Lodewijk Woltjer Lecture

Prof. Isabelle Baraffe obtained her PhD in astrophysics from the University of Paris VII and the University of Göttingen. She moved to postdoc position at the Max-Planck Institute for Astrophysics and then University of Göttingen, before becoming getting a CNRS position at the Centre de Recherche Astrophysique (CRAL) of the Ecole Normale Supérieure (ENS) in Lyon. She joined the University of Exeter in 2010. Her field of research has focussed on stellar and planetary physics. She has been awarded several international prizes and distinctions, among which the Viktor Ambartsumian International Science Prize in 2020 and the Bronze medal from the Centre National de la Recherche Scientifique in 1999. She has been recipient of two Advanced European Research Council (ERC) grants in 2013 and 2018.

Prof. Isabelle Baraffe has produced important work in the fields of stellar and planetary astrophysics, encompassing a wide range of physical domains, from Earth-like planets to very massive stars and compact binaries. Her work aims at understanding and properly describing the physical processes characteristic of the formation, structure and evolution of substellar (planets, brown dwarfs) and stellar objects.

With her collaborators Gilles Chabrier and France Allard, Prof. Baraffe made fundamental contributions to the domain of brown dwarfs and low-mass stars (the dominant stellar population in galaxies). Brown dwarfs are not massive enough to sustain or even ignite hydrogen fusion in their core and provide the missing link between stars and planets. They were discovered only in 1995. Isabelle Baraffe developed along the years a coherent theory for describing the internal and atmospheric structures of low-mass stars and brown dwarfs based on state-of-the-art description of all the micro-physics characteristic of these objects. The Baraffe et al. models explain and even predict all the peculiar observational properties of the aforementioned astrophysical bodies. These models revolutionised the field and established a new paradigm that has sustained for more than 20 years. Her models are widely used by the community to interpret observations and to develop new observational strategies.

Recently, Baraffe demonstrated that early phases of accretion during the birth of the object have a crucial impact on the evolution of young low mass stars and brown dwarfs, even long after accretion has ended. This idea completely changed the standard picture of the early evolution of nascent stars and brown dwarfs, and explained various puzzling properties of young objects, leading to a revision of the standard concept of early phases of evolution.

With Chabrier and Travis Barman, Baraffe developed a general theory that described the inner structure, atmospheric properties and evolution of planets over the entire mass range from Earth-mass to Jupiter-mass bodies. Their models include not only the essential planetary input physics, but also peculiar processes, such as atmospheric evaporation due to the intense parent star incident flux for the short-period transiting planets, double-diffusive layered convection and energy dissipation in the interior due to tidal effects. These models are used widely by the community and provide a theoretical foundation for the analysis of observational data obtained with the largest telescopes worldwide.

While in Exeter, she initiated a major interdisciplinary project, gathering several institutes in the UK and France, in the field of exoplanet atmospheric dynamics. She led the development of the most advanced, three-dimensional radiative hydrodynamics models of exoplanet atmospheres, which are necessary to analyse the wealth of data expected from new generations of telescopes, and to obtain key information such as planet atmospheric chemical composition, the necessary path to better understand planet formation and to detect biosignatures on Earth-like planets.

Prof. Baraffe was awarded an advanced European Research Council (ERC) grant in 2013, which allowed the development of a highly novel numerical tool, specifically the fully compressible, time implicit, three-dimensional (3D) code MUSIC (MUlti-dimensional Stellar Implicit Code). The significant potential for this new tool was recognized by the award of a second advanced ERC grant in 2018.

Prof. Isabelle Baraffe's personal ambition is to advance the very frontiers of astronomy, taking stellar and planetary physics to a new era and to make it one of the major domains of 21st century astronomy. To achieve this, Professor Baraffe has led highly innovative projects such as the development of complex numerical tools that combine state-of-the-art physics and computational methods.

All these achievements make Prof. Isabelle Baraffe an outstanding awardee of the Lodewijk Woltjer Lecture.

