Jan Oort

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Jan Hendrik Oort ( or ; 28 April 1900 – 5 November 1992) was a Dutch astronomer who made significant contributions to the understanding of the Milky Way and who was a pioneer in the field of radio astronomy. The New York Times called him "one of the century's foremost explorers of the universe"; the European Space Agency website describes him as "one of the greatest astronomers of the 20th century" and states that he "revolutionised astronomy through his ground-breaking discoveries." In 1955, Oort's name appeared in Life magazine's list of the 100 most famous living people. He has been described as "putting the Netherlands in the forefront of postwar astronomy". Oort determined that the Milky Way rotates and overturned the idea that the Sun was at its center. He also analyzed the vertical motions of stars near the Sun, using this data to estimate the local gravitational field. He calculated how much mass must be present to account for the stellar motions perpendicular to the Galactic...

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