Celsius, Anders (än`dərs sĕl`sēŭs), 1701–44, Swedish astronomer. While professor of astronomy at the Univ. of Uppsala (1730–44), he traveled through Germany, France, and Italy, visiting great observatories. At Nuremberg in 1733 he published a collection of 316 observations of the aurora borealis made by himself and others. While in Paris he was instrumental in bringing about an expedition (of which he became a member) organized by the French Academy for the measurement of an arc of the meridian in Lapland (1736). He supervised the building of an observatory at Uppsala in 1740 and became its director; while there he pioneered in the measuring of the magnitude of stars, using photometric methods. In 1742 he invented the centigrade (or Celsius) thermometer. His works include De observationibus pro figura telluris determinanda (1738).