Masaru Arai

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is a Japanese amateur astronomer and a discoverer of minor planets and comets.

He is credited by the Minor Planet Center with the discovery of 45 minor planets during 1988–1991, all in collaboration with astronomer Hiroshi Mori. On 5 January 1991, he has also discovered Comet Arai, .

The main-belt asteroid 21082 Araimasaru, discovered by Tsutomu Hioki and Shuji Hayakawa at Okutama in 1991, was named in his honor. Naming citation was published on 6 January 2003 (). Provided by Wikipedia