JEAN-PIERRE LASOTA-HIRSZOWICZ (1942-2024)
Photograph of Jean-Pierre Lasota-Hirszowicz, taken on March 26, 2001 in the IAP library.Credit: Jean Mouette
Jean-Pierre Lasota-Hirszowicz, born in Marseille on October 16, 1942, died in Paris on October 31, 2024, aged 82. He lived in Paris, Oxford and Warsaw with his wife Agnieszka Kołakowska.
Jean-Pierre was a great researcher, loved and respected by all. His scientific career was varied and exemplary. At a very young age, he left France for Poland, where he pursued brilliant studies. In the early 1980s, he arrived in Paris at the Institut d'astrophysique de Paris (IAP), where he was welcomed by the director at the time, Jean Audouze. He already had a solid reputation as a top-level researcher. In 1998, after having been director of the DARC (Département d'Astrophysique Relativiste et de Cosmologie) at the Observatoire de Paris-Meudon, Jean-Pierre returned to the IAP, where he was director of research emeritus at the CNRS since 2009. Jean-Pierre was a man of culture. He was intimately familiar with contemporary history, having lived through some of its most significant episodes himself. He also loved literature. He was very fond of Yasmina Reza, particularly for her distinctive tone. He was currently reading the entire works of Patrick Modiano, whom he said was his favourite French writer. Jean-Pierre was a true man of the Enlightenment, ‘an honest man’ as defined in the 18th century, in other words a man of the world, accomplished, with a cultivated mind and who put intellectual rigour into everything he undertook. Above all, Jean-Pierre was a free man: ‘Liberté, je chéris ton nom’ could be his motto.
Jean-Pierre's career
In 1965, Jean-Pierre defended his master's thesis at the Faculty of Physics at the University of Warsaw. He then defended his doctoral thesis on relativity in 1971 at the Institute of Theoretical Physics at Warsaw University. He first worked at the Nicolas Copernicus Centre of the Polish Academy of Sciences, where he was deputy director for three years. From 1980 onwards, he spent three years in England at Leicester and Cambridge before being recruited by the CNRS in 1983. He joined the DARC (Département d'Astrophysique Relativiste et de Cosmologie) at the Observatoire de Paris-Meudon, where he was director from 1988 to 1998.
Alain Fontaine, Jean-Pierre Lasota-Hirszowicz, Denis Burgarella and Francis Bernardeau, on 29 April 2014, in the IAP amphitheatre.Credit: Jean Mouette
Jean-Pierre was a world-renowned specialist in accretion on compact objects (white dwarfs, neutron stars, black holes), his work on the subject having been recognised by the 2012 Félix Robin Grand Prize of the Sociéte française de physique.
For accretion to occur, the matter must form a disc that allows it to flow progressively towards the central object. While the idea of an accretion disc is well accepted, the physical mechanisms that take place within discs remain the subject of considerable controversy. These have become even more heated since the advent of high-energy X-ray and gamma-ray space observatories, which are placing new constraints on the models.
Jean-Pierre made remarkable breakthroughs in this theoretically very difficult field. In particular, he invented advection-cooled disks. This model has been so successful that the name proposed by Jean-Pierre, ‘ADAF’ (for Advection Dominated Accretion Flow), has now become part of the everyday vocabulary of high-energy astrophysics. This disc model could be applied to the central black hole in our Galaxy, whose weak X-ray and gamma-ray emission is difficult to explain using more conventional models.
Going beyond the ADAF models, Jean-Pierre and his colleagues undertook a comprehensive review of the physics describing flares in X-ray emitting binary systems. This work was the subject of a review that has become one of the classics in the field. We should also mention several remarkable results on the evolution of binary systems in general relativity, including the discovery of the Abramowicz-Lasota effect, in which the centrifugal force ‘flips’ and modifies the characteristics of the orbits around a black hole.
