His niche was in the cosmos, among the stars

Deep into the night sky, the twinkling of distant stars captures our attention. Imaginations marvel at the wonders of the solar system and the dramatic splash of the Milky Way. Except for surveying and location, Canada had little interest in astronomy. Building the country’s first large telescope in the late 1800s at the Dominion Observatory on Vancouver Island, B.C., John S. Plaskett opened minds to the magnificence of the heavens.

Placing a priority on family responsibilities when his father died, Plaskett, born Nov. 17, 1865, at Hickson near Woodstock, Ont., postponed his higher education. The oldest boy of several children, the 16-year-old spent the next five years helping to provide for his mother and siblings.

When able, Plaskett “apprenticed to the Edison Electric Company at Schenectady (and) he gained valuable engineering experience with the Canadian Edison Company at Sherbrooke,” his obituary by F.J.M. Stratton in the science journal Nature, Vol. 148, 1941, said. Adept with instrumentation, Plaskett was hired in 1890 by University of Toronto as a physics department assistant. Five years later, he enrolled in math and physics courses, earning a bachelor of arts in 1899 when he was 33 years old.

Hired by University of Toronto to lecture in physics, Plaskett also took up photography and became skilled in camera techniques. In 1903, “his engineering knowledge and experience together with his proved powers of research in photography and spectroscopy led to his appointment to the astronomical branch of the Department of the Interior at Ottawa,” Stratton noted. (A spectroscope splits white light into its component colours like a prism, according to Hubblesite.org, allowing analysis of the light’s properties, such as oxygen, iron, nitrogen or carbon.)

Plaskett had found his niche: It was in the cosmos, among the stars.

Excelling in his new job at the Dominion Observatory, the scientist spent several years setting up the facility, organizing research programs and installing new instruments. Plaskett created spectrographic equipment with particular notice to “lens design and the effect of the use of a relatively wide slit and of relatively small spectrum dispersion on the accuracy of radial velocity determinations,” according to William Bowyer in “Obituary: J.S. Plaskett,” The Observatory Journal, Vol. 64, 1942.

The observatory had the largest telescope in Canada at the time, with a 15-inch refractor (a 38-centimetre lens). Plaskett’s astrophysical pursuits required a much larger telescope, and in 1910 he put in the request to his boss and fellow astronomer, observatory director William Frederick King.

“King was enthusiastic about the idea, and the two astronomers began pressuring the Canadian government to make it a reality,” said “Canada Under the Stars”. Three years later, funding was approved for the telescope … plus another applauded advancement. “Plaskett worked for the next five years on the design of a 1.83-metre telescope — the biggest in the world — for the new Dominion Astrophysical Observatory to be built in Victoria, B.C.”

Constructing the new refractor, Plaskett’s instrumentation and optical experience proved useful again. He planned “an instrument of advanced design with electric drives, self-aligning ball bearings for both axes, and an improved universal spectrograph,” described R.A. Jarrell in “The Birth of Canadian Physics: J.S. Plaskett at the Dominion Observatory” (The Journal of the Royal Astronomical Society of Canada, June 1977).

Director King died suddenly, and the soon-to-be successor, Otto Julius Klotz, was a rival of Plaskett. The surveyor and astronomer was not interested in the lofty direction of Plaskett’s investigations.

“Plaskett naturally feared the appointment of Klotz, who had no sympathy for astrophysical research,” Jarrell said, and there was a possibility that the new observatory would be attached to the Ottawa location and out of Plaskett’s control. After much petitioning and finding allies, “Plaskett was given relative autonomy at Victoria.” However, Klotz and Plaskett remained at odds.

Opening in 1918 on Little Saanich Mountain, the brand new observatory’s mission “concentrated on stellar spectroscopy, especially radial velocity determinations, carrying on at a high standard essentially the same work which Plaskett had so ably started and supervised at Ottawa,” Bowyer described. The astronomer’s own intensity on O type and B type stars resulted in “extremely important confirmation for the theory of galactic rotation and also threw much light on the nature of the interstellar calcium.”

Gathering astronomical data, recording discoveries and building advanced equipment, Plaskett and his oldest son Harry (born in 1893 in Toronto) must have squealed and danced with excitement in December 1921. As the scientists scanned the Milky Way, a pair of stars came into view, performing a circling dance around a central mass.

“Taking over 40 spectra, Plaskett estimated that the pair were 140 times the mass of the sun or more, 27,000 times brighter, and orbited each other in 14.5 days, making it the most massive star known to man,” described “Centre of the Universe.” About 6,600 light-years away, Plaskett’s Star is located near the Monoceros Constellation; it is also recorded as HR 2422 and V640 Monocerotis.

Reported widely in newspapers, Plaskett’s discovery sparked the imaginations of amateur stargazers. The find was a blue giant, meaning the hottest among stars with temperatures over 30,000 Kelvin.

Another of Plaskett’s remarkable discoveries, with colleague J.A. Pearce, was the rotation of the Milky Way galaxy. “Using the Victoria telescope,” Centre of the Universe said, “they discovered that the galaxy rotates once every 240 million years, and that our solar system lies well away from the galactic centre.”

Promoting astrophysical science, Plaskett loved to give lectures on the subject and encouraged public appreciation of astronomy. The scientist received several honorary doctorates for his pioneering work — travelling to share his vast knowledge, Plaskett attended meetings and participated in committees of the International Astronomical Union.

A high-level member of both the Royal Astronomical Society and Royal Astronomical Society of Canada, Plaskett wrote many articles for the RASC journal — he was an associate editor with the publication for 28 years, as well. Awards and medals from science and astronomical societies flowed in for the groundbreaking scientist. On retiring in 1935, Plaskett was honoured with the prestigious Commander of the Order of the British Empire.

The inspirational Plaskett died six years later in Esquimalt, B.C., on Oct. 17, 1941. He was survived by his wife of nearly 50 years, Rebecca Hope Hemley, and their two sons. Enjoying the company and full support of his wife during his career, Plaskett was regarded as a loving husband and father with a sense of humour and an interest in people. While there are few details on youngest son Stuart Stanley Plaskett, their oldest son joined his father in cosmos science, astronomer Harry Hemley Plaskett.

Among other commemorations, the Canadian Astronomical Society and Royal Astronomical Society of Canada join each year to present the Plaskett Medal to “the PhD graduate from a Canadian university who is judged to have submitted the most outstanding doctoral thesis in astronomy or astrophysics within the last two calendar years.” In 2019, University of Alberta’s grad Alexandra Tetarenko received the gold medal for her thesis on “the physics of relativistic jets in X-ray binaries, as revealed by radio, millimeter (mm) and sub-millimeter (sub-mm) observations.” (Ouch, my brain hurts.)

Astrophysicist J.S. Plaskett must have been imbued with the strength of Atlas — the many who followed stand on the broad shoulders of this superman of Canadian science.

Susanna McLeod is a writer living in Kingston.

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