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The following article was written expressly for the Crimson by Dr. Annie J. Cannon, Curator of Astronomical Photographs at the Harvard Observatory, where there is the largest and most valuable collection of astronomical photographs in the world. Dr. Cannon is recognized as the most eminent woman astronomer, and is the author of the Henry Draper Catalogue of Stellar Spectra, in which a quarter of a million stars are classified.
The Harvard Observatory
Some years ago, a Lehigh, University Professor told me this story concerning a Harvard graduate who was living in his home at that time and attending to the furnace. One day the Professor broached the subject of the Astronomical Observatory at Harvard. The young man looked puzzled and said, "Observatory? I don't know anything about such a place in Cambridge".
"What", exclaimed the Professor, "you never saw the famous Harvard Observatory, only a few blocks away from the College yard? You never heard of Professor Pickering, its distinguished Director these many years"?
"No", said the Harvard man, "in all my four years there, I never saw such a place nor ever heard of any name connected with it".
The Professor, wishing to mitigate a possible shock to my pride, said to me, "Never mind, I have just received a letter from my Harvard graduate, in which he writes,
"Please order a chord of wood for the furnice".
Nights Open to Students
With open nights now available to Harvard students, there can be no reason for lack of knowledge concerning your Observatory, or for failure to take advantage of the opportunity to look through one of its telescopes, or to see the great and unique collection of celestial photographs.
Nearly all astronomical investigations are now made by means of stellar photographs, of which there are 300,000 filed away in the stacks of the Harvard Observatory. Beginning as an experiment in 1850, when the first photograph of a star ever obtained was taken with the "incomparable" 15-inch telescope, starting anew in 1885 after the invention of the dry plate, the Harvard Collection of celestial photographs is the most complete in the whole world. Southern stars not visible in Cambridge were photographed in Arequipa, Peru, from 1891 to 1926, when the station was removed to Bloemfontein, South Africa.
Find New Galaxies
These photographs are mines of information concerning all portions of the sky, mines which have been only partially worked, and which still have rich veins awaiting the explorer. For instance a search is being made on Harvard plates for other galaxies than ours. These galaxies, far away from our own Milky Way system, are frequently of spiral shape, and can be readily detected by the careful observer. On photographs taken at Arequipa twenty-five years ago with the Bruce telescope, Miss Ames has found two thousand new galaxies.
By means of the Harvard photographs, certain comprehensive investigations have been undertaken here, which cannot at present be duplicated at any other Observatory. There is space to speak of two such problems; a survey of the whole sky for the discovery and study of variable stars, and for the classification of stars by means of their spectra.
Stars Are Inconstant
The Harvard photographs have proved to be the most prolific source for the discovery of variable stars, and also of the spectacular objects known as new stars or novae. Thus, 70 percent of the 7000 stars known to vary in brightness, and 67 percent of the 52 new stars which have flashed out since 1885, have been discovered at Harvard from observations of these photographs. And before 1885 few objects of either kind were known.
Professor Shapley, the Director of the Harvard Observatory, who has long University Theatre--"The Awakening" recognized the importance of the variable stars in the study of cosmogony, has laid out an ambitious program for their discovery and investigation. For this purpose, the Milky Way is divided into 240 fields, which are now being examined by a corps of observers, available through an appropriation from the Milton fund.
Perhaps the quickest and most successful way to discover variable or new stars is the simple method of superposing two glass photographs of the same celestial region, taken on different nights. One of the photographs should be negative, on which the stars are black, and the other a positive on which they are white.
Milky Way Yields Finds
By such methods, about a thousand new variable stars have already been found in these Milky Way regions, mainly by Misses Boyd, Mohr, Swope, and Woods. Nearly all of these variables are very faint, and are situated at great distances.
The determination by Miss Swope of the brightness and the period of variation of eighty-five of the variables discovered by her has enabled Dr. Shapley to locate more accurately the center or nucleus of our Galactic universe, 50,000 light years away. This center of our universe is in the Sagittarius-Scorpio region, the brightest part of the Milky Way, which is visible here in the summer sky but too low in the south to be seen in all its glory. In Arequipa, Peru, the region is overhead and is truly a remarkable sight in that transparent atmosphere.
Hardly any story of science has a more romantic appeal than that of the spectra of the stars.
By means of a prism placed over the object glass of the telescope, photographs of stellar spectra have been taken at Harvard for the last forty years. The light of any star of sufficient brightness in the field of view is spread out into a band, showing characteristics by which the spectra can be classified into various groups.
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