Prof. Bożena Czerny (born Muchotrzeb) studied theoretical physics at Warsaw University, where she obtained her MSc degree in 1974. In 1978 she started working as a research assistant at the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences (CAMK), Warsaw, Poland in the field of accretion and obtained her PhD in 1984. Prof Czerny was gradually promoted at CAMK and eventually reached full professor position in 1996. In 2015 she moved to a full time professor position at the Center for Theoretical Physics, Polish Academy of Sciences, Warsaw, Poland, keeping a part-time employment at CAMK till the end of 2017. Prof. Czerny has seved in several committees, such as International Union of Pure and Applied Physics, Council of the National Science Center, and Polish Astronomical Society (President in 2011-2013). She served as a Scientific Editor of the American Astronomical Society journals from 2012 to 2020. She further was awarded in 2019 the Ernst Mach Honorary Medal for Merit in the Physical Sciences awarded by the Czech Academy of Sciences.

Prof. Czerny focuses on modelling the physical processes close to black holes in the centers of active galaxies and in stellar binary systems, and on comparison of the models to the observational data. Her early works started with the understanding of the matter inflow from the inner edge of the disk toward the black hole horizon, which culminated in the contribution to formulation of the slim disk theory. She was among the pioneers in studies of the X-ray variability of active galactic nuclei and of the vertical stratification of the accretion disks, including the idea of the disk warm corona, collaborating with Leicester, Cambridge and Harvard colleagues while working on the emission from accretion disks in AGN. She studied the accretion disk instabilities, comparing their consequences to the observational data. In 2011 she formulated a new model of the Broad Line Region structure in active galactic nuclei, based on the radiation pressure acting on dust, called FRADO (Failed Radiatively Accelerated Dusty Outflow) model. Recently, she has focused her attention to the application of the light echo measurements of distant quasars to determine the distance to these sources and to derive constraints on the cosmological parameters.

Prof. Czerny was a long-time scientific editor of The Astrophysical Journal published by the American Astronomical Society. Her lecturing and publishing activities include the popularization of astronomy and science in general. Her expertise in research led her to win numerous grants. She is currently PI of a 5-year Maestro grant awarded by the Polish National Science Centre, and since Autumn 2021 she is one of the four PIs of an ERC Synergy Grant aimed to use multi-probe methods to establish the distance scale in the Universe with unprecedented accuracy, which includes also the quasar-based constraints.

Prof. Helmi studied astronomy with a specialization in theoretical physics at the Universidad Nacional de La Plata in Argentina, where she obtained her MSc degree in 1994. In 2000, she obtained her PhD cum laude from Leiden University in the Netherlands, for her research on the formation of the Galactic halo. After that she briefly returned to the Universidad Nacional de La Plata as a postdoc, and in 2001 she took a postdoc position at the Max Planck Institute for Astrophysics in Germany. A year later, she returned to the Netherlands as a NOVA fellow at Utrecht University. In 2003, she was appointed Assistant Professor and in 2014 promoted to Full Professor at the Kapteyn Institute of the University of Groningen, where she has been since then. Between 2007-2011 she was member of the Young Academy of the Royal Netherlands Academy of Arts and Sciences, and since 2017 is full member of the Royal Netherlands Academy of Arts and Sciences. In 2019, as a highlight of her career, Prof. Helmi received the prestigious Spinoza Prize, the highest award in Dutch science. In this same year, she was appointed Deputy Scientific director of the Dutch Research School for Astronomy (NOVA).

Prof. Amina Helmi is Professor of Dynamics, Structure and Formation of the Milky Way at the Kapteyn Institute of the University of Groningen in the Netherlands. She is one of the founders of the field of Galactic Archaeology which aims to reconstruct the history of (nearby) galaxies based on the current positions, motions and the chemical composition of stars. She is well-known for the discovery of debris from galaxies that have merged with the Milky Way, mostly recently using data from the Gaia mission, as well as for dynamical modelling of the Milky Way to understand the distribution of dark matter.

Prof. Helmi's approach to research is to develop theoretical models (analytic work and simulations), and to use them to make predictions as well as to interpret observational datasets, at the interface of galactic astronomy and cosmology. During her early career, as part of her PhD research, she discovered the remnants of a small galaxy that was absorbed into our young Milky Way billions of years ago. This collection of stars has since been known as the Helmi stream. Since then, Helmi's models and experiments have considerably expanded our knowledge about the shape, structure and history of the Milky Way and that of its satellites. She has been involved in the European Space Agency Gaia since its conception/adoption, and has been one of the leaders in the exploitation of this revolutionary mission. In 2018, Prof. Helmi used this dataset to discover and characterize the last big merger the Milky Way experienced, which took place approximately 10 billion years ago and was a true milestone in Galactic history. The debris from the merged galaxy, which she named Gaia-Enceladus, dominates the stellar halo near the Sun and the event led to the thickening of the disk present at the time and probably triggered the formation of the thick disk.

