium (ISM). Yet, our understanding of these stars’ chemical composition, especially at low metallicity, remains uncertain. This limits our ability to quantify how they interact with the ISM and the resulting emission line observables. By quantifying chemical abundance ratios over cosmic time and integrating them into stellar and photoionisation models self-consistently, we are starting to accurately predict galaxy properties across epochs. In this presentation, we will merge stellar models with observations of star forming regions, linking the formation of stars to the global galactic environment. We will explore significant knowledge gaps, paving the way to quantify energy, metal, and matter flows on 10 parsec scales. Additionally, we highlight how JWST observations are addressing the disparity between local and high-redshift realms. We’ll end by demonstrating how this work establishes a foundational framework for future investigations with ELTs, which will enable detailed characterisations of resolved stellar populations beyond our cosmic neighbourhood.
Galaxy evolution through the eyes of resolved, multi-wavelength star formation observations
Kathryn Grasha
Research Fellow
Australian National University
Website
In this talk, I will discuss the TYPHOON survey, the largest nearby sample of galaxies with 3D data cubes which will be used as a benchmark to calibrate the models and quantify the impact of variable stellar chemical abundances on emission lines. The combination of this new spectral library and local galaxies to calibrate and create first robust and self-consistent set of chemical abundance diagnostics will allow for the removal of discrepancies in the evolution of the global metallicity over cosmic time. The work presented here represents a first step necessary in order begin providing clear constraints for galaxy evolution theory by combining observations and state-of-the-art modelling as the theoretical basis to derive new, robust galaxy diagnostics across cosmic time.
The Cosmic Assembly of Supermassive Black Holes—A Journey from Microparsecs to Megaparsecs
Angelo Ricarte
Black Hole Initiative (BHI) Fellow
Harvard University
Website
The past decade has featured major advances in supermassive black hole (SMBH) astrophysics: from the gravitational wave background, to glimpses at cosmic dawn, to the first spatially resolved SMBH images. These observations, in tandem with theoretical advances on both event horizon and galactic scales, have spurred progress on longstanding problems in black hole seeding, accretion, feedback, and dynamics. I will first discuss SMBH imaging with the Event Horizon Telescope (EHT), a worldwide network of millimeter observatories, and how we use these images to infer strong magnetic fields that transform the accretion flow. I will then introduce Serotina, a flexible semi-analytic modeling framework for the black hole-galaxy co-evolution on cosmological timescales. I use this cosmological framework to self-consistently predict multi-messenger observables including spin distributions, high-redshift luminosity functions, and gravitational wave events. Bridging disparate spatial scales, we will explore the cosmological-scale implications of the strongly magnetized accretion disks implied by event horizon-scale studies. As new observatories like BHEX, LISA, and AXIS go online in the next decade, this multi-scale theoretical approach will enable us to construct a complete picture of SMBH evolution over cosmic time.
A New Spin on Black Holes in a MAD Universe
Angelo Ricarte
Black Hole Initiative (BHI) Fellow
Harvard University
Website
Recent spatially resolved polarized images of accreting black holes via the Event Horizon Telescope (EHT) have led to advances in the theory of accretion and jet launching. These studies prefer Magnetically Arrested Disk (MAD) accretion flows over their more weakly magnetized Standard and Normal Evolution (SANE) counterparts. Such models generate efficient jets via the Blandford-Znajek (BZ) mechanism, which extracts the spin-energy of the black hole. In this talk, we explore the cosmological implications of MAD accretion flows. First, using general relativistic radiative magnetohydrodynamics (GRRMHD) simulations, we develop new “sub-grid” formulae for BZ jet feedback and spin evolution, appropriate for both semi-analytic models and cosmological simulations, for arbitrary spins and accretion rates. Then, we implement these formulae in the semi-analytic model Serotina, which evolves a cosmological population of supermassive black holes from the seeding epoch (z~20) to the present day. We demonstrate that spin-down in a MAD universe due to BZ jets has an observable effect moderating SMBH spins across cosmic time. Forward modeling different selection effects, we demonstrate how this effect manifests in spin distributions accessible via X-ray reflection spectroscopy, extensions to the EHT, or the Laser Interferometer Space Antenna (LISA).
Exo-Jupiters: The Movers and Shakers of Planetary Systems
Marta Bryan
Assistant Professor
University of Toronto
Website
Understanding what formation processes produce the extraordinary diversity of planetary systems that we see today is one of the driving questions in the field. Of all the new planets that have been discovered, gas giants are the easiest ones for us to find—they are bigger, brighter, and more massive than any other kind of planet. This means that they are ideal targets for characterization techniques that can tell us about the planet formation process, and they are so massive that they dominate the dynamics of their systems, impacting the formation of other planets. Gas giants are an obvious place for us to start if we want to learn about the physics of planet formation.
In this talk I will describe my work using multiple observational techniques to explore the formation and evolution of gas giants. I will discuss how targeting directly imaged planets with high-resolution spectroscopy enables measurements of new planetary properties like rotation rates and obliquities. These provide fundamental insights into the physics of gas giant formation, such as the evolution of planetary angular momentum. I will describe how radial velocity searches for Jupiter analogs in systems with known inner planets reveal the impact gas giants have on the inner architectures of planetary systems, and are a key step in the search for life on other planets. Finally, I will preview compelling future directions and emphasize the importance of broad telescope access to the success of this program.
