siaa_logo_blue Catherine Cesarsky cesarsky_circle

Commissariat à l'Energie Atomique

Gif-sur-Yvette, France

Job Title: Haut Commissaire à l'Energie Atomique


She is an Astronomer: What stage in your career have you reached?

Catherine Cesarsky: I am currently High Commissioner for Atomic Energy in France, which is a governmental position.


SIAA: How many years ago did you complete your PhD?

CC: 38 years.


SIAA: What is the most senior position that you have held?

CC: I was the President of the International Astronomical Union from 2006-2009 and Director General of the European Southern Observatory (ESO) from 1999-2007.


SIAA: Do you feel it was more difficult for you to get a job or a promotion in comparison with male astronomers?

CC: No


SIAA: Are women under-represented in your institution?

CC: My current job is non-astronomy.  In my last astronomy job as DG of ESO, about 20% of the staff were women.


SIAA: What is the biggest challenge you have faced as an astronomer?

CC: Juggling career and family.


SIAA: What is your family status?

CC: Married with two children.


SIAA: Have you had any career breaks?

CC: No.


SIAA: What has brought you to astronomy and what fascinates you most in your job?

CC: I studied physics, moved to astronomy as and undergraduate final project, loved it and stayed. What fascinates me most is the excitement of research and discovery.


SIAA: What recommendation would you make to young women starting their career in astronomy?

CC: To go ahead.


The following interview is taken from 12 scientists of the 21st century, Tinta publishing house, Budapest.



by László Szabados



Born in France, Catherine Cesarsky received a degree in Physical Sciences at the University of Buenos Aires and graduated with a PhD in Astronomy in 1971 from Harvard University (Cambridge, Mass., USA). She worked at the California Institute of Technology. In 1974, she moved to France, where she joined the staff of the Service d'Astrophysique (SAp), Direction des Sciences de la Matière (DSM), Commissariat à l'Energie Atomique (CEA). She then established her career in France. From 1985 to 1993, she was the Head of SAp. Later, as Director of DSM (1994-1999), she led a team of about 3,000 scientists, engineers and technicians working in a broad spectrum of basic research programmes in physics, chemistry, astrophysics and earth sciences. From 1999 to 2007, she was Director General of the European Southern Observatory. She is now the High Commissioner for Atomic Energy in France.


Dr. Cesarsky is known for her successful research activities in several areas of modern astrophysics. She was the Principal Investigator of the ISOCAM camera onboard the Infrared Space Observatory (ISO) of the European Space Agency (ESA), which flew between 1995 and 1998. As such, she has led the ISOCAM central programme.

She received the 1998 COSPAR Space Science Award, and is a Member or Foreign Member of various Academies (French Académie des Sciences, Academia Europaea, International Academy of Astronautics, National Academy of Sciences USA, Royal Swedish Academy of Sciences, Royal Society of London). Between 2006 and 2009, she was President of the International Astronomical Union (IAU).


What major experiences and important people have had a determining influence on your professional career?

I studied physics at the University of Buenos Aires. Although I am French, my parents and family were living in Argentina. In this university I could only study physics; there were no courses in astronomy. Then, in my fourth year, a new professor arrived: the astrophysicist Carlos Varsavsky. He was from Argentina, had got his PhD at Harvard and had worked in Cambridge, England. He came back to Argentina with the components of a radio telescope, donated by the Carnegie Foundation, to be set up in Argentina. He wanted to start forming a group. I decided to join this group and work with him. First of all I had to write a little thesis on the topic of the measurement of the age of stars. I intended to deal with theoretical studies but he, of course, needed help to build the radio telescope. Later on I graduated and agreed to work with him, taking part in the construction of the radio telescope. In return, he agreed to help me get a PhD scholarship in the United States because until that time there had been no PhD program in astronomy in Argentina: it was established just as I left. So I helped in the construction of the radio telescope, and took some astronomy courses at the same time at the University of La Plata. Professor Varsavsky invited several prominent astronomers from all over the world to Argentina, to teach courses for us. One of them was a Harvard professor, and that was my first contact with Harvard.

In the meantime I got married to an astrophysicist, Diego Cesarsky. We both applied to the graduate school in Harvard, and we both won scholarships, so we were able to go to Harvard. So, if this man, Carlos Varsavsky, had not returned to Argentina just at that time but- say- only two years later, I would not be an astrophysicist because there were no such opportunities in Buenos Aires. I will be eternally grateful to him because he steered me in this direction, and I have always enjoyed my work so much.


