## Seeliger, Hugo von

## Seeliger, Hugo von

# SEELIGER, HUGO VON

(*b*. Biala, near Bielitz, Austrian Silesia [now Bielsko Biala, Poland], 23 September 1849; *d*, Munich, Germany,2 December 1924)

*astronomy*.

Seeliger’s father was mayor of Biala. After graduating from the Gymnasium at Heidelberg and Leipzig, where he took his doctorate under Bruhns in 1871. From 1871 to 1873 he was assistant at the Leipzig observatory and, from 1873 to 1878, observer at the Bonn observatory. He served as *Privatdozent* at Leipzig until 1881, when he became director of the Gotha observatory. The following year he succeeded Lamont as professor of astronomy and as director of the Munich observatory, retaining both posts until his death.

One of the most famous astronomers of his time, Seeliger was interested mainly in theoretical astronomy. His activities, however, also included observations, and in 1874 he led an expedition to the Pacific to observe the transit of Venus. His papers on stellar statistics were his most important contribution to theoretical astronomy. He was the first astronomer to develop the fundamental equations of the relations between various statistical functions of the stars. The immense number of stars in the Milky Way precludes a determination of its constitution by studying each star separately. Seeliger found that there are integral equations relating the function of stellar density in space with the distribution of stars of apparent magnitude; the first of these functions can be calculated after the distribution has been determined by observation. Although later improved and simplified in certain points, Seeliger’s theory established the fundamental principles of stellar statistics.

Seeliger’s important papers on the illumination of cosmic objects deal especially with Saturn and the zodiacal light. His speculations on the occurrence of novae were later abandoned by astronomers. His research on the law of gravitation provided a strong impetus to astronomical cosmology. He found that the Euclidean structure of space, non-vanishing mean density of matter, and overall validity of Newton’s law of gravitation were incompatible, because a universe constructed on these principles would be unstable. In an attempt to resolve this difficulty, Seeliger assumed that Newton’s law required small corrections. Later cosmological research, partly stimulated by his results, made it clear that no instability occurs if all matter in the universe moves—for instance, if the universe expands, as has been believed since about 1930.

In 1885 Seeliger married Sophie Stoeltzel, daughter of a professor at the Munich Technische Hochschule: they had two sons. Seeliger was president of the Astronomische Gesellschaft from 1896 to 1921 and of the Munich Academy of Sciences from 1918 to 1923. Many students took their doctorates under his supervision, the best known being Karl Schwarzschild. Seeliger’s influence on the development of astronomy was thus much greater than many astronomers believe.

## BIBLIOGRAPHY

**I.** Original Works. Seeliger’s papers on stellar statistics are in the e in the *Abhandlungen* and *Sitzungsberichte der Bayerischen Akademie der Wissenschaften*, Math.-phys. KI. (1884–1920). Some papers also appeared in *Astronomisch Nachrichten*three articles in the latter— **137** (1895), 129–136: and **138** (1895), 51–54, 255–258- deal with Newton’s law of gravitation. See also “Zur Theorie der Beleuchtung der grossen Planeten, insbesondere des Saturn,” in *Abhandlungen der Bayerischen Akademie der Wissenschaften* Math.-phys. Kl., **16** (1887), 403–516; and “Theorie der Beleuchtung stubförmiger Massen, insbegsondere des Saturnringes,” *ibid*., **18** (1893), 1–72.

A complete bibliography of Seeliger’s publications and of all doctoral theses supervised by him is given by H. Kienle, in *Vierteljahrsschrift der Astronomischen Gesellschaft*, **60** (1925), 18–23.

**II.** Secondary Literature. See G. Deutschland, “Die Untersuchungen H. V. Seeliger’s über das Fixsternsystem,” in *Vierteljahrsschrift der Astronomischen Gesellschaft*, **54** (1919), 25–131; and E. von der Pahlen, Lehrbuch der Stellarstatistik (Leipzig, 1937), 370–409.

F. Schmeidler