At its abrupt termination in January 2012 the SIU research topics were solar physics (including running the revolutionary Dutch Open Telescope), stellar and galaxy evolution, supernova and high-energy astrophysics, experimental spectropolarimetry. In each field, the SIU had high standing. Its astrophysics-oriented education program was particularly renowned.
The earlier history of Utrecht astronomy is described well in the brochures by M.G.J. Minnaert and by C. de Jager linked below (in Dutch). Here I summarize the 50-year period I was part of it. I describe Utrecht solar physics - the major research topic during the past century - separately on this page.
During the 1960s, under C. de Jager and with the addition of full professors A.B. Underhill and H.G. van Bueren, the Sterrewacht diversied into many research interests next to the solar spectrum (giant stars, stellar winds, solar MHD and radio physics, solar and stellar X-ray physics, plasma-astrophysics, heterodyne detection techniques). Theoretical astrophysics and astronomical instrumentation were added to the curriculum. It became the most astrophysics-oriented institute in The Netherlands and grew rapidly to a 1970s staff of 20 tenured scientists with 30 support personnel, including large mechanics and electronics workshops. At the same time, De Jager's newly founded Space Research Laboratory (now SRON) grew to well over 100 employees. De Jager ran the Sterrewacht in the mornings, his space lab in the afternoons, edited the journals he had started (Solar Physics, Space Science Reviews) in the evenings, ran the Flemish Astrophysical Institute in Brussels (which he founded) in frequent visits, and held high-level posts in the IAU, COSPAR, ICSU, Dutch Academy of Sciences, and many more.
PhD students from that golden era of Sterrewacht Sonnenborgh who later became astronomy professor (at Utrecht or elsewhere): M. Kuperus, C. Zwaan, E.P.J. van den Heuvel, W. van Rensbergen, H.J.G.L.M. Lamers, J.M.E. Kuijpers, M.W.M. de Graauw, R.J. Rutten, H.C. Spruit, A. Achterberg, F.W.M. Verbunt, J. Heise, P.C.M. Martens, L.B.F.M. Waters. Other well-known astronomers who got their PhD at Utrecht during that period and went abroad: J.M. Beckers, A. Greve, A.A. van Ballegooijen, C.J. Schrijver, F.B.S. Paerels, R.G.M. Rutten.
In 1987 the university astronomy group moved from Sterrewacht Sonnenborgh to out-of-town campus “De Uithof”. Earlier, De Jager had laid ambitious plans to house both astronomy and space research together in a large new building in an immense 1880s fortification (Fort Rhijnauwen) just south of De Uithof, but the era of expansion was over. Eventually, the closure of some physics departments vacated a floor of the Buys Ballot Laboratorium in De Uithof for astronomy. The professors at that time were A.G. Hearn, M. Kuperus, H.J.G.L.M. Lamers, C. Zwaan. The major reseach interests were solar physics, cool-star activity, hot star winds, accretion disks, plasma astrophysics. Solar radio spectrometry (with the 25-m dish at Dwingeloo) had been terminated in 1984. The development of heterodyne detection in the infrared had moved to SRON Groningen with M.W.M. de Graauw, followed later by H. van de Stadt.
The space research laboratory (SRON Utrecht) moved into an adjacent former physics building in 1990. The strong ties in solar physics and ultraviolet spectroscopy were gone; the collaboration became limited to non-solar X-ray astronomy, the field of the new director J. Bleeker.
After its move the astronomy group (“Vakgroep Sterrekunde”, renamed Sterrekundig Instituut Utrecht) lost its independence and was systematically reduced by the physics administration. At the completion of the Utrecht Echelle Spectrometer for the William Herschel Telescope on La Palma, the sizable instrumentation program was killed except for Hammerschlag's Dutch Open Telescope. Although F.W.M. Verbunt added high-energy astrophysics and H.J.G.L.M. Lamers and N. Langer added stellar and galaxy evolution to the research program, the university contingent dwindled down to only 8 academic and 2 support staff at the time of the closure. Fortunately, externally funded (NWO, NOVA, EC) graduate students, postdocs and overlap staff plus the high quality of teaching and students compensated for this trend, so that critical mass and a lively research and professional education environment were maintained.
Also in the more meager recent years Utrecht astronomy maintained a steady production of first-class astrophysicists, exploiting the field's attractiveness to gifted students. Many now work in astrophysics abroad (seventeen in solar physics alone). In addition, numerous Utrecht-trained astronomers enrich wider society. The national Dutch meteorology institute was the largest taker, employing many in climate research where knowledge of numerical radiative transfer is a valuable asset. Others became researcher in fields ranging from physics (theoretical, nuclear, technical, medical) to Akkadian, or started a career as, e.g., teaching-academy teacher, high-school teacher, business analyst, oil explorer, systems analyst, software engineer, aerospace engineer, human resources manager, musician, publicist, popular-science journalist, car importer, and more.
C.U. Keller (chair experimental astrophysics) became SIU director in 2009 and started a new instrumentation program for spectropolarimetry. Utrecht was even slated to become the Dutch center for optical and infrared astronomy instrumentation, next to already having the main Dutch center for space research. Stronger ties with the latter were also formalized and funded by Utrecht University. There were advanced plans to co-locate the SIU, NOVA instrumentation, and SRON in a new building. The sudden stupidity of the Utrecht University board upset these bright prospects. The Utrecht astronomers moved elsewhere to continue their research, but the SIU, Utrecht solar physics, and Utrecht astronomy education are irrepairably gone.
At this loss of its close partner SRON decided to leave Utrecht. It first selected Amsterdam but then found better connections at Leiden (astronomy there, technology in Delft) and moved to a new building on the Leiden science campus in 2021. All that remains in Utrecht is Museum Sterrenwacht Sonnenborgh and the astronomy record embodied in the 171 PhD theses listed below. Another Utrecht University scandal is that these are not scanned into web-available pdf's.
I spent fifty years in Utrecht astrophysics, the first half at Sterrewacht Sonnenborgh where I started in 1961 following Minnaert's courses and practica, the second half at the Sterrekundig Instituut Utrecht in De Uithof until its termination.
Utrecht solar physics
List of Utrecht astronomy PhDs
M.G.J. Minnaert's beschrijving van Sterrewacht Sonnenborgh uit 1953
C. de Jager's beschrijving van Sterrewacht Sonnenborgh, 1977
Hans Nieuwenhuijzen's photographs 1956-2012
Leo Molenaar's brochure over Minnaert bij de opening van het Minnaertgebouw in 1998
Leo Molenaar's biografie van Minnaert “De rok van het universum”
Sterrekundig Instituut Utrecht
Buys Ballot Laboratorium
Archived SIU webpage
Former directions to get to the SIU: html pdf