Womens History Month: Helen Battles Sawyer Hogg

Helen Battles Sawyer Hogg, CC (1 August 1905 – 28 January 1993) was an astronomer noted for pioneering research into globular clusters and variable stars. She was the first female president of several astronomical organizations and a notable woman of science in a time when many universities would not award scientific degrees to women. Her scientific advocacy and journalism included astronomy columns in the Toronto Star (“With the Stars”, 1951–81) and the Journal of the Royal Astronomical Society of Canada (“Out of Old Books”, 1946–65). She was considered a “great scientist and a gracious person” over a career of sixty years.

While completing her doctoral degree, Hogg taught astronomy at Mount Holyoke and at Smith College. After graduation she moved to Victoria, British Columbia, where she began research at the Dominion Astrophysical Observatory. Hogg began taking photos of variable stars with the 72-inch reflecting telescope, cataloguing the cyclical changes in the brightness of the variable stars. At the Dominion Astrophysical Observatory, Hogg found 132 new variable stars in the globular cluster Messier 2. Hogg published this groundbreaking work in astronomical catalogues that are still used today. Notably, Hogg accomplished all of this as a volunteer assistant to her husband, as the Dominion Astrophysical Observatory would not offer her a job.

In 1935 Hogg moved to the University of Toronto, after her husband had received a job offer to work at the David Dunlap Observatory. For her first year there, Hogg continued her work photographing globular clusters, amassing thousands of photographs which she used to identify many thousands of variable stars. She published Catalogue of 1116 Variable Stars in Globular Clusters in 1939, the first of three catalogues she completed, with a fourth in the works at the time of her death. In addition to her work on variable stars in globular clusters, Hogg used the period-luminosity relationship of Cepheid variable stars (discovered by Henrietta Swan Leavitt in 1908) to enhance the understanding of the Milky Way Galaxy’s age, size and structure.

During the late 1930s, Hogg became one of the first astronomers to travel and work around the world to advance her research, as the globular clusters she was observing were best seen from the southern hemisphere.

From 1939 to 1941, Hogg returned to America to serve as the president of the American Association of Variable Star Observers (1939–1941) and the acting chair of Mount Holyoke’s astronomy department (1940–1941). Upon returning to the David Dunlap Observatory, she took on teaching duties at the University of Toronto, largely as a result of male staff being away due to World War II. Retaining her position after the men returned from war, Hogg advanced to assistant professor in 1951, associate professor in 1955, full professor in 1957, and professor emerita in 1976 upon her retirement. Over her research career Hogg published more than 200 papers, and was a leading authority in astronomy

The Helen Sawyer Hogg Observatory

Helen Sawyer Hogg married husband and fellow astronomy student at Harvard Frank Scott Hogg in 1930, and the two moved to Victoria, British Columbia in 1931. She gave birth to the couple’s daughter Sally there in June 1932. Happily, Hogg found having a child was manageable, and she was able to continue her observation work by bringing her sleeping daughter with her to the observatory at night in a basket. The observatory’s director, Dr. J.S. Plaskett, also was supportive; he gave Helen Sawyer Hogg a research grant of $200, which she used to hire a full-time housekeeper for an entire year providing further support for her research work

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