Measuring the Hubble constant is difficult. In the local universe, the H0 determination is hampered by two impediments: the local disturbance of the expansion field and the rarity of luminous distance indicators with a reliable calibration. This led to the principle of the distance ladder, where distance indicators are calibrated at lower distances and then applied as calibrators of another distance indicator at larger distances. Several methods have been used in the past years to measure the local expansion rate, but they have not converged. In addition, some of the local H0 determinations disagree with the derived expansion rate from the Lambda CDM model as calibrated by the cosmic microwave background resulting in the ‘Hubble tension’. Recently, a Garching team has improved the Expanding Photosphere Method (EPM) for type II supernovae to derive H0 bypassing the distance ladder. This promises to become an independent and unique probe of the cosmic expansion rate. 

The first generation of stars, often called Population III (or Pop III), form from metal-free primordial gas at

redshifts z ~ 30 and below. They dominate the cosmic star formation history until z ~ 20-15, at which point

the formation of metal-enriched Pop II stars takes over. I review current theoretical models for the formation,

properties and impact of Pop III stars, and discuss observational constraints. I argue that primordial gas is highly

susceptible to fragmentation and Pop III stars form as members of small clusters with a logarithmically flat mass

function. Feedback from massive Pop III stars plays a central role in regulating subsequent star formation, but major

uncertainties remain regarding its immediate impact. Direct observations of Pop III stars in the early Universe remain

extremely challenging, whereas stellar archeological surveys allow us to constrain both the low-mass and the high-mass

ends of the Pop III mass distribution. Observations suggest that most massive Pop III stars end their lives as core-collapse

supernovae rather than as pair-instability supernovae.  I also speculate about the formation of supermassive stars, which

under very specific circumstances can get as massive as several 100.000 solar masses and can become the seeds of the

supermassive black holes observed in the high-redshift universe.

Variations in the abundance of interstellar dust have important implications for our ability to trace the chemical enrichment of the universe, stellar mass assembly, and profoundly affect galaxy evolution. I will present results from three observational efforts to characterize the variations of the dust content and properties within and between galaxies, in particular as a function of metallicity and gas density. The dust and gas contents of nearby galaxies were measured using far-infrared, HI 21 cm, and CO emission on the one hand, and UV absorption spectroscopy with Hubble on the other hand. Both approaches demonstrate a significant increase of the dust abundance with gas density, even in very low metallicity systems such as Sextans A (7% solar metallicity). Furthermore, the fraction of metals locked in dust decreases with decreasing metallicity, by a factor of 2 from the Milky Way to the SMC, and a factor 4 from the Milky Way to Sextans A.  This results in the dust-to-gas ratio (D/G) decreasing faster than metallicity, consistent with chemical evolution models and with measurements in Damped Lyman-alpha systems at redshift <4. However, this decrease in D/G is not as dramatic as suggested from previous FIR measurements in nearby galaxies. Furthermore, ongoing efforts to measure the properties and abundance of the smallest dust grains, polycyclic aromatic hydrocarbons (PAHs), in very low metallicity systems with JWST are revealing that PAHs do exist in those environments, but were previously missed owing to the very small size (pc-scale) of the dense regions in which they can form and survive.

Planet formation remains one of the key unsolved challenges in modern astrophysics. Recent exoplanet discoveries and high-resolution observations of protoplanetary disks are reshaping our understanding, prompting a re-evaluation of classical planet formation theories. The omnipresent disk sub-structures helped us to solve the most significant challenges and are driving a new generation of planet formation models. At the same time, increasingly precise laboratory measurements of the Solar System materials provide invaluable benchmarks for the models, giving insights into timescales of planet formation and the large-scale mixing processes. In this talk, I will discuss the understanding of the Solar System formation, which is currently emerging from the synergy of numerical models and meteorite studies.

Over the next decade, large galaxy surveys will map billions of galaxies and probe cosmic structure formation with high statistical precision. This talk will outline opportunities and challenges of cosmological analyses in the presence of complex systematic effects using recent results from the Dark Energy Survey as pathfinder examples. In particular, I will describe different cosmological probes measured from photometric data and summarize the recent progress on combining galaxy clustering, weak lensing, cluster clustering and cluster abundances, as well as constraints on astrophysics from small scales. I will conclude with an outlook on cosmology analysis plans and opportunities for future, much larger experiments such as Rubin Observatory’s LSST, Roman Space Telescope and overlapping Cosmic Microwave Background surveys.