What other profession could you have pursued instead of becoming an astronomer?

I would certainly have been a physicist. I would simply have been involved in some other branch, probably particle physics. Now I think that for my generation it is much more interesting to have been an astrophysicist. It is one of the scientific disciplines where the most interesting things have happened, for people of my generation.

Getting back to influential persons in my career, I can also name Professor Russell Kulsrud. When I was at Harvard, he was my thesis advisor. He was a plasma physicist working in Princeton. At that time I was trying to understand solar flares and related phenomena, the acceleration of particles, and so on. I went to a meeting on plasma astrophysics, in California, to talk about my work. At this meeting I realized how deeply ignorant I was in this field, in which there was no real specialist at Harvard College Observatory. I took a summer job in Princeton, in order to deal with the topic advertised by Russell Kulsrud. I started working under his supervision, and chose him as my thesis advisor, and I wrote a thesis on the propagation of cosmic rays in the galaxy. Even though I could spend little time with Russell, and of course we did not have Internet at the time, we had telephone conversations and now and then we exchanged hand-written letters. Nevertheless, he was enormously helpful with all the basics I needed to carry out this research. I admired his seriousness. He was not a flashy person; he was a deep thinker and he was also very knowledgeable. I am happy to say that he is still very active at an age of about 80. Carlos Varsavsky, regrettably, died very early, at the age of 50.

In addition to these two mentors, I want to mention a third one: Professor Peter Goldreich. When I finished my thesis, I was lucky enough to obtain a postdoctoral fellowship at the California Institute of Technology to work with Goldreich. I spent almost three years there, and, strangely enough, we never did any research together. In the end, we never co-authored a single paper. He was trying to change topic, and so was I, and during those three years we met often and discussed almost everything that there is to discuss in the field of astrophysics. Of course, to have the good fortune to have such a mind at my disposal was fantastic because he is really a great scientist. He completely opened my eyes to astrophysics, and after I left California, I remained interested in all fields of that science, especially in their theoretical aspects, and I devoted the first part of my career to this kind of study.

These are the three professors who had a definite influence on my research career.


What are you, above all, proud of in your professional achievements?

In the first part of my career, say in the 1970s, my research topics were theoretical studies in high-energy astrophysics and the interstellar medium. I achieved substantial recognition at an early age thanks to my work in this field, and some of my papers from this period are still frequently cited. Then I became interested in instrumentation and observation as well.

In 1980s I became Principal Investigator of an infrared camera, ISOCAM, which flew on board of the ISO satellite from 1995 to 1998. The ISO (Infrared Space Observatory) was a highly successful mission of the European Space Agency. The proposal for ISOCAM was, in fact, accepted in 1984- because it takes a long time to construct such an instrument. In the meantime I also became the head of the Department of Astrophysics at Saclay, where I was working, and this position made it easier for me to obtain all the support I needed in order to build ISOCAM properly. It was an international collaboration in which Saclay was playing a big part, and of course we were running the show.

Instead of doing theoretical work with two or three people, mostly alone in a corner, with ISO I found myself running all over Europe and coordinating the work of hundreds of people from all over the world. And then dealing with industry: we had big industrial contracts. The most exciting event in my career was when the ISO satellite was launched. The telescope on board had a cover, and after some time the cover was blown off and the first image came through: it was an image of the “Whirlpool” galaxy, M51. We could immediately see on the computer receiving the data the first ever image of this spectacular galaxy at the wavelength of 15 micrometers, a spectral region which cannot be observed from the Earth. Previous satellites did not have sufficiently high angular resolution to achieve this. It was a very high point in my life - in November, 1995.

In 1994 I became Director of “Sciences of Matter”, responsible for all basic research in Physics and Chemistry at the Commissariat à l'Energie Atomique. So until 1999 I was director of a very large group of about 3,000 people, and that provided some interesting management experience. Earlier I had to manage no more than 150 people, and suddenly there were several thousand of them. Moreover, I had to talk to Ministers and civil servants, to convince the government to provide the funds required to carry out our projects..


eso1How could you deal with your own research topics during this period, burdened as you were with managerial and administrative tasks?

In these years ISO was active and I simultaneously ran basic research at CEA and took part in ISO-related scientific work. This was extremely interesting because of the novelty of the findings, especially those on the distant galaxies. Infrared bright galaxies were much more common earlier in the life of the Universe than they are now. We could look back billions of years in time, reaching about half of the present age of the Universe, and we found that these galaxies were making lots of stars: the rate of star formation was about 70 times higher than the current rate. I took part in many ISO projects but I was most deeply involved in this particular one, on which I continued working for a long time.

