Jan Oort
Jan Oort

Celebrity Profile

Name: Jan Oort
Occupation: Astronomer
Gender: Male
Birth Day: April 28, 1900
Death Date: Nov 5, 1992 (age 92)
Age: Aged 92
Country: Netherlands
Zodiac Sign: Taurus

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Weight: in kg - N/A
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Jan Oort

Jan Oort was born on April 28, 1900 in Netherlands (92 years old). Jan Oort is an Astronomer, zodiac sign: Taurus. Find out Jan Oortnet worth 2020, salary 2020 detail bellow.


He was the 1966 recipient of the Vetlesen Prize and the 1987 winner of the Kyoto Prize.

Does Jan Oort Dead or Alive?

As per our current Database, Jan Oort died on Nov 5, 1992 (age 92).

Net Worth

Net Worth 2020


Salary 2020

Not known

Before Fame

After studying physics at Groningen University, he worked at both the Yale Observatory and Leiden University.

Biography Timeline


Oort was born in Franeker, a small town in the Dutch province of Friesland, on April 28, 1900. He was the second son of Abraham Hermanus Oort, a physician, who died on May 12, 1941, and Ruth Hannah Faber, who was the daughter of Jan Faber and Henrietta Sophia Susanna Schaaii, and who died on November 20, 1957. Both of his parents came from families of clergymen, with his paternal grandfather, a Protestant clergyman with liberal ideas, who "was one of the founders of the more liberal Church in Holland" and who "was one of the three people who made a new translation of the Bible into Dutch." The reference is to Henricus Oort (1836–1927), who was the grandson of a famous Rotterdam preacher and, through his mother, Dina Maria Blom, the grandson of theologian Abraham Hermanus Blom, a "pioneer of modern biblical research". Several of Oort's uncles were pastors, as was his maternal grandfather. "My mother kept up her interests in that, at least in the early years of her marriage", he recalled. "But my father was less interested in Church matters."


In 1903 Oort's parents moved to Oegstgeest, near Leiden, where his father took charge of the Endegeest Psychiatric Clinic. Oort's father, "was a medical director in a sanitorium for nervous illnesses. We lived in the director's house of the sanitorium, in a small forest which was very nice for the children, of course, to grow up in." Oort's younger brother, John, became a professor of plant diseases at the University of Wageningen. In addition to John, Oort had two younger sisters and an elder brother who died of diabetes when he was a student.


Oort attended primary school in Oegstgeest and secondary school in Leiden, and in 1917 went to Groningen University to study physics. He later said that he had become interested in science and astronomy during his high-school years, and conjectured that his interest was stimulated by reading Jules Verne. His one hesitation about studying pure science was the concern that it "might alienate one a bit from people in general", as a result of which "one might not develop the human factor sufficiently." But he overcame this concern and ended up discovering that his later academic positions, which involved considerable administrative responsibilities, afforded a good deal of opportunity for social contact.


After taking his final exam in 1921, Oort was appointed assistant at Groningen, but in September 1922, he went to the United States to do graduate work at Yale and to serve as an assistant to Frank Schlesinger of the Yale Observatory.


In 1924, Oort returned to the Netherlands to work at Leiden University, where he served as a research assistant, becoming Conservator in 1926, Lecturer in 1930, and Professor Extraordinary in 1935. In 1926, he received his doctorate from Groningen with a thesis on the properties of high-velocity stars. The next year, Swedish astronomer Bertil Lindblad proposed that the rate of rotation of stars in the outer part of the galaxy decreased with distance from the galactic core, and Oort, who later said that he believed it was his colleague Willem de Sitter who had first drawn his attention to Lindblad's work, realized that Lindblad was correct and that the truth of his proposition could be demonstrated observationally. Oort provided two formulae that described galactic rotation; the two constants that figured in these formulae are now known as "Oort's constants". Oort "argued that just as the outer planets appear to us to be overtaken and passed by the less distant ones in the solar system, so too with the stars if the Galaxy really rotated", according to the Oxford Dictionary of Scientists. He "was finally able to calculate, on the basis of the various stellar motions, that the Sun was some 30,000 light-years from the center of the Galaxy and took about 225 million years to complete its orbit. He also showed that stars lying in the outer regions of the galactic disk rotated more slowly than those nearer the center. The Galaxy does not therefore rotate as a uniform whole but exhibits what is known as 'differential rotation'."


