Astrophysics · Pontificia Universidad Católica de Chile
I’m currently pursuing a Master’s degree in Astrophysics at Pontificia Universidad Católica de Chile. My research focuses on resolved and unresolved stellar populations, with a particular emphasis on the Surface Brightness Fluctuation (SBF) technique. Recently, I’ve begun studying comets, motivated by the arrival of the interstellar object 3I/ATLAS. Beyond that, my interests include extragalactic astrophysics and cosmology.
What I work on, the papers I’ve contributed to, a bit about me, a handy CSV Spectra Viewer for quick, in-browser plots of large spectra. And finally a public Python package for fluorescence modeling of comet spectra called CometSpec.
Under the guidance of Dr. Christopher Russell and Prof. Jorge Cuadra, I helped develop a public virtual-reality app that lets users explore and “fly through” the Milky Way’s Galactic Center. Built with Unity and C#, the experience combines supercomputer simulations with Chandra X-ray observations. My contributions focused on user-facing utilities, parameter controls, and in-app menus, to make the app intuitive and accessible.
Since 2021 I’ve been part of Prof. Thomas Puzia’s group, working with the Surface Brightness Fluctuations method. Rather than treating SBF solely as a distance indicator, my work explores its value for the study of stellar populations.
I began by quantifying how SBF absolute magnitudes vary with age and metallicity across multiple HST filters using Milky Way globular clusters. This became my bachelor’s thesis; I’m currently preparing the manuscript for submission.
For my master’s thesis I model SBF magnitudes and colors using synthetic stellar populations, from simple to composite populations, expanding the filter set. The goal is to link population parameters to SBF observables and map key degeneracies.
Since July 2025 our group has been studying the interstellar object 3I/ATLAS, the third known interstellar visitor to pass through the Solar System. We have collected observations from multiple facilities, including SOAR and the VLT.
I have analyzed high-resolution spectroscopy to investigate its composition and temporal evolution (e.g., CN, [O I], CO2, H2O, and dust behavior).
We have developed a Python package called CometSpec for this purpose. The package allows fluorescence modeling and fitting via Markov-chain Monte Carlo (MCMC). Isotopes can be included and you can provide your own line lists to expand to more molecules. Check the Publication section for the paper reference.
Context. 3I/ATLAS is only the third known interstellar object to traverse the Solar System, and the first object for which both branches of the perihelion passage can be monitored at high spectral resolution. Aims. We characterize in 3I/ATLAS the heliocentric evolution of the CN production rate and the forbidden [O I] emission, describe the broader emission line inventory, and release the analysis tools and reduced data products to the community. Methods. We obtained high-resolution (R ≃ 140 000) spectroscopy of 3I/ATLAS on 23 nights with VLT/ESPRESSO (rh = 1.67–2.45 au). The CN production rates were derived by fitting the B2Σ+−X2Σ+ band using CometSpec, a publicly released Python package for flexible fluorescence modeling. The three forbidden [O I] lines were modeled to derive the green-to-red (G/R) flux ratio and a CO2/H2O proxy. The two quantities were fitted with symmetric and piecewise-asymmetric power laws. Results. We detected CN in 18 of 22 useful nights. We fit QCN = a(rh/1au)b to the production rate versus heliocentric distance relation. The pre-perihelion CN power-law index is bpre = −4.62+1.25−1.22, which is within the range observed for Solar System comets. The CN residuals about the smooth model show substantial scatter that we attribute to a combination of systematics and possible physical drivers that the current cadence cannot disentangle. The G/R ratio decreases from ∼0.42 ± 0.14 at rh ≃ 2.4 au to ∼0.114 ± 0.004 near perihelion. The asymmetric piecewise oxygen fit is strongly preferred over the symmetric fit, consistent with thermal inertia models, although a denser post-perihelion sampling is needed to confirm this. The CO2/H2O proxy spans ∼0.06–1.06 and is comparable to the values reported by Subaru/HDS and SPHEREx and to those measured for 2I/Borisov. We additionally identify Ni I and Fe I and report post-perihelion production rates for C2 and CH. Conclusions. Our high-resolution monitoring of 3I/ATLAS reveals a CO2-rich coma that becomes progressively H2O-dominated near perihelion, with a G/R asymmetry consistent with delayed H2O sublimation predicted by thermal inertia models. Together with the public release of CometSpec and the reduced data, these results provide an empirical reference and a methodological framework for the next generation of interstellar object monitoring campaigns.
We report Very Large Telescope spectroscopy of the interstellar comet 3I/ATLAS (C/2025 N1), from rh ≃ 4.4 to 2.85 au, using X-Shooter (300–550 nm, R ≃ 3000) and UVES (optical, R ≃ 35–80 k). The coma is dust-dominated, with a fairly constant red optical continuum slope (∼21%–22%/1000 Å). We report the detection of CN emission and also detect numerous Ni I lines, while Fe I remains undetected, potentially implying efficiently released gas-phase Ni. At rh ≃ 3.14 au, we derive 3σ limits of Q(OH) < 1.48 × 1026 s−1 but find no indications for [O I], C2, C3, or NH2. From our latest X-Shooter measurements, conducted on 2025 August 21 (rh = 2.85 au), we measure production rates of log Q(CN) = 24.81 ± 0.01 molecules s−1 and log Q(Ni) = 23.30 ± 0.07 atoms s−1 and characterize their evolution as the comet approaches perihelion. We observe a steep heliocentric distance scaling for the production rates Q(Ni) ∝ rh−7.7±1.0 and Q(CN) ∝ rh−6.7±0.2, and we predict an Ni–CO2 correlation if the Ni I emission is driven by the carbonyl formation channel. Energetic considerations of activation barriers show that this behavior is inconsistent with the direct sublimation of canonical metal/sulfide phases and instead favors low-activation-energy release from dust—e.g., photon-stimulated desorption or mild thermolysis of metalated organics or Ni-rich nanophases, possibly including Ni–carbonyl-like complexes. These hypotheses will be testable with future coordinated ground-based and space-based monitoring, as 3I becomes more active during its continued passage through the solar system.
