Remembering Lodewijk Woltjer

ESO staff pay tribute to former Director General

8 November 2019
What you’ll discover in this blog post:
  • What made Lo Woltjer remarkable as ESO Director General
  • Why Lo Woltjer is highly respected within the astronomical community
  • How Lo Woltjer changed the ESO paradigm and played a key role in the expansion of European ground-based astronomy on the global stage
In this edition of the ESOblog we present tributes to Lodewijk Woltjer, who served as Director General of ESO from 1975 to 1987. As the third and longest-serving Director General, Lodewijk (who was often called Lo) started a new age within ESO, marked by the formation of a science group — an international group of scientists that has thrived and expanded over the decades, pushing for advancements in telescopic and optical technology. Lodewijk sadly died on 25 August 2019 at the age of 89, but his strong personality, interest in humanity and clear vision for ground-based astronomy has left a profound impression on those who knew him and a legacy that subsequent generations of astronomers continue to benefit from.

A lasting impression

He said little but listened carefully

An inspiring gentleman scientist

Lo Woltjer — the human side

Changing the ESO paradigm

A skilled negotiator

Elegant, sharp & quick

Lasting legacy to ground-based European astronomy


A lasting impression

Dietrich Baade
Former Deputy Director for Science
ESO Fellow (1981–1984)

Of all the ESO Directors General (DGs) I served under between 1981 and 2016, Lodewijk Woltjer and Riccardo Giacconi left the most lasting impression. When I joined ESO as a postdoctoral fellow, I imagined a DG to be a very imposing person. However, Lodewijk Woltjer turned out to be a very modest man, perhaps even shy in a way. He avoided the main entrance to the ESO headquarters in Garching and, when he did use it, always jumped up the stairs climbing two at a time. His parking space was not marked but every single one of the approximately 75 staff in Garching knew which one it was. It was close to the side entrance that he preferred, from where he rushed through the narrow internal staircase to his office. He resisted any temptation to ask ESO to order him a prestigious company car, preferring a Citroen DS 19 or 21.

Postdocs had two annual interviews with Lodewijk Woltjer; during my first, I realised that he was better prepared than me, and knew an amazing level of detail about my work and my work contacts. His memory was outstanding also on other occasions. For instance, we once passed each other in the short corridor between the cafeteria and his office. Suddenly, he turned around and asked: “Why does 28 ω Canis Majoris appear twice in your target list?” Not only had he noticed the mistake in my observing proposal, but he had even memorised the full designation of the star I wanted to observe! In this way, I found out that it was not just pro forma that all scientific staff in Garching were expected to provide him with a copy of all submitted observing proposals.

This should have served as a warning to me. The said observing proposal was accepted and the observations scheduled in January when Lodewijk Woltjer usually spent several weeks at the La Silla Observatory. For the observations I used the 1.4-metre Coudé Auxiliary Telescope. At that time, the control system of the tertiary mirror at the beginning of the coudé train had a problem and had to be re-initialised up to seven or eight times every night, causing significant time losses. Eventually, I was so frustrated that I wrote in one of my night reports: “Finally I understand why the VLT design foresees four unit telescopes, namely to make sure that at least one of them is working at any one time.” By chance, I was up early enough during the day to find a note in my mailbox that I had an interview with the DG at noon. I took that timing as implicit criticism, because even after a short summer night, 12:00 was fairly early for an observer. The interview however was very pleasant and mostly about technical matters. As a result, I also learned that the DG himself was reading night reports no less carefully (and critically) than the maintenance staff.

As the founder of the Science Group and ESO’s Fellowship Programme, Lodewijk Woltjer paid close attention to furthering careers, especially of young people. When he appointed observing-technique-specific working groups that aimed to establish the scientific requirements for the VLT and its instrumentation, he included at least one Fellow in each among the half dozen other members. This provided a unique learning experience.

