Curtis, Heber Doust

(b. Muskegon, Michigan, 27 June 1872; d. Ann Arbor, Michigan, 9 January 1942)

astronomy.

Curtis was the son of cultivated but somewhat austere parents. While at Detroit High School he showed an aptitude for languages, and at the University of Michigan he devoted himself to Latin, Greek, and other ancient tongues. He studied some mathematics but little science and, apparently, no astronomy whatever.

Curtis obtained his A. B. in 1892 and his A. M. in 1893, then taught Latin at Detroit High School for six months before becoming professor of Latin and Greek at Napa College in California. At Napa his interest was aroused by a small Clark refracting telescope, and when the college merged at San Jose with the University (now College) of the Pacific, he had the use of a small observatory. In 1896 he transferred to the professorship of mathematics and astronomy.

In 1898 Curtis spent the summer vacation at Lick Observatory, where he was later to carry out his creative work. In 1900 he accepted a Vanderbilt fellowship at the University of Virginia, and he received his Ph.D. there in 1902 with the dissertation “The Definitive Orbit of Comet 1898 I.” Meanwhile, he went as a volunteer assistant on the Lick Observatory eclipse expedition to Thomaston, Georgia, in 1900 and on the U.S. Naval Observatory expedition to Solok, Sumatra, in 1901. He so impressed W. W. Campbell that he was invited to join the staff of Lick Observatory as soon as he completed his degree.

Curtis’ early years on the Lick staff were devoted mainly to continuing Campbell’s studies of the radial velocities of the brighter stars, first at Lick itself and, from 1906, at the station at Santiago, Chile. In 1910 he was recalled by Campbell to work on the program of nebular photography that J. E. Keeler had briefly pioneered at Lick from 1898 to his death in 1900. The outstanding problem of nebular research concerned the nature of the “white” nebulae whose spectrum of light was continuous in a manner consistent with their being large star systems, possible “island universes” comparable with our own star system, or galaxy. Two observational facts were of great weight against this view. First, the vast numbers of white nebulae were not distributed over the whole of the visible sky, as one would expect according to the “island universe” theory, but were concentrated toward the poles of the galaxy and avoided its plane; this “zone of avoidance” suggested that they were subsidiary to the galaxy and not systems of coordinate rank. Second, a bright new star, or nova, had been observed in the great nebula in Andromeda (M31) in 1885; and it had been estimated that, according to the “island universe” theory, this single nova would have to be equivalent in brightness to some 50,000,000 suns.

In the course of his decade of work on nebulae, Curtis steadily became more convinced of the truth of the “island universe” theory. His photographs of white nebulae seen edge-on often showed a dark band of obscuring matter in the plane of the nebula, and he reasoned that a similar band of obscuring matter in the plane of the galaxy would blot out the light of distant nebulae in the direction of the plane and so cause the optical effect of the zone of avoidance. In 1917 Curtis discovered on photographs of nebulae new stars much fainter than the nova of 1885, and the publication of similar discoveries by G. W. Ritchey and others convinced him that the nova of 1885 was exceptional in brightness and that the inferences drawn from it could not be relied upon.

Other evidence against the “island universe” theory was, however, arising from the comparisons by Adriaan van Maanen of photographs of nebulae taken years apart. The changes revealed in 1916 by his meticulous measurements indicated that the spiral nebula M 101 was rotating far too rapidly to be of a size comparable with our galaxy. Curtis himself was skeptical of van Maanen’s results, and his skepticism was to prove well-founded. Van Maanen’s colleague at Mount Wilson, the brilliant young Harlow Shapley, believed in the alleged rotations; and since Shapley had himself used daring new distance-measuring techniques to argue that the galaxy is far larger than had been thought, he became a leading opponent of the “island universe” theory. On 26 April 1920, Shapley and Curtis presented their contrasting positions before the National Academy of Sciences. The encounter aroused intense professional interest at the time, and Curtis’ effectiveness as a public speaker was held to have made his case the more persuasive.

In 1920 Curtis accepted an invitation to become director of Allegheny Observatory of the University of Pittsburgh, and the change marked the end of his major creative contributions to astronomy: his energies were taken up by teaching, administration, and the construction of new instruments. He was content that the main observing program should be a continuation of the stellar parallax investigations initiated by his predecessor. In 1930 Curtis became director of the observatory of the University of Michigan, where he had the promise of money to construct a great telescope. Unfortunately, this gift became a casualty of the depression; and although Curtis persevered in the raising of funds, the telescope was still unconstructed at his death.

BIBLIOGRAPHY

A complete professional bibliography is included in the memoir by Robert G. Aitken cited below. Curtis’ most important publications are “Descriptions of 762 Nebulae and Clusters Photographed With the Crossley Reflector,” in Publications of the Lick Observatory, 31 (1918), 1–42; and “The Nebulae,” in Handbunch der Astrophysik, V, pt. 2 (Berlin, 1933), 774–936.

On Curtis, see Robert G. Aitken, “Heber Doust Curtis 1872–1942,” in Biographical Memoirs. National Academy of Sciences, 22 (1943), 275–294.

Michael A. Hoskin