Prof. Helmi has acquired major grants for her research, such as the prestigious Vidi and Vici grants from the Netherlands Research Council, and an ERC Starting Grant. She has also received numerous prizes, including twice the Amelia Earhart Fellowship Award, the Christiaan Huygens Prize from the Royal Netherlands Academy of Arts and Sciences for her PhD thesis, and recently the Suffrage Science Award and the Spinoza prize. She is currently a member of both the Royal Holland Society of Sciences and Humanities and the Royal Netherlands Academy of Arts and Sciences. She was member of the Astronomy Working Group of ESA between 2006 and 2010, is currently the science representative for the Netherlands on the European Southern Observatory Council and member of the committee currently advising the scientific director of the European Space Agency on the Voyage 2050 program.

Prof. Helmi regularly shares her fascination for astronomy and her most recent discoveries with the general public through media and public lectures, with the hope of raising science literacy and gender equality in academia and beyond.

Prof. Alvio Renzini studied in Pisa, where he received a Physics Diploma from the University of Pisa and the Scuola Normale Superiore in 1963. After holding a fellowship at the Scuola Normale for three years he obtained an Astronomer position at the Astronomical Observatory of Bologna in 1967. In 1970, he was appointed a professor at the University of Bologna, a position he held until 1995 when he moved to ESO as VLT Program Scientist. Since his retirement from ESO in 2005, he is Associate Scientist of INAF at the Astronomical Observatory of Padova. He also was a visiting scientist/professor at numerous institutions around the world and received several awards and honorary appointments.

Prof. Alvio Renzini's research and contributions to astronomy are characterised by unusual breadth and depth. During his early career, he wrote seminal papers on stars, in particular their advanced evolutionary stages and chemistry. Over time, his interests broadened and included the evolution of stellar populations and galaxies, nucleosynthesis, the intergalactic medium in galaxy clusters, and more. As a theoretician, he participated in several prominent galaxy surveys and provided inspiration and support for the interpretation of data. In doing so, he displayed an unwavering focus on the underlying physical processes in astrophysical phenomena which allowed him to cut through their complexity, resulting in arguments of beautiful clarity and deep insight.

Prof. Renzini has been much more than a brilliant scientist with wide-spread theoretical and observational experience. When he moved to ESO in 1995 and became VLT Program Scientist, he took on a most important and influential role in shaping ESO's Very Large Telescope Project. He provided guidance for the optimal use of the VLT and its future instrumentation and suggested crucial upgrades to existing instruments. He fostered survey work at ESO, also in combination with other facilities, like the Hubble Space Telescope. As VLT program scientist he contributed in a major way to the success of ESO and, in turn, the scientific excellence of European Astronomy over the last decades.

Prof. Renzini has been a mentor of many successful scientists who now hold prestigious positions around the world. He is a member of the 'Accademia Nazionale dei Lincei', Rome, the 'Instituto Veneto di Science, Lettere e Arti', and an Honorary Fellow of the Royal Astronomical Society.

Licia Verde was born in Venice, Italy in 1971; she graduated in physics from the University of Padova (1996) and defended her PhD thesis at the University of Edinburgh in 2000. She then moved for postdoctoral appointments at Rutgers University and Princeton University where she was Chandra Fellow and Spitzer fellow. There she seized the opportunity to join the WMAP science team. She became faculty at University of Pennsylvania (2004) and then, in the fall of 2007, a professor at ICREA (Institució Catalana de Recerca i Estudis Avançats) in Barcelona. Since 2010 she leads the Cosmology and Large Scale Structure Group at the Instituto de Ciencias del Cosmos of University of Barcelona. She is the recipient of two ERC IDEAS grants: Starting (2009) and Consolidator (2016). She has shared with the WMAP team the Gruber Cosmology prize (2012) and the 2018 Breakthrough prize for Fundamental Physics. She was among the Thompson Reuters ISI Highly cited researchers in 2015. She was awarded the 2017 Narcis Monturiol medal and the 2018 Premi Nacional de Recerca, that recognises a researcher who has recently contributed significantly and internationally to the advancement of a scientific discipline in any of its fields: human and social sciences, life sciences and health, engineering and technology and experimental sciences. She is a member of the Young Academy of Europe.

