Section 5.--the Work of the Telescope

Prevalent Misconceptions

The general idea of an astronomer’s work, as gathered from the questions and remarks of visitors, is that he sits at the eyepiece of the telescope sweeping the heavens in a search for new planets, comets or stars. The absolute futility of such a use of the telescope is evident when it is realized that the main field of the 72-inch covers only about one hundred-millionth of the sky and if only five seconds was required to examine each field it would take more than a lifetime to go over the whole sky once. A second misconception is the idea that large telescopes are used for visual observations of the planets with special reference to their habitability. No work is being attempted at this or other large observatories on planetary detail for which about an 18-inch refractor gives the best results and such a large telescope as the 72-inch is quite unsuited. All scientific observations with the 72-inch are made photographically and it is only arranged for visual use on Saturday evenings when for two hours visitors are allowed to observe the heavenly bodies. A third misconception is that the astronomer only works at night. However true this idea may have been in the days of visual observations when the measurements were made at the eyepiece, there is certainly now, when photography is so generally applied, more day than night work in astronomy. Besides the advantages of permanency, accuracy of measurement and power of recording objects beyond the range of the keenest eyesight, the photographic method has the further great advantage that an hour’s exposure may give sufficient material for several days’ measurement and discussion.

Spectroscopic Work

As already indicated most of the work with the 72-inch telescope is spectroscopic, but as also indicated modern spectroscopic investigations cover so wide a range of research that the actual work of the observatory is very varied. By aid of suitable spectrographs attached to a large telescope we can measure the speed of the stars towards or from us, their radial velocity as it is termed. We can discover double stars too close ever to be seen double in any telescope and we can determine the manner in which they revolve around one another and their distance apart and mass. From the spectra of the stars we can determine their absolute brightness as compared with the sun and their parallax or distance. The chemical elements present in the outer atmospheres of the stars can be determined and the pressure in these atmospheres. The measurement of temperatures and other physical conditions in the stars by means of the spectroscope is now an accomplished fact and one of the most recent developments of the spectroscopic work here has been to provide evidence of the truth of a theory of atomic structure and to show that the atomic constants in the enormous furnaces of the stars are the same as on the earth. Such a catalogue of information, obtained from an investigation of the mere quality of the light from stars so faint as to be quite invisible to the unaided eye and so distant that it may take thousands of years to travel to us, is sufficiently comprehensive to be treated in more detail.

Radial Velocities

When the 72-inch telescope was in course of design and construction, one of the greatest needs in astronomical work was increased data in regard to the radial velocities of the stars. Although the telescope was so designed as to be suitable for all kinds of observational work, special attention was devoted to the spectroscopic end. After consultation with the most prominent astronomers an observing programme of about 800 stars whose “proper” or cross motions across the sky were accurately known but whose radial velocities had not been determined, was prepared and spectroscopic observations of the stars on this programme were commenced as soon as the telescope was completed in May 1918. After slightly over three years’ work, observation and measurement were completed and Vol. II, No. 1 of the observatory publications, “The Radial Velocities of 594 Stars,” was published early in 1922. As hitherto the radial velocities of only about 2,000 stars had been obtained, this work was a considerable addition to existing data about the motions of the stars and will be of great use in extending our knowledge of the structure and motions of the universe. A second programme of 1,500 stars has been prepared but owing to other intervening observational work, not much has yet been done on this new programme.

One of the auxiliary programmes undertaken and nearly completed since the first programme is the determination of the radial velocities of a very interesting but limited class of stars, the highest temperature stars known, the O-type stars. The radial velocities and other interesting data about 50 of these stars have been completed.

Spectroscopic Double Stars

In the measurement of the radial velocity of the 800 stars on the first programme it was found that in about 180 stars successive plates did not give constant velocities, the stars at one time approaching at another receding from us. This phenomenon is practically certain proof that we are measuring the velocity of a star revolving around an invisible companion and such stars are generally called spectroscopic binaries to distinguish them from visual binaries which can be seen double in the telescope. Over 200 spectroscopic binaries have been discovered at this observatory as compared with about 700 discovered elsewhere, again a considerable addition. In about 20 of these binaries, observations were continued until the period of revolution, the form of the orbit, the separation of the two stars and in some cases, their masses were determined. In a particular class of spectroscopic binaries, the eclipsing variables, which allow from the combination of spectroscopic and photometric measurements the absolute dimensions to be obtained, we were able to determine the separation of the two stars, their diameters, densities, masses and brightnesses and the probable distances. Such complete information has been obtained here about seven systems, while only seven other systems have been determined elsewhere.

Absolute Magnitude and Distance

A new application of spectroscopic methods is to the determination of the total brightness of the stars as compared with the sun and their distance or “spectroscopic parallax” as it is called. This depends not on the positions but on the relative intensity or strength of the lines in the spectra of the stars and has only been developed in the last three or four years. The absolute magnitude and spectroscopic parallax of about 800 stars is now nearly completed and will soon be published while as a side line the radial velocities of 125 more stars have been determined.

