Draper, Henry

Early astronomers also knew that stars seemed to have different colors, hut a system for classifying stars on the basis of color was not proposed until about 1872. That system was proposed hy the American astronomer Henry Draper (1836-82). Draper s system of classification was very important because a star s color is an indication of its second major property, its temperature. The hotter a star, the more likely its color is to be in the blue to white range. The cooler the star, the more likely it is to emit an orangish or reddish color. Draper died before he could complete his system of star classification. The project was completed between 1918 and 1924 by the American astronomer Annie Jump Cannon (1863-1941). 

One of her first assignments at Harvard was to pick up the work of Henry Draper, which had been largely abandoned since his death in 1882. Cannon was apparently the perfect choice for that assignment. She is said to have been able to process star data at a prodigious speed. On average, she classified 5,000 stars a month between 1911 and 1915. At peak speed, she was able to study and classify up to three stars per minute. Overall, Cannon classified 225,300 stars, cataloging them in a nine-volume work entitled The Henry Draper Catalogue. 

Draper G (1988) The development of international humanitarian law. In International dimensions of humanitarian law. UNESCO/Henri Dunant Institute/Martinus Nijhoff, Paris/Geneva/... 

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