In 1999 I became Director General of the European Southern Observatory (ESO). This is an intergovernmental research organization for astronomy with 14 member countries from Europe. ESO operates some of the largest telescopes in the world and other state-of-the-art facilities, and provides European astronomers with access to the southern sky. It was a fantastic time because it was just when the leading telescopes of the world, the system of four eight-meter telescopes which make up the Very Large Telescope, were being put into operation. For instance, I was present at the “first light” of the third (Melipal) and fourth (Yepun) 8-meter telescopes, and at the inauguration of many scientific instruments attached to these and other ESO telescopes in Chile. I was also responsible for the European part of the Atacama Large Millimetre Array (ALMA), a facility which is now being built in a world-wide cooperation (with 18 sponsoring countries) in the Atacama Desert in Chile. Strangely enough, the signing of the agreement on the construction of ALMA between ESO and the National Science Foundation in the USA took place on February 24, 2003, just on my 60th birthday. And since then, every step of building this array has been fascinating. ALMA will offer enormous advances in astronomical knowledge. As you can see, I lived through many interesting, even unique experiences, while serving as Director General of ESO.

More recently, as President of the International Astronomical Union (IAU) I have launched the International Year of Astronomy, and I am very excited about this, too.

Now, as High Commissioner for Atomic Energy in France, I am learning a new trade, involved in politics in a broader sense.


To be the President of the IAU is the highest rank in the astronomers’ community. Did it leave you time to deal with research?

This depends completely on the actual tasks. In the first year IAU affairs took up about 5 per cent of my time, in the second year they took up much more because the preparations for the International Year of Astronomy were so time consuming. Now, in the past 3 months, a very high percentage of my time has been devoted to my duties as President of the IAU and as chair of the Working Group coordinating IYA2009 at international level. My time as IAU President comes to an end in August 2009, but I will run the Working Group until the end, in mid-2010.


What would you still like to achieve in your professional career?

As a researcher, I am still working on galactic evolution, which in a way is a continuation of the studies I had started with ISO. It has now become a whole industry. There are lots of astronomers working in this field and using surveys. So large surveys have been, and are still being, conducted, some with the participation of ESO, such as GOODS (Great Observatories Origins Deep Survey). I am very interested in these problems of galactic evolution and the formation of black holes in the centre of galaxies, and so forth. I would also like to turn my attention once again to cosmic rays with the Fermi, HESS and Auger results coming out. The Auger Observatory is studying ultra-high energy cosmic rays, the rarest and most energy-rich particles in the universe. I keep abreast of the latest developments and findings, and though I have not come up with any new idea that would revolutionize the field it’s always worth keeping oneself informed.

And as I said I am also entering into a new world with my present position.


What are the most outstanding results of the last decade in the field of astronomy, and how might they influence the course of the 21st century?

lagos 1204As far as the last ten to fifteen years are concerned, I think most astronomers would probably give the same answer because it is pretty obvious: the discovery of planets orbiting stars other than the sun. It started in 1995, when Michel Mayor and Didier Queloz demonstrated that there was a planet in orbit around a nearby star. Now we know of more than 330 planets orbiting other stars, and the number of such extrasolar planets is increasing, in fact, very rapidly indeed. Even a few years ago it seemed that with the instruments that we have on the surface of the Earth, it was only possible to detect the presence of extrasolar planets at least as large as Jupiter and Saturn, but a few years ago somewhat smaller planets, the size of Neptune, could be also detected, and now, in fact, everybody is surprised: astronomers are even detecting planets with 2 to 10 times the mass of our own planet, the Earth. These are referred to as super-Earths.

To see even smaller exoplanets, to get down to the critical mass limit of our Earth, we really need new equipment. There is, at the moment, the space mission CoRoT (the abbreviation comes from Convection, Rotation, and planetary Transit) which can, by a different method, observing photometric transits, and perhaps detect planets like the Earth. And another mission, called Kepler, has just been launched which will do similar observations more efficiently. Unlike CoRoT, which is a mostly French mission in partnership with ESA and other European countries, Kepler is a NASA mission.

In the future, to observe and possibly characterize planets, we will have extremely large telescopes like the 42 meter ELT reflector for which I launched the preliminary studies at ESO and, probably later, space missions, maybe using interferometry, that will be able to work in the thermal infrared part of the electromagnetic spectrum, which is ideal for this type of study.

