Skip to ContentSkip to Navigation
Research Kapteyn Institute About the institute

Kapteyn History

by P.C. van der Kruit
Painting of J.C. Kapteyn at his desk by Jan Veth. This painting dates from 1918 and was made at the occasion of his 40th anniversary as professor in Groningen. On the wall behind Kapteyn a picture of David Gill. The painting now resides in the Kapteyn Room in the Kapteyn Astronomical Institute
Painting of J.C. Kapteyn at his desk by Jan Veth. This painting dates from 1918 and was made at the occasion of his 40th anniversary as professor in Groningen. On the wall behind Kapteyn a picture of David Gill. The painting now resides in the Kapteyn Room in the Kapteyn Astronomical Institute

Kapteyn's time

The Institute has been named after the founder, Jacobus Cornelius Kapteyn, who lived from 1851 to 1922. Kapteyn was appointed professor of astronomy and theoretical mechanics in 1878 at a time when no astronomical tradition, let alone an observatory, existed in Groningen. The chair was instituted as a result of the new law on higher education of 1876, in which it was stipulated that the three government subsidized universities at Groningen, Leiden and Utrecht would teach the same curricula, so a new chair in astronomy had to be established in Groningen. Leiden and Utrecht already had such chairs and these were supported by observatories. However, the government did not provide funds to establish another one at Groningen (and the other two astronomy professors together effectively blocked this by giving negative advice so that they would not have to share the available funds with a third party).

The title page of the first volume of the Cape Photographic Durchmusterung. The page shown here is from one of the copies of the CPD in the library of the Kapteyn Astronomical Institute. The signature of Willem de Sitter has been crossed out; it presumably has been de Sitter's private copy.
The title page of the first volume of the Cape Photographic Durchmusterung. The page shown here is from one of the copies of the CPD in the library of the Kapteyn Astronomical Institute. The signature of Willem de Sitter has been crossed out; it presumably has been de Sitter's private copy.

Sir David Gill at Cape Town had been struck by the possibility of counting and cataloguing stars on photographic plates and mentioned this in correspondence with Kapteyn. He lacked the manpower to measure star positions and magnitudes (astronomical jargon for brightnesses), but proceeded anyway to photograph the southern skies. Eventually he succeeded in luring Kapteyn into offering his services. Kapteyn proceeded measuring Gill's plates and this resulted after 12 years of hard work in the publication of the Cape Photographic Durchmusterung in three volumes between 1896 and 1900. In this Durchmusterung the positions and magnitudes of 454,875 stars are catalogued. To perform these tasks Kapteyn founded an Astronomical Laboratory, an “Observatory without telescopes”, that eventually was named after him.

Kapteyn's illustration of his two Star Streams (1904). At only a selection of the regions for which he had data (10 of the available 28), he plots the distribution of proper motions on the sky. If there were no preferential streaming each distribution would be round, but Kapteyn found these distributions to be asymmetrical and to point to an apex in the middle of the figure. The systematic behaviour across the sky is evidence for two Star Streams. It was soon shown by K. Schwarzschild that the pattern could in an alternative, but much more physical manner be explained as an anisotropy in the distribution of the stellar velocities.
Kapteyn's illustration of his two Star Streams (1904). At only a selection of the regions for which he had data (10 of the available 28), he plots the distribution of proper motions on the sky. If there were no preferential streaming each distribution would be round, but Kapteyn found these distributions to be asymmetrical and to point to an apex in the middle of the figure. The systematic behaviour across the sky is evidence for two Star Streams. It was soon shown by K. Schwarzschild that the pattern could in an alternative, but much more physical manner be explained as an anisotropy in the distribution of the stellar velocities.

Kapteyn's main interest was the Structure of the 'Sidereal System'. But this required measuring distances of stars. However, direct measurements from the reflection on the sky of the Earth’s motion around the Sun are possible only for the nearest stars. He designed a novel, statistical method, so-called secular parallax measurements, to statistically estimate distances of stars, making use of the fact that the displacement of a star on the sky resulting from the motion of the Sun through space decreases with distance. These displacements on the sky, called proper motions, of course contain a component due to the star's own motion in space as well, which is why it can only be applied statistically. This required the peculiar motions of stars in space to be random and isotropic (without preferred directions). Kapteyn’s first major discovery was that this in fact is not true, but apparently there are two 'Star Streams', which he announced in 1904 at the St. Louis International Exposition. He found that the space motions of ‘common’ stars in the solar neighborhood showed two preferential directions; later this was explained by Karl Schwarzschild as the result of an anisotropy of stellar motions in a velocity ellipsoid with unequal axes. The streams then are the opposite directions in which the random motions are largest.