The ESO Council had extended Lodewijk Woltjer’s appointment for a third five-year term. But he resigned after (a still unparalleled) 12 years when the VLT project had been approved by Council so that the DG who would be responsible for designing and delivering the VLT would not be hindered by decisions made by a predecessor. After the resignation, many people were surprised to hear that Lo started to talk to them in their respective mother tongue. Until then, he had used English throughout, and avoided his native Dutch, so that there would be no false impression of any undue closeness.

As President of the International Astronomical Union (IAU) from 1994 to 1997, Lodewijk Woltjer also presided the General Assembly in Kyoto in 1997. Resolution after resolution was read by him, on reference frames, nutation theory, Julian Date notations, etc. While important matters, some participants found them boring, when one participant finally stood up to ask whether the members had to bear all this waste of time, a murmur of support rippled through the huge room. Lodewijk Woltjer explained in quiet but unmistakable words that these resolutions were part of the raison d’être of IAU General Assemblies. It was one man against nearly 2000, and the battle was settled before it had begun.


He said little but listened carefully
John Danziger
Senior Astronomer, ESO (19731995)

I first met Lo at Columbia University in 1971–72 when I was a visiting speaker. As a guest at dinner with Lo I became immediately conscious of a person with a wry sense of humour who did not particularly enjoy small talk. When Lo arrived at ESO in 1974 I had already been at ESO Chile since September 1973. Realising that I did not much like living in Chile with their new military government he invited me to come to ESO HQ at CERN in Geneva. It was at this point that Lo had some opposition within ESO countries to having a scientific group stationed in Europe. He eventually overcame that opposition by demonstrating to good effect that having only one group would be detrimental to instrument development only possible in Europe and overseen (but not necessarily controlled) by astronomers. This decision was enhanced by his appointment of educated optical engineers from mainly France and the Netherlands. This has resulted in ESO being at the forefront of instrumental development and the envy of other observatories.

It has been noted and possibly forgotten with time that Lo, for his own benefit and that of his staff, had little tolerance of unproductive bureaucracy and by example minimised it as much as possible. This is an important aspect of a well-run scientific institution.

Lo kept up his scientific interests during his tenure by writing scientific papers. He gave his blessing to an invited speakers programme and regularly attended those talks as well as talks given by his own staff, usually resulting in just one incisive question by Lo. He was always willing to give the benefits of his scientific knowledge to younger members of the ESO staff without imposing himself on them. When he was at La Silla he made a habit of visiting all the larger telescopes every night, and sometimes the smaller ones, just to see how things were going. One night he arrived at the ESO 3.6-metre telescope near midnight to find it abandoned by the scheduled observer in order to have a cooked dinner at the observatory dining room. He was appalled and this led to the introduction of meals being brought to the domes heated in enclosed boxes. I no longer remember whether this necessitated new rules or whether it was quickly understood what was expected.

He was at La Silla when SN1987A exploded and he spent quite a lot of time the first night looking over our shoulders at the ESO 3.6-metre waiting to see the spectra as they came in. Some of those present may not have understood why Lo showed such a keen interest in, and knowledge of, supernovae but it is worth recalling that Lo’s doctoral thesis at Leiden University addressed the structure of the Crab Nebula and the nature of its polarised filaments. In that first week there were meetings in the late afternoon of all scientists involved in observing SN1987A in order to compare notes, review results and reveal plans. Lo was always present, not talking but listening.

I was a witness over many years to Lo’s presence at every Observing Programmes Committee meeting, as the number of proposals for observing time increased rapidly. He said little but listened carefully. If there were two referees who might strongly disagree about the worthwhileness of a programme and refused to change their positions, I noticed that Lo took notes, and more often than not, they got observing time.

Later, when international meetings were called concerning SN1987A, he very much wanted to see and encouraged the presence of ESO at such affairs. In fact, ESO orchestrated the first international scientific meeting on SN1987A in July 1987 which was strongly endorsed by Lo. Succeeding European astronomers have much to be grateful for in Lo Woltjer. And not only European astronomers, but also non-Europeans who have obtained time with worthwhile programmes.


