Colloquia

Constraining dust optical properties is essential for interpreting remote sensing observations of planetary atmospheres and surfaces, as well as for understanding the radiative impact of aerosols in climate and circulation models. In this talk, I will present recent advances in the retrieval and experimental characterization of dust optical properties across the ultraviolet, visible, and near-infrared wavelengths. Our approach combines laboratory measurements with advanced light-scattering modeling to determine wavelength dependent complex refractive indices and other key parameters such as single-scattering albedos, cross sections, and efficiencies. Three Martian dust analogues were analyzed, each prepared with narrow particle size distributions representative of airborne dust in the Martian atmosphere. Particular attention was given to the effects of particle shape, composition, and size on the derived optical properties. The resulting validated optical property database covers wavelengths from 200 to 2000 nm and provides a physically consistent foundation for radiative transfer modeling. These results offer improved constraints for interpreting spacecraft and ground based observations of planetary materials and contribute to the broader understanding of dust scattering behavior in planetary environments.

The search for supermassive black hole binaries (SMBHBs) seemingly saw the dawn of exploration over the past twenty years with several hundred sub-pc candidates claimed from photometric and spectroscopic surveys monitoring active galactic nuclei (AGNs). While the existence of SMBH pairs have been detected at kpc separation, the observational evidence for sub-pc SMBHBs is however still inconclusive. Finding and
expanding the arsenal of SMBHB candidates is not only vital for understanding the co-evolution with their galactic hosts, but is complementary to pulsar timing arrays searching for low-frequency gravitational waves. With the advancements of upcoming high-precision, wide-field optical photometric surveys, like Vera Rubin’s LSST, robust electromagnetic detections may therefore happen in the near future.
Following the pursuit of confirming SMBHBs in the optical, we explore the possibility of using the ESA Plato space mission to detect the photometric signature of Doppler boosting and gravitational self-lensing events linked to their binarity. Although not designed for it, in this seminar we will discuss how Plato may play an essential role in future searches of SMBHBs and for AGN variability research in general. With a minimum 2-yr baseline per pointing field, our simulation study also serves as a benchmark for the upcoming Plato Guest Observer (GO) call in April 2026 designed for complementary sciences alike

HAYDN is one of the ten mission concepts proposed to ESA’s M-class call (M8) after its Step-1 selection. It is designed to revolutionise our understanding of stellar structure and evolution through high-precision, space-based asteroseismology in dense stellar fields, including clusters. By performing continuous photometric monitoring of stars in these dense stellar fields, HAYDN aims to map stellar interiors across a wide range of ages, masses, and chemical environments—providing unprecedented constraints on stellar physics, Galactic evolution, exoplanet’s formation, and the formation history of the Milky Way, for naming some of the HAYDN’s science cases.

Our work focuses on high-accuracy spectral modeling in NLTE, and the determination of chemical abundances for the oldest known stars, providing crucial insights into the early universe and nucleosynthesis processes. Utilizing state-of-the-art spectroscopic techniques, we have analyzed high-resolution observations of the hyper metal-poor star J0815+4729 to derive its precise elemental abundances, including the elements carbon and oxygen. We discuss the implications of our findings on our understanding of the formation and evolution of the oldest stars. In addition, we are constructing a comprehensive NLTE synthetic spectral library that spans from 0.2 to 3 μm in wavelength, which will be made accessible to the public. This spectral library will make a significant impact to large spectroscopy surveys such as APOGEE, DESI, LAMOST, 4MOST, and others.

The rapid progress of quantum technologies—highlighted by recent Nobel Prizes recognizing advances in controlling quantum matter—is reshaping how we investigate the fundamental laws of nature. In this colloquium, I will introduce the concept of quantum machines: platforms such as quantum computers, analog simulators, and engineered networks of photons or ultracold atoms that process information according to the principles of quantum mechanics. These systems are emerging as powerful tools to emulate physical phenomena that were previously inaccessible to theory or experiment. By bridging quantum information science, tensor network methods, and high-energy physics, this work exemplifies how quantum machines are becoming laboratories for exploring exotic phases of matter, the structure of gauge fields, and the processes that shaped the early cosmos. Together, these advances mark the beginning of a new era in which we can engineer, manipulate, and ultimately understand some aspects of the quantum fabric of the universe.

In the past decades, studies of the Milky Way have entered a golden era of large-scale surveys. The Gaia satellite provides precise positions, proper motions, and parallaxes for billions of stars, while ground-based spectroscopic surveys, such as LAMOST, deliver radial velocities and metallicities for nearly ten million stars. In addition, medium- and narrow-band photometric surveys, as well as Gaia’s slitless spectroscopic surveys, provide atmospheric parameters for hundreds of millions of stars. This talk will first summarize our efforts in measuring stellar parameters from these surveys, and then present our work on understanding the assembly history of the Milky Way—particularly its early phase, when the proto-Galaxy formed—and its dark matter distribution, based on the measured parameters of a very large number of stars.

Massive stars play a vital role in shaping the cosmic matter cycle and driving galaxy evolution, chemically enriching their host galaxy through their powerful stellar winds. Understanding the physical processes behind these mass-loss events is key to producing accurate model predictions. Despite its importance, stellar atmosphere modelling poses several challenges. In this talk, we will explore these challenges accross a range of massive stellar types, from OB main-sequence stars to evolved red supergiants and Wolf-Rayets. With these insights, I will further discuss the consequences of mass outflows on stellar evolution and the surrounding environment.

The remarkable success of recent cosmology in pinpointing a consistent concordance model relies on several foundational assumptions, including homogeneity, isotropy of the universe, and scale invariance, among others.  Increasingly precise cosmological observations, such as the exquisite measurements of the CMB sky from the ESA Planck space mission, have opened up the possibility of robust, independent tests of these assumptions. I will present key results from my research programs on this theme and review the current status of the research.

During the last few decades, we've begun to glimpse the universe not just with photons, but also with other messengers like cosmic rays, neutrinos, and even gravitational waves. I will show why photons, cosmic rays, and neutrinos are fundamentally interconnected—as dark matter may also be—and why very-high-energy gamma rays are a key domain in multi-messenger astronomy. I'll emphasize the role of a few key experiments in the Canary Islands in this field, and discuss some of the latest results that are opening new scientific prospects for the upcoming generation of detectors.