Other major results obtained by Jean-Pierre include his 1988 work on ‘slim accretion disks’ around black holes (nearly 1,500 citations, with a remarkable rate of citations increasing steadily over time), which revealed the existence of a new accretion regime close to the Eddington limit, leading to quasi-periodic flashes in the disk.
On the physics of active galactic nuclei, Jean-Pierre contributed in 2007 to an article elucidating the way in which radio luminosity depends on the accretion rate as well as the mass and spin of the central black hole. Here again, this seminal paper is still widely cited and continues to inspire numerous developments.
Jean-Pierre worked extensively within the CNRS-INSU and the European Union: as an expert evaluator of scientific proposals for a number of funding bodies (notably CNRS, the French Ministry of Research, the European Commission (Marie Curie), but also for the Polish Science Foundation, the National Research Foundation of South Africa, the Austrian Science Foundation, Nordita, etc.). He was also editor-in-chief of the Journal of Instrumentation (2011-2017). He has been a referee in many professional journals such as Acta Astronomica, A&A, ApJ, Classical Quantum Gravity, MNRAS, Nature and Science.
Jean-Pierre was a member of the Comité national de la recherche scientifique (1991-1995). He was also scientific advisor to the Chairman and Director of the CNRS (2002-2012).
Jean-Pierre was a major player in the birth of what is now known as astroparticle physics, which straddles astrophysics, theoretical physics, nuclear physics and particle physics. As chairman of the CNRS's interdisciplinary ‘Astroparticles’ programme (2004-2008), which developed this field, and as a special advisor to the director of the INSU for ten years, Jean-Pierre realised very early on the major impact that the detection of gravitational waves would have, and strongly and convincingly supported the Virgo project as a member of its steering committee.
More recently, following the first detections of gravitational waves by LIGO/Virgo, Jean-Pierre contributed to our understanding of the formation mechanisms of black hole binaries by calculating the evolution of a tight system of massive stars, involving two episodes of mass transfer between the components.
He also wrote for a wider audience, both in France and in Poland, and has published two books for the general public on his favourite subjects: ‘The Science of Black Holes’ and ‘Gravitational Waves’ (with Nathalie Deruelle).
Over the years, Jean-Pierre has established numerous scientific collaborations with colleagues who have often become friends: to name but a few, Andrew King in England, who was his first collaborator in 1975; Marek Abramowicz and Marek Sikora in Poland; Jean Heyvaerts, Sylvano Bonazzola and Jean-Marie Hameury in the early days after his arrival in France, followed by Kristen Menou and Guillaume Dubus.
When he came to France, Jean-Pierre had a strong influence on our community, through his scientific influence and his involvement in the organisation and administration of research. His sudden death* leaves a great void.
* His last paper, in collaboration with Marek Abramowicz, appeared on ArXiv in October 2024 (https://arxiv.org/abs/2410.06200).
Testimonials
Patrick Peter (director of the Institut d'astrophysique de Paris - CNRS & Sorbonne Université): My first meeting with Jean-Pierre Lasota was when I arrived at the Meudon observatory to do my thesis; he was then the director of the Relativistic Astrophysics and Cosmology Department (DARC), where he welcomed me warmly. For me, he was an example of a respected ‘director’ with unquestionable authority. It's only when you take on this kind of responsibility yourself that you understand the quality of your commitment, especially when you're pursuing research at the highest level.
Jean-Pierre was a key figure and a benchmark, respected both scientifically and as a human being. We will miss him, but I am proud to have been able to take my turn as his director. I hope I was worthy of it.
Bernard Fort (former director of the Institut d'astrophysique de Paris - CNRS & Sorbonne Université): The death of Jean-Pierre, a colleague whom we held in such high esteem, is a personal loss. If I try today to look at him from an inner look, it is the features of an assertive but strangely fraternal image that I see emerging beyond the great scientist. Whenever I went to see him in his office, I always found friendly feelings flooding back, even as he was hammering away at my arguments or mocking my state of mind. I remember the day when, at the height of his enthusiasm, he told me about the wall of fire on the horizon of black holes and the resulting loss of information. It was one of those good moments when we exchanged ideas on the major issues in astrophysics, without ever believing in the definitive truths of scientific theories, or of any doctrine or ideology.
