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早在 1930 年代,荷蘭科學家簡奧特(Jan Oort)觀察了鄰近星系中恆星的運行後就曾經提出,星系的總質量必須有能觀察到的物質的 3 倍之多,才能使眾多的恆星能夠繞著星系運行而不離開星系。那麼多的質量是誰提供的?奧特沒有給出答案。  到了70 年代,美國天文學家薇拉魯賓(Vera Rubin)研究了螺旋狀星系仙女座星系的星體運動,發現按照萬有引力推算,仙女座星系的星體似乎轉得太快了,除非存在著龐大的、不可見的物質暈環圍繞著星系,而這些不可見物質的總質量高達星系總質量的 90% 以上。

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