Reading stories written in starlight: Understanding what shapes the past lives of galaxies with novel astrostatistical methods
Kartheik Iyer
NASA Hubble Fellow
Columbia University
Website
The light from galaxies that we observe with telescopes on the ground and in space contains emission from its component stars, gas and dust. The spectra (or spectral energy distributions; SEDs) of galaxies therefore tell us stories of how galaxies form and evolve over time, and help us understand the complex processes that regulate galaxy growth over vastly different spatial and temporal scales. Modern galaxy surveys have observed millions of galaxies (and counting!) with unprecedented sensitivity across a wide range of wavelengths, enabling the reconstruction of galaxy star formation histories (SFHs). Meanwhile, large cosmological hydrodynamical simulations help us connect the physical processes that shape galaxies (cosmological accretion, feedback and baryon cycling, mergers, and more) to the imprints they leave in galaxy SFHs.
My research focuses on building a new temporal picture of galaxy evolution by developing novel mathematical frameworks and computational tools to extract information from observations and connect them to theoretical models. I will discuss how this work (i) has led to the development of new methods and data products (Dense Basis, GP-SFH, Katachi) that are valuable to the wider scientific community, (ii) is being applied to observations from JWST, leading to exciting discoveries about how galaxies form stars in the early universe, and (iii) will address the unique challenges (and opportunities!) posed by large, noisy datasets from upcoming observations. While it is always an exciting time to be an astronomer, recent advances in the adjacent fields of astrostatistics and machine learning have opened up new windows for us to identify subtle signals in large populations of galaxies. As we prepare for the next generation of astronomical facilities, these methods—and the interdisciplinary approaches they represent—will be crucial for understanding how galaxies like our Milky Way came to be.
Navigating the astronomical literature with Pathfinder, and the power of interpretable machine learning
Kartheik Iyer
NASA Hubble Fellow
Columbia University
Website
Astronomy literature is vast and difficult to keep track of, a task made more difficult by its insistence on expanding at an ever accelerating rate. I will talk about Pathfinder (https://pfdr.app), a use-case that shows how large language models can be used in conjunction with archival data from arxiv.org and the astrophysics data system (ADS) to provide a complementary approach to finding relevant papers or answer questions based on these papers (thus minimizing the risk of hallucinations). I will also talk about the intermediate space of embeddings that makes exploration in this space possible, and touch upon the role of intermediate spaces and interpretable methods in model building across astronomy.
Alien Skies Under Active Suns
Michael Zhang
Postdoctoral Scholar
University of Chicago
Website
Exoplanet atmospheres are exciting laboratories to probe unique chemical and physical processes in a regime not accessible elsewhere in the universe. Through observations and modelling, I probe the conditions and evolutionary processes on a wide variety of worlds. Small rocky planets orbiting M dwarfs are our only chance of finding exoplanetary biosignatures in the near future, but whether they can even hold on to atmospheres is unknown. To find out, I use JWST thermal emission observations of their day and night sides to look for atmospheric circulation. Their bigger mini-Neptunes cousins, with radii and densities between that of Earth and Neptune, are unlike any planet in the solar system. My multi-wavelength all-sky survey of atmospheric escape from young and intermediate-age mini-Neptunes shows that they have primordial atmospheres which are quickly being photoevaporated, potentially transforming them into a smaller, denser class of planet within a few Gyr. These observations constrain the efficiency of mass loss, the atmospheric metallicity, and the planetary magnetic field, the last of which is difficult to constrain in any other way. In the final part of my talk, I will highlight the importance of open-source software—especially my atmospheric retrieval code PLATON—to studying planets of all types, from super-Earths to mini-Neptunes to hot Jupiters. I will also synergize the different aspects of my research to offer a vision for the future of biosignature searches.
Preliminary Ponderings from a Pulsar “Planet” Program
Michael Zhang
Postdoctoral Scholar
University of Chicago
Website
PSR J2322-2650b is a Jupiter-radius, Jupiter-mass companion to a millisecond pulsar, with temperatures typical of a hot Jupiter. Because its pulsar host is invisible in the infrared, it is the only externally irradiated “hot Jupiter” in the universe where high SNR (>100 at R>100) spectra are possible. We used JWST’s NIRSpec/PRISM (0.7–5.2 μm) to monitor the planet’s spectrum across an entire orbit, and NIRSpec/G235H to obtain a higher-resolution 1.7–3.1 μm dayside snapshot. These observations completely dispel any notion that the planet is a hot Jupiter analog, revealing a mind-bogglingly bizarre spectrum with no similarity to any known planet—a spectrum which raises as many questions as it answers about the object’s formation. This talk is the tale of how a group of both exoplanet and neutron star experts are working together to understand this unique planet. We are studying the planet’s chemistry, circulation, and formation, while simultaneously addressing long-standing questions in high-energy astrophysics surrounding the origin of black widow systems, the spin-up of millisecond pulsars, and possibly the equation of state of neutron stars. I will talk about our successes so far, as well as the challenges that lay ahead.
