Helen Sawyer Hogg (1905-1993) was one of the few women working as a professional astronomer during the first half of the 20th century. Making a career out of studying the variable stars of global star clusters outlining the Milky Way Galaxy, Hogg photographed over 2,000 stars and published more than 200 papers. Although she was an American who studied at Harvard, she lived most of her life in Canada and spent most of her professional career working at the Dunlap Observatory in Toronto. Not only did Hogg have a strong reputation in academics, but she was also popular among the general public due to a weekly newspaper column she wrote to explain astronomical phenomena to lay people.
Helen Battles Sawyer Hogg was born on August 1, 1905 in Lowell, Massachusetts. Her father, Edward Everett Sawyer, was a banker and her mother, Carrie Myra (Sprague) Sawyer, was a teacher. As a child her parents strongly encouraged her to explore nature, including the stars. At the age of five she was allowed outdoors in the evening to witness the 1910 appearance of Halley's Comet. In a 1985 interview for the Graduate, the University of Toronto alumni magazine, Hogg recollected, "I don't remember much about the experience, but I can still visualize the thing with its lovely tail." She would become one of the few people to witness the comet twice when she saw it reappear again in 1986.
Hogg attended Lowell public schools as a child and then went to Mount Holyoke College to study chemistry in 1922. She changed her major, however, after a total eclipse of the sun on January 24, 1925. Hogg's astronomy professor, Anne Young, took her class to Connecticut to view the event, which proved to be a turning point in Hogg's academic career. A year later Hogg had the opportunity to meet astronomer Annie Cannon of the Harvard College Observatory. Cannon arranged for Hogg to attend graduate school at Harvard and work with Harlow Shapley, a renowned astronomer who specialized in global star clusters. Hogg graduated magna cum laude from Mount Holyoke in 1926 and then left for the Harvard Observatory.
Studied Global Star Clusters
Hogg was the first student of Shapley's to study global star clusters and she soon became an expert in the field. There are about 130 global clusters surrounding the Milky Way Galaxy. These clusters were the first stellar formations and each contains thousands of stars. Hogg specialized in the study of variable stars which change in size, temperature, and brightness. Information from such stars allow astronomers to calculate stellar distances which can then be used to estimate the size of the galaxy. Shapley's work in this area showed that the Milky Way was larger than previously thought and than the sun was not the center of the galaxy, which was a controversial assertion at that time.
Hogg graduated with a master's degree in 1928 and a doctorate in 1931 from Radcliffe College, since at that time Harvard did not award graduate degrees in science to women. She began teaching astronomy before she finished her graduate work. In 1927 Hogg worked as a lecturer at Smith College in Northampton, Massachusetts. and in 1930 she returned to her alma mater, Mount Holyoke, as a teacher.
In 1930 Hogg married Frank Hogg, a fellow astronomy student at Harvard who specialized in stellar spectrophotometry. Frank Hogg was from Ontario, Canada, and once they completed their graduate work the couple moved to Canada. While Frank Hogg obtained a research position at the Dominion Astrophysical Observatory in Victoria, British Columbia, Helen Hogg was not offered a position at the observatory despite her qualifications. One reason for this was that, during the Depression, it was not considered acceptable for a woman to be employed at a government service if her husband was already employed there. Fortunately, Hogg was able to pursue her research by working as a volunteer at the observatory. While women were discouraged from working in the observatory at night since the technical staff were all male, Hogg accompanied her husband while he worked and therefore gained access to the telescope and other equipment. At that time the telescope at the Dominion Observatory was the second largest in the world at 72 inches. While the Hoggs were in Victoria they had an infant daughter, Sarah, who often slept in the observatory while her parents worked.
In 1935 Frank Hogg took a job at the David Dunlap Observatory at the University of Toronto, which had a new telescope two inches larger than the one in Victoria. Helen Hogg continued to work for free until she was offered a position as a research assistant in 1936. As Hogg's professional career grew, so too did her family. In 1936 she gave birth to son David and in 1937 James was born. Hogg continued her professional activities even as she raised her three children.
Recognized as an Accomplished Astronomer
Hogg's work was painstaking and required much patience. Tracking a single star's cycle could take hundreds of days and if something interfered with the observations, such as clouds or a scheduling conflict, the astronomer had to wait a year to continue following the cycle. Hogg was able to incorporate her husband's knowledge of stellar spectrophotometry into her own work and produce extended time-exposure photographs of global clusters. This technique allowed her to discover 142 new variable stars. In 1939 Hogg published the first complete catalog of 1,116 variable stars.
During World War II Hogg was given increased responsibilities at the Dunlap Observatory since many men from the facility were called into military service. From 1940 to 1941 she was the acting chairperson of the Astronomy Department at Mount Holyoke and in 1941 she began teaching at the University of Toronto. In 1946 her husband became director of the observatory. In 1950 Hogg was awarded the prestigious Annie J. Cannon award from the American Astronomical Society for outstanding research by a woman astronomer.