There is another recent great achievement, and there is probably a consensus among astronomers in this regard, too: the discovery of the accelerating expansion of the Universe. Astronomers used to think that the expansion of the universe would progressively slow down. However, in 1998, two groups using supernovae, which are reliable cosmic distance indicators, so called standard candles, discovered independently that the expansion is accelerating. Why is that? There is no answer yet. Is there an additional field or force, opposing gravity, which fuels the expansion? For now, we hide our ignorance behind the expression `dark energy’. I think that to understand the nature of dark energy is even more difficult than to understand dark matter, whose existence has been known for a long time. It is one of the most important questions to be answered by the astronomers of today. Chances are it will bring a revolution in fundamental physics. Whether it leads to changes in theories of gravitation, beyond Einstein, or whether it requires the introduction of new fields, or more dimensions as in string theory, or whether it rests on completely new ideas that have not yet surfaced, it is going to be fantastic. I cannot predict when we will understand, whether it is a matter of years or decades. The situation is simpler in the field of extrasolar planets where there is continuous progress. Dark energy may remain a mystery for a long time.

These two outstanding results also exemplify the major differences in “doing science” in the 20th and in the 21st century.


What is your opinion about the social responses to, and impact of, these breakthrough-type questions?

We are in the International Year of Astronomy, celebrating the 400th anniversary of Galileo’s first observations. He first looked at the sky through a telescope he built in 1609. Among other discoveries, Galileo found the four large satellites of Jupiter, and he made the link with the Solar system, and understood that Copernicus was right: Jupiter and its moons form a miniature version of the Solar System, and clarify the fact the Earth and the other planets revolve around the sun. These early telescopic observations completely changed our view of the Universe, because at that time most of humanity still believed in Aristotelian ideas of the cosmos: the Earth was something exceptional and everything else, Sun, planets, stars on a sphere, was perfectly arranged, and revolved around the Earth as Ptolemy described it.

In the same way, astronomers are now making discoveries that can change our whole vision of where we are, where we came from, what our history is. I believe that these are important questions for every human being living on the Earth. And we wish to make people in the world aware of what we are discovering about our common universe, and get them to experience for themselves how fantastic it is to look at the sky, to enjoy its beauty and to reflect on its meaning and on the way it works.

Indeed, another good aspect of astronomy is that all of mankind shares the same sky. This simple fact is a unifying factor for humanity, so it fosters peace. Peace is, of course, essential. In a way, astronomers are already united all around the world: we see this every day at the International Astronomical Union.

Another characteristic aspect of astronomy is that its advances are directly linked to those of high technology. We are always pushing industry to its limits, and in this we encourage all kinds of developments, many of which find other uses in society. There are plenty of examples, including adaptive optics, which helps us to correct astronomical images distorted by turbulence in the atmosphere, and is now also very helpful for the most intricate eye operations. Electronic light detectors that have been developed for astronomical purposes are now being widely used, as are the image processing methods that we have established. Here again, I believe that it is to medicine that our astronomical techniques are most beneficial.

The recent advances in gathering, storing, retrieving, and analyzing huge amounts of data obtained by ground-based and space observatories and other astronomical facilities give rise to large data repositories, denominated `virtual observatories’. The methods used in these facilities can be applied to many other fields where there are large volumes of data which need to be accessed and evaluated in a timely manner; an obvious example are the data from Earth monitoring for climate studies. Astronomy is always at the forefront of technical development, and the new astronomical techniques can find their applications for advancing other fields.


What measures, initiatives and actions do you suggest should be taken to enrich and reinforce the relationship between science and society?

Of course, I would like to see a stronger relationship between science and society, and this is where I think astronomers can help because astronomy is the scientific discipline that is most attractive to the public at large, and thus it can be used to bridge the gap between public understanding of science and the new scientific developments. This is indeed our aim with the International Year of Astronomy: to make people grasp the foundations of scientific method through astronomy, and then they may perhaps also understand other disciplines. Science is needed for the progress of humanity, and science can and will help to solve our enormous problems which are, of course, the lack of peace on the one hand, and, on the other hand, poverty, hunger, and intolerance.


What are the most challenging problems facing the world, generally speaking, and in science at large?

The most challenging problem for the world is the threat of war. In various places on the globe, war could break out at any moment. The eradication of extreme poverty, the lack of opportunities for education in various areas, are other serious problems that need solving. Of course, climate change and environmental pollution are also among the most important problems facing humanity. But the threat to peace is by far the gravest, and it is related to intolerance.