The First Glimpse of the First Galaxies with the James Webb Space Telescope
Rohan Naidu
NASA Hubble Fellow
MIT
Website
The first billion years after the Big Bang mark the last major uncharted epoch of the Universe when the first galaxies emerged to transform the cosmos. They illuminated the invisible scaffolding of dark matter, they ionized the intergalactic reservoirs of hydrogen, and they synthesized the elements that would one day seed life on Earth. My research group will finally reveal these enigmatic sources and the great transformations they wrought on the universe. In this talk I will present early steps in this direction through experiments I am leading with NASA’s flagship James Webb Space Telescope. First, I will discuss a new class of surprisingly luminous early galaxies at the current redshift frontier (z~10-14; <400 million years after the Big Bang), the challenges they pose for theoretical models, and the new path they present to push to previously unimaginable epochs of z~15-20 — the era of very first star-formation. Next, as a case study of the “unknown unknowns” awaiting discovery in the early Universe, I will discuss the surprisingly abundant population of “Little Red Dots” that are driving a revolution in our understanding of the origins of supermassive black holes. Finally, I will describe novel strategies exploiting gravitational lensing to seek pristine metal-free Pop III stars, and to hone in on the elusive protagonists of cosmic reionization, the last large-scale process that touched almost every baryon in the universe. Throughout, I will outline how Hawaii’s unique strengths coupled with new capabilities offered by JWST, Roman, and the ELTs promise a once-in-a-generation expansion of the astrophysical frontier to the brink of the Big Bang.
The Milky Way—An Immigrant Story
Rohan Naidu
NASA Hubble Fellow
MIT
Website
Galaxies like our Milky Way are predicted to grow by assimilating smaller, immigrant galaxies. The outer reaches of our Galaxy—the stellar halo—are predicted to be the melting pot for stars that were born elsewhere, but now call the Milky Way their home. Despite being scattered across the Galaxy, immigrant stars retain memory of their common origin that may be accessed via their shared chemistry and dynamics. The long-held aspiration of tracing every halo star to a distinct accreted galaxy has only recently become possible thanks to the Gaia astrometric mission. In this talk I will present a comprehensive inventory of our Galaxy, mapping debris from various known as well as previously undiscovered dwarf galaxies, including the most distant sample of halo stars with constrained orbits ranging out to 150 kpc. I will discuss two key opportunities arising from these surveys: (i) star-by-star access to the stellar chemistry of “high-redshift” galaxies, since the star-formation in these ancient systems was abruptly truncated when they were assimilated by our Galaxy; (ii) reconstructing the detailed dark matter distribution of the Milky Way as a sum of a now well-known series of mergers. In only five years with Gaia, the number of massive (>million M☉) dwarfs discovered in the stellar halo has exceeded the classical Milky Way satellites of comparable size—I will discuss how the coming few years with large-scale surveys promise to be a remarkably transformative one for astronomy at the edge of the Galaxy.
Resonance Locking and Hot Jupiters
J. J. Zanazzi
51 Pegasi b Postdoctoral Fellow
UC Berkeley
Website
Fluid dynamics set exoplanetary system architectures. The gravity from planetary and binary companions sculpts the natal disk, and tidal interactions between planets and their host star affect spins, eccentricities, and inclinations. Hot Jupiters, in particular, are strongly influenced by tidal dissipation. These planet orbits are often misaligned with their host star equators due to their tumultuous past, but only for hot hosts: cool hosts are predominantly aligned. Prior attempts to explain this correlation between stellar obliquity and effective temperature have proven problematic. We discuss how resonance locking—the coupling of the planet’s orbit to a stellar gravity mode (g-mode)—can preferentially damp the obliquities of cool stars. The radiative cores of cool stars support internal gravity waves, that drive strong tidal dissipation and damp obliquities. Future avenues of investigation for tides in stars, and seismic oscillations in planets, are discussed.
Tilted Protoplanetary Disks
J. J. Zanazzi
51 Pegasi b Postdoctoral Fellow
UC Berkeley
Website
Planetary nurseries birth orderly systems, with flat protoplanetary disks forming circular and co-planar exoplanetary orbits. The dynamically quiet architectures of the Kepler and TESS exoplanets, and the co-planar rings of the ALMA protoplanetary disks, favor uneventful upbringings. The host star, however, does not always share this tranquil history, and can have its equator highly misaligned with the orbits of its planets. In this talk, we discuss how an inclined stellar companion can create a ruckus by tilting planet-forming disks. The companion torques the disk, causing the disk’s angular momentum to continuously change direction. Stars become misaligned only when they are weakly tethered to the disk. Star-disk coupling decreases with age as the disk loses mass, but never decouples if a hot Jupiter forms before disk dispersal. Companions misalign warm Jupiters or low-mass planets, a prediction supported by observations. Planned work on star-disk and disk-binary alignment caused by disk dissipation is discussed.
Lighting up Supermassive Black Holes
Brenna Mockler
Carnegie CTAC Postdoctoral Fellow
Carnegie Observatories
Website
The supermassive black holes at the centers of galaxies power the most energetic phenomena in the universe and evolve alongside their hosts, but much remains unknown about their origins and growth. One of the most promising avenues for studying supermassive black holes is through the tidal disruption of stars that orbit too close to the black holes. These ‘tidal disruption events’ light up hidden supermassive black holes and encode information about the properties of both the black holes and their environments. While these flares have long been theoretically predicted, it is only in the past ~decade that they have been discovered observationally, and the number of detections is about to explode with the onset of LSST. I will show how modeling the light curves and spectra of tidal disruption events allows us to probe the black hole mass function, the formation channels of supermassive black holes, and the limits of black hole growth.
