For his acclaimed studies of spectroscopic binary stars, his innovative instrument design and telescope construction, and his major contribution to the world’s understanding of the Milky Way, John Stanley Plaskett (1865-1941) is recognized as Canada’s father of modern astronomy.
 

John Stanley Plaskett (inset), born on a farm in southwestern Ontario two years before Canada became a nation, was nearly 40 years old when he began work at the Dominion Observatory in Ottawa. There, a fledgling astronomer, he first looked into the far reaches of the universe through a 15-inch telescope. [Photo, courtesy National Research Council/Dominion Astrophysical Observatory]

Born in Hickson, near Woodstock, Ontario, Plaskett left school at age 16 to run the family farm after his father died. Some years later, when circumstances permitted, he left to take employment as an apprentice mechanic with the Edison Electric Company at its plants in Schenectady, New York, and Sherbrooke, Quebec. By 1890, he had become a mechanic in the Physics Department at the University of Toronto, where, as a part-time student, encouraged by his wife, Rebecca, he earned a degree with first-class honours in Physics and Mathematics in 1899. He stayed on at Toronto for four years, lecturing and conducting research into colour photography.

In 1903, Plaskett was recruited by the Department of the Interior to oversee instrumental work at the new Dominion Observatory in Ottawa. Here, the budding astronomer quickly showed his outstanding ability. He was placed in charge of the 1905 solar eclipse expedition to Labrador and subsequently headed astrophysical research at the observatory. Using the 15-inch refractor telescope, Plaskett was responsible for the design and use of spectroscopes to measure the radial velocity of stars. His much-improved spectroscope afforded Plaskett an opportunity to make significant contributions to the study of binary (or twin) stars. However, it soon became apparent that he needed a much larger telescope to observe and record fainter, more distant stars, and he repeatedly pushed the Canadian parliament to support the funding of a suitable instrument.
 

Viewed with hat in hand, third from left, John S. Plaskett stands with colleagues and friends on June 11, 1918, at the official opening of the Dominion Astrophysical Laboratory. Plaskett mainly designed the 72-inch telescope, then the world’s largest, as well as supervised its construction on a hilltop near Victoria, British Columbia. [Photo, courtesy National Research Council/Dominion Astrophysical Observatory]

Finally granting approval in 1913 to build a 72-inch telescope, then the world’s largest, the government made Plaskett supervisor of its design and construction and eventually appointed him the first Director of the Dominion Astrophysical Observatory in Victoria, British Columbia, a position he held until his retirement in 1934.

Reaching further into the galaxy, Plaskett and his staff were able to expand their studies of stellar radial velocities and soon began finding new binaries. Some of these were also eclipsing systems permitting their sizes and masses to be found. Plaskett’s reputation as an internationally respected astronomer received a big boost in 1922 with his discovery of a massive binary star (previously regarded as a single star), which was, for many years, the heaviest on record.
 

John Plaskett, circa 1913, is viewed standing next to the 15-inch telescope at Ottawa’s Dominion Observatory. Realizing the need for a much larger instrument to explore the mysteries of the universe, he vigorously lobbied the federal government to fund the building of a new telescope. [Photo, courtesy City of Toronto Archives/James Collection/2209]

Using radial velocities from thousands of spectra, Plaskett and his colleague, J.A. Pearce, published in the 1930s the first detailed analysis of the rotation of the Milky Way, demonstrating that the sun is two-thirds out from the centre of our galaxy about which it revolves once in 220 million years. This important discovery went a long way towards recognizing that we are part of a vast spiral system like the galaxy in Andromeda. The extensive research of Plaskett and Pearce on the motion and distribution of interstellar matter also greatly contributed to the understanding of the motion and structure of our galaxy.

Dr. J.S. Plaskett received many honours, degrees, medals, and awards for his scientific work from several universities and learned societies in the United Kingdom, the United States, and Canada. His son, Harry H. Plaskett, became a renowned astronomer at Oxford University.
 

Line sketch of the 72-inch telescope. [Photo, courtesy National Research Council of Canada/Dominion Astrophysical Observatory]

Mike Beggs