Jan Hendrik Oort

Jan Hendrik Oort , 1900-1992, Dutch astronomer. He confirmed (1927) Bertil Lindblad's theory of the Milky Way galaxy's rotation. In the 1950s he and his colleagues used radio astronomical means to map the spiral-arm structure of the galaxy. Oort proposed (1950) that comets originate in a cloud of material (the Oort cloud ) orbiting the sun at great distance and that they are occasionally deflected into the inner solar system by gravitational perturbation from the passing of nearby stars.

Oort, Jan Hendrik (1900–92) Dutch astronomer. He carried out research on the structure and dynamics of stellar systems, especially our galaxy, whose rotation he confirmed in 1927. In 1950, he proposed the existence of what has come to be called the Oort cloud – a spherical region of space surrounding the Solar System in which comets are thought to reside.

Oort, JanHendrik (1900–1992)Dutchastronomer. He studied with J. C.Kapteyn, whose work on star streams he continued, finding an overall net motion of the Sun with respect to other stars. In 1927 he showed that high-velocity stars appeared to be rotating about the galactic centre, and went on to estimate the Sun's distance from the centre and also the Galaxy's diameter and mass. He also suggested that the Galaxy had missing mass. In the 1950s he and others (including B. J.Bok and H. van deHulst) used the 21-cm line of interstellar hydrogen to map the Galaxy, revealing its spiral structure. In 1950 he suggested that comets originate in a region now called the Oort Cloud.