What role can science play in meeting or, at least reducing, these challenges and threats?

Basic sciences are, in every case, the real motor of technological advance. In addition, they are universal. They have no borders, as you can see with astronomy, especially now, in the age of the Internet. And so they unite mankind, and from this point of view, they promote peace. Scientists can show the world that citizens of all nations can have purposeful, lively exchanges on a continuing basis. For example, in my profession, in a way we all speak the same language and have similar experiences: we are living every day in our astronomy bubble, and often I feel that I have more in common with an astronomer from the opposite end of the world than with my next-door neighbour. This is also the case among scientists in other fields.

Of course, most important are the technological advances resulting from novel uses of scientific discoveries. Owing to them, science can be of enormous assistance in alleviating poverty, eradicating hunger, and improving health and well-being - provided that the political will is there... Other applications of science include monitoring the environment, predicting climate change, and helping to mitigate its effects.

A final point I want to make about science in general and astronomy in particular is that they have the capacity to direct people’s thoughts towards interesting subjects, where they can exercise their minds and emotions, and which take them away from their everyday material worries- of course the arts play a similar role in this respect. As I have said on many occasions, during the International Year of Astronomy we would like everybody on Earth to think, at least once, about the wonders of the sky, to share the human wish to reach out to the stars and to comprehend them, to feel part of the universe. The aim is to enhance people’s lives.


If you had a chance to formulate one of the main messages of the 2009 World Science Forum, what would it be?

It is a unique opportunity for scientific exchange at the international level, to consider how science contributes vitally to sustainable development, and how it can be used to promote peace. Political aspects can be discussed as well, and, in general the role of science and scientists in society.


The whole world is governed by men, and the situation is no better in science. There are only two women among the scientists interviewed in this book, and this simple fact is a clear message that there is much to do to reach a proper level of emancipation in research. Do you feel that there is any significant or characteristic difference between the sexes that makes scientists of one or the other gender more likely to become `good researchers’?

Women are just as well-qualified as men; they have every capacity to do science. But they have, first of all, been made to feel very early on that this is not the case. They have been discouraged, sometimes, from childhood on. In my opinion, this is a kind of hidden discrimination. Also, there is a point in every career, especially in scientific research, where it seems that total dedication is required, at least for some time. Traditionally women, especially if they have children, have been less prepared to accept this kind of immersion in work than men. But this is changing too; now, young researchers of both sexes struggle, often successfully, to find a balance between work and family.

I myself have two children. I am not the type of woman who could have decided that since I wanted to deal with science, I could not have children; for me, having children was an absolute must. Many, many women of my generation have had good careers in science and also raised families, and this is even truer among the younger generations.


My impression is that the situation is somewhat better in astronomy than in other scientific disciplines in this respect. Do you agree with this opinion?

Yes, it is better but not yet good enough, in the sense that we have in astronomy, the same as in other disciplines, what is called a `leaky pipeline’. This means that the proportion of women is always much higher at lower levels. There is a high proportion of women among the graduate students, then you will find fewer among the postdocs, and so on. At the level of full professors, there are very few women indeed. This kind of leaky pipeline exists in astronomy, too, and we have to understand why, and try to change this unfortunate situation.


But you are a counter-example!

13may2005_paranal_0028Yes, I know that I am an exception who has had a very successful career in spite of being a woman; especially from the point of view - if I may say so - of exercising decision-making power. Really, I have wielded a lot of power -maybe Icontinue to do so in my present position -but I do not know why. It is not because I decided when I was young that this was what I wanted to do, it just happened. It is difficult for me to understand why; perhaps it is simply because people perceive that I am ready to take on responsibilities, when it becomes necessary. But I never felt different from other women, or even other researchers. I always felt and still feel completely at ease in groups in which I am very often the only woman, but I am happier if there are other women, and I feel a strong bond with other women scientists. So it has not been a problem for me to be a woman in a man’s world, or for my career. When I was young, it was more of a problem, because young women were, especially in my time, not so well accepted. People did not expect much, I would say, of young women.

Fortunately, as time went by, people started to take me seriously.


Let me confirm that the whole community of astronomers are proud to have a woman holding the highest post in the International Astronomical Union, and we are perfectly satisfied with the work that you have done in that post.

Thank you for sharing your thoughts with the readers of the book. I wish you further successes in research and in your present and future positions `in power’.