- Oort , Jan Hendrik
- (1900–1992) Dutch astronomerThe son of a physician from Franeker in the Netherlands, Oort (ohrt) was educated at the University of Gröningen where he worked under Jacobus Kapteyn and gained his PhD in 1926. After a short period at Yale University in America he was appointed to the staff of the University of Leiden where he was made professor of astronomy in 1935 and from 1945 to 1970 served as director of the Leiden Observatory. He also served as director of the Netherlands Radio Observatory.Oort's main interest was in the structure and dynamics of our Galaxy. In 1927 he succeeded in confirming the hypothesis of galactic rotation proposed by Bertil Lindblad. He 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. It should then be possible to observe distant stars appearing to lag behind and be overtaken by nearer ones. Extensive observation and statistical analysis of the results would thus not only establish the fact of galactic rotation but also allow something of the structure and mass of the Galaxy to be deduced.Oort 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’.Oort was also one of the earliest of the established astronomers to see the potential of the newly emerging discipline of the 1940s, radio astronomy. As one of the few scientists free to do pure research in the war years, he interested Hendrik van de Hulst in the work that finally led to the discovery in 1951 of the 21-centimeter radio emission from neutral interstellar hydrogen.By measuring the distribution of this radiation and thus of the gas clouds Oort and his Leiden colleagues lost little time in tracing the spiral structure of the galactic arms and made substantial improvements to the earlier work of William Morgan. They were also able to make the first investigation of the central region of the Galaxy: 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.Oort made major contributions to two other fields of astronomy. In 1950 he proposed that a huge swarm of comets surrounded the solar system at an immense distance and acted as a cometary reservoir. A comet could be perturbed out of this Oort cloud by a star and move into an orbit taking it toward the Sun. In 1956, working with Theodore Walraven, he studied the light emitted from the Crab nebula, a supernova remnant. The light was found to be very strongly polarized and must therefore be synchrotron radiation produced by electrons moving at very great speed in a magnetic field.
Scientists. Academic. 2011.
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Oort, Jan Hendrik — ▪ Dutch astronomer born April 28, 1900, Franeker, Neth. died Nov. 5, 1992, Leiden Dutch astronomer who was one of the most important figures in 20th century efforts to understand the nature of the Milky Way Galaxy. After studies at… … Universalium
OORT, Jan Hendrik — (1900–1992) Astronomer. Oort studied at GroningenUniversityunder Jacobus Kapteyn. During 1935–1970, he was professor of astronomy at the University of Leiden and, after 1945, director of the Leiden Observatory. Oort won world fame by his… … Historical Dictionary of the Netherlands
Jan Hendrik Oort — Jan Oort Pour les articles homonymes, voir Oort. Jan Hendrik Oort est un astronome néerlandais (28 avril 1900, Franeker 5 novembre 1992, Wassenaar). Il fut le directeur de l observatoire de Leyde de 1945 à 1970, il mena de… … Wikipédia en Français
Jan Hendrik Oort — Jan Oort Nacimiento 28 de Abril de 1900 Franeker, Friesland Fallecimiento 5 de noviembre de 1992 Leiden Nacionalidad Holandes Campo Astronomía … Wikipedia Español
Jan Hendrik Oort — Gedenktafel an Oorts Geburtshaus in Franeker Jan Hendrik Oort (* 28. April 1900 in Franeker; † 5. November 1992 in Leiden) war ein niederländischer Astronom. Leben Oort studierte an der Un … Deutsch Wikipedia
Jan Hendrick Oort — Jan Oort Pour les articles homonymes, voir Oort. Jan Hendrik Oort est un astronome néerlandais (28 avril 1900, Franeker 5 novembre 1992, Wassenaar). Il fut le directeur de l observatoire de Leyde de 1945 à 1970, il mena de… … Wikipédia en Français
Oort — Oort, Jan Hendrik, niederländischer Astronom, * Franeker 28. 4. 1900, ✝ Leiden 5. 11. 1992; 1945 70 Direktor des Observatoriums in Leiden und Professor ebenda, 1958 61 Präsident der Internationalen Astronomischen Union; bewies 1927, dass die… … Universal-Lexikon
Jan H. Oort — Gedenktafel an Oorts Geburtshaus in Franeker Jan Hendrik Oort (* 28. April 1900 in Franeker; † 5. November 1992 in Leiden) war ein niederländischer Astronom. Oort studierte an der Universität Groningen. Dort war er Schü … Deutsch Wikipedia
Jan Oort — Gedenktafel an Oorts Geburtshaus in Franeker Jan Hendrik Oort (* 28. April 1900 in Franeker; † 5. November 1992 in Leiden) war ein niederländischer Astronom. Oort studierte an der Universität Groningen. Dort war er Schü … Deutsch Wikipedia
Oort cloud — /awrt, ohrt/, Astron. a region of the solar system far beyond the orbit of Pluto in which billions of comets move in nearly circular orbits unless one is pulled into a highly eccentric elliptical orbit by a passing star. [1975 80; after Dutch… … Universalium