Riccardo Giacconi in Milano

We all owe him, as well as Bruno Rossi and Beppo Occhialini, our jobs. We owe him a window on the Universe, but also a view on how to be scientists, in a modern and collaborative way. With hard rules, but also with a challenging and superior goal, though not easy to reach. / easily reachable.

His bond with Milan was important: the University where he studied and briefly taught was there, as well as his beginning and his end. His last official participation in an astronomical congress was in 2012, in one of the meetings organized for the 50th anniversary of X-ray astronomy. We consider indeed X-ray Astronomy officially born in 1962 and glorified with Giacconi’s Nobel prize in 2002. In those celebration meetings, all the best was wished for the incoming next 50 years of X-ray Astronomy and Riccardo was the guest star, named as the “father of X-ray Astronomy”.

Two major congresses took place that year: in September in Mykonos – with a sky as blue as only Greece can have, against the whitest of the houses – Riccardo reminded us the technical choices which led to the Aerobee launch in 1962. But it was in Milan, in October, that he granted us with a sort of summary of his career. The article that describes his speech is very explicit in its intent: to clarify some past controversies and to express hope for the future of the discipline. This is clearly written from the very first rows.

But the main lesson can be find in the paragraphs’ titles: “Learn Think Plan and Do”. And I perfectly remember (and I also used it to close some of my conferences) his wish, or, better, his imperative:

“WE MUST HOWEVER ENSURE THAT THE NEW GENERATION OF ASTRONOMERS WILL HAVE THE OPPORTUNITY TO LEARN – THINK – PLAN AND DO. “

He always felt this as his task and it must be his legacy, that has to become our assignment: to let young people, the new generations, have a place to learn and to think, but also to make projects and work with their own hands, to be protagonists of themselves.

In the spring of 1979 Giacconi gave a public lecture in Rome. I was a physics student at the time and noticed that an influential and successful University professor from Rome demonstrated a sort of deference towards Giacconi that I had never seen of him. That episode made me aware of Giacconi’s scientific stature, even before I knew much about the research field that he had created and led for two decades already. After a few years I joined Giacconi’s group at the Harvard-Smithsonian Center for Astrophysics (Cambridge, Massachusetts) as a research fellow. He received me in his office and told me straight out that the model I was determined to work on would lead me nowhere. He then gave me some  alternative ideas and suggested a couple of scientists I could work with. I was very grateful for that: I myself was not persuaded about the model and after a short while my work in his group was thriving. A few months later, Giacconi became the Director of the Space Telescope Science Institute and moved to Baltimore.  Right before that, somebody in Italy asked me to give him privately the message that a “trip to Stockholm would soon take place”: I wrote it on sheet of paper that I placed in an envelope and left with his secretary. Evidently it was not the first, nor would it be the last message of this kind that Giacconi received, if in his scientific autobiography he stated that he considered himself lucky to have always ignored such rumours.

The years I spent in his group at CfA were very productive for me. After my moving back to Europe, I met with Giacconi several times: he always showed interest in my research, despite the fact that I worked on the other side of the ocean and on very different subjects from his, by then. I gradually got to know him better: his strong, generous (and sometimes severe) character was accompanied by joviality and a great sense of humour. He had no appreciation whatsoever for flattery and pretence; in fact, he would occasionally give abrasive replies to people approaching him with adulation. In his powerful roles he quite often had to make important decisions, sometimes difficult and unpopular, but his skills in innovating, managing and giving impulse to the large programs he worked on became about legendary. Yet the way he talked about science was always open and lively; ideas and arguments were key, rather than seniority of participants in a discussion.

In 1991 he accepted a clara fama professorship at Università Statale di Milano, the same he attended as a student in the 50’s. He asked me to join him in teaching the Astrophysics course; I gave the lectures during the periods he spent in the States to continue his work. A few minutes before the beginning of his first lecture, he told me “I really need to make the students understand that I don’t know something”. He thus wanted to express in his lectures what I – at the time a beginning teacher – did my best to hide in mine. The deep meaning of that sentence became clear to me only years later, after I had learned how to learn from my students. Giacconi was an excellent teacher, he had taught for many years at Harvard and Johns Hopkins. The lectures he gave in Milan were beautiful and inspiring. I recorded most of them, including the first three, which are presented here.

In those years Giacconi had an idea he himself ranked among his best ones: a wide field telescope that could map the sky in the X-ray band with unrivalled accuracy, thanks to an innovative design. The ensuing study led to a project for a small size scientific satellite, very much at variance with the gigantic, super-expensive (and often unfeasible) projects that Space Agencies were considering at those times. Together with Guido Chincarini, then director of the Osservatorio Astronomico di Brera, Giacconi  organised a meeting in Tremezzo (Italy) with scientists and representatives of the Italian space agency, industry and political world, in order to promote small and fast scientific space missions, requiring relatively low budgets. Unfortunately the time was not ripe and no consistent development followed. A quarter century later it is now apparent that the aim of that meeting was long-sighted: small, mini, micro satellites and even cubesats have been built and launched across three continents. Giacconi’s part-time activity in Italy was coming to an end: his new appointment as Director of the European Southern Observatory did not permit him to continue.

In 1997 the Festschrift  that Remo Ruffini, Herbert Gursky and I organized in Rome for the 65th birthday of Giacconi was a demonstration of the very high esteem of generations of colleagues and collaborators; many came to celebrate him from the United States and from all over Europe. The participants’ presentations, later collected in a monograph, encompassed scientific results as well as personal memories, and provided an intense, multifaced view of Giacconi’s career.