Interstellar objects (ISOs) provide unique insights into the building blocks and conditions of extrasolar planetary systems. The newly discovered object, 3I/ATLAS (C/2025 N1), represents the third known ISO after 1I/'Oumuamua and 2I/Borisov. We present initial spectroscopic characterizations of 3I using observations from the Goodman High Throughput Spectrograph on the 4.1 m SOAR Telescope in Chile during the night of July 3. The reflectance spectrum of 3I, covering 3700–7000 Å, reveals a red continuum, comparable to extreme trans-Neptunian objects, with a weak UV-optical turnover indicative of complex carbonaceous and irradiated organics. At the time of observation, when 3I was at a heliocentric distance of 4.4 au, we detected no discernible gas emission from canonical cometary species (CN, C3, C2, CO+, and [O I]). This is in agreement with expectations from our thermal evolution model, which indicates sublimation-driven activity should commence once 3I/ATLAS approaches smaller heliocentric distances. Nonetheless, the paradoxical situation of early onset coma without evidence of sublimation tracers calls for other dust-liberating mechanisms that ancient ISOs may be subjected to at large heliocentric distances.
Hello! I am Jose Baltasar Luco Korn, though I prefer to go by Baltasar. I am a Chilean astronomy graduate student with a deep passion for understanding the universe through stellar populations and its chemical evolution.
I hold two bachelor's degrees one in Astrophysics and another in Mathematics from Pontificia Universidad Católica de Chile, where I developed a strong foundation in both theoretical and observational astronomy. Since 2025, I have been pursuing my Master's degree in Astrophysics at the same institution, deepening my expertise in stellar population synthesis and extragalactic research.
My fascination with astronomy began in childhood. Over the years, this curiosity has evolved into a focused research interest in stellar populations, understanding how the collective properties of stars reveal the formation histories of galaxies. I am particularly drawn to using techniques like Surface Brightness Fluctuations (SBF) to probe stellar ages, metallicities, and distances across cosmic time, from resolved to unresolved stellar populations, in simple and composite populations.
Beyond stellar populations, I maintain broad interests across astrophysics, including cosmology, extragalactic astronomy, and the study of interstellar objects. I've had the privilege of contributing to groundbreaking observations of 3I/ATLAS, the third known interstellar visitor to our Solar System, combining spectroscopy with theoretical modeling to understand its composition and origin.
When I'm not working with data, I enjoy exploring new technologies for data visualization, building tools for the astronomy community, and staying curious about the intersection of mathematics, physics, and computation in modern astrophysics.
Besides astronomy research, I have gained diverse experience in science communication, teaching, and even international work. I am passionate about sharing knowledge and connecting with communities through education and outreach.
Pontificia Universidad Católica de Chile
Astrophysics Institute, Pontificia Universidad Católica de Chile
Refined skills in science communication through multimedia editing, social media management, and live streaming. Served as Monitor Coordinator for the public opening of the historic Manuel Foster Observatory (a National Monument), promoting astronomy education and preserving astronomical heritage.
Center of Excellence in Astrophysics and Related Technologies (CATA)
Engaged in science communication initiatives, multimedia editing, and social media management. Coordinated and executed diverse educational outreach activities across various schools and provinces within Santiago, promoting scientific literacy and community engagement with astrophysics.
Beyond my formal roles, I am still participating in various outreach activities in my free time. The outreach activities I have been involved so far include:
Vail Resorts · Breckenridge, CO, USA
Worked as a ski instructor under the J1 Visa program, specializing in teaching children aged 3 to 6 years old. Enhanced teamwork skills, fostered social relationships, gained experience working with children, and embodied a strong sense of responsibility in an international setting.
Outside of astronomy:
Photography allows me to capture fleeting moments and see the world through a different lens—both literally and figuratively. I enjoy working with both digital and analog (film) photography, appreciating the immediacy and flexibility of digital alongside the deliberate, tactile process of shooting film.
I take photos of the night sky, everyday life, and landscapes. I enjoy the entire process, from getting the frame shot to editing, finding satisfaction in capturing moments and bringing out their essence through post-processing.
I enjoy making beer from scratch, preparing the ingredients, brewing, bottling, and finally trying the results. I like to test different types of recipes and put my own touch on them, while keeping detailed records to make my brews reproducible.
From all the different beer styles, I'll highlight APA (American Pale Ale) as my favorite. Here I attach the recipe for one of my best brews, the Patagonia Best Bitter.
A selection of moments captured through my lens: landscapes, travels, and everyday beauty. Click on any image to view it in full size.
