Kimura, Hisashi

(b, Kanazawa, Japan, 9 September 1870; d. Setagaya-ku, Tokyo, Japan, 26 September 1943)

astronomy.

Hisashi Kimura graduated from the department of astronomy, College of Science, Tokyo University, in 1892. During the following six years, while attending graduate school at the same university, he began to study latitude variation through observation. In 1899 he became director of the Mizusawa Latitude Observatory and devoted the rest of his life to the observation of latitude variation.

The question of latitude variation was of considerable interest to astronomers at the end of the nineteenth century because of Euler’s work. In 1765 Euler’s theory had predicted that a difference of motion between the principal axis and the rotational axis of the earth’s moment of inertia would cause the latter to rotate around the former in a cycle of 305 days. This fact was substantiated 120 years later by Seth Chandler and Friedrich Küstner.

Kimura discovered that in latitude variation there is an annual term independent of the motion of the earth’s axis which can be observed regardless of the observer’s position (“A New Annual Term in the Variation of Latitude, Independent of the Components of the Pole’s Motion,” in Astronomical Journal, 22 [1902]. 197). The observation of the value became an important problem in international observation. Even today the cause for this annual term is not clear but it is presumed that it is a geophysical phenomenon rather than an astronomical one.

Kimura became the chairman of the Latitude Variation Committee of the International Astronomical Union in 1918, and when the Mizusawa Observatory was established as the Central Bureau of International Latitude Observation in 1922, Kimura was elected director; he held both positions until his resignation in 1936.

BIBLIOGRAPHY

His works are published in Results of International Latitude Service, 7 (Mizusawa, 1935 and 8 (Mizusawa, 1940). His research achievements are published in Astronomical Journal, 36 (1943), 117-119, and in “An Interim Report on an International Research Project: the Wandering of the North Pole,” in Harlow Shapley, ed., Source Book in Astronomy, 1900-1950 (Cambridge, Mass., 1960), pp. 64-66.

S. Nakayama