Jean-Pierre and I sought to share a common spirit, and the loss we feel is commensurate with that. We will miss Jean-Pierre, but his memory will live on in all of us.
Nathalie Deruelle (former director of the DARC and the GReCO): The scientific world has lost a great astrophysicist in Jean-Pierre. One of those who see far, and right. One who only collaborates with friends of the same calibre, whose minds are clear and uncompromising. Of those who don't hesitate to kick mediocre people in the teeth. Of those who are not afraid to have strong opinions, who force people to think, even to question established systems of thought or governance.
But he was more than that. His culture was immense. A great lover of music and literature, with as much knowledge of the Nazi and Communist dictatorships as many seasoned historians, an ardent and uncompromising defender of Israel's right to exist, he kept his interlocutors on their toes, and sometimes caught them unawares, particularly during memorable dinners at his home, alongside his wife Agnès Kolakowska, who, with the same depth of insight, was his perfect counterpart.
I was very fortunate to be one of his friends. He will remain, for me and many others, a model of intellectual and moral uprightness.
Jean-Marie Hameury (Director of Research emeritus CNRS at the observatoire astronomique de Strasbourg): I've known Jean-Pierre for over 40 years. As soon as he arrived in France, we worked together, first on gamma-ray bursts, then on compact binaries; this collaboration proved to be long-lasting and very fruitful. I owe him a huge debt of gratitude. He was my mentor when I finished my thesis, while I was still a post-doc. In particular, I remember long discussions in the cafeteria at Meudon, where we could clear up a difficult problem (or talk about other things). I missed them when I went to Strasbourg. He was a remarkable physicist who made a point of relying first on observations to build models that then had to be validated by new observations. After a thesis and initial work in general relativity, he chose to tackle more astrophysical problems; he had the invaluable ability to identify promising subjects to which he could make an effective contribution. His first collaborators (and friends), Andrew King and Marek Abramowicz, followed the same path.
Jean-Pierre knew the world of physicists very well, and was recognised by this community as one of their own. The Observatoire de Paris laboratory he headed for ten years, the DARC, was part of the theoretical physics section. He was one of the key players in the construction of Virgo and, more generally, in the construction of the astroparticles community as a project leader at the CNRS; his experience was invaluable to me when I had to interact with the IN2P3 and the physics department on these issues when I was deputy scientific director of the INSU. His clear vision of the issues at stake and the underlying reasons for the positions taken by the various players were of great help in smoothing out the difficulties inherent in bringing together communities with different, well-established traditions and practices.
Our working relationship very quickly developed into a friendship. Jean-Pierre was a man of strong convictions, but one with whom it was always possible to argue as long as you had good arguments to put forward, and who was willing to accept differences of opinion. On the other hand, he had little sympathy for mediocrity (in any field), and a profound aversion to bad faith.
I will miss him enormously.
Jean Audouze (former director of the Institut d'astrophysique de Paris - CNRS & Sorbonne Université): We met for the first time at Les Houches in July-August 1966, as we were both students at the Ecole de Physique Théorique, which that year was devoted to ‘high energies in astrophysics’. Philippe Véron (1939-2014) and Evry Schatzman (1920-2010) were the directors of this session in which Suzy Collin-Zahn, James Lequeux and Michel Maurette took part, as did the astrophysicist Jim Hartle. We had lectures from Kip Thorne (Nobel Prize in Physics 2017), Al Cameron, one of the fathers of nuclear astrophysics, John Wheeler, a theoretical astrophysicist from Princeton and a former student of Einstein, and Engelbert Schücking, professor of theoretical physics at NYU. We first shared a small chalet, which burnt down because we had used a very dilapidated chimney, and then moved on to other accommodation following the fire, which had the unfortunate consequence of destroying the chalet itself.
