was a Japanese

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...

noted for his contributions to

celestial mechanics Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, to ...

Life and work

Hagihara graduated from

Tokyo Imperial University , abbreviated as or UTokyo, is a public research university located in Bunkyō, Tokyo, Japan. Established in 1877, the university was the first Imperial University and is currently a Top Type university of the Top Global University Project by ...

with a degree in astronomy in 1921 and became an assistant professor of astronomy there two years later. In 1923 the Japanese government sent him abroad as a traveling scholar. Hagihara went to Cambridge University in England to study differential equations under the mathematician Henry Frederick Baker and relativity alongside

Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...

under the astrophysicist Sir

Arthur Stanley Eddington Sir Arthur Stanley Eddington (28 December 1882 – 22 November 1944) was an English astronomer, physicist, and mathematician. He was also a philosopher of science and a populariser of science. The Eddington limit, the natural limit to the lumi ...

. He was a visiting scholar in France, Germany, and the United States. He returned to Japan in 1925 but left for the United States three years later to study the topology of dynamical systems at Harvard University under

George David Birkhoff George David Birkhoff (March 21, 1884 – November 12, 1944) was an American mathematician best known for what is now called the ergodic theorem. Birkhoff was one of the most important leaders in American mathematics in his generation, and during ...

on a Rockefeller Foundation Fellowship. Hagihara finished his studies at Harvard in 1929 and returned again to the University of Tokyo, where, in 1930, he completed a D.Sc. dissertation on the stability of satellite systems. In 1935, he published a paper showing that the trajectory of a test particle in the Schwarzschild metric can be expressed in terms of elliptic functions. For more than a decade after 1937, he investigated the distribution of electron velocities in planetary nebulae. He was promoted to full professor at the University of Tokyo in 1935. From 1945 to 1957 he was the director of the Tokyo Astronomical Observatory and subsequently was a professor at

Tohoku University , or is a Japanese national university located in Sendai, Miyagi in the Tōhoku Region, Japan. It is informally referred to as . Established in 1907, it was the third Imperial University in Japan and among the first three Designated National ...

(1957–1960) and president of

Utsunomiya University is a national university in Japan. The main campus is located in Miné-machi, and the engineering campus at Yōtō, in Utsunomiya, Tochigi Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Tochigi Prefecture ...

(1961–1967). In 1961 he was elected vice-president of the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

and president of the IAU's commission on celestial mechanics. He retired from all of his official duties, except for the Japan Academy, in 1967 and devoted himself to writing his comprehensive five volume work, ''Celestial Mechanics'', which was based on his lecture notes. Hagihara was regarded as a quiet and cultured gentleman, an excellent teacher and a capable administrator. He has pointed out the importance of the post-Newton models for celestial mechanics, namely that developed by Georgi Manev.

Honors

* The main-belt asteroid 1971 Hagihara was named in his honor. * Fellow of the

Royal Astronomical Society (Whatever shines should be observed) , predecessor = , successor = , formation = , founder = , extinction = , merger = , merged = , type = NG ...

* Chairman of the National Committee of Astronomy (Japan) * Member

Japan Academy The Japan Academy ( Japanese: 日本学士院, ''Nihon Gakushiin'') is an honorary organisation and science academy founded in 1879 to bring together leading Japanese scholars with distinguished records of scientific achievements. The Academy is ...

* Member Science Council of Japan * Order of Cultural Merit (Japan) * Recipient of the

James Craig Watson Medal 400px, James Craig Watson Medal The James Craig Watson Medal was established by the bequest of James Craig Watson, an astronomer the University of Michigan between 1863 and 1879, and is awarded every 1-4 years by the U.S. National Academy of Scien ...

from the U.S. National Academy of Science (1960)

Works

* * * * * *

References

* {{DEFAULTSORT:Hagihara, Yusuke 1897 births 1979 deaths University of Paris alumni Harvard University alumni Academic staff of the University of Tokyo Recipients of the Order of Culture Recipients of the Order of the Sacred Treasure, 1st class 20th-century Japanese astronomers People from Osaka Academic staff of Tohoku University

Life and work

Honors

Works

See also

References