Oort, Jan Hendrik (1900–1992)
Dutch astronomer who made major contributions to our knowledge of the structure
and rotation of the Milky Way Galaxy. More
or less as a sideline, Oort studied comets as well and provided evidence
for his theory, now widely accepted, that the Sun is surrounded by a distant
cloud of ice-rock objects that has become known as the Oort
Cloud. Oort studied stellar dynamics under Jacobus Kapteyn
at Groningen and worked at the University of Leiden from 1924 to 1992. In
1927 he confirmed Bertil Lindblad's hypothesis
of galactic rotation by analyzing motions of distant stars. During World
War II Oort started his compatriot Hendrik van
der Hulst on the successful search for the 21-cm
neutral hydrogen line and after the war led the Dutch group that used
the 21-cm line to map the layout of the Galaxy, including the large-scale
spiral structure, the galactic center, and gas cloud motions. In 1950, based
on his analysis of the well-measured orbits of 19 long-period
comets, Oort proposed the existence of a vast repository of frozen cometary
nuclei. He later showed that light from the Crab
Nebula is polarized, confirming
Iosif Shklovskii's suggestion that the
emission is largely due to synchrotron
radiation.
Adapted in part from the biographical
entry at The Bruce Medalists website
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