An inspiring gentleman scientist
Peter Shaver
Senior Astronomer, ESO (19782006)
Former President of the IAU’s Division X on Galaxies and the Universe

Lo was one of the last of the grand generation of dignified and inspiring gentlemen scientists. Always in jacket and tie, he gave elegant talks without notes or viewgraphs, every word considered and significant. He was highly respected and knew the astronomical community well, so he was the ideal person to lead ESO through its formative period. During the busy years after he established the science group, we were all very impressed that he still took the time to visit students, fellows and staff, asking piercing questions and making helpful comments. I feel very fortunate to have been involved in many of his initiatives over the years ⁠— the Swedish-ESO Submillimetre Telescope (SEST) project (which led to the European participation in ALMA), studies for the VLT, the European Astronomical Society, and the restructured IAU. In later years I knew Lo and his wife Ulla as wonderful personal friends. They will be very well remembered.


Lo Woltjer — the human side

Daniel Hofstadt
Former Head of the Technical Research Support Department, ESO
Former ESO representative in Chile

For thirteen years I was to report to a man I called a “General” Director.

He was enigmatic, with a sceptical view of men and the world. Yet he was tremendously strong minded and determined to promote ESO into becoming a world class Institution. His ways were not aligned with traditional managerial or even diplomatic behaviour.

When he left ESO we agreed to meet once a year in the south of France. My wife Sonia and I visited him and Ulla in Saint Michel. In March 1999 they came for the VLT inauguration and Ulla wished to visit us in the Chilean Lake District. Lo had said “Oh, pourquoi pas?”, lifting a hand with his casual gesture.

He arrived at Lake Rupanco, dressed in white, town shoes and an elegant jacket, instantaneously fascinated by the beauty of the place. Soon he sensed the wild of the forest, the moods of the lake, the staging`s of the mountain clouds. Permanently looking out for the slightest sign of a change in the sky. He would remain on our house terrace till the last sunray, scrutinising the other side of the lake. I told him about trees, birds, fish and people. He agreed to believe half of my stories. Early morning, while everyone else was still asleep, we reshaped the world together. He never engaged in any argument. At most he would lift his hand to say, “Oh, possibly!”. To get the early morning spirit rolling I would sometimes cite nasty extracts from the sarcastic Schopenhauer. We agreed how stupid the business of the world was but carefully omitted our own weaknesses. I never saw Lo admitting anything beyond his willingness. I guess he would have said the same of me.

It was amazing to watch such a man relate to the spirit of our wonderful paradise. He even considered buying land. It had to be on the other side of the lake where hardly anybody lived, an open spot glowing in the evening sun. It could only be reached by boat. Not necessarily a very convenient access choice when the lake was in a bad mood. Our house is at the end of the world but Lo wanted a place beyond the end of the world. He sometimes walked off without telling us. Ulla was worried the day he decided to join me and a friend in a fishing trip at our mountain lagoon, a three-hour climb on a forest trail. Lo went in white trousers and town jacket. We enquired about his tie. When we arrived at the lagoon, he was very tired. After a sandwich and beer, we went fishing while he decided to walk slowly back on his own. He left some clumsy signs of broken branches on the trail. Once we came back at the lakeshore there was no sign of him. There happened to be a local horse race event that afternoon where the people could help us to organise a search party. We got the horses, but all the horsemen had been disabled by a combination of joy and beer. As we went back on the trail, somebody came rushing after us and said that a man in white trousers and grey hair was sitting in a lonely place meditating in front of the lake.

Any adventure intrigued Lo, raising his curiosity and often made him laugh. He was fascinated by the water and would go swimming even when he had difficulties walking. He was also willing to drink some local brew to help his cough although he did not believe in it and agreed that wine was a better option. He loved our dogs and played with our grandchildren. At Rupanco Lo was fully integrated. Astonishing for a man who lived his whole life with a suitcase in his hand. He quickly developed his own views of this new world and acknowledged the purpose of it all. Part of his book with Roger Bonnet “Surviving 1000 centuries. Can we do it? “ was written at Lake Rupanco.

