Hogg, Helen Sawyer (1905-1993) was an American-born Canadian astronomer. She became known for her research on variable stars —stars whose light regularly varies in brightness because of their pulsating atmospheres. Hogg discovered more than 250 variable stars. She mainly studied variable stars in globular star clusters, which are ball-like groups of stars that surround the center of the Milky Way Galaxy. Her work included measuring the period of many of these stars. A variable star's period is the time its light takes to change from bright to dim and back to bright. This information, in certain cases, helps astronomers determine the distance of the star from the earth.
Helen Sawyer was born on Aug. 1. 1905, in Lowell, Massachusetts. She earned a bachelor's degree from Mount Holyoke College in 1926. She received a master's degree in 1928 and a Ph.D. degree in astronomy in 1931 from Radcliffe College.
In 1930, Sawyer married Frank Hogg, a Canadian astronomer, and added his last name to her own. The couple moved to Canada in 1931. They had three children. Frank Hogg died in 1951.
In 1935, Helen Sawyer Hogg held an assistantship at the David Dunlap Observatory of the University of Toronto. She was a research associate at the observatory from 1936 until her death in 1993. She also held a position at the university's department of astronomy at the same time. At the university, she reached the rank of professor in 1957 and was named professor emeritus in 1976.
Hogg's first edition of her major work, Catalogue of Variable Stars in Globular Clusters, was published in 1939. From 1951 to 1981, she wrote a weekly newspaper column, “The Stars,” in the Toronto Star. In 1957, Hogg became the first woman to serve as president of the Royal Astronomical Society of Canada.
In 1985, Hogg married Francis E. L. Priestley. He died in 1988. Hogg died of a heart attack on Jan. 28, 1993, in Richmond Hill, Ontario.