Jean-Pierre then returned to the Nicolaus Copernicus Astronomy Centre in Warsaw. We didn't lose touch then, because during the 1970s, we both spent most of our summers at the Cambridge Institute of Astronomy, directed first by Fred Hoyle and then by Martin Rees. In the early 1980s, Jean-Pierre, who had dual Polish and French nationality, decided to come and live in France, first for a brief period at the IAP and then at Meudon at the DARC, where he was director. He returned to the IAP in 1998 as director of research. Three books he has authored or co-authored have been published: 1 - ‘Étoiles et matière interstellaire’ by James Lequeux, Claude Bertout, Jean-Pierre Lasota, Nikos Prantzos and Jean-Paul Zahn in 2009 by Editions Ellipse - 2 - ‘La science des trous noirs’ by Jean-Pierre Lasota by Editions Odile Jacob in 2010 and 3 - ‘Les ondes gravitationnelles’ by Nathalie Deruelle and Jean-Pierre Lasota, also by Editions Odile Jacob in 2018.
Jean-Pierre was one of my first friends in our discipline, and he was both warm-hearted and deadpan. My deepest sympathy goes out to his wife Agnès.
Suzy Zahn (astrophysicist at the observatoire de Paris): Like Jean Audouze, I met Jean-Pierre Lasota during the École des Houches in 1966. He was then recruited to the CNRS in 1983, and came to the Observatoire de Paris-Meudon, where he held the post of Director of the Relativistic Astrophysics and Cosmology Department (DARC) for several years, before moving to the IAP with several researchers from his laboratory.
I was lucky enough to work with him, and it was he who introduced me to accretion disks, on which he gave extremely clear lectures. In particular, we wrote a journal article on discs in galactic nuclei and quasars.
Jean-Pierre was remarkably intelligent and cultured, in science as in art. He was intellectually honest and had no patience for mediocrity, which led to enmities he didn't care for. Discussions with him were sometimes stormy, but always very enriching and thought-provoking.
Guillaume Dubus (Director of Research CNRS at the Institut de Planétologie et d’Astrophysique de Grenoble (IPAG): Jean-Pierre always impressed me with his unique ability to keep abreast of the latest developments in his field. He had an original and deeply thoughtful way of looking at them, with a particular gift for identifying the most controversial aspects, explaining them in a simple way and expressing his opinions clearly. Jean-Pierre never hesitated to take a stand, whatever the audience, with an assurance that sometimes surprised. However, he also had this quality of accepting, without hesitation, when something or someone had convinced him to change his mind. I've always admired his balance between critical thinking and open-mindedness, his ability to set up a debate. I think that Jean-Pierre's contribution to science was even greater than his own, albeit considerable, work. His gift for analysis was wonderfully illustrated by his ability to compare models with observations. In this respect, his influence on me was considerable. Jean-Pierre was much more than a thesis supervisor: our passionate discussions, his incisive and demanding questions on one subject and then another, left a deep mark on me and will leave a huge void. I still remember Jean-Pierre as an active, committed and passionate man until he was suddenly taken ill.
Didier Barret (Director of Research CNRS at Institut de Recherche en Astrophysique et Planétologie (IRAP): Jean-Pierre Lasota played a key role in my early career through his mentoring, friendship and unfailing support. I admired him as a scientist and as a person. He was a true inspiration for me through the way he carried out research, often following his own path, away from the main stream. This made him as one of the productive scientists of the field, leading some very important publications which will survive him for a long time. I will also remember him also as a passionate researcher, always excited about the latest discovery, and sometimes critical about this or this interpretation. Science makes progresses thanks to brilliant and strong personalities like Jean-Pierre, and I was fortunate enough to have him closed to me, while developing my own career. How to not mention this particular phone call he gave me to announce with pride and happiness that the committee he was in, had decided to offer me a permanent position at CNRS: this obviously changed the rest of my life, and without his support this would have never happened. ‘Le petit Toulousain’, as he often called me in the early days, already misses you Jean-Pierre, be sure that I know how much I own you. My condolences to his family, friends and colleagues.