Exploring Galactic Nuclei with Tidal Disruption Events
Brenna Mockler
Carnegie CTAC Postdoctoral Fellow
Carnegie Observatories
Website
Tidal disruption events provide windows into the hearts of galaxies, teaching us about stellar and galaxy evolution at size scales that are difficult to probe observationally outside our own galactic neighborhood. For example, recent observations of these transients have shown evidence for higher mass and higher metallicity stellar populations in the centers of galaxies—suggesting that the dense, dynamic galactic nuclei environment influences the birth and evolution of stars. The rates of these transients also probe the shape of the galactic potential. This includes the steepness of the stellar cusp and asymmetries in the nuclear cluster, resulting, for example, from the presence of a hidden supermassive black hole binary. In these ways, TDEs connect the environment around the supermassive black hole to large-scale changes in the galaxy such as star formation and merger history, helping us learn about how supermassive black holes grow and evolve with their galaxies.
Early Dynamics of Compact Exoplanet Systems
Max Goldberg
Postdoctoral Researcher
Observatoire de la Côte d’Azur
Website
Most of the thousands of discovered exoplanets are billions of years old. However, these planets, and the planetary systems they are a part of, retain distinct fingerprints of how and when they formed. I will present work that aims to uncover the environment in which planets form by investigating how the architectures of multiplanet systems are shaped by physical processes. I show that varying degrees of planet-planet interactions, planet-disk interactions, and tidal dissipation successfully reproduce many bulk features of the small planet census. In particular, resonant chains broken through dynamical instabilities match the orbital and size architectures of many compact Kepler systems. Furthermore, for the small fraction of systems that remain resonant, detailed analysis can recover measurements of the protoplanetary disk environment and orbital histories of the planets.
Self-consistent Models for the Formation of the Terrestrial Planets
Max Goldberg
Postdoctoral Researcher
Observatoire de la Côte d’Azur
Website
The wealth of information available on the terrestrial planets has not translated into a clear theory of their formation. Dynamical models tend to invoke rings of rocky material that, over 100 Myr, accreted into the rocky planets and the asteroid belt. However, chemical and isotopic analyses have demonstrated that the Earth accreted from at least three separate material reservoirs separated in space and time, traces of which are found today in the meteorite population. Our goal is to build a single self-consistent model of the Solar disk evolution, planetesimal formation, and terrestrial planet accretion compatible with all available constraints. We use state-of-the-art dynamical simulations and modern disk paradigms to make testable predictions of the orbital architecture of the Solar System and the chemical and isotopic compositions of planets and small bodies. I will discuss in particular the role of the giant planets in transporting material through the early Solar System to resolve an outstanding issue in the heterogeneity of Earth’s accretion. Finally, while such detailed constraints are not yet available in extrasolar systems, similar mechanisms must shape them.
Modeling Turbulent Formation of First Galaxies and Galactic Disks
Vadim Semenov
NASA Hubble & ITC Postdoctoral Fellow
Harvard University
Website
Over the past few years, our paradigm of galaxy formation has been qualitatively transformed. The JWST has revealed a surprisingly large population of early UV-bright galaxies at redshifts z>10, challenging modern theories of galaxy formation. Observations from JWST and ALMA have also shown that disk galaxies were already common in the early Universe by z>4, implying that disks form much earlier than previously thought (z∼1−2). Closer to home, these high-redshift discoveries can be mapped onto the formation and evolution of our own Milky Way, which can now be traced through chemo-kinematic “archaeological” surveys of nearby stars back to the dawn of the Galactic disk. These local data suggest that the Milky Way disk also formed surprisingly early, by z∼3. In my talk, I will demonstrate how state-of-the-art simulations of galaxies help us solve these puzzles and build a coherent picture of galaxy formation and evolution across cosmic time. In particular, I will highlight the importance of predictive, physically motivated models for key unresolved processes, such as ISM turbulence and turbulence-regulated star formation, which enable us to investigate these processes under the extreme and largely uncharted conditions of the early Universe.
Why Do Galaxies Form Stars Inefficiently?
Vadim Semenov
NASA Hubble & ITC Postdoctoral Fellow
Harvard University
Website
Star formation in galaxies is surprisingly inefficient. Gas in galaxies is converted into stars on timescales tens to hundreds of times longer than any relevant dynamical timescale in the interstellar medium (ISM). I will present a simple physical framework describing the rapid cycling of interstellar gas between dense, actively star-forming, and diffuse, ‘inert’ ISM states. This framework explicitly connects global star formation on kiloparsec scales with the timescales of processes governing gas evolution within individual star-forming regions. I will demonstrate how this framework explains why galaxies form stars inefficiently and how it elucidates the non-trivial dependence of the global star formation rate on star formation and feedback processes in galaxy simulations. Finally, I will show that comparisons of these simulations with high-resolution, multi-tracer observations of the ISM in nearby star-forming galaxies provide invaluable insights into the star formation-feedback cycle.