Prof. Licia Verde is a cosmologist who addresses questions such as origin, composition and evolution of the Universe, with special attention to statistical methodology.

Shortly after graduating from her PhD, Verde made her mark by analysing a powerful but incredibly challenging statistical property of galaxy surveys related to higher-order correlations. She showed that galaxies of the Anglo Australian Two-degrees galaxy redshift survey (the largest three-dimensional galaxy survey available then) trace the distribution of the elusive yet ubiquitous dark matter (which makes up to about 80% of the mass of the Universe). This result indicated that the galaxy distribution can be used to study the dark matter one.

Prof. Verde then joined the science team of the Microwave Anisotropy Probe (later renamed Wilkinson Microwave Anisotropy probe WMAP). Verde participated in analysis and interpretation of the Cosmic Microwave Background data from the WMAP satellite. This analysis was pivotal in establishing what is today the standard cosmological model. In this model, the Universe is composed of dark matter and dark energy and the standard matter, as we know it, makes up to only about 5% of the Universe. The galaxies and large scale structure we see today arose from tiny initial quantum fluctuations that got amplified by gravity over 13.7 billion years of evolution.

Prof. Licia Verde then turned her attention to developing rigorous statistical tools to analyse surveys of the Universe and thus connect theoretical models to the observations. Thanks to two ERC grants she has established a vibrant and highly international research group in physical cosmology at the University of Barcelona. Under her lead, the group has contributed to some of the most important results from the Baryon Acoustic Oscillations Survey, part of the Sloan Digital Sky Survey: measurements of the expansion history of the Universe and the formation of cosmological structures as well as constraint on cosmological parameters describing structure and detailed composition of the Cosmos. Her group is now involved with two forthcoming surveys: the Dark Energy Spectroscopic Instrument survey and the Euclid mission. These surveys will provide detailed three dimensional maps of galaxies and large-scale cosmological structures covering unprecedented volume: the survey volume being a sizeable fraction of the entire observable Universe. If WMAP marked the inception of precision cosmology, the advent of such large surveys is propelling cosmology in the "big data" era.

Prof. Licia Verde has supervised 7 master students, has or is supervising 7 PhD students and mentoring 20 externally recruited postdocs. She is a promoter of Girls in Science, Technology, Engineering, and Mathematics disciplines, she is passionate about outreach and science communication especially to young ages, diversity and inclusion in the work place and the future of scholarly communication.

Prof. Conny Aerts graduated as mathematician from Antwerp University in 1988 and defended her PhD thesis in astrophysics at KU Leuven in 1993. She continued her career as Postdoctoral Fellow of the Research Foundation Flanders until 2001, defining an independent research track and performing numerous stays abroad in Europe, Chile and the USA to achieve it. She was appointed as Lecturer (2001), Associate Professor (2004), and Full Professor (2007) at KU Leuven. Since 2011, she is Director of the Institute of Astronomy in Leuven. Since 2004, she also leads the Chair in Asteroseismology at the Radboud University Nijmegen. She is the recipient of 2 ERC Advanced Grants (2009 and 2016) and was awarded the Francqui Prize in 2012. Conny Aerts is an Honorary Fellow of the Royal Astronomical Society since 2010, and Commander in the Order of Leopold since 2016, the highest civilian recognition offered through Royal Decree by His Majesty King Philippe for services to the Kingdom of Belgium.

