Dugan, Raymond Smith
Born Montague, Massachusetts, USA, 30 May 1878
Died Philadelphia, Pennsylvania, USA, 31 August 1940
American astronomer Raymond Dugan is best remembered for his accurate light curves of eclipsing binaries, in which one star passes in front of the other and blocks its light. He was also the first to recognize that the details of such light curves could be analyzed to reveal the heating of one star by the other and to show that distortion of spherical stars into ellipsoids by the gravity of their companions was common.
The son of Jeremiah Welby and Mary Evelyn Smith, a descendant of Miles Standish, Dugan completed his bachelor’s degree at Amherst College in 1889. The following 3 years were spent at the Syrian Protestant College (now American University) in Beirut, Lebanon, where Dugan was an instructor in astronomy and mathematics and acting director of the observatory. He returned to Amherst for a master’s degree in 1902 and immediately left to pursue his doctorate at Heidelberg, where he studied under Maximilian Wolf . As an assistant at the Königstuhl Observatory, Dugan took part in the ongoing search for asteroids and discovered 18 minor planets. On receiving his Ph.D. in 1905, he was hired as an instructor in astronomy at Princeton University, where he stayed for the next 35 years. Appointed as an assistant professor in 1908, Dugan was promoted to professor 12 years later. Dugan married Annette Odiorne in 1909. They adopted two children.
While Dugan is probably best remembered as a coauthor with Henry Russell and John Quincy Stewart of the two-volume textbook Astronomyfirst published in 1926, he was instrumental in the development of precise determinations of light curves of eclipsing binaries. A contemporary noted that he had “the world’s most accurate photometric eyes.” Dugan’s approach was to make a thorough investigation of the entire light curve of a few stars rather than to get rough results for many objects. He used Princeton’s 23-in. telescope with a polarizing photometer for most of his work. Examples of Dugan’s procedure are found among his early studies of RT Persei. The light curve was based on 904 points, each the mean of 16 readings, for a total of some 14,500 measures. The direct methods for determining stellar separations, size, limb darkening, and brightness from light curves that would be developed by Zdenĕk Kopal and others did not yet exist. Thus, Dugan spent many hours in laborious computations that would now be called model fitting and done by computer.
Among Dugan’s discoveries was that the ellipticity of components, first recognized in the very close pair β Lyrae, was a general property of eclipsing variables and that the smaller, but hotter and brighter, component in many systems heated the side of the companion facing it, thus causing the “reflection” effect.
By 1937, Dugan had made over 300,000 settings while his students had made some 200,000 more. Dugan followed a few of his stars year by year as long as he was capable of observing. For many, he found slow changes in their periods.
Dugan was elected a member of the American Philosophical Society in 1931. From 1935 until his death, he served as chairman of the International Astronomical Union’s Commission on Variable Stars. From 1927 to 1937, Dugan was secretary of the American Astronomical Society and its vice president from 1936 to 1938.