First page of a manuscript (undated) by Kapteyn for the "Plan of Selected Areas". At the bottom he says: "Suggestions for the improvement of the plan are earnestly requested. If needed the plan can afterwards be printed, advantage being taken of these suggestions. That this plan originated at the Laboratory in Groningen need not create surprise. The nature of our astronomical institution makes our work dependent on that of other observatories.'' This manuscript resides in the Kapteyn Room at the Kapteyn Astronomical Institute.
First page of a manuscript (undated) by Kapteyn for the "Plan of Selected Areas". At the bottom he says: "Suggestions for the improvement of the plan are earnestly requested. If needed the plan can afterwards be printed, advantage being taken of these suggestions. That this plan originated at the Laboratory in Groningen need not create surprise. The nature of our astronomical institution makes our work dependent on that of other observatories.'' This manuscript resides in the Kapteyn Room at the Kapteyn Astronomical Institute.

Kapteyn developed methods to derive the space distribution of stars from star counts as a function of magnitude (brightness) all over the sky and mapping of the apparent displacements, called proper motions, of stars due to their motion in space with respect to the Sun. He worried extensively about absorption of starlight by interstellar material and published two papers on that in the Astrophysical Journal in 1909. In the end, he concluded that there indeed was evidence for such absorption. He had correctly realized that absorption (in fact in practice mostly scattering of light by small dust particles) would depend on wavelength, making stars appear redder at large distances. In fact his derived amount, improved in his student Pieter van Rhijn’s PhD thesis, in is not too bad at all, although it is now known to be restricted to close to the plane of the Milky Way Galaxy. Later Harlow Shapley in the US showed that absorption towards a globular cluster outside the Milky Way was virtually absent, at least substantially less than Kapteyn’s value. This lead astronomers, including Kapteyn, to incorrectly follow Shapley and ignore interstellar absorption everywhere, including near the Milky Way, in the 'disk' of the Galaxy.

This picture of Kapteyn was made at the Monastery (the residence of visiting astronomers) at the Mount Wilson Observatory during one of Kapteyn's annual visits in 1908. Kapteyn is holding a copy of the literary magazine "The Dial". This picture has been supplied by Dr. T.D. Kinman, courtesy of the Observatories of the Carnegie Institution of Science.
This picture of Kapteyn was made at the Monastery (the residence of visiting astronomers) at the Mount Wilson Observatory during one of Kapteyn's annual visits in 1908. Kapteyn is holding a copy of the literary magazine "The Dial". This picture has been supplied by Dr. T.D. Kinman, courtesy of the Observatories of the Carnegie Institution of Science.

Kapteyn also pioneered international collaborations and was very successful in that; in this the necessity for him to work with plates, taken by others and measured in his observatory without a telescope, and his Anglo-Saxon orientation (contrary to the German orientation so common in those days) must have been important factors in this. He became a good friend of George Ellery Hale and between 1908 and 1914 spent his summer months as research associate at the Mount Wilson Observatory in California. In 1906 he published his Plan of Selected Areas, in which observatories all over the world would measure positions, magnitudes, proper motions (and for the brighter part also spectral types and radial velocities) in a set of carefully chosen fields distributed over the whole sky.

In St. Louis Kapteyn had become good friends with George Ellery Hale. The latter was so impressed by Kapteyn that when in 1906 he was completing the construction of the largest telescope in the world, the 60-inch at Mount Wilson near Pasadena and Los Angeles, he adopted Kapteyn’s Plan as the major observing program for his new giant telescope. This also resulted in an invitation to Kapteyn to become a research associate of the Carnegie Institution of Washington at the Mount Wilson Observatory in California to oversee this work. Indeed Kapteyn, from the second time onward accompanied by his wife, spent his summer months in California from 1908 on until 1914 when the 'Great War' prevented travel across the Atlantic.

The original Kapteyn Astronomical Laboratory at the Broerstraat in the center of Groningen. This picture has been taken around 1920.
The original Kapteyn Astronomical Laboratory at the Broerstraat in the center of Groningen. This picture has been taken around 1920.

Kapteyn never succeeded in establishing an observatory at Groningen. But he did secure a building for his "Astronomical Laboratory", which was opened in 1896 in a temporary location and after a few moves to its final location (in the Broerstraat in the center of Groningen next to the University's central building) in 1913. After Kapteyn's retirement in 1921 and shortly before his death in 1922, the curators of Groningen University decided to name the astronomical laboratory after Kapteyn.

