Double star - Nijyuusei (English spelling) double star

Japanese: 二重星 - にじゅうせい（英語表記）double star

A double star is two stars that appear very close to each other. Usually, they appear as one to the naked eye, but when viewed through a telescope, they appear as two. A binary star is when the two stars are actually close together and revolve around each other due to gravity. The brighter star is called the primary star, and the fainter star is called the companion star. When the two stars can be observed separately with a telescope, they are called visual binary stars. When the two stars cannot be separated but can be seen from periodic changes in their spectral lines, they are called spectroscopic binary stars. When one star is obscured by the orbital motion and changes in luminosity can be seen, they are called eclipsing binary stars (or eclipsing variable stars). By observing binary stars, the masses of the stars can be determined. It is thought that a considerable number of stars form binaries.

(Makoto Tosa, Professor at Tohoku University / 2007)

Source : "Chiezo" published by Asahi Shimbun Publications Co., Ltd. About Chiezo

Japanese:

非常に近接して見える2個の恒星が二重星。通常、肉眼では1個にしか見えないが、望遠鏡では2つに見えるものを指す。連星は2つの星の距離が実際に近く、万有引力により公転運動しているもの。明るい方を主星、暗い方を伴星という。望遠鏡で2星が分離して観測できる場合を実視連星、2星は分離できないが、スペクトル線の周期的変化から分かる場合を分光連星、公転運動によって星が隠され、光度変化が認められるものを食連星(または食変光星)という。連星の観測により、星の質量が決定できる。かなりの星が連星をなすと考えられている。

(土佐誠東北大学教授／ 2007年)

出典　(株)朝日新聞出版発行「知恵蔵」知恵蔵について　情報

<<: Twenty-two shrines

>>: Double Truth