On January 1, 1951, Frank Hogg died suddenly. Although Helen Hogg was left to care for their three children, she continued to forge her own career in astronomy. Her next major career move came in 1955-1956 when she became the program director of astronomy with the U.S. National Science Foundation. Then in 1957 she became full professor at the University of Toronto, a position which she held until 1976.
Introduced Astronomy to Lay People
In addition to her academic duties, Hogg took over a weekly column in the Toronto Star called "The Stars" that her husband had been writing until his death. Hogg used this forum to explain astronomical phenomenon to lay people. For example, in a 1975 article she explained the meaning of "a blue moon," which she said was most likely caused by certain types of dust particles that are slightly larger than a wavelength of light. These particles filter red light, but allow blue light to pass through, thereby creating the illusion of a blue moon. Hogg continued to write the popular column until 1981. Her effectiveness in writing for lay people led to her 1976 book The Stars Belong to Everyone: How to Enjoy Astronomy. In the foreword to the book she wrote, "Very little time is required to see and enjoy the beauties of the sky; once you come to know them, they never lose their appeal." For almost 30 years she also taught basic astronomy to non-science students.
Hogg retired from teaching in 1976 but continued to go to the observatory daily. During her long career she had taken thousands of pictures of global clusters and had published hundreds of scientific articles. As Christine Clement and Peter Broughton wrote in the Royal Astronomical Society of Canada Journal, Hogg's "knowledge of the sky was phenomenal. Even on cloudy nights when she was scheduled to observe at the David Dunlap Observatory, she always watched for breaks in the clouds just in case one of her 'clusters' might appear. She never missed an opportunity." Even when she was no longer able to climb the stairs to the telescope, Hogg continued to analyze and write about her photographs. She updated her first catalog of variable stars twice, in 1955 and 1973, and was working on another edition at the time of her death. In 1985 Hogg married F. E. L. Priestley, professor emeritus of English at the University of Toronto. Her passion for astronomy affected her new husband, too. He published two articles in the Royal Astronomical Society of Canada Journal in 1986 and 1987. However, her second marriage did not last long, for Priestley died in 1988.
Service and Legacy
Hogg was very humble about her career in astronomy. In 1985 she told the University of Toronto Graduate, "I don't think I've made that many earth-shaking discoveries. It's just a case of working and accumulating a lot of information in one area." Her colleagues, however, properly recognized her work. Throughout her lifetime Hogg received numerous professional awards for her contributions to astronomy. Aside from the prestigious Cannon Prize, Hogg also received the Rittenhouse Medal from the Rittenhouse Astronomical Society and the Service Award Medal from the Royal Astronomical Society of Canada, as well as six honorary degrees. She also served as a member as well as the president of many professional societies, including the Royal Astronomical Society of Canada. She also made many contributions as a pioneering woman in the field. She was the first woman president of the Royal Canadian Institute, the first woman president of the physical sciences section of the Royal Society of Canada, one of the first two women to serve as director of Bell Canada, and the founding president of the Canadian Astronomical Society. Just before her death she taped an interview for the University of Toronto to encourage young women to pursue careers in science. Hogg was also awarded honorary lifetime memberships to the Ontario Field Naturalists, the Royal Canadian Institute, the University Women's Club of Toronto, and Science North, Sudbury.
Hogg died of a heart attack in Richmond Hill, Ontario, on January 28, 1993, at the age of 87. Her contributions to astronomy have been recognized by the scientific community in many ways. In 1984 small planet 2917 which orbits between Jupiter and Mars was named Sawyer Hogg. In 1985 the Helen Sawyer Hogg lectureship was established by the Canadian Astronomical Society and the Royal Astronomical Society of Canada. Four years later the observatory a the National Museum of Science and Technology was named in her honor. In 1992 the University of Toronto named its telescope in Chile after Hogg. Her son David also pursued a career in astronomy, serving as a radio astronomer at the National Radio Astronomy Observatory and a life member of the Royal Astronomical Society of Canada.
Jarrell, Richard A., The Cold Light of Dawn: A History of Canadian Astronomy, University of Toronto Press, 1988.
Hogg, Helen Sawyer, The Stars Belong to Everyone: How to Enjoy Astronomy, Doubleday Canada Unlimited, 1976.
Royal Astronomical Society of Canada Journal, December 1993.
Toronto Star, December 3, 1985; October 1, 1989; June 20, 1992; January 29, 1993; February 7, 1993; October 24, 1993; June 9, 1996.
"Helen Sawyer Hogg: A Gift of Stars," http://www.sdsc.edu/ScienceWomen/hogg.html (October 22, 2001).
"Path of Heroes: Helen Sawyer Hogg," http://www.pch.gc.ca/poh-sdh-2000/english/routeeight/r8-hero4.html (October 22, 2001).
University of Toronto Astronomy Department Web site, http://www.astro.utoronto.ca/ (November 2, 2001).