Stellar Chemistry and Planetary Connections: Insights from Lithium and High-Precision Abundance Studies

Qinghui Sun

Associate Scientist

Tsung-Dao Lee Institute, Shanghai Jiao Tong University

SJTU faculty webpage

Understanding the connection between stars and their planets is essential for revealing the processes that govern stellar interiors and shape planetary systems. High-resolution stellar spectroscopy enables precise measurements of the chemical compositions of planet-hosting stars, offering insights into stellar evolution, planet formation, and conditions for habitability. This talk will present results from large ground-based telescopes and dedicated programs, including abundance studies of solar twins, solar-type stars, binaries, and clusters, along with their planetary systems. These abundances trace stellar internal processes, reveal abundance patterns linked to planet formation, and provide a consistent framework for comparing stellar and planetary compositions. Advances in observational facilities and statistical methods are driving a more integrated view of star–planet chemical connections, highlighting current challenges and pointing to future opportunities.

The Space-Based Time-Domain Revolution in Astrophysics

Dan Huber

Associate Astronomer

University of Hawaiʻi Institute for Astronomy

Website

Review articles are a cornerstone of the astronomical literature. They introduce students and newcomers to a field, and provide seasoned researchers with a convenient citation for the introduction of their next paper. Writing a review, however, is rarely convenient. It is typically a long, occasionally painful, exercise. This talk will tell the story of an Annual Reviews of Astronomy & Astrophysics article more than three years in the making that has (at long last) reached publication. The review describes the transformation of astrophysics by space-based time-domain telescopes such as CoRoT, Kepler/K2, and TESS. By delivering continuous, high-cadence, high-precision light curves for millions of sources in our Galaxy and beyond, these missions have reshaped astrophysics over the past two decades, enabling breakthroughs ranging from the solar system and stellar interiors to transients and active galactic nuclei.

Bridging black hole accretion physics across the mass spectrum with tidal disruption events

Vera Berger

NSF Graduate Research Fellow

Massachusetts Institute of Technology

Website

Tidal disruption events (TDEs) offer rare real-time views of the formation and evolution of accretion disks around massive black holes. Their spectral and timing properties provide independent constraints on the black hole mass, making TDEs valuable probes of accretion physics across the mass spectrum. I will present a five-year spectral and timing study of the TDE AT2019teq, which exhibits extreme variability, including order-of-magnitude changes in flux on minute-to-day timescales, and a rare late-time emergence of hard X-ray emission, leading to the longest-lived corona observed in a TDE. AT2019teq’s evolution shows unique similarities to X-ray binary state transitions, albeit at higher luminosity and on much faster timescales. Using the presence of both a disk-dominated and a corona-dominated state, I apply multiple spectral and variability-based estimators of the black hole mass. I will discuss how TDEs with state transitions can probe the mass scaling of black hole accretion physics.

A Path to an All-Sky Survey with Roman

Jesse Han

Stanford Science Fellow

Stanford

Website

A deep, space-based, all-sky near-infrared survey carried out with the Nancy Grace Roman Space Telescope would constitute a foundational astronomical infrastructure for decades to come. In this white paper, we present a concrete and feasible path to imaging the entire sky at ∼0.1′′ resolution, beginning with high-impact fields in Cycle 1 and scaling to ultra-wide coverage within the nominal mission. This first-epoch survey will reach H∼25.5 AB mag (5 σ ) and maximize synergies with contemporaneous observatories, while preserving substantial time for other ambitious Roman programs. We outline representative scheduling scenarios and an example Cycle 1 program that triples early Roman-LSST overlap and delivers high-value community data products such as LSST forced photometry, joint Gaia-Roman astrometry, and catalogs of Galactic substructure, strong lenses, and other rare systems. The Cycle 1 program will lay the foundation for an eventual all-sky survey, while also delivering high-impact early science. We invite broad community participation in shaping and carrying out both the initial program and the long-term vision of an all-sky Roman survey.

