Early Scientific Discoveries

The observatory was instrumental in some important early scientific discoveries. One of these involved Plaskett’s work with taking spectra of stars, which involves photographing these spectra for further study.

Splitting the light of stars into a rainbow, or spectrum, reveals dark lines. These occur because chemical elements in the atmosphere of the star absorb light. As a star moves towards or away from us, the dark lines in the spectrum shift, and the faster it moves, the more the dark lines shift.

Plaskett designed the new telescope to be very efficient at taking  spectra, and he and his colleagues used it to gather measurements of the motions of many stars. These motions can tell us about how stars are distributed in space. This approach can also be used to discover stars that orbit each other, commonly referred to as binary stars.

Animated image showing the motion of a binary star system and the resulting velocities and shift of the spectral lines. On the left, there are two views of the system, one looking down and one looking edge-on. The same technique is used to discover planets around other stars. The motion of a planet will cause a slight variability in the velocity of the star. The top image on the right shows the range in velocity for a planet-star system.

The Victoria telescope captured its very first spectrum of a star on May 6, 1918, pictured below. The spectrum was taken on a small piece of glass coated with a material sensitive to light. After being exposed to starlight, the glass “plate” was developed in a chemical bath. The result is a negative image: when more light hits the plate, the image gets darker. The spectrum of the star appears as a dark streak in the middle. It is shown surrounded on either side with spectra created in a laboratory with well-known chemical elements. These allowed the spectrum of the star to be measured accurately.

The ‘plate envelope’ in which the photographic glass plate with the stellar spectrum is stored

An image of the very first spectrum taken by the telescope. The spectrum of the star is the thick line in between the sparse lines of the reference spectrum. The lines of the reference spectrum have well-known wavelengths and allow the lines in the stellar spectrum to be measured accurately.

Plaskett sent monthly reports to Ottawa on the operation of the observatory. The reports always recorded the number of spectra taken during the month to show how well the telescope was working. In the report of April 1922, Plaskett wrote that the telescope had made possible his “discovery and announcement of the most massive star known.” The name given to this star was “Plaskett’s Star” after its discoverer.

Reports on this discovery appeared in newspapers across the world. The discovery brought attention to Plaskett, Victoria, and Canada as a whole. Articles described Plaskett as “the most distinguished astronomer in Canada.” The farmer’s son was now one of the most noted astronomers in the world.

A July, 1922 newspaper article from Australia on the discovery of Plaskett’s Star. This is one example of how this discovery was overed world-wide.

Plaskett’s Star is actually a binary star system, which is two stars that orbit each other. The stars orbit each other every 14 days at a speed of 300 km/sec. Plaskett’s Star was long thought to be the most massive known binary system. However, work in this century has revealed that the Eta Carinae binary system is larger.

The observatory continued its work on measuring velocities and identifying binary star systems. Twelve years after the observatory opened, it had established itself as the world leader in binary star observations. In January 1930, Plaskett reported that “of the 900 known binaries, 400 have been discovered here.”

Plaskett’s work received more and more attention from astronomers around the world. In 1930 he received the Rumford Medal given by the American Academy of Arts and Sciencesfor his distinguished work in astronomy. He is the only individual Canadian to have won this prestigious award.

A July,2930 newspaper article that covers Plaskett’s return to Victoria after a 3-month trip to Europe and the US. During this trip Plaskett received two prestigious awards recognizing his contributions to astronomy during his career to that point. At this point he was working on what would be his greatest achievement.

Plaskett also used the observatory’s telescope to study the material between the stars. Astronomers had known about this interstellar material for several years, but Plaskett was the first to show that the material is distributed throughout the Milky Way. This knowledge would play a crucial role in the observatory’s greatest discovery.