Hendrik Christoffel van de Hulst

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Hendrik C. van de Hulst, 1977

Hendrik Christoffel van de Hulst , called Henk, (born November 19, 1918 in Utrecht , † July 31, 2000 in Leiden ) was one of the most important Dutch astrophysicists of the past 150 years.

Live and act

Hendrik Christoffel van de Hulst was born on November 19, 1918 as the son of the school principal and children's book illustrator Willem Gerrit van de Hulst (1879–1963) and his wife Johanna Cornelia in Utrecht. He grew up in a Calvinist religious environment, believing in the teaching of the Reformed Dutch Church. Five other siblings lived in the family. He later described his family conditions as pleasant and happy. Only his health was bad during these years. While attending school at the high school in Utrecht in 1930, he showed that he had good qualifications for a university visit with a strong mathematical profile. His actual career aspiration at that time was to become an engineer or technician. He studied at the University of Utrecht , but it wasn't until his sophomore year that he decided to turn to astrophysics. This was particularly evident in the interesting lectures given by his lecturer Marcel Minnaert (1893–1970). Due to the German invasion of the Netherlands, Hendrik van de Hulst had to interrupt his studies in 1939. As a prisoner of war, Marcel Minnaert made him aware of a prize competition at the University of Leiden in 1941. The task here was to find explanations for the dust particles discovered 10 years ago in interstellar space. In April 1941, Hendrik van de Hulst submitted his application and the jury attested that he had "a mature scientific spirit". Because after the interruption of his studies he continued to deal with the topic of light scattering in an astronomical context.

When news arrived from the USA in 1944 that the American engineer and radio amateur Grote Reber (1911–2002) had investigated the discovery of Karl Jansky (1905–1950) and carried out further investigations into sources of interference that disrupt long-distance communication systems, he was there encountered strong emissions in the middle of the Milky Way galaxy. In 1944, Hulst theoretically calculated the 21 cm line (1420.4058 MHz) of interstellar neutral hydrogen and thus predicted its existence as the emission and absorption line of interstellar clouds of hydrogen. Following a suggestion by Jan Oort , with whom he was in Leiden for a few months in 1944, he then occupied himself with observations of the spectral line in the radio regime. At that time Oort was looking for explanations for the observations described by Grote Reber. The line is a special case of hyperfine structure . It comes about when the spin of the electron orbiting the hydrogen nucleus flips over . Van de Hulst reported on this at a meeting of the Dutch Astronomy Club (NAC) in April 1944. But it was not until 1951 that this radiation was detected independently by several radio observatories , first by Edward Mills Purcell . Afterwards van de Hulst led the Dutch team with Oort and Christian Alexander Muller (Lex Muller), which together with an Australian team mapped the interstellar clouds of the Milky Way and demonstrated their spiral arms. At the meeting of the NAC in the Leiden Observatory in April, the possibilities and perspectives of radio astronomy for the Netherlands were discussed based on these spectacular discoveries. In the following year, several groups - international observatories were also present - tried to check the prediction made by van de Hulst in astronomical practice. When the university was not yet able to work again after the end of the war, van de Hulst first tried to acquire knowledge through self-study. In 1946 he did his doctorate with Marcel Minnaert on the subject of "Optics of spherical particles".

In the same year he married Wilhelmine Mengerink, who also studied astronomy in Utrecht. After the wedding, she switched to psychology. The marriage resulted in two sons and two daughters.

After completing their doctorate, Hendrik van de Hulst and his wife left the Netherlands and started working in the USA. He received a postdoctoral fellowship at the Yerkes Observatory at the University of Chicago. He worked here for two years. During this time he made close contact with S. Chandesekhar, who later won the Nobel Prize, and Gerard Kuiper (1905–1973). This stimulated Hendrik van de Hulst's interest in continuing to work on solar system topics, which led to research on the dust of the zodiac signs. But Oort recommended that he return to the Netherlands. Here he began in 1948 as a lecturer at the University of Leiden. But in the following years he kept returning to the USA for longer periods. Then he worked at Harvard, Caltech and the Institute for Space Studies in New York. In 1951 the practical breakthrough of his theoretical assumption of 1944 was reached, when several observatories could actually detect this radiation independently of one another. First they were confirmed beyond any doubt by Harvard University, then by the Kootwijk Observatory (Netherlands).