Size distributions of small bodies in the solar system

Andrew Hoffman

PhD Candidate

University of Hawaiʻi Institute for Astronomy

IfA student webpage

The sizes of small bodies (asteroids, comets, etc) in the solar system are a result of both their formation processes and subsequent evolution. Therefore, characterizing the sizes of these objects can tell us about their history. I will give a quick run-through of the importance of investigating the sizes of small solar system bodies. I will go over the current understanding of the various populations, the relevance of 3I in this context, and a brief summary of some of my recent work with the sizes of long period comets.

What Lava World 55 Cancri e Reveals About the Cosmic Shoreline for Rocky Planets

Barron Nguyen

Undergraduate Student

Stanford University

Personal webpage

Super-Earth 55 Cancri e is a mature 8 Gyr lava world orbiting a K-type star, with JWST observations suggesting a carbon-dominated atmosphere (CO2/CO) over a global magma ocean. This challenges the “cosmic shoreline” view that secondary atmospheres cannot survive on close-in planets. We suggest this atmosphere arises from outgassing of its initial volatile reservoir. As solidification drives the magma ocean away from solution-equilibrium, tidal and greenhouse heating prolong outgassing. Our model shows tidal heating maintains high surface temperatures (~3200 K at e=0.005) to the present day, though with a tradeoff between prolonging tenuous outgassing and enlarging the atmosphere. Tidal heating dominates early before shifting toward volatile inventory dependence at mature ages. This feedback gives rise to a “cosmic sandbar,” set by outgassing-escape balance rather than the predominantly escape-regulated shoreline. Using the previously-thought outlier 55 Cancri e as a case study, we present a framework linking tidal heating, volatile budgets, stellar type, and age to secondary atmosphere formation on close-in rocky planets, predicting an outgassing-regulated sandbar and escape-regulated shoreline bounding an airless valley, with generalized implications for systems like TRAPPIST-1 and the JWST DDT survey.

Probing Limb Darkening and Stellar Interiors Using Interferometry and Asteroseismology

Arnab Chowhan

PhD Candidate

University of Sydney

Limb darkening, the dimming of light across the stellar disk, strongly affects how we measure the sizes and temperatures of stars. Using the PAVO beam combiner at the CHARA Array, we can spatially resolve the surfaces of red giant stars and precisely map their center-to-limb intensity profiles, yielding angular diameters that, combined with Gaia parallaxes and spectral energy distributions, provide model-independent stellar radii and temperatures. Some stars also produce oscillations that travel through their interiors, which we can study using asteroseismology with the TESS Mission. In this talk, I will present results from a survey of 15 giant stars observed with PAVO, demonstrating that state-of-the-art 3D STAGGER atmosphere models systematically overpredict limb darkening coefficients, leading to angular diameter overestimates of around 2%. I will further present the first combined interferometric and asteroseismic analysis of a core-Helium burning red giant, showing how the two techniques together break degeneracies in stellar evolutionary models and place stringent tests on our understanding of these models.

The IfA REU Program: A summer full of students

Roy Gal

Astronomer

IfA

The IfA has had an NSF-funded Research Experiences for Undergraduates (REU) program almost continuously for two decades. The program was just renewed for two more years, and, together with PI-funded positions, we will be welcoming 15 students this summer (and 6 more with CHAMP+AHA). I’ll talk about what’s new with the program, what current and prospective mentors can expect, and take suggestions for future iterations of the program.