Andrew King (Professor of Astrophysics in the Department of Physics and Astronomy at the University of Leicester): Jean-Pierre was my friend and scientific collaborator for fifty years.
We first met at the Theoretical Physics Institute in Hamburg, where I was a postdoc and he was visiting from Warsaw. We instantly realised we had strongly overlapping scientific interests, and most importantly, a shared sense of humour. We began to work together, initially on problems in General Relativity, and later in astrophysics. What made this special was that our collaborations were always fun - we realised very quickly that we had similar interests in a vast range of things: music, art, literature and more. So the hard work involved was always lightened by constant banter.
I visited him in Warsaw, and my special memory is of us watching my very young son attempt to crawl along the floor of the guesthouse of the Academy of Sciences, and discovering that its mirror-like shine made progress in any direction impossible. On a later visit to me in the UK, where by then I had a permanent position, martial law was announced in Poland. Jean-Pierre instantly told me he would not return under these conditions, and began the progression through temporary positions in various places which eventually led to Meudon and IAP. I was lucky enough to visit him regularly and get to know many of the fine scientists in both places, doing science together, and indulging our shared interests in music and good food and wine. Years of gentle pressure from me gradually got him to reverse his previously entirely negative view of Richard Wagner, and we saw performances at three separate seasons of the Bayreuth Festival, returning each time suffused by the glorious music, but in despair at the distortions of ‘Regieoper’.
Over the decades we were each other's most prolific scientific collaborator, publishing almost fifty refereed papers together. As every scientist knows, the moments where it seems that you are thinking something genuinely new are extremely rare, and usually illusory. A few years ago we had quite unexpected observational confirmation - after more then twenty years - of one such possible moment. As yet it is not disproved. Only a few weeks later, the real Universe obliged us by suddenly offering a spectacular application of what we had guessed. This in turn allowed us to confirm a different and much older idea, to the satisfaction of its author.
As someone once said, science makes progress by trial and error, so it is our job to keep making the errors. For me, nothing will replace what I experienced with Jean-Pierre. I miss him terribly, but count myself supremely fortunate to have known him for fifty years.
David Buckley (Honorary Research Associate, South African Astronomical Observatory (SAAO): I knew Jean-Pierre for over 35 years, from the time I was a postdoc at the University of Cape Town, where he and Agnieszka spent a sabbatical. Our mutual interests at that time in cataclysmic variable stars, particularly magnetic systems, led to many long discussions which gave me new insights about their evolution. But he had a much wider breadth of astronomical knowledge and insights, leading to significant discoveries which impacted significantly on the wider field of accretion in compact binaries. We became firm friends, always enjoying meeting up after years at conferences or when I happened to be visiting Paris when he was there, sometime with my family, which usually led to gastronomical adventures with him and Agnieszka.
He will be sorely missed by so many of us, as a brilliant scientist and collaborator, and as a good friend, who was always supportive and encouraging of his colleagues, including many early career researchers, all who learned so much from him.
Jean-Philippe Uzan (Director of Research CNRS at the Institut d'astrophysique de Paris): Jean-Pierre, our first interaction at DARC in 1996 was a bit rough when I was just starting my thesis. Of course I was young and unsure, and above all it took me some time to understand the full range of your humour. In time, we became friends, office neighbours from the DARC to the IAP. What morning debates, scientific and especially political, where we could conclude that we agreed to disagree. But we had to argue hard, because you never gave up, always without concession. Above all, thank you for the memories of friendly dinners with Agnès, Nathalie, Élisabeth and even my son Yakov, who also sends his thoughts to you from Scandinavia where he is studying. Thank you for all these moments and for your support over the years. Astrophysics, the Institute and above all your friends feel a great void. I feel a great emptiness. Thank you Jean-Pierre.
Marek Abramowicz (Professor Emeritus, Göteborg University): Jean-Pierre had an incredibly original sense of humour. He didn’t take himself too seriously and when he joked about my small misfortunes, he always knew that I would love his mockery. Below is one such example that I recall with great fondness.
