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61 Cygni 〔Not to be confused with 16 Cygni, a more distant system containing two G-type stars harboring the gas giant planet 16 Cygni Bb.〕 is a binary star system in the constellation Cygnus, consisting of a pair of K-type dwarf stars that orbit each other in a period of about 659 years. Of apparent magnitude 5.20 and 6.05 respectively, they can be seen with binoculars in city skies or with the naked eye in rural areas without light pollution. 61 Cygni first attracted the attention of astronomers when its large proper motion was first demonstrated by Giuseppe Piazzi in 1804. In 1838, Friedrich Wilhelm Bessel measured its distance from Earth at about 10.3 light years, very close to the actual value of about 11.4 light years; this was the first distance estimate for any star other than the Sun, and first star to have its stellar parallax measured. Among all stars or stellar systems listed in the modern Hipparcos Catalogue, 61 Cygni currently has the seventh highest proper motion, and the highest among all visible stars or systems.〔 Over the course of the twentieth century, several different astronomers reported evidence of a massive planet orbiting one of the two stars, but recent high-precision radial velocity observations have shown that all such claims were unfounded. No habitable planets have been confirmed in this stellar system to date. == Name == 61 Cygni is relatively dim, so it does not appear on ancient star maps, nor is it given a name in western or Chinese systems. The name "61 Cygni" is part of the Flamsteed designation assigned to stars. According to this designation scheme, devised by John Flamsteed to catalog his observations, stars of a particular constellation are numbered in the order of their right ascension, not in Greek letters as the Bayer designation does.〔(【引用サイトリンク】 title=Naming Objects Outside the Solar System-Stars )〕 The star does not appear under that name in Flamsteed's ''Historia Coelestis Britannica'', although it has been stated by him that 61 Cygni actually corresponds to what he referred to as 85 Cygni in the 1712 edition. It has also been called "Bessel's Star" or "Piazzi's Flying Star".〔(【引用サイトリンク】 title= 61 Cyg (Piazzi's Flying Star) )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「61 Cygni」の詳細全文を読む スポンサード リンク
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