Not All Those Who Wander Are Lost—Tracing Our Galactic Dynamic History
Neige Frankel
Postdoctoral Fellow
Canadian Institute for Theoretical Astrophysics
Website
Galaxies emerge from random fluctuations, yet their masses, sizes, and morphologies are not randomly distributed, instead occupying a small region of the vast parameter space available. This suggests that physical processes regulated their evolution. But how? The challenge lies in seeing only the final snapshot of our Universe, not its full evolution. The Milky Way is a typical disk galaxy. But it is unique in being our home, allowing us to uniquely collect individual stars positions, motion, ages and composition. These observations hold information about the process that shaped our Galaxy. But extracting this information in a statistically rigorous way requires a stringent data-model comparison framework. I will present the first step of such a framework and how it enriched our understanding of the Galactic disk, revealing that our Galaxy was likely reshaped by migration of stars across its disk. Building on this framework will be crucial to extract quantitative information from imminent large scale surveys, allowing us to see recently formed dynamical structures, marking the beginning of a new era in galactic dynamics and allowing us to address afresh stringent questions in galaxy evolution.
Iron Snails in our Galactic Backyard—Non-equilibrium Dynamics and Spiral Abundance Patterns
Neige Frankel
Postdoctoral Fellow
Canadian Institute for Theoretical Astrophysics
Website
With the explosion of data for our own galaxy from large scale spectroscopic and astrometric surveys, we have never seen the Milky Way in such detail: we can now directly ‘see’ dynamics in action as our disk is shaping itself, thanks to the availability of 6D phase-space information for hundreds of millions of stars. In particular, the recently discovered phase spiral in the vertical motion (the Gaia Snail) carries evidence for vertical phase mixing, departure from dynamical equilibrium, and may shield light on the processes setting the vertical structure of the Milky Way’s disk. I will introduce the Gaia Snail, the Iron Snail, and present different quantitative approaches that we can use to understand our Galaxy’s recent history in detail.
The Golden Era of Transient Astronomy
Michael Tucker
CCAPP Fellow
Ohio State University
Website
The Universe is filled with the eruptive and the explosive. The proliferation of sky surveys over the past decade has revolutionized our view into the temporal Universe with the discovery rate of ‘transients’, events that brighten and fade with time, increasing ten-fold. I will highlight recent results from our efforts to characterize the extreme and exotic occurring in the Universe, and, more importantly, how we can apply these insights across astrophysical disciplines. Finally, I will show some of the novel ways we are re-purposing survey data, such as triangulating ancient supernovae and mapping local interstellar clouds. I conclude by looking to the future, where upcoming ground- and space-based surveys hold enormous potential for probing nearly every aspect of the time-domain sky.
White Dwarf Mergers, Type Ia Supernovae, and Cosmology
Michael Tucker
CCAPP Fellow
Ohio State University
Website
It is widely accepted that the Universe is expanding, and the expansion rate itself is accelerating due to dark energy. Yet the cosmic explosions typically used to measure this expansion, Type Ia supernovae, are poorly understood, leading to questions about their reliability. I will review recent progress on identifying how white dwarfs, the dead cores of low-mass stars, explode as Type Ia supernovae, including the most conclusive evidence to-date that merging white dwarf binaries produce some, but not all, of the Type Ia supernovae used for cosmology. I will briefly discuss the implications of these results, including precision cosmology in the modern era of large-scale surveys, flame propagation in electron-degenerate matter, and milli-Hertz gravitational waves observable by LISA.
Bridging worlds: Enhancing exoplanet imaging beyond the speckle noise
Nour Skaf
Postdoctoral Researcher
UC Santa Cruz
Studying exoplanets’ atmosphere and formation processes is crucial to ultimately find and characterize Earth-like planets. Direct imaging (DI) is key in this endeavor, as it is the only method enabling detailed spectroscopic characterization of exoplanets and circumstellar disks. However, DI remains limited, particularly at small separations, leaving planets in the 5-15 AU range largely undetected due to the limitations of current instrumentation. The dominant obstacle is speckle noise, which creates contrast barriers that obscure faint planetary signals. Most of my work focuses on advancing adaptive optics (AO) and wavefront sensing and control (WFS&C) techniques to overcome these barriers. Specifically, I will discuss the DrWHO algorithm, a focal-plane wavefront correction algorithm, and its applications in improving contrast performance at small angular separations. I validated DrWHO on-sky on Subaru/SCExAO. Alongside instrumental advances, I will highlight my research on planet formation and atmospheric characterization, emphasizing the need for a holistic approach to understanding exoplanetary systems. By improving high-contrast imaging techniques, we will unlock new opportunities to study exoplanet demographics, formation, and atmospheres, in previously inaccessible regions. This will ultimately pave the way for the direct imaging of Earth-like planets with Extremely Large Telescopes (ELTs) and the Habitable Worlds Observatory (HWO).
Bridging gaps: Advancing wavefront control for exoplanet imaging
&
Expanding global access to astronomy
Nour Skaf
Postdoctoral Researcher
UC Santa Cruz
This talk will be divided into two parts.
