John Stanley Plaskett

(1865-1941) J.S. Plaskett played a pivotal role in the establishment of astrophysical research in Canada and helped to confirm the rotation rate of the Milky Way. He was an active member of the Ottawa Centre between 1907 and 1918, acted as an Associate Editor of the Journal for 28 years, and Society President (1914-15).

JOHN STANLEY PLASKETT (1865-1941) spent a happy youth on the family farm near Woodstock. Ontario, and did mechanical and electrical work for a number of years before moving to Toronto. There he earned his B.A. in 1899 while employed as a mechanical assistant in the University of Toronto Physics Department. His name first appears in Society records as assisting Chant with lecture demonstrations. His astronomical career began in 1903 when he accepted a job in Ottawa superintending the installation of equipment at the Dominion Observatory then under construction. Plaskett went on to use the 38-cm refractor to obtain spectra of binaries. He soon faced the limitations of the equipment there and designed a new and faster spectrograph, but in the long run, he knew that a much larger telescope was needed to put Canada in the forefront of astrophysical research. His persistent lobbying of the federal authorities led eventually to the establishment of the DAO under his directorship.

Plaskett's discovery in 1922 of a binary system which had the greatest mass of any then known, attracted a lot of media attention but his pre-eminent work, carried out between 1928 and 1935 in collaboration with J.A. Pearce, confirmed the rotation rate of the Galaxy. For his outstanding work Plaskett received some of the most prestigious international awards that any astronomer can ever earn.

Plaskett was a kind and constant supporter of the RASC. Between 1907 and 1918, he held many offices in the Ottawa Centre and on the national Council, including the presidency at both levels. He contributed numerous papers to the Journal of which he was Associate Editor for twenty-eight years, and throughout his career he frequently spoke at Centre meetings, especially in later years in Victoria and in Winnipeg where he was Honorary President. One of his sons, Harry H. Plaskett, became Savilian Professor of Astronomy at Oxford University.

Further Reading

  • Obituary, JRASC (December 1941)
  • Plaskett Medal (includes a selection of Plaskett-related JRASC articles)
  • A Bibliography of the Published Papers of J. S. Plaskett, JRASC (December 1941)
  • JRASC articles by J.S. Plaskett
  • Book: The Dominion Astrophysical Observatory (1923)
  • a major monograph on J.S. Plaskett by R. Peter Broughton, titled Northern Star, is scheduled to appear within the next several years


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Plaskett, John S.