The “trip to Stockholm” took place in 2002: on October 9th all major Italian newspapers reported the news in large front-page titles and photographs, “An Italian expatriate is Nobel Laureate in Physics” wrote Corriere della Sera; “Giacconi, Nobel Laureate for the invisible Universe” il Sole 24 ore; “An Italian Nobel Laureate in Physics” La Repubblica. The award was in due recognition of his work and the wealth of fundamental results it led to. In the Italian scientific community the enthusiasm was so widespread that Giacconi compared it in jest to that for a Football World Cup victory.

The last time I met Giacconi was in 2012 at the Milan meeting celebrating the 50th anniversary of X-ray Astronomy and, in fact, largely devoted to him. On that occasion he spared some time to hear about the project I was working on: though far from his interests, he asked me cogent questions and gave me his perspective on it. My grateful memory goes to him now, immense scientist and unequalled teacher.

When you interact with a person like Riccardo, you cannot remain indifferent and you end up being influenced in a way or another. What was astonishing for me was his thinking big, but always with a practical side: he had a scientific goal in mind and, to reach it, he was proposing a new satellite, both innovative and feasible! In fact, this was what he had done successfully several times in the past! Unfortunately, with WFXT he did not make it, I say “unfortunately” because this project still has a very high scientific importance after 30 years. We hope that sooner or later the scientific community will be able to construct this mission.

For four years we met frequently. In fact, together with Oberto Citterio, Paolo Conconi, Gianpiero Tagliaferri and the group that worked on X ray optics in Brera, we began to design and develop polynomial grazing wide field optics to show WFXT feasibility. The proposal of the mission was submitted during the Decadal Survey 2010.

Even if at that time it was not selected, the work went on and evolved in the Lynx mission, that we hope will be chosen during next Decadal Survey 2020. Of this period (from 2008 to 2012) I keep many memories and I think I learnt important things. I discovered with time that Riccardo, rather than being a simply rough person, was instead a frank, pragmatic and in-love-with-science man. Besides having a very strong personality (to be euphemistic…), he did not like “yes-men” and always accepted discussion and confrontation au pair.

My dearest memories are linked to the two last occasions in which I met him, at the two conferences in his honour, arranged in 2012 in Mykonos and in Milan, for the 50’s anniversary of X ray astronomy. In Mykonos I had been invited to discuss X-ray optics, speaking also about the pioneering epoch in which Riccardo, Bruno Rossi and their collaborators made the first steps to focus with grazing optics during the 60’s (I was worried to talk nonsensical). When I entered the conference hall early in the morning and very much in advance, I found he was already there and he greeted me warmly. When I expressed him my worries for the talk, he laughed, took me under his arm and went on walking with me around the room for about 20 minutes, talking about many subjects, both scientific and personal. I must confess I was very proud (it is an episode I often tell to my family, a real catch phrase), I was looked at with envy by my colleagues all round, with some of the young ones that from time to time stopped us, to ask for a photo with Riccardo. Milan meeting had been organized by us of INAF and he gave us the gift of being present even if a bad cold was tormenting him. The congress was a great success and I think it was the occasion for his last public speech. We saw him very happy among the main actors of X-ray astronomy. I believe this conference represented for him also a way to solve his conflictual – but loving – relationship with Italy (and especially with Milan). In that occasion he gave us, with Piero Biancucci, a beautiful interview, a sort of moral testament (the video was recorded in Brera’s instrument corridor and is available on Youtube). When I took him by car with Ginevra Trincheri to the Museo della Scienza e delle Tecnologie, where the congress was taking place, as usual I was getting lost in Milan. Riccardo, laughing, made fun of me and started giving me indications, confessing that, after many years, he had never forgotten what in the end was his city.

I had the privilege of a longstanding collaboration with Riccardo Giacconi on the WFXT (Wide Field X-ray Telescope) project, with the whole INAF-OAB team for the development of X-ray optics for this space mission.

The WFXT project has been strongly supported by Riccardo, who, in his creative vision of modern astrophysics, had forecasted how interesting it would be to develop an X-ray optic system with a resolution that is constant on a wide field of view and that is particularly apt for a survey of the X-ray sky. As any expert knows, X-ray optics built using the Wolter 1 scheme allow high angular resolutions only on the optic axis. In wide optical fields aberrations appear that significantly decrease the quality of the image. Riccardo had the intuition of substituting the Wolter 1 optic profile with a polynomial one, which had been studied by C. J. Burrows. With his enthusiasm he persuaded the INAF – OAB team to develop a prototype of an X-ray mirror with this profile. In OAB we were strongly committed to its production and, after a series of developments, we made a SiC mirror, that proved, under X-ray test, that we could reach an angular resolution of 10 arcsec for a field of view of 1°, with the possibility of improvement: the goal at that time was 5 arcsec. This demonstration persuaded the WFXT team to propose to both ASI and NASA this mission to survey celestial X-ray sources in a wide field. The mission was selected for a first phase of study by ASI, but was subsequently dismissed in favour of other programmatic priorities both in ASI and NASA, so the mission could not be accomplished.

I strongly believe in the scientific value this mission continues to have and I hope we will get back to it in the near future.

The collaboration with Riccardo represented a pleasant period of my professional live, as I received a constant stimulation toward technology innovation, together with the build-up of new knowledge in modern management of astrophysical projects, being Riccardo a true master in those aspects.