First, I will focus on wavefront sensing and control (WFS&C), a critical component of high-contrast imaging, aiming at addressing the speckle noise barrier currently limiting exoplanet detection. I will dive deeper into my work on the DrWHO algorithm: a key outcome is the one-to-one mapping from wavefront sensor (WFS) data to the point spread function (PSF). This will enable on-the-fly telemetry processing through reinforcement learning and PSF reconstruction, eventually bridging the gap between WFS&C and post-processing techniques, ultimately opening the door to a new level of speckle suppression. I will describe my work on real-time control accessibility to enhance WFS&C development.
The second part of the talk will focus on my work on astronomy accessibility. Astronomy and space are intrinsically what connect us all, by the very nature of our cosmic origin. However, today, while every single culture in the world was once connected to the stars, emerging countries and underrepresented communities have little to no access to it. I will share some of my experience witnessing how different cultures approach their development of astronomy and space. We will look at a few African and Southeast Asian examples, and highlight how communities, universities, and governments are dealing with the focus of astronomy and space as a tool for development in education, technology, science, and peace-building.
One-minute colloquium
Presented by the IfA Community
Participants will have one (1) slide and one (1) minute to present their research.
For newcomers, this is a great introduction to what goes on at IfA; for others who might’ve been stuck under the ice of Enceladus for the past year, it’s always interesting to see what your peers have been up to recently.
Plus, witness the ruthless truncation as the presentation auto-advances slides after exactly 60 seconds!
The Most Massive Stars
Jeremy Goodman
Professor
Princeton University
The observed masses of stars range from one tenth to one hundred times that of the Sun. The lower mass limit has a clear physical explanation. This is less true of the upper limit, which might vary among star-forming environments. Indeed, supermassive stars at cosmic dawn have been invoked to explain the early appearance of bright AGN. At any redshift, AGN disks are themselves possible birthplaces for very massive stars (VMS). In both cases, however, the arguments are indirect and theoretical; we lack direct observational evidence for VMS. These matters will be reviewed, together with progress in understanding the physical limits to stellar mass, and observational prospects.
The TRGB-SBF Project: A Pop II Path to H0
Brent Tully
Emeritus Faculty
University of Hawaiʻi Institute for Astronomy
The path from Cepheid variables to type Ia supernovae gives a value of the Hubble constant which significantly disagrees with the value determined from observations of conditions in the early universe and a cosmological model. A totally independent measurement of H0 from observed redshifts and distances is needed to evaluate the possibilities of systematic errors. A path is being explored that should be as accurate or better than the Cepheid-SNIa way, involving only observations of old evolved stars. Gaia parallaxes ground the absolute scales of RR Lyrae stars that establish the absolute magnitudes of stars at the tip of the red giant branch that set the scale of the power spectrum of surface brightness fluctuations in E/S0 galaxies that are observed at redshifts with negligible confusion from peculiar velocities. Observations with JWST are fundamental for the success of this program.
Explosive Transients Across the Universe
Tony Piro
Staff Scientist
Carnegie Observatories
Website
Astrophysical transients can become as bright as hundreds of millions or billions of stars for a matter of weeks to months. This allows these cosmic beacons to be viewed across the universe, so that we can study extreme environments in ways that would otherwise be inaccessible to us. Some examples include the last stages of massive star evolution, the birth sites of neutron star binaries, and the regions around black holes that have recently eaten another star. I will describe some of the most exciting recent observations of astrophysical transients and how theoretical models are key for interpreting these events.
Towards a Unified picture of Planet Formation: Successes and Challenges
Songhu Wang
Assistant Professor
Indiana University
IU Faculty Page
While the exoplanetary field is replete with remarkable discoveries, perhaps the two most intriguing findings have been the detection of hot Jupiters—giant planets orbiting perilously close to their parent stars, and the startling abundance of super-Earths—planets with masses between that of Earth and Neptune. The mere existence of these worlds was wholly unpredicted based on the expectations gleaned from centuries of observations of our own solar system. This talk will examine the demographics and orbital architectures of these exoplanets, discussing how the broad variety of observed exoplanetary systems could potentially be understood within a unified theoretical framework, and a significant new challenge that we are facing to understand hot Jupiter formation.
Near-Earth Object Discovery Enhancement with Machine Learning Techniques
Peter Vereš
Astronomer
Center for Astrophysics | Harvard & Smithsonian
Website
Near-Earth Objects (NEOs), defined as asteroids and comets with a perihelion distance <1.3 AU, have been a focus of global interest for over two decades. NASA-funded surveys have predominantly contributed to the discovery of nearly 38,000 NEOs to date, maintaining a steady detection rate of ~3,000 per year—a number expected to increase with upcoming observatories like Vera Rubin and NEO Surveyor. NEOs are primarily identified through the digest2 score, posting to the Minor Planet Center’s NEO Confirmation Page (NEOCP), and rapid follow-up observations. However, ~11% of candidates remain unconfirmed due to insufficient follow-up, and ~30% of NEOCP entries turn out to be non-NEOs, consuming valuable resources.
