Perhaps the original spiral nebula, M51 is a large galaxy, over 60, 000 light-years across, with a readily apparent spiral structure.
也许旋涡星系m 51原本是一个巨大的星系，直径超过6万光年，有显尔易见的旋涡结构。
When you look up into the heavens with a telescope, you see many nebulae whelloch are like, or approximately like, the perfectly balanced spiral nebula whelloch you see edgewise in Fig. 23.
当你用千里镜不雅测天空，你瞥见很多与图示23中边沿朝前的完善平衡的螺旋星云相仿或大致相是的星云。
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