Colloquia

MHD waves – slow, Alfvén and fast – lose their distinctiveness in certain regions of a stratified plasma, such as solar or stellar atmospheres. We discuss all three mode conversion processes, fast/slow, fast/Alfvén and slow/Alfvén and how they are affected by atmospheric structure, magnetic field orientation, and partial ionization. We also present some simulations of fast/slow coupling in shock waves.

Stellar models are a crucial ingredients for a pletora of fundamental research fields in Astrophysics: from the planet-host stars to Galactic Archaeology, from fundamental Physics to the study/understanding of far-away unresolved galaxies, from helio/astero-seismology to exotic stellar objects such as Blue Stragglers, Blue Hook stars, millisecond pulsars, supernova progenitors, etc. There are various stellar model libraries available in the literature, each one with its own pro and cons; some of them being more suitable for specific research topics. In any case, the use of any stellar model library should not ignore the knowledge of the limitations affecting each library. In this talk, we present the BaSTI_IAC stellar model library that has been developed in the context of a strong collaboration with staff members of the IAC; we discuss the main characteristics of this library, and make a comparison with some of the most commonly used model libraries available in literature. We present also some important recent applications of the BaSTI_IAC library to various scientific problems. At the end we discuss the ongoing effort to improve/extend the library as well as our wish to include additional stellar and sub-stellar mass ranges, with hope to foster new collaborations/synergies with colleagues@IAC.

The elusiveness of neutrinos is most renowned for their ability to penetrate and traverse vast amounts of matter without disturbance. While this very same property makes neutrino detection one of humanity’s most remarkable achievements, recent and forthcoming advancements in instrumentation continue to enhance our ability to harness neutrino-based information as a fundamental tool. This, in turn, provides unique insights into some of the most essential mysteries of the Universe. For instance, shortly after their discovery in the 1950s, neutrinos offered direct confirmation and deeper understanding of the fundamental fusion processes powering the Sun. Today, they are indispensable to our quest for a comprehensive understanding of Earth’s interior, the depths of the Sun, supernovae, high-energy cosmic ray emissions, and the early Universe’s structure following the Big Bang. Furthermore, neutrinos may play a crucial role in our pursuit of the origins of matter and the search for new physics beyond the Standard Model.
In this colloquium, I will highlight some of the most remarkable achievements in neutrino science to date, as well as emerging advancements that have the potential to complement all other cosmic probes — most notably, those within the IAC’s leadership in this field.

Stars and planets formed within the same molecular cloud are inextricably linked in their composition. Alpha-process elements shape planetary cores and atmospheres, with studies showing that key elemental ratios (e.g. Fe/Si, Mg/Si) in planets reflect those of their host stars. While correlations between stellar chemical abundances, planet occurrence, mass and orbital properties have been suggested, definitive confirmation remains difficult due to the subtlety of these trends. Large, homogeneous, high-precision spectral datasets are essential to uncover these relationships. Bright stars (V < 11 mag), such as PLATO's priority-one targets, provide an ideal sample for high-quality stellar and chemical abundance measurements and are expected to yield thousands of new planetary discoveries in the coming years. However, modern multi-object spectroscopic (MOS) surveys often exclude these stars due to their low on-sky density, leading to inefficiencies in conventional observing strategies. The WEAVE-TwiLight Survey (WTLS) solves this problem by introducing a groundbreaking observing mode that optimises efficiency by combining multiple fields into a single fibre configuration. It is expected to produce a homogeneous spectral dataset of ~6,000 bright stars, tailored to probe the chemical relationships between host stars and their planets. In this talk, I will give a general overview of host-star planet relations and discuss the status of the upcoming WEAVE-TwiLight Survey.

On December 25, 2021, the James Webb Space Telescope was launched from Earth towards its ultimate destination at the L2 Lagrange Point, 1.5 million kilometers away from Earth. The culmination of decades of planning, construction, execution, and transport all came down to a critical few minutes, which led to our newest flagship observatory in space. Science operations began in July of 2022, with the past 2+ years bringing about a number of scientific revolutions: both expected, such as the discovery of a number of record-breaking galaxies and other cosmic objects, and unexpected, such as new features in star and planet-formation, and big surprises about the earliest supermassive black holes in our Universe. Come learn what we've discovered and how it's altered our cosmic perspective, and explore how the unheralded concept of "discovery potential" is essential for driving unexpected discoveries at the frontiers of science.

One of the most fundamental questions in astronomy is how stars, the building blocks of the Universe, form. We generally understand that stars emerge from dense regions within molecular clouds, called prestellar cores, which collapse under gravity to form protostars, but many details of this process remain elusive. Despite significant advances in instrumentation and modelling, we still lack a complete understanding of how stars and planetary systems develop. A crucial piece of this puzzle lies in the protostellar phase, particularly the accretion process responsible for stellar mass growth at the early and more embedded stages of star formation. In this talk, I will review the current state of knowledge on accretion, presenting my work on last observational results of the early stages of star formation and discussing their implications for the broader star and planet formation scenario. 

Relativistic jets are amongst the most important and powerful phenomena in astrophysics, and yet also amongst the least understood. Most well known in the context of supermassive black holes in active galactic nuclei (AGN), relativistic jets are also the underlying mechanism behind gamma-ray bursts (GRBs) and LIGO neutron star merger afterglows, and a fundamental component of Tidal Disruption Events. Stellar mass (<20 solar masses) black holes and neutron stars in binary systems, known as 'X-ray binaries' (XRBs), are the local, lower-mass, and hence faster-evolving analogues to AGN, as well as being the direct descendants of GRBs and on the same mass scale as the LIGO merging BH. The near scale-independence of accretion and jet formation with BH mass, theoretically expected and observationally established, demonstrates that what we learn from XRBs can be applied to more massive systems such as AGN. In the past 6 years observations with the MeerKAT telescope have revolutionised our understanding of these jets, allowing unprecedented investigations into the power of black hole jets, measured as we track them decelerating and transferring their launch kinetic energy to the ambient ISM. These observations have also increased our sample size sufficiently that we can now make definitive statements about the relation between jet speed, jet precession, the nature of the compact object, and the connection to black hole spin.

Mathematics of atmospheric fronts: S.Q.G.(Surface Quasigeostrophic Equation) is a relevant model to understand the evolution of atmospheric fronts. It represents also a mathematical challenge, because of its non-linear and non-local character, which illustrates the rôle of mathematics in the development of science.

This colloquium will be held in person in the Aula

In the local universe most of the stellar mass is in passive galaxies, where star formation is
absent or at very low levels. Understanding what are the mechanisms that have been
responsible for quenching star formation in galaxies, and transforming them into passive,
quiescent systems, is one of the main observational and theoretical challenges of extragalactic
astrophysics. I will give a brief overview of the several possible quenching causes and physical
processes that have been proposed so far, ranging from feedback from black hole accretion and
starburst activity, to effects associated with the large scale environment in which galaxies live.
Although most of these mechanisms and causes play a role in different classes of galaxies and
at different epochs, multi-band observations are providing growing evidences that just a few of
them play the key, dominant role.
I will conclude by providing prospects for further investigating these aspects and tackling open
questions with the next generation of observing facilities.