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.