I was working at my computer when suddenly I received an email from an unknown person (probably a student) asking me a detailed question about theory of accretion discs around black holes.
The question was important, fundamental and I didn't know the answer. I immediately sent an email to Jean-Pierre, asking whether he knew the answer. His reply, from Paris, came instantaneously: ‘Are you crazy, Marek? You and I solved this problem in our joint paper alongside your assistant Xingming Chen back in 1997!’.
‘Of course!’ I thought and immediately recalled everything in detail, emailing back the following: ‘Thank you, Jean-Pierre, you're right. I forgot.’
To which Jean-Pierre replied: ‘No, you didn't forget. You never read this paper!’.
Alain Omont (former director of the Institut d'astrophysique de Paris - CNRS & Sorbonne Université): The sudden death, in the middle of his work, of Jean-Pierre, a great researcher and friend, was a violent shock for me.
Although he was not part of the IAP when I was its director and we never collaborated directly scientifically, we have interacted constantly for almost thirty-five years, and this has developed into a deep friendship over the years.
I had immense respect for his work and his scientific rigour. He made a major contribution to the renewal of the IAP's theoretical sector with the arrival of his young colleagues from DARC.
I owe him a debt of gratitude when, in the 1990s, we organised a close collaboration with the Copernicus Institute in Warsaw.
A little later, he invited me to join VIRGO's scientific council for a few years, introducing me to what has become a key sector of astrophysics.
My heart sinks when I think of the warm dinners he organised with Agnieszka, sharing a whole circle of friends with us.
Jean-Pierre Lasota at his home on 24 November 2001.Credit: DR
Awards won by Jean-Pierre Lasota-Hirszowicz
Félix Robin Grand Prize from the Société française de Physique (2012) for all his scientific activity.
Rosenblum Memorial Lecture at the Racah Institute of Physics, Hebrew University, Jerusalem (2003).
Member of an International Advisory Committee of the R.F. Kennedy Human Rights Prize (1985-2000).
Works for a wider audience (non-exhaustive)
1980: The Theory of Relativity, co-authored by Andrzej Szymacha, Wydawnictwa Szkolne i Pedagogiczne. Delta Library’ series, ISBN 83-02-00476-6.
1999: Unmasking black holes, Scientific American, 280, n° 5, p. 40
2010: The Science of Black Holes, published by Odile Jacob, Paris, ISBN 978-2-7381-2008-3.
2011: Astronomy at the frontiers of science, Springer, ISBN 978-94-007-1657-5.
2013: The presentation (PDF) of the seminar he gave at the IAP on 8 February 2013: Black holes spin
2017: Was the Big Bang noisy?, co-author: Karolina Głowacka, Warsaw: Prószyński i S-ka, ISBN 978-83-8097-127-1.
2019: Gravitational waves. A new era in astrophysics, co-author: Nathalie Deruelle, Varsovie: Prószyński i S-ka, ISBN 978-83-8169-151-2
2020: Problems with Eureka: what are physicists arguing about? (Kłopoty z Eureką. O co kłócą się fizycy?), co-author: Karolina Głowacka, Cracovie: Copernicus Center Press, ISBN 978-83-7886-493-6.
2022: The road to black holes (Droga do czarnych dziur), Copernicus Center Press, ISBN 978-83-7886629-9.
Video of a lecture by Jean-Pierre Lasota-Hirszowicz on black holes (filmed in 2005 by CERIMES as part of a series of public lectures to mark the centenary of relativity):
https://www.canal-u.tv/chaines/cerimes/les-trous-noirs
Video of a lecture by Jean-Pierre Lasota-Hirszowicz on black holes (filmed by CERIMES in 2009):
http://www.canal-u.tv/video/cerimes/les_trous_noirs_01_12_2009.9533
Video presentation of his book ‘The Science of Black Holes’ published by Odile Jacob in 2010: http://www.youtube.com/watch?v=Iyr1ohC1TxI
Layout: Jean Mouette
November 2024