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Curiosity 449th Dies Natalis

University ceremony

Dies Natalis

Thursday 8 February 2024
Pieterskerkhof 1A

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News articles and video

The theme of the celebration of Leiden University's 449th Dies Natalis is curiosity: the inquisitive behaviour that is at the basis of all science and that also engages and moves us forward in our daily existence.

Dies lectures and honorary doctorate

The first Dies lecture will be delivered by cognitive psychologist Prof Mariska Kret, who does fundamental research on expressions of emotions in humans and animals. This year, a second Dies lecture will be given by astronomer Prof. Sara Seager, who has, among other things, developed methods to investigate to what extent the atmospheres of certain exoplanets are suitable for life. For her work, which is both academically and socially important, during this celebration Prof. Seager will receive an honorary doctorate from Ignas Snellen, professor of observational astrophysics and scientific director of the Leiden Observatory.

Opening speech

Rector magnificus Hester Bijl takes a closer look at this dies celebration’s theme: curisosity.

Dies lecture by Mariska Kret

Professor Mariska Kret, professor of cognitive psychology, lectures on the differences, but even more about the similarities between the ways in which human beings express their emotions and the ways that animals do this.

Esteemed audience, how curious are you? Part I

Researchers pique your curiosity, but fortunately supply you with answers as well!

Conferral of honorary doctorate

Under the auspices of Prof. Jasper Knoester, dean of the Faculty of Science, Professor Sara Seager (Massachusetts Institute of Technology, Cambridge, USA) will receive an honorary doctorate for her research into the atmospheres of exoplanets from Professor Ignas Snellen, Professor of Observational Astrophysics and scientific director of for the Leiden Observatory.


Performed by the Leiden Student Choir and Orchestra Collegium Musicum.

Dies lecture by Sara Seager

Our freshly appointed honorary doctor looks beyond the world of our own solar system, driven by a curiosity to know whether, somewhere in the universe, there exists a planet with an atmosphere that enable huan life. Or, in other words: does Planet Earth have a twin? 

Esteemed audience, how curious are you? Part II

More questions, more answers!

Conversation and closing remarks by Annetje Ottow

In a converstation with Willemijn Vader (Vitroscan), Ruben van Dijk (PastForward) and Marret Noordewier (Knowledge Centre Psychology and Economic Behaviour), President of the Executive Board Professor Annetje Ottow explores the impact of curiosity on research, education and business.


As is tradition, the Dies Natalis ceremony is concluded by jointly singing the national anthem.

Drinks reception

  • Hester Bijl Rector Magnificus

    Hester Bijl studied Applied Mathematics at Delft University of Technology, where she also obtained a PhD in numerical mathematics in 1999. She also obtained a master's degree in English Language and Literature from Leiden University. For her research on applications of numerical fluid dynamics in aerospace and wind energy technology, she received, among other things, person-oriented grants from NWO. She was a member of the first cohort of the Young Academy of the KNAW and also served on its board. From 1999 to 2003, she was a visiting researcher at NASA Langley Research Center for several periods. 

    Before coming to Leiden in 2016, where she was appointed vice-rector magnificus, Bijl spent 17 years at Delft University of Technology's Faculty of Aerospace Engineering, where she eventually held the position of dean.

    In 2021, Bijl succeeded Carel Stolker as Rector Magnificus of Leiden University.

  • Mariska Kret Professor Cognitive Psychology

    Prof.dr. Mariska Kret (1982) is professor of cognitive psychology at Leiden University. After completing a PhD on human body language perception, she gradually shifted her work to comparative research on great apes and patients with mental illness. She now heads the CoPAN (Comparative Psychology and Affective Neuroscience) lab. An essay she co-wrote with Yena Kim, “The function of emotional expressions: An ontogenic and phylogenic comparison,” was recently included in The Oxford. In 2022, her book 'Between grimace and smile – Expressions of emotions in humans and animals' was published in which she shows the differences and similarities between humans and animals in the expressions of their emotions.

  • Annetje Ottow President of the Executive Board

    Annetje Ottow studied Law at Leiden University, receiving a Master of Laws (cum laude) in business law, and went on to receive a Master of Laws from Queen Mary College in London in 1990. She then worked in the legal profession for 16 years, first at De Brauw Blackstone Westbroek and later as a partner at Houthoff Buruma. From 2006 to 2013, she was a member of the Board of the Independent Post and Telecommunications Authority (OPTA).  

    In 2007, Ottow was appointed professor of Public Economic Law at Utrecht University. From 2014 to 2018, she was dean of the Faculty of Law, Economics, Governance and Organisation there, and Vice President of the Executive Board from 2018 to 2021.

    In 2021 she succeeded Carel Stolker as President of the Executive Board of Leiden University.

Marieke Epping, science communications adviser at Leiden University, explains how you, the audience, can put your curiosity to work. Scan the QR code on one of the screens in the Pieterskerk or on the card in the showcase and show how creative curiosity makes! Four researchers will bring the redeeming answer and explain what you saw.