Towards the end of his life Kapteyn published with Pieter van Rhijn a schematic model for the distribution of stars in space (Astrophysical Journal, 1920), followed by his 'First attempt at a theory of the arrangement and motion of the Sidereal System' (Astrophysical Journal, 1922). In this he laid the foundations for dynamical studies by combining observed space distributions with motions and derived a first value for the density of matter in the neighborhood of the Sun.

This Kapteyn Universe, a highly flattened system with the Sun reasonably close to its center suffered in the direction of the plane from absorption but is in the vertical direction even now very close to what we think it is now. Due to the neglecting of absorption the Kapteyn Universe is in the long direction about three times too small compared to what we now call the 'disk' of the Galaxy. Shapley had found that globular clusters were distributed in a roughly spherical structure concentrated towards a center in the plane of the Milky Way, but this was very much larger than Kapteyn’s Universe. This now is the 'halo' of the Galaxy, but also due to absorption Shapley’s system is too large by a factor two.

Kapteyn's Universe, consisting of a set of concentric ellipsoids. The numbers on the right (0.63, 0.40, 0.25, 0.16, 0.10, etc.) show the density at the surfaces of the ellipsoids in units of the central density, which is taken to be the density of stars near the sun, and this was determined as 0.045 stars per pc3. The circle labeled "S" indicates the position of the sun; this is located on ellipsoid 5, where the density is one-tenth of the central value. From Kapteyn (1922).
Kapteyn's Universe, consisting of a set of concentric ellipsoids. The numbers on the right (0.63, 0.40, 0.25, 0.16, 0.10, etc.) show the density at the surfaces of the ellipsoids in units of the central density, which is taken to be the density of stars near the sun, and this was determined as 0.045 stars per pc3. The circle labeled "S" indicates the position of the sun; this is located on ellipsoid 5, where the density is one-tenth of the central value. From Kapteyn (1922).

Kapteyn is less prominent internationally now, to some extent because his work on the structure of the Galaxy in the USA is usually seen as a competition between him and Shapley which was won by the latter. Kapteyn is described as having a capital blunder by ignoring interstellar absorption, while this in fact was prompted by Shapley. However, another major reason is that after the War Kapteyn took the position that it was a major mistake to exclude Germany and other defeated nations from international organizations such as the League of Nations, the International Research Council and the International Astronomical Union, a stand for which he was heavily criticized and condemned by many scientists and astronomers in the UK and USA in particular.

Van Rhijn and Blaauw

Drawing of Pieter Johannes van Rhijn, donated to the Kapteyn Astronomical Institute by his descendants. It resides in the Kapteyn Room.
Drawing of Pieter Johannes van Rhijn, donated to the Kapteyn Astronomical Institute by his descendants. It resides in the Kapteyn Room.

In 1921, Kapteyn was succeeded as Professor of Astronomy and Director of the Astronomical Laboratory by his assistant Pieter J. van Rhijn (1886-1960). The latter had obtained his PhD under Kapteyn in 1915. Kapteyn's first student, Willem de Sitter (1872-1932; PhD thesis in 1901) had become director of Leiden Observatory.

Kapteyn's most famous student was Jan Hendrik Oort (1900-1992), who had come to Groningen to study because of Kapteyn. He was undecided between physics and astronomy and has stated repeatedly that he had been turned to astronomy by Kapteyn. He worked under Kapteyn on high velocity stars, which later would put him on the discovery trail of Galactic rotation, but in 1922 still had to start thesis research. De Sitter offered him a job in Leiden and after two years at Yale to work under Frank Schlessinger he moved to Leiden. In the end, he did obtain his PhD in Groningen under van Rhijn in 1926 on the subject where he had already worked on in his Groningen years. Other students of van Rhijn, such as Peter van de Kamp (1901-1994; PhD in 1926) and Barthelomeus (Bart) Jan Bok (1906-1983; PhD in 1932) moved to the USA, where a position in astronomy was easier to obtain than in the Netherlands. Adriaan Blaauw (1916-2010) had come from Leiden to work with van Rhijn and worked in Groningen during the Second World War He eventually obtained his PhD in 1946, but went back to Leiden (Blaauw eventually returned).