We analyzed 30 distinct digest2 parameters to refine candidate selection, developing a filtering mechanism that could reduce non-NEOs on NEOCP by 20% while preserving true NEOs. Additionally, we applied four machine learning (ML) techniques—Gradient Boosting, Random Forest, Stochastic Gradient Descent, and Neural Networks—achieving ~95% precision in classifying NEOCP candidates. Our findings suggest optimized criteria that could significantly improve NEO detection efficiency.
Theoretical Insights into Tidal Disruption Events: Rates, Accretion, Emission, and Feedback
Jane Lixin Dai
Associate Professor
University of Hong Kong
Website
Tidal disruption events (TDEs) are among the most fascinating astronomical phenomena, offering a unique probe into the properties of massive black holes and the nuclear environments of galaxies. In this talk, I will present results from theoretical calculations of the realistic rates of TDEs for both supermassive and intermediate-mass black holes. These results reveal how TDE rates depend on black hole mass, stellar dynamics, and galactic environments. I will also show state-of-the-art simulations of TDE accretion, outflows and emissions, demonstrating how these processes produce the diverse emission features we observe, including Bowen fluorescence lines. Finally, I will discuss the broader implications of TDEs for black hole growth, particularly in the early universe, and their role in shaping galactic evolution. By exploring these results, we can better understand the physics of TDEs and their critical role in the growth of black holes and the evolution of galaxies across cosmic time.
Exploring new frontiers in solar flare research using high cadence IRIS observations
Juraj Lörinčík
Research Scientist
Bay Area Environmental Research Institute
Solar flares are sudden, explosive releases of magnetic energy accumulated in the Sun’s atmosphere. Often accompanied by coronal mass ejections, flares are among a few astrophysical phenomena with a direct and tangible impact on human infrastructure. Studying these complex and dynamic events has for long been hindered by the limited temporal, spatial, and spectral resolution of available instrumentation.
Recent high-cadence observing campaigns of the Interface Region Imaging Spectrograph (IRIS) mission have provided new opportunities to explore physics of solar flares captured at unprecedented sub-second time resolution. This colloquium will provide an overview of key discoveries from these unique datasets and discuss how they challenge the current understanding of solar flares. Notably, high-cadence IRIS imaging observations detected dynamic flare kernel brightenings propagating at speeds of thousands of kilometers per second within solar flare footprints. These motions provide the first direct observational evidence of the ‘slip-running regime’ of magnetic reconnection, a fundamental process first simulated nearly two decades ago. In addition, spectroscopic analysis of the same event revealed intriguing time delays between emissions formed in different atmospheric layers, offering new insights into heat propagation therein. Our latest research is focused on quasi-periodic pulsations of plasma downflow velocities in flare footprints. In two different eruptive flares, these pulsations were found to correlate with hard X-ray signatures of energetic electrons, evidencing that the pulsations are driven by magnetic reconnection.
These outcomes not only provide vital observational support for long-standing numerical predictions but also challenge the current generation of models of solar flares and eruptions. The Daniel K. Inouye Solar Telescope (DKIST) is well suited to build upon these findings and advance the understanding of physical processes driving and/or associated with solar flares.
Understanding how the solar wind gets a magnetic push: A coordinated, multi-mission effort during the last total solar eclipse
Yeimy Rivera
Astrophysicist
Center for Astrophysics | Harvard & Smithsonian
CfA Faculty Page
During total solar eclipses, the Sun’s atmosphere, the corona, can be seen with the naked eye continuously out to 10s of solar radii. In this region, its atmosphere is super-sonically expanding creating a continuous outflow of plasma, the solar wind, that fills and shapes the heliosphere. Depending on where it originates on the Sun, the solar wind can experience different levels of heating as it escapes the corona while being accelerated by varying contributions of its thermal pressure gradient and work done by plasma oscillations. While the heating and acceleration has been studied extensively, observations of the solar wind are largely limited to the corona (remote sensing) or farther out (in situ), with few opportunities where both can be linked contemporaneously.
Last year’s 2024 total solar eclipse over North America offered one of the most detailed views of the Sun and its outflowing solar wind for this purpose. Through a multi-mission coordinated effort, our eclipse team follows a single solar wind stream past the orbit of Venus. Through combined ground (NSF-funded DKIST, Mauna Loa Solar Observatory UCoMP and K-Cor) and space (NASA’s Parker Solar Probe, ESA’s Solar Orbiter, JAXA/NASA’s Hinode/EIS)-based remote and in situ observations, the work examines multi-wavelength observations of a low-latitude coronal hole (dark solar regions as observed in EUV where the fastest solar wind escapes from) to derive detailed plasma conditions and magnetic field properties. We connect these remote properties to heliospheric observations during a fortuitous spacecraft alignment around the solar eclipse. Together, a high speed solar wind stream can be traced from deep in the corona into the heliosphere shedding light on the mass and energy flow in the atmosphere of our star. More generally, this work offers insights into the physics of magnetized stellar winds and their impact on the surrounding planetary environment.
Introduction to the Space Science and Engineering Initiative, and Opportunities and Applications for the Next Generation of X/γ-ray Detector Systems and Technologies
Branden Allen
Engineering Specialist Faculty
-and-
Program Lead, SSEI
University of Hawaiʻi Space Science and Engineering Initiative (SSEI)
The Space Science and Engineering Initiative (SSEI) was created as a joint effort between the UHM College of Engineering (CoE) and the Institute for Astronomy (IfA) for the establishment of an interisland advanced technology research and development center based in Hilo, which aims to significantly expand technical capabilities to support the space sciences, particularly targeting application for the observatories on Maunakea and Haleakalā. Here, I will discuss the current status of the SSEI and give a brief overview of our current portfolio of activities.
