Lau, Hans Emil

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Lau, Hans Emil

(b. Odense, Denmark, 16 April 1879; d. Usseød, Denmark, 16 October 1918),

astronomy.

In 1906 Lau received the master’s degree at the University of Copenhagen. During the following years he worked at the private Urania Observatory at Frederiksberg, a suburb of Copenhagen. About 1911-1912 he spent a year at the Treptow Sternwarte in Berlin, and after his return to Denmark he built a small private observatory.

In 1905 Lau was awarded a gold medal by Copenhagen University for a discussion of the observations of the bright new star of 1901 and of theories on new stars; he also published an interpretation of a nova spectrum. From his youth Lau worked on the problem of a trans-Neptunian planet (or two planets); and his conclusions must be characterized as sound.

During 1905-1911 Lau made a long series of visual measurements of double stars and did some pioneer work on photographic observations; he discussed the systematic errors of visual observations and made a close determination of the orbit of the system of 70 Ophiuchi; in connection with his reobservation of previously measured optical companions of bright stars he published several discussions of the proper motions and parallaxes of faint stars. He made observations of variable stars, of stars suspected of variability, and of colors of stars; he was also one of the first astronomers to become interested in photographic photometry.

Lau was always an eager observer of the planets, especially of Mars and Jupiter, making drawings of their surfaces and micrometrical determinations of the positions of details on them. His comprehensive descriptions of the yearly changes of the features of Mars and of the clouded world of Jupiter, based on observations collected from a great many observers, must be regarded as exhaustive contemporary discussions of these problems.

Lau never succeeded in obtaining a position at a scientific institution, but his contributions are those of an original and dedicated scientist.

BIBLIOGRAPHY

I. Original Works. A listing of Lau’s works in Astronomische Nachrichten is in Poggendorff, V, 711. His writings include “Sur la question des planètes transneptuniennes,” in Bulletin astronomique, 20 (1903), 251-256; “Sur le spectre des étoiles nouvelles,” ibid., 23 (1906), 297-303; “Sur le système de 70 Ophiuchi,” ibid., 25 (1908), 139-141, and 26 (1909), 433-456; “Über die Rotation des Planeten Jupiter,” in Astronomische Nachrichten, 195 (1913), 313-340; “La planète transneptunienne,” in Bulletin de la Société astronomique de France, 28 (1914), 279-283; “Die periodischen Veränderungen auf dem Mars,” in Astronomische Nachrichten, 204 (1917), 81-124; and “Utersuchungen über die Farben der Fixsterne,” ibis., 205 (1918), 49-70. Lau’s measurements of visual double stars are published in a series of papers in Astronomische Nachrichten, 169-205 (1905-1918).