  • Lennard Kwakernaak, PhD student at the Leiden Institute for Research in Physics, knows all about the rubber object on display.
  • Michiel van Elk, associate professor of Cognitive Psychology, even wears a helmet when not on a motorbike.
  • Anne van der Does, associate professor at the PulmoScienceLab Leiden, LUMC, wants to find it in the little things.
  • Valerio Gentile, PhD candidate in Archaeology, hopes the pen remains mightier than the sword.

Honorary doctor

  • Sara Seager Professor of Planetary Science and Physics Massachusetts Institute of Technology

    Professor Sara Seager is a Canadian-American astrophysicist at the Massachusetts Institute of Technology. She pioneered many research areas of exoplanets—planets orbiting stars other than our sun. Her extensive and innovative methods have established the groundwork for the possibility of discovering another Earth.


Honorary promoter

  • Ignas Snellen Scientific director / Professor of Observational astrophysics

    Professor Ignas Snellen is a professor of Astronomy at Leiden University. After concluding his PhD research in Leiden in 1997, he worked for three years as a postdoctoral fellow at the Institute of Astronomy in Cambridge (UK), after which he became an astronomy lecturer at the University of Edinburgh. Snellen returned to Leiden University in 2004. His main area of research is the atmosphere extrasolar planets, by means of earth-based telescopes


  • Jasper Knoester Dean / Professor of Science

    Prof. Jasper Knoester obtained his PhD at Utrecht University in 1987. In 1993, he became Professor of the Theory of Condensed Matter at Groningen University. From 2003 to 2009, Kn was scientific director of the Zernike Institute for Advanced Materials in Groningen, and from 2010 to 2021, he was dean of the Faculty of Science and Engineering at the University of Groningen. As of January 2022, he is dean of the Faculty of Science of Leiden University.

Leiden Student Choir and Orchestra Collegium Musicum

On November 15, 1936, the Leiden Student Chamber Orchestra Collegium Musicum was founded and in 1964 they officially merged with the Leiden Student Choir, which had been founded in 1934, to form the Leiden Student Choir and Orchestra Collegium Musicum.

Gerrit Maas has been leading the choir since 2019 and Jeppe Moulijn, after having been orchestra conductor at Collegium Musicum since 1993, became the permanent orchestra conductor in 2015. Thanks to their efforts, the level of Collegium Musicum remains high.

Collegium Musicum's musicians perform three movements from Henry Purcell's Fairy Queen:

  • Sing while we trip it
  • If love's a sweet passion
  • Now the night

Composition of the chamber choir

  • Irene Abspoel - Pedagogical sciences
  • Margaux Jacquemart - Psychology
  • Tessa Bosch - Archaeology
  • Femke Pieterse - Philosophy
  • Eline Schoonhoven - Industrial Ecology
  • Altos
  • Amy de Jongh - Educational Sciences
  • Hannelore van Es - Psychology
  • Leoniek Koster - Greek and Latin Language and Culture
  • Tara Pijpers - Archaeology
  • Josefien Garcia Weenink - LUC The Hague
  • Oscar Ociepka - Physics
  • Willem van den Berg - Middle Eastern Studies
  • Vincent van Zijtveld - Graduate
  • Serkan Esiner - Graduated
  • Erki Elbrecht - Data Science & AI
  • Emiel Beinema - Communication Design for Innovation
  • Benjamin Plomp - Greek and Latin Language and Culture, Russian Studies
  • Paolo Lammens - Mathematics

Soloist: tba
String quartet and harpsichord: tba
Conductor: Gerrit Maas

Collegium Musicum website

Van Hagerbeer organ

The first organ to be installed in what is now called Pieterskerk church, dates from 1446 and was probably built by Jacob van Biltsteyn from Kampen. In 1639, the instrument was restored by father and son Van Hagerbeer.  To this day, about 100 pipes from the original organ are part of the Van Hagerbeer organ, ranking them among the oldest sounding organ pipes in the world.

Works to be performed


14:40 - 14:50
  • Fantasia (G dorisch) - Jan Pieterszoon Sweelinck (1562 - 1621)
  • Fantasia sopra Sollare (FbWV 204) - Johann Jacob Froberger (1616 - 1667)
Entrance of processions
  • Fantasia - Abraham van den Kerckhoven (1618? - 1701)
  • Toccata en fuga F-dur, BuxWV 157 - Dietrich Buxtehude (1637 - 1707)
  • Fuga C-dur, BuxWV 174 - Dietrich Buxtehude 

About the organist

The Van Hagerbeer organ is played by Jan Verschuren, who studied organ at the conservatories of Leuven and Utrecht. Organ recitals have taken him throughout Europe. Verschuren succeeded Folkert Grondsma as the organist incumbent at the Hartebrugkerk in Leiden and he is also the university organist for Leiden University and the Technical University Eindhoven. In 2002 he was decorated by the Société Académique des Arts-Sciences-Lettres in Paris for his contributions to promoting French organ music. Today, Verschuren will be accompanied by Bert Crama to handle the various sets of stops.

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