Physical Conditions in the Stars

The spectrographs have also been used by one member of the staff in the determination of the physical and chemical conditions in stellar atmospheres, a new and difficult problem but one which promises not only very valuable additions to our knowledge of the constitution of the stars but may also lead to economic applications of the greatest importance. A new method depending upon the use of a wedge of dark glass has been applied to determining the distribution of energy in the different parts of the spectrum of the stars and to measuring their temperatures, while an application of the same methods to individual lines may lead to a great increase in our knowledge of conditions in the stars. A special investigation of three of the high temperature O-type stars referred to above has proved the existence in the spectra of these stars of lines predicted as present from purely theoretical conditions but never previously identified and has thus remarkably verified a theory of the structure of the atom. The measurement of the wave lengths of these hitherto unknown lines has led to an important independent determination of the fundamental constants of atomic structure and the dimensions of the atom and has shown that these constants and dimensions are the same in the tremendous furnaces of the stars as in our terrestrial laboratories, a verification of the homogeneity of matter and the uniformity of physical laws throughout the universe. Further interesting results from this investigation are the application of a new theory of ionization with the probable relative abundance of the elements to an independent determination of the temperature of these stars.

Other Investigations

Direct photographs have been made of some nebulae and clusters but this work is not being definitely followed at present. Investigations into the phenomena accompanying some short period binaries have been made and into the behaviour of the two strong calcium lines H and K in the spectra of the high temperature stars from which interesting and valuable results are expected. Since the observatory commenced work two bright novae or new stars have appeared, which have been fully observed spectroscopically here and the results discussed. The plates of the nova in Aquila have been loaned to the observatory at the University of Cambridge, England, for fuller discussion and analysis.

Value of Astronomical Work

This brief sketch of the work of the observatory naturally leads to the question frequently asked of astronomers:--What use is the work done at observatories and what practical value can a knowledge of the stars have in everyday life? While astronomy has obvious practical applications to navigation and surveying yet nine-tenths of modern astronomical research is devoted to the more or less abstract question of the constitution and motion of the stars and the structure of the universe. Indeed most physical and chemical as well as astronomical research is undertaken for the purpose of increasing our knowledge and of investigating the secrets and laws of nature and has generally no direct practical economic application. But it is now generally recognized by the layman as well as the scientist that without abstract there can be no applied science and that all the great economic and industrial applications of science have had to be preceded by the abstract and apparently non-practical investigations of pure science. The Great War perhaps made more evident than ever before the absolute dependence of applied science upon the unselfish and abstract work of pure science.

Economic Value

In view of past experience in science it would hence be a rash prediction to assert that the investigation of the conditions in distant stars can have no practical application upon earth. It may be of interest to point out one possible application of astrophysical research.

It is generally agreed that one of the most important economic problems of the not far distant future will be the provision of sources of energy to replace our rapidly depleting supplies of coal and oil. It appears now that the most probable solution of this problem will consist in the development of some method for utilizing the inexhaustible stores of energy contained in the atoms of matter. Modern research on conditions in the stars has made it practically certain that the enormous supply of energy, which has been radiated into space for aeons of time from these bodies, can only be maintained undiminished by the energy released by the transformation of atoms in the interior of the stars, where conditions of temperature and pressure prevail at present unattainable in terrestrial laboratories. The most hopeful line of attack upon this tremendously important economic problem hence seems to lie in the systematic astrophysical investigation of conditions in the stars supplemented by physical and chemical researches on the structure of the atom.

Ethical Value

While astronomers and scientific men generally fully realize the value of the practical applications of science, their main purpose is the search for truth and the extension of our knowledge of nature. While it is possible that investigation of the stars may have immense economic value, it is certain that it has tremendous ethical value giving us a clearer knowledge of the laws of nature and of our relations to the wonders of creation. Astronomy is the oldest and in many respects the most important of the sciences and its study, through the ages has been one of the most elevating influences on human character. Poincaré has well said that if the earth had been so continuously covered with clouds that the heavenly bodies could not be seen, mankind would still be in a primitive state and under the domain of superstition. The main superiority of modern over ancient civilization does not consist in the greater abundance of the necessities and luxuries of life, although this is undoubtedly due primarily to scientific research, but to the elevating influences of the truer conceptions of nature made possible by the abstract study of astronomy and other sciences.

It has been truly said that the degree of civilization of a country may be judged by the support it gives to the study of astronomy. By the establishment and maintenance of the Dominion Observatory at Ottawa and of the Dominion Astrophysical Observatory at Victoria with the second largest telescope in the world, Canada has a just claim on this criterion to the favourable estimation of the scientific world.

VICTORIA, B.C., May, 1923.

TRANSCRIBER’S NOTES:

Italicized text is surrounded by underscores: italics.

Obvious typographical errors have been corrected.