Prof. Conny Aerts is a stellar astrophysicist, working on stellar structure & evolution, with a focus on variable stars. She is a pioneer in the research domain of asteroseismology. This topic received an immense boost thanks to recent space missions, delivering high-precision uninterrupted space photometry. This kind of data brought her to the cores of stars and in particular to their interior rotation and mixing. Conny Aerts and her team developed rigorous mathematical methods to detect and identify non-radial pulsation modes in stars from high-precision spectroscopy and space photometry. Her team also designed and applied supervised and unsupervised statistical clustering methods for big data sets to find variable and binary stars of various kinds, as starting point for follow-up campaigns for asteroseismology. These methods recently led to the discovery and interpretation of numerous gravity-mode pulsators, opening new probing power for stellar interiors. Thanks to her appointment as Chair in Asteroseismology at the Radboud University Nijmegen in 2004, Conny introduced herself to the topic of subdwarf stars, their binarity and pulsations. In 2009, Prof. Conny Aerts was awarded an ERC Advanced Grant, PROSPERITY to evaluate stellar models from CoRoT and Kepler space asteroseismology. Under her leadership, her PhD students made major contributions, such as the discovery of non-radial pulsation modes, dipole mixed modes, and non-rigid rotation in red giants, following her earlier detections of core overshooting and core rotation in massive stars. This culminated in the prestigious 2012 Francqui Prize, also termed Belgian Nobel Prize. Conny Aerts was the first woman to receive this prize in the option Science & Technology since its creation in 1933. The ERC offered her a second Advanced Grant, MAMSIE, in 2016 to bridge stellar physics and 3D hydrodynamics with the aim of remedying shortcomings in stellar evolution theory of massive stars.  Conny Aerts supervised more than 40 Master students, 25 PhD students, and 15 externally recruited postdocs. She also took part in more than 50 PhD examination committees. She teaches various courses in the Master Astronomy & Astrophysics at Leuven & Nijmegen universities, while she also gives training on gender-related, mentor-mentee and science communication & outreach topics. Conny Aerts is member of numerous international committees and boards. As Belgian Principal Investigator, she is heavily involved in the ESA M3 space mission PLATO that should get launched by 2026.

Bengt Gustafsson is a renowned Swedish astrophysicist born in 1943 in Uppsala, Sweden. He started his studies at Uppsala University, then spent two years at the Nordic Institute for Theoretical Physics (Nordita) in Copenhagen before obtaining his PhD degree at Uppsala University in 1974. He became professor of astrophysics at Stockholm University and, in 1987, professor of theoretical astrophysics at Uppsala University. He has also been guest professor at the University of Maryland (USA), at the University of Asmara (Eritrea), and at the University of Texas (USA). After an extremely active and fruitful career, Bengt Gustafsson is now professor emeritus at Uppsala University and affiliated professor at Nordita (now in Stockholm).

Bengt Gustafsson has worked extensively on the theory of stellar atmospheres, the interpretation of stellar spectra, on the chemical evolution of galaxies, and, more recently, on the early history of the Sun. He has published about 400 scientific papers some of them related to seminal studies leading to significant advances as attested by some 15'000 citations. He has also written a number of popular articles and books, and has contributed on philosophical and science-policy issues. He has served in various prestigious national and international committees, such as the Nobel Committee of Physics, the ESO Council, and the astronomy/space science panel of the European Research Council (ERC). He was the chairman of the Committee on Freedom and Responsibility in the conduct of Science in the framework of the International Council for Science (ICSU).

Thibault Damour is a French theoretical physicist born in 1951 in Lyon. After studies at the Ecole Normale Supérieure de la rue d'Ulm (1970-1974), he obtained his Thèse de Doctorat de troisième cycle in 1974 (Université de Paris VI), and, later, his Thèse de Doctorat d'Etat ès Sciences Physiques (Université de Paris VI, 10 janvier 1979). He started his career (1977-1989) as researcher at the Centre National de la Recherche Scientifique (CNRS). Since 1989 he is permanent professor at the Institut des Hautes Etudes Scientifiques (IHES).

Thibault Damour is a theoretical physicist working on consequences of Einstein's theory of General Relativity, and its String Theory extensions. He has made lasting contributions on: the theory of black holes, the dynamics and relativistic timing of binary pulsars, the generation of gravitational waves, the motion and coalescence of black holes, as well as several aspects of early cosmology. He has introduced in 2000 (with several collaborators) a new method for describing the motion and gravitational radiation of coalescing binary black holes, which gave the first prediction of the gravitational wave signal observed by LIGO in September 2015. His work was crucially used for interpreting the observed signal and measuring the masses and spins of the two coalescing black holes.

Ewine F. van Dishoeck's research is at the boundary of astronomy, laboratory astrophysics and chemistry and uses ground- and space-based observatories in the infrared and sub-millimetre range. Her current scientific focus is on the physical and chemical evolution of material from interstellar clouds to planet-forming disks and the importance of molecules as diagnostics of the star-formation process.