In the following year 1952 van de Hulst became professor at the University of Leiden . In this position he wrote a book on the fundamentals of physics together with Cornelis Anthonie van Peursen (1920–1996). In doing so, they came to the conclusion that it is not possible to give a clear philosophical definition for physics as a science. This knowledge and the intensive preoccupation with phenomena of the natural sciences led him to distance himself more and more from his earlier religious views. Several scientific papers followed the monograph "Light Scattering by Small Particles", which he said was written primarily to "explain the light of the Milky Way". The international organization for peaceful exploration of the university, the COSPAR , was founded in 1958 by the ICSU, the union of the sciences . Because there were enormous concerns at the time that the competition between the US and the USSR, which had already begun, would lead to only the military aspects of space exploration in mind. Van de Hulst became its first director and influenced the work of the international bodies, which was ostensibly based on scientific ethics. A year later, the Committee for Space Research was founded, and in 1960 he was involved in founding ESRO - the first European space research organization. Van de Hulst was a member of the Dutch Academy of Sciences. In 1960 he was elected to the American Academy of Arts and Sciences and the American Philosophical Society , in 1977 to the National Academy of Sciences and in 1991 as a foreign member of the Royal Society . As a Dutchman, it was particularly important to him to help strengthen his country's position. In 1965 he won a group of young Delft engineers, formed and supported the group so that he could also make independent contributions to the Netherlands. As a result, a laboratory was built in Leiden in the early 1970s, which was primarily concerned with the scientific monitoring of interstellar scattering processes. In addition to his research in the field of radio astronomy, he was also able to make valuable contributions to the understanding of light scattering by small particles and in particular by interstellar dust, the solar corona and interstellar matter . In 1975 he was involved in the establishment of the European Space Agency (ESA) and in the establishment of the European Space Research and Technology Center (ESTEC) in Noordwijk .

After his retirement in 1984, he continued to pursue these activities. Shortly afterwards, the new institute SRON for the management and planning of space research was established under the auspices of the Dutch National Science Foundation. However, in the late 1990s, his health was causing him some problems. Hendrik van der Hulst suddenly lost weight; a medical examination resulted in the diagnosis of inoperable lung cancer. When the doctor who looked after him informed him that his death was imminent, he replied that at least then he would not have to worry about the problems of the turn of the century. Thanks to his stoic attitude, he managed to extend this threatening date into July of the following year. Van de Hulst died on July 21, 2000 in Leiden.

Awards and honors

The asteroid (2413) van de Hulst was named after him in 1987 (and the minor planet (2412) Wil after his wife in 1985 ).

Works

  • J. Mayo Greenberg, HC van de Hulst (Ed.): Interstellar dust and related topics . Reidel, Dordrecht 1973, ISBN 90-277-0396-5 .
  • Light scattering by small particles . Dover Publ., New York, Dover, 1981, ISBN 0-486-64228-3 .
  • Observation of the interstellar hydrogen line of wave length 21 cm made at Kootwijk, Netherlands, Astronomical Journal, Volume 56, 1951, p. 144
  • The galaxy explored by radio waves, The Observatory, Volume 73, 1953, pp. 129-139
  • Study of the 21 cm line and their interpretation, in HC van de Hulst (Ed.), Radio astronomy, Proc. of the 4th IAU Symposium, Cambridge University Press 1957, pp. 3-13

literature

  • Alan Cook: Hendrik Christoffel Van De Hulst Ridder In De Orde Van Nederlandse Leeuw. November 19, 1918 - July 31, 2000 . In: Biographical Memoirs of the Royal Society . tape 47 , 2001, p. 465-479 , doi : 10.1098 / rsbm.2001.0028 ( royalsocietypublishing.org ).
  • HC van de Hulst: Roaming Through Astrophysics, Ann. Rev. Astron. Astrophys, Volume 36, 1998, pp. 1-16

Web links

Individual evidence

  1. ↑ In Memoriam. Hendrik Christoffel van de Hulst, University of Leiden in: https.strw-leidenuniv.ni/vdhulst_e.html
  2. ↑ Published in 1945: HC van de Hulst, Radiostraling uit het wereldruim II: herkomst der radiogolven, Nederlands Tijdschrift voor Natuurkunde, Volume 11, 1945, pp. 210-221. English translation: Origin of the radio waves from outer space, in: Woodruff Turner Sullivan III: Classics in Radio Astronomy, Studies in the history of modern science 10, Dordrecht: Reidel 1982, pp. 302-316
  3. ^ Hugo van Woerden, Richard G. Strom, The beginnings of radio astronomy in the Netherlands, Journal of Astronomical History and Heritage, Volume 9, 2006, pp. 3-20
  4. ↑ Member History: Hendrik C. van de Hulst. American Philosophical Society, accessed October 6, 2018 .
  5. ^ Entry on Hulst, Hendrik Christoffel van de (1918 - 2000) in the archive of the Royal Society , London
personal data
SURNAME Hulst, Hendrik Christoffel van de
BRIEF DESCRIPTION Dutch astrophysicist
DATE OF BIRTH November 19, 1918
PLACE OF BIRTH Utrecht
DATE OF DEATH July 31, 2000
Place of death Suffer