Dugan, Raymond Smith

(b. Montague, Massachusetts, 30 May 1878; d. Philadelphia, Pennsylvania, 31 August 1940)

astronomy.

Dugan devoted over half his life to the study of eclipsing variables—those pairs of stars which by chance have orbits almost edge on to us and therefore appear to vary in brightness because of repeated mutual eclipses. His prolonged and careful observations resulted in a wealth of information about many fundamental properties of stars. He also collaborated with Henry Norris Russell in writing one of the best elementary astronomy texts of this century.

His mother, Mary Evelyn Smith Dugan, was of Puritan stock, and his father, Jeremiah Welby Dugan, was but one generation removed from Ireland. After receiving a B.A. degree from Amherst College in 1899, Dugan went to Beirut (then Syria) to serve both as instructor in mathematics and astronomy and as acting director of the observatory in the Syrian Protestant College (now American University). Here he remained until 1902, when Amherst granted him an M.A. degree and he transferred to the University of Heidelberg to work and study for three years under Max Wolf. During this period he discovered eighteen asteroids, found two new variable stars, and earned a Ph.D. degree with a dissertation on the star cluster known as the Pleiades.

Having taken part in the Lick Observatory expedition to Alhama de Aragôn, Spain, for the solar eclipse of 30 August 1905, Dugan returned to the United States to become instructor in astronomy at Princeton University. In 1909 he married Annette Rumford Odiorne, and in 1920 he was named professor, which rank he held until death terminated his thirtyfive-year association with Princeton.

Endowed with what a contemporary referred to as “the world’s most accurate photometric eyes,” Dugan used Princeton’s twenty-three-inch telescope with a polarizing photometer to make long series of observations on a selected few eclipsing variables: for several of them this involved more than 18,000 individual settings. The resulting light curves, when analyzed according to methods developed in large part by his colleague Russell, revealed the relative sizes of the two stars, how far apart they were, their individual surface brightnesses, mutual tidally induced distortions into ellipsoids, and even how their densities varied from center to periphery. Dugan was the first to detect the so-called reflection effect, a brightening of the fainter member on the side facing its more luminous partner. He also found evidence that even widely separated pairs could be tidally distorted; furthermore he was able to explain some of the gradually lengthening periods of revolution that he observed as resulting from tidal evolution.

Dugan was elected a member of the American Philosophical Society in 1931 and served from 1935 until his death as chairman of the Commission on Variable Stars of the International Astronomical Union. He was also secretary of the American Astronomical Society from 1927 to 1936 and vice-president from 1936 to 1938.

BIBLIOGRAPHY

I. Original Works. The textbook referred to above was by Henry Norris Russell, Raymond Smith Dugan, and John Quincy Stewart, Astronomy, I. The Solar System (Boston, 1926; rev. ed., 1945), II. Astrophysics and Stellar Astronomy (Boston, 1927; repr. with supp. material, 1938).

Dugan’s discoveries of asteroids were reported in Astronomische Nachrichten, 160 (1902–1903), cols. 183,216; 161 (1903), col. 143; 162 (1903), cols. 15. III, 160; 163 (1903). cols. 255. 285, 379; 164 (1903–1904), cols. 15. 191,224; 165 (1904), cols. 110, 191; his discovery of two variable stars, ibid., col. 43. A shortened version of his dissertation also appeared in Astronomische Nachrichten, 166 (1904), 49–56; the full text, “Helligkeiten und mittlere Örter von 359 Sternen der Plejaden-Gruppe,” is in Publikationen des Astrophysikalischen Observatoriums Königstuhl-Heidelberg, 2 (1906). 29–55. His work on eclipsing variables, under the general title “Photometric Researches,” makes up (if four papers by his students are included) 17 of the 19 Contributions From the Princeton University Observatory that appeared between 1911 and 1940: details concerning equipment and observing techniques are in “The Algol System RT Persei,” in no. 1 (1911), 1–47, with a shortened version published in Monthly Notices of the Royal Astronomical Society, 75 (1915). 692–702; his first detection of the reflection effect is described in “The Algol System Z Draconis,” in no. 2 (1912), 1–44, with a shortened version in Monthly Notices of the Royal Astronomical Society, 75 (1915). 702–710; confirmation of the reflection effect and observation of ellipsoidal shapes in widely separated pairs appeared in “The Eclipsing Variables RV Ophiuchi and RZ Cassiopeiae,” in no. 4 (1916), 1–38, also covered in Astrophysical Journal, 43 (1916). 130–144, and 44 (1916), 117–123, and for RZ Cassiopeiae alone in Monthly Notices of the Royal Astronomical Society, 76 (1916), 729–739; his first evidence for a lengthening period, indicating tidal evolution, is in “The Eclipsing Variable U Cephei,” in no. 5 (1920), 1–34, with a shortened version in Astrophysical Journal, 52 (1920), 154–161; the first evidence for radial variation in density appeared in “The Eclipsing Variable Y Cygni,” in no. 12 (1931), 1–50; and his critical summary of the first twenty-nine years of his work at Princeton is in the introduction to “A Finding List for Observers of Eclipsing Variables,” in no. 15 (1934), 1–33.

For insight into the conditions under which Dugan worked (and a taste of his dry wit), see “The Old Princeton Observatory and the New,” in Popular Astronomy, 43 (1935), 146–151, repr. from Princeton Alumni Weekly (2 Oct. 1934).

The list of Dugan’s publications in Poggendorff, VI, 612, and VIIb, 1149–1150. is complete except for some early items (included above).

II. Secondary Literature. Obituary notices on Dugan by Henry Norris Russell appeared in Popular Astronomy, 48 (1940), 466–469; Science, n.s. 92 (1940), 231; and Yearbook of the American Philosophical Society (1940), 419–420. Other brief notices are listed in Poggendorff, VIIb (see above), Dugan’s entry in Who Was Who in America, I (Chicago, 1943) appears on p. 344.

Sally H. Dieke