Van Rhijn's attempts to obtain a telescope for the Laboratory with funds from the government failed. However, in 1931, he succeeded in requiring a 55-cm reflector and a dome on the Laboratory building financed with private funds. This telescope was mainly used by van Rhijn and Jan Borgman for studies of interstellar reddening. In 1959, the telescope was removed because of structural difficulties with the building.

The work done under van Rhijn during his long tenure of Professor and Director (1921 to 1957) concerned the further execution of the Plan of Selected Areas. It was not very innovative but time-consuming and routine work and the Kapteyn Laboratory lost much of its prominence. Most work went into determining the spectra of stars in these Areas; in collaboration with the Bergedorfer Sternwarte near Hamburg, prism-objective plates were analyzed in all northern hemisphere Areas, resulting in the Bergedorfer Spektral-Durchmusterung der 115 nordlichen Kapteynschen Eichfelder, completed in 1953. Blaauw has later often complained that Groningen should have been in the title since a substantial fraction of the work was performed there. Undeniably, the Kapteyn Laboratory went into a severe decline during van Rhijn's years.

Prof. Adriaan Blaauw, third director of the Kapteyn Astronomical Laboratory.
Prof. Adriaan Blaauw, third director of the Kapteyn Astronomical Laboratory.

In 1957, after the retirement of van Rhijn, Adriaan Blaauw was appointed as Professor and Director. Under his direction the research broadened into various other areas. And Blaauw was very much involved in the establishment of the European Southern Observatory ESO, an initiative by Oort in Leiden and Walter Baade, a German who worked most of his life at Mount Wilson and Palomar Observatories. After the first Symposium of the International Astronomical Union about Galactic Research held near Groningen in 1953, staff member Lukas Plaut was designated to conduct the Palomar-Groningen Survey of RR Lyrea stars in one of 'Baade's Windows' near the direction of the Galactic Center, which lasted up to the early 1970s. Jan Borgman facilitated that by designing and building an instrument that electronically could compare star fields such that variable stars were easily recognized (an automated version of a so-called Blink Comparator used visually). Stuart R. Pottasch was appointed as professor of astrophysics in 1963.

Under Jan Borgman, the Kapteyn Observatory in Roden was opened in 1965 with a 61-cm reflector. Borgman also started a working group 'photometry' for space research, that first used balloons but eventually resulted in a strong involvement in the Astronomical Netherlands Satellite (ANS; an ultraviolet and X-ray space observatory), that was used in orbit between 1974 and 1976. The Kapteyn Observatory remained heavily involved in the early development of the ESO, eventually situated in Chile after much site-testing in South Africa. Galactic structure remained a central area of interest. Under Hugo van Woerden a group was started to use the 25-meter radio telescope at Dwingeloo for studies of the neutral hydrogen gas in the Galaxy, an initiative originating from and strongly supported by Blaauw.

The WSN (Mathematics-Astronomy-Physics) Building on the Paddepoel Campus where the Kapteyn Laboratory has been located between 1970 and 1983.
The WSN (Mathematics-Astronomy-Physics) Building on the Paddepoel Campus where the Kapteyn Laboratory has been located between 1970 and 1983.

After 1970

In 1968, Blaauw became part-time Scientific Director of ESO and in 1970 Director General. Also in 1970 the Kapteyn Laboratory moved to a new location on the campus site in development near the northern suburb Paddepoel of Groningen. It is now called the Zernike Campus. The space research working group, now called the Laboratory for Space Research, also moved from Roden to Paddepoel. The original Kapteyn Laboratory was used for some time as part of the University's central administrative offices, but was damaged by a fire in the 1980s. The University's Board seized the opportunity to demolish the building. A restructuring of organizational structure of universities, sparked by student revolts demanding more involvement and influence on decisions in democratic procedures, took place around the same time, in which astronomy became a sub-faculty. Stuart R. Pottasch became the first Dean of the Sub-Faculty Astronomy (later Chairman of the Astronomy Department) from 1970 to 1982.

Staff and students in the Radio Group of the Kapteyn Laboratory in 1982. Renzo Sancisi and Piet van der Kruit were on sabbatical leaves, respectively in the USA and Australia and are missing on this photograph. From the Kapteyn collection, by Seth Shostak.
Staff and students in the Radio Group of the Kapteyn Laboratory in 1982. Renzo Sancisi and Piet van der Kruit were on sabbatical leaves, respectively in the USA and Australia and are missing on this photograph. From the Kapteyn collection, by Seth Shostak.