A Critical Examination of the PAH Hypothesis 

Alan Tokunaga

Astronomer Emeritus

University of Hawaiʻi Institute for Astronomy

IfA webpage

The polycyclic aromatic hydrocarbon (PAH) hypothesis proposes that the aromatic infrared bands (AIBs) observed at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μm originate from gas-phase PAH molecules. These bands exhibit consistent peak wavelengths and profiles in many diverse sources. Significantly, the Infrared Space Observatory and JWST spectra show nearly identical red wings of the 3.3 μm AIB and blue wings of the 11.2 μm AIB. This spectral uniformity suggests that the AIBs arise from a small number of gas-phase PAH species, regardless of the excitation conditions or the nature of the source (i.e. HII regions, reflection nebulae, planetary nebulae, young stellar objects, the diffuse interstellar medium). However, a small number of gas-phase PAH species is inconsistent with current modeling of the AIBs, which requires a wide range of gas-phase PAH molecules. It is also inconsistent with the lack of observed ultraviolet and optical absorption bands from gas-phase PAH molecules. These issues require quantitative investigation to definitively establish gas-phase PAH molecules as the carrier of the AIBs. A paper with the details of this talk can be found at: this link.

Lessons learned from way too many missions to Mars

James Wray

Professor

Georgia Institute of Technology

Website

After completing a lovely summer research project with Mike Liu here at the IfA, I was tricked into studying Mars rocks for the next 20 years by Mike’s undergraduate advisor, who told me that geology was just astronomy with the telescope moved closer to its target. There are other differences too, as it turns out. This talk will cover personal highs and lows from working on a range of Mars missions, describing how I joined their science teams and failed to join some others. Team dynamics play a big role in both scientific and career enjoyment outcomes for these missions, so the talk will describe approaches that have seemed beneficial in this regard.

A Stellar Obliquity Measurement for the Disintegrating Planet BD+05 4868 Ab

Steven Giacalone

NSF Astronomy & Astrophysics Postdoctoral Fellow

Caltech

Website

Stellar obliquity, defined as the angle between the stellar spin vector and the planetary orbital angular momentum vector, is a unique tracer of orbital evolution. Over the last decade, obliquity measurements of stars with transiting hot Jupiters have revealed a wide variety of orbital orientations, including polar and retrograde orbits that challenge the conventional picture of quiescent migration through a protoplanetary disk. Thanks to discoveries from the NASA TESS mission and new high-precision radial velocity instruments, our understanding of the stellar obliquity distribution has extended to systems with Neptune-mass planets in recent years. However, these measurements are still largely out of reach for rocky planets, which induce signals too small for even the most state-of-the-art EPRV spectrographs due to their shallow transits. Disintegrating planets provide the rare opportunity to study the dynamical histories of rocky planets in detail. These worlds, which are believed to be less massive than Mars, orbit so close to their stars that they shed mass catastrophically, leaving large comet-like tails of dust in their wakes. These tails sometimes occult more than 1% of the stellar surface, inducing deep transits that can be used to measure the obliquities of their host stars. As of today, only four disintegrating planets have been detected, and only one — BD+05 4868 Ab — orbits a star bright enough for EPRV follow-up observations. Using concurrent observations with Keck/KPF and the ESA CHEOPS space telescope, we precisely constrain the stellar obliquity of the BD+05 4868 A system, finding that the orbit of the disintegrating planet is significantly misaligned with the spin axis of the host star. We discuss the implications of our measurement for the dynamical evolutions of rocky planets and forecast the prospects of discovering and characterizing similar systems in the future.

Trials and trepidations of the 2024 total solar eclipse expedition

Shadia Habbal and Zac Bailey

Faculty and Grad Student

IfA

The latest Solar Wind Sherpas total solar eclipse expedition was in April 2024. To maximize the group’s chances of data acquisition during totality they secured three observing sites on the ground across the path of totality: Torreon, Mexico; Kerrville, Texas; and Sims, Arkansas. The Sims group was accompanied by 2 cinematographers/photographers who produced a 17 minute documentary that was entered in several film festivals in Europe and in the US and received very favorable reviews. It has not been publicly released yet. However, we were granted permission to show it for the first time at the IfA during the Open House. This is its second showing at the IfA.

Community Building Activities

IfA Community

Graduate Students and Postdocs

IfA

IfA Website

Come hang out and build community!