Kiyotsugu Hirayama

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Kiyotsugu Hirayama (平山 清次, Hirayama Kiyotsugu, October 13, 1874 – April 8, 1943) was a Japanese astronomer, best known for his discovery that many asteroid orbits were more similar to one another than chance would allow, leading to the concept of asteroid families, now called "Hirayama families" in his honour.

The crater Hirayama on the Moon is jointly named after him and Shin Hirayama. The asteroid 1999 Hirayama is named in his honour.[1]


  1. ^ "(1999) Hirayama". (1999) Hirayama In: Dictionary of Minor Planet Names. Springer. 2003. p. 162. doi:10.1007/978-3-540-29925-7_2000. ISBN 978-3-540-29925-7.