Ewine F. van Dishoeck is a Dutch astronomer and chemist born in 1955 in Leiden. Graduated at Leiden University, she held positions in the United States at Harvard, Princeton and Caltech from 1984 to 1990. She returned to the University of Leiden in 1990, where she became professor of molecular astrophysics in 1995. She is also an external scientific member of the Max Planck Institute for Extraterrestrial Physics in Garching. She authored or co-authored more than 450 refereed publications with over 25'000 citations and holds many national and international science policy functions, including scientific director of the Netherlands Research School for Astronomy (NOVA), president of Division H of the International Astronomical Union, former member of the Board of the Atacama Large Millimeter/submillimeter Array (ALMA), co-PI of the MIRI instrument on the James Webb Space Telescope (JWST) and co-I of the HIFI instrument on the Herschel Space Observatory. She has been fortunate to receive the Dutch Spinoza award, an ERC Advanced grant, and the Dutch Academy Prize. She is a Member of the Dutch Royal Academy of Sciences and the Leopoldina German Academy of Sciences, Foreign Associate of the US National Academy of Sciences, and Foreign Member of the American Academy of Arts and Sciences.

Rashid A. Sunyaev was born and finished secondary school in Tashkent, before graduating from the Moscow Institute of Physics and Technology in 1966. He then became the PhD student of Yakov Borisovich Zel'dovich, who knew how to inspire his young colleague. The two scientists collaborated tightly over 22-years at the interface of theory and experiment. Sunyaev was Full Professor at the Moscow Institute of Physics and Technology from 1975 to 2001. He was first the Head of the Laboratory of Theoretical Astrophysics at the Space Research Institute of Moscow (1974-1982) and then of the High Energy Astrophysics Department in the same institute (1982-2002). Since 1992 he is Chief Scientist at this institute of the Russian Academy of Sciences. He became director of the Max-Planck Institute for Astrophysics in 1996 and then Maureen and John Hendricks Visiting Professor at the Institute for Advanced Study of Princeton in 2010. During his extremely successful career, Sunyaev has received numerous honours and awards all around the world.

Suzy Collin-Zahn was born and studied in Paris. Her first scientific interests were in the domain of plasma physics applied to the solar corona. She turned to the study of AGN in the early days of the subject and ever since contributed original elements to the slowly emerging puzzle. Suzy has led a lively research group in the Paris observatory for several decades. She contributed to astrophysics through her research, but also through her teaching, the popular books she wrote and her participation in national and international committees. Suzy Collin-Zahn is now emeritus associate astronomer at the Paris observatory.

Prof. Wolfgang Hillebrandt was born in 1944. He studied physics and mathematics at the University of Cologne were he obtained his PhD in 1973. After some time at Caltech in California and some at the Technical University of Darmstadt, he joined the Max Planck Institute for Physics and Astrophysics in Munich in 1978 and then Garching, where he became director. He is Honorary Professor at the Technische Universität München.

Prof. George Miley was born in 1942 and has dual Irish and Dutch nationality. He studied at University College Dublin and obtained his PhD in 1968 from the University of Manchester, home of the Jodrell Bank radio telescope. He joined the staff of Leiden University in 1970 and has spent several years in the US, including 4 years on the staff of the Space Telescope Science Institute. Prof. Miley is the initiator of the "Universe Awareness" programme aimed to inspire economically disadvantaged children with astronomy and, as IAU Vice President, he has recently led the development of the IAU Strategic Plan 2010 - 2020, "Astronomy for the Developing World".

Professor Lodewijk Woltjer is one of Europe's outstanding astronomers of the second half of the twentieth century. First of all Lodewijk Woltjer made significant contributions to theoretical astrophysics, from his fundamental work on the Crab nebula and his studies on hydromagnetic equilibrium to the energy source of Radio Galaxies and Quasars. After serving as chairman at the Astronomy Department of Columbia University in New York, a position he held for ten years, Lodewijk Wolter in 1975 became Director General of the European Southern Observatory (ESO). Under his leadership ESO established itself as one of the world's leading astronomical institutes.

Lodewijk Woltjer realised with great foresight what needed to be done in order for Europe to bridge the gap that existed in observational astronomy with other countries. He initiated the development of new instrumentation and telescope technology whose highlight, the Very Large Telescope, has become the world's most successful ground- based observatory and has re-established Europe's leadership in observational optical astronomy.

Twenty years ago Lodewijk Woltjer initiated the foundation of the European Astronomical Society and became its first president. A few years later Lodewijk Woltjer became president of the International Astronomical Union.