跟我一起看美丽的星云吧

Credit & Copyright: Robert Gendler
拍摄者、版权：（著名天文摄影大师）Robert Gendler
Explanation:
How far can you see? The most distant object easily visible to the unaided eye is M31, the great Andromeda Galaxy some two million light-years away. Without a telescope, even this immense spiral galaxy appears as an unremarkable, faint, nebulous cloud in the constellation Andromeda.
我们能看到多远？肉眼可见的最遥远天体是M31——离我们约200万光年的巨大的仙女座大星系。如果我们不借助望远镜，这个庞大的涡旋星系不过是仙女座内不起眼的昏暗云团而已。
But a bright yellow nucleus, dark winding dustlanes, gorgeous blue spiral arms and star clusters are recorded in this stunning telescopic digital mosaic of the nearby island universe. While even casual skygazers are now inspired by the knowledge that there are many distant galaxies like M31, astronomers seriously debated this fundamental concept only 80 years ago. Were these "spiral nebulae" simply outlying components of our own Milky Way Galaxy or were they instead "island universes" -- distant systems of stars comparable to the Milky Way itself? This question was central to the famous Shapley-Curtis debate of 1920, which was later resolved by observations of M31 in favor of Andromeda, island universe.
但在这张近邻宇宙岛漂亮的数码拼接图像中，可以清晰看到明亮的黄色核心、蜿蜒的黑色尘埃带、灿烂的蓝色旋臂和星团。虽然现在观星新手也知道，宇宙中有无数与M31类似的遥远星系；但是80年前，这样的基本概念在天文学界却争议极大：这些“螺旋型星云”到底是我们银河系外围的偏僻天体，还是它们与银河系一样，是遥远的“宇宙岛”？1920年，就此问题进行了著名的Shapley-Curtis辩论。后来一系列的观测表明，M31是遥远的“宇宙岛”。