Jan Oort

Jan Hendrik Oort ForMemRS[1] (/ˈɔːrt/ or /ˈʊərt/;[2] 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.[3] The New York Times called him "one of the century's foremost explorers of the universe";[4] 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."[5] In 1955, Oort's name appeared in Life magazine's list of the 100 most famous living people.[6] He has been described as "putting the Netherlands in the forefront of postwar astronomy."[4]

Oort determined that the Milky Way rotates and overturned the idea that the Sun was at its center. He also postulated the existence of the mysterious invisible dark matter in 1932, which is believed to make up roughly 84.5% of the total matter in the Universe and whose gravitational pull causes "the clustering of stars into galaxies and galaxies into connecting strings of galaxies".[4][7] He discovered the galactic halo, a group of stars orbiting the Milky Way but outside the main disk.[8] Additionally Oort is responsible for a number of important insights about comets, including the realization that their orbits "implied there was a lot more solar system than the region occupied by the planets."[4]

The Oort cloud, the Oort constants, and the asteroid 1691 Oort were all named after him.

Early life and education
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,[9] 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"[10] and who "was one of the three people who made a new translation of the Bible into Dutch."[10] 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".[10] 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."[10]

Link..
https://en.wikipedia.org/wiki/Jan_Oort