Afterward, I will discuss my own research program which focuses primarily on the development of high-energy detectors, associated technologies, telescopes and missions for spaceflight. This will be followed by a discussion of plans and potential for their future deployment for use in astrophysics and planetary science.
Imaging the Cosmic Web
Chris Martin
Edward C. Stone Professor of Physics
Caltech
-and-
Director
Caltech Optical Observatories
Website
Space Astrophysics Laboratory
The intergalactic medium (IGM) represents the dominant reservoir of baryons at high redshift, traces the architecture of the cosmic web dominated by dark matter, and fuels on-going galaxy evolution. The IGM has been studied using Quasi-Stellar Objects (QSO) absorption lines including the Lyman alpha forest (LAF), which are unable to provide the information that emission maps would give. But because of the low surface brightness and extended, diffuse distribution, direct detection of an emission equivalent to the absorption LAF has not been possible with existing instrumentation and observational approaches. Using a purpose-built instrument, with nod-and-shuffle and dual-field subtraction, we have detected, for the first time, an emission Lyman α forest (ELAF). The emission forest is highly extended, shows filamentary morphology with filaments connecting galaxies, exhibits statistics like the absorption Lyman α forest, displays spectra resembling the absorption forest, and is correlated with galaxy-traced overdensities consistent with bias like dark matter. We conclude that the ELAF may provide a new tool for tracing a significant fraction of the cosmic web of baryons and dark matter. Finally, I will present status of the Super-pressure STABLE Cosmic Web Imager (SSCWI) program, a Brinson Exploration Hub balloon experiment, focused on emission from the Circum-QSO, the Circum-Galactic Medium, and the cosmic web. SSCWI offers the opportunity to image the cosmic web in the local universe for the first time, and compare its properties to those at high redshift.
Mirage or Miracle? The Enigma of Remarkably Luminous Galaxies at the Cosmic Frontier
Rohan Naidu
NASA Hubble Fellow
MIT
Website
JWST has revealed a stunning population of bright galaxies at z>10 — surprisingly early epochs where few such sources were expected. In this talk I will present the most distant example of this class yet: a luminous source at zspec=14.44 that expands the observational frontier to a mere 280 million years after the Big Bang. Using this source as an exemplar, I will illustrate the challenges and opportunities posed by this class of objects. The number density of bright zspec~14-15 sources is now *spectroscopically* confirmed to be >100 times larger than pre-JWST consensus models. Intriguingly, the lack of a strong damping wing in this z=14.44 source adds to a growing set of hints for a potentially revised timeline for cosmic reionization. The super-solar Nitrogen enhancement in these sources is remarkably reminiscent of the abundance pattern seen in Milky Way globular clusters and the most ancient stars born within the Milky Way — we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time.
Spectroscopy using a Photonic Lantern at the Subaru Telescope
Sebastien Vievard
Assistant Specialist Faculty
University of Hawaiʻi Space Science and Engineering Initiative (SSEI)
A Photonic Lantern (PL) is a novel device that efficiently converts a multi-mode fiber into several single-mode fibers. When coupled with an extreme adaptive optics (ExAO) system and a spectrograph, PLs enable high throughput spectroscopy at high angular resolution. The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system of the Subaru Telescope recently acquired a PL that feeds a R ~ 4,000 spectrograph optimized for the 600 to 760 nm wavelength range. We present here the integration of the PL on SCExAO, and study the device performance in terms of throughput, field of view, and spectral reconstruction. We also present the first on-sky demonstration of a Visible PL coupled with an ExAO system, showing a significant improvement of x12 in throughput compared to the use of a sole single-mode fiber. We also highlight the faithful reconstruction of spectral features of ʻAua [Betelgeuse] and discuss how this work lays the foundation for future advancements in high-throughput photonic instrumentation for high-resolution imaging.
Chips off the old block: The steady state population of Earth’s minimoons of lunar provenance
Rob Jedicke
Emeritus Faculty
University of Hawaiʻi Institute for Astronomy
Recent spectroscopic observations suggest that some asteroids on Earth-like orbits may have originated from the Moon, despite earlier doubts based on dynamical models and cosmic ray exposure ages of lunar meteorites. Some of these objects become temporarily gravitationally bound to Earth, and a subset — known as ‘minimoons’ — briefly orbit our planet.
In this study, we use numerical simulations to calculate the steady-state size-frequency distribution of the bound population, incorporating current models of lunar impact rates, impact energy, crater-scaling laws, and the relationship between ejecta mass and velocity. Our results show that lunar ejecta could plausibly explain the observed population of bound objects, although uncertainties in crater formation and ejecta properties lead to a wide range of possible outcomes. If these objects can be spectrally distinguished as lunar or asteroidal in origin, it may offer new constraints on both cratering processes and the transport of small bodies from the main asteroid belt into near-Earth space.
TBA
Edward C. Moran
Professor of Astronomy
Wesleyan University
Coming soon.