In 1927, Oort married Johanna Maria (Mieke) Graadt van Roggen (1906–1993). They had met at a university celebration at Utrecht, where Oort's brother was studying biology at the time. Oort and his wife had two sons, Coenraad (Coen) and Abraham, and a daughter, Marijke. Abraham became a professor of climatology at Princeton University.


In 1934, Oort became assistant to the director of Leiden Observatory; the next year he became General Secretary of the International Astronomical Union (IAU), a post he held until 1948; in 1937 he was elected to the Royal Academy. In 1939, he spent half a year in the U.S., and became interested in the Crab Nebula, concluding in a paper, written with American astronomer Nicholas Mayall, that it was the result of a supernova explosion.


In 1940, the Nazis invaded the Netherlands. Soon after, they dismissed the Jewish professors from Leiden and other universities. "Among the professors who were dismissed", Oort later recalled, "was a very famous … professor of law by the name of Meyers. On the day when he got the letter from the authorities that he could no longer teach his classes, the dean of the faculty of law went into his class … and delivered a speech in which he started by saying, 'I won't talk about his dismissal and I shall leave the people who did this, below us, but will concentrate on the greatness of the man dismissed by our aggressors.'"


Before the war was over, he initiated, in collaboration with a student at Utrecht, Hendrik van de Hulst, a project that eventually succeeded, in 1951, in detecting the 21-centimeter radio emission from interstellar hydrogen spectral line at radio frequencies. Oort and his colleagues also made the first investigation of the central region of the Galaxy, and discovered that “the 21-centimeter radio emission passed unabsorbed through the gas clouds that had hidden the center from optical observation. They found a huge concentration of mass there, later identified as mainly stars, and also discovered that much of the gas in the region was moving rapidly outward away from the center.” In June 1945, after the end of the war, Oort returned to Leiden, took over as director of the Observatory, and became Full Professor of Astronomy. During this immediate postwar period, he led the Dutch group that built radio telescopes at Radio Kootwijk, Dwingeloo, and Westerbork and used the 21-centimeter line to map the Milky Way, including the large-scale spiral structure, the galactic center, and gas cloud motions. Oort was helped in this project by the Dutch telecommunications company, PTT, which, he later explained, “had under their care all the radar equipment that was left behind by the Germans on the coast of Holland. This radar equipment consisted in part of reflecting telescopes of 7 1/2 meter aperture.... Our radio astronomy was really started with the aid of one of these instruments… it was in Kootwijk that the first map of the Galaxy was made.” For a brief period, before the completion of the Jodrell Bank telescope, the Dwingeloo instrument was the largest of its kind on earth.

In 1951 Oort and his wife spent several months in Princeton and Pasadena, an interlude that led to a paper by Oort and Lyman Spitzer on the acceleration of interstellar clouds by O-type stars. He went on to study high-velocity clouds. Oort served as director of the Leiden Observatory until 1970. After his retirement, he wrote comprehensive articles on the galactic center and on superclusters and published several papers on the quasar absorption lines, supporting Yakov Zel’dovich's pancake model of the universe. He also continued researching the Milky Way and other galaxies and their distribution until shortly before his death at 92.


Oort went on to study comets, which he formulated a number of revolutionary hypotheses. He hypothesized that the Solar System is surrounded by a massive cloud consisting of billions of comets, many of them “long-period” comets that originate in a cloud far beyond the orbits of Neptune and Pluto. This cloud is now known as the Oort Cloud. He also realized that these external comets, from beyond Pluto, can “become trapped into tighter orbits by Jupiter, and become periodic comets, like Halley's comet.” According to one source, “Oort was one of the few people to have seen Comet Halley on two separate apparitions. At the age of 10, he was with his father on the shore at Noordwijk, Netherlands, when he first saw the comet. In 1986, 76 years later, he went up in a plane and was able to see the famous comet once more.”

Family Life

Jan's marriage to Johanna Maria Graadt van Roggen resulted in sons named Abraham and Coenraad and a daughter named Marijke.

🎂 Upcoming Birthday

Currently, Jan Oort is 121 years, 5 months and 20 days old. Jan Oort will celebrate 122nd birthday on a Thursday 28th of April 2022. Below we countdown to Jan Oort upcoming birthday.


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