In 1970 also the Westerbork Synthesis Radio Telescope came into operation and the radio group of the Kapteyn Institute quickly became one of the major users. Especially after observations using the 21-cm line of neutral hydrogen became possible (to a large extent the result of efforts by Ronald J. Allen, who had been recruited as a postdoc and subsequently became a staff member), extensive studies were made of nearby galaxies, shifting the emphasis from structure of our own Milky Way Galaxy to that of external ones. Star formation, interstellar medium and gas in the Galaxy remained a second strong focus. In particular the so-called flat rotation curves of spiral galaxies and the evidence these present for large quantities of unknown 'dark matter' became a major subject of study. Renzo Sancisi and Miller Goss, in addition to Ron Allen, Tjeerd van Albada and Ron Ekers, lead the Westerbork studies, while Pieter C. van der Kruit combined radio studies with the new field of optical surface photometry on the basis of electronic scanning and digitizing of photographic plates with the Astrocan machine of Leiden Observatory.

Photographs of some of the senior staff of the Kapteyn Laboratory in 1980s. Top row (from left to right): Ron Allen, Ron Ekers, Miller Goss, Stuart Pottasch, Renzo Sancisi, Bottom row (from left to right): Bob Sanders, Ulrich Schwartz, Tjeerd van Albada, Piet van der Kruit, Hugo van Woerden. From the photo-collection of the Kapteyn Astronomical Institute, produced by Seth Shostak.
Photographs of some of the senior staff of the Kapteyn Laboratory in 1980s. Top row (from left to right): Ron Allen, Ron Ekers, Miller Goss, Stuart Pottasch, Renzo Sancisi, Bottom row (from left to right): Bob Sanders, Ulrich Schwartz, Tjeerd van Albada, Piet van der Kruit, Hugo van Woerden. From the photo-collection of the Kapteyn Astronomical Institute, produced by Seth Shostak.
The Kapteyn Room at the Kapteyn Astronomical Institute. The picture shows in the back Kapteyn's desk (with a sample of his publications) and globes, the painting by Jan Veth, and a star map he made as a teenager.
The Kapteyn Room at the Kapteyn Astronomical Institute. The picture shows in the back Kapteyn's desk (with a sample of his publications) and globes, the painting by Jan Veth, and a star map he made as a teenager.

The Space Research group, in the meantime under the direction of Reinder J. van Duinen, was a major contributor to the Astronomical Netherlands Satellite ANS followed by major participation in the NL/UK/NASA Infra-Red Astronomical Satellite IRAS, which was launched in 1983. Borgman had in 1975 become Dean of the Faculty of Mathematics and Natural Sciences, then became Rector Magnificus and subsequently chairman of the Board of Groningen University, and moved in 1988 to the Hague to become chairman of the Netherlands Organization for Scientific Research (NWO). The Space Research laboratory became part of the Netherlands Foundation for Space Research (SRON), financed by NWO.

The Kapteynborg, the current location of the Kapteyn Astronomical Institute
The Kapteynborg, the current location of the Kapteyn Astronomical Institute

In 1981, with the beginning of the Dutch involvement in the UK/NL Isaac Newton Group of optical telescopes at La Palma (Canary Islands), the Interuniversity Working Group for Astronomical Instrumentation was founded in Roden with personnel from Groningen and Leiden Universities. Under the leadership of Harvey R. Butcher and Jan Willem Pel it developed instrumentation for both ESO and La Palma.  The Working Group was transferred to the Radio Observatory in Dwingeloo in 1995 and made a name designing and building optical instrumentation; the Kapteyn Observatory at Roden was closed. In 1983, the Kapteyn Astronomical Institute moved to its present location in what was at first called the Zernike Building, now the Kapteynborg.

In 1982, Pottasch was succeeded by Ronald J. Allen as chairman of the Astronomy Department and this position was held subsequently by Hugo van Woerden from 1985 to 1991 and by Pieter C. van der Kruit from 1991 to 1994. In 1994, van der Kruit became Dean of the Faculty of Mathematics and Natural Sciences until the end of 1997. Also in 1994 the Astronomy Department (which had included the Kapteyn Laboratory in Groningen, the Kapteyn Observatory in Roden and the associated research within the Department for Space Research) was formally recognized by Groningen University as a research institute, which gave it some protected status, and was renamed the Kapteyn Astronomical Institute. Tjeerd S. van Albada became the Scientific Director, succeeded in 1998 by Piet van der Kruit.

