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. Oort chose Groningen partly because a well known astronomer,
Jacobus Cornelius Kapteyn, was teaching there, although Oort was unsure whether he wanted to specialize in physics or astronomy. After studying with Kapteyn, Oort decided on astronomy. "It was the personality of Professor Kapteyn which decided me entirely", he later recalled. "He was quite an inspiring teacher and especially his elementary astronomy lectures were fascinating." Oort began working on research with Kapteyn early in his third year. According to Oort one professor at Groningen who had considerable influence on his education was physicist
Frits Zernike. 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. ==Career==