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.

More than 7500 extrasolar planets are known, most of them are located within our solar neighborhood where they orbit stars different than our Sun. How does the climate differ on extrasolar planets that orbit such different host stars? By building and utilized virtual laboratories temperature, wind and cloud maps of such extrasolar planets can be predicted and studied. Our virtual laboratories are therefore vital tool to interpret observations from, e.g. space missions like CHEOPS and JWST, and to make predictions for future missions like PLATO and NewAthena. For this, our present focus is on giant gas planets since they have observable atmospheres, and hence, enable us to link modeling and observation to understand their physics and chemistry.

Clouds most often block the view into the atmospheres and hence, hinder the spectroscopic in-depth characterization of the many known exoplanets. Of particular interest is therefore the understanding and the modeling of cloud formation which forms a tight feedback-loop with the local temperature but also the local gas phase composition. The local gas phase is further affected by the external high-energy radiation, including stellar energetic particles and cosmic rays. I will demonstrate why gas giant exoplanets are exciting objects that allow to study cold, cloud forming and hot, ionizing thermodynamic regimes in one and the same objects.

The MHONGOOSE Large Survey Project is obtaining ultra-deep 21-cm neutral hydrogen (HI) observations with the MeerKAT radio telescope to map the distribution and kinematics of the low column-density gas in and around 30 nearby star-forming spiral and dwarf galaxies. These deepest resolved HI observations of nearby galaxies to date serve to put additional constraints on the role of accretion of cold gas in the replenishing of these galaxies' gas reservoirs. Observations for the survey have just completed and MHONGOOSE is routinely reaching its target HI column density sensitivity of a few times 10^17 atoms cm^-2, two orders of magnitude lower than the typical values found in galaxy HI disks. Our full-depth data show that the outskirts of our galaxies are complex and dynamic environments, with many potential accretion and interaction features visible in HI that only now become visible due to the excellent column density sensitivity.  We detect a significant number of uncatalogued low-mass dwarf galaxies, which enable "Local Group science" in environments at tens of Mpc distance. A first comparison of the MHONGOOSE observations with simulated HI maps from recent cosmological simulations show a marked difference in kinematics and morphology, indicating that cold gas accretion is likely happening in a more gentle way. The sensitive MHONGOOSE observations point the way to a better understanding of the role of gas accretion in galaxy evolution in the nearby universe and identifies opportunities for new HI surveys with the upcoming SKA-MID telescope.

Neutrinos are fascinating particles heralding the dawn of multi-messenger astronomy. Neutrinos affect the stellar dynamics, drive the formation of new elements, and carry signatures of the yet mysterious physics governing the most energetic transients in our universe. Recent developments on the role of neutrinos in cosmic sources will be reviewed together with the most exciting multi-messenger detection prospects.

Galactic cosmic rays and stellar energetic particles are relativistic particles that reach exoplanets. Depending on their energy, they can penetrate exoplanetary atmospheres, similar to what occurs on Earth. The main properties, relevant for these energetic particles, that vary for exoplanetary systems in comparison to the solar system are the stellar winds properties, the exoplanet atmosphere composition and the stellar energetic particle spectrum. The properties of stellar energetic particles for stars other than the Sun remain elusive.

For exoplanetary atmospheres, one of the most important effects due to Galactic cosmic rays and stellar energetic particles is that they ionise the atmosphere. This ionisation leads to exotic chemistry depending on the atmospheric composition. Energetic particles can also drive the formation of prebiotic molecules, the building blocks of life in exoplanet atmospheres. These effects are also relevant for the early Earth atmosphere.

I will discuss our simulation results which show the ionising impact of energetic particles in exoplanetary atmospheres and the early Earth atmosphere. I will show how the stellar wind can affect the energetic particle flux reaching an exoplanet. Finally, I will discuss how JWST could detect the signature of energetic particle-induced chemistry in an exoplanet atmosphere. Such a detection could be used to constrain the energetic particle flux impacting on the exoplanet atmosphere.