He and Ulla came back every summer to this captivating spot on Planet Earth, eventually reinforcing my own beliefs of a sense purpose in nature. He acknowledged that life makes sense at our lake, once again casually lifting his hand “Oh, I guess so”

Last summer Lo and Ulla could not visit us. Lo’s straw hat is still hanging at our entrance door.

Lo and Ulla at the Hofstadts’ summer home in the Chilean Lake District.
Credit: ESO/Bob Williams


Changing the ESO paradigm
Catherine Cesarsky
ESO Director General (19992007)
Chair of the Square Kilometre Array Board of Directors

I am very sad to hear of the departure of Lo Woltjer, a few months after his wife Ulla. Over the years, we had many opportunities to meet and exchange both inside and outside the astronomy world, and my husband Diego and I had developed a friendly relationship with them. Most of our encounters were unplanned, we just attended similar meetings and events. Diego and I became accustomed to running into them at parties or at friends’ houses, and shared drinks or meals in various parts of the world. I just can’t get used to the idea that we will not meet them again.

I have always had great respect and admiration for Lo. In the 70s and early 80s, we worked in the same branch of astronomy, high energy astrophysics, and I was familiar with his papers. Before I even met him, I knew by heart his article on supernova remnants in the Annual Review of Astronomy and Astrophysics. All his life he kept a keen interest in high energy astrophysics, neutron stars and pulsars, supernova remnants and plerions, active galactic nuclei and radio galaxies, and the gamma ray background. He had a long-term, fruitful collaboration with Giancarlo Setti. Later, in his years in Haute Provence, he collaborated with Myra Veron-Cetty on quasars. For many years he was close to Franco Pacini, even if they did not publish much together, and frequently spent time in the Arcetri Observatory. I saw them: Lo, Franco and partly also Giancarlo, as tutelary figures of European astronomy, especially in the realm of high energy astrophysics research.

But Lo was also ESO Director General, and I witnessed how he changed the ESO paradigm, with his quest for a 16-metre telescope for ESO. For many years, at all the astronomy meetings in Europe, the subject was brought up and different designs were debated. Lo gave visionary talks about the scientific capabilities of a 16-metre telescope, which he considered superior to the Hubble Space Telescope. In the end, Lo was masterful in achieving definition of the 16-metre telescope: four 8-metre telescopes with active optics and an interferometric capacity; as well as in obtaining the green light from the ESO Council in December 1987.

When he was ESO DG, Lo often invited me to spend time at ESO. It was difficult for me for family reasons, but in the end in November 1981 my whole family spent one full month in Garching. I vividly remember going to see him in his office for the first time. I felt extremely awkward; I realised only much later that he could be so intimidating only because he was himself shy. He received me very nicely in the office that, many years later, I was to occupy for eight years, and which at the time seemed luxurious beyond measure to me. Over the course of the month our contact became much more fluid.

After leaving ESO, Lo became very interested in space-based infrared astronomy, and ESA gave him an important role in the selection of the International Space Observatory (ISO) observations. This led us to frequent interactions and exchanges. Having personally invested several years in the development of the ISO mission and especially of ISOCAM, I was happy to see Lo declare at the end of the mission, in 1999: “ISO has been a remarkable success story for European Astronomy”.

Lo chaired the search committee that preceded my designation as ESO DG. I am grateful to him for this mark of confidence in me, but even more for the legacy he left me and all European astronomers, the fantastic set of telescopes that Europe acquired thanks to his foresight, his steadfastness and his powers of persuasion.


A skilled negotiator
Virigina Trimble
Professor of Physics & Astronomy, University of California Irvine

I never visited ESO/Garching during Lodewijk’s term as Director General, but the first time I walked into ESO headquarters for a conference under his successor's directorship, I knew immediately "LW was here," because the carpets leading to the library were blue, a favourite colour of his. Lodewijk (nearly) always wrote in green ink, carried a pocket watch, and spoke what some fellow-countrymen called "Oxford Dutch".

