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| dist_pc=2,300〔 }} WR 104 is a binary star system located about 7,500 light years from Earth. The primary is a Wolf-Rayet star and the secondary is a main sequence OB star. WR 104 is surrounded by a distinctive dusty pinwheel nebula over 200 astronomical units long formed by interaction between the stellar winds of the two stars as they rotate and orbit. The spiral is composed of dust that would normally be prevented from forming by WR 104's intense radiation were it not for the star's companion. The region where the stellar wind from the two massive stars interacts compresses the material enough for the dust to form, and the rotation of the system causes the spiral-shaped pattern. The round appearance of the spiral leads to the conclusion that the system is seen almost pole on, and an almost circular orbital period of 220 days had been assumed from the pinwheel outflow pattern. WR 104 shows frequent eclipse events as well as other irregular variations in brightness. The undisturbed apparent magnitude is around 12.7, but the star is rarely at that level. The eclipses are believed to be by dust formed from expelled material, not by the companion star.〔 A third star, about 2 magnitudes fainter than the spectroscopic pair at visual wavelengths, has been resolved almost 1" distant. ==References== 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「WR 104」の詳細全文を読む スポンサード リンク
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