The discovery of over 5,000 exoplanets has revolutionized our ability to address fundamental questions about planetary habitability and evolution: Are there Earth-like worlds in the Universe? Can they support life? My research accelerates the discovery and characterization of habitable planets by combining cutting-edge observations with advanced models to characterize the atmospheres and surfaces of rocky and low-temperature exoplanets, trace their evolutionary pathways, and search for signs of liquid-water oceans.

In this talk, I will discuss recent breakthroughs in the study of rocky exoplanets, including the first detection of a magma-ocean atmosphere on 55 Cancri e and the discovery of a volcanic, SO₂-rich atmosphere on L 98-59 b using JWST. These findings provide unprecedented insights into the interplay between geological processes and atmospheric evolution, establishing the emerging field of exoplanet geology. I will also present ongoing efforts to identify liquid-water conditions on temperate sub-Neptunes, illustrating how innovative models, such as our next-generation planetary atmosphere framework, EPACRIS, enable us to predict key atmospheric signatures and interpret groundbreaking JWST observations. 

Finally, I will discuss the path forward for characterizing Earth-like planets and highlight how today’s exoplanet studies drive scientific and technological priorities of future exploration.

Observational surveys of the distribution of matter in the universe are becoming ever more precise and continue to be extended to smaller scales. This necessitates accounting for the fact that baryons do not precisely trace the dark matter. The redistribution of baryons by galactic winds, which is the major bottleneck in our understanding of  galaxy evolution, therefore requires a convergence between models of large-scale structure and cosmology. I will present results from the FLAMINGO suite of large-volume cosmological, hydrodynamical simulations. The fiducial simulations have been calibrated using machine learning to reproduce the low-z galaxy mass function and cluster gas fractions, but the suite also includes systematic variations in the galaxy formation model and cosmology. The simulations provide insight into the importance of baryonic effects for cosmology using large-scale structure and galaxy clusters.

Quantum Computing (QC) is a paradigm with disruptive potential in many areas of computational sciences and large projected impact in research, industry and society. In my talk I will provide a general overview of the main concepts of QC and how it can be integrated into the High-Performance Computing ecosystem as a suitable tool for astronomy and astrophysics. Although application areas in these disciplines are in the first stages of exploration, a few promising directions will be highlighted. Finally, the access paths to QC systems for the local research community will be described.

Over the past 15 years, the Atacama Large Millimeter/submillimeter Array (ALMA) in the Chilean desert has revolutionized our understanding of planetary formation. ALMA has not only provided the expected large samples and high-resolution images of planet-forming material, but it has also led to groundbreaking discoveries that challenge existing theories. One of the most striking revelations is that planets form much faster than previously thought. In this talk, I will explore the key concepts and scales involved in the process of building planets from micrometer sized cosmic dust. I will discuss how theory and observations help us reimagine how planetary systems, both similar and very different from our own, are formed.

The boundaries of relativistic black hole jets—at the interface between the jet and the disk wind—lie at the core of our recent understanding of jet-powered phenomena. They harbor intense velocity and magnetic shears, which provide the free energy needed to power a number of observational signatures. We demonstrate that magnetic reconnection—a process by which opposite field lines annihilate, releasing their energy to the plasma—ultimately governs dissipation of the available free energy at jet boundaries. Reconnection resulting from the nonlinear evolution of Kelvin-Helmholtz type vortices can naturally explain the limb-brightened radio emission of AGN jets, such as M87. Also, inverse Compton scattering within the chain of magnetic islands / flux ropes self-consistently created by reconnection at the jet boundaries can power the mysterious hard X-ray “coronal” emission of X-ray binaries. We will also argue that reconnection-driven hadronic acceleration in the coronal regions of NGC 1068 may be the source of the TeV neutrinos recently detected by IceCube.

Observing campaigns have revealed a great diversity in exoplanetary systems whose origin is yet to be understood. How and when planets form, and how they evolve and interact with their birth environment, the protoplanetary disks, are major open questions. Protoplanetary disks evolve while planets are forming, implying a direct feedback between the processes of planet formation and disk evolution. These mechanisms leave clear imprints on the disk structure that can be directly observed. In this talk, I will review recent observational results on protoplanetary disks, in particular those from the exoALMA Large Program, the first sub-millimeter planet hunting campaign. With exquisite molecular line observations, the velocity structure of fifteen protoplanetary disks revealed a variety of kinematic perturbations possibly due to embedded protoplanets, (magneto-)hydrodynamical instabilities or winds.