In 1992, the astronomical institutes at the Dutch universities formed together the Netherlands Research School for Astronomy (NOVA) and were recognized as such by the Royal Netherlands Academy of Arts and Sciences. In 1998, the Minister of Education, Culture and Science organized an 'Bonus Incentives Scheme' (Dieptestrategie), in which the over 100 research schools in the Netherlands could compete for recognition as top research school and obtain considerable addition funding for a ten-year period. NOVA came out as number one in this nation-wide competition, in which only six were awarded the status top research school.

This has been extended since every ten or so years, during which ASTRON was given the label 'exemplary', a distinction shared with only one other research school in the Netherlands.

Due to additional resources and protected status of NOVA, as well as the relocation of the optical workshops to Dwingeloo, retirements and departing staff to other major institutions abroad, a significant extension and renewing of the scientific staff in Groningen took place between roughly 1990 and 2010. In 2021 there are about 18 permanent scientific staff and supporting technical, computer and administrative staff, some 20-30 postdocs and over 50 PhD students.

Due to additional resources and protected status of NOVA, as well as the relocation of the optical workshops to Dwingeloo, retirements and departing staff to other major institutions abroad, a significant extension and renewing of the scientific staff in Groningen took place between roughly 1990 and 2010. In 2021 there are about 18 permanent scientific staff and supporting technical, computer and administrative staff, some 20-30 postdocs and over 50 PhD students.

The scientific directors have been Thijs (J.M.) van der Hulst (2005-2011), Reynier F. Peletier (2011-2017), Scott C. Trager (2017-2020) and Léon Koopmans (2020-present). In 2017 the Faculty of Mathematical and Natural Sciences renamed itself to become the Faculty of Science and Engineering. The staff of the Kapteyn Astronomical Institute has been or is heavily involved with many ground based and space facilities, such as ESO, La Palma, ISO, Herschel, LOFAR, SKA, Euclid, and many more. They have been exceedingly successful in obtaining external funding, in addition to NOVA, and prizes and awards. These include grants from NWO and in personal grants such as Veni-Vidi-Vici of NWO and starting, consolidating and advanced grants of the European Research Council ERC. Piet van der Kruit has been named one of a few distinguished named professors in the Faculty (Jacobus C. Kapteyn Professor). Prof. Amina Helmi has been awarded the very prestigious Spinoza Prize, the highest scientific award in the Netherlands.

Literature

  • Kapteyn, zijn Leven en Werken, 1928, biography of Kapteyn by his daughter Henrietta Herzsprung-Kapteyn. Translated into English by P.C. van der Kruit at https://www.astro.rug.nl/JCKapteyn/.
  • In het voetspoor van Kapteyn: Schetsen uit het werkprogramma van de Nederlandse Sterrenkundigen aangeboden door vrienden en collega's aan Prof. dr. P.J. van Rhijn ter gelegenheid van zijn zeventigste verjaardag, 1956, Nederlandse Astronomen Club.
  • Sterrenkijken Bekeken; Sterrenkunde aan de Groningse Universiteit vanaf 1614, 1983, publication of the Groningen University Museum (eds. A. Blaauw, J.A. de Boer, E. Dekker and J. Schuller tot Peursum-Meijer).
  • The Legacy of J.C. Kapteyn; Studies on Kapteyn and the Development of Modern Astronomy, 2000, proceedings of a symposium on Kapteyn (eds. P.C. van der Kruit and K. van Berkel), published by Kluwer Academic Publishers (ISBN 978-3-319-10875-9).
  • Jacobus Cornelius Kapteyn: Born investigator of the Heavens, 2014, by Pieter C. van der Kruit, volume 416 in the Astrophysics and Space Science Library of Springer Publishers (ISBN 978-3-319-10875-9).
  • De Inrichting van de Hemel: Een biografie van astronoom Jacobus C. Kapteyn, 2016, by Pieter C. van der Kruit, Amsterdam University Press (ISBN 978-9-462-98042-6).
  • Pioneer of Galactic Astronomy: A Biography of Jacobus C. Kapteyn, 2020, by Pieter C. van der Kruit, Springer Biographies, Springer Publishers (ISBN 978-3-030-55422-4).
On the left you see the copy of the CPD that Kapteyn dedicated to his wife. Next to these the four volumes containing the reprints of Kapteyn's publications and the volumes III to VII of various hand-written tables.
On the left you see the copy of the CPD that Kapteyn dedicated to his wife. Next to these the four volumes containing the reprints of Kapteyn's publications and the volumes III to VII of various hand-written tables.
Last modified:22 July 2021 08.46 a.m.
printView this page in: Nederlands