OUDE STERREWACHT LEIDEN – OBSERVATOIRE DE LEYDE

Leiden University, founded in 1575, is the oldest university in the Netherlands. As early as 1633, astronomy played an important role, with the establishment of an observatory - today the oldest university observatory in the world - to house a precious Snellius quadrant, an instrument for measuring distances and angles. For the first two centuries, the observatory was mainly used for educational purposes.

In 1861, under the leadership of astronomer Frederik Kaiser, the construction of a new observatory was promoted as a means of sustainably strengthening astronomy in the Netherlands. In the late 19th and early 20th centuries, Leiden became a world-renowned scientific center, attracting famous physicists such as Paul Ehrenfest, Hendrik Lorentz, Pieter Zeeman and Heike Kamerlingh Onnes, some of whom went on to win the Nobel Prize.

In 1919, Willem de Sitter, a specialist in the theory of relativity, became director of the observatory and collaborated with Albert Einstein in the early 1930s. From 1945 to 1970, Jan Hendrik Oort ran the site and became the most famous Dutch scientist. He is notably credited with the discovery of the "Oort cloud", located at the very edge of the solar system and serving as a reservoir for comets.

In the twentieth century, city observatories could no longer remain at the cutting edge of astronomical research due to various forms of pollution, notably light pollution. Naturally, after the creation of the European Southern Observatory (ESO) in 1962, Dutch astronomy, like that of other European countries, moved to the new observatories built in the southern hemisphere, notably in Chile. Since the late 1970s, astronomers have no longer been housed in the observatory building, but in the Jan-Hendrik Oort building and the Huygens laboratory on the Wassenaarseweg site.

For a time, it was feared that the old observatory would be abandoned. Fortunately, renovation and refurbishment work was carried out between 2008 and 2012, preserving this scientific and historical heritage.

Each year, a new exhibition on the interface between astronomy and society is presented, and guided tours are offered at set times. These allow visitors to discover the exhibition and a telescope that is over 120 years old! At weekends, the exhibition can be visited as part of a tour of the botanical garden (Hortus Botanicus).