WOLF, MAXIMILIAN FRANZ JOSEPH CORNELIUS

(b. Heidelberg, Germany, 21 June 1863; d. Heidelberg, 3 October 1932)

astronomy.

Wolf was the son of Franz Wolf and Elise Helwerth. He became interested in astronomy in his youth and in 1885 his father, a rich physician, constructed a private observatory for him. Wolf received the Ph. D. at Heidelberg in 1888, with a dissertation on celestial mechanics written under the direction of Leo Königsberger; he then went to Stockholm, where for the next two years he continued his studies with Gylden. His dissertation on asteroids, influenced by Gylden, was published in Stockholm, and won him a post as academic lecturer when he returned to the University of Heidelberg. He remained there for the rest of his life, and was professor of astrophysics and astronomy from 1901 until 1932.

Working in his private observatory, Wolf soon became famous for his innovative photographic methods. He used a wide-angle lens to investigate the diffuse nebulae of our galaxy and invented a technique for discovering asteroids through the streaks they made on time-exposure plates. These investigations brought him into contact with a number of American astronomers, especially E. E. Barnard. and in 1893 Wolf visited United States observatories. He returned with plans to build a new observatory at Heidelberg, since his own, located in the center of town, was inadequate; the grand duke of Baden was interested in Wolf’s idea, and under his patronage an observatory was begun on the Königstuhl. Catherine Wolfe Bruce, of New York City, who was also interested in Wolf’s work, made him the generous gift of the sixteen-inch double telescope that provided the foundation for his continuing investigations.

At the new Baden Observatory, Wolf and his collaborators discovered hundreds of new asteroids and determined their positions by means of a visual refractor–a method that produced more exact results than those derivable photographically from plates made with a wide-angle objective. From 1906 on, Wolf also used a reflector to obtain spectrographs of the galactic nebulae. He began by studying the shapes of the gaseous nebulae–as they were than called–but soon became interested in their relationships to surrounding stars. Observing that many of the extended dark nebulae show dark patches, or “cavities,” as he called them, Wolf counted the number of stars in such dark areas and demonstrated by the statistics of stellar magnitudes that the cavities were clouds of cosmic dust. Since it was possible for him to make spectrophotographs of only the brighter single stars, he made use of red filters on his reflector to view an extended celestial region.

As a result of these investigations Wolf was early able to recognize the difference between the gaseous and planetary nebulae, on the one hand, and the spiral nebulae, on the other. He reached this distinction through both spectral analysis and the study of the systematic distribution of the spiral nebulae relative to the mean plane of the galaxy. By 1911 he had offered a number of conclusions that were later generally adopted.

Wolf also studied single stars, comparing two plates of the same celestial region, photographed at different times, to find variable stars of substantial proper motion. In these investigations he often made use of the stereocomparator, an instrument that he and Pulfrich had invented. Wolf was of the view that, in general, the instrument creates the science, as could best be seen in the development of astronomy; throughout his career, he therefore paid particular attention to instrumentation. He further wished to establish an observatory in a more favorable climate than that of central Europe, and, with his friend A. F. Lindemann (the father of the British physicist Lord Cherwell), investigated sites around the Mediterranean–without, however, finding any more suitable.

Wolf was an exceptional teacher as well as researcher, and attracted students from all over the world, including Luigi Carnera, R. S. Dugan, August Kopff, and Heinrich Vogt. His lectures were vivid, and he often illustrated them with slides. In addition to his students, Wolf had friends all over the world, particularly in the United States; he was therefore much affected by World War I, and following the war was active in attempting to restore scientific relationships between America and Germany.

Wolf received many honors and awards. He was also highly esteemed by amateur astronomers, from whom he often received requests for celestial photographs. It is characteristic of his generosity that he was often able to oblige them, even though he prepared all copies and slides of his photographs himself.

BIBLIOGRAPHY

I. Original Works. Wolf’s works include “Photographic Observations of Minor Planets,” in Astronomy and Astrophysics, 12 (1893), 779; “Reflector and Portrait Lens in Celestial Photography,” in Nature, 55 (1897), 582; Königstuhlnebellisten, I–XVI (1902– 1928), “Stereoskopische Bestimmung der relativen Eigenbewegung von Fixsternen,” in Astronomische Nachrichten, 171 (1906), 321–326; “Spektren von Gsnebeln,” in Viertel jahrsschrift der Astronomischen Gesellschaft, 43 (1908), 208; “Die Spektra zweier planetarischer Nebel, Heidelberg,” in Sitzungsberichte der Akademie der Wissenschaften in Wien, pt. 2A (1911); “Auffindund und Messung von Eigenbewegungen durch Stereoeffekt,” in Vierteljahrsschrift der Astronomischen Gesellschaft, 51 (1916), 113; “Die Sternleeren beim Amerikanebel,” in Astronomische Nachrichten, 223 (1924), 89; and “Die Sternleeren bei S. Monocerotis,” in Seeliger-Festschrift (1924), 312.

II. Secondary Literature. On Wolf and his work, see H.-C. Freiesleben, Max Wolf, Der Bahnbrecher der Himmelsphotographie, Grosse Naturforscher, no. 26 (Stuttgart, 1962), which includes a comprehensive bibliograpby of Wolf’s publications, 232–238.

H.-Christ. Freiesleben