Duncan, John Charles
Duncan, John Charles
(b Duncan’s Mill, near Knightstown, Indiana, 8 February 1882; d. Chula Vista, California, 10 September 1967)
Duncan’s chief contribution to astronomy was his photographic demonstration of expansion in the Crab nebula. He is perhaps better known, however, as the author of Astronomy, a standard college textbook for over thirty years, which was illustrated with many of his own excellent photographs of nebulae and galaxies.
The son of Daniel Davidson Duncan and his wife, Naomi Jessup, Duncan grew up in Indiana and taught at a country school there from 1901 to 1903 while an undergraduate at Indiana University in Bloomington. Between receiving his B.A. in 1905 and his M.A. in 1906, both from Indiana University, he was a fellow of Lowell Observatory in Flagstaff, Arizona. In 1907, following his marriage to Katharine Armington Bullard the previous year, he enrolled at the University of California, where he received a Ph.D. in 1909; his dissertation, on Cepheid variables, was written under the direction of William Wallace Campbell.
Returning to the East, he served as instructor in astronomy at Harvard University from 1909 to 1916, before becoming professor of astronomy and director of Whitin Observatory at Wellesley College. Upon his retirement from these posts in 1950—at the age of sixty-eight—he spent the next twelve years as visiting professor at the University of Arizona and visiting astronomer at Steward Observatory.
The Crab nebula, located in the constellation of Taurus, is still today a fruitful subject for investigation because of its association with the pulsar NP 0532; it is believed to be the remnant of a supernova observed in Japan and China in A.D. 1054. By comparing a photograph taken with the sixty-inch telescope at Mount Wilson in 1909 by George Willis Ritchey with one he took himself in 1921 with the same instrument, Duncan was able to demonstrate outward motions in the filaments of the Crab. He later confirmed these motions with another photograph taken in 1938, thus showing that it was indeed an expanding envelope such as has been observed around other novae.
Duncan also investigated comets, spectroscopic binary stars, and novae. His long-exposure photographs of nebulae and galaxies were taken during an appointment as astronomer at Mount Wilson in 1920 and during many subsequent summers spent there as a voluntary research assistant.
His dissertation was published as “The Orbits of the Cepheid Variables Y Sagittarii and RT Aurigae; with a Discussion of the Possible Causes of This Type of Stellar Variation,” in Lick Observatory Bulletin, 5 (1908–1910), 82–94. His work on the Crab nebula appeared as “Changes Observed in the Crab Nebula in Taurus,” in Proceedings of the National Academy of Sciences, 7 (1921), 179–180; and as “Second Report on the Expansion of the Crab Nebula,” in Astrophysical Journal, 89 (1939), 482–485.
Reproductions and descriptions of the best of Duncan’s photographs are contained in six papers: “Bright Nebulae and Star Clusters in Sagittarius and Scutum,” in Astrophysical Journal, 51 (1920), 4–12, with 4 plates; “Bright and Dark Nebulae near ζ Orionis, Photographed with the 100-inch Hooker Telescope,” ibid., 53 (1921), 392–396, with 2 plates; “Photographic Studies of Nebulae, Third Paper,” ibid., 57 (1923), 137–148, with 11 plates; “Photographic Studies of Nebulae, Fourth Paper,” ibid., 63 (1926), 122–126, with 4 plates; “Photographic Studies of Nebulae, Fifth Paper,” ibid, 86 (1937), 496–498, with 6 plates; and “Photographic Studies of Nebulae VI. The Great Nebulous Region in Cygnus Photographed in Red Light,” ibid., 109 (1949), 479, with 2 plates.
There are 38 articles by Duncan listed in Poggendorff, VI, pt. 1, 615, and VIIb, pt. 2, 1155–1156, which include all those mentioned above except the second.
II. Secondary Literature. Joseph Ashbrook’s brief, unsigned obituary notice, with photograph, appeared in Sky and Telescope, 34 (1967), 283. Other facts about Duncan’s life can be found in Who’s Who in America, XXVII (Chicago, 1952), 690–691, and XXVIII (Chicago, 1954),– 746; and in American Men of Science, 11th ed., The Physical and Biological Sciences, D-G (New York, 1965), 1313.
Sally H. Dieke