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Dr. Yoshihide Kozai Former Director General of NAOJ Passes Away

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Dr. Yoshihide Kozai

Dr. Yoshihide Kozai, Professor Emeritus of the National Astronomical Observatory of Japan (NAOJ) and also the founding Director General of NAOJ for 6 years starting from 1988, passed away due to liver failure at 6:15 p.m. on Monday, February 5, 2018, at age 89.

Dr. Yoshihide Kozai was a global leader in the field of astronomy. He lent his strength to Tokyo Astronomical Observatory (TAO), NAOJ, and the development of astronomy in Japan and around the world. Dr. Kozai was first appointed to the University of Tokyo’s Tokyo Astronomical Observatory in 1952. He also served as a Visiting Researcher at institutes like the Smithsonian Astrophysical Observatory in the U.S.A. before being appointed Director General of TAO in 1981. While modernizing TAO, he led its reorganization into the Inter-University Research Institute, National Astronomical Observatory of Japan in 1988 and served as the founding director of NAOJ until 1992. During this time he conducted a wide variety of international activities, such as starting the 8.2 meter aperture Subaru Telescope project as Japan's first large overseas research facility, and serving as the first ever Japanese President of the International Astronomical Union (IAU) from 1988 to 1991.

He is known worldwide in the research field of celestial mechanics for his work on the motion of artificial satellites. He had many important achievements, such as proposing “Kozai’s equation” which is still used for satellite orbit calculations and based on that he discovered the North-South asymmetry of the Earth (the so called “Pear Shape”). He also proposed the kinematic mechanism by which asteroids in inclined or elliptical orbits experience large changes in their orbits due to the gravity of the planets (known as the “Kozai mechanism,” this principle is now widely used for exoplanet systems). For these achievements, he received the Imperial Prize and the Japan Academy Prize in 1979, American Astronomical Society Brouwer Award in 1990, Second Class Order of the Sacred Treasure in 2002, and Person of Cultural Merit in 2009. On the other hand, in the Science Council of Japan, he helped address the deficiency of Japanese female researchers and other problems. After retiring from NAOJ, he continued to make many great contributions to society as Director of Gunma Astronomical Observatory, such as supporting young researchers from Japan and Asian nations. We will not forget his many friendly interactions with amateur astronomers, including writing books for the public and serving on the editorial committee for astronomy magazines.

We respectfully mourn his passing.

Comment from Dr. Masahiko Hayashi, Director General of the National Astronomical Observatory of Japan.

Dr. Yoshihide Kozai made great accomplishments in the study of celestial mechanics. On the other hand, he established the cornerstone for the development of the National Astronomical Observatory of Japan as an Inter-University Research Institute. Japanese astronomy has experienced a huge growth thanks to his work. In particular, as the last Director General of Tokyo Astronomical Observatory, he led the establishment of NAOJ in 1988. He also decided to set up a large telescope outside Japan (later named the Subaru Telescope) and oversaw the start of the project as the founding Director General of NAOJ. This was the first time for Japan to build a telescope overseas. At the same time, he led gravitational wave detector experiments. In the 1990’s, TAMA300 in Mitaka Campus proved the potential of laser interferometers as gravitational wave detectors. We respectfully mourn Dr. Kozai who made great contributions to the development of Japanese astronomy and pray that his soul may rest in peace.

February 13, 2018

Brief Personal History
1952 Assistant at Tokyo Astronomical Observatory, the University of Tokyo
1958 PhD at the University of Tokyo
1958 Visiting Researcher at the Smithsonian Astrophysical Observatory and Harvard College Observatory (Until 1963)
1963 Associate Professor at Tokyo Astronomical Observatory, the University of Tokyo
1963 The Asahi Prize (The Asahi Shimbun Company)
1965 Head of the Computing Center for Artificial Satellites, Tokyo Astronomical Observatory
1966 Professor at Tokyo Astronomical Observatory, the University of Tokyo
1973 Director of Dodaira Observatory, Tokyo Astronomical Observatory
1979 Imperial Prize and Japan Academy Prize for “Research on Movements of Saturnian Satellites, Artificial Satellites, and Asteroids”
1980 Member of the Japan Academy
1981 Director General of Tokyo Astronomical Observatory (Until 1988)
1983 Administrative Director of the Astronomical Society of Japan (Until 1985)
1988 Founding Director General of the National Astronomical Observatory of Japan (Until 1994)
1988 President of the International Astronomical Union (IAU) (Until 1991, the first Japanese president)
1990 Brouwer Award (American Astronomical Society)
1997 Director of Gunma Astronomical Observatory (Until 2012)
2002 Second Class Order of the Sacred Treasure
2009 Person of Cultural Merit
2010 Honorary Citizen of Mitaka City
2018 Deceased

February 22, 2018: updated.