His grandfather, Jan Woltjer, Sr. was a professor of classical languages in Amsterdam. Jan Woltjer, Jr. (1891 Amsterdam – 1946 Leiden) received a PhD from Leiden in 1918 for work with Willem de Sitter on the theory of the motion of Saturn's moon Hyperion. He is best known for showing that Hyperion’s motion is chaotic; the first clear example in astronomy (later cited by former IAU President Kozai). His later work was astrophysical, concerning pulsation theory in variable stars, and including a late paper on the dynamics of the solar chromosphere.

Jan, Jr. married Hillegonda Hester de Vries. Their four children were all scholars, Anna (later Halasz, sociology), Margo (later Decker, classical languages), Jan Julian (history), and Lodewijk (astronomy). All were born in the Netherlands. Lodewijk's parents sent him to Switzerland for part of the Second World War. He returned with fluent French and a love for the French-speaking part of the country, calling Geneva "a very livable city." It was there that I saw him for the last two times, in December 2015 and July 2019.

With the advancing years, Woltjer's right eye deteriorated to complete blindness, so that he had no binocular vision, and he described his method of distance determination as the analogue of dynamical parallax. We collaborated on two papers, one on the Crab Nebula published in 1971 and "Quasars at 25" the outcome of an IAU Symposium in Bangalore India, published in 1986. We had planned a joint Annual Review on dark matter to be written that same year, but he became rather busy with plans for the New Technology Telescope and VLT for ESO, disagreed about the first paragraph, and the paper ended up as just Trimble 1987.

Many of the more official commentaries remark upon how very skilled LW was in bringing disparate interests to agreement when chairing boards, committees, panels, and all. His own description of the method was to let everyone say everything they had to say at length until they were talked out. He then offered a summary (including the main point he had in mind) and asked whether anyone disagreed or wanted to say more. They almost never did. I have tried this a few times, with only moderate success. Perhaps, like Feynman diagrams, the method worked best for its originator. At times also when someone wanted something, he would say "yes, or instead, we could..." (and offer something else he found more attractive).


Elegant, sharp & quick
Pierre Léna
ESO Council Member for France (19861993)
Member, Académie des sciences, France

While publishing the story of his ESO years (1975–1987) in 2006, complemented by his broad vision on space astronomy missions, Lo Woltjer called his book “Europe’s Quest for the Universe”. Notwithstanding his known discretion and reserve, shown by the impersonal tone of the chapters, he could really have called it: “My struggles for European access to the Universe”.

Lo’s scientific life, and more than often personal life, were devoted to this grand task ⁠— so understandable for a man who was the son of an astronomer, born in 1930 in the Netherlands, and who during his youth saw the rise of Nazism, the devastation of science in Europe and the flourishing of the US science during his post-war stay in Columbia and Princeton.

Appointed to the ESO Scientific and Technical Committee in 1978, fairly ignorant myself of ESO’s potential, I met Lo for the first time. Today, only a handful of us can recall his way of communicating his ambition during this epoch. Elegant, sharp in his analysis, quick to identify the critical points, prudent in avoiding confrontations when they could jeopardise his project, he did not try to convince, he simply decided to go ahead no matter what. I was immediately seduced by his character. His esteem for the French scientific tradition (and cuisine!) helped, at a moment where some French astronomers were hesitant to invest in ESO.

Indeed, the next decade was full of fantastic moments. Lo’s leadership drove a team of staff members, with Daniel Enard, Daniel Hofstadt in La Silla, Massimo Tarenghi, Ray Wilson, and close partners such as Immo Appenzeller, Reimar Lüst, Franco Pacini, Giancarlo Setti, Jean-Pierre Swings. There, the VLT was conceived, designed, discussed, presented for the first time to the European astronomical community in 1983. I was amazed by Lo’s trust in my youthful enthusiasm, and sometimes unconventional propositions for the VLT, such as building an interferometer, the future VLTI. The final approval of the VLT by the 1987 Council could have been the beginning of a triumphant new era for Lo. But, as he told me in confidence, in a rare moment, “there are certain things in life which one may want to do”, and he left ESO, retiring on the Olympus of his success. He would indeed go on to do many “certain things”, including the creation of the European Astronomical Society, the chairing of the International Astronomical Union and the chairing of the European Space Agency Space Science Advisory Committee (SSAC) with the Horizon 2000 programme.

Lo’s wife Ulla Demierre shared, with great love, this new life of Lo, and a small circle of friends celebrated his 80th birthday at La Pérouse in Paris, knowing what they owed to his vision. Behind the exquisite courtesy, elegance and often distant attitude, including some skepticism about human nature, Lo’s humanity was deeply present, always in search of friendship. Writing with Roger Bonnet, who retired on a similar “Olympus”, the book “Surviving 1,000 Centuries. Can we do it?” This was not a figure of speech, it expressed Lo’s preoccupation for humanity, and in this way he extended his field of enquiry and preoccupations to the future of all humans.

Lo and Ulla have left us, but their joint heritage will endure.


Lasting legacy to ground-based European astronomy
Bob Williams
Director of the Cerro Tololo Inter-American Observatory (19861993)
Director of the Space Telescope Science Institute (STScI) (19931998)

It was my pleasure to serve as Director of the Cerro Tololo Inter-American Observatory in Chile at the same time that Lo was ESO Director General. Site testing on Cerro Paranal was just beginning in this period and we met on the occasions that Lo visited La Silla to discuss matters of interest to both observatories. Our discussions were always cordial and collaborative in nature although there were a few situations when admittedly a bit of competition may have been detectable in the background, for example, the observations of SN 1987A.

After Lo stepped down as Director General in 1987 our relationship became much more social. Lo and his wife Ulla very much enjoyed Chile and the many friends and associates who remained connected with ESO. In particular, Daniel Hofstadt ⁠— who served for years as the ESO Head of Mission (Jefe de Misión) in Santiago and was the primary contact for Lo on official matters related to ESO and the Chilean government ⁠— and his wife Sonia developed a very strong friendship with Lo and Ulla.

As Jefe de Misión for CTIO I often worked with Daniel on official matters that impacted both observatories. My wife Elaine and I became good friends with the Hofstadts, who were (and remain!) marvelously outgoing and sociable. They had fallen in love with the south of Chile and along with several other ESO staff members had bought property on the shores of Lago Rupanco. Hard not to become enchanted with the beauty of the Chilean lake district, we often visited the Hofstadts at Rupanco during the Chilean summers.

On one of Lo and Ulla’s visits to Santiago and Lago Rupanco, Elaine and I joined the Hofstadts and Woltjers for a week at the lake. We made lefse for Christmas (Elaine has Norwegian roots) and kayaked each morning and afternoon, making sure to finish each day with pisco sours on the deck of the Hofstadts’ summer home.

Lo and I maintained a strong professional relationship at a time when we both served as officers on the Executive Committee of the IAU. In retrospect, it can be said that Lo Woltjer played a key role in the expansion of European ground-based astronomy in many areas at world-class level. His leadership of ESO in the era of the development of thin-mirror technology, active optics, data archiving and management, the New Technology Telescope, and the VLT are all legacies of his clear vision and unique scientific and administrative abilities.

Numbers in this article

12 Number of years that Lo Woltjer was ESO Director General.
16 Diameter of the telescope (in metres) that Lo Woltjer aimed for.
75 Approximate number of staff working in Garching at the time of Lo Woltjer’s tenure.
89 Age of Lo Woltjer when he died.
1930 Year that Lo Woltjer was born.
1975 Year that Lo Woltjer took over as ESO Director General.
1983 Year that the Very Large Telescope was presented for the first time to the European astronomical community.
1987 Year that Lo Woltjer received the green light for the Very Large Telescope.
1987 Year that Lo Woltjer stepped down as ESO Director General.
1994 Year that Lo Woltjer became President of the IAU (from 1994-1997)
1997 Year that Lo Woltjer presided over the IAU General Assembly in Kyoto.
1999 Year of the VLT inauguration.
2006 Year that Lo Woltjer published the story of his ESO years “Europe’s Quest for the Universe”
2008 Year that Lo Woltjer and Roger Bonnet published “Surviving 1,000 Years. Can We Do It?”